Based on the polynomial theory, the error propagation characteristics of the widely used N-step discrete Fourier transform (N-DFT) phase-shiftalgorithm were analyzed via theoretical analysis, under the effect of Gamm...
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Based on the polynomial theory, the error propagation characteristics of the widely used N-step discrete Fourier transform (N-DFT) phase-shiftalgorithm were analyzed via theoretical analysis, under the effect of Gamma distortion and phase detuning. The results showed that the N-DFT algorithm could not simultaneously suppress both types of error. A robust linear phase-shift (RLPS) algorithm was designed, the performance of the RLPS and 8-DFT algorithms in terms of spectral response, detuning robustness, and GS/N\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${G}_{S/N}$$\end{document} was briefly analysis by Manuel Servin method. The Simulation analysis and comparison of the results show that the RLPS algorithm could suppress both types of error simultaneously, which exhibited better stability and accuracy than N-DFT and exponential algorithms, particularly in gradient measurement stability, peak-to-valley (PV) and root-mean-square (RMS) error suppression. Moreover, a physical experiment apparatus was built to test unidirectionally inclined plane mirror and concave mirror using the RLPS, N-DFT, and exponential algorithms. The results showed that the RLPS algorithm could significantly improve the measurement stability and accuracy in the presence of detuning and without screen Gamma calibration.
Time of flight (ToF) light detection and ranging (Lidar) range finder is widely used in various applications, such as automotive driving, marine environment surveying, atmospheric observing, and physical distancing mo...
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Time of flight (ToF) light detection and ranging (Lidar) range finder is widely used in various applications, such as automotive driving, marine environment surveying, atmospheric observing, and physical distancing monitoring. The ToF Lidar offers a high-resolution range, which can be achieved by increasing the modulation frequency. However, when the modulation frequency is increased, the maximum unambiguous range tends to decrease. To overcome such a problem, we develop a novel ToF Lidar range finder based on dual-modulation frequencies switching, capable of providing an extended range while maintaining the high resolution. In the design, the modulation frequency is alternately changed between 2 and 10 MHz to modulate the intensity of the laser diode as a transmitter. We operate an avalanche photodetector as a receiver to obtain a reflection of modulated light from a target. By switching between dual-modulation frequencies, the photodetector detects two-phaseshifts, which are calculated by our phase shift algorithm. It is shown that the proposed algorithm can solve the ambiguous range problem. As proof of the concept, we experimentally demonstrate a range measurement of a target up to 55-m distance, where the ambiguous range is experienced four times if only a single modulation frequency of 10 MHz is used. Interestingly, the range ambiguity no longer appears after applying the proposed design and algorithm.
The phase-shifting method is widely used in fringe projection profilometry(FPP),The digital light projector(DLP) and charge coupled device(CCD) are generally nonlinear *** captured fringes do not have a good sinusoida...
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ISBN:
(纸本)9781510637054
The phase-shifting method is widely used in fringe projection profilometry(FPP),The digital light projector(DLP) and charge coupled device(CCD) are generally nonlinear *** captured fringes do not have a good sinusoidal property,which leads to errors in the retrieved phase *** methods to calibrate the nonlinear response of a FPP and compensate for the associated error can be classified into active methods(correction before pattern projection) and passive methods(correction after pattern projection).The basic idea of the active method to precisely obtain the input-output relation function of the projector. The passive method compensates the error in phase domain by the post-processing *** *** . presented the double three-step phaseshifting algorithm to reduce the nonlinear phase error by projecting two groups of three-step phase-shifting fringe with an initial phase offset of 60 ***,some scholars improved this *** ***. presented a method that combined the two wrapped phases to obtain the combination of the wrapped phase,it is simpler than Huang' s method because only one time phase unwrapping procedure is *** *** . combined double-step phase-shifting method and multi-frequency temporal phase unwrapping algorithm, proposed a multi-frequency inverse-phase method to realize the 3D shape measurement of the complicated *** proposed a similar *** main difference between Lei and Mao is that the operation order of double-step phase-shifting algorithm for error compensation is different. In Mao' s method,error compensation is performed in the wrapped phase map while it is done with the unwrapped phase map in Lei' s *** paper compares double-step phase-shifting algorithm,its variational algorithm (Zheng' s method,Lei' s method,Mao' s method) and phase shift algorithm with twice the number of steps for nonlinear error compensation, our study finds that these algorithms have similar effect in
A multiparty quantum key distribution protocol is proposed in this paper. The distributor uses a phaseshift operation to encode the key sequence into some EPR sequences. The participants perform a phaseshift operati...
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A multiparty quantum key distribution protocol is proposed in this paper. The distributor uses a phaseshift operation to encode the key sequence into some EPR sequences. The participants perform a phaseshift operation on the particles from Bell states according to their private keys, and t out of n participants can use the Lagrange interpolation to recover the EPR sequences. Furthermore, two cooperating participants, one from each of the two disjoint groups, can always reconstruct the original key sequence by only a single-photon measurement. Performance analysis shows that the proposed protocol is simpler and more efficient than the existing schemes.
Time-of-flight (Tof) range imaging is a new suitable choice for measurement and modeling in many different applications such as robotics, machine vision, medical imaging, multimedia and so forth. But due to the techno...
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ISBN:
(纸本)9781479921805
Time-of-flight (Tof) range imaging is a new suitable choice for measurement and modeling in many different applications such as robotics, machine vision, medical imaging, multimedia and so forth. But due to the technology's relatively new appearance on the market the knowledge of its capabilities is very low. This paper presents an uncertainty analysis for optical Tof sensors based on a four-phase-shiftalgorithm for range value calculation. The measurement uncertainty indicates the interval of the values that the quantity to be measured (in this paper range information) may assume, after all systematic biases have been corrected. The uncertainty analysis is evaluated by simulation. At the end of the paper the results are discussed.
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 phaseshifter. In this paper, the calculation the...
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ISBN:
(纸本)9780819483850
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 phaseshifter. In this paper, the calculation theory and consequence in measurement error of the phase shift algorithm are discussed. These algorithms include traditional three-phasealgorithm, traditional four-phasealgorithm, traditional five-phasealgorithm, carre algorithm, new compensating four-phasealgorithm and new compensating five-phasealgorithm. 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-phasealgorithm is immune to phase-shifting error, and its result is insensitive to Gauss noise, it can improve measurement accuracy effectively.
Registered depth and intensity data at a high frame rate, a compact design, low weight, and a reduced power consumption have motivated the increasing usage of lock-in time-of-flight (TOF) cameras in research areas suc...
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Registered depth and intensity data at a high frame rate, a compact design, low weight, and a reduced power consumption have motivated the increasing usage of lock-in time-of-flight (TOF) cameras in research areas such as computer graphics, machine vision, and robotics. The state-of-the-art practice is to use continuous wave modulation with square waves for TOF cameras. Square waves can be easily generated digitally with a high accuracy and stability using programmable logic devices. In this paper, a modulation method based on sine waves is proposed, which significantly reduces the depth distortion offset (wiggling effect) of lock-in TOF cameras. Furthermore, a model for the noise distribution in the depth image is derived. This model can predict the performance of the proposed modulation method for each pixel in real time.
Camera calibration is the most essential and usually the first step in computer vision applications. The results highly depend on the accuracy of the feature extraction. Conventional feature extraction methods suffer ...
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Camera calibration is the most essential and usually the first step in computer vision applications. The results highly depend on the accuracy of the feature extraction. Conventional feature extraction methods suffer from perspective and lens distortion. In this paper, a novel feature extraction method is proposed by using fringe patterns groups as calibration target. Each group comprises six sinusoidal, in which, three are used for calculating vertical phases and the other three for horizontal phases. A three-step phase shift algorithm is used for wrapped phase calculation. Then, feature points are detected with a 2D phase-difference pulse detection method and refinement is done by simple interpolation. Finally, camera calibration is done by using these features as control points, experimental results indicated the proposed method accurate and robust. (C) 2013 Elsevier GmbH. All rights reserved.
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 *** this paper,the calculation theory and co...
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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 *** this paper,the calculation theory and consequence in measurement error of the phase shift algorithm are *** algorithms include traditional three-phasealgorithm,traditional four-phasealgorithm,traditional five-phasealgorithm,carre algorithm,new compensating four-phasealgorithm and new compensating five-phase *** 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-phasealgorithm is immune to phase-shifting error,and its result is insensitive to Gauss noise,it can improve measurement accuracy effectively.
During the last years, time-of-flight (TOF) sensors achieved a significant impact onto research fields in machine vision. In comparison to other common 3-D sensing devices, they combine the advantages of active sensor...
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During the last years, time-of-flight (TOF) sensors achieved a significant impact onto research fields in machine vision. In comparison to other common 3-D sensing devices, 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. In this paper, a new approach is presented which increases the range calculation time by a factor of four. Experimental results show that the proposed algorithm is well suited for real-time processing of the range images of continuous wave TOF cameras.
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