Proceedings Volume 6289

Novel Optical Systems Design and Optimization IX

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Proceedings Volume 6289

Novel Optical Systems Design and Optimization IX

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Volume Details

Date Published: 5 September 2006
Contents: 8 Sessions, 44 Papers, 0 Presentations
Conference: SPIE Optics + Photonics 2006
Volume Number: 6289

Table of Contents

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Table of Contents

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  • Special Session: Youth Optics Education
  • Materials
  • Structures in Photonics
  • Geometrical Optics and Lens Design
  • Alignment
  • Diffraction and Illumination
  • Optical Modeling
  • Poster Session
Special Session: Youth Optics Education
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Successfully using optical components and systems in novel ways during educational outreach programs for K-12 grades
Much work has been done in efforts to reach students in the K-12 grades to encourage them to learn about optics and related sciences and technologies. One goal of these efforts is to develop the future optical scientists and engineers to carry on the work of this and related societies. One main obstacle is to create low costs novel and effective hands-on optical components and systems for these students to use and from which to get excited. Students at different grade levels and abilities are receptive to different kinds of components and systems and this must be taken into account when preparing for outreach programs. There are, however, some guiding principles which can be used throughout the various levels, including making sure the components and systems are good examples and not marginal. Small telescopes or microscopes that use poor quality optics which provide poor quality images do more to discourage young students from going into the sciences than if they never had the experience at all. Some examples of both poor and good quality optical components and systems that will be described and demonstrated include: lenses, telescopes, microscopes, diffraction gratings, Kaleidoscopes, Fresnel Lenses, polarization filters and liquid crystals. The figures in this paper are in color and best viewed on-line or printed with a good color printer.
Materials
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The origins of fiber print-through in lightweight composite optics
NASA and the U. S. Air Force are looking to improve space borne telescopes by reducing mirror weight. One commonly attempted solution is to fabricate Carbon Fiber Reinforced Polymer (CFRP) mirrors using a mirror replication technique. These attempts have been hindered by the well-known fiber print-through phenomenon. The resulting sinusoidal surface distortion is fiber print-through, where chemical and thermal shrinkage during cure have been hypothesized to be the dominant causes. Although successful mitigation of fiber print-through via a polished resin layer method has been proven, an additional resin layer reduces the heat transfer through the mirror thickness that would be necessary for high-energy laser applications and also carries structural disadvantages. The purpose of this research was to quantify the dominating causes of fiber print-through and its contribution to the total surface roughness of a composite (where total roughness includes the elements of print-through and other surface anomalies that contribute to diffuse reflection). In order to quantify the causes of fiber print-through, a number of CFRP samples with varying fiber type, diameter and cure schemes were fabricated. The dominating causes of fiber print-through were then found by measuring fiber print-through, via microscopic interferometry, and determining which variables had the greatest influence on print-through.
Space qualification of silicon carbide for mirror applications: progress and future objectives
Production of optical silicon carbide (SiC) for mirror applications continues to evolve and there are renewed plans to use this material in future space-based systems. While SiC has the potential for rapid and cost-effective manufacturing of large, lightweight, athermal optical systems, this material's use in mirror applications is relatively new and has limited flight heritage. This combination of drivers stresses the necessity for a space qualification program for this material. Successful space qualification will require independent collaboration to absorb the high cost of executing this program while taking advantage of each contributing group's laboratory expertise to develop a comprehensive SiC database. This paper provides an overview of the trends and progress in the production of SiC, and identifies future objectives such as non-destructive evaluation and space-effects modeling to ensure proper implementation of this material into future space-based systems.
Key product development based on cyclo olefin polymer for LCD-TV
Yuichiro Konishi, Masahi Kobayashi, Kouhei Arakawa
Cyclo Olefin Polymer (COP), which was developed by Zeon Corporation, is well known and used as an optical plastic in optical markets, having unique properties such as high light transmission, low water absorption, low birefringence etc. Optes Inc, who is ZEON CORPORATION's affiliate optical parts manufacturer, has succeeded in the development of high performance optical base films. These are used for retardation and polarizing films in LCD's (Liquid Crystal Displays), made from Cyclo Olefin Polymer with own film extrusion technologies. The Optical base film developed by Optes Inc has superior properties compared with those of existing products such as polycarbonate (PC), polyethylene terephthalate (PET) and Triacetate Cellulose (TAC) base in terms of low birefringence, high optical isotropy and high dimensional stability under high humidity and temperature conditions.
Optomechanical considerations for the VISAR diagnostic at the National Ignition Facility (NIF)
Morris I. Kaufman, John R. Celeste, Brent C. Frogget, et al.
The National Ignition Facility (NIF) requires optical diagnostics for measuring shock velocities in shock physics experiments. The velocity interferometer for any reflector measures shock velocities at a location remote to the NIF target chamber. Our team designed two systems, one for a polar port orientation, and the other to accommodate two equatorial ports. The polar-oriented design requires a 48-m optical relay to move the light from inside the target chamber to a separately housed measurement and laser illumination station. The currently operational equatorial design requires a much shorter relay of 21 m. Both designs posed significant optomechanical challenges due to the long optical path length, large quantity of optical elements, and stringent NIF requirements. System design had to tightly control the use of lubricants and materials, especially those inside the vacuum chamber; tolerate earthquakes and radiation; and consider numerous other tolerance, alignment, and steering adjustment issues. To ensure compliance with NIF performance requirements, we conducted a finite element analysis.
Space imaging measurement system based on fixed lens and moving detector
Akira Akiyama, Minoru Doshida, Eiichiro Mutoh, et al.
We have developed the Space Imaging Measurement System based on the fixed lens and fast moving detector to the control of the autonomous ground vehicle. The space measurement is the most important task in the development of the autonomous ground vehicle. In this study we move the detector back and forth along the optical axis at the fast rate to measure the three-dimensional image data. This system is just appropriate to the autonomous ground vehicle because this system does not send out any optical energy to measure the distance and keep the safety. And we use the digital camera of the visible ray range. Therefore it gives us the cost reduction of the three-dimensional image data acquisition with respect to the imaging laser system. We can combine many pieces of the narrow space imaging measurement data to construct the wide range three-dimensional data. This gives us the improvement of the image recognition with respect to the object space. To develop the fast movement of the detector, we build the counter mass balance in the mechanical crank system of the Space Imaging Measurement System. And then we set up the duct to prevent the optical noise due to the ray not coming through lens. The object distance is derived from the focus distance which related to the best focused image data. The best focused image data is selected from the image of the maximum standard deviation in the standard deviations of series images.
Structures in Photonics
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Liquid crystal based active optics
Brett E. Bagwell, David V. Wick, Robert Batchko, et al.
Liquid crystal spatial light modulators, lenses, and bandpass filters are becoming increasingly capable as material and electronics development continues to improve device performance and reduce fabrication costs. These devices are being utilized in a number of imaging applications in order to improve the performance and flexibility of the system while simultaneously reducing the size and weight compared to a conventional lens. We will present recent progress at Sandia National Laboratories in developing foveated imaging, active optical (aka nonmechanical) zoom, and enhanced multi-spectral imaging systems using liquid crystal devices.
New approach to image amplification based on an optically pumped multi-core optical fiber
Arturo Chavez-Pirson, Bor-Chyuan Hwang, Dan Nguyen, et al.
This paper describes a new approach to amplify optical images by using optically pumped doped cores in a multi-core optical fiber structure. This approach combines the high gain and high efficiency properties of cladding pumped optical amplifiers with the imaging properties of coherent fiber bundles. The individual cores correspond to the pixels in the image amplifier. We have demonstrated 3x3 arrays in an ytterbium-doped phosphate fiber energized by one multimode semiconductor diode. Each pixel is capable of high gain (> 20 dB), low noise, and large acceptance angle (>12 degrees). We expect our glass and preform fabrication method to scale to over 100 pixels. The amplified image can preserve coherence (phase and wavelength) - or scramble the coherence depending on the design of the cores. This image amplifier is an enabling technology for any type of imaging system that is photon-starved and requires a compact and low noise image amplifier.
Tilted logpile photonic crystals using the LIGA technique
J. D. Williams, C. Arrington, W. C. Sweatt, et al.
The LIGA microfabrication technique offers a unique method for fabricating 3-dimensional photonic lattices based on the Iowa State "logpile" structure. These structures represent the [111] orientation of the [100] logpile structures previously demonstrated by Sandia National Laboratories. The novelty to this approach is the single step process that does not require any alignment. The mask and substrate are fixed to one another and exposed twice from different angles using a synchrotron light source. The first exposure patterns the resist at an angle of 45 degrees normal to the substrate with a rotation of 8 degrees. The second exposure requires a 180 degree rotation about the normal of the mask and substrate. The resulting pattern is a vertically oriented logpile pattern that is rotated slightly off axis. The exposed PMMA is developed in a single step to produce an inverse lattice structure. This mold is filled with electroplated gold and stripped away to create a usable gold photonic crystal. Tilted logpiles demonstrate band characteristics very similar to those observed from [100] logpiles. Reflectivity tests show a band edge around 5 μm and compare well with numerical simulations.
Design and analysis of coupled-resonator optical waveguides (CROWs) using a hardware-based simulation platform
Shouyuan Shi, James P. Durbano, Ahmed S. Sharkawy, et al.
The coupled-resonator optical waveguide (CROW) is a new type of waveguide in which light propagates due to the coupling between adjacent resonators. CROWs have attracted significant interest within the photonics community because of their ability to manipulate light and provide better control over the optical dispersion characteristics on a microscopic scale. Furthermore, the weak coupling between adjacent, high-Q resonator cavities can significantly reduce the group velocity of light in such structures and may potentially lead to applications in delaying, storing, and buffering of optical pulses, as well as laser systems. Unfortunately, modeling such devices is complex and simplified models suitable for simulations do not truly reflect the operation of the device. Thus, a rigorous numerical electromagnetic analysis is needed to address various issues such as propagation losses, speed, and the efficiency of coupling light into and out of these devices. Further, such analysis requires support for very large problem sizes, too large to be practically simulated using standard software tools, in order to support multiple rings in the structure. To this end, we have developed a novel, hardware-based platform to analyze CROW structures. In this paper, we describe this platform, which has performance comparable to a 100-node PC cluster, and analyze several CROW structures for optical delay applications.
The effect of fabrication parameters on the cleaving of microstructured polymer optical fibers
Susan Law, Geoffrey Barton, Martijn van Eijkelenborg, et al.
A key step towards the commercialization of microstructured polymer optical fibers is the ability to cleave and splice them. The cleaving of polymer optical fiber (whether by cutting or fracture) depends upon the mechanical properties of the material. These in turn depend on the conditions under which the fiber is drawn from the preform. The relationship between fiber draw conditions, mechanical properties of the drawn fiber and the ability to cut the heated fiber with a hot razor blade has been investigated for PMMA fibers of varying hole structure. Differential scanning calorimetry measurements indicate that the type of PMMA used exhibits two 'relaxations' with inflexion points at 115±3oC and 80±2oC respectively, independent of draw conditions. The first of these is in the range expected for the α-relaxation. The origin of the second is unknown. Dynamic mechanical analysis of fiber samples indicates that the temperature dependence of the elastic and loss moduli of the fiber vary significantly with draw conditions. The end-face produced by cutting with a razor blade also varies with draw conditions. Fiber drawn under high tension splinters during cutting and fiber drawn under low tension undergoes ductile deformation and fracture. However for intermediate draw conditions the fiber can be cleanly cut with a razor blade at a temperature of 80±10oC.
Geometrical Optics and Lens Design
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Geometrical optics: some applications of the law of intensity
Geometrical optics is commonly associated with the ray-like properties of light, such as, law of reflection, Snell's law, ray tracing, the optical path length and phase. The geometrical optics law of intensity and the optical wavefront are also well known, but are perhaps less used as a basis for optical design than ray tracing. This paper will first review how the geometrical optics law of intensity leads to the invariance of the product of the intensity of light times an element of area along a bundle of rays. Then, we will discuss how the geometrical optics law of intensity provides a good foundation for understanding not only nonimaging optics through direct ways to design optical systems for prescribed illumination requirements but also imaging applications through a complete understanding of the differential geometry of the optical wavefront and the caustic surfaces.
Optics to rectify CORONA panoramic photographs for map making
Robert S. Hilbert
In the 1960's, accurate maps of the United States were available to all, from the U.S. Government, but maps of the Soviet Union were not, and in fact were classified. Maps of the Soviet Union were needed by the U.S. Government, including for U.S. targeting of Soviet ICBM sites, and for negotiating the SALT ICBM disarmament treaty. Although mapping cameras were historically frame cameras with low distortion, the CORONA panoramic film coverage was used to identify any ICBM sites. If distortion-free photographs could be produced from this inherently distorted panoramic material, accurate maps could be produced that would be valuable. Use of the stereo photographs from CORONA, for developing accurate topographical maps, was the mission of Itek's Gamma Rectifier. Bob Shannon's department at Itek was responsible for designing the optics for the Gamma Rectifier. He assigned the design to the author. The optical requirements of this system are described along with the optical design solution, which allowed the inherent panoramic distortion of the original photographs to be "rectified" to a very high level of accuracy, in enlarged photographs. These rectifiers were used three shifts a day, for over a decade, and produced the most accurate maps of the earth's surface, that existed at that time. The results facilitated the success of the Strategic Arms Limitation Talks (SALT) Treaty signed by the US and the Soviet Union in 1972, which were verified by "national means of verification" (i.e. space reconnaissance).
Low-birefringence lens design for polarization sensitive optical systems
Polarization sensitive optical systems may contain optical components that are considered non-polarization optics, such as multi-element collection/illumination lenses, relay lenses and focusing/imaging lenses. With conventional optical design and optomechanical software tools to design these lenses, special consideration is required in choosing glass materials, coatings, and optomechanical design for low intrinsic and stress-induced birefringence and thermal stability. Optical design parameters are discussed to achieve overall minimum birefringence, by optimizing with low intrinsic birefringence glass material, applying phase-controlled (balanced) coating design, and low stress mechanical design approaches. Also discussed are options for matching thermal expansion coefficient (CTE) of the system components. Analysis on transmissive phase retardation of a microbjective at its pupil plane, as well as its birefringence measurement data, will be presented. It is shown that it is critical to design and optimize at multiple positions across the lens pupil to achieve better polarization performance.
Low vision goggles: optical design studies
Ofer Levy, Boris Apter, Uzi Efron
Low Vision (LV) due to Age Related Macular Degeneration (AMD), Glaucoma or Retinitis Pigmentosa (RP) is a growing problem, which will affect more than 15 million people in the U.S alone in 2010. Low Vision Aid Goggles (LVG) have been under development at Ben-Gurion University and the Holon Institute of Technology. The device is based on a unique Image Transceiver Device (ITD), combining both functions of imaging and Display in a single chip. Using the ITD-based goggles, specifically designed for the visually impaired, our aim is to develop a head-mounted device that will allow the capture of the ambient scenery, perform the necessary image enhancement and processing, and re-direct it to the healthy part of the patient's retina. This design methodology will allow the Goggles to be mobile, multi-task and environmental-adaptive. In this paper we present the optical design considerations of the Goggles, including a preliminary performance analysis. Common vision deficiencies of LV patients are usually divided into two main categories: peripheral vision loss (PVL) and central vision loss (CVL), each requiring different Goggles design. A set of design principles had been defined for each category. Four main optical designs are presented and compared according to the design principles. Each of the designs is presented in two main optical configurations: See-through system and Video imaging system. The use of a full-color ITD-Based Goggles is also discussed.
Alignment
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Versatile autostigmatic microscope
An autostigmatic microscope is described and its uses explained. Then an adaptation of the original instrument is described that uses current technological advances in laser diodes and video displays to turn an old workhorse into a versatile optical test and alignment device. This paper illustrates applications that make use of the capabilities of the modern autostigmatic microscope outside the field of aligning optical systems such as using it as an electronic autocollimator, a check on the centration of the axes of molded optics and the measurement of the runout and wobble of precision spindles such as air bearings.
Additional algorithms for sensor chip alignment to blind datums
Gary B. Hughes
Alignment of the sensor focal plane array (FPA) to optical components is a critical design feature. Imaging system designs include reference datums that provide the basis for manufacturing alignment in each sub-assembly. Measurement of z and parallelism positioning can be problematic, since the relevant datum features are often beneath the mounting platform and are obscured to the measurement system. General algorithms for determining sensor chip alignment when datum features are inaccessible to the measurement system have been developed. Pre-characterization measurements of datum surfaces are stored for later use during alignment measurement to determine datum locations. The algorithms are useful for post-mounting alignment measurement, and can also be used for active manufacturing alignment. This paper presents additional algorithms that are useful for active alignment, including methods for determining rotation axes on the aligner-bonder system and for determining actuator motions to bring the FPA into alignment with datums. The algorithms have been successfully implemented for ultra-precision, active manufacturing alignment and post-alignment measurement of infrared imaging systems.
A multidisciplinary design and optimization methodology for the Adaptive Scanning Optical Microscope (ASOM)
Dynamic optical systems that include active and adaptive optical elements allow the pursuit of scientific investigations, military applications, and medical diagnostics that are well beyond the theoretical capabilities of a purely static optical design. However, the design of such systems is particularly challenging because of the large number of design variables, multiple operating configurations, and the need to coordinate different simulation tools (e.g. optical ray tracing, finite element analysis, dynamic simulations, etc.) during the design and optimization process. This paper presents a design methodology to facilitate the design and optimization of our novel Adaptive Scanning Optical Microscope (ASOM), which includes a fast steering mirror (FSM), a custom designed scanner lens, and a MEMS deformable mirror (DM) to effectively enlarge the field of view in optical microscopy. An "all at once" formulation of the optimization problem using a traditional construction of the merit function proved inadequate. Instead, our approach first partitions the design problem into manageable sub-problems and uses the Collaborative Optimization (CO) framework to coordinate the system wide optimization of the sub-problems while maintaining a physically consistent solution between the simulation codes. Next, we demonstrate the efficacy of the approach by presenting two ASOM designs that were generated using this methodology. The first design is based on high fidelity simulations and the second lower cost version has been constructed and tested in our laboratory using a 32 actuator deformable mirror. We conclude by summarizing our experiences and discussing how the approach could be generalized to other optical system design challenges.
Diffraction and Illumination
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Understanding diffraction effects in novel systems containing nanostructures
James E. Harvey, Andrey Krywonos
The recent revelation that diffracted radiance is the fundamental quantity predicted by scalar diffraction theory, combined with the observation that radiance (not irradiance or intensity) is shift-invariant in direction cosine space, has lead to the development of a generalized linear systems formulation of non-paraxial scalar diffraction theory. Thus simple Fourier techniques can now be used to predict a variety of wide-angle diffraction phenomena. These include: (1) the redistribution of radiant energy from evanescent diffracted orders to propagating ones, (2) the angular broadening (and apparent shifting) of wide-angle diffracted orders, and (3) diffraction efficiencies predicted with an accuracy usually thought to require rigorous electromagnetic theory. In addition, this new insight and understanding has led to an empirically modified Brckmann-Kirchhoff surface scatter model that is more accurate than the classical Beckmann-Kirchhoff theory in predicting scatter effects at large incident and scattered angles, without the smooth-surface limitation of the Rayleigh-Rice vector perturbation surface scatter theory. This new understanding of non-paraxial diffraction phenomena is becoming increasingly important in the design and analysis of novel optical systems containing nano-structures.
Numerical experiments in modeling diffraction phenomena with Monte Carlo ray tracing
Monte Carlo ray tracing programs routinely simulate the phenomena of reflection, refraction, and scattering by redirecting rays when they intersect a surface. We desire to simulate the diffraction of light by apertures, a wave phenomenon, by a method that melds easily into ray tracing algorithms. The proposed method redirects rays in random directions according to a Gaussian probability distribution. The width of this distribution varies inversely with distance of the ray intersection point from the edge of the aperture, and is derived from the Heisenberg uncertainty relation. Previous results have shown good agreement of incoherent summing of rays traced as compared with results obtained by integral methods. Here we present the coherent summation of rays, showing results that substantially agree with those obtained by integral methods including the fringes that result from interference of coherent light.
Robust error estimation in optical analysis software using subdivided and recombined ray traces
It is often necessary in optical analysis software to trace millions of rays in order to determine flux transfer, color chromaticity, and the distributions of intensity, irradiance, or radiance onto one or more targets. The key question of "have I traced enough rays?" cannot be answered unless the statistical error in the final simulated result is below some measurement criteria; for instance, if you are to determine irradiance uniformity to less than 1%, having a 2% statistical error across the target will wash out what you are trying to analyze. Some optical analysis software packages do not provide error estimation methods, while others use error estimation algorithms having assumptions that are not valid for all cases. This paper describes how subdividing and recombining raytraces provides a robust method for estimating error. We will show that this error estimation technique can be used with most optical analysis packages and we will compare it with algorithms employed currently. Example systems will be analyzed and presented.
Illumination optimization for optical semiconductor metrology
Bryan M. Barnes, Lowell P. Howard, Richard M. Silver
Uniform sample illumination via Kohler illumination is achieved by establishing a pair of conjugate focal planes; a light source is focused onto the condenser lens back focal plane while the image of the field aperture is focused at the plane of the specimen. Placement accuracy of these elements along the optical axis will determine the quality of the spatial homogeneity of the illumination in the sample plane. Imaging is therefore inherently sensitive to the tolerance of this alignment. Measuring three-dimensional features on semiconductor wafers has demonstrated an additional requirement for angular illumination homogeneity, as this is critical for robust matching between experimental results and numerically modeled results. We outline our techniques for aligning a custom-built microscope that features a 12 mm diameter conjugate back focal plane, beginning with the establishment of an optical axis based upon the objective lens. We then illustrate the techniques used to establish the quantitative degree of spatial and angular homogeneity through quantifying the resultant illumination while apertures are scanned across this conjugate back focal plane. Examples of the correlation between homogeneity and optical metrology are provided.
Optical illumination and critical dimension analysis using the through-focus focus metric method
In this paper we present recent developments in optical microscope image analysis using both, best focus optical image as well as those images conventionally considered out of focus for metrology applications. Depending on the type of analysis, considerable information can be deduced with the additional use of the out of focus optical images. One method for analyzing the complete set of images is to calculate the total "edge slope" from an image, as the target is moved through-focus. A plot of the sum of the mean square slope is defined as the through-focus focus metric. We present a unique method for evaluating the angular illumination homogeneity in an optical microscope (with Koehler illumination configuration), based on the through-focus focus metric approach. Both theoretical simulations and experimental results are presented to demonstrate this approach. We present a second application based on the through-focus focus metric method for evaluating critical dimensions (CD) with demonstrated nanometer sensitivity for both experimental and optical simulations. An additional approach to analyzing the complete set of images is to assemble or align the through focus image intensity profiles such that the x-axis represents the position on the target, the y-axis represents the focus (or defocus) position of the target with respect to the lens and the z-axis represents the image intensity. This two-dimensional image is referred to as the through focus image map. Using recent simulation results we apply the through focus image map to CD and overlay analysis and demonstrate nanometer sensitivity in the theoretical results.
Optical Modeling
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Imaging at low Fresnel number: some challenges and applications
A brief review of the main effects associated with low Fresnel number N in optical system with circular and elliptical pupil shape under uniform and Gaussian illumination is given. The attention is drawn more specifically on the focal shift and its impact on static resolution and depth-of-focus. This is illustrated by several examples of imaging systems in the terahertz spectral region, where diffraction effect tends to dominate. Recently developed in the mm-wave range, compact passive THz imagers often require large depth-of-field at a nominal distance of several meters leading to a value of the Fresnel number N<1. Typically far-infrared and submm space-based astronomical instrumentation with or without direct spatial sampling (i.e. Nyquist or better) requires compactness inducing small internal pupil size leading to N<5 across a larger spectral bandwidth, putting restrictive constraints on the design and/or the operation of the imaging system. Some application-specific design guidelines are also derived from the good agreement found between optical modeling and experimental measurements on prototypes. Finally mention is made of shorter wavelength optical instruments or devices in which similar effect can occur showing the general nature of the phenomenon.
Mechanically assisted liquid lens zoom system for mobile phone cameras
Camera systems with small form factor are an integral part of today's mobile phones which recently feature auto focus functionality. Ready to market solutions without moving parts have been developed by using the electrowetting technology. Besides virtually no deterioration, easy control electronics and simple and therefore cost-effective fabrication, this type of liquid lenses enables extremely fast settling times compared to mechanical approaches. As a next evolutionary step mobile phone cameras will be equipped with zoom functionality. We present first order considerations for the optical design of a miniaturized zoom system based on liquid-lenses and compare it to its mechanical counterpart. We propose a design of a zoom lens with a zoom factor of 2.5 considering state-of-the-art commercially available liquid lens products. The lens possesses auto focus capability and is based on liquid lenses and one additional mechanical actuator. The combination of liquid lenses and a single mechanical actuator enables extremely short settling times of about 20ms for the auto focus and a simplified mechanical system design leading to lower production cost and longer life time. The camera system has a mechanical outline of 24mm in length and 8mm in diameter. The lens with f/# 3.5 provides market relevant optical performance and is designed for an image circle of 6.25mm (1/2.8" format sensor).
Dynamic optics for digital projection applications
We present a projection optical system incoporating a dynamic optical element and we outline some of its potentional applications for digital projections. We describe experiments undertaken to validate a variety of these applications, in particular: change of focus without mechanical motion of the focus group; correction of chromatic aberration; and correction of a variety of other aberrations. We conclude that dynamic optical element can be used to improve the quality of image achieved from a very simple digital projection optical system.
Poster Session
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Optical system for ultrathin projection TV
A rear projection optical system that performs enlarged projection from the primary image plane on the reduction side to the second image plane on the enlargement side without forming an intermediate real image has: a refractive lens group including an aperture; a bending mirror that rotates the optical axis for the optical system after said bending mirror by approximately 90 degrees; for performing enlargement projection from a primary image surface located on the reduction side to a secondary image surface located on the enlargement side has, from the secondary image surface side, at least two reflective surfaces. Of the first and the second reflective surface counted from the secondary image surface side, at least one has a negative optical power. At least one Fresnel reflective surface having a positive or negative optical power is disposed within the entire projection optical system.
Stability analysis of optomechanical system in SGII facility
In SHENGUANGII (SGII) facility, the optomechanical system is the optics and optomechanical support hardware which necessary to transport the laser beams through the system from the laser drivers to the target. In order to satisfy the laser beam accurately positioned, the system must provide a stable platform for the optical elements before and during a shot. While the ambient vibration such as thermal impact, ground borne, acoustic and noise usually disturbs the stability of the system when the facility on working. This paper put forward the concept of system stability, and the method of test and vibration isolation control presented. The finite element analysis has been used to analysis the stability of the typical system. Base on the result, the working performance of system can be confirm, even the stability of SGII facility in future long-time work can be estimated, also the key points of stability design for the important parts and system can be suggested. It offers design guidance on the next upgrade of SG facility design and guarantee for the procedure of facility's precision. This information also can be used to the structure and system of the similar facilities.
Enhancement of the optical performances for the LED backlight systems with a novel lens cap
A novel dual-cone-shaped side-emitting lens cap for High Brightness Light Emitting Diodes (HB-LEDs) is proposed for improving brightness and high uniformity of the direct LED acklight Units (BLUs) for large area LCD-TVs. Combining the designed lens cap with red, green and blue (RGB) chips on a Metal Core Printed Circuit Board (MCPCB), the LED module with the proposed cap is able to provide a compact white light source with unique features such as instant color variability and lower power usage, etc. The dual-cone-shaped of the proposed lens cap is designed to emitting most of the light rays to the sides, only a small portion of light upward along the optical axis of the lens, providing a uniform luminance distribution and the high brightness on the backlight. In addition, a small, half-circle eflective surface is designed and upon the proposed LED module about 10mm, the surfaces of which are attached with reflective films to increase the level of light mixing in the larger, global reflector optical box. With the structure of the LED module well designed, the LED backlight Module would design for the large area LCD-TV using the fewer number of LEDs and also have low power consumption. The results indeed identify the attributes of the BLU, which make it possible to achieve excellent backlight performance using a direct illumination approach from the light source of "Dual-Cone-Shaped Side-Emitting Lens Cap of LEDs".
A study on the optimization methods for optomechanical alignment
Ming-Ta Yu, Tsung-Yin Lin, Yi-You Li, et al.
The alignment for optomechanical components is important in designing and manufacturing optical systems. This study uses optical fibers for example to find suitable optimization strategies for optomechanical alignment. The core diameter of the single-mode fiber is about 6μm to 9μm. Any slight misalignment or deformation of the optical mechanism will cause signification optical losses during connections. The alignment methods can be divided into passive and active ones. In the passive alignment, optical connectors, ferrules, and sleeves are used to align two optical fibers. In the active alignment, the best connection position with minimum connection losses must be found, and users usually take a lot of effort to do this. This study uses different optimum methodologies: non-gradient-based, gradient-based, and Hessian-based methods, to find the optimum position. The non-gradient-based method has low accuracy and the efficiency cannot be increased. The gradient-based methods seem to have better efficiency to find the optimum position because it uses gradient information to calculate the search direction in every iteration. Finally for the Hessian-based methods, it is found that the advantage of using Hessian matrix is not obvious because the light intensity distribution is similar to the Gaussian distribution.
Optimization design of large octagonal Nd:glass support system
Wavefront distortion induced by structure design must be minished to raise the quality of output beam in ICF facility. The support system of large octagonal Nd:glass in main amplifiers of SG-II is optimized with finite element analysis software ANSYS, and wavefront distortion in aperture of amplifier is calculated with Zernike polynomials fitting in different parameters combination. The transmission wavefront distortion induced by optimal support system is less than tenth wavelength and meets the requirement of system.
Compound telescope
Zhenwu Lu, Nan Zhang, Hua Liu, et al.
Compound telescope is a new type of space optical system. It uses the concept of compound eyes and the property of diffractive lens. With the help of diffractive lens, the diffractive optical system could become lighter weight, lower cost, and looser tolerance. And with the help of compound-eye configuration, the field of view is expanded. A design example of compound diffractive optical system is given. It is composed of many diffractive telescope of F/4, 200mm aperture, 0.1 degrees field of view. It is shown that the whole system can approximately attain the diffraction limit over wide field of view.
Near field analysis of CSG and BSG combined element under high power laser condition
In high power laser system, it is of great interest to combine two or more diffractive structures, in particular, the beam-sampling gratings (BSG) and the color separation gratings (CSG), onto one element. However, the combined element with diffractive structure on both surfaces, may cause serious laser induced damage to the element itself. So, this paper use Fourier modal method to analyze the near field characteristic of CSG and BSG combined element. Through theoretically analysis and numerical calculation, amplitude and phase distribution of electric field are present both inside and outside the diffractive structural region, and the maximum peak-to-average modulation in near field is also given. Based on this study, the most possibility of optical damage induced by beam modulation of CSG and BSG combined element appears in the neighborhood of the interface.
New infrared photonic lattice coating
C. F. Schmidt, W. C. Sweatt, I. El-Kady, et al.
We have designed, fabricated, and tested large sheets of photonic bandgap (PBG) material that have a "cubic array of cubes" structure. Structures with bandgaps in two wavebands have been fabricated: the thermal IR (8-12μm) and the visible/near IR (0.6-2.5μm). A thermal-IR PBG can modify the emission properties of structures for temperature control. Visible/near-IR PBGs can be used in photonic circuits and can improve illumination efficiency.
CCD on-chip imaging for smart micro-object and fluorescence imaging system
Hongyun Qiu, Yang Liu, Liqun Sun, et al.
The imaging method by simply putting the object directly on the surface of CCD or CMOS array chip is experimented. A 4.65*4.65μm pixel size 1024*768 CCD chip is used in the experiments. CCD's optic window is removed and surrounding lead on chip is covered with some glue to protect the CCD chip from damaged during the imaging operation. Light emitted or transmitted from object is gathered by the nearest one or several pixels. The comparative experiment shows, to compare the normal microscope imaging using the optic lens, Sharp image with no color shift, optic aberration and field distortion is achieved. To compare with a 4x N.A=0.1 lens at the same magnification, better light couple efficiency and simple optomechanics construction are achieved in our experiment system. As the key factors effecting the image PSF,MTF, resolution, contrast and couple efficiency, the object distance and illumination light path are analyzed and experimented. It shows this will be a potential ultra small size, high efficiency and low cost micro-object imaging and fluorescence imaging system for cell level biology photometry and imaging.
Automated zoom lens design and second-order derivative optimization methods
Sergey G. Menabde, Vitaly M. Klimov
For modern multimedia devices, such as digital photo and video cameras, compact size of optical system is becoming more and more important. This work is dedicated to zoom lens design and second-order derivative optimization method of designed system with using of computer program which allows to design a small-size high-quality system. For lens designing we are using the third order aberration theory and an equation set describing interrelations of system parameters, such as minimum length of system, focal length of each component, their shifts and distances between them. Also equations include conditions of uninterrupted focusing on CCD. Zoom lens consists of three components, two of which are movable. First component is immovable. Number of lenses in each component (two or three) is determined automatically in according to conditions of minimum aberrations and manufacturability. Designed system contains only second-order surfaces with eccentricities. Complete correcting of aberrations consists of two phases. First, the best constructive parameters (radii of curvature, thicknesses and eccentricities) are determined for designed system. The second-order derivative method is used for that. The main feature of this method is the using of Hesse matrix of wave aberration function. Second, for selected surfaces aspherical coefficients are determined. Wave aberration's dependence of constructive parameters and aspherical coefficients is used.
Applications of chirped microlens arrays for aberration compensation and improved system integration
The fields of applications for microlens arrays are widespread ranging from multi-channel collimation in fiber optics, wave front sensors to imaging and beam shaping tasks. Herein identical lens-lets are arranged on a constant pitch yielding to a regular microlens array. We increase the flexibility of the arrangements to chirped microlens arrays meaning the single lens-lets are neither identical nor placed on a fixed pitch. The describing parameters of the single lenses like radii of curvature, center position and angular orientation depend on the position of the cell within the array. The calculation of the cell parameters can be done either analytically, semi- or fully numerically. One field of application of chirped microlens arrays is the correction of aberrations in cases where the single lenses are dedicated to certain optical channels. We present design considerations, approaches for obtaining the array parameters as well as measurements on prototyped systems with the example of an ultra-thin artificial compound eye objective. Another field of application is the use of chirped microlens arrays for achieving a simplified integration of micro-optical systems. Using the new degree of freedom in the design of the microlens arrays a reduction of the number of optical elements in a micro-optical system can be achieved leading to easier assembly and more cost effective products. We propose a beam shaping system of a laser diode for creation of a line focus with top-hat intensity distribution and present experimental results.
Design considerations for a time-resolved tomographic diagnostic at DARHT
An instrument has been developed to acquire time-resolved tomographic data from the electron beam at the DARHT [Dual-Axis Radiographic Hydrodynamic Test] facility at Los Alamos National Laboratory. The instrument contains four optical lines of sight that view a single tilted object. The lens design optically integrates along one optical axis for each line of sight. These images are relayed via fiber optic arrays to streak cameras, and the recorded streaks are used to reconstruct the original two-dimensional data. Installation of this instrument into the facility requires automation of both the optomechanical adjustments and calibration of the instrument in a constrained space. Additional design considerations include compound tilts on the object and image planes.
Servo-modulator system used in a 2D shearing interferometer
G. García-Torales, J. L. Flores, J. G. Mateos Suárez, et al.
An improvement of a 2D shearing interferometer to measure small and large non-rotationally symmetrical wavefronts aberrations is described. This interferometric system encompasses large and differential wavefront displacements using a high accuracy rotation system incorporated in a Mach-Zehnder interferometer. The rotation of the prism arrangement is controlled with an electronic servomotor system by means of an auto-tuning using a Neural Network Algorithm, NNA. We describe the servo-mechanical system, the electronic interface and algorithms to control the performance of the rotation device with the aim of obtain accurate wave front position by a prism rotator system.
An experimental instrument of diffraction imaging and its applications
Weiping Zhang, Chuanggao Huang, Xiaorong He, et al.
A novel experimental instrument of diffraction imaging and its applications are introduced in this paper. This apparatus is composed of movable mechanical parts, optical elements and computer image acquisition system. It can be readily used in the confirmation of bi-grating imaging phenomena and observation of the ordinary transmission hologram displaying with white light source.
Design and fabrication of dye doped polymer optical fiber for optical amplification
M. Rajesh, M. Sheeba, K. Geetha, et al.
Design and fabrication of dye doped polymer optical fiber and its suitability as a fiber optic amplifier is studied, typical result is presented in this paper.
The fabrication of micro lens controlled by high voltage
Ying Liu, James P. Ryle, Unnikrishnan Gopinathan, et al.
Micro-optical elements are becoming more and more important in both consumer and industrial products. Developments such as the tunable liquid lens and the silicon laser will lead to further development of these technologies. In this paper we shall discuss a method that enables perturbation of the shape of a UV curable liquid droplet using an applied electrostatic field. This method provides a novel method for the control of the pre-cured lens profile and hence the final solid lens optical properties. This method also allows the fabrication of aspheric lenses using the UV-curable technique with the degree of aspericity controlled in real time by varying the applied electric field. The analysis of this fabrication method requires the development of an accurate in-situ lens profile measurement system. A range of techniques can be used to examine the resulting solid lens including mechanical techniques such as Dektak and Talysurf profilometry and optical techniques such as laser profilometry and interferometric techniques. We note that in order to fully characterise this fabrication technique it is necessary to measure the surface profile of the lens both post-curing and also when it is in the liquid state. The method chosen to examine the liquid lens is interferometry. In this study the surface profile of the microlens is examined using a Mach-Zehnder interferometer. The development of this interferometric measurement system and the analysis software are discussed. The application of this system in examining the E-field induced perturbation of the UV curable resin lenses will also be discussed and initial attempts to control the optical properties of the lens by preshaping the lens using the E-Field technique are discussed.
Research on the frequency response function and bandwidth of step-index plastic optical fiber
The Step-index plastic optical fiber (SIPOF) bandwidth calculation model is given. The model includes not only the modal delay but also the attenuation and mode coupling effects. the numerical solution of the power flow equation in Fourier domain which is the main equation in this model is reported. This solution is based on Crank-Nicholson implicit difference method. The frequency response function and bandwidth of four kinds of SIPOFS with different Numerical aperture is researched. The frequency response function and bandwidth under selective excitation is numerically calculated. The results imply that the selective excitation of SIPOF increased effectively the fiber bandwidth. Calculated results are useful for practical application of plastic optical fiber.
Novel composite coded pattern for small angle measurement using imaging method
Suguna Sree Nukala, Sai Siva Gorthi, Kameswara Rao Lolla
A novel approach for measurement of small rotation angles using imaging method is proposed and demonstrated. A plane mirror placed on a precision rotating table is used for imaging the newly designed composite coded pattern. The imaged patterns are captured with the help of a CCD camera. The angular rotation of the plane mirror is determined from a pair of the images of the pattern, captured once before and once after affecting the tilt of the mirror. Both simulation and experimental results suggest that the proposed approach not only retains the advantages of the original imaging method but also contributes significantly to the enhancement of its measuring range (±4.13° with accuracy of the order of 1 arcsec).