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Pseudo-Four-phase-shift algorithm for Performance Enhancement of 3D-TOF Vision Systems

IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT 2010年第5期59卷 1175-1181页

作者： Hussmann, Stephan Edeler, Torsten Westcoast Univ Appl Sci Dept Elect Engn & Informat Technol D-25746 Heide Germany

Time-of-flight (TOF) sensors have recently become available at reasonable prices. In comparison with stereo vision systems and laser range scanners, they combine the advantages of active sensors, providing accurate distance measurements, and camera-based systems, recording a 2-D matrix at a high frame rate. Moreover, low-cost 3-D imaging has the potential to open a wide field of additional applications and solutions in markets such as consumer electronics, multimedia, digital photography, robotics, and medical technologies. This paper focuses on the currently implemented phase-shift algorithm in this type of sensors. This paper presents a new approach that doubles the frame rate and thereby enhances the performance of photonic mixer device (PMD) TOF sensors. In the experimental section, detailed measurements are presented, and the advantages and disadvantages of the proposed algorithm in comparison with the state-of-the-art algorithm are discussed.

关键词： Optical distance measurement phase measurement phase-shift algorithm photonic mixer devices (PMDs) time-of-flight (TOF)

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An elliptic phase-shift algorithm for high speed three-dimensional profilometry

An elliptic phase-shift algorithm for high speed three-dimen...

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Conference on Image Processing - Machine Vision Applications VI

作者： Deng, Fuqin Li, Zhao Chen, Jia Deng, Jiangwen Fung, Kenneth S. M. Lam, Edmund Y. Univ Hong Kong Dept Elect & Elect Engn Imaging Syst Lab Hong Kong Hong Kong Peoples R China

ISBN: (纸本)9780819494344

A high throughput is often required in many machine vision systems, especially on the assembly line in the semiconductor industry. To develop a non-contact three-dimensional dense surface reconstruction system for real-time surface inspection and metrology applications, in this work, we project sinusoidal patterns onto the inspected objects and propose a high speed phase-shift algorithm. First, we use an illumination-reflectivity-focus (IRF) model to investigate the factors in image formation for phase-measuring profilometry. Second, by visualizing and analyzing the characteristic intensity locus projected onto the intensity space, we build a two-dimensional phase map to store the phase information for each point in the intensity space. Third, we develop an efficient elliptic phase-shift algorithm (E-PSA) for high speed surface profilometry. In this method, instead of calculating the time-consuming inverse trigonometric function, we only need to normalize the measured image intensities and then index the built two-dimensional phase map during real-time phase reconstruction. Finally, experimental results show that it is about two times faster than conventional phase-shift algorithm.

关键词： Three-dimensional image acquisition phase-shift algorithm industrial inspection surface measurements profilometry

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Performance improvement of a 3D-TOF PMD camera using a pseudo 4-phase shift algorithm

Performance improvement of a 3D-TOF PMD camera using a pseud...

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26th IEEE International Instrumentation and Measurement Technology Conference

作者： Hussmann, Stephan Edeler, Torsten Westcoast Univ Appl Sci Dept Elect Engn & Informat Technol D-25746 Heide Germany

ISBN: (纸本)9781424433520

Time-of-Flight sensors have recently become available at reasonable prices. In comparison to stereo vision system and laser range scanners they combine the advantages of active sensors providing accurate distance measurements and camera-based systems recording a 2D matrix at a high frame rate. Moreover low cost 3D imaging has the potential to open a wide field of additional applications and solutions in markets like consumer electronics, multimedia, digital photography, robotics and medical technologies. This paper focuses on the currently implemented phase-shift algorithm in this type of sensors. This paper presents a new approach which doubles the frame rate and thereby increases the performance of PMD TOF sensors. Experimental results show that the proposed algorithm is working effectively.

关键词： phase measurement phase-shift algorithm photonic mixer devices (PMD) time-of-flight (TOF)

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Methods for removal of spurious reflection effect on phase-shifting interferometry

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JOURNAL OF OPTICS A-PURE AND APPLIED OPTICS 2006年第8期8卷 617-624页

作者： Zhong, Xianghong Shanghai Inst Opt & Fine Mech Lab Informat Opt Shanghai 201800 Peoples R China

Spurious reflection is one of the troublesome problems in phase-shifting interferometry. This paper deals with the problem on the basis of a two-run-times-two-frame phase-shift algorithm, in which the phase shifts are shared out between the reference beam and the object beam. The effect of spurious reflection on phase measurement is investigated;two simple methods for removal of the effect are presented and each needs only six interferograms. Two other solutions to the spurious reflection problem are also reviewed. The simulation results obtained using these four solutions are compared. The influence of a mix of phase-shifter miscalibration and spurious reflection on phase measurement is also discussed.

关键词： spurious reflection phase retrieval phase-shift algorithm phase-shifting interferometry

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phase-shifting of correlation fringes created by image processing as an alternative to improve digital shearography

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OPTICS COMMUNICATIONS 2016年 380卷 114-123页

作者： Braga, Roberto A., Jr. Gonzalez-Pena, Rolando J. Marcon, Marlon Magalhaes, Ricardo R. Paiva-Almeida, Thiago Santos, Igor V. A. Martins, Moises Univ Fed Lavras Dept Engn BR-3037 Lavras MG Brazil Univ Valencia Unidad Biofis & Fis Med Dept Fisiol Fac Med & Odontol Valencia 46010 Spain Inst Fed Minas Gerais Dept Engn & Comp Campus Bambui IFMG Bambui MG Brazil

The adoption of digital speckle pattern shearing interferometry, or speckle shearography, is well known in many areas when one needs to measure micro-displacements in-plane and out of the plane in biological and non-biological objects;it is based on the Michelson's Interferometer with the use of a piezoelectric transducer (PZT) in order to provide the phase-shift of the fringes and then to improve the quality of the final image. The creation of the shifting images using a PZT, despite its widespread use, has some drawbacks or limitations, such as the cost of the apparatus, the difficulties in applying the same displacement in the mirror repeated times, and when the phase-shift cannot be used in dynamic object measurement. The aim of this work was to create digitally phase-shift images avoiding the mechanical adjustments of the PZT, testing them with the digital shearography method. The methodology was tested using a well-known object, a cantilever beam of aluminium under deformation. The results documented the ability to create the deformation map and curves with reliability and sensitivity, reducing the cost, and improving the robustness and also the accessibility of digital speckle pattern shearing interferometry. (C) 2016 Elsevier B.V. All rights reserved.

关键词： phase-shift algorithm Speckle interferometry Piezoelectric transducer Digital speckle pattern shearing interferometry

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Single frame correction of motion artifacts in PMD-based time of flight cameras

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IMAGE AND VISION COMPUTING 2014年第12期32卷 1127-1143页

作者： Jimenez, David Pizarro, Daniel Mazo, Manuel Univ Alcala Geintra Res Grp Madrid 28871 Spain Univ Auvergne ALCoV ISIT F-63001 Clermont Ferrand France

One of the leading time of flight imaging technologies for depth sensing is based on Photonic Mixer Devices (PMD). In PMD sensors each pixel samples the correlation between emitted and received light signals. Current PMD cameras compute eight correlation samples per pixel in four sequential stages to obtain depth with invariance to signal amplitude and offset variations. With motion, PMD pixels capture different depths at each stage. As a result, correlation samples are not coherent with a single depth, producing artifacts. We propose to detect and remove motion artifacts from a single frame taken by a PMD camera. The algorithm we propose is very fast, simple and can be easily included in camera hardware. We recover depth of each pixel by exploiting consistency of the correlation samples and local neighbors of the pixel. In addition, our method obtains the motion flow of occluding contours in the image from a single frame. The system has been validated in real scenes using a commercial low-cost PMD camera and high speed dynamics. In all cases our method produces accurate results and it highly reduces motion artifacts. (C) 2014 Elsevier B.V. All rights reserved.

关键词： Time of flight (ToF) Motion artifacts (MoArt) Photonic mixer devices (PMD) Motion flow phase-shift algorithm

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phase-shifting algorithms for nonlinear and spatially nonuniform phase shifts

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION 1997年第4期14卷 918-930页

作者： Hibino, K Oreb, BF Farrant, DI Larkin, KG CSIRO DIV APPL PHYS LINDFIELD NSW 2070 AUSTRALIA

In phase-shifting interferometry spatial nonuniformity of the phase shift gives a significant error in the evaluated phase when the phase shift is nonlinear. However, current error-compensating algorithms can counteract the spatial nonuniformity only in linear miscalibrations of the phase shift. We describe an error-expansion method to construct phase-shifting algorithms that can compensate for nonlinear and spatially nonuniform phase shifts. The condition for eliminating the effect of nonlinear and spatially nonuniform phase shifts is given as a set of linear equations of the sampling amplitudes. As examples, three new algorithms (six-sample, eight-sample, and nine-sample algorithms) are given to show the method of compensation for a quadratic and spatially nonuniform phase shift. (C) 1997 Optical Society of America.

关键词： phase measurement interferometry phase-shift algorithm nonlinear phase shift spatially nonuniform phase shift

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phase-measuring algorithms to suppress spatially nonuniform phase modulation in a two-beam interferometer

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OPTICAL REVIEW 2000年第6期7卷 543-549页

作者： Hibino, K Yamauchi, M Agcy Ind Sci & Technol Mech Engn Lab Tsukuba Ibaraki 3058564 Japan

phase modulation of presently used phase-shifting interferometers is assumed to be spatially uniform across the observing aperture. However, calibration errors or the configuration of an interferometer can cause a spatial nonuniformity in the phase modulation. Spatial nonuniformity causes a significant error in the measured phase when the phase modulator has nonlinear sensitivity. An even-order nonlinearity in the phase modulation in particular contributes to the errors. Lowest-order errors can be suppressed by adding a new symmetry to the sampling functions of the phase-shifting algorithm, however the algorithm suffers from large random noise. The random noise is shown to be decreased substantially by applying one more sampled frame to the algorithm. We derive new seven-sample and eight-sample algorithms that can compensate for a nonuniform phase shift and has much less random noise than the previous algorithm we proposed.

关键词： phase-shifting interferometry phase-shift algorithm nonlinear phase-shift spatially nonuniform phase shift

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Error-compensating phase measuring algorithms in a Fizeau interferometer

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OPTICAL REVIEW 1999年第6期6卷 529-538页

作者： Hibino, K AIST Mech Engn Lab Tsukuba Ibaraki 3058564 Japan

In phase-shifting Fizeau interferometers, nonlinear motion of the phase shifter and multiple-beam interference are the most common sources of systematic errors affecting high-precision phase measurement. A new class of algorithms with extended compensating capability for these errors is proposed. Measurement errors for the new algorithms and two groups of conventional algorithms: discrete Fourier algorithms and the Schwider-Larkin-Hibino algorithms are estimated as a function of the number of sampled images when these systematic error sources are equally dominant. It is shown that the conventional phase-measuring algorithms produce significant errors when the reflectivity of the testing surface exceeds ten percent. Also, these algorithms have an optimum number of samples at around seven with which the residual errors become minimum. The new class of algorithms shows a substantial reduction of the residual errors when the number of samples exceeds ten. There is no optimum number of samples for the new algorithms. For fewer than six samples, discrete Fourier algorithms which have no error-compensating capability for the nonlinearity of phase modulation give a minimum error.

关键词： phase measurement Fizeau interferometer interferometry phase-shift algorithm nonlinear phase-shift

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Novel Modulation of Isolated Bidirectional DC-DC Converter for Energy Storage Systems

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IEEE TRANSACTIONS ON POWER ELECTRONICS 2019年第2期34卷 1266-1275页

作者： Nguyen Anh Dung Chiu, Huang-Jen Lin, Jing-Yuan Hsieh, Yao-Ching Chen, Hui-Ting Zeng, Bo-Xiang Natl Taiwan Univ Sci & Technol Dept Elect & Comp Engn Taipei 10607 Taiwan Natl Sun Yat Sen Univ Dept Elect Engn Kaohsiung 80424 Taiwan

In this study, a novel modulation of an isolated three-phase bidirectional dc-dc converter is proposed for the high-voltage input power supply to low-voltage output energy storage systems. The wye-delta connection of the transformers is employed to reduce the voltage stress at the high side and the current stress at the low side of the transformers. Frequency control allows the output voltage regulation, and a phase-shift algorithm with a resonant tank is proposed following with the switching frequency to reduce the frequency range with the specific power. Furthermore, the zero-voltage-switching condition for all MOSFETs in the entire power range, which is the major restriction of a single-phase converter, is also discussed in this paper. The three-phase wye-delta converter significantly reduces the ripple of inductor current compared with that of a single-phase converter. A 2 kW prototype converter was built and successfully tested to verify the capability of such control modulation.

关键词： Bidirectional converter frequency modulation phase-shift algorithm three-phase wye-delta converter

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