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Fast and robust online three-dimensional measurement based on feature correspondence

OPTICAL ENGINEERING 2021年第7期60卷 074101-074101页

作者： Wu, Haitao Cao, Yiping An, Haihua Li, Yang Li, Hongmei Xu, Cai Sichuan Univ Dept Optoelect Chengdu Sichuan Peoples R China East China Univ Technol Sch Sci Nanchang Jiangxi Peoples R China Chengdu Normal Univ Coll Phys & Engn Chengdu Sichuan Peoples R China

Online three-dimensional (3D) measurement plays an important role in industry. When phase-shifting profilometry is employed in online 3D measurement, pixel matching is an important step to keep objects at the same coordinate value. However, the correlation operation and marker feature matching algorithms may take a long time, increasing the complexity. So a fast and robust online 3D measurement based on feature correspondence is proposed. In this method, only one frame of the sinusoidal fringe pattern is projected onto the measured object, and image correction technique is employed to rectify pixel size. Then five frames of deformed patterns with equivalent displacement are captured by the camera, and the corresponding modulation patterns are extracted. The oriented fast and rotated brief feature algorithm is used to extract the matching pair of feature points, and the improved grid-based motion statistical feature algorithm can better eliminate the false match to achieve pixel matching. In this way, five frames of deformed patterns with an equivalent shifted-phase can be extracted. Finally, the 3D shape of the measured object is reconstructed by the five-step equivalent phase-shifting algorithm. Experimental results verify the effectiveness and feasibility of the proposed method. (C) 2021 Society of Photo-Optical Instrumentation Engineers (SPIE)

关键词： three-dimensional measurement online measurement pixel matching modulation feature correspondence phase-shifting algorithm

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Reconstruction-free fast depth segmentation via temporal orthogonal frequency fringe patterns

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OPTICS AND LASER TECHNOLOGY 2021年 137卷 106803-106803页

作者： Deng, Ji Li, Jian Feng, Hao Xiao, Yu Ding, Shumeng Han, Wenzhong Zeng, Zhoumo Tianjin Univ Sch Precis Instrument & Optoelect Engn State Key Lab Precis Measurement Technol & Instru 92 Weijin Rd Tianjin 300072 Peoples R China North China Inst Aerosp Engn Sch Mech & Elect Engn 133 Aimin East Rd Langfang 065000 Peoples R China

In many machine vision techniques, depth segmentation is a central process to segment targeted objects with abruptly changing depth into different regions for 3D data analysis. However, current techniques are limited by data-acquisition speed, computational cost, and the precision of segmentation. To overcome these challenges, this paper proposes a dynamic depth-segmentation technique that allows the segmentation of target objects into isolated depth regions without requiring three-dimensional reconstruction and background removal. Taking full advantage of the merits of the phase-shifting algorithm, singular-points theory about depth segmentation is summarized and applied to extract the segmenting lines as the markers for depth segmentation. Meanwhile, by using the proposed temporal orthogonal frequency scheme, the dynamic performance and the high-frequency components of the measured objects are both guaranteed during the computing process. Finally, a low-cost morphology-based optimization is created to solve the over-segmentation problem and enlarge the measurable dynamic range. The simulation result demonstrates the segmentation accuracy of this technique. Experimental results on objects of differing status show that the proposed approach provides satisfactory omnidirectional depth-segmentation results with high accuracy and fidelity.

关键词： Depth segmentation phase-shifting algorithm Singular-points theory Reconstruction-free

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Flexible depth segmentation method using phase-shifted wrapped phase sequences

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OPTICS AND LASERS IN ENGINEERING 2019年 122卷 284-293页

作者： Deng, Ji Li, Jian Feng, Hao Zeng, Zhoumo Tianjin Univ Sch Precis Instrument & Opto Elect Engn State Key Lab Precis Measurement Technol & Instru 92 Weijin Rd Tianjin 300072 Peoples R China

Depth segmentation has attracted much attention in fields ranging from industrial monitoring to image understanding. However, it remains difficult to segment objects positioned at different depths with high speed and high accuracy. This paper proposes a novel depth segmentation scheme based on the phase-shift invariance of the segmentation lines and a simple optimization framework that exploits simple image processing algorithms to enhance its performance in noisy environments. Without the need for precalibration or complementary cues, this approach performs depth segmentation effectively by changing the pattern sequence selectively during the step of postprocessing. First, the structural configuration and special properties of the phase-shifting algorithm are described, following which an optimization framework is established to allow data matting and labeling. Simulation and experimental results show that this approach can perform depth segmentation efficiently despite the influence of environmental noise. Moreover, the processing is of low cost, only needing to detect the intersections of discontinuities among three different wrapped phase maps. Most significantly, this method is robust to variations in environmental noise, camera exposure, and object color and texture.

关键词： Depth segmentation phase-shift invariance phase-shifting algorithm

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Random three-step phase retrieval approach based on difference map Gram-Schmidt orthonormalization and Lissajous ellipse fitting method

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OPTICS AND LASERS IN ENGINEERING 2019年第Oct.期121卷 11-17页

作者： Zhang, Yu Tian, Xiaobo Liang, Rongguang Northeast Elect Power Univ Coll Sci Inst Mat Phys Jilin 132012 Jilin Peoples R China Chinese Acad Sci Changchun Inst Opt Fine Mech & Phys State Key Lab Appl Opt Changchun 130022 Jilin Peoples R China Univ Arizona Coll Opt Sci Tucson AZ 85721 USA

To achieve high measurement accuracy with less computational time in phase-shifting interferometry, a random phase retrieval approach based on difference map Gram-Schmidt othonormalization and Lissajous ellipse fitting method (DGS-LEF) is proposed, it easy to implement and only needs three phase shifted interferograms, it doesn't need pre-filtering, moreover, the phase shift can be random except for too small relative phase shift between two adjacent interferograms, last but not least, this method is effective for the symmetrical and asymmetrical fringes. The simulations and experiments verify the correctness and feasibility of DGS-LEF.

关键词： phase-shifting algorithm Difference map Gram-Schmidt normalization Lissajous ellipse fitting phase shift Accuracy Computational time

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A Statistic Method of Project Nonlinearity Correction in Multi-frequency phase-shifting Fringe Projection Profilometry 6

A Statistic Method of Project Nonlinearity Correction in Mul...

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6th International Conference on Optical and Photonic Engineering (icOPEN)

作者： Xing, Shuo Guo, Hongwei Shanghai Univ Dept Precis Mech Engn Lab Appl Opt & Metrol Shanghai 200072 Peoples R China

ISBN: (纸本)9781510622579

In fringe projection profilometry, using multi-frequency fringe patterns allows us to determine fringe orders automatically, thus unwrapping the measured phase maps. Simultaneously, doing this provides a possibility of correcting the effects of the projector nonlinearity directly from the captured fringe patterns. This projector nonlinearity decreases the measurement accuracies by inducing errors appearing as ripple-like artifacts on the phase maps and, further, on the reconstructed 3D shape surfaces. Theoretical analysis shows that these artifacts, depending on the number of phase shifts, have multiplied frequencies higher than the fringe frequencies, and their amplitudes are dependent on the extent of the projector nonlinearity. These facts imply that, we estimate the amplitude of the artifacts from two phase maps of the fringe patterns having different frequencies, by exploiting the statistics of the differences of their phase errors. By subtracting out the artifacts from the phase maps, the effects of the projector nonlinearity on the measurement results can be suppressed significantly. Experiment results demonstrate that this proposed method offers some advantages over others, such as working without a photometric calibration, being applicable when the projector nonlinearity varies with time, and being efficient in computation.

关键词： Fringe projection profilometry phase measurement phase-shifting algorithm projector nonlinearity correction

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phase-shifting interference microscope with extendable field of measurement

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JOURNAL OF OPTICS 2018年第4期20卷 045605-045605页

作者： Lin, Shyh-Tsong Hsu, Wei-Feng Wang, Ming-Shiang Natl Taipei Univ Technol Dept Electroopt Engn 1Sec 3Chung Hsiao East Rd Taipei 10608 Taiwan

An innovative phase-shifting interference microscope aimed at extending the field of measurement is proposed in this paper. The microscope comprises a light source module, a phase modulation module, and an interferometric module, which reconstructs the micro-structure contours of samples using the five-step phase-shifting algorithm. This paper discusses the measurement theory and outlines the configuration, experimental setup, and experimental results obtained using the proposed interference microscope. The results confirm the efficacy of the microscope, achieving a standard deviation of 2.4 nm from a step height of 86.2 nm in multiple examinations.

关键词： interference microscope phase-shifting algorithm micro-structure contour field of measurement

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High-dynamic-range 3D shape measurement based on time domain superposition

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MEASUREMENT SCIENCE AND TECHNOLOGY 2019年第6期30卷 065004-065004页

作者： Zhang, Liang Chen, Qian Zuo, Chao Tao, Tianyang Zhang, Yuzhen Feng, Shijie Nanjing Univ Sci & Technol Jiangsu Key Lab Spectral Imaging & Intelligent Se Nanjing 210094 Jiangsu Peoples R China Nanjing Univ Sci & Technol Smart Computat Imaging SCI Lab Nanjing 210094 Jiangsu Peoples R China

Fringe projection is a widely used approach for 3D shape measurements. However, it is ineffective for scenarios with a wide range of reflectivity. In this paper, we propose a technique that can measure high-dynamic-range surfaces without changing camera exposure or projected light intensity. With the strategy of time domain superposition, we can use noisy fringe images to recover phase and geometric shapes accurately for low-reflection and high-reflection regions. The measurement accuracy of low-reflection regions obtained by the proposed method is about three times higher than that of the traditional phase-shifting method. Both simulations and experiments are performed to verify the proposed method.

关键词： fringe projection profilometry phase-shifting algorithm high dynamic range 3D reconstruction time domain superposition

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Enhanced dual-frequency pattern scheme based on spatial-temporal fringes method

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JOURNAL OF MODERN OPTICS 2018年第12期65卷 1495-1506页

作者： Wang, Minmin Zhou, Canlin Si, Shuchun Lei, Zhenkun Li, Xiaolei Li, Hui Li, YanJie Shandong Univ Sch Phys Jinan Shandong Peoples R China Dalian Univ Technol Dept Engn Mech Dalian Peoples R China Hebei Univ Technol Sch Mech Engn Tianjin Peoples R China Jinan Univ Sch Civil Engn & Architecture Jinan Shandong Peoples R China

One of the major challenges of employing a dual-frequency phase-shifting algorithm for phase retrieval is its sensitivity to noise. Yun et al proposed a dual-frequency method based on the Fourier transform profilometry, yet the low-frequency lobes are close to each other for accurate band-pass filtering. In the light of this problem, a novel dual-frequency pattern based on the spatial-temporal fringes (STF) method is developed in this paper. Three fringe patterns with two different frequencies are required. The low-frequency phase is obtained from two low-frequency fringe patterns by the STF method, so the signal lobes can be extracted accurately as they are far away from each other. The high-frequency phase is retrieved from another fringe pattern without the impact of the DC component. Simulations and experiments are conducted to demonstrate the excellent precision of the proposed method.

关键词： phase retrieval profilometry phase-shifting algorithm Fourier transform dual-frequency pattern

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Repeatability study on different interference systems

Repeatability study on different interference systems

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Conference on Optical Precision Manufacturing, Testing, and Applications / International Symposium on Optoelectronic Technology and Application / Annual Conference of the Chinese-Society-for-Optical-Engineering (CSOE)

作者： Zhang, Linghua Zhang, Bo Han, Sen Tang, Shouhong Zhuang, Chengjin Univ Shanghai Sci & Technol Shanghai Peoples R China Suzhou Univ Sci & Technol Suzhou Peoples R China Suzhou H&L Instruments LLC Suzhou Peoples R China

ISBN: (数字)9781510623378

ISBN: (纸本)9781510623378

Interferometry repeatability is an important indicator for measuring instrumentation and test results. The precondition of improving the detection accuracy is to ensure high-precision repeatability, so high-precision repeatability is one of the most important indicators in precision detection. In the Fizeau interferometer, common light paths are used for the distances from the laser light source to the reference surface, from the reference surface to the detector CCD, and the reference beam and the test beam. However, the strict sense of the co-beam does not exist, and it is not absolute ideal that reference plane has high-precision surface. The test beam reflects from the measured surface will have a certain angular deviation from the reference beam. If so, it may make the reference beam and the test beam reach the CCD detector along different optical paths and generate return error accordingly. And finally it makes effects in sampling and wave surface reproduction. Therefore, using the Zygo GPI system, the 4D system and the H&L system to make research on the same optical platform for relative interferometry repeatability comparison, ensuring that the cavity length is the same, and the standard reference mirror and the tested mirror is the same. Measurements were repeated 50 times for zero-stripes, five-stripes, and ten-stripes. The PV values and RMS values of the 50 measurements make mean processing to reflect the measurement repeatability. Further repeatability error analysis is performed on the phase shift algorithm and PZT phase shifter.

关键词： repeatability phase-shifting algorithm PZT phase shifter

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Modified Fourier transform profilometry based on digital time-multiplexing technique 6

Modified Fourier transform profilometry based on digital tim...

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6th International Conference on Optical and Photonic Engineering (icOPEN)

作者： Zhou, Canlin Li, XiaoLei Si, Shuchun Lei, Zhenkun Li, YanJie Shandong Univ Sch Phys Jinan 250100 Shandong Peoples R China Hebei Univ Technol Sch Mech Engn Tianjin 300130 Peoples R China Dalian Univ Technol Dept Engn Mech Dalian 116024 Peoples R China Jinan Univ Sch Civil Engn & Architecture Jinan 2250020 Shandong Peoples R China

ISBN: (纸本)9781510622579

In order to avoid frequency aliasing, improve the spatial resolution of the phase map in Fourier transform Profilometry(FTP), an approach based on the digital time-multiplexing technique is proposed to remove the background component from the deformed fringe pattern. Firstly, a sinusoidal fringe pattern is projected onto the tested object by digital-light-processing(DLP) projector, the fringe pattern modulated by the object's surface is captured by a CCD camera. Secondly, apply Fourier transform to the captured fringe pattern to obtain the spectrum. Thirdly, rotate the specimen's fringe pattern 90-deg to obtain the rotated fringe pattern, then obtain the new spectrum corresponding to the rotated fringe pattern. Fourthly, the new spectrum is subtracted from the original spectrum, clip the negative going values in the resultant spectrum by digital manipulation. Fifthly, filter out the first-order spectrum from the resultant spectrum by the band filter, apply inverse Fourier transform to the selected spectrum to obtain complex fields, then retrieve the phase, unwrap the wrapped phase map by the phase unwrapping algorithm. Finally, the simulation and experimental evaluations are conducted to prove the validity and performance of the proposed method. The results are analyzed and compared with those of the conventional method. The effectiveness and superiority of the proposed method have been demonstrated and verified.

关键词： phase-shifting algorithm Fourier transform phase measuring profilometry(PMP) filtering

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