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A Markov random field based method for removing invalid unwrapping phase points in 3D reconstruction

IET IMAGE PROCESSING 2023年第12期17卷 3477-3487页

作者： Gao, Jinfeng Wu, Fengyuan Cheng, Cheng Wu, Chengbai Zhou, Yangfan Huanghuai Univ Sch Informat Engn Zhumadian Henan Peoples R China Southeast Univ Coll Software Engn Suzhou Peoples R China Chinese Acad Sci Suzhou Inst Nanotech & Nanob SINANO Suzhou Peoples R China Ainstec Inc Suzhou Peoples R China Suzhou Centec Commun Co Ltd Suzhou Peoples R China Chinese Acad Sci Suzhou Inst Nanotech & Nanob SINANO Suzhou 215123 Peoples R China

Fringe projection profilometry is widely used in 3D structured light due to its fast speed and accuracy. However, in the process of phase unwrapping, it is easy to cause invalid points in the edges and shadows of objects, which leads to error points in 3D reconstruction. To solve this problem, we propose an invalid points removal method based on Markov random fields. Specifically, the proposed method formulates unwrapped phase and mask maps as energy functions and uses iterative methods to minimize them. Furthermore, we validate the proposed method in a monocular structured light system and compare it with existing algorithms. Results show that the proposed method effectively identifies edges and shadows while preserving valid points, and has strong robustness and correctness.

关键词： image denoising image processing phase coding

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Large aperture phase-coded diffractive lens for achromatic and 16°field-of-view imaging with high efficiency

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Chinese Physics B 2022年第7期31卷 349-360页

作者： Gu Ma Peng-Lei Zheng Zheng-Wen Hu Suo-Dong Ma Feng Xu Dong-Lin Pu Qin-Hua Wang School of Optoelectronic Science and Engineering and Collaborative Innovation Center of Suzhou Nano Science and Technology Soochow UniversitySuzhou 215006China Key Laboratory of Advanced Optical Manufacturing Technologies of Jiangsu Province and Key Laboratory of Modern Optical Technologies of Education Ministry of China Soochow UniversitySuzhou 215006China CAS Key Laboratory of Space Precision Measurement Technology Xi’an 710119China

Diffractive lenses(DLs)can realize high-resolution imaging with light weight and compact *** DLs suffer large chromatic and off-axis aberrations,which significantly limits their practical *** many achromatic methods have been proposed,most of them are used for designing small aperture DLs,which have low diffraction *** the designing of diffractive achromatic lenses,increasing the aperture and improving the diffraction efficiency have become two of the most important design ***,a novel phase-coded diffractive lens(PCDL)for achromatic imaging with a large aperture and high efficiency is proposed and demonstrated experimentally,and it also possesses wide field-of-view(FOV)imaging at the same *** phase distribution of the conventional phase-type diffractive lens(DL)is coded with a cubic function to expand both the working bandwidth and the FOV of conventional *** proposed phase-type DL is fabricated by using the laser direct writing of grey-scale patterns for a PCDL of a diameter of 10 mm,a focal length of 100 mm,and a cubic phase coding parameter of 30π.Experimental results show that the working bandwidth and the FOV of the PCDL respectively reach 50 nm and 16°with over 8%focusing efficiency,which are in significant contrast to the counterparts of conventional DL and in good agreement with the theoretical *** work provides a novel way for implementing the achromatic,wide FOV,and high-efficiency imaging with large aperture DL.

关键词： achromatic imaging diffractive lens phase coding large aperture high efficiency

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Efficient information hiding in medical optical images based on piecewise linear chaotic maps

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JOURNAL OF OPTICS-INDIA 2023年第4期52卷 1852-1866页

作者： Nasr, Marwa A. El-Shafai, Walid Abdel-Salam, Nariman El-Rabaie, El-Sayed M. El-Fishawy, Adel S. Abd El-Samie, Fathi E. Menoufia Univ Fac Elect Engn Elect & Elect Commun Engn Dept Menoufia 32952 Egypt Prince Sultan Univ Coll Engn Dept Comp Sci Secur Engn Lab Riyadh 11586 Saudi Arabia Canadian Int Coll CIC Fac Engn Elect & Commun Engn Dept Giza Egypt Princess Nourah Bint Abdulrahman Univ Coll Comp & Informat Sci Dept Informat Technol POB 84428 Riyadh 11671 Saudi Arabia

Steganography is one of the fascinating subjects for researchers. One of the recent research trends in this field is audio steganography, which depends on hiding of information in the cover file, while only the sender and the recipient know that there is a secret content. This technique achieves more information security and protects the image from unauthorized access. Based on the Short-Time Fourier Transform (STFT), this paper provides a new audio steganography technique for concealing medical images in audio files. The medical image is encrypted using a Piece-Wise Linear Chaotic Map (PWLCM)-based bit-level image encryption technique. In addition, the image is processed as a spectrogram and converted into a speech-like signal through the STFT before embedding it within the cover audio file. The proposed technique is carried out on four different medical images, and four audio files of suitable size. Furthermore, it is validated by comparing it with the works in the literature. The comparison reveals that the proposed audio steganography technique reveals a superior performance regarding the quality of encryption and confidentiality of medical images, as the pre-stage with the PWLCM provides more security, and good restoration quality as it achieves a Peak Signal-to-Noise Ratio (PSNR) of 55.25 dB, and a Mean Square Error (MSE) of 2.9x10(-6).

关键词： Audio steganography phase coding Image encryption Discrete Wavelet Transform (DWT) Piecewise Linear Chaotic Map (PWLCM) Short-Time Fourier Transform (STFT)

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Feasibility Study of Employing MIMO SFCW Radar using Doppler Division Multiple Access

Feasibility Study of Employing MIMO SFCW Radar using Doppler...

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IEEE Texas Symposium on Wireless and Microwave Circuits and Systems (WMCS)

作者： Thompson, Derek Carman, Aaron B. Li, Changzhi Texas Tech Univ Dept Elect & Comp Engn Lubbock TX 79409 USA

ISBN: (纸本)9798350349382;9798350349375

Multiple input multiple output (MIMO) radar systems have seen considerable use due to their ability to simulate a large antenna array with few physical antenna elements. The performance of microwave sensors can benefit greatly from MIMO techniques. This paper presents a simulation study to determine the feasibility of MIMO radars leveraging the stepped-frequency continuous wave (SFCW) transmit scheme and investigates the possibility of utilizing Doppler division multiple access (DDMA) for MIMO SFCW radar. Although DDMA is a well-known slow-time phase coding method to synthesize frequency division and generate orthogonal MIMO waveforms, it has not been leveraged in the context of SFCW radar. Therefore, this paper compares SFCW with the more common frequency modulated continuous wave (FMCW) technique to compare the merits and demerits of each transmit scheme. A MATLAB simulation is presented to analyze the possibility of DDMA SFCW radars.

关键词： SFCW MIMO DDMA FMCW slow-time phase coding frequency division simulation feasibility

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Photonic Generation of a Windowed phase-Coded Microwave Waveform With Suppressed Spectrum Sidelobes

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JOURNAL OF LIGHTWAVE TECHNOLOGY 2022年第20期40卷 6813-6822页

作者： Hu, Yang Chan, Erwin H. W. Wang, Xudong Feng, Xinhuan Guan, Bai-Ou Yao, Jianping Jinan Univ Inst Photon Technol Guangdong Prov Key Lab Opt Fiber Sensing & Commun Guangzhou 510632 Peoples R China Charles Darwin Univ Coll Engn IT & Environm Darwin NT 0909 Australia Univ Ottawa Sch Elect Engn & Comp Sci Microwave Photon Res Lab Ottawa ON K1N 6N5 Canada

An approach to photonic generation of a windowed binary phase-coded microwave waveform with suppressed spectrum sidelobes is proposed and demonstrated. An optical double sideband plus carrier signal with the carrier and the two sidebands being orthogonally polarized is generated by a dual-polarization quadrature phase shift keying (DP-QPSK) modulator, with the generated signal sent to a phase modulator (PM) where phase coding is performed. The PM can support phase modulation in two orthogonal polarization directions. The phase-modulated signals are projected to one polarization direction and detected at a photodetector (PD). Switching the polarity of the coding signal, a pi phase shift is introduced. Since the amplitude of the generated signal is dependent on the amplitude of the input coding signal, a windowing function is applied to the generated waveform by using a windowed input phase coding signal, to suppress the sidelobes in the spectrum of the generated microwave waveform. The key features of the proposed waveform generator include all-optical generation without the need of electronic components and optical filters, thus ensuring a wide operating frequency range. The proposed phase-coded microwave waveform generator also has the ability to switch between the fundamental and harmonic carrier frequency by controlling the modulator bias voltages. Experimental results show that, using a windowed 64-bit Gaussian pseudo-random binary sequence coding signal, a phase-coded microwave waveform is generated with the sidelobes of the spectrum largely suppressed by 20 dB and a pulse compression ratio as large as 133. Generation of binary phase-coded microwave waveforms at the 2nd harmonic carrier frequencies is also demonstrated experimentally.

关键词： Radio frequency Microwave photonics Microwave theory and techniques Encoding Microwave filters Microwave communication phase shift keying Frequency multiplication microwave photonics phase coding photonic signal generation pulse compression

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Advancing Image Classification with phase-coded Ultra-Efficient Spiking Neural Networks

Advancing Image Classification with Phase-coded Ultra-Effici...

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IEEE International Symposium on Circuits and Systems (ISCAS)

作者： Cai, Zhengyu Kalatehbali, Hamid Rahimian Walters, Ben Azghadi, Mostafa Rahimi Genova, Roman Amirsoleimani, Amirali Univ Toronto Dept Elect & Comp Engn Toronto ON Canada York Univ Dept Elect Engn & Comp Sci Toronto ON Canada James Cook Univ Coll Sci & Engn Townsville Australia

ISBN: (纸本)9798350330991;9798350331004

Conventional surrogate Back-Propagation-Through-Time learning in Spiking Neural Networks (SNN) demands excessive energy consumption when simulating over extended time intervals. Moreover, the spike encoding process necessitates intricate hardware support, thus undermining overall efficiency. Additionally, their classification accuracies fall short in comparison to artificial neural networks due to the inherent information loss in spike translation. Therefore, there is a critical need for efficient techniques that can enhance performance without compromising accuracy. In this study, we introduce a novel learning scheme that harnesses lossless phase coding. This approach allows us to achieve minimal inference latency, requiring a maximum of at most 8 simulation steps. Furthermore, our training times exhibit significant reductions when compared to previous single-spike networks. Our experimental results demonstrate that phase-SNN attains state-of-the-art accuracy levels, achieving 98.6% and 89.6% accuracies on the MNIST and Fashion-MNIST datasets, respectively.

关键词： Neural coding phase coding Spiking Neural Networks Neuromorphic Computing

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Automotive Radar Interference Mitigation Using phase-Coded FMCW Waveform 4

Automotive Radar Interference Mitigation Using Phase-Coded F...

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IEEE 4th International Symposium on Joint Communications and Sensing (JC and S)

作者： Kumbul, Utku Petrov, Nikita Vauchert, Cicero S. Yarovoy, Alexander IMEC Eindhoven Netherlands Delft Univ Technol Dept Microelect Delft Netherlands NXP Semicond Eindhoven Netherlands

ISBN: (纸本)9798350385458;9798350385441

Automotive radar interference problem between multiple radar sensors is investigated. phase-coded frequency modulated continuous wave (PC-FMCW) radar structure with low sampling and processing power demands is introduced to blindly mitigate mutual interference. The interference resiliency of the proposed structure is evaluated and compared with the conventional frequency modulated continuous wave (FMCW) automotive radar. It is demonstrated that the proposed approach is more robust to both coherent and non-coherent interference types, allowing resilience to both external interference of radars but also the self-interference in the simultaneous multiple input multiple output (MIMO) transmission.

关键词： Automotive radar Interference mitigation phase-coded FMCW phase coding Modulated chirps Mutual interference

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Multi-user underwater acoustic communication using binary phase-coded hyperbolic frequency-modulated signals

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IET COMMUNICATIONS 2022年第12期16卷 1415-1427页

作者： Zuberi, Habib Hussain Liu, Songzuo Sohail, Muhammad Zohaib Pan, Chenyu Harbin Engn Univ Acoust Sci & Technol Lab Harbin Peoples R China Harbin Engn Univ Key Lab Marine Informat Acquisit & Secur Minist Ind & Informat Technol Harbin Peoples R China Harbin Engn Univ Coll Underwater Acoust Engn 145-1 Nantong St Harbin 150001 Peoples R China Bahria Univ Elect Engn Dept Karachi Campus Karachi Pakistan

Multi-user communication traditionally uses either code division multiple access (CDMA) or time-division multiple access schemes. The chirp signals resilience to multipath and the Doppler effect makes it suitable for underwater acoustic communication. This paper presents a binary phase-coded hyperbolic frequency-modulated (BPC-HFM) for multi-user underwater acoustic communication. The proposed scheme has the advantage of both linear frequency-modulated signal, which is immune to multipath and Doppler offset, while PN sequence is encoded in such a manner that a waveform possesses either a phase shift of 0 or 180 depending upon the code which results in a unique orthogonal waveform for every user. As a result, it helps to reduce multiple access interference;in addition, the time-reversal mirror technique is used to enhance the performance of the system in the high multipath environment due to the virtue of hydro-acoustic channel. Furthermore, it uses a relatively simple matched filter-based receiver. To substantiate the robustness of the proposed multi-user waveforms three types of hydro-acoustic channels using the different numbers of multiple users are chosen for simulation and the bit error rate (BER) of the system is calculated. Furthermore, the results are compared to binary phase-coded linear frequency-modulated signal and conventional Direct sequence spread spectrum CDMA.

关键词： BPC-HFM phase shift chirp modulation multipath channels matched filter-based receiver time-reversal mirror technique underwater acoustic communication chirp signals resilience linear frequency-modulated signal Doppler offset phase coding binary codes multiuser underwater acoustic communication interference suppression hydro-acoustic channel error statistics matched filters bit error rate binary phase-coded hyperbolic frequency-modulated signals multiple access interference frequency modulation high multipath environment Doppler effect multi-access systems

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A User-Friendly SSVEP-Based BCI Using Imperceptible phase-Coded Flickers at 60Hz

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China Communications 2022年第2期19卷 1-14页

作者： Lu Jiang Weihua Pei Yijun Wang State Key Laboratory on Integrated Optoelectronics Institute of SemiconductorsChinese Academy of SciencesBeijing 100083China University of Chinese Academy of Sciences Beijing 100049China Chinese Institute for Brain Research Beijing 102206China

A brain-computer interface(BCI)system based on steady-state visual evoked potentials(SSVEP)was developed by four-class phase-coded *** elicited by flickers at 60Hz,which is higher than the critical fusion frequency(CFF),were compared with those at 15Hz and *** components in electroencephalogram(EEG)were detected using task related component analysis(TRCA)*** analysis with 17 subjects indicated that the highest information transfer rate(ITR)was 29.80±4.65bpm with 0.5s data length for 60Hz and the classification accuracy was 70.07±4.15%.The online BCI system reached an averaged classification accuracy of 87.75±3.50%at 60Hz with 4s,resulting in an ITR of 16.73±*** particular,the maximum ITR for a subject was 80bpm with 0.5s at *** the BCI performance of 60Hz was lower than that of 15Hz and 30Hz,the results of the behavioral test indicated that,with no perception of flicker,the BCI system with 60Hz was more comfortable to use than 15Hz and *** analysis revealed that SSVEP with higher signal-to-noise ratio(SNR)corresponded to better classification performance and the improvement in comfortableness was accompanied by a decrease in *** study demonstrates the feasibility and potential of a user-friendly SSVEP-based BCI using imperceptible flickers.

关键词： brain-computer interface electroencephalogram steady-state visual evoked potentials imperceptible flickers phase coding task related component analysis

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Automotive radar interference study for different radar waveform types

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IET RADAR SONAR AND NAVIGATION 2022年第3期16卷 564-577页

作者： Kumbul, Utku Uysal, Faruk Vaucher, Cicero S. Yarovoy, Alexander Delft Univ Technol Dept Microelect Bldg 36Mekelweg 4 NL-2628 CD Delft Netherlands NXP Semicond Eindhoven Netherlands

Mutual interference between different radar waveforms used in automotive radar applications is studied. The existing interference analysis is extended to a generalised radar-to-radar interference equation that covers most of the common interference scenarios for automotive radar systems. The outcome of the generalised equation is demonstrated for a number of typical scenarios where radars with different continuously transmitting waveforms are involved. The proposed equation can be used to characterise the received interference and its features by analysing the instantaneous beat frequency of the victim radar. Moreover, an interference analysis of phase-coded frequency-modulated continuous waveforms is performed and demonstrated experimentally by using real-time automotive radars for the first time in the literature. The experimental results corroborate the interference analysis of different waveforms and validate the proposed generalised interference equation under various conditions.

关键词： automotive radar phase coding radar interference waveform analysis

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