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Optimized phase-coding method for absolute phase retrieval based on K-means algorithm

JOURNAL OF MODERN OPTICS 2021年第6期68卷 303-310页

作者： Cai, Bolin Shen, Yuan Wu, Jun Yang, Yu Wang, Yuwei Wang, Mengyu Chen, Xiangcheng Zhang, Lei Wang, Keyi Anhui Univ Sch Internet Hefei Peoples R China Univ Sci & Technol China Dept Precis Machinery & Precis Instrumentat Hefei Peoples R China Wuhan Univ Technol Sch Automat Wuhan Peoples R China Anhui Agr Univ Coll Engn Hefei Peoples R China

The phase-coding method for absolute phase measurement possesses a strong robustness because its codewords are encoded into phase domain rather than intensity. However, a misalignment problem arises between fringe order and wrapped phase in this method owing to random noises and image blurring, especially in the high-frequency fringes situation. Therefore, the measurement result is unavailable. To overcome this problem, an optimized phase-coding algorithm is proposed in the study. We use the sinusoidal patterns to generate two opposite binary masks, which can locate half of each codeword. Then, the K-means algorithm is used to correct the codewords errors. The accurate fringe order is obtained by merging two halves of codewords and the absolute phase is recovered afterward. The used method is experimentally verified by an established measurement system, and the results show the proposed method is robustness and efficiency.

关键词： phase measurement phase-coding fringe order codewords

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Two-Digit phase-coding Strategy for Fringe Projection Profilometry

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IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT 2021年 70卷 1-9页

作者： Chen, Xiangcheng Wu, Jun Fan, Ruimei Liu, Qing Xiao, Yongxin Wang, Yuwei Wang, Yajun Wuhan Univ Technol Sch Automat Wuhan 430070 Peoples R China Xian Jiao Tong Liverpool Univ Dept Elect & Elect Engn Suzhou 215123 Peoples R China Anhui Agr Univ Coll Engn Hefei 230036 Peoples R China Sichuan Univ Dept Optoelect Chengdu 610065 Peoples R China

phase-coding methods have been widely used for three-dimensional (3-D) shape measurement, which use sinusoidal phase-shifting patterns to recover wrapped phase and the stair phase-coding patterns to determine the fringe order. However, due to the system nonlinearity, random noises, and image blurring, the total number of codewords that can be used is limited. In order to increase the number of codewords, this article presents a two-digit phase-coding (TDPC) strategy, in which each fringe of the sinusoidal phase-shifting patterns corresponds to a two-digit codeword encoded in the phase-coding patterns. In this way, more codewords can be generated without increasing additional patterns. Experiments of the cup and sculptures have been carried out, and the results confirm that the TDPC method can recover the 3-D shape of objects more robustly. Meanwhile, the precision experiment of a standard ball proves the high accuracy of the proposed method.

关键词： 3-D shape measurement fringe order phase-coding phase-shifting two-digit codeword

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Two-plus-two fringe projection profilometry based on phase-shifted coding

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SCIENTIFIC REPORTS 2024年第1期14卷 1-11页

作者： Zhang, Hechen Zhou, Jin Jia, Dan Huang, Jinlong Yuan, Jin Chinese Acad Sci Inst Opt Elect Chengdu 610207 Peoples R China

In fringe projection profilometry based on temporal phase unwrapping, determining a fringe order map commonly requires a large number of fringes. To reduce the fringe number, this paper proposes a concise absolute phase retrieval algorithm just by projecting four fringes. The first two orthogonal fringes with relatively large frequency can collect reliable height information. The second two fringes are designed the same as the first two, but the only difference is that each 2 pi-phase of them is shifted by a unique amount, which can robustly label a large number of fringe orders. For decoding the fringes, we develop an average intensity one-time extraction algorithm, which allows for the rapid acquisition of the two pairs of alternating current components. From this, the wrapped phase containing height information and the stair-coded phase providing fringe orders can be directly extracted by arctangent operation in a point-to-point manner. Furthermore, we also develop a universal fringe order correction algorithm that can simultaneously correct the common errors and the misalignment between the wrapped phase and fringe orders. Experiment results demonstrate that this method achieves comparable accuracy and adaptability to the phase-coding method, while utilizing two fewer fringes.

关键词： 3D surface measurement Fringe projection profilometry Absolute phase retrieval phase-coding Fringe order correction

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Shared and task-specific phase coding characteristics of gamma- and theta-bands in speech perception and covert speech

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SPEECH COMMUNICATION 2023年第1期147卷 63-73页

作者： Moon, Jae Chau, Tom Univ Toronto Holland Bloorview Kids Rehabil Hosp Bloorview Res Inst Inst Biomed Engn 150 Kilgour Rd East York ON M4G 1R8 Canada

Covert speech is the mental imagery of speaking. This task has gained increasing attention to understand the nature of thought and produce decoding methods for brain-computer interfaces. Building on previous work, we sought to delineate and compare further the potential roles of O and y oscillations in covert speech and speech perception. Using 64-channel EEG recordings of two words and rest and employing measures of phase alignment, we found significant differential engagement of O oscillations and shared phase alignment profiles for the y-band across tasks. Our findings appear to suggest that the O and y oscillations subserve, respectively, distinct and shared encoding processes between the two tasks. Our findings can contribute to the evolving discussion regarding the similarities between output and input-based speech representations and suggests that a transferable model between the two tasks may be feasible which can lead to the development of more user-friendly covert speech brain-computer interfaces.

关键词： EEG Neural oscillation phase-coding Active sensing Covert speech Speech perception Brain-computer interface

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COMPARISON OF phase-coding METHODS FOR ABSOLUTE phase RETRIEVAL

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MECHATRONIC SYSTEMS AND CONTROL 2022年第1期50卷 37-48页

作者： Zhou, Dawei Wu, Jun Chen, Xiangcheng Zuo, Zhaolu Kong, Deyi Naval Univ Engn Dept Informat Secur Wuhan Peoples R China Wuhan Univ Technol Sch Automat Wuhan Peoples R China Chinese Acad Sci Hefei Inst Phys Sci Hefei Peoples R China

Fringe projection profilometry (FPP) techniques have seen tremendous growths in many fields including machine vision, industrial engineering and medical imaging, due to the obvious superiorities of non-contact, low-cost, high-precision, fast-speed and full-field acquisition. Three-dimensional (3D) shapes are generally reconstructed by recovering the absolute phase of the deformed fringes. phase-coding methods have widely been used for absolute phase retrieval during the past few years due to their high robustness. This paper reviews the phase-coding-based absolute phase-retrieval methods, discusses challenging issues and proposes further research directions to advance phase-coding methods.

关键词： Fringe projection profilometry phase-coding absolute phase retrieval 3D shape measurement

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Dynamic three-dimensional shape measurement with a complementary phase-coding method

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OPTICS AND LASERS IN ENGINEERING 2020年第0期127卷 105982-000页

作者： Wang, Yuwei Liu, Lu Wu, Jun Song, Xiaokai Chen, Xiangcheng Wang, Yajun Anhui Agr Univ Coll Engn Hefei 230036 Peoples R China Anhui Prov Engn Lab Intelligent Agr Machinery & E Hefei 230036 Peoples R China Wuhan Univ Technol Sch Automat Wuhan 430070 Peoples R China Wuhan Univ State Key Lab Informat Engn Surveying Mapping & R Wuhan 430079 Peoples R China

The traditional phase-coding (TPC) method has been widely used for three-dimensional (3D) shape measurement. However, the fringe order determined from the coding patterns cannot be precisely aligned with the wrapped phase calculated from the sinusoidal patterns when measuring dynamic objects. Consequently, phase unwrapping errors will occur around the 2 pi phase jumps of the wrapped phase. To address this problem, the present work proposes a complementary phase-coding (CPC) method for dynamic 3D shape measurement. Specifically, the projection of the sinusoidal and coding patterns forms a cycle and the se patterns are shifted by a half-period between even and odd cycles. Combining two fringe orders of adjacent even and odd cycles, the absolute phase map can be correctly recovered. Moreover, to improve the measurement speed, all 8-bit gray patterns are converted into 1-bit binary patterns by a binary dithering technique. Both simulations and experiments demonstrate the robustness and efficiency of the proposed method.

关键词： phase-coding Shape measurement phase unwrapping Fringe order

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Absolute phase retrieval via color phase-coding

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OPTIK 2017年 140卷 1056-1062页

作者： Cheng, Teng Du, Qingyu Jiang, Yaxi Zhu, Xingkui Hefei Univ Technol Sch Automot & Transport Engn Hefei 230009 Peoples R China Beihang Univ Sch Comp Sci & Technol Beijing 230009 Peoples R China

phase-coding method that embeds codewords into phase rather than intensity performs well for absolute phase retrieval. However, this method becomes instable when dealing with a large number of codewords. This paper designs three color phase-coding fringes to determine the fringe order pixel by pixel. Specifically, six groups of N-stairs are encoded into three coding fringes, and each group is endowed with a different color to eliminate ambiguity between groups. Such that three additional fringes can generate more than 6N codewords by combining the color and phase information. Experiment results confirmed the validity of the proposed method. (C) 2017 Elsevier GmbH. All rights reserved.

关键词： phase-coding Codeword phase retrieval Fringe order

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A modified phase-coding method for absolute phase retrieval

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OPTICS AND LASERS IN ENGINEERING 2016年 87卷 97-102页

作者： Xing, Y. Quan, C. Tay, C. J. Natl Univ Singapore Dept Mech Engn 9 Engn Dr 1 Singapore 117576 Singapore

Fringe projection technique is one of the most robust tools for three dimensional (3D) shape measurement. Various fringe projection methods have been proposed for addressing different issues in profilometry and phase-coding is one such technique employed to determine fringe orders for absolute phase retrieval. However this method is prone to fringe order error, while dealing with high-frequency fringes. This paper studies phase error introduced by system non-linearity in phase-coding and provides a mathematical model to obtain the maximum number of achievable codewords in a given scheme. In addition, a modified phase-coding method is also proposed for phase error compensation. Experimental study validates the theoretical analysis on the maximum number of achievable codewords and the performance of the modified phase-coding method is also illustrated. (C) 2016 Elsevier Ltd. All rights reserved.

关键词： Fringe projection phase-coding phase-shifting System non-linearity phase error compensation

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FPGA based digital phase-coding quantum key distribution system

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Science China(Physics,Mechanics & Astronomy) 2015年第12期58卷 153-159页

作者： LU XiaoMing Zhang LiJun WANG YongGang CHEN Wei HUANG DaJun LI Deng WANG Shuang HE DeYong YIN ZhenQiang ZHOU Yu HUI Cong HAN ZhengFu Department of Modern Physics University of Science and Technology of China Key Laboratory of Quantum Information University of Science and Technology of China Synergetic Innovation Center of Quantum Information & Quantum Physics University of Science and Technology of China Chinese Academy of Sciences

Quantum key distribution （QKD） is a technology with the potential capability to achieve information-theoretic security. phase- coding is an important approach to develop practical QKD systems in fiber channel. In order to improve the phase-coding modulation rate, we proposed a new digital-modulation method in this paper and constructed a compact and robust prototype of QKD system using currently available components in our lab to demonstrate the effectiveness of the method. The system was deployed in laboratory environment over a 50 km fiber and continuously operated during 87 h without manual interaction. The quantum bit error rate （QBER） of the system was stable with an average value of 3.22% and the secure key generation rate is 8.91 kbps. Although the modulation rate of the photon in the derno system was only 200 MHz, which was limited by the Faraday- Michelson interferometer （FMI） structure, the proposed method and the field programmable gate array （FPGA） based electronics scheme have a great potential for high speed QKD systems with Giga-bits/second modulation rate.

关键词： quantum key distribution phase-coding digital phase modulation field programmable gate array Faraday-Michelsoninterferometer

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A phase-coding framework for SSVEP-based BCI 6

A phase-coding framework for SSVEP-based BCI

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6th International Conference on Electronics and Information Engineering (ICEIE)

作者： Yang, Qiuling Wu, Pingdong Beijing Inst Technol Beijing 100081 Peoples R China

ISBN: (纸本)9781510600294

Compared with the traditional frequency-coding mode, steady-state visual evoked potential (SSVEP)-based brain-computer interfaces (BCIs) will obtain some good aspects by using phase-coding mode. phase-coding mode should play an important role in SSVEP-based BCIs. But current research is only involved in a particular aspect of phase-coding mode or a particular method. In this situation, it makes researchers difficult to compare the various techniques described in the literature and hinders the development of the phase-coding study. In response to this situation, a common framework is suitable for the research. This paper proposes a general framework for phase-coding mode using in SSVEP-based BCIs. To validate the proposed idea, we design a SSVEP-based BCI in the light of the framework. It is shown that our framework proposed is suitable for the research of SSVEP-based BCIs.

关键词： brain-computer interface (BCI) steady-state visual evoked potential ( SSVEP) phase-coding framework

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