Computer Science › Computer Vision and Pattern Recognition

Optical measurement and interference techniques

Works Count: 60813

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Description

This cluster of papers covers advances in digital image correlation techniques, including camera calibration, structured light and fringe projection methods, 3D shape measurement, phase unwrapping, strain and deformation analysis, optical metrology, and inverse modeling for surface profilometry.

Keywords

Camera Calibration; Structured Light; Fringe Projection; 3D Shape Measurement; Phase Unwrapping; Strain Measurement; Deformation Analysis; Optical Metrology; Inverse Modeling; Surface Profilometry

A practical algorithm for the determination of phase from image and diffraction plane pictures

1972-01-01

R.W. Gerchberg

Gradient Estimation via Perturbation Analysis

1991-11-01

Paul Glasserman , Yu‐Chi Ho

V Phase-Measurement Interferometry Techniques

1988-01-01

Katherine Creath

Optical Shop Testing

2006-11-02

Daniel Malacara

Fringe scanning techniques, now renamed heterodyning or phase shift interferometry, are covered in a completely rewritten chapter. New chapters have been added to cover wavefront fitting and evaluation as well … Fringe scanning techniques, now renamed heterodyning or phase shift interferometry, are covered in a completely rewritten chapter. New chapters have been added to cover wavefront fitting and evaluation as well as holographic and Moire methods. The chapter on parameter measurements has been completely rewritten and an appendix added suggesting appropriate tests for typical optical surfaces.

Quantitative measurement of displacement and strain fields from HREM micrographs

1998-08-01

Martin Hÿtch , E. Snoeck , R. Kilaas

Camera calibration with distortion models and accuracy evaluation

1992-01-01

Juyang Weng , Paul R. Cohen , M. Herniou

A camera model that accounts for major sources of camera distortion, namely, radial, decentering, and thin prism distortions is presented. The proposed calibration procedure consists of two steps: (1) the … A camera model that accounts for major sources of camera distortion, namely, radial, decentering, and thin prism distortions is presented. The proposed calibration procedure consists of two steps: (1) the calibration parameters are estimated using a closed-form solution based on a distribution-free camera model; and (2) the parameters estimated in the first step are improved iteratively through a nonlinear optimization, taking into account camera distortions. According to minimum variance estimation, the objective function to be minimized is the mean-square discrepancy between the observed image points and their inferred image projections computed with the estimated calibration parameters. The authors introduce a type of measure that can be used to directly evaluate the performance of calibration and compare calibrations among different systems. The validity and performance of the calibration procedure are tested with both synthetic data and real images taken by tele- and wide-angle lenses.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>

A state of the art in structured light patterns for surface profilometry

2010-03-23

Joaquim Salví , Sergio Fernández Romero , Tomislav Pribanić +1 more

Optimization of particle image velocimeters. I. Double pulsed systems

1990-11-01

Richard D. Keane , R. J. Adrian

The spatial resolution, detection rate, accuracy and reliability of a particle image velocimeter (PIV) depend critically upon the careful selection of a number of parameters of the PIV system and … The spatial resolution, detection rate, accuracy and reliability of a particle image velocimeter (PIV) depend critically upon the careful selection of a number of parameters of the PIV system and the fluid motion. An analytical model and a Monte Carlo computer simulation have been developed to analyse the effects of experimental parameters and to optimize the system parameters. A set of six nondimensional parameters that are the most significant in optimizing PIV performance are identified. They are the data validation criterion, the particle image density, the relative in-plane image displacement, the relative out-of-plane displacement, a velocity gradient parameter, and the ratio of the mean image diameter to the interrogation spot diameter. These parameters are studied for the case of interrogation by autocorrelation analysis. By a single transformation, these results can be applied to interrogation by two-dimensional Fourier transform analysis of the Young's fringes.

Digital volume correlation: Three-dimensional strain mapping using X-ray tomography

1999-09-01

Brian K. Bay , Tait S. Smith , David P. Fyhrie +1 more

The design and use of steerable filters

1991-01-01

William T. Freeman , Edward H. Adelson

The authors present an efficient architecture to synthesize filters of arbitrary orientations from linear combinations of basis filters, allowing one to adaptively steer a filter to any orientation, and to … The authors present an efficient architecture to synthesize filters of arbitrary orientations from linear combinations of basis filters, allowing one to adaptively steer a filter to any orientation, and to determine analytically the filter output as a function of orientation. Steerable filters may be designed in quadrature pairs to allow adaptive control over phase as well as orientation. The authors show how to design and steer the filters and present examples of their use in the analysis of orientation and phase, angularly adaptive filtering, edge detection, and shape from shading. One can also build a self-similar steerable pyramid representation. The same concepts can be generalized to the design of 3-D steerable filters.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>

Automated phase-measuring profilometry of 3-D diffuse objects

1984-09-15

V. Srinivasan , H. C. Liu , M. Halioua

The high resolution surface profile of a 3-D diffuse object is obtained by measurement of the phase distribution across the image of a projected sinusoidal grating deformed by the surface. … The high resolution surface profile of a 3-D diffuse object is obtained by measurement of the phase distribution across the image of a projected sinusoidal grating deformed by the surface. A shearing polarization interferometer is used for projection. Deformed grating images are detected by an array camera and processed by a microcomputer. Surface height resolutions of better than 10 μm have been attained, limited essentially by electronic quantization noise. In contrast to direct deformed grating analysis, this method, based on phase-shifting interferometric techniques, is capable of accurate measurement even with coarse projected gratings and low density image sensing arrays. Areas of application include industrial quality control, biostereometrics, robotics, and solid modeling for computer graphics.

Digital phase-shifting interferometry: a simple error-compensating phase calculation algorithm

1987-07-01

P. Hariharan , B. F. Oreb , Tomoaki Eiju

La difference de phase entre les 2 faisceaux interferant varie de maniere connue et on fait des mesures de la distribution d'intensite a travers la pupille correspondant a au moins … La difference de phase entre les 2 faisceaux interferant varie de maniere connue et on fait des mesures de la distribution d'intensite a travers la pupille correspondant a au moins 3 dephasages differents

Applications of digital-image-correlation techniques to experimental mechanics

1985-09-01

Tsuchin Philip Chu , W. F. Ranson , Michael A. Sutton

Motion extrapolation in catching

1994-07-01

Romi Nijhawan

Pattern codification strategies in structured light systems

2003-11-24

Joaquim Salví , Jordi Pagès , Joan Batlle

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Overview of three-dimensional shape measurement using optical methods

2000-01-01

Fanglin Chen , Gordon M. Brown , Mumin Song

We first provide an overview of 3-D shape measurement us- ing various optical methods. Then we focus on structured light tech- niques where various optical configurations, image acquisition tech- niques, … We first provide an overview of 3-D shape measurement us- ing various optical methods. Then we focus on structured light tech- niques where various optical configurations, image acquisition tech- niques, data postprocessing and analysis methods and advantages and limitations are presented. Several industrial application examples are presented. Important areas requiring further R&D are discussed. Finally, a comprehensive bibliography on 3-D shape measurement is included, although it is not intended to be exhaustive. © 2000 Society of Photo-Optical Instrumentation Engineers. (S0091-3286(00)00101-X)

Digital image correlation using Newton-Raphson method of partial differential correction

1989-09-01

Hugh A. Bruck , S.R. McNeill , Michael A. Sutton +1 more

Notes on the estimation of the numerical density of arbitrary profiles: the edge effect

1977-11-01

Hans Jørgen G. Gundersen

SUMMARY A description is given of a family of test‐frames for obtaining an unbiased estimate of the numerical density of arbitrary profiles on a section. The counting rule pertaining to … SUMMARY A description is given of a family of test‐frames for obtaining an unbiased estimate of the numerical density of arbitrary profiles on a section. The counting rule pertaining to the test‐frame is simple and requires no corrections based on other estimated quantities.

Determination of displacements using an improved digital correlation method

1983-08-01

MA Sutton , WJ Wolters , WH Peters +2 more

Two-dimensional digital image correlation for in-plane displacement and strain measurement: a review

2009-04-27

Bing Pan , Qian Kemao , Huimin Xie +1 more

As a practical and effective tool for quantitative in-plane deformation measurement of a planar object surface, two-dimensional digital image correlation (2D DIC) is now widely accepted and commonly used in … As a practical and effective tool for quantitative in-plane deformation measurement of a planar object surface, two-dimensional digital image correlation (2D DIC) is now widely accepted and commonly used in the field of experimental mechanics. It directly provides full-field displacements to sub-pixel accuracy and full-field strains by comparing the digital images of a test object surface acquired before and after deformation. In this review, methodologies of the 2D DIC technique for displacement field measurement and strain field estimation are systematically reviewed and discussed. Detailed analyses of the measurement accuracy considering the influences of both experimental conditions and algorithm details are provided. Measures for achieving high accuracy deformation measurement using the 2D DIC technique are also recommended. Since microscale and nanoscale deformation measurement can easily be realized by combining the 2D DIC technique with high-spatial-resolution microscopes, the 2D DIC technique should find more applications in broad areas.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

1982-01-01

Mitsuo Takeda , Hideki Ina , Seiji Kobayashi

A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object … A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moiré topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

Ncorr: Open-Source 2D Digital Image Correlation Matlab Software

2015-03-31

Justin A. Blaber , Benjamin S. Adair , Αντωνία Αντωνίου

Segmentation through variable-order surface fitting

1988-03-01

Paul J. Besl , Ramesh Jain

The solution of the segmentation problem requires a mechanism for partitioning the image array into low-level entities based on a model of the underlying image structure. A piecewise-smooth surface model … The solution of the segmentation problem requires a mechanism for partitioning the image array into low-level entities based on a model of the underlying image structure. A piecewise-smooth surface model for image data that possesses surface coherence properties is used to develop an algorithm that simultaneously segments a large class of images into regions of arbitrary shape and approximates image data with bivariate functions so that it is possible to compute a complete, noiseless image reconstruction based on the extracted functions and regions. Surface curvature sign labeling provides an initial coarse image segmentation, which is refined by an iterative region-growing method based on variable-order surface fitting. Experimental results show the algorithm's performance on six range images and three intensity images.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>

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Recent progresses on real-time 3D shape measurement using digital fringe projection techniques

2009-04-17

Song Zhang

A generic camera model and calibration method for conventional, wide-angle, and fish-eye lenses

2006-06-21

Juho Kannala , Sami S. Brandt

Fish-eye lenses are convenient in such applications where a very wide angle of view is needed, but their use for measurement purposes has been limited by the lack of an … Fish-eye lenses are convenient in such applications where a very wide angle of view is needed, but their use for measurement purposes has been limited by the lack of an accurate, generic, and easy-to-use calibration procedure. We hence propose a generic camera model, which is suitable for fish-eye lens cameras as well as for conventional and wide-angle lens cameras, and a calibration method for estimating the parameters of the model. The achieved level of calibration accuracy is comparable to the previously reported state-of-the-art.

A four-step camera calibration procedure with implicit image correction

2002-11-22

Janne Heikkilä , Olli Silvén

In geometrical camera calibration the objective is to determine a set of camera parameters that describe the mapping between 3-D reference coordinates and 2-D image coordinates. Various methods for camera … In geometrical camera calibration the objective is to determine a set of camera parameters that describe the mapping between 3-D reference coordinates and 2-D image coordinates. Various methods for camera calibration can be found from the literature. However surprisingly little attention has been paid to the whole calibration procedure, i.e., control point extraction from images, model fitting, image correction, and errors originating in these stages. The main interest has been in model fitting, although the other stages are also important. In this paper we present a four-step calibration procedure that is an extension to the two-step method. There is an additional step to compensate for distortion caused by circular features, and a step for correcting the distorted image coordinates. The image correction is performed with an empirical inverse model that accurately compensates for radial and tangential distortions. Finally, a linear method for solving the parameters of the inverse model is presented.

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Digital Image Correlation: from Displacement Measurement to Identification of Elastic Properties – a Review

2006-04-07

François Hild , Stéphane Roux

Abstract: The current state of the art of digital image correlation, where displacements can be determined for values less than one pixel, enables one to better characterise the behaviour of … Abstract: The current state of the art of digital image correlation, where displacements can be determined for values less than one pixel, enables one to better characterise the behaviour of materials and the response of structures to external loads. A general presentation of the extraction of displacement fields from pictures taken at different instants during an experiment is given. Different strategies can be followed to determine subpixel displacements. New identification procedures are then devised making use of full-field measurements. A priori or a posteriori routes can be followed. They are illustrated on the analysis of a Brazilian disk test.

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Electromagnetic diffraction in optical systems, II. Structure of the image field in an aplanatic system

1959-12-15

B. Richards , E. Wolf

An investigation is made of the structure of the electromagnetic field near the focus of an aplanatic system which images a point source. First the case of a linearly polarized … An investigation is made of the structure of the electromagnetic field near the focus of an aplanatic system which images a point source. First the case of a linearly polarized incident field is examined and expressions are derived for the electric and magnetic vectors in the image space. Some general consequences of the formulae are then discussed. In particular the symmetry properties of the field with respect to the focal plane are noted and the state of polarization of the image region is investigated. The distribution of the time-averaged electric and magnetic energy densities and of the energy flow (Poynting vector) in the focal plane is studied in detail, and the results are illustrated by diagrams and in a tabulated form based on data obtained by extensive calculations on an electronic computor. The case of an unpolarized field is also investigated. The solution is riot restricted to systems of low aperture, and the computational results cover, in fact, selected values of the angular semi-aperture a on the image side, in the whole range 0 ≤ α ≤ 90°. The limiting case α → 0 is examined in detail and it is shown that the field is then completely characterized by a single, generally complex, scalar function, which turns out to be identical with that of the classical scalar theory of Airy, Lommel and Struve. The results have an immediate bearing on the resolving power of image forming systems; they also help our understanding of the significance of the scalar diffraction theory, which is customarily employed, without a proper justification, in the analysis of images in lowaperture systems.

An Efficient and Accurate Camera Calibration Technique For 3D Machine Vision

1986-01-01

R. Tsai

The importance of phase in signals

1981-01-01

Alan V. Oppenheim , Jeong Sik Lim

In the Fourier representation of signals, spectral magnitude and phase tend to play different roles and in some situations many of the important features of a signal are preserved if … In the Fourier representation of signals, spectral magnitude and phase tend to play different roles and in some situations many of the important features of a signal are preserved if only the phase is retained. Furthermore, under a variety of conditions, such as when a signal is of finite length, phase information alone is sufficient to completely reconstruct a signal to within a scale factor. In this paper, we review and discuss these observations and results in a number of different contexts and applications. Specifically, the intelligibility of phase-only reconstruction for images, speech, and crystallographic structures are illustrated. Several approaches to justifying the relative importance of phase through statistical arguments are presented, along with a number of informal arguments suggesting reasons for the importance of phase. Specific conditions under which a sequence can be exactly reconstructed from phase are reviewed, both for one-dimensional and multi-dimensional sequences, and algorithms for both approximate and exact reconstruction of signals from phase information are presented. A number of applications of the observations and results in this paper are suggested.

A versatile camera calibration technique for high-accuracy 3D machine vision metrology using off-the-shelf TV cameras and lenses

1987-08-01

R. Tsai

A new technique for three-dimensional (3D) camera calibration for machine vision metrology using off-the-shelf TV cameras and lenses is described. The two-stage technique is aimed at efficient computation of camera … A new technique for three-dimensional (3D) camera calibration for machine vision metrology using off-the-shelf TV cameras and lenses is described. The two-stage technique is aimed at efficient computation of camera external position and orientation relative to object reference coordinate system as well as the effective focal length, radial lens distortion, and image scanning parameters. The two-stage technique has advantage in terms of accuracy, speed, and versatility over existing state of the art. A critical review of the state of the art is given in the beginning. A theoretical framework is established, supported by comprehensive proof in five appendixes, and may pave the way for future research on 3D robotics vision. Test results using real data are described. Both accuracy and speed are reported. The experimental results are analyzed and compared with theoretical prediction. Recent effort indicates that with slight modification, the two-stage calibration can be done in real time.

Fringe projection techniques: Whither we are?

2009-10-07

Sai Siva Gorthi , Pramod K. Rastogi

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Robust two-dimensional weighted and unweighted phase unwrapping that uses fast transforms and iterative methods

1994-01-01

Dennis C. Ghiglia , Louis A. Romero

Two-dimensional (2D) phase unwrapping continues to find applications in a wide variety of scientific and engineering areas including optical and microwave interferometry, adaptive optics, compensated imaging, and synthetic-aperture-radar phase correction, … Two-dimensional (2D) phase unwrapping continues to find applications in a wide variety of scientific and engineering areas including optical and microwave interferometry, adaptive optics, compensated imaging, and synthetic-aperture-radar phase correction, and image processing. We have developed a robust method (not based on any path-following scheme) for unwrapping 2D phase principal values (in a least-squares sense) by using fast cosine transforms. If the 2D phase values are associated with a 2D weighting, the fast transforms can still be used in iterative methods for solving the weighted unwrapping problem. Weighted unwrapping can be used to isolate inconsistent regions (i.e., phase shear) in an elegant fashion.

Digital Imaging Techniques In Experimental Stress Analysis

1982-06-01

W. H. Peters , W. F. Ranson

Digital imaging techniques are utilized as a measure of surface displacement components in laser speckle metrology. An image scanner which is interfaced to a computer records and stores in memory … Digital imaging techniques are utilized as a measure of surface displacement components in laser speckle metrology. An image scanner which is interfaced to a computer records and stores in memory the laser speckle patterns of an object in a reference and deformed configuration. Subsets of the deformed images are numerically correlated with the references as a measure of surface displacements. Discrete values are determined around a closed contour for plane problems which then become input into a boundary integral equation method in order to calculate surface traction in the contour. Stresses are then calculated within this boundary. The solution procedure is illustrated by a numerical example of a case of uniform tension.

Geometric camera calibration using circular control points

2000-01-01

Janne Heikkilä

Modern CCD cameras are usually capable of a spatial accuracy greater than 1/50 of the pixel size. However, such accuracy is not easily attained due to various error sources that … Modern CCD cameras are usually capable of a spatial accuracy greater than 1/50 of the pixel size. However, such accuracy is not easily attained due to various error sources that can affect the image formation process. Current calibration methods typically assume that the observations are unbiased, the only error is the zero-mean independent and identically distributed random noise in the observed image coordinates, and the camera model completely explains the mapping between the 3D coordinates and the image coordinates. In general, these conditions are not met, causing the calibration results to be less accurate than expected. In the paper, a calibration procedure for precise 3D computer vision applications is described. It introduces bias correction for circular control points and a nonrecursive method for reversing the distortion model. The accuracy analysis is presented and the error sources that can reduce the theoretical accuracy are discussed. The tests with synthetic images indicate improvements in the calibration results in limited error conditions. In real images, the suppression of external error sources becomes a prerequisite for successful calibration.

Soil deformation measurement using particle image velocimetry (PIV) and photogrammetry

2003-09-01

David White , W. Andy Take , M. D. Bolton

A deformation measurement system based on particle image velocimetry (PIV) and close-range photogrammetry has been developed for use in geotechnical testing. In this paper, the theory underlying this system is … A deformation measurement system based on particle image velocimetry (PIV) and close-range photogrammetry has been developed for use in geotechnical testing. In this paper, the theory underlying this system is described, and the performance is validated. Digital photography is used to capture images of planar soil deformation. Using PIV, the movement of a fine mesh of soil patches is measured to a high precision. Since PIV operates on the image texture, intrusive target markers need not be installed in the observed soil. The resulting displacement vectors are converted from image space to object space using a photogrammetric transformation. A series of validation experiments are reported. These demonstrate that the precision, accuracy and resolution of the system are an order of magnitude higher than previous image-based deformation methods, and are comparable to local instrumentation used in element testing. This performance is achieved concurrent with an order of magnitude increase in the number of measurement points that can be fitted in an image. The performance of the system is illustrated with two example applications.

Fast two-dimensional phase-unwrapping algorithm based on sorting by reliability following a noncontinuous path

2002-12-10

Miguel Arevalillo‐Herráez , David R. Burton , Michael J. Lalor +1 more

We describe what is to our knowledge a novel technique for phase unwrapping. Several algorithms based on unwrapping the most-reliable pixels first have been proposed. These were restricted to continuous … We describe what is to our knowledge a novel technique for phase unwrapping. Several algorithms based on unwrapping the most-reliable pixels first have been proposed. These were restricted to continuous paths and were subject to difficulties in defining a starting pixel. The technique described here uses a different type of reliability function and does not follow a continuous path to perform the unwrapping operation. The technique is explained in detail and illustrated with a number of examples.

Fourier transform profilometry for the automatic measurement of 3-D object shapes

1983-12-15

Mitsuo Takeda , Kazuhiro Mutoh

A new computer-based technique for automatic 3-D shape measurement is proposed and verified by experiments. In contrast to the moire contouring technique, a grating pattern projected onto the object surface … A new computer-based technique for automatic 3-D shape measurement is proposed and verified by experiments. In contrast to the moire contouring technique, a grating pattern projected onto the object surface is Fourier-transformed and processed in its spatial frequency domain as well as in its space-signal domain. This technique has a much higher sensitivity than the conventional moire technique and is capable of fully automatic distinction between a depression and an elevation on the object surface. There is no requirement for assigning fringe orders and interpolating data in the regions between contour fringes. The technique is free from errors caused by spurious moire fringes generated by the higher harmonic components of the grating pattern.

A flexible new technique for camera calibration

2000-01-01

Z. Zhang

We propose a flexible technique to easily calibrate a camera. It only requires the camera to observe a planar pattern shown at a few (at least two) different orientations. Either … We propose a flexible technique to easily calibrate a camera. It only requires the camera to observe a planar pattern shown at a few (at least two) different orientations. Either the camera or the planar pattern can be freely moved. The motion need not be known. Radial lens distortion is modeled. The proposed procedure consists of a closed-form solution, followed by a nonlinear refinement based on the maximum likelihood criterion. Both computer simulation and real data have been used to test the proposed technique and very good results have been obtained. Compared with classical techniques which use expensive equipment such as two or three orthogonal planes, the proposed technique is easy to use and flexible. It advances 3D computer vision one more step from laboratory environments to real world use.

Structured-light 3D surface imaging: a tutorial

2011-03-31

Jason Geng

We provide a review of recent advances in 3D surface imaging technologies. We focus particularly on noncontact 3D surface measurement techniques based on structured illumination. The high-speed and high-resolution pattern … We provide a review of recent advances in 3D surface imaging technologies. We focus particularly on noncontact 3D surface measurement techniques based on structured illumination. The high-speed and high-resolution pattern projection capability offered by the digital light projection technology, together with the recent advances in imaging sensor technologies, may enable new generation systems for 3D surface measurement applications that will provide much better functionality and performance than existing ones in terms of speed, accuracy, resolution, modularization, and ease of use. Performance indexes of 3D imaging system are discussed, and various 3D surface imaging schemes are categorized, illustrated, and compared. Calibration techniques are also discussed, since they play critical roles in achieving the required precision. Numerous applications of 3D surface imaging technologies are discussed with several examples.

Temporal phase unwrapping algorithms for fringe projection profilometry: A comparative review

2016-05-06

Chao Zuo , Lei Huang , Minliang Zhang +2 more

High-speed 3D shape measurement with structured light methods: A review

2018-03-18

Song Zhang

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Phase shifting algorithms for fringe projection profilometry: A review

2018-05-15

Chao Zuo , Shijie Feng , Lei Huang +3 more

Soil deformation measurement using particle image velocimetry (PIV) and photogrammetry

2003-09-01

David White , W. Andy Take , M. D. Bolton

Linear one dimensional inverse profiling: the role of a perfect reflecting plane in background

2025-06-25

Maria Antonia Maisto , Roberto Dima , Loreto Di Donato +3 more | Journal of the Optical Society of America A

Material surface detail enhancement via stokes imaging

2025-06-24

Qi Hu , Jin Yang , Jin Duan +2 more | Journal of Modern Optics

Collimated phase measuring deflectometry II: Re-design of the optical layout for high-curvature surfaces

2025-06-23

Corey Austin , Wanqi Shang , Lei Huang +4 more | Optics and Lasers in Engineering

A lightweight 3D foot measurement method base on visual hull and slices-net

2025-06-23

Dong He , A. H.-T. Li , Yang Yang +2 more | Optics and Lasers in Engineering

Design Method of Time‐Multiplexed Ultrashort Throw Ratio Projection System with Low Distortion and Uniform Resolution

2025-06-23

Yuefan Shan , Jia-Ping Sun , Xilong Dai +3 more | Advanced Photonics Research

Time‐multiplexed laser projection is recognized as a promising projection technology owing to its broad color gamut and high energy efficiency. The escalating demands for enhanced laser safety and reduced space … Time‐multiplexed laser projection is recognized as a promising projection technology owing to its broad color gamut and high energy efficiency. The escalating demands for enhanced laser safety and reduced space occupation necessitate the development of ultrashort throw ratio (UTR) projectors. However, the inherent mechanical deflection limitations and distortions of micro electro mechanical systems (MEMS) scanners pose significant challenges to achieving UTR projection. To address these constraints, trapezoidal distortion is first eliminated by ensuring vertical laser incidence on MEMS mirrors during the initial projection phase. Subsequently, a systematic design methodology for UTR laser MEMS projection systems is proposed, incorporating a miniaturized catadioptric projection objective that maintains uniformly optical étendue distribution. This configuration achieves a throw ratio of 0.27, reduces pillow distortion to 0.4%, and ensures consistent resolution across the entire screen. Segmentation and modular assembly of the catadioptric objective at telecentric intermediate image planes enhances the efficiency of initial structural design phase. The developed projection prototype experimentally validates the efficacy of the projection system designed through the proposed methodology in decreasing the projection ratio, correcting distortion, and maintaining uniform projection resolution across the full field of view.

An improved Fourier transform profilometry and phase coding for 3D shape measurement

2025-06-21

Yonghua Han , Yanjun Fu , Shiyang Tian +3 more | Optical Review

A Novel Initial Weld Point Positioning and Path Planning Method for Robot Welding Based on Passive light stereo vision and Structured Light Vision

2025-06-21

Tianqi Wang , Qiaochu Li , Junjie He +1 more | International Journal of Precision Engineering and Manufacturing

Phase retrieval in speckle pattern interferometry under vibrational environments

2025-06-20

Peizheng Yan , Yonghong Wang , Mohan Ding +1 more | Optics and Lasers in Engineering

Experimental Study on Glass Deformation Calculation Using the Holographic Interferometry Double-Exposure Method

2025-06-19

Yucheng Li , Yang Zhang , Deyu Jia +2 more | Applied Sciences

This study systematically compares the metrological characteristics of single- exposure, double-exposure, and continuous-exposure holographic interferometry for micro-deformation detection. Results demonstrate that the double-exposure method achieves optimal balance across critical performance … This study systematically compares the metrological characteristics of single- exposure, double-exposure, and continuous-exposure holographic interferometry for micro-deformation detection. Results demonstrate that the double-exposure method achieves optimal balance across critical performance metrics through its ideal cosine fringe field modulation. This approach (1) eliminates object wave amplitude interference via dual-exposure superposition, establishing submicron linear mapping between fringe displacement and deformation amplitude; (2) introduces a fringe gradient-based direction detection algorithm resolving deformation vector ambiguity; and (3) implements an error-compensated fusion framework integrating theoretical modeling, MATLAB 2015b simulations, and experimental validation. Experiments on drilled glass samples confirm their superior performance in terms of near-ideal fringe contrast (1.0) and noise suppression (0.06). The technique significantly improves real-time capability and anti-interference robustness in micro-deformation monitoring, providing a validated solution for MEMS and material mechanics characterization.

APPLICATIONS OF CONTOURS AND PIXEL VALUE SUMMATION IN DETERMINING THREE-DIMENSIONAL SIGNAL INTENSITIES

2025-06-19

Amit K Kishore , Pravin Kumar , K. Triveni +3 more | International Journal of Apllied Mathematics

Deep learning-based displacement identification and quantification for structures with surface features loss

2025-06-18

Li Zhu , Qun Xie , Yanjun Li +3 more | Mechanical Systems and Signal Processing

Investigation of the shear characteristics of snakeskin-inspired interface using discrete-element method

2025-06-18

Aidin Kahbasi , Liang Zhang , Lei Wang | Proceedings of the Institution of Civil Engineers - Geotechnical Engineering

Taking inspiration from the unique structure of snake scales, this research delves into understanding the intricacies of a snakeskin-inspired interface shearing process for geotechnical applications. This study investigates the performance … Taking inspiration from the unique structure of snake scales, this research delves into understanding the intricacies of a snakeskin-inspired interface shearing process for geotechnical applications. This study investigates the performance of three snakeskin-inspired plates modelled after Heterodon nasicus, Leptophis ahaetulla and Cerastes cerastes with varying surface textures characterized by different length-to-height (L/H) ratios, along with a smooth reference plate for comparison. To evaluate the influence of scale size and shape, the discrete-element method was employed to simulate the interface shearing process under both caudal and cranial shearing directions. The results indicate that plates with moderate L/H ratios (e.g. L/H = 1.0–1.5) achieved up to 28% higher peak shear stress compared to the smooth surface, particularly under cranial shearing. Among the profile types, the Heterodon nasicus-inspired plate exhibited the highest shear resistance and volumetric dilation, with 15–20% greater dilation than the Cerastes cerastes-inspired plate. These findings provide preliminary insights into the potential benefits of integrating snakeskin-inspired surfaces into the development of engineered foundation and anchorage systems for geotechnical applications.

Accurate dynamic phase measurement of transparent objects by the spatiotemporal phase-shifting method with polarized sensor

2025-06-17

Shien Ri , Hou Natsu | Optics & Laser Technology

Wire rope lay length measurement based on DT-CWT

2025-06-17

Peiyao Li , Guohua Cao | Measurement

Robust white light algorithm for scanning error compensation

2025-06-17

Yulan Chen , Sizepeng Zhao , Anqi Liu +2 more | Optics and Lasers in Engineering

Self-Calibration of Fused Camera Images

2025-06-16

Karsten Jacobsen | The international archives of the photogrammetry, remote sensing and spatial information sciences/International archives of the photogrammetry, remote sensing and spatial information sciences

Abstract. The standard sensor for large-format digital cameras is currently the Sony CMOS chip with approximately 14200 × 10600 pixels of 3.76 μm. Sony CMOS chips with ~ 19299 × … Abstract. The standard sensor for large-format digital cameras is currently the Sony CMOS chip with approximately 14200 × 10600 pixels of 3.76 μm. Sony CMOS chips with ~ 19299 × 12800 pixels and a pixel size of 2.81 μm will be available in near future. The very large sensors used in the DMC-3 are no longer manufactured. To achieve larger imaging systems, camera systems with multiple sub-cameras are being used instead of single cameras. The images of the sub-cameras must be fused into homogenous images. The dominant method for the image fusion is the geometric fusion of the sub-images to lower resolution overview images. To achieve this, the images are geometrical enhanced by the calibrating the sub-cameras. Theoretically, the fused, geometrical enhanced images should be free of systematic image errors. However, this must not be the case, even with thermal control of the sub-cameras, satisfying thermal camera control of the entire camera system is not possible. The standard additional parameters cannot be used for image fusion problems that do not meet the calibration of individual cameras. Therefore, a specific set of additional parameters is required for each type of fused images. It turns out that full geometric accuracy can only be achieved with such special set of additional parameters, but it is possible to reach the accuracy as for the single cameras.

Effects of vibration frequency and velocity parameters on Doppler frequency shift in laser Doppler vibrometer systems

2025-06-15

Abdurrahman Günday , Aydın Balabey , Canberk Utar +3 more | Gümüşhane Üniversitesi Fen Bilimleri Enstitüsü Dergisi

In this article, the effects of maximum velocity, vibration frequency and vibration amplitude parameters of objects on Doppler frequency shift (DFS) in Laser Doppler Vibrometer (LDV) systems using lasers at … In this article, the effects of maximum velocity, vibration frequency and vibration amplitude parameters of objects on Doppler frequency shift (DFS) in Laser Doppler Vibrometer (LDV) systems using lasers at 1064 nm and 1550 nm wavelengths have been examined. In this context, while the velocity change of the object has been obtained in the range of 0 – 1200 µm/s with the laser at 1064 nm wavelength, the DFS varied between 0 and 2255.64 Hz. On the other hand, for 1550 nm wavelength, DFS have taken the values in the range of 0 – 1548.39 Hz. Moreover, for the 1064 nm wavelength, the maximum DFS and sampling time have been obtained in the range of 295.26 – 2066.84 Hz and 6.77 – 0.96 ms, respectively, in response to the change of vibration frequency from 50 to 350 Hz. For the same values of the vibration frequency, at the wavelength of 1550 nm, the maximum DFS and sampling time have changed in the range of 202.68 – 1418.78 Hz and 9.86 – 1.41 ms, respectively. Therefore, it is observed that as the vibration frequency increases, the maximum velocity and DFS increase linearly, while the sampling time decreases logarithmically. The results show that laser systems at 1064 nm wavelength respond faster but produce higher DFS values. On the other hand, LDV systems employing lasers at 1550 nm wavelength offer lower DFS and longer sampling times. Additionally, lasers that emit light at a wavelength of 1064 nm are more sensitive to velocity changes, whereas lasers at a wavelength of 1550 nm provide more stable measurement opportunities.

A kernel function based on Gaussian surface construction for fast and high-precision extraction of centers of line-structure light

2025-06-13

Jianxin Liu , Guo Yu , Chen Zhao +2 more | Measurement Science and Technology

Abstract Line-structure light three-dimensional (3D) measurement is widely applied in the field of non-contact 3D metrology. The curve fitting method is a frequently used algorithm for extracting the center of … Abstract Line-structure light three-dimensional (3D) measurement is widely applied in the field of non-contact 3D metrology. The curve fitting method is a frequently used algorithm for extracting the center of laser stripes. With respect to the calculation of the sampling direction in the curve fitting method, this paper constructs a kernel function for solving the normal direction of the pixel-level center of the laser stripe, based on the characteristic that the line-structure light follows a Gaussian distribution in the normal direction. By calculating the sampling points within a certain range of the pixel-level center using the kernel function, the first-order and second-order derivatives at the center could be directly obtained, thereby obtaining the normal direction at the center. To enhance the robustness of the sampling data in the normal direction and the real-time processing capability, this paper proposed the calculation of adaptive sampling width and prediction based on the region of interest of the Kalman filtered image respectively. The experimental results demonstrated that the proposed method attains a spherical surface fitting accuracy of 0.0251 mm for the standard target ball. The pre-extraction speed of the stripes is increased by 228% compared to global detection, and the sub-pixel center extraction speed reaches 0.91 milliseconds per frame.

Large depth-of-field 3D measurement with multi-view fusion in MEMS-based structured light field

2025-06-13

Yupei Miao , Ziwei Wang , Xiaojie Zhang +4 more | Optics Express

An a posteriori data-driven method for phase-averaging optical measurements

2025-06-13

Enrico Amico , Sara Montagner , Jacopo Serpieri +1 more | Measurement Science and Technology

Abstract Phase-averaging is a fundamental approach for investigating periodic&#xD;and non-stationary phenomena. In fluid dynamics, these can be generated by&#xD;rotating blades such as propellers/turbines or by pulsed jets. Traditional phase-&#xD;averaging approaches … Abstract Phase-averaging is a fundamental approach for investigating periodic&#xD;and non-stationary phenomena. In fluid dynamics, these can be generated by&#xD;rotating blades such as propellers/turbines or by pulsed jets. Traditional phase-&#xD;averaging approaches often rely on synchronized data acquisition systems, which&#xD;might require high-speed cameras, light sources, and precise delay generators and&#xD;encoders, making them expensive and sometimes unfeasible. This work proposes a&#xD;a posteriori data-driven approach that reconstructs phase information from randomly&#xD;acquired uncorrelated photographic frames (snapshots) using the ISOMAP algorithm.&#xD;The technique enables accurate reordering of snapshots in the phase space and&#xD;subsequent computation of the phase-averaged flow field without the need for&#xD;synchronization. The framework was validated through numerical simulations and&#xD;experimental fluid dynamics datasets from an optical setup featuring single- and multi-&#xD;propeller configurations. The results demonstrate that the proposed method effectively&#xD;captures the periodic flow characteristics while addressing the challenges related to&#xD;synchronization and hardware limitations. Furthermore, the ability to apply this&#xD;technique to archival datasets extends its applicability to a wide range of experimental&#xD;fluid dynamics studies. This approach provides a scalable and cost-effective alternative&#xD;to traditional methods for the analysis of periodic phenomena.

A versatile framework for attitude tuning of beamlines at light source facilities

2025-06-12

Peng Cheng Li , Xueyan Bi , Z.F. Zhang +7 more | Journal of Synchrotron Radiation

Aside from regular beamline experiments at light sources, the preparation steps before these experiments are also worthy of systematic consideration in terms of automation; a representative category in these steps … Aside from regular beamline experiments at light sources, the preparation steps before these experiments are also worthy of systematic consideration in terms of automation; a representative category in these steps is attitude tuning, which typically appears in contexts like beam focusing, sample alignment etc . With the goal of saving time and human effort in both writing and using such code, a Mamba -based attitude-tuning framework is created. It supports flexible input/output ports, easy integration of diverse evaluation functions and free selection of optimization algorithms. With the help of Mamba 's infrastructure, machine learning (ML) and artificial intelligence (AI) technologies can also be readily integrated. The tuning of a polycapillary lens and of an X-ray emission spectrometer are given as examples for the general use of this framework, featuring powerful command-line interfaces (CLIs) and friendly graphical user interfaces (GUIs) that allow comfortable human-in-the-loop control. The tuning of a Raman spectrometer demonstrates more specialized use of the framework with customized optimization algorithms. With similar applications in mind, this framework is estimated to be capable of fulfilling most attitude-tuning needs. Also reported is a virtual-beamline mechanism based on easily customisable simulated detectors and motors, which facilitates both testing for developers and training for users, as well as the encapsulation of digital twins.

Frame-By-Frame Stop Motion

2025-06-12

Tom Gasek | CRC Press eBooks

Remote measurement of reinforcing bar spacing and length from an oblique photograph using a novel perspective correction technique

2025-06-12

Jun Su Park , Jiyoung Kang , Hyo Park | Computer-Aided Civil and Infrastructure Engineering

Abstract The dimensional inspection of reinforcing bars at construction sites prior to concrete pouring is essential to ensure structural integrity. However, this process has traditionally relied on manual tape measurements, … Abstract The dimensional inspection of reinforcing bars at construction sites prior to concrete pouring is essential to ensure structural integrity. However, this process has traditionally relied on manual tape measurements, which are labor‐intensive, unsafe, and prone to human error. To address these limitations, this study introduces a novel method for remotely inspecting the spacings and lengths of reinforcing bars using a single oblique photograph and a new perspective correction technique. This method transforms oblique images into vertical images using constraints based on four specific vectors that must be perpendicular to one another, thereby eliminating the need for the four‐point correspondence required by existing methods. This improvement enhances the practicality of the proposed method. A validation experiment conducted at an apartment construction site yielded a mean absolute error of 5.12 mm in measuring the spacing and length of reinforcing bars, demonstrating field‐level accuracy in compliance with American Concrete Institute 117 and the Gagemaker's Rule from US military standard 120.

Calibration method for laser-camera scanners with a motorized rotating mechanism using a hand-eye calibration framework

2025-06-12

Van-Tung Ha , Van-Phu Do , Han-Gyeol Kim +3 more | Optical Engineering

Analysis of notch strains combining electronic speckle pattern interferometry and digital image correlation

2025-06-09

Thomas Lehmann , Jörn Ihlemann | Journal of Theoretical and Applied Mechanics/Mechanika Teoretyczna i Stosowana