This PDF file contains the front matter associated with SPIE Proceedings Volume 7855, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

A polarimeter is an optical instrument used in the transmissive mode for determining the polarization state of a light beam, or the polarization-altering properties of a sample, such as diattenuation, retardation and depolarizion.1 (Reflective "polarimeters" are typically called ellipsometers.) Polarimeters can, thus, be broadly categorized as either light-measuring polarimeters or sample-measuring polarimeters. A light-measuring polarimeter is also known as a Stokes polarimeter, which measures the polarization state of a light beam as described by the Stokes parameters. A sample-measuring polarimeter is also known as a Mueller polarimeter, which measures the complete set or a subset of polarization-altering properties of a sample. Polarimeters can also be categorized by whether they measure the complete set of polarization properties. If a Stokes polarimeter measures all four Stokes parameters, it is called a complete Stokes polarimeter; otherwise, an incomplete or a special Stokes polarimeter. Similarly, there are complete and incomplete Mueller polarimeters. Nearly all samplemeasuring polarimeters are incomplete or special polarimeters, particularly for industrial applications. These special polarimeters bear different names. For example, a circular dichroism spectrometer, which measures the differential absorption between left and right circularly polarized light (▵;A= A_L - A_R), is a special polarimeter for measuring the circular diattenuation of a sample; a linear birefringence measurement system is a special polarimeter for measuring the linear retardation of a sample. Polarimeters have a broad range of applications in both academic research and industrial metrology. Polarimeters are applied to chemistry, biology, physics, astronomy, material science and many other scientific areas. Polarimeters are used as metrology tools in the semiconductor, fiber telecommunication, flat panel display, pharmaceutical and many other industries. Different branches of polarimetry have established their own scientific communities, within which regular conferences are held.^2-6 Tens of thousands of articles have been published on polarimeters and their applications, including books and many review articles.^{1, 7-15} In this paper, I will focus on polarimeters using the photoelastic modulator (PEM).^16-18

Photomechanics, one kind of interferometry based experimental methods used to measure the mechanical quantities, can provide interferometric fringes using specially designed optical setups. Analysis of mechanical quantities from the interferometric fringes needs good understanding of their distribution, which is often not easy when analyzing a complicated model. At this time, the simulation of the experimental results on similar models will greatly improve the experimental data processing of photomechanics. Moreover this simulation will also greatly contribute to the teaching of photomechanics. In this paper, a basic framework for photomechanics simulation is firstly proposed. The specific algorithms for simulation of the two important photomechanics methods, photoelasticity and electronic speckle pattern interferometry (ESPI), are developed. A photomechanics simulation system containing photoelasticity and ESPI is constructed. When simulation, the distribution of the mechanical quantities is firstly calculated using finite element method (FEM), and then the interferometric fringes are generated through the virtual realization of the interferometric procedure in the corresponding optical setup. The whole simulation procedure is realized with the Matlab software. Comparison between the results from simulation and the real experiment shows the validity of the simulation algorithms.

In this paper, we have developed a spectroscopic topological Stokes polarimeter using an axisymmetrical quarter wave plate (AQWP). The AQWP is fabricated by the alignment of segments of quarter wave films. The azimuthal angles of the polarization element are changed in according with its own segment. This element works as same the technique as the rotating quarter wave plate. In the experiment, we evaluated birefringence distribution of the AQWP. By changing a position of polarized singularity point in the beam spot, we can measure states of polarization. We demonstrate that the change of polarization states is corresponded with the change of the polarized singularity points.

In this paper, an approach based on the objective speckles field to measure the elastic modulus of solid material with three-points bending method is presented. The speckle images of the loading force rod under different loading are recorded and performed Fast Fourier Transformation (FFT), the deflection of the specimen can be obtained. The Young's modulus of the specimen calculated agrees well with that of stretch approach. The approach presented in this paper has advantage of simplicity, noncontact and high accuracy.

Besides the requirement on high contrast and low noise, the more important aspect to affect the accuracy of the optical extensometer is the pixel resolution of the digital image. The resolution of the marker positioning algorithms is often evaluated as pixel, and the higher pixel resolution will induce a higher strain measurement resolution in optical extensometer. Since the algorithm error is always seen as a constant, the strain error is decreased with the distance of the measured region increases when using optical extensometer. On the other hand, the lens distortion will affect the accuracy of the marker positioning algorithms. If the distance of the measured region increases, the lens distortion error will also increase for that the lens distortion is much evident at the image margin. Therefore, when applying optical extensometer, a balance should be found between the algorithm error and the high distortion of the marker image. In order to obtain the best measurement accuracy, the marker positions for optical extensometer should be optimized. An optimization model for choosing best marker position for optical extensometer is constructed on the considering of the pixel resolution and second order lens distortion. It can be concluded that the extensometer using markers located at the position optimized from the optimization model would give the best measurement results, and the law that the best distance between the two markers will change with the size of the strain if the distortion parameters of the camera is given has been found.

This paper focuses on the effect of operating temperature of uncooled CCD on the strain measurement error when the CCD is used to measure strain in an optical extensometer. A special experiment is designed in which an optical extensometer is used to measure the strain and a thermocouple is used to measure the temperature of CCD. The results show that the measured temperature of CCD has a similar tendency with the change of the measured strain. For different types of uncooled CCD, the temperature varies about 5~10 degree from the beginning of the experiment to the end, and the error of the measured strain induced by the temperature was about 120~180με. It is considered that the error is related to the inherent noise of the electronic components of the CCD whose operating mode is sensitive to the temperature change. When using the optical extensometer, it is suggested to preheat the CCD 1~2 hours before the experiment especially in doing high accuracy measurement. Otherwise, the strain induced by the operating temperature should be eliminated from the measurement results through conducting temperature compensation method mentioned in this paper.

In general, eddy current sensors are point-based sensors with a very high sensitivity but are very slow because of scanning. Optical visual inspections can be very fast but have difficulty in detection of tiny flaws. Magneto-optical imaging is a hybrid sensing technique that combines the advantages of both the eddy current sensor and the optical visual inspection. It has a very high sensitivity and fast inspection speed up to 100mm per second. This paper discusses the optical system design in a magneto-optical imaging sensor including wavelength selection analysis, image contrast enhancement option, and frame subtraction, etc. Theoretical analysis is given as well as initial testing results.

Inner profile measurement is an important matter in such fields as medicine, dentistry and anthropology as well as mechanical engineering and other industrial applications. Here we describe recent development of our measurement principle for inner diameter of pipes and/or holes. The key device in this technique is a ring beam device which consists of a conical mirror and a laser diode. And the fundamental principle is based on optical sectioning without using any contact type stylus. The optically sectioned profile of an inner wall of a pipe-like object is analyzed to give the inner profile in addition to the inner diameter. This optical instrument with a simple and small configuration is now under development for practical uses. In our hitherto trial experimental works, the availability of this instrument has been evaluated in many cases and availability for practical applications is expected, especially, for measurement and inspection of mechanical components and elements besides pipes. This ring beam device consisting of a conical mirror and a LD is assembled to form a disk-like light sheet. We show measurement result of pipes and holes, and, at the same time, report a compact inner profile measuring instrument at this point. Both the ring beam device and a miniaturized CCD camera are fabricated into a glass tube. Availability of this instrument is shown by measuring the inner profiles of various pipes. In response to this trial, there appeared a strong request that not only the internal but external profiles should be measured simultaneously. Therefore we propose potentially possible method for measurement of external profile at the same time with internal profile. If one pair of concave mirrors are used in our arrangement, external profile is captured. In combination with inner profile measurement technique, simultaneous measurement of inner and outer profiles becomes attainable. A measurement result on a bevel gear shows availability of here proposed principle. In addition, we are trying to extend our technique to check defects and/or flaws on the inner wall of pipe-like objects.

To improve difficulties inherent to the conventional three-dimensional profiling system based on pattern projection method, we have proposed incorporating a recent digital device such as a MEMS scanner into projection optics. Due to this revision, first of all, such a small size system as a palm-top camera is attainable, and low cost measurement system is potentially realized. In this system, we can control the scanner to produce the projection pattern with appropriate periodical structure and sinusoidal intensity distribution. Due to this flexible pattern projection, phase-shifting technique becomes applicable for industrial inspection and measurement in automobile industry and others. The camera is as small as a photographic digital camera in dimensional size. In addition, our recent improvement of measuring performance by modulating the projected pattern is to be demonstrated.

Phase shifting based measurements have been well established for use in both interferometry and structured light based measurements. The use of modern LCD, DLP or LCOS based projectors to create and shift projected patterns for use in phase shifting systems has provided new capabilities such as pattern masking, adjustable resolutions and active preprocessing, along with many challenges. Now the latest consumer projection technology has made available low cost, pocket-sized projectors, some with built in memory. These small projectors open up the possibility of mini-phase shift systems, as well as the possibility of portable measurement systems. This paper explores some of the possibilities for systems made with pocket size pattern projectors, and what some of the limitations may be that will need to be overcome. Experimental data will be presented that illustrates some of these challenges.

This paper describes progressive generations of hand held triangulation sensors for measuring small features, from edge breaks to corrosion pits. We describe the design considerations, ergonomics, packaging and interface between the device and part, such as the sensor tip and optional fixtures. We then present a customized design to address different types of surface features and defects. Next, we present the calibration concept, and its execution. The paper closes by summarizing system performance evaluation experiments and their results. It was shown that the system is capable of measuring edges down to a radius of 250 microns at a repeatability of 50 microns.

A simple optical system for small rotation angle measurement is constructed in this paper. A laser diode is fixed on the rotation part of the mechanism and the laser beam is received by a screen. The position of the spot could be registered from the image captured by CCD camera using the gray centroid algorithm. Then rotation could be obtained from the spot movement according to geometrical relationship. In order to verify the system and evaluate its accuracy, a deflection test of a low carbon steel cantilever beam is performed. It shows that the maximum relative error of experiment results and theoretical value is less than 1.5%, the measuring accuracy and stability is satisfied. The system in this paper has many advantages, such as high resolution, low cost, great convenience and could be used to measure small rotation angles of very complex mechanisms under non-contact request.

A competitive homemade two-coordinate autocollimator is presented, which is able to measure the angle along the horizontal and vertical axis by using a single linear CCD to detect the three image point positions of the N shape reticle on the CCD, with total measurement error no greater than 5urad in the measurement range of ±2100urad and the dynamic response frequency 2KHz.

This paper presents an absolute phase calculation method from one composite RGB fringe pattern image by using the windowed Fourier transform (WFT) algorithm and the optimum three-frequency selection method. Three fringe patterns having the optimum fringe numbers are coded into the red, green and blue channels of a composite color image. The generated composite RGB image is projected onto a measured object surface from a Digital Light Processing (DLP) projector and the deformed fringe patterns captured by a color CCD camera from a different viewpoint. The wrapped phase information will be calculated by the WFT algorithm. The WFT algorithm limits the processed image to a small area, so it can give much better phase near edges or discontinuities than FT algorithm. Applying the WFT algorithm to the three fringe patterns obtains three wrapped phase maps. An absolute phase map is calculated pixel by pixel from one composite RGB fringe pattern image after applying the optimum threefrequency selection method to the three obtained wrapped phase maps. Therefore, the proposed method can measure absolute phase of objects having discontinuous surfaces from one snapshot image. Experimental results on moving discontinuous objects show that the proposed method reliably obtains the absolute phase information.

A high-resolution, dynamic Three-dimensional (3-D) profilometry based on the combined stereovision and color-encoded digital fringe projection is proposed. In this technique, a sinusoidal fringe pattern is encoded with spatial neighborhood strategy based on De Bruijn sequences. A decoding algorithm for the color pattern is presented. The absolute phase value is retrieved by space method based on locally intensity variety, and unwrapped by dividing the periods based on the intensity peak and the corresponding color information. Therefore, only a single color image is needed to realize the unique code in pixel dimension, which meets the demand of high-resolution, real-time 3D shape measurement. That means this technique could realize pixel-level resolution and measure disconnected objects. Since the phase value at each pixel is only used to assist stereo matching, the 3-D reconstruction could be realtime, and the accuracy is also enhanced. A measurement system consisted of one projector and two cameras is developed. Experimental results are presented to show the feasibility of the proposed method.

A profilometry based on Fizeau interferometer using the optical comb and the sinusoidal phase modulation technique is demonstrated. The optical comb generated with the Fabry-Perot etalon and a SLD is introduced in the Fizeau interferometer. The interval wave number of comb is swept by controlling the resonance length of the Fabry-Perot etalon. The sweeping range is about 500 μm. The displacement measurement is performed by determination of zerophase or π-phase positions. The accuracy estimated from 5 repeated experiments is about 0.2 rad.

Displacement information of a moving target can be detected using an optical feedback self-mixing interferometry (OFSMI) system. A sensing signal observed from the OFSMI system is called self-mixing signal (SMS). The paper studies the waveform features of the SMSs and proposes an algorithm for reconstructing the displacement of a moving target. The reconstruction accuracy of the algorithm mainly depends on the locating accuracy for those characteristic points on a SMS. A set of rules for identifying those characteristic points are described in the paper. The proposed algorithm is verified by simulation signals firstly, and then applied on extensive SMSs which are obtained from the experimental set-up. The results show that the displacement of the external moving target can be reconstructed under different feedback levels.

Optical feedback Self-mixing Interferometry (OFSMI) can achieve a high-resolution displacement sensing and measurement by using advanced digital signal processing. However, most existing signal processing algorithms used for OFSMI signals are implemented on a PC by Matlab or other programming languages. In this case, the whole structure of OFSMI sensing system is incompact and the measurement is in low speed. The design trends in sensing systems are towarding to small size, high integration and fast real time processing. These trends require us to improve the existing OFSMI design. It is a good solution to apply Field-programmable gate arrays (FPGAs) technique onto OFSMI sensing systems. In this work, we designed a FPGA based signal processing unit for an OFSMI displacement sensing system. The OFSMI sensing signals observed from an OFSMI system is connected to a FPGA development board (Spartan-3E) for high speed signal processing. The FPGA processing unit retrieves the displacement information carried in the OFSMI signals. The FPGA design includes noise reduction, signal peak detection and impulse magnitude tracking. As the magnitude of the sensing signal is time-varying, for adapting the variation, a dynamic updating algorithm is introduced in the magnitude tracking unit. Both simulation and hardware co-simulation show that the OFSMI system with a FPGA based signal processing unit can achieve fast and reliable displacement sensing.

We propose a measurement method of vibrational surface profile for an ultrasonic motor (USM) using a stroboscopic oblique incidence interferometer. A time-dependent behaviors of the stator, one of the main components of the USM, is of considerable practical interest for development of new devices. owever it is difficult to observe its surface profile because there are diffused and vibrational surface. An obliquely incident light would offer advantage of the diffused surface because of higher reflectance. Furthermore, for detecting interferences at the vibrational surface profile, a modulated light source is synchronized with electrical signals of the USM. We are successful to detect a vibrational surface of the stator.

Birefringent dual-frequency laser based on frequency splitting technology has been employed to obtain the frequency difference from approximate 40 MHz to several hundreds MHz. In this paper, the mechanism of frequency splitting in birefringent dual-frequency laser with intracavity quartz crystal is analyzed. Beside the birefringence effect, the optical activity of quartz crystal and the self-reproduction of laser are considered. The formulae of the polarization angles and the frequency difference of the two lasing eigen-modes are deduced in detail, and the continuities of their curves are discussed. Based on these formulae, the theoretical curves of polarization angle and frequency difference are calculated, which are consistent well with their experimental curves.

recently successfully introduced into optics. Optical FMCW interference naturally generates a dynamic signal, both the phase and frequency of which are relative to the optical path difference between the two interfering optical waves. Hence, optical FMCW interference not only can measure the relative change of optical path difference (or other related parameters) more accurately and easily, but also can measure the absolute value of optical path difference (or other related parameters). The phase measurement gives a resolution thousands of times higher than the frequency measurement. Particularly, since the signal of optical FMCW interference is a dynamic signal, to calibrate the fractional phase, distinguish the phase-shift direction and count the number of full periods is quite easy. Therefore, compared with traditional optical homodyne interference, optical FMCW interference can offer a higher accuracy and a longer measurement range. During the last few years, some important achievements in both the theory and application of optical FMCW interference have been made. Today, optical FMCW interference has become a well-defined new branch of physical optics. The investigation of optical FMCW interference not only extends our knowledge about the nature of light, but also offers a new advanced technology for optical metrology. Optical FMCW interference can be used to upgrade some existing optical instruments and to create the new-conceptual optical instruments. In this paper, I attempt to review the principle and applications of optical FMCW interference in metrology.

The multi-wavelength back-propagation (MWB) method enables to determine precisely the optical path different (OPD) longer than the optical wavelength from detecting the amplitude and phase of the interference signal for the multiple wavelengths. In this study, we demonstrate a 1-dimensional thickness profile measurement by the MWB and sinusoidal phase modulation (SPM) technique with a spectral interferometer. The OPD for the front and rear reflecting surfaces of a glass film with the thickness of 100 μm are measured. The thickness profile is successfully measured with repeatability of 2 nm estimated from a standard error between 9 repeatedly-measured profiles.

Two light beams reflected from a front and rear surfaces of a glass film of 20 micron thickness interfere with each other in a common path interferometer. Sinusoidal wavelength-scanning light with the scanning amplitude of 5 nm and frequency of 15 KHz is used to generate a sinusoidal phase-modulated interference signal with the modulation amplitude of 2.6 rad. The phase of the interference signal provides the thickness variation of the film, whose measurement accuracy is a few nanometers. Moreover, in order to achieve a high spatial resolution and a wide measurement region a focused beam is scanned on the surface of the film with a rotating mirror.

This paper analyzes the phase error for a 3-D shape measurement system that utilizes our recently proposed projector defocusing technique. In this technique, by defocusing binary structured patterns, seemingly sinusoidal ones can be generated, and 3-D shape measurement can be performed by fringe analysis. However, there are still significant errors if the object is not within a certain depth range where the defocused fringe patterns still have binary structures. In this research, we experimentally studied a large depth range of defocused fringe patterns, from close to be binary to to be sinusoidal, and its associated phase errors are analyzed. We established a mathematical phase error function in terms of the wrapped phase and the depth z. Finally, the mathematical function is calibrated and is used to compensate for the phase error at arbitrary depth ranges within the calibration volume. Experiment will be presented to demonstrate the success of this proposed technique.

We present a simple calibration method of the phase-based 3D imaging systems based on an uneven fringe projection method. The relationship between absolute phase and depth is linear and independent of pixel position, which can be represented by a polynomial function. By designing a plate having discrete markers with known separate distance in between on the plate surface and projecting uneven fringe pattern onto it, one can calculate the absolute phase of the centre on each marker. The 3D coordinates of all the markers can be obtained by a general CCD camera calibration method. So coefficient set of the polynomial function are determined by using the obtained absolute phase and depth of all the markers. The proposed method was applied to calibrate a phase-based 3D imaging system. Experimental results and performance evaluation show that the proposed calibration method can easily build up the accurate relationship between absolute phase and depth information data.

It is usually difficult to calibrate the 3-D vision inspection system that may be employed to measure the large-scale engineering objects. One of the challenges is how to in-situ build-up a large and precise calibration target. In this paper, we present a calibration target reconstruction strategy to solve such a problem. First, we choose one of the engineering objects to be inspected as a calibration target, on which we paste coded marks on the object surface. Next, we locate and decode marks to get homologous points. From multiple camera images, the fundamental matrix between adjacent images can be estimated, and then the essential matrix can be derived with priori known camera intrinsic parameters and decomposed to obtain camera extrinsic parameters. Finally, we are able to obtain the initial 3D coordinates with binocular stereo vision reconstruction, and then optimize them with the bundle adjustment by considering the lens distortions, leading to a high-precision calibration target. This reconstruction strategy has been applied to the inspection of an industrial project, from which the proposed method is successfully validated.

Fringe Pattern Profilometry (FPP) is 3D surface measuring technique based on triangulation. The utilization of digital projection in FPP system introduces significant phase distortion for Phase Shifting Profilometry (PSP), because of the nonlinear response of digital video projectors, which is referred as gamma distortion. Considering that the distorted phase has a stable function for a reference plane, this paper proposes an approach based on inverse function shift estimation (IFSE) to detect the spatial shift of the distorted phase caused by object height. This spatial shift is independent of projector's gamma distortion and accurate surface can be reconstructed based it. The simulation results show that the proposed method can almost completely eliminate gamma distortion in reconstructed surface and we obtain more than 5 times improvement in practical experiments.

A fast quality-guided flood-fill phase unwrapping algorithm is proposed for real-time 3D Fringe Pattern Profilometry (FPP) system. The proposed approach consists of three steps. First, based on the phase maps acquired by phase shift profilometry (PSP) techniques, a quality map is generated according to the phase variance adjacent pixels on the wrapped phase map. According to the quality map, the phase map is divided into several parts which are categorised as either rapid phase changing areas or smooth phase changing areas. Then quality-guided flood-fill phase unwrapping algorithm is applied to rapid phase changing areas and non-guided path-following algorithm is used in the smooth phase changing area. The proposed approach is much faster than the conventional non-guided path-following algorithm, and it is more robust than the non-guided path-following algorithm. Experiments are carried out to verify the performance.

Structured light based 3D measurement is a typical optic method used to detect surface profile. The primary system projects a structured pattern onto the measured surface. Through the phase shifting analysis, the depth profile is extracted with a high resolution. In this paper a portable device bases on structured light method is introduced. The tool is used to inspect edge breaks and corrosion depth on the turbine system parts. In order to maintain the inspection accuracy under the portable operation, a simple but reliable calibration process and enhancement algorithms are needed to mitigate the variations of user operations and system noise. In this paper, an effective calibration method with simple process is introduced to calculate the system parameters and minimize the measurement errors. A set of image enhancement algorithm designed specially for the structured patterns are introduced that is able to mitigate the noise clearly but won't decrease the measurement resolution. The results are demonstrated through the calibration of a prototype system. Measurement results are presented for sample surface using the filtering. The results show that the calibration process and image enhancement works effectively to maintain a good accuracy and data quality.

Position and orientation estimation of the object, which can be widely applied in the fields as robot navigation, surgery, electro-optic aiming system, etc, has an important value. The monocular vision positioning algorithm which is based on the point characteristics is studied and new measurement method is proposed in this paper. First, calculate the approximate coordinates of the five reference points which can be used as the initial value of iteration in the camera coordinate system according to weakp3p; Second, get the exact coordinates of the reference points in the camera coordinate system through iterative calculation with the constraints relationship of the reference points; Finally, get the position and orientation of the object. So the measurement model of monocular vision is constructed. In order to verify the accuracy of measurement model, a plane target using infrared LED as reference points is designed to finish the verification of the measurement method and the corresponding image processing algorithm is studied. And then The monocular vision experimental system is established. Experimental results show that the translational positioning accuracy reaches ±0.05mm and rotary positioning accuracy reaches ±0.2o .

This paper presents a technique to choose appropriate light source for maximizing the contrast between the object and the background surfaces in color vision application. From the physics of color image formation, three parameters which affect generating signal of color digital camera are researched. An optimal color illumination for enhancing color contrast can be found by maximizing these surfaces spectral reflectance. The discrimination of these surfaces spectral reflectance was estimated by using average color difference in CIELab color space. A printed color patch which have seven several colored characters was used to demonstrate the approach. For each colored character, appropriate Light Emitting Diode (LED) illumination was selected to maximize the discriminability, which is more suitable than D65 illumination. These experiments illustrate the usefulness of properly chosen color illumination in color vision application.

An anti-noise subpixel algorithm of phase-shifting of fundamental frequency was presented based on the phase-shifting of Fourier transform and the anti-noise characteristics of low-frequency part of the phase spectrum of the image. The essence of the algorithm is that the displacement caculation of the image is replaced by the movement caculation of the coordinate, which makes the phase of the fundamental frequency zero under different coordninates when image position changes. Under the circumstances that the image of the CCD autocollimator is polluted by the noises caused by tempreture, the measuring accuracies of the normally-used barycenter, edge detection, Gaussian fitting algorithm and the algorithm presented in this paper were compared. Experiment results show, the subpixel algorithm demonstrated here has the advantages of strong anti-noise ability and high precision. The reliability of the algorithm is also disproved by the peak location of the reconstructed image after the removal of higher harmonics. When applied to the one-dimensional CCD photoelectric autocaollimator used in field conditions, fine linearity and ±3// measurement accuracy were simutaneously obtained in the whole ±3600// measurement range when the temperature varies between -400C-600C.

In order to study the effect of structural parameters on the performance of fiber distance sensor with one normal single mode fiber for illuminating and one inclined multimode fiber for receiving, a theoretical power-distance model is established to describe the influence of the inclination fiber angle, the separation distance between the two fiber tips, the offset distance between the two fiber tips and/or reflector angle on the modulation performance of the fiber distance sensor. Numerical simulation results indicate that for the sensitivity of the sensor, it increases as the inclination fiber angle increases, the separation distance decreases, the offset distance decreases and/or the reflector angle increases. For the linear region, it increases as the separation distance increases, and/or the reflector angle decreases, however, it change less obviously as the inclination fiber angle increases, and even remains unchanged as the offset distance is changeable. For the dead zone, it decreases as the separation distance decreases, and/or the offset distance increases, and the study would help the design of the inclined-fiber receiving distance sensor to the desired modulation performance.

Optical 3D Profile measurements have seen an increasing use in industry from electronics packaging to turbine engine airfoils. This paper will review a number of industrial applications of optical 3D profilometry, what has been achieved, and where new opportunities may be arising. Based upon the current applications, we will identify some of the key barriers to successful implementation, and what is needed to address these barriers from an industrial perspective. Finally, this paper will suggest some possible development areas that may greatly expand the application and acceptance of 3D profilometry.

As an expensive natural stone, jade has a worldwide market. In the jade industry, the inspection and analysis basically rely on the human eye and/or experience, which cause unavoidable waste and damage of these expensive materials. Optical Coherence Tomography (OCT) is a fundamentally new type of optical sensing technology, which can perform high resolution, cross-sectional sensing of the internal structure of materials. As jade is almost translucent to infra red light, OCT becomes an ideal tool to change the traditional procedure to volume data based machine vision system. OCT can also be used for anti-counterfeit of the expensive jade ware.

The fabric quality defect detection is very useful for improving the qualities of the products. It is also very important to increase the reputation and the economic benefits of a company. However, there are some shortcomings in the traditional manual detection methods, such as the low detection efficiency, the fatigue problem of the operator, and the detection inaccuracy, etc. The existing 2D image processing methods are difficult to solve the interference which is caused by non-defect case, just like the cloth folds, the flying thick silk floss, the noise from the background light and ambient light, etc. In order to solve those problem, the BCCSL (Binocular Camera Color Structure Light) method and SFMS (Shape from Multi Shading) method is proposed in this paper. The three-dimensional color coordinates of the fabric can be quickly and highly-precision obtained, thus to judge the defects shape and location. The BCCSL method and SFMS method can quickly obtain the three-dimensional coordinates' information of the fabric defects. The BCCSL method collects the 3D skeleton's information of a fabric image through the binocular video capture device and the color structured light projection device in real-time. And the details 3D coordinates of fabric outside strip structural are obtained through the proposed method SFMS. The interference information, such as the cloth fold, the flying thick silk floss, and the noise from the background light and ambient light can be excluded by using the three-dimensional defect identification. What is more, according to the characteristics of 3D structure of the defect, the fabric can be identified and classified. Further more, the possible problems from the production line can be summarized.

The geometric parameters of wheelsets, such as flange thickness, and rim width, and rim inside distance, are key parameters that influence the wheel-rail contact. The online measurement techniques of these parameters are important to ensure the safety of train vehicle and increase the reliability and efficiency of maintaining. The paper purposed the measurement system based on the optoelectronic techniques. The measuring system is composed of the trigger sensor and the laser displacement sensors fixed on the rails and the system can measure the wheelset's parameters when trains pass through. The measuring results are improved by the wavelet analysis denoised. The average value difference is between 0-0.3mm comparing the system and the manual that shows two methods are coincided. When trains pass through the measuring system under the speed of 10km/h, measuring results shows that the system can meet with the measuring requirement on line.

The steam flow in low-pressure turbine contained abundant water droplets, which will decrease the work efficiency and pose potential threaten to operation safety, so measurement of steam wetness has brought great interest in electricity generation industry. In this paper, a new measuring method using CCD (Charge Coupled Device) imaging technique was proposed to determine the wetness in steam turbine based on the forward small angle light scattering theory. A simulated steam turbine facility was designed to generate the wet steam, and light scattering experiments were carried out at various working conditions in this device. The steam wetness parameters and droplet size distribution were obtained by means of numerical inversion of the light intensity distribution based on Mie scattering theory. The results demonstrate that the obtained data from the present analysis is in good agreement with the results of the theory analysis and previous study, and the proposed method is proved to be suitable for steam wetness measuring and monitoring by further development.

As an effect of globalization, product parts are manufactured more and more in different places. Due to the manufacturing processes, (sub-) products are being transported back and forth and rearranged until they can finally reach the consumer. Not only the environment is increasingly burdened, but also the natural resources are wasted increasingly thoughtless. One reason is certainly because for decades the industry has had only an inflexible concept for the inspection of (sub-) products, which cannot be easily adapted to changes in product layout, for example one robot with one sensor or one rigid structure with a fixed number of sensors for one specific inspection task. This rigid approach is unsuitable for the inspection of variant products. For these reasons, a new concept for 2D and 3D metric and logical quality monitoring with a more accurate, flexible, economical and efficient inspection station has been developed and tested in IOSB.

Computed Tomography (CT) testing is an important non-destructive testing technology in industry inspection. So the important work of CT development is the value calibration and the precise result judgment. Bi-directional reflection distribution function(BRDF) as the common spatial characteristic parameter can be fit for the CT data structure in theory level and the CT data cube can be calibrated using BRDF in both spectral and spatial. Deferent processing calibrated images can be achieved by calibrating CT data in deferent dynamic range using corresponding BRDF absolute value. Thus the influence of BRDF calibration to CT data can be achieved from these serial calibration data and the optimized arithmetic model for this calibration is established. Furthermore, the uncertainty of this value traceability and calibration is analyzed and a corresponding example in CT industry NDT is given which illustrate that this calibration is useful in analysis of PT image because it provide more true image and reduce the probability of error judgment.

In this paper, general theory of Fourier-transform spectrometer and polarization interferometer is presented. A new design is proposed for Fourier-transform spectrometer based on polarization interferometer with Wollaston prisms and linear CCD. Firstly, measured light is changed into linear polarization light by polarization plate. And then the light can be split into ordinary and extraordinary lights by going through one Wollaston prism. At last, after going through another Wollaston prism and analyzer, interfering fringes can be formed on linear CCD behind the analyzer. The linear CCD is driven by CPLD to output amplitude of interfering fringes and synchronous signals of frames and pixels respectively. DSP is used to collect interference pattern signals from CCD and the digital data of interfering fringes are processed by using 2048-point-FFT. Finally, optical spectrum of measured light can be display on LCD connected to DSP with RS232. The spectrometer will possess the features of firmness, portability and the ability of real-time analyzing. The work will provide a convenient and significant foundation for application of more high accuracy of Fourier-transform spectrometer.

Signal to noise ratio is a fundamental performance of a image intensifier, which shows the photons detection ability from object in low light level, and its determine detection range and image definition. The input illuminated circular area must be 0.2mm in diameter on the photocathode, input illuminance must be 1.02×10^-4lx in signal to noise ratio value measurement of Image intensifier . So the paper study a novel illuminance calibration method, which uses PMT photon counting detection technique. The method can directly calibrate illuminance value of very low light sources in signal to noise ratio measurement device of image intensifier. First, we introduce the principle of low light image intensifier S/N tester. Secondly we research illuminance calibration method of 0.2mm in diameter on the photocathode of image intensifier, design quasi-point low light luminometer, which adopts the photon counting detection technique. So we research the radiation characteristic of standard light source with 2856K color temperature and calculate its output photon number, For high accuracy measurement on quasi-point sources, vision function correction and cosine correction is made. Lastly, we research the traceability diagram of this luminometer, which is traceable to our primary photometry metrology standard device. The experimental results indicate the novel illuminance calibration method can accurately directly measure illuminance of quasi-point sources. Comparing with the conventional calibration method this novel method avoids the transfer error. The absolute illuminance calibration uncertainty is analyzed. These analysis results are useful as a evaluating method for improving signal to noise ratio of Image intensifier.

This paper is based on the triangulation method and the random digital speckles are projected on the reference plane and the surface of the object, with the digital speckle correlation principle, solving the height of object and reconstructing three-dimension of the object. Experimental results indicate that the digital speckle correlation technology in the measurement of three-dimensional objects is validity, reliability.

Machine vision now is widely used as non-contact metrology which is a trend of measurement. In this article, a 3D machine vision probe for engineering is designed. The XY axial measurement is done by 2D vision metrology, while the Z axial height is measured by microscope through auto-focus (AF). As the critical part of probe, a long work distance (WD) microscope is well designed. To attain the long WD, a positive and a negative lens group configure the microscope. The microscope, with resolution of 1μm and WD of 35mm, is quite closed to diffraction limited as evidenced from MTF (Modulation Transfer Function) chart.The AF, a key technology in probe designing, is particularly introduced. Images acquired by microscope are calculated to get the AF curve data. To make the AF curve smooth, the images are denoised and the curve is processed with a low pass filter (LPF). And a new method of curve fitting is involved to get the accuracy focused position.The measurement with probe shows that the uncertainty is 0.03μm at XY axial plane, while the uncertainty is less than 3μm at Z axial height. It indicates that our probe achieves requirements.

Principle of using infrared dual-frequency He-Ne laser as a displacement sensor is presented. By inserting birefringent elements into laser cavity, one laser beam is splitted into two orthogonally polarized laser beams. When cavity length is changing, two beams appear one after another. Power turning curves are formed, which provide a method of displacement measurement. Compared to red He-Ne laser, infrared He-Ne laser has the feature of higher gain and corresponding stability. By counting numbers of equal-intensity points and combining subdivision techniques, displacement sensor based on infrared dual-frequency He-Ne laser is expected to afford measurement range of 100mm with resolution of 10 nm.

Finding the position and orientation between a camera and a target with respect to a scene object from n correspondence points is crucial for many computer and robot vision tasks. With a limited number of correspondence points, the closed-from solution is applied to solve the pose estimation problem. To estimate the pose between the camera and the target from the four reference point, a pose estimate model is built with the four projection line between the 3D space point and 2D image point, under the full perspective projection of the camera. The transformation matrix is determined by the coordinates of four reference points in camera coordinate system and the target coordinate system respectively. To figure out the transformation matrix, the distance factor of the four reference points in camera system must be calculated. Considering the quality of the triangle, the pose estimate model with is simplified, which avoid the iteration, as while as taking the advantage of the data redundancy. Considering the specific relationship of the four reference points, the Levenberg-Marquardt algorithm is used to figure out the unknown parameters in the pose estimate model. Then the position and orientation between the camera and the target is obtained with respect to the coordinate transformation matrix from the camera coordinates to the target coordinates. In the experiment, both synthetic and real data are used to examine the accuracy and stability of the pose estimate algorithms with four points. Experiment result shows the distance measurement precision better than 0.03mm, and the angle measurement precision better than 0.2°.

An experiment measuring system is introduced. Angle-resolved single-band and multispectral bidirectional reflectance distribution function measurements are operated in ultraviolet band. Hemisphere spectral reflectivity of some samples is measured. An optimizing modeling method, particle swarm optimization (PSO) is used to model the laser BRDF data of typical samples. The results are fitted with the models developed above using optimize algorithm to get the parameters. Spectral BRDF of samples calculated with the model are in good agreement with the measured data. And these studies about measuring and optimizing modeling of typical roughness target samples in ultraviolet band have significant meanings in a lot of related fields.

A photoelectric autocollimator, which consists of an optical autocollimator and an area CCD and whose standard deviation is less than 0.5" calibrated by a dual-frequency laser interferometer HP5528A, is proposed in the paper. The positional precision of a NC motorized stage is detected automatically and quickly by applying the photoelectric autocollimator calibrated and an optical polyhedron to finish the error compensation of the stage. According to GB/T 17421.2-2000, when the polyhedron and the stage both revolve with the same axis, the positional error of the stage is measured by the photoelectric autocollimator and then sent back to the controlling system of the stage manually or automatically. Experimental results show that an angle can be measured by the photoelectric autocollimator and the calculated position accuracy agrees with that which is measured by a Triangle autocollimator 500-57 at the same time.

A new method based on confocal microscopy is presented to measure the distance between the focus of an objective lens and the curved surface. The focus error signal based on this method is constructed. And this signal features not only the possession of the linear relationship to the defocus, that is the distance between the focus of the objective lens and the curved surface, and direction information of defocus and a wide measuring range, but also the independence of the tilt angle of curved surface, the power fluctuation and the like.

Raman spectroscopy is often hampered by strong fluorescence background that can easily bury the much weaker Raman signal. One of the most widely used techniques to reject the fluorescence disturbance is the shifted-excitation Raman difference spectroscopy (SERDS), which incorporates multiple wavelengths as excitation sources. This paper proposed a SERDS system with 532 nm and 526.5 nm DPSS lasers and a home-made holographic notch filter. In this system, two lasers illuminate the sample alternatively, and two series of spectra are acquired to generate the difference spectrum. And then a regularization constrained least square algorithm is proposed to reconstruct the conventional Raman spectrum from the difference spectrum. Computer simulation of this algorithm is provided and the preliminary experimental results are presented. It demonstrates that this system can effectively reject the fluorescence.

When applying phase-stepping interferometry to measure wavefront with aberration, distortion is caused by various factors and the main one is phase-shifting error from phase shifter. In this paper, the calculation theory and consequence in measurement error of the phase shift algorithm are discussed. These algorithms include traditional three-phase algorithm, traditional four-phase algorithm, traditional five-phase algorithm, carre algorithm, new compensating four-phase algorithm and new compensating five-phase algorithm. According to the theory analysis and computer stimulation, these methods are compared through introduce phase-shifting error, wavefront aberration and Gauss noise, the results show the new compensating five-phase algorithm is immune to phase-shifting error, and its result is insensitive to Gauss noise, it can improve measurement accuracy effectively.

Blob detection which focuses on detecting points or regions of a different intensity than the surrounding image is increasingly used in consumer products such as human-computer interfaces and motion tracking. Because blob detection is computationally intensive but requires relatively simple arithmetic operations, it is an ideal candidate for parallelization in hardware. The main goal of this paper is to develop a hardware implementation for blob detection structure that is able to detect multipoint in a video image on a Xilinx FPGA platform. This system consists of three functional blocks. The first block use a dual port memory to get the histogram of video data and then to obtain the threshold value for the image frame. The second block applies the threshold value to the video stream data, gets the line connected component, and these components are then transferred into the third block by Fast Simplex Link (FSL). The third block is a Microblaze processor which does the label connection and gets the center of points. This approach is implemented on a Xilinx Spartan3 chip with 640 by 480 resolutions up to 30Hz. It can be used in various low cost consumer applications.

Two on-line inspection methods of printed matter based on optical image subtraction are proposed, using two kinds of spatial light modulation (SLM) respectively, which are TFT-LCD and CRT-LCLV. The test image of printed matter is obtained by CCD, while the standard image of printed matter is saved in computer. The test image and standard image are jointly displayed on SLM by computer as the input image of an optical image subtraction system, which is an optical 4f system with a sine-grating between two lenses. The subtraction image will occur at the output plane, which contain all defects of the test image. Comparing to machine vision method, this inspection method of printed matter based on optical image subtraction is advantaged because the inspection process is accomplished by the optical system, avoiding any complicated arithmetic. The precision of printed matter inspection is defined by the frequency of SLM and the sine-grating. The relationship between parameters of the subtraction image and parameters of optical system is analyzed.

The modulation and demodulation technique of laser self-mixing interference vibrometer is researched in this paper. Combining with triangular current modulation and DSP demodulation technique, a new-type laser self-mixing interference vibrometer is designed to achieve non-contact vibration measurement of a target. Theoretical analysis, simulation results and error evaluation are presented in this paper. The vibration waveform is reconstructed with an accuracy of 0.325 micron in a wide dynamic range. Experiments results show a good agreement with the simulative results. The vibrometer is compact, inexpensive, self-aligning and can be applied to various vibration measurements for its simplicity.

In the field of industrial product inspection, a CMM (Coordinate Measurement Machine) is indispensable to get high precise dimensions, and it is tedious to inspect a complex shape by manual. For many products, high precise dimensions are only needed on some special features, such as cylinders, holes, and plans. In this paper, an optical fringe measurement system is implemented based on Gray code, and a Canon DSL camera with high resolution is adopted to capture the projection patterns and the coded markers glued on the CMM. The range images from the optical measurement system are automatically aligned with the CMM coordinate system through the coded markers. A greedy feature fitting algorithm is used to processing the obtained points cloud, and the special features are extracted, which are used to direct the CMM to obtain more precise parameters. In this integration system, the whole inspection procedure is automated regardless of the existence of the CAD model of the product. The data from different sensors are fused together by an overlap patch algorithm. As a result, the full surface is scanned, and the necessary precision is guaranteed on some special locations. The design principle and workflow of the integration method are presented, and a detail example is given.

Characteristics of laser radar (LADAR) 3D image depend on ladar transceivers, propagation effects, target/beam interactions, and data processing or detection algorithms. Process of target/beam interaction is determined by target surface optical scattering properties, which can be characterized by bidirectional reflectivity distribution function (BRDF). Based on alternative monostatic BRDF models, we report here a backscattering model of optical radiation for ladar 3D range image. Atmospheric turbulence effects are not treated.

CCD calibration is carried out for wheel set wear online measurement. Calibration precision influences the accuracy of wheel set measurement. A CCD calibration method is designed based on perspective projection of pinhole camera and iterative algorithm. Space angles and object distance of CCD parameters are obtained by CCD calibration. Transformation relation between physical coordinates and pixel coordinates is determined by these two CCD parameters. Experimental results showed that space angle achieved a error of 0.1° and object distance achieved a error of 2 mm. The calibration method meet accuracy demands of wheel set wear measurement.

Plastic is used widely for its cheapness and light weight. In the manufacture of plastic products, optical measurement is always adopted for inspection purpose. There are three phases for a plastic part to be made. First, the rude injection mold must be refined to generate qualified products; then, the technical parameters of the injection machine must be adjusted to produce conforming products efficiently; in the end, the finished products are given. For each phase, optical devices are adopted to obtain point clouds of plastic samples, which are compared with the CAD model, so a registration operation is needed to align the point clouds with the CAD model. In this paper, three different evaluation metrics for registration are put forward for each manufacture phase to meet its special demands. In mold modification phase, a most overlap metric is used to find out the most distortion regions of the mold. In technical parameters adjustment phase, a combined weighted overlap metrics are used to evaluate how close the plastic samples to the CAD model. In the production phase, the samples are placed over a fixture, and a simple feature based registration is used. For each evaluation metric, a suitable algorithm is developed to realize the registration operation. A car's interior panel is used to verify the idea, and the test results proof the validity of the method.

A new method for determining line centre is proposed within a microscope imaging measurement system. Due to the optical diffraction effect the image of each line on the scale is stripe shaped. The strip can be molded as two edges that close together. With the gradient algorithm all the local maximum and minimum in the line scale image are detected. Therefore the rising and falling edge can be positioned in pixel level. The line centre is then the middle of between the rising and falling edge. To achieve a high level accuracy of the centre position, with the points near the line centre in the gradient image a least-squares line fitting algorithm is used. The zero gradient magnitude is located with sub-pixel resolution. Experiments have been performed with a standard line scale under different objectives. Results indicate the effectiveness of the method.

We present a non-contact type monitoring system specially devised to control the cutting depth on the grinding process. This system comprises a one axis scanning stage and the imaging system using line camera and collimated white light source. Experimental results prove that the proposed system is useful, especially for the monitoring system in grinding the piston groove on the cylinder with a few micrometers accuracy in the dozens of millimeter area.

3D point clouds registration is a crucial problem in reverse engineering. In order to register point clouds without manual information on objects, a novel method is proposed based on geometric properties of point clouds. The method consists four parts: selecting public areas, computing normal vectors and curvatures, finding corresponding points and further precise registration. Public areas of point clouds are selected through a scan order method. Normal vector and curvature of each point are calculated through surface fitting. Curvatures of points are taken as the registration relationship and all the pair-wise points with the same or similar curvature are extracted. The property of distance invariance in rigid body transformation is used to match the pair-wise points. Matching points are picked out and mismatched ones are excluded by comparing the curvatures in the k-neighborhood. After that the algorithm of quaternion is used to compute transform matrix and ICP algorithm is introduced to improve registration precision. Experimental results show that the proposed method is robust when registering point clouds of different scans.

The methods for performance evaluation of Articulated Arm Coordinate Measuring Machine (AACMM) have been published. Non-arm Coordinate Measuring Machine (NACMM) is similar with AACMM in function, and then the performance evaluation methods should be also similar. The research based on comparing the principle and error resources of the both systems, set up a new combination of the position, orientation and test number, try to locate a more reasonable procedure in evaluate the performance of NACMMs which can be comparable with ASME B89.4.22-2004, but better for find the characteristic of accuracy changing in measurement volume. The procedure is confirmed by testing of different NACMMs.

Based on the CAD model of the free-form surface workpiece, an automatic method to obtain the position and orientation of the workpiece without contact is proposed. The method consists of two steps. The first step is rough localization which gets the approximate correspondence between workpiece and CAD model based on surface features. The second step is fine localization. It is achieved by searching the nearest point on the CAD surface to the light dot by gridsubdivide surface of CAD model. ICP (iterative closest point) algorithm that obtains precise correspondences between the workpiece and the CAD model is used for this step. Experiments were carried out and the results show that the method is efficient and robust.

The UV absorption spectrometry technique DOAS (Differential Optical Absorption Spectroscopy) has been widely used in continuous monitoring of flue gas, and has achieved good results. DOAS method is based on the basic law of light absorption--Lambert-Beer law. SO2, NOX are the principal component of the flue gas. These components are considered by DOAS method at the same time. And certain mathematical methods are used for concentrations measuring. The Continuous Emission Monitoring System (CEMS) based on the principle of DOAS mainly has two probe-styles present: in-situ probe-style and extractive probe-style. For the in-situ probe-style CEMS based on DOAS method, prolonged use for the UV light source, contaminated lens caused by floating oil and complex environment of the flue will all bring attenuation of the spectral intensity, it will affect the accuracy of measurement. In this article, an in-situ continuous monitoring system based on DOAS method is described, and a component adaptive sensing technology is proposed. By using this adaptive sensing technology, CEMS can adjust the integral time of the spectrometer according to the non-measuring attenuation of the light source intensity and automatically compensate the loss of spectral intensity. Under the laboratory conditions, the experiments for SO2, NO standard gas measurement using adaptive sensing technology is made. Many different levels of light intensity attenuation are considered in the experiments. The results show that the adaptive sensing technology can well compensate the non-measuring loss of spectral intensity. In the field measurement, this technology can well reduce the measurement error brought by attenuation of light intensity, compared with the handheld gas analyzer, the average error of concentration measurement is less than 2% FS(Full Scale).

Spheroidal graphite cast iron,with excellent mechanical properties,is widely used in manufacturing many advanced castings,such as crankshaft,gears,pistons,and a variety of machine parts.Its microstructure morphology reflects the quality performance of the products,which leads to an urgent need for a simple,accurate and automatic microstructure morphology detection technique for detecting the quality of spheroidal graphite cast iron.In this paper,opto-electrical detection technique is employed for designing a spheroidal graphite cast iron microstructure automatic detection system,in which the microstructure is imaged by optical microscopy system,and the digital images are obtained by industrial cameras and sent to the computer.A series of digital image processing algorithms,including gray transformation, binarization,edge detection,image morphology and seed filling etc,are adopted to calculate and analyze the microstructure images.The morphology and microstructure analysis methods are combined to obtain the characteristic parameters such as the size of the graphite,the ball classification,the number of graphite nodules and so on.The experiment results show that this method is simple,fast,and accurate and can be employed for assessment of the spheroidal graphite cast iron metallographic phase instead of manual detection.

The purpose of the study is to investigate the correlations among lightness, chroma and hue angle, confirming the lightness is the key factor to ruby color appearance by calculating color difference. Based on the uniform color space CIE 1976 L*a*b*, the lightness is correlated with hue angle. Purplish red rubies with the medium lightness(L*=40~50) and relatively high chroma (C*=25~35) displayed the best visual appearance by naked eyes. The result of partial correlation analysis revealed the correlation between ▵L* and ▵E* (r▵L*×▵E*=-0.992) is relatively higher than r▵C*×▵E* =0.919 and r▵L*×▵E* =0.885, which means that the change of ruby's color was mostly benefit from ▵L*, ▵C* and ▵H* had the little contribution to ▵E*. It is concluded that ▵L* is the key factor of ruby red evaluating, then followed by ▵C* and ▵H*.