This PDF file contains the front matter associated with SPIE Proceedings Volume 8550, including the Title Page, Copyright Information, Table of Contents, and the Conference Committee listing.

Designing optical subsystems not only requires consideration of the optical properties of the optical components but also examination of the properties of the mechanical subsystem structures such as e.g., alignment or mounting structures. This is essential since most optical subsystems extend over three dimensions and are realized in modular setups, where the optical components are mounted and adjusted by means of mechanical structures. Hence, the contour accuracy of these structures is crucial for the adjusted alignment of the optical components and therefore for the system’s performance. The contour accuracy depends on both the fabrication processes and the operational conditions of the optical subsystem. This leads to our concept of comprehensive modeling and simulation where not only optical properties are to be simulated but as well the influences of the mechanical system structures on the optical performance.

The geometric point spread function (PSF) is an appropriate tool for modeling image degradation of an optical system, whenever the effect of diffraction is small compared to that of aberrations. The PSF is conventionally estimated by computing the density of ray intersections with the image plane (ray-counting method). We studied the effect of two factors on the estimation: the number of rays, using an error model, and the influence of the ray sampling pattern. We measured the accuracy of the PSFs estimation in three ideal cases, where we could derive an analytical expression for the irradiance. Additionally we estimated the PSFs generated by a single rear landscape lens. We have observed a consistent improvement of 4.5 dB (Signal-to-Noise Ratio) when doubling the number of rays. This ensures that an arbitrarily high accuracy on the estimation of geometric PSFs is theoretically attainable. However, the method is not very effcient because of the slow convergence rate. As an alternative, to avoid tracing a large number of rays, we investigated the benefits of interpolating rays intersections (using cubic splines) of the ray mapping. For instance, by interpolating only 100 traced rays we may obtain a similar quality in the estimation as when using 100 million of real traced rays. Among different uniform ray pupil sampling patterns (square, jittered square, hexapolar and hexagonal) we found that the hexagonal outperformed the other ones.

The previous publications (Miñano et al, 2011) have shown that using a Spherical Geodesic Waveguide (SGW), it can be achieved the super-resolution up to λ /500 close to a set of discrete frequencies. These frequencies are directly connected with the well-known Schumann resonance frequencies of spherical symmetric systems. However, the Spherical Geodesic Waveguide (SGW) has been presented as an ideal system, in which the technological obstacles or manufacturing feasibility and their influence on final results were not taken into account. In order to prove the concept of superresolution experimentally, the Spherical Geodesic Waveguide is modified according to the manufacturing requirements and technological limitations. Each manufacturing process imposes some imperfections which can affect the experimental results. Here, we analyze the influence of the manufacturing limitations on the super-resolution properties of the SGW. Beside the theoretical work, herein, there has been presented the experimental results, as well.

By integrating optical and photometrical simulation directly into CAD/CAM software, OPTIS presents an innovative solution which answers the global design needs on complex shapes, making optical, thermal, mechanical and cinematic functionalities communicate with each other. The OptisWorks solution, integrated in SolidWorks from Dassault Systèmes, opens up access to a multitude of applications to optical engineers, from analysis of optical performance, stray light analysis, and at the same time putting into a virtual context the final opto-mechanical system under constraint, which now becomes an integral part of the final assembly. The Optical Design solution inside OptisWorks enables the creation of optical components dedicated to imaging (lenses, mirrors, diaphragms) and their insertion directly in the CAD environment. After having added an optical source and a detection surface plane, the user can analyze the optical performances of his/her imaging system: spot size, wave front default, MTF, etc. The results of these analyses are comparable to what dedicated optical design software can offer. The user can then launch an optimization or a tolerancing of their opto-mechanical system. CAD integration also offers other physical simulation tools available with SolidWorks: thermal, tolerancing, cinematic, interference detection, etc. For example it is possible, using the thermal simulation model, to take into account dilation of opto-mechanical elements right from the optical design phase, and to determine their influence on optical performances. This innovation naturally leads onto a change in the methodologies of designing optical imaging systems which are now open to the CAD world. By integrating optics right at the start of the design process, enables designers to arrive quicker at a solution which will fully meet all the criteria and specifications requested, and no longer in isolation to each specification.

Recent developments in design algorithm allow the calculation of free form surfaces that generate a picture in the target plane with the help of one optical surface. In contrast to conventional imaging, light modulation is done by a ray-optical redistribution of the incident light which is comparable to incoherent beam shaping. Such picture-generating surfaces normally exhibit very complex surface sags, that are manufactured using diamond turning machining. The knowledge of manufacturing tolerances is important to generate the desired intensity distribution with the required accuracy and at the same time reduce manufacturing effort. However, compared to the tolerancing of conventional optical elements (e.g. spheres), the tolerancing of picture-generating free form optical elements is a demanding task. The complexity of their surface shapes and the target intensity distribution are challenging considering the finding of tolerance parameters and performance criteria. Tolerance parameters strongly depend on the manufacturing process. Therefore they can be obtained by a detailed analysis of their manufacturing process. In this contribution we focused on picture-generating free form optical elements manufactured using diamond turning with slow tool servo support. Astigmatism and spherical aberration are typical manufacturing errors caused by this tool exhibiting low spatial frequency. Errors with middle to high spatial frequency have not been investigated so far. Conventional software tools for tolerancing, as e.g. implemented in Zemax, provide only such tolerance parameters as radius, thickness or tilt, corresponding to conventional manufacturing methods of classical optical elements (e.g. spheres). Therefore we implemented a software tool developed in Matlab and using Zemax for raytracing in order to perform sensitivity analysis and Monte Carlo analysis. Conventional performance criteria like spot radius or wavefront error to evaluate the tolerance analysis cannot be applied for picture-generating free from elements. Consequently, other performance criteria were investigated. The correlation between the desired and the generated intensity distribution was chosen to be an appropriate performance criterion for the tolerancing analysis.

In the framework of instrument calibration, straylight issues are a critical aspect that can deteriorate the optical performances of instrument. To cope with this, a new facility is designed dedicated for in-field and far field straylight characterization: up to 10^-8 for in-field and up to 10^-10 for far field straylight in the visible to NIR spectral ranges. Moreover, from previous straylight test performed at CSL, vacuum conditions are needed for reaching the 10^-10 rejection requirement mainly to avoid air/dust diffusion. The major constrains are to design a straylight facility either for in-field and out-field straylight measurements. That requires high dynamic range at source level and a high radiance point source allowing small diverging collimated beam. Moreover, the straylight facility has to be implemented into a limited envelope and has to be built with vacuum compatible materials and black coating. As checking the facility performance requires an instrument better than the facility itself, that is no easy to find, so that the performances have been estimated through a modelisation into a non sequential optical software. This modelisation is based on CAD importation of mechanical design, on BRDF characteristics of black coating and on statistical averaging of ray tracing at instrument entrance.

A simulation model for the development of an aspheric lens adjustment system that is based on multi-point optical distance measurement is presented. Adjustment of aspheric lenses means the correction of decentering and tilt errors within the mount of the lens. The presented model includes the determination of decentering and tilt errors using distance measurement variation of the lens surface at certain radial positions over 360° rotation of the lens. However, the occurring noise in the distance measurement as well as an uncertainty in the distance sensor positioning lead to errors remaining after the determination of decentering and tilt by the new method. The size of these residual errors can be estimated by the presented simulation tool with statistical significance. The simulation model provides the possibility to use arbitrary noise values as input quantity. The individual aspheric lens design data, the number of chosen measurement positions, and the specified noise level determine the statistically expected residual error after lens adjustment. It provides the possibility to determine the optimal arrangement of the positions of the distance sensor and the number of repetitions for every given aspheric lens for the enforcement of the requested measurement accuracy. The newly developed simulation model is a necessary tool for a novel metrology method of the adjustment of aspheric lenses.

The forward tracing technique for diffraction analysis (FFTD) is a numerical technique for ray-tracing environments inspired by the Boundary Diffraction Wave. The technique was developed specifically considering circular apertures in imaging systems. In previous work the technique was applied to a simple optical system. The value of the method has been geared towards aiding optical design where diffraction effects not produces at the aperture stop are important. In this work the technique is applied and evaluated as a tool for analyzing a complex system where only circular apertures are present. The chosen system is an IR endoscope on the MWIR region. The system requirements make for circular apertures aside from the stop where diffraction becomes important. FFTD is applied for obtaining irradiance information at the image plane. The key parameters affecting the simulation are described on axis and field.

Synopsys OSG ( formerly Optical Research Associates ) have recently developed a CODE V® feature called 'Glass Expert'. Taking advantage of modern computing power, this program extends the normal optimisation methods by allowing a large number of glass types to be substituted into a lens system in an automatic way . We evaluated this software, applying it to a small number of suitable lens systems . We wanted to discover how quickly it runs, how the user input choice affects the end-result , and at what point of the design process it is most valuable . The exercise proved to be very interesting. We describe how, in one case of a highly colour-corrected visible system, the macro was able to reproduce, within a couple of hours , most of the glass choices I discovered over a period of a couple of weeks in the original design process. While this macro is obviously useful for specially-corrected visible systems, it is also potentially useful for mid-wave IR and the important short-wave IR ( SWIR ) band. An example of re-optimisation of a NIR/SWIR –band lens is given . ‘Glass Expert’ also offers the interesting possibility of swapping air and glass materials in an automatic way. We tried this option on one example, but ran into some problems that require further thinking . Some other pitfalls, and potential future improvements in the software are mentioned. We also describe how ‘Glass Expert’ and Global Synthesis® can work very effectively in combination .

Photonic Crystal Fibres (PCFs) are well known for allowing the implementation of specific waveguiding features that cannot be achieved with conventional optical fibres. This results from the design flexibility of the holey structure in the PCF cladding and/or core regions. Today PCFs have found applications for example in supercontinuum generation, optical sensing and fibre lasers. They are now also being combined with fibre Bragg gratings, more specifically in the fields of optical fibre sensing and all-fibre laser applications. In this contribution we discuss how we applied micro-optical design methods based on commercially available software such as MODE Solutions and FDTD Solutions from Lumerical Solutions, Inc. and COMSOL Multiphysics® combined with MATLAB® scripting and additional optimization methods to develop microstructured fibres for three different purposes, i.e. PCF structures that facilitate Bragg grating inscription, PCF structures that enable temperature insensitive pressure measurements and bendable PCFs with a very large mode area for high power short pulse fibre lasers. For the three cases we describe the fibre design methods and property simulations as well as the tolerance studies that take into account manufacturing imperfections as well as possible variations in material parameters.

Opto-mechanical structures (objectives) are employed to transfer photons which are collected from their field of view (FOV) to the detector plane. The sensors used in such systems have high gain which causes them to detect stray light originated from the mechanical body of the objective. This type of stray light is a major problem in low light nonimaging optical systems used in laser seekers which employ four quadrant position sensors to determine laser illumination reflected from a target surface positioned kilometers away. This work, mainly concentrates on reducing unwanted stray light caused by inner mechanical structure of large FOV objectives with the use of software tools. Stray light in an optical system can not be totally eliminated. However, it can often be reduced to a level at which it is tolerable. This works focuses on reducing unwanted stray light originating from mechanical structure of the objective in a cost efficient way. In order to prevent this unwanted stray light a sample laser seeker objective is designed in ZEMAX software environment together with its mechanical mount. Black delrin is used as the objective material. Its specular and diffused reflective properties are measured with spectrophotometer and defined in the software environment. Ten objectives with different baffle height/pitch ratio (h/p) are designed and used in the same optic design. In order to show that a software model can be used to find the optimum h/p ratio for eliminating stray light, prototype objectives are manufactured and tested with readout electronics. After making measurements with different angles on incidence values best applicable objective with a certain baffle h/p ratio is found. It is verified that the h/p ratio found in software model is in very good agreement with the measurement results. This helps us not use more baffles than necessary since increasing baffle h/p astronomically increases production and workmanship costs. This study shows that, instead of manufacturing expensive prototypes computer simulation can be used to identify and also take necessary precautions to prevent or decrease stray light before production. This prevents loss of significant amount of time, work, and cost.

Dispersion causes the focal lengths of refractive and diffractive optical elements to vary with wavelength. In our contribution we show how it can be used for chromatic encoding and decoding of optical signals. We specifically discuss how these concepts can be applied for the implementation of systems with applications in the growing fields of hyperspectral imaging and chromatic distance coding. Refractive systems as well as hybrid combinations of diffractive and refractive elements are used to create specific chromatic aberrations of the sensors. Our design approach enables the tailoring of the sensor properties to the measurement problem and assists designers in finding optimized solutions for industrial applications. The focus of our research is on parallelized imaging systems that cover extended objects. In comparison to point sensors, such systems promise reduced image acquisition times and an increased overall performance. Concepts for three-dimensional profilometry with chromatic confocal sensor systems as well as spectrally resolved imaging of object scenes are discussed.

^{Passive athermalization has become a key-technology for automotive and other outdoor applications using modern uncooled 25 and 17 micron bolometer arrays. For high volume applications, passively athermalized optical designs with a minimum of lenses reduce costs and require a careful choice of lens and housing materials. But, up to now, metrics of athermal properties of these lenses are seldom published. Metrics for athermalization are mentioned in two categories: MTF-based to describe application limits under environmental conditions, and first order relations which are helpful in the optical and mechanical design process. Correlation between both categories is analyzed on several GASIR®-lens designs. The allowable degradation of MTF in the Temperature Range depends on the lens application. The MTF-approach proposed to quantify passive athermalization considers different metrics: Several Through-Focus-MTF-graphs at interesting temperatures for optical design, the MTF-versus-field-graph at interesting temperatures offers the complete customer information; the On-Axis-MTF versus temperature shows the typical thermal drift. The most effective way to describe the athermalization status is the value pair of Temperature Range and of percentage in MTF-loss for on-axis point. This pair of values is applicable for all IR-imaging lenses, closely related to lens application, and independent of the camera detector. First order relations identify the most critical influences on athermalization. Different lens materials are discussed whereby the achromatic correction by diffractive structures reduces also the effective Thermal Glass Constant. GASIR® possesses inherent passive athermalization properties. Known first order relations are expanded to two group lens systems. This new relation gives a good overview on where the most effective place for the PMA-mechanism in the lens assembly is and how to arrange it. A narrow field of view example shows different kinds of movement: first group only, second group only and both groups together. It will be seen that the shortest compensation mechanism depends on power and distance of groups.}

Real-time imaging techniques are required in diverse fields, such as food factory production lines for food quality monitoring, and in the medical profession for clinical diagnosis. For these purposes, magnetic resonance imaging and X-ray computed tomography have been developed; however, these techniques are difficult to use and expensive, and cannot detect organic, wooden, or plastic foreign objects in food. Optical measurement methods, in contrast, are simple and cheap, and are suitable for real-time monitoring. Optical coherence tomography and photo-acoustic tomography techniques have been developed, but are not classified as real-time imaging techniques as a certain time interval is necessary for computation and imaging. For real-time light-based imaging, we previously developed a compact system using near infrared light, which could detect insects and human hair in food and the blood vessels in the human body. In this study, we describe an improved system in which organic foreign objects or substances in food and bones in chicken wings can be imaged in real time using diffused light. The system consists of an optical source, composed of superluminescent diodes emitting 830-nm light, a certain optical system eliminating scattering light, and a CMOS sensor covering a wide dynamic range. Foreign substances, such as human hairs and insects, are clearly detected in images of 5 mm-thick chocolate. The bone structures in 20 mm-thick chicken wings are also imaged in real-time.

Today’s high brilliance Laser sources cause huge thermal effects on optical components, affecting process stability. This paper shows the holistic approach to the improvement of objective lenses to minimum thermal effects as focus shift. A new approach to the transient simulation of thermal behavior, starting with FEM Analysis, analytical description of surface deformation and refraction index distribution resulting in transient plot of image quality changes by optics design simulation. Optics material selection and characterization of bulk material, surface and coating by newly developed measurement techniques is shown. The optimum setting of opto-mechanical design, material selection, surface finish and coating allows to produce lenses with focus shift by 0,05times the Rayleigh range @1064nm, 4kW multimode at reasonable price.

Optical simulation software based on the ray tracing method offers easy and fast results in imaging optics. This method can also be applied in other fields of light propagation. In fiber optics BPM software is usually used to research the guidance of light in the inner fiber. This is suitable for fibers with small core diameters such as single mode or multi mode glass fibers. For short distance communications polymer optical fibers (POFs) are gradually gaining in importance. This kind of fiber offers a larger core diameter, e.g. the step index POF features a core diameter of 980 μm. Consequently, POFs have a large number of modes (<3 million modes) and BPM is not suitable anymore. Instead, ray tracing could be used. This simulation method is not only applicable for the fiber itself but also for the key components of a complete POF network, e.g. couplers or other key-elements of the transmission line. In this paper a demultiplexer designed and developed by means of ray tracing is presented. Compared to the classical optical design, requirements for optimal design differ particularly with regard to minimize the insertion loss. In other words, the complete light has to be transmitted to guarantee a good transmission. The basis of the presented key element is a wavelength division multiplex device using a Rowland spectrometer set-up. In this approach the input fiber carries multiple wavelengths, which will be divided into multiple output fibers that transmit only one wavelength. To adapt the basic set-up to POF, the guidance of light in this element has to be changed fundamentally. Here, a monolithic approach is presented with a blazed grating using an aspheric mirror to minimize most of the aberrations. In the simulations the POF is represented by an area light source, while the grating is analyzed for different orders and the highest possible efficiency. In general, the element should be designed in a way that it can be produced with a mass production technology like injection molding and hot embossing in order to offer a reasonable price less than 10 EUR. The paper will give an introduction to POF, its application arrays, and will step by step describe the development of the demultiplexer by means of ray tracing simulations.

Here we present a new light sheet generator unit for Ultramicroscopy (UM) employing a combination of optical lenses with aspherical surface structure. UM allows 3D-vizualization of chemically transparent biological specimens with μm-resolution. Improving optical characteristics parameters of light sheet such as the uniformity factor of spatial intensity distribution along the line of focus, the thickness of light sheet, and chromatic aberrations are the most important criteria in this design. Since we do not use any hard edge aperture there is no truncation of the beam and laser energy is used more efficiently. Due to these improvements, a marked enhancement in presenting fine details of biological specimens such as Drosophila melanogaster, entire mouse brain, and hippocampus are achieved.

Background The mechanical properties of small minimally invasive instruments are limited and thus must be treated as flexible instruments. Proper functional behavior of these instruments can be significantly enhanced when the instrument is equipped with a shape sensor to track the path of the flexible instrument. MRI compatible instruments, and thus the corresponding paths, are long in particular. Therefore, the accuracy of the tip position is stringent. Approach We have developed and realized a thin Fiber Bragg Grating (FBG) based fiber optical shape sensor. The main advantages of this fiber optical sensor are its minimum dimensions, the intrinsic MRI compatibility, and the ability of sensing deformation with submicro-strain accuracy. The shape sensor consists of three fibers, each equipped with multiple FBG’s, which are integrated physically by gluing and can be positioned inside an flexible instrument. In this study a critical component analysis and numerical error analysis were performed. To improve performance, a calibration procedure was developed for the shape sensor. Results and Conclusion With current state of the art interrogators it is possible to measure a local deformation with a triplet of FBG sensor very accurately. At high radii of curvature, the accuracy is dominated by the interrogator, whereas at low radii of curvature, the position of the fibers is leading. The results show that position error of a single segment of the shape sensor (outer diameter of 220 μm, a segment length of 23.5 mm and a minimum bending radius of 30 mm) could be measured with accuracies (3σ) of 100 μm for low radius of curvature upto 8 μm for high radii of curvature.

Study of aberrational performance and manufacturing tolerances of Klevtsov family of optical telescopes is presented, with focus on determination of practical boundaries in design space of two-glass solution, which provides correction of spherochromatic aberration comparable with complex full-aperture catadioptric designs at expense of using dense and ultra-dense crowns for sub-aperture meniscus elements with careful mating of Mangin mirror glass. This allows radical improvement of spherochromatic correction in comparison to basic Klevtsov design with corrector lenses of same glass, with increase of both primary mirror’s and whole system’s speed. This family of designs is subject of late Klevtsov’s patents from middle of 90’s and allows building of very compact systems with moderate overall focal ratio, like presented analyzed examples with 0.5 m aperture with f/1.5 primary mirror and f/5 equivalent focal ration, with diffraction-limited on-axis performance within whole visible range Comparison of practical Klevtsov designs with pure reflective designs such as Cassegrain, Ritchey- Chretien, Dall-Kirkham and full-aperture catadioptric designs such as Schmidt-Cassegrain, Maksutov-Cassegrain and Volosov-Houghton designs is taken for field and axial aberrations correspondingly. A number of field correctors for Klevtsov telescope is presented, with near-neutral and focal-converting designs. Overall combination of investigated basic variants and correctors forms perspective multi-focal all-spherical optical telescope, highly suitable for large-volume production, combining low cost, short optical tubes, moderate secondary mirror obscuration and decent field for both high-quality visual observations and CCD imaging.

The object of this paper is to present the experimental validation of aberration compensation into a novel design for seethrough head-mounted displays. The proximity of the user's head generates high geometrical constraints. To compensate for the resulting aberrations, we use both dynamic sequential image creation and dynamic adapted aberration compensation. The see-through head-mounted display is composed of a holographic mirror serving as a combiner and a phase modulation spatial light modulator which insures the dynamic phase correction. The first step of the work has consisted in the realization of the holographic combiner and the characterization of the phase modulation by the light modulator. An experimental analysis of the aberrations of the image beam has been conducted. Next, the implementation of the theoretical corrective phase function into the spatial light modulator has been realized. Finally, the experimental demonstration of the expected aberration compensation has been achieved.

Every digital camera has an IR cut filter to adapt the spectral sensivity of the sensor to that of the human eye. The trend to backside illuminated CMOS chips enable higher “light gathering”, especially under higher angles of incidence (field of view). Due to the virtually angle-independent transmittance characteristics of absorptive filter glasses (e.g. IR blocking so-called “blue glass”), blue glass is more and more used. Pure interference filters have a high angle dependency and in addition reflect the IR light which can cause ghost images. A typical design of a smart phone camera will be used to design and analyze the quality of a blue glass absorption filter. Blue glass as plano-plano filter plate in front of a CMOS chip will be examined. Furthermore, a lens made out of blue glass (substituting the plano-plano filter) will be designed and analyzed. It turns out that the blue glass lens can be used as a crown glass in an achromatic lens. The required transmittance (filter) curve will be elaborated. Such a blue glass lens can shrink down the size of the digital camera significantly. The blue glass lens needs to have a certain inner glass quality, e.g. striae, and thus the effects of wavefront distortion due to inner glass quality will be investigated. As a result striae of blue glass used lens or as plano-plano filter plate needs to be at a certain level. The blue glass lens has tighter restrictions on striae. For both cases a recommendation of inner glass quality level in terms of wavefront distortion will be given.

Ultraprecise aspherical mirrors that offer nanofocusing and high coherence are indispensable for developing third-generation synchrotron radiation and X-ray free electron laser sources. In industry, the extreme ultraviolet (wavelength: 13.5 nm) lithography used for high-accuracy aspheric mirrors is a promising technology for fabricating semiconductor devices. In addition, ultraprecise mirrors with a radius of curvature of less than 10 mm are needed in many digital video instruments. We developed a new type of nanoprofiler that traces the normal vector of a mirror’s surface. The principle of our measuring method is that the normal vector at each point on the surface is determined by making the incident light beam on the mirror surface and the reflected beam at that point coincide, using two sets of two pairs of goniometers and one linear stage. From the acquired normal vectors and their coordinates, the three-dimensional shape is calculated by a reconstruction algorithm. The characteristics of the measuring method are as follows. The profiler uses the straightness of laser light without using a reference surface. Surfaces of any shape can be measured, and there is no limit on the aperture size. We calibrated this nanoprofiler by considering the system error resulting from the assembly error and encoder scale error, and evaluated the performance at the nanometer scale. We suppressed the effect of random errors by maintaining the temperature in a constant-temperature room within ±0.01°C. We measured a concave spherical mirror with a radius of curvature of 400 mm and a flat mirror, and compared the results with those obtained using a Fizeau interferometer. The profiles of the mirrors were consistent within the range of system errors.

We present an aspheric collimating lens for mid-infrared (4-14 μm) quantum cascade lasers. The lenses were etched into silicon by an inductively coupled plasma reactive ion etching system on wafer level. The high refractive index of silicon reduces the height of the lens profile resulting in a simple element working at high numerical aperture (up to 0.82). Wafer level processes enable the fabrication of about 5000 lenses in parallel. Such cost-effective collimating lens is a step towards the adoption of quantum cascade lasers for all its potential applications.

For interferometric testing of polished surfaces and wavefronts with the best physically accessible accuracy it is good to use a perfect wavefront reference originating from light diffraction by a pinhole aperture in a point-diffraction interferometer (PDI). It is evident that phase shifting (PS) interferometric measurements with the use of the PDI should be fulfilled adequately to perfectness of its wavefront reference unless high accuracy expectations will not be met. High accuracy of the reference beam phase shifting of the two-beam PDI is produced by a two staged alignment procedure being performed on-line when PS fringe patterns (frames) are being saved. This procedure is a time frequency filtering of intensity function of each pixel performed in order to extract regular sinusoids from a set of erroneous and noisy signals. The results of wavefront retrieval from the saved set of PS frames using any N bucket algorithm by the Durango software in both cases – not aligned and aligned – are compared. This research helps keep the PDI accuracy corresponding to perfectness of the wavefront diffraction reference. Also this research may help in PS measurements performed by other types of interferometers where phase shifts are realized by test part movement.

The need for affordable and sustainable ophthalmic systems for measurement and correction of refraction is well-recognized. Power-adjustable spectacles based on the Alvarez principle (transversal lateral movement of two lenses) have emerged as an innovative technology for this purpose. Within this framework our aim is to design novel power-adjustable ophthalmic systems applying a comprehensive optical design methodology. We present two designs using only two lenses: one is a sphero-cylindrical refractor based on three independent lateral movements. The second system is a spectacle providing spherical correction over different gaze directions. Our optical design methodology comprises several stages. We set a merit function where the oblique astigmatism and mean power error were evaluated for different configurations. The lenses have a planar and a third degree polynomial surface. The lenses are arranged with their planar surfaces in contact, so that the incoming light is only refracted by two surfaces. The merit function was optimized following a cascade approach where different surface parameters where optimized at successive steps. The spherical-cylindrical refractor is capable of measuring sphere powers ranging from -5.00 D to +5.00 D and cross-cylinders from -2.00 D to 2.00 D. The astigmatism and power errors are mostly below 0.1 D in absolute value for all the configurations. We also demonstrate a design for hypermetropia and presbyopia correction with a power variation from +0.5 D to +5 D.

A microlens suitable for integration with photonic elements on the same substrate is presented. It is fabricated utilizing planar standard technologies such as UV lithography, ICP-CVD and Deep Reactive Ion Etching. For reaching an optical 3D functionality with 2 D structuring methods a variation of the refractive index during the layer deposition process in the vertical direction is used. For the horizontal direction, parallel to the substrate, the shape of etched side walls determines the focus. This procedure allows the independent control of light propagation in two perpendicular directions with planar technologies. To demonstrate the potential of the technology, optical elements for the collimation of fiber-based light sources are presented.

The SCHOTT glass catalog of 1906 lists the borosilicate crown glass type BK7 for the first time. Since that time it has grown to a high volume glass with equivalents available from all glass manufacturers and became so omnipresent, that many people value it as a cheap bulk commodity type not worthwhile to be looked at closer. This might hold for small thin lenses. However, BK7 can be produced from strip glass format over thick blocks up to large disks of more than 1 m diameter and half a meter thickness. Achieving high homogeneity in thicknesses of 50 mm and above is far from trivial and with increasing thickness it is a challenge even for outstanding glass producers. The present state-of-the-art at SCHOTT is represented by a world record refractive index homogeneity of 1•10^-6 peak-to-valley in block glass with more than 200 x 200 mm² and 100 mm thickness measured in all directions top-to-bottom and in lateral directions. The progress in transmittance led to the introduction of a new quality grade N-BK7HT. The transmittance improvement in the blue-violet spectral range leads to noticeably better twilight vision in use with binocular prisms and image stability in cinema digital projection.

A highly efficient method for splitting the probe beam produced by a scanning low-coherence distance-measuring interferometer (SLCDI) is presented. The SLCDI is used to measure thicknesses of materials with thicknesses in the range of 12 microns-50 mm, with a repeatability of 0.1 microns. The measurements are made optically with a beam with a wavelength of 1.3 microns. The SLCDI is also capable of simultaneous measurement of a stack of multiple films. Splitting of the beam from the SLCDI probe to create a multi-point probe allows for multiple, simultaneous measurements to be made at a surface. An advantage of this capability is that it provides the ability of to measure the surface normal at each of the surfaces that are under test. The operation of the SLCDI will be described along with how the operation impacts the requirements for the multi-point probe system. The requirements are discussed from the standpoint of the coherence length of the SLCDI source and the operational usage of the probe. The splitting is achieved through the use of polarization components. The function and performance of the resulting probe is also discussed.

This paper describes the design of a 3-5microns 26:1 zoom with a focal length extender capability that increases NFOV focal length by 1.75x. Mechanical restrictions for a payload envelope will be considered as well as cold stop efficiency issues.

Especially for optical compound systems the precise geometric alignment of every single element according to the optical design is essential to obtain the desired imaging properties. In this contribution we present a technology for the measurement of the complete set of geometric alignment parameters in assembled systems. During the measurement the deviation of each center or curvature with respect to a reference axis is measured. These data are further processed in order to provide the shift and tilt of every single lens or group of lenses with respect to a defined reference axis. The centering errors of up to 40 surfaces within a system under test can be measured with accuracies in the range of an arc second. In addition, the relative distances of the optical surfaces (center thicknesses of lens elements, air spacing in between) are optically determined in the same measurement system by means of low-coherent interferometry. The measured results can be used for tolerance testing of the sample with respect to the given optical design. In addition, the obtained information can also be applied for the direct compensation of geometrical alignment errors of every single lens in the assembly for the optimized assembly of high-precision optics.

Skew aberration is an intrinsic rotation of polarization states due to the geometric transformation of local coordinates via parallel transport of vectors. Skew aberration is a component of polarization aberration but is independent of the incident polarization state or the coatings applied to the optical interface. Skew aberration occurs even for rays propagating through ideal, aberration-free, and non-polarizing optical systems. Skew aberration is typically a small effect in optical systems but it should be of concern in microlithography optics and other polarization sensitive systems with high numerical aperture and large field of view. The variation of skew aberration across the exit pupil causes undesired polarization components in the exit pupil. Typically cross polarized satellites form around the point spread function (PSF). The PSF and optical transfer function (OTF) are different from ideal PSF or OTF and thus the image quality can be degraded. In the presence of polarization aberration, the scalar PSF and OTF can be generalized to a two-by-two point spread matrix (PSM) or optical transfer matrix (OTM) in Jones matrix notation. We demonstrate analysis of skew aberration effects separate from other polarization aberrations by using a two-by-two PSM and OTM of the U.S. patent 2,896,506. We demonstrate a relationship between skew aberration, Lagrange invariant and the sum of the individual surface powers of the system, using paraxial optics.

The SMS, Simultaneous Multiple Surfaces, design was born to Nonimaging Optics applications and is now being applied also to Imaging Optics. In this paper the wave aberration function of a selected SMS design is studied. It has been found the SMS aberrations can be analyzed with a little set of parameters, sometimes two. The connection of this model with the conventional aberration expansion is also presented. To verify these mathematical model two SMS design systems were raytraced and the data were analyzed with a classical statistical methods: the plot of discrepancies and the quadratic average error. Both the tests show very good agreement with the model for our systems.

In this work, novel imaging designs with a single optical surface (either refractive or reflective) are presented. In some of these designs, both object and image shapes are given but mapping from object to image is obtained as a result of the design. In other designs, not only the mapping is obtained in the design process, but also the shape of the object is found. In the examples considered, the image is virtual and located at infinity and is seen from known pupil, which can emulate a human eye. In the first introductory part, 2D designs have been done using three different design methods: a SMS design, a compound Cartesian oval surface, and a differential equation method for the limit case of small pupil. At the point-size pupil limit, it is proven that these three methods coincide. In the second part, previous 2D designs are extended to 3D by rotation and the astigmatism of the image has been studied. As an advanced variation, the differential equation method is used to provide the freedom to control the tangential rays and sagittal rays simultaneously. As a result, designs without astigmatism (at the small pupil limit) on a curved object surface have been obtained. Finally, this anastigmatic differential equation method has been extended to 3D for the general case, in which freeform surfaces are designed.

Negative Refractive Lens (NRL) has shown that an optical system can produce images with details below the classic Abbe diffraction limit. This optical system transmits the electromagnetic fields, emitted by an object plane, towards an image plane producing the same field distribution in both planes. In particular, a Dirac delta electric field in the object plane is focused without diffraction limit to the Dirac delta electric field in the image plane. Two devices with positive refraction, the Maxwell Fish Eye lens (MFE) and the Spherical Geodesic Waveguide (SGW) have been claimed to break the diffraction limit using positive refraction with a different meaning. In these cases, it has been considered the power transmission from a point source to a point receptor, which falls drastically when the receptor is displaced from the focus by a distance much smaller than the wavelength. Although these systems can detect displacements up to λ/3000, they cannot be compared to the NRL, since the concept of image is different. The SGW deals only with point source and drain, while in the case of the NRL, there is an object and an image surface. Here, it is presented an analysis of the SGW with defined object and image surfaces (both are conical surfaces), similarly as in the case of the NRL. The results show that a Dirac delta electric field on the object surface produces an image below the diffraction limit on the image surface.

To realize wavefront reconstruction for two double-shearing wavefronts produced by our studied cross phase grating lateral shearing interferometer(CPGLSI) in x and y directions, improved wavefront reconstruction using difference Zernike polynomials is studied in this paper. Firstly, the x directional double-shearing wavefronts in the x direction produced by shearing of (+1, +1), (-1, +1) orders diffraction beams and that of (+1,-1), (-1,-1) orders diffraction beams are represented respectively by the corresponding difference Zernike polynomials. Then the whole difference wavefront in x direction is represented by the half value of the sum of the above x directional double-shearing wavefronts. Similarly, the double-shearing wavefronts in the y direction produced by shearing of (+1, +1), (+1, -1) orders and that of (-1, +1), (-1,-1) orders are represented respectively by the corresponding difference Zernike polynomials. Then the whole difference wavefront in y direction is also represented by the half value of the sum of the y directional double-shearing wavefronts. Secondly, the least square fitting is used to obtain the whole wavefront. Investigations on reconstruction accuracy and reliability are carried out by numerical experiments, in which influences of different shearing amounts and noises on reconstruction accuracy are evaluated. The simulation results show that the wavefront reconstruction accuracy can all reach to high accuracy corresponding to different shearing amounts and also validate that our wavefront reconstruction technique is robust to noise.

The optical design of freeform surfaces is particularly demanding due to the inherently large number of degrees of freedom. Therefore the technique of tailoring optical freeform surfaces (mirrors or lenses), which is based on solving the underlying differential equations, is routinely used in nonimaging optics to efficiently achieve predefined light distributions. Tailoring can also be employed for imaging optics: an optical freeform surface can be tailored such that one condition is exactly fulfilled - i.e. spherical aberration at a specific point is corrected. Recently, we extended this method such that two freeform surfaces can be tailored at the same time (double tailoring). This gives the freedom to impose a second condition, which is also exactly fulfilled. Thereby, this method allows for instance to simultaneously correct spherical aberration and satisfy additional conditions, i.e. the sine condition. As an example for a tailored off-axis aplanatic system we show a head-up display (HUD) consisting of two simultaneously tailored freeform mirrors

RUAG Space, together with THALES SESO, initiated the development of light weighted sandwich structures for optical applications, already some years ago. The results of the use of this type of structure applied for optical benches and the first outlook for their use as mirror substrates were published in previous papers. This paper is going to present the results of the polishing activities performed on a 650 mm diameter mirror manufactured with Zerodur face sheets and a low density aluminum core. This substrate showed a mass density of 15 kg/m². The excellent optical quality achieved proves the suitability of this technology for several applications, in particular for scanning mirrors for space and possibly for moveable mirror in ground based astronomical telescopes. With the emerging need for extremely high flatness under thermal loads (radius of curvature < 400km) activities have been initiated to identify materials for the core of the substrate closer matching the extremely low CTE offered by materials like Zerodur. The progresses made in this field are presented and an outlook for future activities is provided.

The BepiColombo Laser Altimeter (BELA) is selected to fly on board of the ESA's BepiColombo Mercury Planetary Orbiter (MPO). The instrument will be the first European planetary laser altimeter system. RUAG Space is the industrial prime for the Receiver part of the scientific instrument. The BELA Receiver is a joined effort of Swiss industries under the leading role of RUAG and University of Bern as co-Prime. A core element is the light weighted Receiver Telescope (RTL), to collect the laser pulse reflected from the planet’s surface. An innovative design was required to deal with the very challenging Mercury’s environmental conditions and with the very stringent instrument’s mass budget. The Optothermo- mechanical analyses lead to the design of a 1250mm focal length Cassegrain telescope made of Beryllium. It provides an aperture of 204 mm diameter and a 2 mm thick primary mirror for a total mass of less than 600gr. The manufacturing and the integration needed special developments. This paper presents the design analyses and the major challenges which had to be solved. Discussing some aspects of the telescope integration and test campaign, the finally achieved performances and lessons learnt will be presented.

RUAG Space developed, manufactured and demonstrated an afocal mirror telescope for space applications. The telescope is part of a Laser Communication Terminal (LCT) for GEO and LEO satellites. The design is off-axis and free of central obscuration. Optical interfaces are provided by pupils outside the telescope towards space (ø=135 mm) and towards the payload (ø=12.5 mm). The magnification is Γ=-10.8. The main characteristics are a WFE of ≤35nm, transmission <96%, low extinction ratio of linear and circular polarization, low stray light and low mass. The performance stability was demonstrated under various environments including vibrations, shock and thermal-vacuum up to 55°C. These properties enable a broad use, not limited to space. The layout is composed of four mirrors (Zerodur and Fused Silica) integrated in a nearly zero expansion Carbon Fibre (CFRP) structure. A detailed characterisation and advanced understanding of the CFRP represents a main achievement. The water absorption of CFRP in air causes elastic distortions of the structure until saturation. Certain optical performances are affected by this phenomenon which has to be considered when testing the system in thermal-vacuum environment. These effects were characterised and precompensated during integration in order to tailor the performance to the in-orbit conditions. The stability of the performances confirmed the selection of the CFRP as nearly-zero CTE material. Combined effects of moisture release and thermo-elastic distortions under thermal-vacuum loads were detected. The optical performances verification was then consequently and successfully tailored in order to distinguish these effects and prove the telescope stability under thermal-vacuum environment.

Martian atmosphere contains two main mechanisms leading the heat transfer process: CO₂ and suspended dust. The flight model (FM) of the current Dust Sensor (DS) of the Mars MetNet Mission has already been fabricated providing only with the ability for measuring the particle size distribution. The optimized DS proposed in this work includes two sub-instruments more for measuring both, CO₂ concentration and ground temperature. This DS will allow correlate the particle size distribution of the airborne dust, the CO₂ concentration and the ground temperature, in a specific location on the Martian surface. All of these parameters will be measured as an in-situ parameter, giving very valuable information about the Martian Planetary Boundary Layer (PBL). The scope of the Mars MetNet Mission is to deploy, in successive flights, several tens of mini atmospheric stations on the Martian surface. Infrared Lab in University Carlos III (LIR- UC3M) is in charge of the design and development of the DS, a micro-sensor (mass <100 g and mean power <1W) which scope is the characterization of airborne dust and other parameters of interest in the heat transfer process. The DS detection principle is of MIE scattering wavelength dependence when particle size is similar to that., so the sensor is provided with spectral resolution,. The optimized DS incorporates angular dependence, so the data retrieval algorithm takes both spectral and angular information making the algorithm most robust. The incorporation of new parameters such as CO₂ and ground temperature is possible thanks to the addition of new sensor elements, properly spectrally tuned. As in the previous DS each parameter is also measured within the MWIR range and the spectral resolution is provided by a interference filter, specifically designed for.

An innovative microscope system had been developed by MDA and INO for planetary exploration applications funded by the Canadian Space Agency (CSA). The device is designed for the capture of low and high resolution images, providing multispectral and colour images, and for 3-D mapping of soil or rock samples. The system consists of a microscope equipped with a monochromatic CMOS sensor, a pattern projector and active multispectral illumination. The compact and lightweight device is intended to be mounted on the robotic arm of a planetary exploration rover developed by the CSA. In image capture mode, the microscope operates on a quite large 400-900 nm spectral band. The illumination of the samples is done using LEDs of different colors turned ON and OFF in sequence providing calibrated reflectance images as well as synthesized color images. Fluorescence imaging is supported by UV illumination at 365 nm. The microscope consists only of fixed optical components. Changing the numerical aperture and resolution of the microscope is done by changing the diameter of the system aperture stop and by pixel binning. The 3-D mapping is done with the Moiré phase shift method. The projection of the Moiré patterns on samples is done with a specially designed video projector equipped with a TI DLP while the microscope acts as the camera. Both the microscope and the projector are modified Offner reflective configurations. The system allows the generation of superb high resolution color images with very large depth of field (focus stacking) or color textured 3-D maps from a set of images acquired at different heights using the 3-D map for the segmentation of the in-focus pixels in each image. This paper briefly describes the concept of the instrument and details the optical design of the optical system. An overview of the key performances is also provided.

The near-infrared spectrograph (NIRSpec) is a complex instrument that will be launched on board the James Webb Space Telescope (JWST). It is composed of three three-mirror anastigmats (TMAs) made of silicon carbide (SiC). Sagem REOSC has been in charge of the mirror polishing, coating, alignment and testing, as well as cryogenic testing. The performance level and the alignment constraints, along with the polishing and alignment processes, have led to the set up of a model to accurately predict the final performances of each TMA, and minimize the risk of vignetting. The model has then been fitted to the measured parameters obtained after alignment (wavefront error, magnification or focal length...) to get an accurate modelization of the actual performances, and allow their evaluation on the full field of view. The model has been finally delivered with each TMA, as a basis for the instrument performance simulator. We will show a good correlation between the predicted performance (before alignment, obtained from individual mirror data) and the final performance (after alignment), as well as a very good fit between the as-built models and the actual TMAs.

IGRINS, the Immersion GRating INfrared Spectrometer includes an immersion grating made of silicon and observes both H-band (1.49~1.80 μm) and K-band (1.96~2.46 μm), simultaneously. In order to align such an infrared optical system, the compensator in its optical components has been adjusted within tolerances at room temperature without vacuum environment. However, such a system will ultimately operate at low temperature and vacuum with no adjustment mechanism. Therefore a reasonable relationship between different environmental variations such as room and low temperature might provide useful knowledge to align the system properly. We are attempting to develop a new process to predict the Wave Front Error (WFE), and to produce correct mechanical control values when the optical system is perturbed by moving the lens at room temperature. The purpose is to provide adequate optical performance without making changes at operating temperature. In other words, WFE was measured at operating temperature without any modification but a compensator was altered correctly at room temperature to meet target performance. The ‘no adjustment’ philosophy was achieved by deterministic mechanical adjustment at room temperature from a simulation that we developed. In this study, an achromatic doublet lens was used to substitute for the H and K band camera of IGRINS. This novel process exhibits accuracy predictability of about 0.002 λ rms WFE and can be applied to a cooled infrared optical systems.

We describe the optical design of MEGARA, the future optical Integral Field Unit (IFU) and Multi-Object Spectrograph (MOS) for the 10.4-m Gran Telescopio CANARIAS (GTC). MEGARA is being built by a Consortium of public research institutions led by the Universidad Complutense de Madrid (UCM, Spain) that also includes INAOE (Mexico), IAA-CSIC (Spain) and UPM (Spain).

We study a periodic Co/Mo₂C multilayer prepared by magnetron sputtering. The period is 4.1 nm and the sample is designed to work around 778 eV, i.e. close to the Co 2p_3/2 threshold, at a glancing angle of 11°. In this condition, strong x-ray standing waves set up within the sample. In order to probe different depths within the stack, particularly the interfaces, the glancing angle is moved along the first Bragg peak, while, the B 1s, C 1s, Mo 3d or O 1s photoelectron spectra, the Co Lα x-ray spectrum as well as the drain current of the sample are measured. Boron is present in the 3.5 nm B₄C capping layer and oxygen is from surface contamination. The photoelectrons bring information from the superficial zone, i.e. the 5 first nm, while the characteristic x-rays probe the whole stack. Clear modulations of the intensity of the studied signals as well as core level shifts are observed when going through the Bragg peak. In order to understand what happens in the multilayer calculations of depth distributions of the electric field and the energy loss by the radiation are made with the IMD and OPAL codes, respectively. The combination of experimental results and theoretical simulations will enable us to determine from which place originate the various signals and to know if some interaction exists between the Co and Mo₂C layers.

Mars-XRD is an X-ray diffractometer developed for in situ mineralogical analysis of the Martian soil. Mars-XRD main components are ⁵⁵Fe radioactive source, collimator and CCD-based detector. For spectroscopic requirements the beam section should be smaller than 1x10 mm² at sample distance. To improve X - ray flux and tuning capability a collimator with converging blades (Soller slits) has been implemented. A dedicated C++ program (XRC-PhOBOS,¹ Photon Output and Blade Optimization Software) investigates for the best Soller slits configuration comparing billion of combinations. The out-coming optimized collimator transmits a flux twice higher than a system with blades with the constant angular aperture and five times higher than a two apertures collimator. Software algorithm, updates and examples are illustrated in present paper.

Recently, we have developed compact modules comprising optical position sensing, and driver electronics, with closed loop control, which can measure the trajectory of resonantly driven 2D-micro-scanner mirrors. In this contribution we present the optical design of the position sensing unit and highlight various critical aspects. Basically position encoding is obtained using trigger signals generated when a fast photodiode is hit by a laser beam reflected from the backside of the mirror. This approach can also be used in the case of 2D-mirrors. In our device the backside of the mirror is hit by two crossed orthogonal laser beams, whose reflections pass cylindrical mirrors in order to suppress the orthogonal dimension. Mirror deflection around one axis is compensated at the plane of the detection diodes while deflection around the other axis leads to a linear displacement of the beam. The optical design of the unit has to provide the optimal compromise between the requirements for small size and simplicity on the one hand and optical accuracy on the other.

Methods are presented that can be used to design and operate optical systems with actively controlled components. Optical systems based on extreme aspheres and freeform surfaces have been investigated. Existing three mirror anastigmat (TMA) designs have been re-optimized in order to achieve two spherical and one challenging (extreme asphere or freeform) mirror surface. We foresee a manufacturing method, where the mirror substrate is plasticised by cold hydro-forming and its surface shape can be controlled via actuators to remove residual errors. Based on singular value decomposition (SVD) and regularization of the sensitivity matrix, the degrees of freedom (DOF) of the active surface can be analysed. Phase diversity (PD) is used as a wavefront retrieval process, to measure the performance metric and determine the sensitivity matrix thus correlating the performance metric of the system and the DOF of the active component.

MarcoPolo-R is a medium-class space mission proposed for the 2015-2025 ESA Cosmic Vision Program with primary goal to return to Earth an unaltered sample from a primitive near-Earth asteroid (NEA). Among the proposed instruments on board, its narrow-angle camera (NAC) should be able to image the candidate object with spatial resolution of 3 mm per pixel at 200 m from its surface. The camera should also be able to support the lander descent operations by imaging the target from several distances in order to locate a suitable place for the landing. Hence a refocusing system is requested to accomplish this task, extending its imaging capabilities. Here we present a three-mirror anastigmat (TMA) common-axis optical design, providing high-quality imaging performances by selecting as entrance pupil the system aperture stop and exploiting the motion of a single mirror inside the instrument to allow the wide image refocusing requested, from infinity up to 200 m above the NEA surface. Such proposal matches with the NAC technical specifications and can be easily implemented with present day technology.

In this work, we have achieved for the first time an effective speckle noise reduction simply by means of just high frequency LD driving current superposition for an ultla compact micro-electro-mechanical-systems (MEMS) based high resolution scanning beam RGB-laser projectors including the direct green emission LD. In the experiments, we have carried out quantitative evaluations of the speckle noise by overlaying the projected images using a CCD camera with histogram based estimation of speckle noise intensities. Moreover, we have examined the reduction of granular images seen by humane eyes in higher ratios in color stereo image pairs using double-stimulus continuous-quality scale (DSCQS) method. As a consequence, the noise reduction rate of 53.5% for the red laser diode, 80.1% for the green laser diode, and 50.3% for the blue laser diode was attained with histogram based estimation, and the image quality was also enhanced by speckle noise reduction with all RGB LD's using DSCQS method. Moreover, we have also investigated the noise reduction mechanisms in these RGB LD's in relation with the relaxation oscillation frequencies from viewpoint of chaotic multi-mode oscillations with existence of optical feedback.

The surroundings of a nuclear fusion reactor experiments the presence of magnetic fields, which affects the performance of any diagnostic optical system located nearby. It is therefore necessary to determine with precision the optimum location for the diagnostic and to design magnetically robust optical imaging systems. The purpose of the present optical diagnostic is to measure the temperature dispersion in the vicinity of the NBI (neutral beam injectors) that heat the confined plasma inside the fusion device. The measure is made by processing the information contained in the images of the objects inside the chamber in the 7 to 16 um far infrared wavelength range, through a F2Ba vacuum viewport window. Our main concern is to design the optical relay from this viewport to the IR sensor, a FPA uncooled microbolometer 320x240px, for different axial distances, with a field of view of 24°x18° and 1.3 mrad of IFOV spatial resolution. The proposed optical relay system includes the use of a reflexive relay (aspheric concave mirrors) and a refractive and imaging camera. The system has being corrected for primary aberrations and optimized to allow a future second optical system working in visible range after the mirrors, by including a dichroic beamsplitter.

In the current retinal imaging systems, laser cavities or astronomical spectroscopes, there is the need to employ off-axis reflective systems. These systems often use different configuration where the object or image could be at finite distances or at infinity with respect to the spherical mirrors. In this work, expressions for the wavefront aberrations in an off-axis spherical mirror with image point or object point from different cases are presented, analyzed and evaluated. Assuming a relatively small pupil and a small angle of incidence, these formulas are derived from the optical path difference between a reference surface (paraboloid, ellipsoid or hyperboloid), and a sphere. They can be used to design and analyze some off-axis reflective systems.

This method of optical scanning presented in this paper is used for precision measurement deformation or absolute forms in comparison with a reference component form, of optical or mechanical components, on surfaces that are of the order of mm² and more. The principle of the method is to project the image of the source grating on the surface to be inspected, after reflection; the image of the source grating is printed by the object topography and is then projected onto the plane of the reference grating to detect defects. The optical device used allows the magnification dimensional surface up to 1000 times the surface inspected, which allows easy processing and reaches an exceptional nanometric imprecision of measurements. According to the measurement principle, the sensitivity for displacement measurement using moiré technique depends on the frequency grating, for increase the detection resolution. This measurement technique can be used advantageously to measure the deformations generated by constraints on functional parts and the influence of these variations on the function. It can also be used for dimensional control when, for example, to quantify the error as to whether a piece is good or rubbish. It then suffices to compare a figure of moiré fringes with another previously recorded from a piece considered standard, which saves time, money and accuracy. This method of control and measurement allows real time control; speed control and the detection resolution may vary depending on the importance of defects to be measured.

The surface microstructure of engine cylinder is critical to its performance. To reduce wear and generated noise, a submicron and even nanometer smooth surface is required, so more requirements are needed for traditional measurement. While interferometric optical profilers are often used for testing surface microstructure and this technique is both noncontact and nondestructive, we set up a cylindrical interferometric measurement system to get the surface shape of engine cylinder wall. This system includes the interferometer, the cylindrical wave converter and a platform with five-dimensional precise adjustment. Considering the aberration affected by the real experiment condition, it is almost impossible to measure the surface profile of the tested object with displacement from a best-fit reference cylinder. In this paper, we set up a model to simulate the interferogram when the axis of measured object is off the cylindrical focus line. As the actual experiment environment, there are four situations about the position error of measured object and the exit pupil wave surface formula for each case can be built by the physical optics. If tested object center is slightly displaced from the focal line, the formula of the wave surface can be simplified. Then we can get the interferogram by using the formula. The paper also compares the simulation results with the ones by Zemax software to verify the testing mode.

The second generation of gravitational wave detectors will aim at improving by an order of magnitude their sensitivity versus the present ones (LIGO and VIRGO). These detectors are based on long-baseline Michelson interferometer with high finesse Fabry-Perot cavity in the arms and have strong requirements on the mirrors quality. These large low-loss mirrors (340 mm in diameter, 200 mm thick) must have a near perfect flatness. The coating process shall not add surface figure Zernike terms higher than second order with amplitude <0.5 nm over the central 160 mm diameter. The limits for absorption and scattering losses are respectively 0.5 and 5 ppm. For each cavity the maximum loss budget due to the surface figure error should be smaller than 50 ppm. Moreover the transmission matching between the two inputs mirrors must be better than 99%. We describe the different configurations that were explored in order to respect all these requirements. Coatings are done using IBS. The two first configurations based on a single rotation motion combined or not with uniformity masks allow to obtain coating thickness uniformity around 0.2 % rms on 160 mm diameter. But this is not sufficient to meet all the specifications. A planetary motion completed by masking technique has been studied. With simulated values the loss cavity is below 20 ppm, better than the requirements. First experimental results obtained with the planetary system will be presented.

EchMod is a MATLAB toolbox designed for the simulation and modeling of high resolution echelle spectrographs. It is designed to allow the rapid calculation of the properties of the most common forms of echelle spectrographs, primarily with astronomical applications in mind. Construction of synthetic 2D images is possible. User in- put spectra may be combined with end-to-end efficiency models to create realistic synthetic spectra. EchMod also allows for an interface to and from Zemax which makes the toolbox useful during the optical design and construction of echelle grating based spectrographs.

The Co-based multilayers have been shown promising optical mirrors for application in the EUV and soft x-ray ranges. Most multilayer systems cannot attain the reflectivity and resolution requirements assumed by theory because of interdiffusion and roughness. Therefore, it is necessary to find out the excellent material possessing optical performance in the EUV and soft x-ray ranges and propose solution to eliminate the interface imperfections or find out new efficient combinations. Here we propose a new system, namely the periodic Co/Mo₂C multilayer. The multilayer systems are prepared by the magnetron sputtering and characterized by x-ray reflectivity at 8048 eV (Cu Kα emission) and with synchrotron radiation in the soft x-ray range at 778 eV. The measurements are used in order to determine the structural parameters (thickness, roughness and density) of the layers. The simulated reflectivity at 11° grazing angle with s-polarized is calculated to be 45% at 778 eV, if there is no interaction between the layers and no interfacial roughness, while experimentally reflectivity is limited to 25%. The relationship between the reflectivity and annealing up to a temperature of 600°C is also investigated. It shows that the Co/Mo₂C multilayer is able to work up to 600°C. First the reflectivity increases to 27% at 300°C. After the reflectivity slightly decreases to 25% at 500°C and then we observe a reflectivity drop to 20% at 600°C. Relationship between the structural parameters and the reflectivity values is deduced from the fit of the experimental curves.

The preliminary design of a polychromator unit for a Raman lidar (Light Detection And Ranging) for atmospheric calibration in the framework of the Cherenkov Telescope Array (CTA) project is presented. To obtain high quality data from CTA, a precise monitoring of the atmospheric transmission is needed. Remote-sensing instruments, like elastic/Raman lidars, have already been proven a powerful tool in environmental studies, and a lidar installed and operated at the CTA site is foreseen for correcting systematic biases on the energy and flux. The lidar we discuss here consists of a powerful laser that emits light pulses into the atmosphere, a mirror of 1.8 m diameter that collects the backscattered light and a polychromator unit where the light is analyzed. The laser is a pulsed Nd:YAG with the first two harmonics available at 355 and 532 nm and the polychromator has 4 read-out channels: two to analyze the elastic backscattering at 355 and 532 nm and two for the Raman Nitrogen back-scattered light, at 387 and 607 nm, respectively. The polychromator module needs to collect the majority of the light coming from the telescope, to split the different wavelengths and to focus the beams onto photomultiplier detectors. The collection and focalization of the beams are done by means of simple lens-couples and the separation with custom-made dichroic mirrors and narrow-band filters. The performance of the conceived optical design, the adopted design choices for the glass, surface figure and size of the lenses, and the expected throughput for the different channels are hereafter described.

A new high-speed slope measuring instrument is currently under development for small-aperture aspheric lenses and mirrors. In the present study, normal vectors at each point on the lens surface were determined using the reflected light beam that follows the same path as the incident beam. The capability of the developed instrument to achieve submicroradian surface slope metrology of a small-radius aspheric lens was verified. The paper also describes in detail the design principle, aspheric lens measuring method, initial alignment and calibration procedure, shape determination procedure developed from the measured slope metrology, and the high-speed slope measuring technique.

In our previous paper, on dynamic handling of massive micro-bead arrays, we developed a hybrid optical tweezers system consisting of two multi-beam techniques: the GPC method and the galvano mirrors (GMs) scanning method. This system had high versatility for manipulating massive arrays, but arrays formed by its GM scanning tweezers could be handled only in a two-and-half dimensional (2.5D) working space. This limitation arose from the low bandwidth of the Z-axis manipulation due to the lens translation using a linear stage. For true 3D controlled manipulation of multiple micro-beads, in this paper, we redesign the GM scanning part of the previous hybrid system using an electrically focus-tunable lens with high bandwidth. The optical structure is linked to a commercially available microscope via its epifluorescence port. One set of optical tweezers based on the GPC uses the p-polarized beam, and the other set based on the GM scanning uses the s-polarized beam. In the results of the 3D manipulation experiment, the controlled rotation of five beads forming a pentagon and that of four beads forming a tetrahedron about arbitrary axes are demonstrated.

FIRI (Far Infrared Interferometer) is a concept for a spatial and spectral interferometer with an operating wavelength range 25-300 μm and sub-arcsecond angular resolution, and is based in the combination of two well-known techniques, Stellar Interferometry and Fourier Transform Spectroscopy to achieve high spectral and spatial resolution in the Far Infrared. The resulting technique is called Double Fourier Spatio-Spectral Interferometry (Mariotti and Ridgway 1988). With increased spatial and spectral resolution a number of interesting science cases such as the formation and evolution of AGN and the characterization of gas, ice and dust in disks undergoing planetary formation, among others, can be investigated. Here the current status of the design of the FIRI system via an instrument simulator is presented, as well as the results of a test-bed implementation.

In this paper we present a technique to accurately build a 3D hyperspectral image cube from a 2D imager overlaid with a wedge filter with up to hundreds of spectral bands, providing time-multiplexed data through scanning. The correctness of the spectral curve of each pixel in the physical scene, being the combination of its spectral information captured over different time stamps, is directly related to the alignment accuracy and scanning sensitivity. To overcome the accumulated alignment errors from scanning inaccuracies, frequency- dependent scaling from lens, spectral band separations and the imager’s spectral filter technology limitations, we have designed a new image alignment algorithm based on Random Sample Consensus (RANSAC) model fitting. It estimates many mechanical and optical system model parameters with image feature matching over the spectral bands, ensuring high immunity against the spectral reflectance variations, noise, motion-blur, blur etc. The estimated system model parameters are used to align the images captured over different bands in the 3D hypercube, reducing the average alignment error to 0.5 pixels, much below the alignment error obtained with state-of-the-art techniques. The image feature correspondences between the images in different bands of the same object are consistently produced, resulting in a hardware-software co-designed hyperspectral imager system, conciliating high quality and correct spectral curve responses with low-cost.

In this contribution we propose methods for vehicle detection and tracking for the Advanced Driver Assistance Systems (ADAS) that work under extremely adverse weather conditions. Most of the state-of-the-art vehicle detection and tracking methods are based either on appearance based vehicle recognition or on extraction and tracking of dedicated image key points. Visibility deterioration due to rain drops and water streaks on the windshield, swirling spray, and fog lead to a drastic performance reduction or even to a complete failure of these approaches. In this contribution we propose several methods for coping with these phenomena. In addition to an extension of the feature-based tracking method, which copes with outliers and temporarily disappearing key points, we present a detection and tracking method based on search for vehicle rear lights and whole rear views in the saturation channel. Utilization of symmetry operators and search space restriction allows to detect and track vehicles even in pouring rain conditions. Furthermore, we present two applications of the above-described methods. Estimation of the strength of spray produced by preceding vehicles allows to draw conclusions about the overall visibility conditions and to adjust the intensity of one's own rear lights. Besides, a restoration of deteriorated image regions becomes possible.

Copper is a heavy metal, which is used in heat and electrical conductors and in a multitude of alloys in the technical context. Moreover, it is a trace element that is essential for the life of organisms but can cause toxic effects in elevated concentrations. Maximum limits in water and for beverages exist. Beyond that there is a need for the control of copper concentrations in the fields of sewage and agriculture. Hence, competitive measurement systems that allow for the fast, user-friendly and reliable detection are presumed to have a large potential market. One prominent class of naturally occurring fluorophores is the Green Fluorescent Protein (GFP). GFP originally stems from the jellyfish Aequorea Victoria and has found its way in various applications e.g. as biosensors in basic research and for monitoring gene expression. Exploiting GFP in plant cells allowed for the visualization of the copper uptake by changes in the GFP fluorescence. In principle changes in the fluorescence intensity or in the fluorescence lifetime can be utilized to determine copper concentrations. However, lifetime changes have the advantage of omitting calibration measurements and therefore make this method ideally suited for sensing purposes. Here the decrease of the fluorescence lifetime of GFP by Förster resonance energy transfer (FRET) is used to measure the copper ion concentration in drinking water. Therefore a system is developed that is based on a GFP sample in a predefined concentration. The GFP mutant can be excited with blue light. For binding of copper ions a His-tag is included in the GFP. After measuring the fluorescence lifetime of the pure GFP the copper determination of the sample is performed by lifetime measurement. Therefore the lifetime can be assigned to the copper concentration of the GFP-doped drinking water sample. In summary a method for the quantification of copper ions based on changes of the fluorescence lifetime of GFP is developed and the measurement of the copper concentration in water samples is performed.

The paper considers results of design and simulation of analogue-digital converters (ADC) based on current mirrors for the multi-sensor systems with parallel inputs-outputs. Such ADCs are named us as multichannel serial-parallel analog-to-digital converters based on current mirrors (M SP ADC CM). Compared with usual converters, for example reading, a bit-by-bit equilibration, and so forth, the proposed converters have a number of advantages: high speed and reliability, simplicity, small power consumption, the big degree of integration in linear and matrix structures. We discuss aspects of the design of M SP ADC CM in Gray and binary codes. It is offered, investigated and simulated the 6, 8 and more digit M SP ADC CM in Gray code and binary codes. Each channel of the overall structure consists of several base digit cells (ABC), with options for low power consumption with only one such ABC and analog memory (less than 20 CMOS transistors). Base digit cells (АВС) of such M SP ADC CM, series-pipelined in structures, consist of 20-30 CMOS transistors, one photodiode, have low (1-3.3) V supply voltage, work in current modes with the maximum values of currents (10-40) μA. Therefore such new principles of realization of high-speed low-digital M SP ADC CM have allowing, as shown by simulation experiments, to reach time of transformation less than 20-30ns at 5-8 bits of binary code and Gray code and the power consumption 1-5mW. The quantity of easily cascadable АВС depends on multi-bit ADC, and makes n, and provides quantity of quantization levels equal N=2ⁿ. Such simple structure of M SP ADC CM with low power consumption ≤3÷5mWand supply voltage (3-7)V, and at the same time with good dynamic characteristics (frequency of digitization even for 1.5μm CMOS-technologies is 40 MHz, and can be increased up to 10 times) and accuracy (Δ_quantization=156,25nA for I_max=10μA ) characteristics are show. The range of optical signals, taking into account sensitivity of modern photo-detectors, can be 20-200 μW. Each channel of ADC, to reach the general power 50-100_μW for low power consumption, can consist of only one such ABC and analog memory. To implement such serial ADC no more than 40 CMOS transistors are needed. The M SP ADC CM opens new prospects for realization linear and matrix (with picture operands) micro photo-electronic structures which are necessary for neural networks, digital optoelectronic processors, neural-fuzzy controllers, and so forth.

This paper presents a high dynamic range imaging sensor for detection of low light level signals. The sensor utilises a 12x12 array of large 150μm x 150μm pixels. The readout circuitry allows for multiple readout options including; multiple sampling (which allows for techniques such as Correlated Double Sampling (CDS)) and Time to Digital Conversion (TDC) techniques, operated both independently and under the same integration period. Scope for test patterns is also present in the design. All samples taken from the pixels before during and after exposure are converted digitally through the use of a single slope ADC utilising a 10 bit DAC and a comparator. No sample and hold capacitor is present. 4x10 bit SRAMs (Static Random Access Memory) per pixel are utilised to record multiple samples, or act as a counter for the TDC mode of operation. The large dynamic range of the system is attributable to both the novel timing system implemented within the multiple sampling mode of operation and the TDC mode of operation (operated independently or intermittently within the same integration time), which combines the use of 4x10 bit SRAMs with the 10 bit DAC to produce a counter capable of monitoring the pixel signal over extremely long integration times; in this case up to 30 seconds.

InGaAs/InP SPADs are solid-state devices able to detect near-infrared single photons up to 1700 nm. The pn junction is defined by Zn diffusions in a lightly n-doped InP layer. If a simple Zn diffusion were employed, it would suffer edge effects; therefore a double diffusion is used in order to smooth the electric field at the periphery of the active area. However, since most of the main parameters of the SPAD depend on the electric field profile, it is of outmost importance to properly evaluate the electric field, both in the active area and at its periphery. Currently-available programs for 2D simulations require heavy and long computations and are not tailored for SPAD performance assessment, thus often 1D custom simulation is performed for qualitative evaluation of “detection” characteristics. We present two 1D and 2D device simulators designed for InGaAs/InP SPAD detectors and the models we implemented therein. We compare the differences in the results between the 1D and 2D approaches in terms of electric field profile, breakdown voltage, trigger efficiency and dark count rates. The 1D simulator overestimates breakdown voltage by few percent, while the 2D simulator matches the measured values. We show how trigger efficiency is not constant in the device and how the high electric field near the edges contributes to increase the dark count rate due to tunneling effects.

The thermal sensor system presented in this paper is based on the mechanical bending due to the incident IR radiation. A diffraction grating is embedded under each pixel to facilitate optical readout. Typically the first diffraction order is used to monitor the sub-micron mechanical displacement with sub-nanometer precision. In this work; two different optical readout systems based on diffraction gratings are analyzed. First setup employs a conventional 4f optical system. In this one-to-one imaging system, collimated light is propagated through a lens, filtered with an aperture and then imaged onto a CCD by a second lens. Second system is more compact to improve image quality and to reduce noise. This is achieved by using an off-axis converging laser beam illumination that forms the Fourier plane near the imaging lens. This approach has important advantages such as reducing number of optical components and minimizing the optical path. The system was optimized considering parameters such as laser converging angle, laser beam size at MEMS chip, and magnification of the imaging system.

It is shown that electron heating by electromagnetic radiation in MCT layers can be used for designing of uncooled THz/sub-THz detectors with appropriate for active imaging characteristics (NEP ~2.6•10^-10 W/Hz^1/2 at ν ~ 140 GHz) and these detectors can be manufactured within well established MCT technologies. This narrow-gap semiconductor can be considered as a material for THz/sub-THz detectors with possibility to be assembled into arrays. The characteristics of those detectors can be controlled and improved by selection of parameters of initial layers, substrate properties and antennas configuration. For FET detectors, even for transistors with rather long channels (~ 1 μm) rather similar characteristics at ν ~ 140 GHz can be obtained too.

Analysis of multiple factors affecting the uncertainty of the absolute spectral responsivity of optical radiation detectors is presented. This includes both the validation of the radiometric scale of the infrared reference detectors and the scale transfer process to the unit under test. Reference detectors include a low NEP pyroelectric detector, an InSb detector, and a sphere-input extended InGaAs detector. While all three types of reference detectors were calibrated independently, less than 0.5 % mismatch of spectral responsivities was observed in the spectrally overlapping regions. We provide a performance evaluation of the NIST IR Detector Calibration Facility, which was designed for testing optical radiation detectors in both radiant power and irradiance measurement modes. This facility utilizes a high throughput monochromator with interchangeable diffraction gratings. Depending on the spectral range, a blackbody at 1100°C, or a quartz halogen lamp with about a 10^-4 long-term relative output variation was used as a radiation source. In order to minimize the uncertainty budget for calibration data, specific attention was given to the profile of the incident beam, the precise positioning of detectors, and the influence of atmospheric absorption. In addition to the spectral responsivity calibration of detectors, the facility allows precise mapping of detector active area for spatial non-uniformity of response. Typical calibration uncertainties that can be achieved are about 1 % and 2.5 % (k=2) in the radiant power and irradiance modes, respectively. Examples for responsivity calibrations of different detectors are presented.

To measure the concentration of a fluid under consideration by means of tunable diode laser spectroscopy an algorithm for automatic detection of absorption transitions has been developed. The algorithm consists of a three step process. In the first step, necessary information is taken from the HITRAN database. Measured data are analyzed in the second step in order to eliminate the laser characteristics underlying the absorption spectrum, to localize the absorption lines and to get convenient initial values for fitting the absorption transitions to a Lorentzian line shape profile in step 3. The concentration is calculated from the best approximation among all parameters from the transitions found on the signal. The developed algorithm was tested with a set of simulated curves with different concentrations of carbon dioxide transitions at the 2.004 μm band and it could analyse concentrations with relative error better than 1% for concentrations down to approximately 200 ppb. Computation time including acquisition time and graphical output display is fast enough to enable online monitoring of fluid concentrations.

Geometrization of the temporal photoresponse of the semiconductor compounds by means of it transformation to the dynamic and wavelet signatures provides quality new possibilities for the spatial-temporal order analysis of the photoresponse. This approach allows to define the both «rough» dynamic and «thin» informative constituents in the multiscale dynamic structure of sensor’s photoresponse. It is shown that spatial-temporal disorder in photoresponse is caused by the induced rearrangement of the multiscale dynamic structure over different time-frequency domains. Generally, the results of this study indicate that the overall form of the organization of responses from sensor materials is determined by the spatial and temporal ordering of its structure. Offered approach was found an effective for the decision of serial of associate technological, diagnostic and operating problems of modern complex semiconductor compounds.

The rapid improvement of the LED-efficiency in the visible range and the availability of UVA-LEDs motivated us to perform a feasibility study focused on developing a light module powered only with LED sources for photostability tests in constant climate chambers. We first carried out a market analysis to identify suitable LEDs for this application. Secondly, a new opto-mechanical light module was developed and optically simulated with the software LightTools®. The geometrical distribution of all LEDs was optimized to provide uniform illumination at a given distance and a spectral distribution according to the guideline ICHQ1b for photostability tests. Finally, an opto-mechanical prototype was built up and measured. Both irradiance/illuminance measured values and spectral distribution were in very good agreement with the optical simulation values. The uniformity too was better than predicted and within the 10% target value. Nevertheless, in a further optimization, a 3D-textures pattern was added on the front size of the glass plate located under the LEDs. According to the final optical simulation results this typical backlighting optimization provides an additional improvement of the uniformity. In conclusion, we have demonstrated that LEDs can already provide an efficient optical alternative to classical fluorescent lamps in this demanding industrial application field. But two few UVA-LEDs with the right wavelength and power are available on the market. And none has undergone the reliability tests required by this application (humidity, temperature, lifetime )

LEDs are substituting fluorescent and incandescent bulbs as illumination sources due to their low power consumption and long lifetime. Visible Light Communications (VLC) makes use of the LEDs short switching times to transmit information. Although LEDs switching speed is around Mbps range, higher speeds (hundred of Mbps) can be reached by using high bandwidth-efficiency modulation techniques. However, the use of these techniques requires a more complex driver which elevates drastically its power consumption. In this work an energy efficiency analysis of the different VLC modulation techniques and drivers is presented. Besides, the design of new schemes of VLC drivers is described.

For Solid State Lighting devices thermal management has a great impact on the performance. Therefore, it is necessary to analyze thermal and optical behavior simultaneously due to the mutual interaction between the two. For a remote phosphor configuration the dependence of the device performance on thermal conductivity and refractive indices of phosphor’s host material is investigated. Even though the temperature range inside the phosphor can be dramatically reduced by choosing the right material, the overall performance suffers from the low extraction efficiency of light due to the high refractive index of the chosen material.

In this work the concept of tracking integration in concentrating photovoltaics (CPV) is revisited and developed further. With respect to conventional CPV, tracking integration eliminates the clear separation between stationary units of optics and solar cells, and external solar trackers. This approach is capable of further increasing the concentration ratio and makes high concentrating photovoltaics (< 500x) available for single-axis tracker installations. The reduced external solar tracking effort enables possibly cheaper and more compact installations. Our proposed optical system uses two laterally moving plano-convex lenses to achieve high concentration over a wide angular range of ±24°. The lateral movement allows to combine both steering and concentration of the incident direct sun light. Given the specific symmetry conditions of the underlying optical design problem, rotational symmetric lenses are not ideal for this application. For this type of design problems, a new free-form optics design method presented in previous papers perfectly matches the symmetry. It is derived directly from Fermat's principle, leading to sets of functional differential equations allowing the successive calculation of the Taylor series coeficients of each implicit surface function up to very high orders. For optical systems designed for wide field of view and with clearly separated optical surfaces, this new analytic design method has potential application in both fields of nonimaging and imaging optics.

Lateral moving optics along straight path has already been studied in the past. However, their relative small angular range can be a limitation to potential applications. In this work, a new design concept of SMS moving optics is developed, in which the movement is no longer lateral but follows a curved trajectory, which is calculated in the design process. We have chosen an afocal system, which aim to direct the parallel rays of large incident angles to parallel output rays, and we have obtained that the RMS of the divergence angle of the output rays remains below 1 degree within a input angular range of ±45 output. Potential applications of this beam-steering device are: skylights to provide steerable natural illumination, building integrated CPV systems, and steerable LED illumination.

Optical design tools allow more and more complete physical phenomena simulation and illumination design itself becomes more and more complex. A big part of these designs uses volume scattering materials. However, those are not yet implemented in such tools. For this reason we worked on a way to characterize volume scattering materials. How can we characterize and implement volume scattering materials in optical design tool for illumination design? We worked on two ways of characterizing volume scattering materials based on real Bidirectional Scatter Distribution Function (BSDF) measurements made with Reflet bench. LightTools software with its Henyey-Greenstein and Mie scattering model was also used in the process of material characterization. The study showed that the results with both Henyey and Mie characterization, allow simulation of volume scattering materials within of 5% precision compare to real measurements. Thanks to such simulations it is now possible to have custom shape illumination design using volume scattering materials from a library. Sony Ericson was the first user to benefit from these study’s results.

The optical design of a laser scanning picoprojector can be separated into discrete tasks. Typically, diode lasers are employed and their highly divergent emission is firstly collimated. Some beam shaping is required since the asymmetric divergence from diode lasers is converted to an elliptical collimated beam. The red, green and blue beams then need to be combined to produce a single beam which can be controlled to present any colour of the available colour gamut. The final step of the process is to direct the combined beam towards a MEMS scan head comprising a single, bi-axis or two, single axis scanning micro-mirrors. There is currently an impetus to embed picoprojector opto-electro-mechanics into other devices such as mobile telephones and this restricts the 3D volume available for the collimation, beam combination and MEMS scan head. Even for a standalone picoprojector there is an incentive for a compact design. So along with conventional optical engineering tasks such as lens design, Gaussian beam propagation, tolerancing, laser safety and design for manufacture, there is an additional task of determining the best optical architecture to achieve the goal. Here we present a design study of a laser scanning picoprojector where the various optical architecture possibilities are presented. A novel solution is presented which has been built as a prototype projector and which offers excellent future miniaturisation possibilities.

Collimators for spot LED lamps have to meet stringent requirements like high efficiency and on axis intensity, good beam control, color and position mixing, low cost, and a low aspect ratio to enable compact devices with sufficient space for drive electronics and cooling. To meet such requirements only very few optical architectures are routinely used, namely Fresnel lenses, parabolic or aspheric reflectors, and TIR lenses, often called Photon funnels. Collimators make use of five different deflection mechanisms, namely refraction, total internal reflection, metallic or metallic like reflection, scattering, and diffraction. Light, when travelling through a given collimator type undergoes a characteristic sequence of deflections but many collimators exhibit different paths where portions of the light undergo different deflection sequences. In this paper we illustrate the design space for collimators for a single Lambertian LED or LED array source located on the optical axis under the boundary conditions of low aspect ratio, rotational symmetry and minimum Etendue dilution. All possible optical architectures with up to 4 deflections are mapped out in terms of paths of distinct deflection sequences. The important characteristics of deflection sequences are investigated. For a given collimator, the deflection paths involved allows predicting efficiency, on axis intensity, and compactness. Additionally the beam shape as well as position and color mixing capabilities can be estimated from the influence of the deflection sequence on pinhole image rotation and distortion. Such results are compared to raytrace results for some designed collimators of standard and uncommon architectures.

The method for computation of LED optical elements with two aspherical surfaces and the highest possible efficiency is presented. The series of optical elements producing uniformly illuminated circle regions were computed and simulated with point light source. The simulation data shows that such optical elements have good performance for all angular sizes of the illuminated region (from 0° to 160°) including cases of full collimation and illumination of wide regions. The proposed design method works well with extended light sources too. The optical element with height of 7 mm generating uniformly illuminated region with angular size of 60° was simulated with extended light source 1x1 mm. The light efficiency decreased by 1-2 % only and the irradiance distribution remained the same. Taking into account the small dimensions of the proposed optical elements they can compete with TIR-optics in cases of generation narrow-angle light distributions.

GaN-based blue LEDs with various types of phosphor has been providing high brightness in lighting application with the integration of various nonimaging optical parts for controlling luminous intensity distribution. Such secondary optics, particularly in road lighting, inherently lose light flux of 15% with additional manufacturing and assembling cost. Making primary optics of LED as functional as secondary optics will cut off this additional cost and further increase the efficacy of luminaire. In this paper, we present the design procedure of LED primary optics as functional as road lighting secondary optics. The compact freeform lens has been designed with precise optical modeling of the target LED. Machining of primary optics mold comprise a determinant solution in generating specific luminous intensity distribution for road lighting. Optical performance of the primary optics had advantages of much smaller size in volume (~1/10), lumen efficacy (~93.9%).

Luminous power LED technology has been improving quite fast and it will replace completely the lighting components that are used currently in the present decade due to its lighting advantages. This study was carried out to determine illumination efficiencies of power LED drivers and optics. The buck-based type LED driver was selected for this study. On this way, power LED driver circuit was designed using switching current regulator and circuit component values were computed for maximum light output efficiency. A reflector which will enable uniform distribution of the maximum power LED illumination to be obtained by using this driver circuit was investigated. In this case, diffusers and Fresnel lenses were proposed depending on the use. Diffusers can be used for indoor iluminations combined with reflectors. To this end, also Fresnel lenses were investigated.

The advent and rapid development of efficient high power LED sources with their unique emission characteristics enables the development of illumination systems that meet very strict requirements concerning light distribution and efficiency. Most of the algorithms used to design the necessary optical freeform surfaces rely on the point source assumption. As long as the distance between LED and those surfaces is sufficiently large, this is a good approximation. One further important design goal is to make the optical components as small as possible, which makes the point source assumption less accurate. The existing design algorithms thus have to be accompanied by methods to treat the finite-sized LED sources. We examine the limits that are set by the finite size of the light sources and present algorithms to optimize optical freeform surfaces up to these limits. Point source results are iteratively improved to get the desired illumination pattern employing finite sized LEDs. At each iteration step the illumination pattern used in the point source computations is adapted so that the real illumination pattern of an LED approximates the originally desired pattern.

The increasing efficiency of high power LEDs has resulted in many new applications in general lighting. To take full advantage of the properties of LEDs, free-form surfaces can be utilized to create compact non imaging optical systems with high efficiencies and high degrees of freedom for optical designers. One of the commonly used methods to do optical design for this kind of systems is optimization. Appling this powerful tool allows the enhancement of given optical elements to achieve a desired performance. In this way, free form surfaces which are usually represented by NURBS, can be optimized and applied even close to an extended LED light source. However, using optimization for free-form surfaces is far from being straight-forward and requires a lot of experience mostly due to the high amount of possible optimization variables for NURBS. This comes along with high, computational effort and difficulties concerning the choice of boundary conditions and merit functions. This contribution presents a novel non-imaging optical design approach using the concept of free-form deformation (FFD) in conjunction with customized optimization algorithms to create efficient optical free-form surfaces for extended LED light sources. Within this framework, specific coordinate system transformations are used to modify the global shape of free-form surfaces. In this way, optimization techniques relying on relatively few and easily accessible variables can be applied successfully. All presented concepts are implemented in a flexible and fully automated FFD optimization software tool incorporating a commercial raytracer and numerical optimization techniques. Several examples are presented in detail and the scope of FFD based optimization is demonstrated.

Aplanatic designs present great interest in the optics field since they are free from spherical aberration and linear coma at the axial direction. Nevertheless nowadays it cannot be found on literature any thin aplanatic design based on a lens. This work presents the first aplanatic thin lens (in this case a dome-shaped faceted TIR lens performing light collimation), designed for LED illumination applications. This device, due to its TIR structure (defined as an anomalous microstructure as we will see) presents good color-mixing properties. We will show this by means of raytrace simulations, as well as high optical efficiency.

A strategy to obtain sets of initial configuration to design freeform reflector surfaces is presented. This strategy brings the initial configuration of the reflector surface using a collection of elemental facets defined by Bezier surfaces and able to face the optimization process of the illumination system. The purpose of this communication is to provide initial configurations to obtain a set of parameters defining the freeform facets described by Bezier curves. Those parameters can be modified by a global optimization process of the lighting system. This task can be accomplished using a set of simple geometric elements that are the basis for calculating a first approximation to the facet surface. The proposed strategy provides a simple geometric design method to perform valid initial configurations for lighting systems with reflective surfaces that can be further optimized. The method to calculate the geometry of every single facet is based on ray tracing and uses a merit function to find the parameters defining the Bezier curve that best meets specifications in each elementary facet. Applying this method to 2D tangential and sagital axes, a network of control points are obtained for describing a Bezier surface compatible with any standard optical optimization tool and suitable for viewing with CAD tools.

Two quasi-aplanatic free-form solid V-groove collimators are presented in this work. Both optical designs are originally designed using the Simultaneous Multiple Surface method in three dimensions (SMS 3D). The second optically active surface in both free-form V-groove devices is designed a posteriori as a grooved surface. First two mirror (XX) design is designed in order to clearly show the design procedure and working principle of these devices. Second, RXI free-form design is comparable with existing RXI collimators; it is a compact and highly efficient design made of polycarbonate (PC) performing very good colour mixing of the RGGB LED sources placed off-axis. There have been presented rotationally symmetric non-aplanatic high efficiency collimators with colour mixing property to be improved and rotationally symmetric aplanatic devices with good colour mixing property and efficiency to be improved. The aim of this work was to design a free-form device in order to improve colour mixing property of the rotationally symmetric non-aplanatic RXI devices and the efficiency of the aplanatic ones.

High flux and high CRI may be achieved by combining different chips and/or phosphors. This, however, results in inhomogeneous sources that, when combined with collimating optics, typically produce patterns with undesired artifacts. These may be a combination of spatial, angular or color non-uniformities. In order to avoid these effects, there is a need to mix the light source, both spatially and angularly. Diffusers can achieve this effect, but they also increase the etendue (and reduce the brightness) of the resulting source, leading to optical systems of increased size and wider emission angles. The shell mixer is an optic comprised of many lenses on a shell covering the source. These lenses perform Kohler integration to mix the emitted light, both spatially and angularly. Placing it on top of a multi-chip Lambertian light source, the result is a highly homogeneous virtual source (i.e, spatially and angularly mixed), also Lambertian, which is located in the same position with essentially the same size (so the average brightness is not increased). This virtual light source can then be collimated using another optic, resulting in a homogeneous pattern without color separation. Experimental measurements have shown optical efficiency of the shell of 94%, and highly homogeneous angular intensity distribution of collimated beams, in good agreement with the ray-tracing simulations.

An optical system was designed and fabricated to achieve signal wavelength conversion. Although a rare-earth doped phosphor was useful to achieve the infrared-to-visible conversion, its long-lasting phosphorescence prevented high-frequency modulation. This problem was solved by using a time-space conversion method, in which a phosphorescent disk was rotated to attain the fast-response wavelength conversion. When an infrared pulse train with 500-ns duration and 1-MHz repetition rate was focused on the rotating disk, phosphorescent dots were created along the disk periphery. By detecting the phosphorescence at a downstream position of the dot trajectory, a visible signal of 1 MHz was observed.

Cylindrical prismatic hollow light guides are able to transmit daylight properly into the spaces of a building in which natural light has a difficult access. Transmission through the guide depends on the optical characteristics of the material, the shape of the guide and the fidelity of the geometry in prisms structure. It is important to analyse the micro-structure prism imperfections of the surfaces such as the existence of a curved area on peaks prism which modify the behaviour of the prism film; these imperfections, change the optical path and therefore the rays are directed to other directions instead of undergoing total internal reflections. In this paper, several cylindrical guides made of transparent dielectric material characterized with an absorption factor have been developed. A numerical analysis has been carried out by software tools to analyse the flux distribution in the light guidance system comparing its efficiency by optical analysis in different simulations. These simulations include high reproductively prism related to the light pipe’s material and optical properties including a study of the impact of imperfect geometry which is necessary to allow rigorous comparisons with the experimental simulations. The simulated results have been compared with experimental data obtained through real scale analysis. The experimental measurements have revealed effectiveness of 66.7 % in the aspect ratio of 30.

The new optimization method for design of LED optical elements working on the total internal reflection principle is proposed. The optimization method includes the quick raytracing technique adapted for axis-symmetrical surfaces and processing more than hundred thousand rays per second. The raytracing technique based on the approximation of the surface of revolution by a set of truncated cones is presented. As an example, the compact optical element producing uniformly illuminated circle region with angular size of 50° for an extended light source 1x1 mm is computed and simulated. The light efficiency of the designed optical element is about 91.3% and the root-mean-square error of the generated irradiance distribution is less than 10%.

Durability of LEDs is usually specified to 10,000 hours though numerous LED products feature a lesser operation life. This might be caused by faulty constructions or improper physical environments and operating conditions. Since such failure cannot be accepted for cost intensive applications in automotive, medical or illuminating engineering simulation based prediction of LEDs durability is a promising design approach. Main causes of degradation are manufacturing and operation temperatures or temperature gradients, respectively. These result in an increased diffusion, accelerated chemical reactions and induced material stresses. In a consequence, chemical, physical and mechanical properties of parts are altered. To investigate conditions of LED operation, LEDs degradation and conditions of failure a test environment considering electrical and thermal loads as well as optical emission has been designed. Furthermore, the LED test environment has been modelled within the software application MatLAB/Simulink to simulate and predict the durability of complex LED-systems. Test environment, computer-aided simulation and a test design using design of experiments are combined to a design tool named MValEnt. This supports validation and design of complex LED-systems for varied conditions of operations and component characteristics. Integrated data interfaces provide an iterative product development. Load measurements reveal different failure mechanisms due to characteristics of operating current, ambient temperature and pulse-width modulation (pwm) as well as operation interruptions. Electrical and thermal coupling of LED circuits results in additional loads and thus degradation. With increasing power mechanisms of LEDs degradation are comparable to those found in power electronics.

Lithography is the key technology to semiconductor manufacture. With the rapid improvement of projection lens and resolution enhancement technique (RET), the essence of the illuminator can never be overestimated in the lithography system. However, due to various and complex components and the fact that fewer design methods were proposed in the papers compared with those of the projection lens, a detailed design method for the illuminator is needed. This paper introduces the detailed design process for the illuminator in a NA 0.75 lithography system on 90nm node. The exposure field at the reticle plane is 104mm×42mm. The illuminator mainly consists of three parts: the beam shaping unit, the uniformizer and the relay lens. In order to construct the matching relationship among the various components in the illuminator, a design method based on the fly’s eye, which is the core and starting point, has been proposed. This method has been successfully used in small field lithography system. With this method, the matching relationship in the illuminator can be determined easily, and the illumination NA and size are guaranteed simultaneously. Furthermore, the detailed design for some key issues in the illuminator is given: the diffractive optical element (DOE), zoom lens and axicon are used together to generate different sources in the entrance pupil of the projection lens; the condenser design; and 1X relay with two cylinder lenses to achieve trapezoid intensity distribution in the scan direction. A demonstration simulation result is given, and the uniformity of the non-scan and scan direction reached 1.2% and 1.7% respectively under all illumination modes. The result showed good performance and the requirements of the lithography tools have been met.

There are many master pieces of the cultural heritage which can´t be correctly contemplated if daylight is not part of the exhibition environment, since they were made with the sun light as essential element of them. The Pórtico de la Gloria and the Cloister and paintings of Santa María de El Paular monastery are ones of these cases. The Pórtico de la Gloria (Gate of the Glory) is probably the most relevant masterpiece of the Santiago de Compostela cathedral. It is located at the narthex of the west gate. It is a masterwork of Romanesque sculpture built between 1168 and 1188 by Master Mateo. During the XVIII century a new Baroque façade was placed in front of it replacing the middle ages wall. Daylight entering through the windows of the facade makes possible to see the art work but the sun can generate serious problems since it heats the stone and evaporates the humidity. Thermal imagers have been used to test the thermal performance of the antireflection treatment located in the windows in the actual temperature of the stone sculptures. The cloister of the monastery of Santa María de El Paular, housed until the confiscation of 1835 a collection of 54 paintings of Vincente Carducho called Carthusian series. When in 2006 the restoration of the 52 still preserved paintings was completed, began a refurbishment of the cloister to return the paintings to their original place. We conducted a study of the incidence of the Sun in the cloister and how to avoid direct sunlight on Carducho's paintings.

When artificially lighting a restored painting, it is important to ensure consistency in the visual perception of original and restored areas. The current paper has worked out how chromatic difference varies between restored and original areas when modifying the lighting source. In colorimetry, metamerism is the matching of apparent color of objects with different spectral reflectance. The color of a surface is the value resulting from the product of the spectral reflectance curve of the material and the spectral emittance curve of the lighting source casting light on it. As a result, the color of surfaces depends on the lighting source used to illuminate them. This paper describes the work carried out to study the color difference between original and restored metameric areas of a painting with some chromatic reintegrated areas under different light sources. Firstly, based on an ultraviolet photograph from the painting, the areas with chromatic reintegration were identified. Secondly, using a PR-655 SpectraScan spectroradiometer as well as a calibrated lighting source and measuring geometry 0°/45°, the spectral reflectance was measured at four points of the same apparent color both next to original painting and in chromatic reintegrated areas. Finally, colorimetric calculations for a 2° CIE pattern observer were performed by using spectral measurements. The color difference between the original and the restored areas was estimated under different CIE pattern illuminants by using the CIE L*a*b color space.

It is demonstrated that, with a probability greater than zero, Einstein Local Hidden Variables can violate the Clauser, Horn, Shimony and Holt contrast. The method is based on Stochastic Physical Optics. The paper argues for a probabilistic loophole in CHSH experiments.

The vector Slepian multipole fields are recently published basis functions that are naturally suitable for approximating the focal electric field of a high numerical aperture lens, because their plane-wave amplitude spectrum shows an angular energy distribution that is highly confined to the spherical cap corresponding to the numerical aperture of the lens. Thus when solving inverse problems, no additional constraints are needed to ensure the directionality of the focused field, and the number of degrees of freedom can be reduced, as opposed to a representation using conventional multipole fields. In this paper we demonstrate the applicability of this new basis to an inverse problem of focusing where the three-dimensional intensity distribution is prescribed in some reasonably chosen volume around the focus. Using numerical optimization, an approximation of the focused electric field in terms of the vector Slepian multipole fields is obtained and the illuminating field is calculated in a straightforward way. Three examples from recent literature have been chosen to illustrate the method.

Polymers are often embedded with specific nanofillers such that the functional characteristics and properties of the resulting polymeric nanocomposite (PNC) are enhanced. The degree to which these enhancements can be achieved depends not only on the level of particle loading of nanofillers, but most importantly on the resulting dispersion profile achieved within the matrix. Agglomeration (often referred to as clustering) is a result of the mixing process and very much depends on the chemistry between the polymer and nanofiller. Depending on the PNC type, different mixing processes can be applied but the general consensus is that such processes are not repeatable themselves. Not only it is quite difficult to achieve the desired level of dispersion, but in addition there is a limited number of characterization tools that can be employed to routinely check the homogeneity achieved within a produced sample. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques are usually employed, but they are very time consuming, expensive, require special sample preparation and treatment, often produce results that are difficult to interpret and can only analyse very small areas of sample. This work reports on the adaptation and development and three optical techniques that are non-destructive, can accurately characterize the dispersion achieved as a result of the mixing process and can analyse larger material areas. The techniques reported are based on static and dynamic visible and infra-red light scattering.

The scattering of a spatially partially coherent wave from a one-dimensional statistically rough metallic surface is investigated. Assuming a Gaussian Schell-model form for the incident field autocorrelation function, a closed-form expression for the scattered field autocorrelation function is derived using the physical optics approximation (Kirchhoff approximation). Two forms of the solution are derived—one applicable to very rough surfaces and the other applicable to moderately rough surfaces. It is shown that for very rough surfaces, the solution, under certain circumstances, remains Gaussian Schell model as has been previously reported. As such, closed-form expressions for the angular coherence radius and angular scattering radius are derived. These expressions are, in general, complicated functions of both the source (size and coherence properties) and surface parameters (surface height standard deviation and correlation length). It is demonstrated that for many scenarios of interest, the angular coherence radius can be safely approximated as a function of just the source parameters and the angular scattering radius can be simplified to a function of just the surface parameters. For the moderately rough surface solution, the scattered field autocorrelation function is, in general, not Gaussian Schell model and it is therefore not possible to derive analytical forms for the angular coherence radius or angular scattering radius. Nonetheless, the form of the autocorrelation function is physically intuitive and is discussed in this work. To verify the presented theoretical analysis, wave optics simulation results are presented and compared to the predictions of the analytical models. This analysis is concluded with a discussion of future work.

In the previous paper the new scanning technique was proposed. The sample was illuminated by a focused laser beam with an optical vortex. The vortex was introduced to the laser beam by vortex lens. When shifting the vortex lens the optical vortex in the focused beam moves and scans the sample. In order to use this new scanning technique for microscopic imaging a method for the focused vortex beam phase reconstruction is necessary. In this paper a fast and accurate method for phase reconstruction of the focused vortex beam is investigated. It is shown that the propose method is accurate enough to explore even small optical vortex shifts inside the focused beam.

We report on diffraction efficiency considerations and experimental implementation of diffraction gratings by means of a phase-only spatial light modulator, parallel aligned (PAL) liquid crystal on silicon (LCoS) display. We present results of the implementation of continuous phase profiles for optimal efficiency, and their application for blazed gratings and diffractive lenses onto displays with reduced phase modulation range and also onto displays with large phase modulation range.

1/ ƒ fluctuations are widely observed in various physical, chemical and biomedical systems. T.Musha and G.Borbely took a laser light scattering experiments where 1/ƒ fluctuations directly represent the phonon energy fluctuations. Light scattering experiments for liquids shows that scatterers are not propagating ones such as phonons, but localized ones. Previously it was shown that hydrogen-bonded (H-bonded) liquids have structural heterogeneities of nanometer size (supramolecular ones) which can act as localized scatterers of a light beam. In this work fluctuations of light scattering in H-bonded liquids have been investigated. Power spectral density are describing by law S( f )~1/ƒ^α where index α depends on the type of liquid and molar ratio water/glycerol in solution. Two simple models which can explain this phenomenon are considered. The first model is a one-dimensional chain with nonlinear interaction between atoms, known as the Fermi-Pasta-Ulam system. In such a system there is a transfer of energy among modes, resulting in slow 1/ƒ fluctuations of total energy. In the second model we consider liquids structure by percolation theory which predicts an existence of weak supramolecular heterogeneities. Thus, intensity fluctuations might reflect fluctuations of the cross section scattering centers and/or fluctuations in the number of such centers in the volume of scattering.

The fast and accurate propagation of general optical fields in free space is still a challenging task. Most of the standard algorithms are either fast or accurate. In the paper we introduce without further physical approximations three new algorithms for the fast propagation of non-paraxial vectorial optical fields containing smooth but strong phase terms. Dependent on the shape of the smooth phase term different propagation operators are applied. The first method for the efficient propagation of fields, which are containing smooth spherical phase terms, is based on Mansuripur's extended Fresnel diffraction integral1 using fast Fourier Transformations. This concept is improved by Avoort's parabolic fitting technique2 and the parameter space, for which the extended Fresnel operator is numerically feasible, is discussed in detail. Furthermore we introduce the inversion of the extended Fresnel operator for the fast propagation of non-paraxial fields into the focal region. Secondly we discuss a new semi-analytical spectrum of plane waves (SPW) operator for the quick propagation of fields with smooth linear phase terms. The method is based on the analytical handling of the linear phase term and the lateral offset, which reduces the required computational window sizes in the target plane. Finally we generalize the semi-analytical SPW operator concept to universal shapes of smooth phases by de- composing non-paraxial fields into subfields with smooth linear phase terms. In the target plane, all propagated subfields are added coherently where the analytical known smooth linear phase terms are handled numerical efficient by a new inverse parabasal decomposition technique (PDT). Numerical results are presented for examples, demonstrating the efficiency and the accuracy of the three new propagation methods. All simulations were done with the optics software VirtualLab^TM.3

We present a theoretical analysis of the closed-aperture Gaussian beam Z-scan for nonlinear optical materials with both saturable absorption and simultaneous third- and fifth-order nonlinear refraction. We formulate a theoretical expression for the Z-scan transmittance by means of the Adomian’s decomposition method and the thin film approximation. It is applied to the experimental characterization of the nonlinear optical properties of a semiconductor CdSe quantum dot-polymer nanocomposite film. We show that measured results of the open- and closed-aperture Z-scan transmittances of the nanocomposite film are well explained by the theoretical model.

This article introduces an efficient tilt operator for harmonic fields. In optical modeling and design, a field tilting operation is often needed, e.g., the propagation of a harmonic field between non-parallel planes, since most of the existing propagation operators only deal with the case of propagation between parallel planes. Such operator enables the modeling of various optical components, like the case of prisms and tolerancing with tilted components. The tilt operator is a rigorous method to calculate vectorial harmonic fields on tilted planes. The theory applies a non-equidistant sampling in the k-space of the field before rotation in order to obtain an equidistant sampling of the rotated field. Different interpolation techniques are employed for the non-equidistant sampling in the k-space of the initial field and their performances are evaluated. Besides the tilt operator, the propagation method of harmonic fields through planar interface is proposed as well. The application of both methods makes it possible to model a sequence of tilted optical interfaces, e.g., prisms. At the end of this article, a dispersive prisms example is presented. All simulations are done with the optics software VirtualLab^TM.1

Projection lithography at wavelengths in the extreme ultraviolet spectral range between 5 and 20 nm (EUV-lithography) employs reflective optical components including masks. This article applies rigorous electromagnetic field (EMF) simulation in combination with accurate projection image modeling to explore the impact of typical mask geometry parameters on the characteristics of lithographic processes. This includes telecentricity and shadowing effects resulting from the off-axis illumination in EUV systems and mask induced aberration{like effects. The importance of these effects for several alternative mask concepts including attenuated and alternating phase shift masks is investigated.

Typical focus sensors in conventional integrated circuit lithographic equipment have long been known to exhibit errors due to the nature of patterns printed on the wafer. One such error can be characterized as being derived from thin film effects where the derivative of the phase on reflection by the wafer introduces a shift in the beam that is basically identical to a shift that would be generated by a change in wafer height. In this paper we present a theoretical investigation into the nature and magnitude of the focus offset produced by this wafer effect under current typical process parameters.

In situ aberration measurement of projection objective is necessary for lithography tool. For 90 nm technology node, aberration measurement accuracy of 1 nm rms is required. In this paper, a high numerical aperture Hartmann wavefront sensor with pinhole array extended source is proposed. The sensor uses source mask with pinhole array on the object plane of projection objective to filter the aberration of illumination optics as well as provide sufficient power required by Hartmann sensor. A coupling objective, which is installed at the confocal position of the projection objective under test, transforms the high numerical aperture spherical waves to plane waves. A null mask, which has similar structure with source mask, can be inserted at the image plane of projection objective. With the null mask installed and source mask uninstalled, the systematic measurement errors mainly caused by coupling objective can be calibrated by the relative measurement process. In this paper, some design considerations of source mask and null mask are presented. Using partial coherent light propagation and Fourier optics theory, the proper spacing and quantity of pinholes on either source mask or null mask are calculated. Finally, measurement accuracy of the sensor is evaluated using three-dimensional electromagnetic simulation of 193nm high numerical aperture converging beam propagation through pinhole with different pinhole parameters. Simulation results show that, measurement accuracy of the sensor is better than 0.5 nm rms in theory after systematic errors calibration.

An in-situ aberration measurement technique based on aerial image with optimized source is proposed. A linear relationship between aerial image and Zernike coefficients is established by principle component analysis and regression analysis. The linear relationship is used to extract aberrations. The impacts of the source on regression matrix character and the Zernike aberrations measurement accuracy are analyzed. An evaluation function for the aberrations measurement accuracy is introduced to optimize the source. Parameters of the source are optimized by the evaluation function using the simulators Dr.LiTHO and PROLITH. Then the optimized source parameters are adopted in our method. Compared with the previous aberration measurement technique based on principal component analysis of aerial image (AMAI-PCA), the number terms of Zernike coefficients that can be measured are increased from 7 to 27, and the Zernike aberrations measurement accuracy is improved by more than 20%.

A novel technique (AMAI-Quad) for aberration extraction of lithographic projection based on quadratic relationship model between aerial-image intensity distribution and Zernike coefficients is proposed. Zernike coefficients in this case represent the imaging quality of lithographic projection lens in a semiconductor wafer exposure scanner. The proposed method uses principal component analysis and multivariate linear regression analysis for model generation. This quadratic model is then used to extract Zernike coefficients by nonlinear least-squares. Compared with earlier techniques, based on a linear relationship between Zernike coefficients and aerial images, proposed by Duan, the new method can extend the types of aberrations measured. The application of AMAI-Quad to computed images of lithography simulators PROLITH and Dr.LiTHO for randomly varied wavefront aberrations within a range of 50mλ demonstrated an accuracy improvement of 30%.

A method for generating beams with arbitrary polarization and shape is proposed. Our design requires the use of a Mach-Zehnder set-up combined with translucent liquid crystal displays in each arm of the interferometer; in this way, independent manipulation of each transverse beam components is possible. The target of this communication is to develop a numerical procedure for calculating the holograms required for dynamically encode any amplitude value and polarization state in each point of the wavefront. Several examples demonstrating the capabilities of the method are provided.

The characterization of nanostructured surfaces by scatterometry is an established method in wafer metrology. From measured light diffraction patterns, critical dimensions (CD) of surface profiles are determined, i.e., line widths, heights and other profile properties in the sub-micrometer range. As structures become smaller and smaller, shorter wavelengths like extreme ultraviolet (EUV) at 13.5 nm ensure a sufficient sensitivity of the measured light diffraction pattern with regard to the structure details. Obviously, the impact of structure roughness with amplitudes in the range of a few nanometers can no longer be neglected in the course of the profile reconstruction. To model line roughness, i.e., line edge (LER) and line width (LWR) roughness, a large number of finite element (FEM) simulations are performed for domains with large periods, each containing many pairs of line and space with stochastically chosen widths. These structures are composed of TaN -absorber lines with an underlying MoSi -multilayer stack representing a typical EUV mask. The resulting mean efficiencies and the variances of the efficiencies in dependence on different degrees of roughness are calculated. A systematic decrease of the mean efficiencies for higher diffraction orders along with increasing variances are observed. In particular, we obtain a simple analytical expression for the bias in the mean efficiencies and the additional uncertainty contribution stemming from the presence of LER and/or LWR. As a consequence, the bias has to be included into the model to provide accurate values for the reconstructed critical profile parameters. The sensitivity of the reconstructed CDs in respect of roughness is demonstrated by using numerous LER/LWR perturbed datasets of efficiencies as input data for the reconstructions. Finally, the reconstructed critical dimensions are significantly improved toward the nominal values if the scattering efficiencies are bias-corrected.