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Absolute phase retrieval based on spatial ternary phase coding with circular fringe projection

OPTICS AND LASERS IN ENGINEERING 2024年 178卷

作者： Ruan, Guoshui Cao, Yiping Wu, Haitao Wei, Zhimi Li, Chengmeng Sichuan Univ Coll Elect & Informat Engn Chengdu 610065 Peoples R China

Fringe projection profilometry (FPP) based on temporal phase unwrapping (TPU) plays a vital role due to its high precision and fast speed in three-dimensional (3D) measurements. However, a fundamental contradiction arises between the necessity for numerous auxiliary patterns and the goal of enhancing measurement efficiency, particularly when ensuring a big codeword space for fringe order. Thus, a spatial ternary phase coding (STPC) method is proposed, which achieves a big codeword space by projecting just one auxiliary coding pattern while ensuring a robust decoding. By equally dividing each fringe period into several segments, ternary coding of fringe order is accomplished using an arccosine operation to code three distinct phase values within each segment. Meanwhile, circular grating is adopted due to its excellent performance in phase sensitivity, which offers a higher measuring accuracy in 3D reconstruction. Accordingly, a robust TPU is achieved by combining the introduced phase unwrapping scheme and the circle center -cosine theorem (CCCT) strategy. Furthermore, high -efficiency measurements are attained through projecting three phase -shifting circular gratings and one STPC grating, rendering it suitable for real-time measurements. Experimental results with various static objects and real-time scene demonstrate the feasibility and validity of the proposed method.

关键词： 3D measurement Fringe projection profilometry Temporal phase unwrapping phase coding Circular fringe

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Three-dimensional shape measurement based on color complementary phase coding method

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OPTICS AND LASERS IN ENGINEERING 2024年 180卷

作者： Fu, Lina Zhang, Zonghua Huang, Hong Li, Yanling Yang, Jingwen Ni, Yubo Gao, Nan Meng, Zhaozong Zhang, Guofeng Hebei Univ Technol Sch Mech Engn Tianjin 300401 Peoples R China Chongqing Univ Key Lab Optoelect Technol & Syst Educ Minist China Chongqing 400044 Peoples R China Univ Huddersfield EPSRC Adv Metrol Hub Huddersfield HD1 3DH England Xi An Jiao Tong Univ Sch Mech Engn Xian 710049 Shanxi Peoples R China

Fringe projection profilometry (FPP) has been widely studied and used in three dimensional (3D) shape measurement because of its non-contact and high accuracy. By analyzing the captured fringe patterns, phase data can be demodulated with regard to depth. However, measurement efficiency decreases as number of the projected patterns increases. Therefore, it is a challenge to improve the projection rate, while ensuring measurement accuracy. To overcome this challenge, this paper proposes a complementary encoding method to correct the jump error of the unwrapping phase based on color phase-encoded fringe projection. Meanwhile, number of the projected patterns is reduced by using color modulation technique to generate composite fringes. The 3D reconstruction results of the proposed method are verified by qualitative experiments. Moreover, effectiveness of its error correction is discussed by quantitative experiments.

关键词： 3D measurement Fringe projection profilometry phase coding Color fringe modulation

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2-D Single-Port phase coding Meta-Antenna Leveraging Frequency Diversity for Microwave Imaging

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IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS 2024年第11期23卷 3421-3425页

作者： Wei, Yifei Chen, Xinhao Liu, Baiyang Huang, Yi Duan, Chaijie Zhang, Qingfeng Southern Univ Sci & Technol Dept Elect & Elect Engn State Key Lab Opt Fiber & Cable Manufacture Techno Shenzhen 518055 Peoples R China Natl Ctr Appl Math Shenzhen NCAMS Shenzhen 518055 Peoples R China Shenzhen Technol Univ Coll Big Data & Internet Shenzhen 518118 Peoples R China Shenzhen HUAYI Med Technol Co Ltd Shenzhen Peoples R China

The diversity of the field pattern in a radiation aper-ture plays a pivotal role on the capacity enhancement of microwave imaging and sensing. Conventional methodologies typically em-ploy multiple ports to excite a 2-D aperture for frequency diver-sity enhancement. However, multiport excitation poses significant challenges for transceivers when multiple-input-multiple-output(MIMO) technology is implemented, while employing switches can result in slower imaging speed. This letter presents a single-port2-D phase coding planar meta-antenna that generates frequency diverse radiation fields, aiming to achieve single-shot high-speed microwave imaging. A prototype of meta-antenna with 13.34 lambda(0 )x 6.67 lambda(0 )aperture size is designed and fabricated for microwaveimaging within 10 GHz to 15 GHz. It achieves a spatial resolution of5mminthey-direction and 9 mm in thex-direction for experimental demonstration, which finally validates the proposed diversity-enhanced meta-antenna. The proposed meta-antenna may findwide applications in integrated communication and sensing

关键词： Imaging Frequency diversity Microwave imaging Microwave integrated circuits Microwave communication Microwave FET integrated circuits Apertures meta-antenna microwave imaging phase coding

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NLFM microwave waveform generation with increased time bandwidth product based on polarization modulation and phase coding

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OPTICAL AND QUANTUM ELECTRONICS 2022年第4期54卷 244-244页

作者： Guo, Yuxiao Wang, Muguang Mu, Hongqian Zhang, Jianyong Beijing Jiaotong Univ Minist Educ Key Lab All Opt Network & Adv Telecommun Network Inst Lightwave Technol Beijing 100044 Peoples R China

A photonic method for nonlinear frequency-modulated (NLFM) waveform generation with increased time bandwidth product (TBWP) is proposed based on polarization modulation and phase coding. A lightwave generated by a laser diode is firstly injected into a phase-coherent orthogonal lightwave generator (POLG). The POLG consists of a dual-polarization binary phase shift keying (DPBPSK) modulator and a polarization controller (PC). The DPBPSK modulator is driven by a radio frequency (RF) signal via a 90 degrees hybrid coupler. After the POLG, a pair of phase-coherent orthogonally polarized optical carriers are generated and injected into a polarization modulator (PolM) which is driven by a specially designed phase modulation signal. After another PC and a polarizer, the optical signal is detected by a photodetector and an NLFM waveform can be generated. The central frequency and bandwidth of the generated NLFM waveform can be easily adjusted by tuning the frequency of the RF signal applied to the DPBPSK modulator and the phase modulation signal applied to the PolM. The TBWP of the generated NLFM waveform can be further increased by phase coding technique. A numerical simulation is conducted to verify the proposal. The generated NLFM waveforms have a great improvement in peak-to-sidelobe ratio of the compressed pulses compared with linear frequency-modulated waveforms with the same bandwidth, duration and phase coding.

关键词： Microwave photonics Nonlinear frequency-modulated waveform phase coding Peak-to-sidelobe ratio

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Dual-chirp waveform generation and its TBWP improvement based on polarization modulation and phase coding

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OPTICS COMMUNICATIONS 2020年第0期463卷 125413-000页

作者： Li, Xuan Zhao, Shanghong Zhang, Kun Wang, Guodong Air Force Engn Univ Informat & Nav Coll Xian 710077 Peoples R China

A photonics approach to generate a phase-coded dual-chirp waveform with reconfigurable time duration, arbitrary large TBWP, flexible tuning frequency and bandwidth is proposed and demonstrated. In the scheme, one polarization modulator (PolM) is applied to modulate a repetitive parabolic waveform with an dual-wave-length optical signal, while another PolM is utilized to achieve phase coding with a Pseudorandom (PN) sequence. After balanced detection, a phase-coded dual-chirp signal with improved time-bandwidth product (TBWP) can be generated. The approach is verified by simulation. Basis dual-chirp waveforms with tunable central frequency of 20 to 30 GHz, tunable bandwidth of 1.25 to 5 GHz but fixed TBWP of 16 are generated. Then, 30-GHz central frequency, 2.5-GHz bandwidth phase-coded dual-chirp signals with phase shift of pi, TBWP of 240, 1008 and 2032 are obtained. The generated dual-chirp microwave waveform can be used in a radar system to improve its range-Doppler resolution.

关键词： Dual-chirp waveform Time-bandwidth product Polarization modulation phase coding

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3-D Shape measurement based on the unequal-period combination approach of phase coding and sinusoidal fringe

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JOURNAL OF MODERN OPTICS 2019年第21期66卷 2083-2092页

作者： Fu, Ling Gao, Dingshan Huazhong Univ Sci & Technol Sch Elect Informat & Commun Wuhan Hubei Peoples R China Huazhong Univ Sci & Technol Wuhan Natl Lab Optoelect Wuhan Hubei Peoples R China Huazhong Univ Sci & Technol Sch Opt & Elect Informat Wuhan Hubei Peoples R China

The phase coding plus sinusoidal fringe method involves embedding the codeword into the phase domain, and is suitable for different contrast variation surfaces. However, as the number of phase coding fringe cycles increase, the fringe order becomes difficult to judge, ultimately leading to phase unwrapping errors. To resolve this issue, an unequal-period combination approach of phase coding and sinusoidal fringe was proposed. The main idea of this method was to project N cycles phase coding fringe, 2N (3N, 4N ...) cycles sinusoidal fringe, and the phase coding fringe was ahead of the sinusoidal fringe. This method alleviated the difficulty in judging the fringe order and, consequently, improved measurement accuracy. Experiment results validated the efficiency and accuracy of this novel method.

关键词： 3-D shape measurement phase coding sinusoidal fringe unequal-period Fringe projection profilometry phase retrieval

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A 3D shape measurement method based on novel segmented quantization phase coding

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OPTICS AND LASERS IN ENGINEERING 2019年 113卷 62-70页

作者： Wang, Lin Chen, Yuan Han, Xu Fu, Yanjun Zhong, Kejun Jiang, Guangyu Nanchang Hangkong Univ Educ Minist China Key Lab Nondestruct Testing Nanchang 330063 Jiangxi Peoples R China

Codeword is very important in phase unwrapping based on phase coding method. Each phase coding fringe is marked with a unique codeword and then used to determine the fringe order for absolute phase retrieval. However, the traditional phase coding method is limited by the number of codeword. To overcome this problem, a segmented quantization phase coding and decoding method is proposed to achieve absolute phase retrieval without reducing the difference between adjacent quantized phase values or increasing the quantization levels. The quantized phase is modulated by a specific coding sequence and then embedded into phase coding fringe patterns, thereby greatly improving the accuracy of the decoding. The coding creates multiple segments of the whole region and each segment embeds the special coding sequence. Through the corresponding decoding algorithm, the fringe order can be obtained, and following this, the absolute phase is obtained. Simulation and experimental results demonstrate the feasibility and superiority of the proposed method to measure both a single object and multiple isolated objects.

关键词： 3D measurement phase retrieval phase coding Codeword

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A modified stepped frequency phase coding radar waveform designed for the frequency domain algorithm

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DIGITAL SIGNAL PROCESSING 2019年 88卷 101-115页

作者： Saleh, Mahdi Omar, Samir-Mohamad Grivel, Eric Bazzi, Oussama Bordeaux Univ CNRS Bordeaux INP ENSEIRBMATMECAIMSUMR 5218 Talence France Lebanese Univ Fac Sci 1 Dept Phys & Elect Beirut Lebanon Int Univ Beirut BIU Sch Engn CCE Dept Beirut Lebanon

A great deal of interest has been paid to enhance the radar range resolution for the last decades. One of the techniques is to construct a waveform combining inter-pulse and intra-pulse modulations. In this paper, stepped frequency (SF) waveform is used to represent the former, whereas phase coding (PC) is considered for the latter. To obtain the high-resolution range profile (HRRP) of a target induced by an SF waveform at the receiver, one of the approaches is the frequency domain (FD) algorithm. It has been successfully applied with SF linear frequency modulation waveforms. However, based on our investigations, processing the SFPC waveform with the FD algorithm does not lead to the performance, in terms of peak sidelobe ratio (PSLR) and integrated sidelobe ratio (ISLR), of the single-carrier phase coding (SCPC) waveform processed with a matched filter (MF). To overcome these drawbacks, we propose to split the spectrum of a phase coded pulse into a predetermined number of portions, and then to successively transmit the time-domain transformed versions of these various portions. The received echoes are then processed with a modified version of the FD algorithm. Our analysis and simulations show that the proposed waveform can be characterized by a PSLR and an ISLR close to those of the SCPC processed with MF in some scenarios. (C) 2019 Elsevier Inc. All rights reserved.

关键词： Stepped frequency waveforms phase coding Intra-pulse modulation Peak sidelobe ratio FD algorithm

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Combined phase-Rate coding by Persistently Active Neurons as a Mechanism for Maintaining Multiple Items in Working Memory in Humans

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NEURON 2020年第2期106卷 256-+页

作者： Kaminski, Jan Brzezicka, Aneta Mamelak, Adam N. Rutishauser, Ueli Cedars Sinai Med Ctr Dept Neurosurg 8700 Beverly Blvd Los Angeles CA 90048 USA SWPS Univ Social Sci & Humanities Inst Psychol PL-03815 Warsaw Poland Cedars Sinai Med Ctr Dept Neurol 8700 Beverly Blvd Los Angeles CA 90048 USA Cedars Sinai Med Ctr Ctr Neural Sci & Med Dept Biomed Sci 8700 Beverly Blvd Los Angeles CA 90048 USA CALTECH Div Biol & Biol Engn 1200 E Calif Blvd Pasadena CA 91125 USA

Maintaining multiple items in working memory (WM) is central to human behavior. Persistently active neurons are thought to be a mechanism to maintain WMs, but it remains unclear how such activity is coordinated when multiple items are kept in memory. We show that memoranda-selective persistently active neurons in the human medial temporal lobe phase lock to ongoing slow-frequency (1-7 Hz) oscillations during WM maintenance. The properties of phase locking are dependent on memory content and load. During high memory loads, the phase of the oscillatory activity to which neurons phase lock provides information about memory content not available in the firing rate of the neurons. We provide a computational model that reveals that inhibitory-feedback-mediated competition between multiple persistently active neurons reproduces this phenomenon. This work reveals a mechanism for the active maintenance of multiple items in WM that relies on persistently active neurons whose activation is orchestrated by oscillatory activity.

关键词： working memory theta oscillations human single-neuron persistent activity local field potentials phase locking phase coding hippocampus amygdala

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Effects of phase coding on Doppler Spectra in PPAR Weather Radar

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IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING 2018年第4期56卷 2043-2065页

作者： Ivic, Igor R. Univ Oklahoma Cooperat Inst Mesoscale Meteorol Studies Norman OK 73072 USA NOAA OAR Natl Severe Storms Lab Norman OK 73072 USA

One option for the improvement of weather radar technology is the use of dual-polarized phased-array radar for weather observations. Several risk factors on this path have been identified and one of the most important ones is the existence of significant cross-polar patterns inherent to the phased-array antenna. These antenna patterns induce cross-coupling between returns from the two orthogonal radiation planes, which results in the biases of polarimetric variable estimates. Furthermore, the inductive and capacitive coupling in hardware behind the antenna may exacerbate the cross-coupling effects. This presents a formidable challenge because sufficient cross-polar isolation is difficult to achieve by the antenna hardware alone. Hence, additional approaches are required to reduce the biases due to cross-coupling. One proposed technique is a 180 degrees pulse-to-pulse phase change of signals injected in either the horizontal or vertical ports of the transmission elements. This approach was analyzed for signals processed in the time domain but its effects in the frequency domain have not been investigated. Herein, these effects are considered in the presence of nondepolarizing scatterers.

关键词： phase coding phased-array radar (PAR) radar polarimetry radar signal processing weather radar

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