Structured light system calibration has been widely studied over the decades, and a variety of calibration approaches have been proposed. Among these methods, the flexible method using flat checkerboard is widely adopted. However, there is a lack of studies on selecting the optimal checker size for high accuracy calibration, whilst it is vital to understanding this factor. This paper presents a systematic study on how the checker size affects the calibration accuracy for a structured light system, and provides a general guideline to select the optimal size. For this initial study, 7 different checker sizes are selected, and experiments demonstrated that the system achieved the best calibration accuracy within a certain range of checker size.

An accuracy analysis of fringe projection systems is performed taking into account the geometric properties of the sensor and the surface shape of the measuring objects. Especially the deviations of the normal vector directions between the optical axis of projection and observation contribute to differences in the achievable measuring accuracy. An accuracy model was developed which describes the relation between the (fix) geometry of the sensor components and the (variable) conditions of the measurement characterized by a set of parameters on the one side and the measuring accuracy on the other side.

Fish-eye camera is suitable for 3D shape measurements at short range, because it has very wide depth of field and very wide angle of view. Most traditional calibration methods of the parameters for 3D shape measurements use a calibration chart drawn by white and black dual level lattices. However, edges of lattices are blurred by the influence of spatial LPF characteristics of image resolution. In this paper, we propose a high precision calibration method of the intrinsic parameters using slanting brightness lattice patterns with lower spatial frequency component.

A novel stereo camera architecture has been proposed by some researchers recently. It consists of a single digital camera and a mirror adaptor attached in front of the camera lens. The adaptor functions like a pair of periscopes which split the incoming light to form two stereo images on the left and right half of the image sensor. This novel architecture has many advantages in terms of cost, compactness, and accuracy, relative to a conventional stereo camera system with two separate cameras. However, straightforward extension of the traditional calibration techniques were found to be inaccurate and ineffective. Therefore we present a new technique which fully exploits the physical constraint that the stereo image pair have the same intrinsic camera parameters such as focal length, principle point and pixel size. Our method involves taking one image of a calibration object and estimating one set of intrinsic parameters and two sets of extrinsic parameters corresponding to the mirror adaptor simultaneously. The method also includes lens distortion correction to improve the calibration accuracy. Experimental results on a real camera system are presented to demonstrate that the new calibration technique is accurate and robust.

Cutting tools are an essential component used in manufacturing parts for different products. Many cutting tools are manufactured with complex geometric shapes and sharp and/or curved edges. As such, maintaining quality control of cutting tools during their fabrication may be essential to controlling the quality of components manufactured using the cutting tools. In this paper, a 3D cutting tool inspection system, is presented. The architecture of the system, the cutter inspection workflow and some key technologies are discussed. The relative key technologies include two aspects. The first aspect is the system extrinsic self-calibration method for ensuring the system accuracy. This paper will elaborate on how to calibrate the orientation and location of the rotary stage in the coordination system, including the relative relationship between the axis of the chuck used to hold the tool and the rotary axis used to position the tool, along with the relative relationship between Z stage and rotary axis. Further, this paper will analyze self-calibration solutions for separately correcting the error of the squareness and optical measuring beam and the error of the alignment between a side scan and a tip scan. The second aspect this paper will address is a method of scan planning for automatic and effective data collection. Tool measurement planning plays a big role in saving tool measurement time, improving data accuracy, as well as ensuring data completeness. Ths paper will present a round-part oriented measurement method that includes coarse/fine section scans that aim at getting 2D section geometry in a progressive manner, covering the key sharp/curved edge areas, and the side helical scan combined with the tip round scan for shape-simulated full geometry capture. Finally, this paper will present experimental results and some field tests data.

The three-dimensional measurement method by SEM has already been proposed by using the principle of shadow moiré. In this method, there are some troubles in order to perform a high-resolution analysis. A new method based on the principle of projection moiré is discussed to solve the troubles. In this paper, the mechanism of producing some shadows of the grid on the surface of the object by back scattering electron beam is discussed. Fringe image as the shadow of grating is analyzed by the Wavelet transform. 3-D precise measurement can be realized by using the phenomenon of shadows of grid by electron. The error analysis of the proposed method is also performed. Furthermore, a three dimensional structure of the head of a hard disk is measured by the system using the grating of which pitch is 4 μm. From comparison with AFM, it is confirmed that the proposed method has high-resolution power.

In this paper we present a review of the phase unwrapping problem in Fringe Pattern Profilometry (FPP), based on which we study the spatial shift wrapping problem in spatial shift estimation (SEE) based FPP. An approach for carrying out the spatial shift unwrapping is proposed with its performance confirmed by experiments.

Image deblurring is an important preprocessing step in the inspection and measurement applications of machine vision systems. A computational algorithm and analysis are presented for a new approach to one-dimensional shift-variant image deblurring. The new approach is based on a new mathematical transform that restates the traditional shift-variant image blurring model in a completely local but exactly equivalent form. The new approach is computationally noniterative, efficient, and permits very fine-grain parallel implementation. The theory of the new approach for onedimensional shift-variant deblurring is presented. Further, its advantages in comparison with related approaches, and experimental results are presented.

Automatic inspection of manufactured products with natural looking textures is a challenging task. Products such as tiles, textile, leather, and lumber project image textures that cannot be modeled as periodic or otherwise regular; therefore, a stochastic modeling of local intensity distribution is required. An inspection system to replace human inspectors should be flexible in detecting flaws such as scratches, cracks, and stains occurring in various shapes and sizes that have never been seen before. A computer vision algorithm is proposed in this paper that extracts local statistical features from grey-level texture images decomposed with wavelet frames into subbands of various orientations and scales. The local features extracted are second order statistics derived from grey-level co-occurrence matrices. Subsequently, a support vector machine (SVM) classifier is trained to learn a general description of normal texture from defect-free samples. This algorithm is implemented in LabVIEW and is capable of processing natural texture images in real-time.

Analyzing the state of polarization of these reflected beams by using Stokes parameters is used to characterize the natural properties of the surface. We show the angle-resolved Stokes parameters of several objects with rough surface, and derive depolarized components caused by scattering. The preliminary results offer our further investigation of the relation between the optical performance and the structure of the rough surface.

The increase in awareness of the need to improve quality control on part machining efficiency has led to a great deal of research aimed at cutting tool geometry analysis. This paper presents a framework of preprocessing point-based data and extracting parameters after feature detection and data segmentation for cutting tool inspection, assuming unorganized measurement data. The data processing method, including data decimating, smoothing, normal and curvature estimating, denoising, sorting, as well as re-sampling, are exploited to meet the demands for high quality, data simplification for geometric analysis. We will discuss the geometry analysis for parameter extraction, including key feature point detection and key area segmentation based on general reverse engineering solutions and specific cutting tool characteristics. Based on the presented simplification methods using virtual slicing and rotary axial projection data, some cutting tool dimensional parameters can be extracted directly. Alternately, based on 2D points on a given cross section, a plurality of curves can be generated, and optimized by minimizing deviations between the set of points and the plurality of curves. Section parameters can then be extracted from the optimized curves. Furthermore, the methods and processes of multi-section based spatial parameter extraction will be illustrated. This paper presents experimental results and field tests. The experimental results show that the preprocessing is very robust and the parameter extraction results agree with what is expected.

This paper presents a methodology for the non-contact inspection of geometric features of internal threads in machined automotive parts. The method enables in-process internal thread quality verification using a high-precision laser sensor. It allows extracting thread pitch, major and minor diameters, thread height and even allows finding the angular location of the starting point of a thread with respect to a reference point on the perimeter. An in-process thread inspection prototype possessing five axes of motion is presented to demonstrate the capabilities of this method. The validation of this method and the self-calibration approach for system alignment were tested on several internal threads showing a high degree of repeatability.

Roughness of a paper surface is particularly important in paper and board destined to be printed. Surfaces are often coated and the amount of coating and method of application used depends on the roughness of the base paper. We present a method of measure of the roughness of the paper based in the analysis of speckle pattern on the surface. Images are captured by means of a simple configuration using a laser and a camera CCD. Then, we apply digital image processing using the co-occurrence matrix, so this method can be considered as a non-contact surface profiling method, that can be used online.

The potential of scatterometry has been developed for many years, but it is challenging to accurately and quickly obtain the overlay error from diffraction data. We presented a method to measure the overlay error by choosing an optimal measurement target design for scatterometry. All of the simulations in this study were calculated by rigorous coupled wave analysis. A set of two layer grating model were developed for evaluation of overlay measurement sensitivity at different incident angle, such as theta (0° to 90°) and phi (0° to 180°). We also compared the optical response of zero order and first order diffraction signature. We can use appropriate target design and measured condition to maximize the overlay measurement sensitivity and reduce the noise from lithography printing error. In addition, the diffractive signature imaging microscope (DSIM) is introduced to measure the diffraction signature. This instrument is a full-optical operation system without any mechanical movement, so it has good stabilization.

In sweet cherry (Prunus avium), the red pigmentation is correlated with the fruit maturity stage and can be measured by non-invasive spectroscopy. In the present study, the influence of varying fruit scattering coefficients on the fruit remittance spectrum (cw) were corrected with the effective pathlength and refractive index in the fruit tissue obtained with distribution of time-of-flight (DTOF) readings and total internal reflection fluorescence (TIRF) analysis, respectively. The approach was validated on fruits providing variation in the scattering coefficient outside the calibration sample set. In the validation, the measuring uncertainty when non-invasively analyzing fruits with cw method in comparison with combined application of cw, DTOF, and TIRF measurements showed an increase in r² up to 22.7 % with, however, high errors in all approaches.

A collimated line beam is incident at an oblique incident angle of 0.61 rad into an inner surface of a hydrodynamic bearing whose inner diameter and length are 3 mm and 3.5 mm, respectively. Lights reflected in specified directions from the inner surface are selected to obtain an optical field whose phase distribution is proportional to the inner surface profile. This optical field interferes with a reference optical field in a two-wavelength interferometer using a tunable external cavity laser diode. Shapes of grooves with depth of about 5 μm and width of about 0.15 mm formed on the inner surface can be measured with an error less than 0.3 μm.

We have developed a ballistic shock sensor based on interferometric velocimetry. The requirements of the sensor are that it should measure the motion of an impacted armored plate with velocities up to 10 m/s, frequencies up to 100 kHz, and displacements not exceeding about 3 mm. Our fiber optic system uses a 3 × 3 fiber directional coupler and digital demodulation for passive stabilization of the interferometer. In this paper, we describe the digital signal processing for phase drift compensation and automatic calibration of the system. Simulation results will be presented.

Rotating machinery parts, e. g. roller bearings or turbine engines, are present in many industrial applications. Within this paper, a metrology system for determining the out-of-plane and in-plane deformation and vibration of rotating objects is presented. The system consists of an optomechanical image derotator, which is combined with a high speed camera and a scanning Laser-Doppler-Vibrometer (LDV). The image derotator is used to measure deflection and vibration in a coordinate system fixed to the rotating object. To demonstrate the capability of this measurement system, examples of high relevance in industrial applications are considered.

This paper presents a digital multiple-wavelength phase-shifting technique for three-dimensional shape measurement. The projected phase-shifted fringe images have wavelengths of λ_κ = W/2^κ-1 (k = 1,2,3...). The phase unwrapping is not needed for the longest wavelength because a single fringe covers the whole area. The shorter wavelength phase, φκ(x,y), is unwrapped by referring to the previously unwrapped longer wavelength phase, Φ_k-1(x,y), pixel by pixel without accessing its neighborhood pixels. Experiments demonstrate that this technique has low noise and less sensitivity to motion. It can be used to measure arbitrary step height and multiple objects simultaneously.

A high level of immunity to vibration required for on-machine measurements is demonstrated by the continuous phaseshifting interferometer described in this work. Phase measurement errors caused by environmental disturbance and mechanical instability are eliminated by Fourier analysis on a few hundreds of fringes captured by a high-speed CMOS camera. For the purpose, phase shifting is applied in a continuous mode. The proposed continuous phase-scanning method is proposed to apply the phase-extraction principle on a specific heterodyne frequency generated from multiple cycles of 2π-scanning by the uniform translation of PZT-driven stage. As a result, inherent drawbacks of conventional PSI algorithms, such as nonlinearity errors of PZT, measurement speed, complexity of phase analysis algorithm, can be overcome effectively. The experimental results about surface measurement of 1" spherical concave mirror show that superior phase reconstruction performance with good quality can be achieved even under severe vibration circumstances simulated by target excitation along a lateral direction.

To improve difficulties inherent to the conventional three-dimensional profiling system based on pattern projection method, we propose incorporating a recent digital device such as a MEMS scanner into projection optics. Due to this revision, first of all, a compact measurement system is easily attainable, and, when we adjust the scanner to produce the original pattern with non-equal periodical structure, the projected pattern is so formed as to be equal in period on the reference plane. In addition, the pattern becomes sharp over the whole field of measurement when the Scheimpflug condition is satisfied in optical arrangement. This brings easier analysis of the captured pattern and attains the threedimensional profilometry system with deeper range of focus, wider field of measurement and higher accuracy of measurement.

Structured light systems have used many forms of means to create structured patterns ranging from laser lines and physical gratings to current programmable projectors. There are both good and bad aspects of each method, including considerations of contrast, brightness, coherent noise, line stability, and noise associated with the shape of the pattern of lines created. This paper will compare the major means of structured light projection including laser lines, white light gratings, LCDs, DMDs, and LCOS projectors. These method will be analyze with respect to the key performance parameters of the projection means as applied to the most popular means of analysis, including both line center and phase shift analysis. Finally, the results of efforts to characterize the effects of drift of the patterns will be detailed within the context of efforts to obtain absolute distance information at the few micron level.

Microscopic TV holography (MTVH) is widely used for out-of-plane deformation and 3-D surface profile characterization of microsystems. However, the problem of overcrowding of fringes shows up when deformations are large, making quantitative fringe analysis difficult. In this paper, we introduce the use of microscopic TV sherography (MTVS) for microsystems characterization so that under relatively large out-of-plane deformation the slope of deformation is measured, rather than the deformation itself. The optical arrangement consists of a zoom imaging system with a conventional Michelson shear interferometer. We use the digital speckle photography (DSP) technique for precise measurement of magnitude of the lateral shear introduced between the two sheared images.

With refraction microscope optics it is generally understood that as magnification increases field-of-view will decrease. This constraint has posed scaling limitations for microscopy of large objects. We have shown in theory and proven in a reduction-to-practice that in the special case of grazing incidence diffraction, as magnification increases, field-of-view remains constant while efficiency goes down. This distinction has utility for many 3D optical inspection tasks. A holographic optical element (HOE) is used as the microscope's primary objective, and a laser stripe is used to interrogate target surfaces. The microscope's HOE can be embossed in polycarbonate and offered as a consumable part that can be replaced inexpensively if it becomes contaminated. Specimens can be placed on a moveable stage and advanced to collect a sequence of 3D profiles. Laser speckle is ameliorated as a natural consequence of the scanning mechanism. A prototype of the microscope has been demonstrated in a desktop embodiment. It is contemplated as a profiler for industrial inspection and quality control.

We present a dual mode interferometer system based on a single-frame phase acquisition sensor that is capable of measuring the dynamic displacement of both specular and diffuse components. The single frame acquisition allows the interferometer to freeze the motions of the test articles in both configurations and examine the dynamic nature of the surface figure under dynamic stress. The system has applications in the testing of dynamic optical components such as deformable mirrors as well as defect detection and structural stability of composite materials. This paper will provide an overview of the interferometer design, outline the different measurement configurations and present measurement results of dynamically excited test articles.

The use of a color visibility-modulated fringe pattern is proposed to further accelerate image acquisition in the newly proposed combined stereovision and phase shifting method for 3-D shape measurement. The method uses two cameras and one projector and can eliminate errors caused by inaccurate phase measurement. In order to eliminate the need for pattern switching and thus make real-time image acquisition possible, the use of a visibility-modulated fringe pattern was previously proposed. This modified pattern is sinusoidal in one direction as in a conventional fringe pattern, but is visibility-modulated in the other direction. Using this modified pattern we can achieve pixel-level phase matching in both directions without changing the fringe pattern. In this paper, a color visibility-modulated fringe pattern is introduced to further accelerate image acquisition. To obtain the three fringe images simultaneously, we encode the three phase-shifted fringe patterns into the R, G, and B channels of a color pattern and project it onto the object via a color projector. The color fringe image is then taken by two single-CCD color cameras simultaneously and each decoded into three fringe images. The problems specifically associated with color systems, such as color coupling and color imbalance, will be shown to have much less effect on the measured results. With this technique, the acquisition speed is limited only by the frame rate of the camera, which significantly reduces the errors caused by object motions. Experimental results are presented to support claims of the proposed method.

In this paper we present an extension to high resolution multi-view fringe projection systems, as introduced in [1], in order to add pixel synchronous colour information to 3D point clouds. Our approach allows the use of a separate colour camera without the drawback of having to rely on complex image-tosurface mapping algorithms. The advantage of the new method is that no loss of spatial measurement information occurs. Additionally, colour measurement is not limited like in previous coloured structured lighting approaches. Furthermore this paper covers the task of seamless fusion of coloured multi-view 3D point clouds. Due to differences in lighting and viewing direction in each single object view a simple data fusion causes visual artefacts and seams in the final object illustration. Several approaches to this problem have been applied and evaluated. This includes point-bypoint lighting and viewing angle normalization via physics-based reflection models and measurement geometry aided image processing algorithms. The result of these considerations is an automatic system to create the point cloud of a 360-degree object view with each measuring point containing range and colour information.

Chromatic confocal spectral interferometry (CCSI) is a hybrid method for fast topography measurement, which combines the advantages of the interferometric gain and accuracy with the robustness of confocal microscopy. The CCSI-principle provides a single shot measurement of depth while offering a higher lateral resolution than commonly used spectral interferometers. This contribution is focused on the modeling and simulation of a CCSI-sensor for measuring rough surfaces, based on sequential and non-sequential ray-tracing. With the simulation, the influence of surface roughness, surface reflectivity, and surface contamination on reliability of the sensor can be estimated.

This paper describes a 3D surface profile measurement based on focus method by an optical sectioning. The optical system is employed uniaxial condition of projection and observation axis. The contrast of projected sinusoidal pattern onto the sample is approximated the Gauss distribution along the distance. The highest contrast indicates at the focused plane. It is possible to analyze the contrast distribution by a grating projected method using a liquid crystal grating. A phase-shifting method is applied to the contrast analysis. The liquid crystal grating is powerful tool to make arbitrary intensity and frequency distribution. Surface profiles of mechanical parts were measured to demonstrate for this method.

A portable 3-D shape measurement system based on a combined stereovision and phase shifting method which can realize big scale objects measurement is proposed. This system uses two pre-calibrated cameras and one projector which do not need to be calibrated. During the whole measurement procedure, the projector is used to project a visibilitymodulated fringe pattern on the object and is relatively fixed to the object. The two cameras are set up for stereovision and grab fringe images simultaneously. The cameras can be moved to as many positions as needed to capture single views and these single views can then be transformed into the same global coordinate system to reconstruct the whole 3- D model. Since the phase value at each pixel is used to assist stereo matching only, it does not have to be accurate and the errors caused by inaccurate phase measurement, for example, periodic errors due to the nonlinearity of the projector's gamma curve are eliminated. These two high frame rate cameras can grab images as fast as 180 fps. Using the visibility-modulated fringe pattern the phase information in one direction and fringe visibility information in the other direction can be obtained simultaneously for stereo matching. Therefore only three images are needed for a single view, which means the image acquisition time for each view is just 13.9ms. Experimental results are presented to show the feasibility of this method.

This paper describes a real time, low cost part metrology method for capturing and extracting 3D part data using a single camera and no moving elements. 3D capture in machine vision is typically done using stereo photogrammetry, phase shifting using structured light, or autofocus mechanism for depth capture. These methods rely on expensive and often slow components such as multiple cameras, specialized lighting, or motion components such as motors or piezoelectric actuators. We demonstrated a method for 3D capture using only a single camera, birefringent lenses and ultra-fast electronic polarization switches. Using multiple images acquired at different polarization states and thus different focal distances, a high-resolution 3D point cloud of a test part was extracted with a good match to the ground truth data. This paper will describe the operation of the method and discuss the practical limitations.

The optical inspection and metrology for non-optics industry gains increasing importance. Several optical sensors are available for shape measurements of rough surfaces. However, at fast rotating objects such as turbine blades high temporal resolution is necessary, which often can not be fulfilled by commercially available sensors. The recently developed laser Doppler distance sensors allow temporal resolutions in the microsecond range. The independence of the distance measurement uncertainty to the lateral surface velocity is unique. The laser Doppler distance sensors were realized by the evaluation of the interference signal frequency as well as the interference signal phase. Both sensors have been employed for high-speed inspection.

The purpose of color measuring instrument is judging the color information by scientific method, which may instead of the human's eyes. Generally, the instruments of color measuring have two kinds, spectrophotometer and color meter. The former measures spectrum by usage of prism or grating to separate the light, this could achieve high accuracy but with a higher price. The latter obtains tristimulus from color filter; however there is no spectrum information with it. This article establishes a color measuring system and uses eigenspectrum method to correct the average inaccuracy. The measuring system includes tristimulus sensors which were made by color filter, and Xenon lamp as light source. The advantage of this measuring system is the higher accuracy and the lower cost. The eigenspectrum method can correct the average inaccuracy in less eigenvector, which can save the time. This method used singular value deposition to obtain basis function of spectrum set, which can be obtained by measuring. Because the range of the spectrum set was 380nm to 780nm, the eigenvector per nanometer from 380nm to 780nm can be obtained. In general, the color spectrum can be obtained with less eigenvector. This article establishes a color measuring system, which has three sensors and uses Xenon lamp as light source, to acquire the color spectral reflectance. This article also uses the eigenspectrum methods to correct the average color difference in L*a*b* color space,which from 31.2398 down to 4.8401, and reconstructs the spectrum information.

It is measured the topography of a large object by using structured light. The type of fringes generated are equivalent to the produced by divergent beams. In this case the relation between the phase and the height is not linear. In this work it is proposed an iterative estimation to the topography measurement. It is taken in account the variation of period in xdirection of the projected grating and the perspective problem of CCD camera. The shape obtained is compared with the measurements realized with a commercial scanner. The stop criterion value c in the algorithm was chosen of .1 mm. This value corresponds to resolution in z of commercial scanner. To this case, three iterations are enough to reach the value of c. It is observed that after three iterations, the value of z is approximately the same. It is obtained a great discrepancy to the topography measurement when does not use correction in perspective and in the period variation due to divergent projection of the fringes. The main contribution of this work is show that it is important consider the variation of period and the perspective problem in the measurement of the topography to large objects.

We propose a novel multi-channel liquid crystal cell parameter measurement system, which combines the spectroscopic ellipsometry technique with the hyperspectral imaging spectrograph for the multi-point measurement. This system is based on PSA setup (polarizer-sample-analyzer) to measure normalized transmission spectrum for analyzing properties of homogeneous cell and MVA cell. We also develop a theoretical method to simplify the calculation of the orientation angle of liquid crystal cells for speeding up the measurement. The liquid crystal cell gap can be calculated by the measured retardation and the given refractive indices of specified wavelength. The pretilt angle is also analyzed by multi-channel measurement system. We present the analysis of hyperspectral imaging spectrograph and the orientation angle measurement by direct calculation method for high speed on-line multi-channel liquid crystal cell parameter measurement.

A method to measure the frequency change of the tunable laser based on a Jamin shearing interferometer is proposed. The Jamin shearing interferometer is composed of two Jamin plates, two shearing plates and a retardation plate. The tunable laser beam is split into two beams by one Jamin plate. The retardation plate is placed in one of two beams to provide additional phase retardation. Two beams pass two shearing plates, respectively, and are combined by the other Jamin plate to form lateral shearing interferogram. In course of tuning, interference fringes are shifted as a whole and its spacing is kept constant. By detecting displacement of fringes, the frequency change of the laser is obtained. In experiments, we observed that interference fringes were shift periodically when the laser diode was modulated sinusoidally. A series of interferogram in which fringes are shifted as a whole with the variation of the frequency are obtained. The feasibility of the method is verified.

Synthetic aperture imaging ladar (SAIL) used a series of pulses in which the optical frequency was swept linearly in time over a bandwidth greater than several gigahertz. The linearity of such broadly tunable sources is often poor which is leading to phase errors. Many methods are adopted to correct for quadratic and higher-order phase errors such as the reference channel or algorithm for unmatched channel of Aerospace and the reference interferometer of Naval Research Laboratory. If the real value of frequency swept quasi-linearly is measured another direct way to mitigate the waveform linearity problem can be developed. At first the frequency curve is measured with Fabry Perot fiber interferometer. Experiment and results are explained in detail in this paper. The quadratic and higher-order terms of frequency swept are calculated. They may be used to deduce the phase errors directly later. At the same time the wavefront is also measured by a Jamin shearing interferometer through the fringe analysis.

In this work, a dual illumination beam system is used to obtain the strain intensity factor in mode one (mode I) to mechanical elements during tension testing. The displacement field is obtained by means of a phase stepping technique, and deformations are calculated by the Stokes differentiation method. Results are compared using a finite element analysis technique.

The fabrication of new optical materials has many challenges that suggest the need for new metrology tools. To this purpose, the authors designed a system for localizing 10 micron embedded defects in a 10-millimeter thick semitransparent medium. The system, comprising a single camera and a motion system, uses a combination of brightfield and darkfield illumination. This paper describes the optical design and algorithm tradeoffs used to reach the desired detection and measurement characteristics using stereo photogrammetry and parallel-camera stereoscopic matching. Initial experiment results concerning defect detection and positioning, as well as analysis of computational complexity of a complete wafer inspection are presented. We concluded that parallel camera stereoscopic matching combined with darkfield illumination provides the most compatible solution to the 3D defect detection and positioning requirement, detecting 10 micron defects at a positioning accuracy of better than +/- 0.5 millimeters and at a speed of less than 3 minutes per part.