This PDF file contains the front matter associated with SPIE Proceedings Volume 10678, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

Mechanical vibrations, air and thermal instabilities are among the most disturbing agents that make difficult or impossible a successful speckle interferometry measurement in harsh environments. Usually, they destroy the interference signal or, at least, dramatically reduce the interference signal quality, what raises the measurement uncertainty to unacceptable levels. Understanding the effects of disturbing agents on speckle interferometry is a first step towards finding strategies to perform effective measurements in harsh environments. There are three main strategies to successfully measure under unfavorable conditions: isolation, robustness and both. By isolation, we mean ways to avoid the action of the disturbing agents on the speckle interferometer and on the measurand. By robustness, we mean using a robust mechanical design, a robust optical technique, a robust data reduction algorithm and/or a robust configuration that is not much disturbed by mechanical, thermal or air instabilities. Compactness, high stiffness, robust mechanical design and an effective clamping system are very important considerations to minimize the influence of mechanical vibrations. One-shot measurement and averaging are also robust strategies to minimize the negative effects of mechanical vibrations as well as air and thermal instabilities. Protective enclosures are useful solutions for reducing air instabilities effects, but sometimes ineffective for achieving thermal stability outside the lab. Robust optical techniques are perhaps the most effective way to reduce the effects of thermal dilatation. The paper describes these concepts and discusses four speckle interferometry systems developed and successfully used by the authors in harsh environments: An achromatic speckle interferometer, using a diffractive optical element, was developed and has been applied to in-situ measure of residual stresses in pipelines. The second and third systems are compact and attachable shearography systems for in-field testing of the adhesion of joints of composite material pipes. Finally, the fourth system is a configuration of a shearography system using two apertures to produce carrier fringes for the measurement from a single image for each loading stage.

This study presents a focusing type grating interferometer for precision displacement measurement. The proposed measurement technique combines the designs of grating interferometers and a focusing type optical path configuration, granting the system high resolution and high stability. This measurement system uses a helium-neon laser as a light source. A beam from the light source is passed through a Wollaston prism and is divided into p-polarized and s-polarized beams separated at 20°. The beams are then focused into the grating via a focusing lens and then diffracted. By choosing a specific combination of grating pitch and lens focal length, it is possible to partially superimpose the zero-order ppolarized beam with the first-order s-polarized beam and form interference after the beams pass through a polarizer. When the grating is displaced, a phase change is introduced into the interference signal, which is then received by a photodetector. Via a self-developed phase demodulation program, the grating displacement can be derived from the phase change of the interference signal. The experiments show that the proposed system can accurately provide displacement information, with a resolution of up to 10 nm and repeatability of up to 10 nm. In addition, the system was tested with random waveforms to verify its ability to measure irregular displacements, and the results prove that the focusing type grating interferometer possesses excellent displacement measurement capabilities.

This contribution introduces a novel approach for phase retrieval of smooth surfaces based on parameter estimation in the two beam interference equation. Perturbation resistance is achieved, by sampling of the required interference images in separated color channels of a 3-Chip-CCD camera, using pulsed LED illumination with pulse width and interval in the range of microseconds. Therefore, two interference images are captured with an extremely short delay compared to the camera frame rate, making the measurement quasi single-shot with respect to low frequency perturbations. An optical path difference is introduced to one of the recorded images, by an oscillating mirror in the reference path. This is required to determine the correct sign of the retrieved phase. The theory of phase reconstruction based on the two beam interference equation is outlined in detail. Experimental results are presented, which indicate a strong influence of dispersion effects on the achievable results.

The linear translation stages play an important role in computer numerical control machine tools, coordinate measuring machines and semiconductor lithograph equipment. Six geometric motion errors are associated with a precision linear stage. High precision simultaneous measurement of multiple degrees of freedom is essential for the multiple-dimension motion calibration of the ultra-precision linear translation stage. In this paper, a laser heterodyne interferometer for simultaneous measurement of displacement and roll angle based on the acousto-optic modulator is proposed. In this optical configuration, a stabilize single-frequency laser (f₀) and two acousto-optic modulators are used to generate the laser source. The frequency shifts of the two AOMs are f₁ and f₂, respectively. The positive first order diffraction beams of two AOMs, f₀+f₁ and f₀+f₂, are merged into one orthogonally and linearly polarized beam with a frequency offset of (f₁-f₂) as the laser source for the roll measurement-unit. A half wave plate (HWP) is utilized as the roll sensing plate to magnify the tiny roll angle into an observable phase shift based on the change of polarization state. The resolution of the roll measurement system is determined by the amplification factor which can be enhanced by a multi-reflection cavity made of a specifically arranged assembly square pyramidal mirror and a folding mirror. The zeroth beam f₀ and the positive first order beam f₀+f₁ provided by two AOMs forms two space separated beams for the displacement measurement, which can eliminate the periodic nonlinearity error. The optical system of the simultaneous measurement of displacement and roll angle were setup. The experimental results showed good repeatability and good consistency.

In this paper, we present the construction and preliminary experimental results of a MOEMS fiber-based integrated probe for endoscopic optical imaging of stomach tissue using a Swept-Source Optical Coherence Tomography (SSOCT). The probe consists of a Mirau micro-interferometer, combined with a GRIN lens collimator and a micromirror scanner. We describe the building blocks of the probe, especially the monolithically integrated Mirau mirointerferometer, fabricated by wafer-level vertical stacking and anodic bonding of Si/glass components, and the electrothermal 2-axis MEMS microscanner allowing large swept angles (up to ±22°) at high frequencies (> kHz) for low driving voltages (<20 V). The results of probe characterization, performed in a designed SS-OCT system, have confirmed proper operation of the probe. The B-scan images were obtained for central wavelength of λc = 840 nm, swept range of Dλ = 60 nm and A-scan frequency of f_A= 110 kHz. The axial resolution of the probe is equal to 5.2 μm (determined by applied swept source), whereas the lateral resolution, measured by use of USAF test pattern, is 9.8 μm.

Our study focuses on popular subjects – the development of new optical measuring instruments in microscopy, coupled with optical coherence tomography (OCT). We have proposed to use hybrid hyperchromatic lenses in the schemes of spectral OCT with switchable wavelength. Change wavelength of optical radiation in the system with a hybrid lens allows accurate focusing on the surface areas of different depths, or in other words, to produce layer-by-layer scan and construction of a three-dimensional image of the investigated object with high quality. The results of our work are the development of new methods of calculation hyperchromatic hybrid lenses. The use of our optical systems in the spectral optical coherence tomography will allow to increase the speed of a spectral scan, to simplify the method of processing the measurement results, to increase the longitudinal and transverse resolution of the resulting images. In our article, we cite examples of optical schemes designed hybrid lenses, quick method of calculation of such systems, the results of aberration analysis and evaluation of the quality of the received image.

During the fabrication process of microlenses, characterization is essential for two purposes: evaluate the optical quality of the element and provide surface information feedback for process optimization. However, no technique can fulfill these two objectives at the same time. Interferometry is used for quality evaluation and optical profilometry for process optimization. In order to address this problem, we propose to use a high resolution interference microscope to characterize microlenses. The focusing capacity can be directly measured by recording the field near the focal spot at different wavelengths. Information about the microlens surface can also be retrieved. All this is illustrated for the front focus of a fused-silica microlens.

We have investigated the effect of brutal steam condensation processes and the behavior of its condensed water prior evaporation, with an integrated resonant photonic structure and dynamic tracking of its transduced signal. The aim of this analysis is to develop a steam condensation lab-on-chip sensor, with the possibility of data treatment with an embedded system. Integrated photonic micro-resonators (MRs) devices have been designed and fabricated with polymer UV210 by means of Deep-UV photolithography. Thanks to this technique, we have achieved racetrack shaped micro-resonators coupled to suited access waveguides. We have assessed such MRs with different geometrical characteristics while changing respectively; the coupling length (LC), the radius of curvature (R) and the width (w) of the guides. The chosen values for the set of parameters LC-R-w (in μm) are 5-5-3 and 10-10-3. The laser source used with the injection bench is a Gaussian broadband laser (λ_central=790 nm, FWHM=40 nm) allowing us to visualize several resonances at the same time in order to multiplex the relevant measurements. The transduced spectrum is then acquired with an Optical Spectrum Analyzer (OSA) linked to a computer with Labview and Matlab software recording and processing data in real time. Then, relevant characteristics to be tracked are the Free Spectral Range (FSR) and the transmitted energy; these quantities can be linked to the physical characteristics of the structure considering both the effective refractive index and the absorption coefficient. The experimental set-up also includes various movies with a top-view imaging camera of the chip (MRs) recording the soft matter process steps, so as to correlate the changes in the transduced spectrum and the behavior of the condensed steam mechanisms (condensation, coalescence and evaporation). Then, the chip is fitted with a temperature controller, so as to carry out measurements at different temperatures: 20°C, 24°C and 28°C.

That paper focuses on diffraction gratings consisting some period failures provided by the errors of the electronbeam lithography method. Samples of lithographic phase gratings were tentatively analyzed to describe that technological errors. A small linear modulation of the period or a joint of a frame edges can cause not only diffraction efficiency losses but also functional breakdown. A simulation of the diffraction of a monochromatic wave at the described diffraction phase structures is carried out. Described diffraction gratings have interest in field of linear displacement encoders.

Microphone membranes tthat have theeir frequency response uniiquely tailoreed to specificc applications are typicallyy produced in an unautomated and expensive manuufacturing prrocess. A combination off holographic stroboscopyy, numerical simulation and laser structuriing is appliedd to shift the resonant frequencies of thee membrane too their desired values given an unknown tension across the microphone membrane due to manuufacturing tollerances. Thee uncharacterized microphone membrane is driven thrrough physical contact withh a piezo. Thhe piezo is swept through a range of frequencies and the full surface profile oscillations are recorded using stroboscopic digitaal holographyy techniques. These resonant displacemennt maps will bee used, in combination with finite differeence eigenvaluue simulationss and perturbattion theory, to determine the preloadedd tension profile across the membrane. Given a desired responsee function of the membrane,, a new membrane mass-density profile can be tailoreed to match the current meembrane to thee requirements of the micropphone. A 20 WW ns Q-switchhed laser steerred by galvanometer mirrorrs will be usedd to restructuree the mass density of the membrane to meeet the design requirements of the micropphone.

This study concerns the determination of the diameter of an optical fiber by analysis of a 2D measured diffraction pattern relative to this linear object, falling within the scope of the Fraunhofer approximation. In this approach, when considering a small line-shaped aperture, with a radius α, or a diffractive object placed at the y-axis, an amplitude of the in-line Fraunhofer hologram can be achieved by a mathematical expression, for a given wavelength of the illuminating light λ and a distance z between the particle and the recording plane. The interferometric signal depends on an Airy curve expressed by a Sinc function whose determination of the zeros makes it possible to deduce an argument giving the radius of the fiber. The measurement is carried out for an object-CCD distance equal to z = 60 mm, with a wavelength of illumination λ = 635nm. The zeros of the Airy function appearing in the analytic expression of the interferometric signal allows us to achieve the value of the measured diameter. Knowing that the fiber radius is α = 62.5 μm, the measured value is acquired with an error of 1.7%.

Theory and experiment in the field of light scattering from optical coatings have been extensively studied and controlled since the 90’s. Indeed surface and bulk theories were developed for substrates and optical coatings, and have revealed great agreement with experiment. Furthermore, angle-resolved apparatuses were built with detection limits close to scattering from the air particles. All these tools have allowed to characterize roughnesses lower than 0.1 nm; also, the microstructure of thin film layers was investigated versus the deposition technologies. Nevertheless, in the last few years, new challenges for light scattering have merged. Actually, modern deposition technologies with their sophisticated monitoring systems today enable the deposition of large numbers of layers, hence providing complex filters which must be characterized at their working wavelengths or in a wide spectral region. Moreover an increasing demand for micro-structured filters has merged and requires new procedures to discriminate scattering from all micro-devices. In this context, we have developed in our group at Institut FRESNEL new numerical and metrological tools to satisfy these demands. All scattering facilities were rebuilt and upgraded, sometimes with strongly different principles. In this paper, we will present a rapid overview of these developments, with a focus on broad band scattering metrology (400nm-100nm) with no loss of performance, separation of intrinsic (surface profile) and extrinsic (local defects) roughness, and the control of large-angle scattering in ultra-narrow band filters. Examples and applications will be given to emphasize all improvements.

We present a multimodal imaging microscope combined with a Muller polarimeter. The multimodal imaging microscope works in both real and Fourier (back-focal) planes. The Fourier plane allows the study of the angular distribution of light scattered or transmitted by the studied sample, whereas the real plane provides an image of the sample, thus allowing the study of the spatial distribution created by the latter one. A Mueller polarimeter provides a complete description of the polarimetric response of the sample. In this paper, we describe the technical characteristics of the multimodal imaging Mueller polarimetric microscope, and we provide an example of the application consisting of the characterization of the polarization of the light scattered by spheroidal microparticles which are made of transparent polymer beads deposited on a glass substrate. A thermal treatment allows transforming the beads from their original spherical shape to those of prolate spheroids. We analyze the modification of the optical response of the particles as a function of their different shape. The experimental results are complemented by numerical simulations based on the Finite-Difference Time- Domain (FDTD) method.

In the domain of optical metrology, white light interference microscopy is mainly known for performing micro and nano surface profilometry. This is achieved by identifying the envelope peak of the fringe signal. However, the polychromatic signal is rich in information and spectral characterization may be performed through the Fourier analysis of the signal, which gives local spectroscopic information about the sample surface. The use of CSI for studying transparent layers has also been well-developed since the analysis of the reflected light provides both structural and spectral information on the layer. Through the spectral analysis of the reflected light, it has been shown that the morphological properties of a thin film structure, namely the thickness and the refractive index, can be precisely measured. In this case, either the amplitude or the phase of the thin film total reflectance spectrum are used to recover the thickness. The technique is based on the best fit between the experimentally measured spectrum with that of the theoretical model using a non-linear least-squares algorithm. Usually, this spectral method is used to investigate thin films having a thickness that does not exceed a few hundred nanometers. In this work, we apply a similar technique, based on the magnitude of the total reflectance spectrum, to study thicker transparent layers. In this case, we show that precautions regarding the effective numerical aperture of the system need to be considered to obtain consistent values of both the refractive index and the thickness. In addition, we demonstrate the possibility of extracting the depth-resolved reflectance spectra of a buried interface independently from the spectral response of the surface. The consistency of these different spectra is demonstrated by comparing the results with those obtained using a program based on electromagnetic matrix methods for stratified media. The lateral spatial resolution of the measurements attained is a spot size of around 0.84 μm for spectrally characterizing small structures.

Imaging Confocal Microscopes (ICM) are highly used for the assessment of three-dimensional measurement of technical surfaces. The benefit of an ICM in comparison to an interferometer is the use of high numerical aperture microscope objectives, which allows retrieving signal from high slope regions of a surface. When measuring a flat sample, such as a high-quality mirror, all ICM’s show a complex shape of low frequencies instead of a uniform flat result. Such shape, obtained from a λ/10, Sa < 0.5 nm calibration mirror is used as a reference for being subtracted from all the measurements, according to ISO 25178-607. This is true and valid only for those surfaces that have small slopes. When measuring surfaces with varying local slopes or tilted with respect to the calibration, the flatness error calibration is no longer valid, leaving what is called the residual flatness error.

In this paper we show that the residual flatness error on a reference sphere measured with a 10X can make the measurement of the radius to have up to 10% error. We analyzed the sources that generate this effect and proposed a method to correct it: we measured a tilted mirror with several angles and characterized the flatness error as a function of the distance to the optical axis, and the tilt angle. New measurements take into account such characterization by assessing the local slopes. We tested the method on calibrated reference spheres and proved to provide correct measurements. We also analyzed this behavior in Laser Scan as well on Microdisplay Scan confocal microscopes.

Rigorous simulations of three-dimensional structures containing different shapes and materials are often too extensive for being performed with regular hardware. We present an application of the Differential Method which is able to perform rigorous simulation of three dimensional microspheres, which are placed with an air-gap over a structured region. An application of GPU-accelerated calculations as well as changes in the approach to the integration algorithms provide a considerable speedup in calculation time. This enables an investigation of the already shown, but until now not reasonably computable super resolution capababilities of microspheres.

The optical performance of wire grid polarizers crucially depends on the fabrication accuracy. Reducing the application wavelengths to the ultraviolet spectral range sets the challenge that structural deviations in the range of typically a few nanometers become comparable to the feature sizes of the structure. In this contribution we present a concept to determine structural parameters and structural deviations of DUV wire grid polarizers fabricated with self-aligned double patterning. To this end, we evaluate the properties (i.e the spectral positions, the angular dependence of the spectral positions and widths) of asymmetry induced resonances in the transmittance spectra which occur at wavelengths larger than 380 nm. We derive requirements for measurement setup for nanoscale determination of the structural properties. Our results indicate that the investigation of the angular dependent transmittance at only two different wavelengths and one polarization state is sufficient to determine structural deviations with uncertainties of ±1:7nm for the effective shift of the ridge and ±0:34° for the effective tilt. Thus, the proposed method allows us to retrieve deep subwavelength structural information at the nanoscale with easily accessible transmittance measurements in the visible spectral range.

Parallel phase shift interferometric detection systems were developed using polarized interferometry, three detectors and multiple wavelengths. In phase shift interferometry (PSI) several phase shifted interference images are usually acquired in a sequence and are algebraically combined to extract the phase information. However, phase imaging is limited both by the 2π phase modulo limiting the ability to map structures with heights only up to half the source's wavelength i.e. several hundreds of nm, and also by error induced by the movements of the sample between the acquisitions of phase shifted interference images. Several approaches for dealing with these limitations have been developed that provided only a limited solution, e.g. using a beat wavelength interferogram by a two wavelength illumination but that is more sensitive to phase noise and thus less accurate and parallel PSI in which all phase shifted images are acquired simultaneously but that does not resolve the height limitation. We have developed a combined and improved technique for parallel PSI and three wavelength illumination enabling overcoming both limitations without elevating phase noise sensitivity. Several bench prototypes were built: some allowing video rate 3D imaging of moving samples such as biological live samples or high throughput scanning of metrology samples with nm scale resolution, and others allowing single point very high speed axial motion tracking and vibrometry with sub-nm scale resolution and max step height of few tens of µm. Selected References: 1. Michael Ney, Avner Safrani, Ibrahim Abdulhalim, Instantaneous high-resolution focus tracking and a vibrometery system using parallel phase shift interferometry, J. Opt. A (Letters) 18, 09LT05 (5pp) (2016). 2. Michael Ney, Avner Safrani, Ibrahim Abdulhalim, Three wavelengths parallel phase-shift interferometry for real-time focus tracking and vibration measurement, Optics Letter 42, 719-22 (2017). 3. Avner Safrani and Ibrahim Abdulhalim, High speed 3D imaging using two wavelengths parallel phase shift interferometry, Optics Letters 40, 4651-4 (2015). 4. Avner Safrani and Ibrahim Abdulhalim, Full field parallel interferometry coherence probe microscope for high speed optical metrology, Appl. Opt. 54, 5083-87 (2015). 5. Avner Safrani and I. Abdulhalim, Real Time, Phase Shift, Interference Microscopy, Optics Letters 39, 5220-23 (2014).

The nanopositioning and nanomeasuring machines NMM-1 and NPMM-200 were developed at the Technische Universät Ilmenau. These machines realise the Abbe comparator principle and the Bryan principle in all three axes to achieve nanometre accuracy. The length measurements are carried out with fibre-coupled laser interferometers. The length and angle values are used together with the probe system signals for ultra-precision position control during surface and coordinate measurements. This paper presents the metrological concepts, the implemented designs as well as specific aspects of the interferometric measuring systems and the measurement uncertainty estimation.

In this work, a novel experimental procedure for thin-film characterization and its data analysis is described. The presented technique is based on low-coherence interferometry and resolves thicknesses with nm-precision. An element with known dispersion is placed in the interferometer's sample arm and delivers a controlled phase variation in relation to the wavelength. This phase variation is dependent on the thickness of the material and its wavelength-dependent refractive index. Furthermore, the phase variation is characterized by a stationary point, the so called equalization wavelength. Changes in the thickness of the material under test will shift the equalization wavelength and transform its interference amplitude. In combination with an imaging spectrometer thin films are spatially resolved with a spatial resolution of 4 μm within a single acquisition. This makes data acquisition fast. The advantage over other conventionally used methods, like reflectometry and ellipsometry, is that signal processing is greatly simplified and therefore much faster.

We propose a wavelength standard for highly precise dimensional measurements. An internal-mirror helium-neon laser is offset-locked to a frequency comb line in order to carry out a secondary standard with reduced phase noise and high optical power. Additional lasers can be traced back to this secondary standard, which will enable us to disseminate the accuracy and stability to the metrology lasers of our nanopositioning and -measuring machine, the so-called NPMM-200. First measurements revealed that the stability of the secondary standard is restricted by the time standard of the optical frequency comb to a value of 2.4·10^-12 (τ = 1 s), which is a significant improvement in comparison to the stability of the existing metrology lasers. In further measurements a metrology laser was locked onto the secondary standard with a relative instability of 0.6·10^-15 (τ = 1000 s).

The laser interferometer is widely used in various fields because of its high resolution, high stability, high measurement speed and large-scale measurement capabilities, thus many research groups and equipment manufacturers have devoted time and resources to its development. This study presents an innovative symmetrical double diffraction laser encoder for precision displacement measurement. The system has the advantages of not defocusing during measurement, and can provide long range dual-axis linear displacement and rotation angle measurement. The system consists of two detection configurations, each composed of a double diffraction optical configuration, grating interferometer and phase demodulation system. The light source is passed through a non-polarized beam splitter, diffraction grating and mirror to form a grating interferometer system. The positive and negative first order beams formed from grating diffraction are reflected back through the grating by mirrors, forming a symmetrical double diffraction optical configuration to effectively enhance the system resolution. When the grating moves a corresponding phase shift will be introduced into the signal. Finally, a photodetector receives the signal and the data is analyzed with a self-developed phase demodulation program to obtain the displacement information. By comparing the displacement information of the two axes, rotation information can be obtained via trigonometric calculation. It can be inferred from the measurement principles that the theoretical resolution can be as high as 15 pm. Experimental results demonstrate that for displacement and rotation measurement, the repeatability of the symmetrical double diffraction laser encoder is 5 nm and 35 nrad, respectively. The system has excellent measurement performance, and its simple structure lends to easy setup and calibration.

This work proposes a two-step phase-shifting algorithm as an improvement of fringe projection profilometry. Considering the working process of fringe projection, the captured fringe image is formulated with two variables, i.e. surface reflectivity and phase value. And a phase shift of 3π/2 is introduced to get the two-step phase-shifting. After appropriate variable substitution, expressions of two fringe images can be transformed into two equations corresponding to a line and a circle respectively. With this circle-line model, the characteristic of solution and the phase error due to non-zero ambient light are analyzed. Then the approach of error compensation is proposed based on estimation of the real fringe contrast and non-linear least square optimization. The validity of the proposed approach is demonstrated with both simulations and experiments.

An approach for localization of the randomly distributed spherical whispering gallery mode resonators on the multiplexed chip has been proposed. The method consists of several steps: chip image enhancement, sensing unit edge detection and light out-coupling area/sensing unit matching. The proposed approach has been successfully tested for detection of the bovine serum albumin protein solution.

Reflective coatings are used on building walls and roofs to reducing heating from solar radiation, and thus have a high reflectivity for the visible and near-infrared wavelengths where sunlight has most of its energy. However, the loss of solar heating during winter increases energy consumption. For temperate latitudes, the solar altitude at noon during summer approaches zenith, while at noon in winter the sun appears much lower in the sky. We propose to take advantage of this change in solar altitude from summer to winter to passively adjust the reflection properties to season. Towards this aim, we numerically calculate the diffraction efficiency of a one-dimensional periodic microstructure using rigorous coupled wave analysis (RCWA). We analyze the angular selectivity of the grating structure for its suitability to retain cooling properties in summer while allowing solar heating in winter. In order to explore angle-selective reflection properties, we explored a series of cross-sectional shapes for the grating by adjusting its geometrical parameters. We find that a rectangular cross-sectional profile produces high angular selectivity of reflection but narrow spectral bandwidth, and trapezoidal shapes produce smaller angular selectivity but broader bandwidth.

Phase Measuring Deflectometry is a highly precise and full-field measurement technique suitable for specular surfaces. Typically, computer displays are used to provide reference patterns whose distortions, when observed as reflections at the surface under test, provide the information to determine its shape. During the evaluation, an ideal display is usually assumed, ignoring properties like shape deviation with respect to a plane. Such deviations, however, limit the accuracy of this technique. To provide a starting point for the development of a more sophisticated evaluation technique, this paper presents our models and results for the simulation of non-ideal display properties in deflectometry. Our simulations contain the geometrical calibration of components of our setup as well as the shape measurement. Evaluations are based on global deviations of the measured surface. The display properties under consideration are investigated individually as well as in combination. As a result of our model-based investigation, we find that shape deviations of the display are the most dominant influence when measuring the global shape of the surface under test while the influence of angle-dependent emission characteristics of the display is neglectable.

Nowadays embedding smart devices into various structures is making great strides: from skyscrapers and bridges to lab-on- a-chip and many biomedical fields. Out of a wide variety of sensors, this study aims to design, simulate, and analyze a mechanical elongation one. Classical elongation sensors tend to rely on Bragg peak wavelength variations, which in many cases are reported with respect to strain variation. In this paper, using a 2D triangular photonic crystal structure embedded perpendicularly into a fiber optic core, we rely on a different sensing mechanism. The optimized 2D photonic crystal structure was simulated using EM Explorer, a specialized electromagnetic (EM) wavelength propagation equations solver. The simulations performed have shown that measuring the phase variations of the EM components can provide very accurate information of ultra-small mechanical deformations. In contrast, other sensors have been relying on amplitude variations for such measurements. The EM propagation through the photonic crystal embedded into a fiber optic core has been simulated at ten different elongation forces, spanning from 1 N to 10 N. The applied force changes the geometry of the lattice structure. The geometric coordinates of the photonic crystal structure are used as input values for EM Explorer, which solves the EM wavelength propagation. The simulation results have shown that the phase of the electrical field exhibits a steep change (highly non-linear) when a particular elongation force is applied. The phase of the electrical field varied from 3.089 to –3.058 radians for a force variation of 1 N. This means that the proposed mechanical deformation sensor had a phase variation of Δθ = 6.14 radians for a mechanical deformation of ΔL = 3.55 nm (1 N loading force). Hence, the sensitivity of the sensor is about 10 pm/°.

In this paper we present a comprehensive description of the pump-probe holographic arrangement and data processing procedure optimized for reconstruction of long smooth strain wave patterns in transparent solids. The approach was tested on detection of nonlinear strain waves generated in a uniform PMMA bar by initial shock pulses of different energies. Phase images representing these waves in the bulk of the waveguide are demonstrated. The strain wave parameters and evolution were shown to be substantially dependent on the initial shock pulse amplitude.

Inline, also known as on-line, measurement is one of the most important measurement techniques in automotive manufacturing industry, especially for body shop. Nowadays, optical measurement systems, which is most commonly used for inline measurement, are developing rapidly. However, some of dimensional features in body shop such as spot welding points, stud welding, high reflective surfaces and black painted materials, are still challenging for traditional optical inline systems to measure. Aiming at optical challenging dimensional features, a measuring system with cameras and fixed illuminations is developed to achieve robust and accurate measurement. Photometric stereo technique is used to obtain the surface normal map of the feature, so the algorithm can adapt to various reflections of the material. A Histogram of Oriented Normals (HON) extractor is proposed to extract the feature vector, which is small enough to fit a neural network, from normal map. After building a database with 1000 normal map and corresponding feature position, an artificial neural network is trained for localization the feature from 2D image. Combining 2D information from two different cameras, the 3D coordinate will be available with triangulation. Comparing with traditional HOG bench mark extractor, proposed system showed significant advantage on optical challenging materials in the experiment with welded stud sample. Comparing with off-line measurement systems, proposed system takes much less time, which gives the potential for optical challenging features inline measurement.

The specific conical shape of the axicon makes them well suited for the generation of so-called Bessel beams. We present here a technological micro-glass blowing platform developed for miniaturization of micro-optical components. This employs the glass-blowing process, silicon micromachining and heterogeneous bonding. Here, we focus on the unconventional fabrication methods of micro-optical components in borosilicate glass. As an example, an original concept of a micro-machined micro-axicons for generation of Bessel beams is demonstrated and experimentally validated.

This paper reports an application of a rainbow technique to characterize both the core and cladding diameter of a single, silica-based, step-index optical fiber. Both quantities are inversely calculated using a correlation formula from the farfield scattering pattern where multiple primary rainbows occur. A set of observations of scattering allows one to retrieve the parameters of interest. Numerical studies assume variable core (10–50 μm) as well as cladding diameter (120– 130 μm). A part of analysis shows how the temporal coherence of the incident beam of light affects the solutions.

Improvements have been made to a commercial Linnik microscope in order to perform measurements in water for studying structures of transparent and non-transparent samples. One of the main goals of the present work is to study pollutants in colloidal layers immersed in liquid. The second reason to work in liquid is to increase the lateral resolution. The challenges to overcome include achieving stability in the complex Linnik design as well as the difficulty of balancing the optical distance of the two arms of the interferometer to obtain the interference fringes. The main problem is the path length compensation in the mirror arm which needs a complex mechanical design to allow a high enough number of degrees of freedom to correct alignment of the optical elements. In our system, the reference mirror arm is mounted horizontally, making liquid immersion tricky. In this work, we have investigated alternative solutions based on non-liquid elastic polymers placed between the end of the objective and the reference mirror using sodium polyacrylate (SPA) beads and PDMS (polydimethylsiloxane) slabs, with a refractive index very close to that of water. The results of the performance tests of the modified system are presented and demonstrated. The new design provides a workable system that is ready for the future study of colloidal and other samples directly in water.

We calculate the forces of a single-beam optical trap, also known as an "optical tweezers," on micron-sized dielectric spheres based on the wave optics regime. These forces have previously been calculated using a geometrical ray optics approach by Ashkin. The relatively simple approach proposed by Ashkin is based on tracing a set of equal intensity rays from a uniformly sampled microscope objective lens aperture, all passing through a single point in space, the focal point of the lens. This model does not take into account the wave nature of light and is, therefore, it cannot account for the effects of diffraction Here we propose the use of the angular spectrum method, based on the fast Fourier transform algorithm, to calculate the scalar wavefield on the surface of a microsphere, from which ray amplitudes and directions can be estimated. This allows for the Ashkin’s method to calculate forces on trapped spherical particle to be amended to account for the effects of diffraction. Numerical results are presented for a laser power of 10mW and a microscope objective with a numerical aperture of 1.25, and compared with those obtained using the traditional geometrical approach.