2021

• Record 49 of
  
  Title:Fringe projection profilometry with phase-coded optics
  
  Author(s):Yan, Qi(1,2); Ma, Suodong(1,2,3); Chen, Xu(1,2); Xu, Feng(1,2); Huang, Qitai(1,2)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 11899  Issue:   DOI: 10.1117/12.2601795  Published: 2021  
  Abstract:Fringe projection profilometry (FPP) is a commonly used tool in the three-dimensional (3D) measurement of diffuse objects in reverse engineering, products online detection, medical diagnosis, etc. However, due to the limited depth-of-field (DOF) of projection-imaging lenses, the contrast of captured sinusoidal fringes will decrease with the increase of defocus, which affects the high-precision acquisition of axial 3D topography. Although the lenses can be designed based on Scheimpflug principle or double-Telecentric optical path to extend the DOF, some problems such as off-Axis aberration, fixed magnification and limited field-of-view are still existing. To overcome the aforementioned drawbacks, FPP with phase-coded optics is proposed in this paper, where the captured sinusoidal fringe patterns are modulated effectively and the projection-imaging DOF of the system is greatly extended. Experimental results demonstrate the effectiveness of the proposed technique. © COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.
  Accession Number: 20215211394370
• Record 50 of
  
  Title:3D printing active variable curvature mirror research for zoom imaging
  
  Author(s):Xie, Xiaopeng(1); Xu, Liang(1); Wang, Yongjie(2); Shen, Le(3); Yang, Mingyang(4); Fan, Wenhui(1); Zhao, Hui(1)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 11895  Issue:   DOI: 10.1117/12.2601500  Published: 2021  
  Abstract:A variable curvature mirror (VCM) fabricated by 3D printing technique which is thickness optimized in structure design to reduce spherical aberration and supposed to be used in zoom imaging system is investigated. First, measurement and parameters fix of the mirror blank printed by 3D printing of AlSi10Mg are done for its precision deviation introduce by the manufacturing method. Second, elementary optical polishing is done for the purpose of Nickel plated. Fine optical polishing is applied on the VCM after the Nickel plated. Third, an actuation test experiment is built and tested by piezoelectric actuators of PI with nanometer precision and Zygo interferometer. The original surface figure accuracy of 90% radius is 2.225 λ / 0.394 λ (λ = 632.8 nm). As a result, within the ultimate testing range of the interferometer, the VCM achieve about 8.68μm deformation with the corresponding position change of actuator is 18μm, which is about 50% of it. Finally, an experiment of zoom imaging effect is done. The experiment shows that it does have effect to the zoom imaging which can compensate the defocus within 230.7μm. From the performance of the VCM at this stage, it can be used in infrared imaging. For the following work, its structure will be further optimized and the precision problems will be solved through using more proper manufacture method to improve its radius change performance during actuation process. Therefore, it can be used in visible light imaging in the future. © COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.
  Accession Number: 20215211394800
• Record 51 of
  
  Title:Hyperspectral imaging system based on fiber endoscope
  
  Author(s):Chen, Liqun(1); Chu, Yukun(1); Zhang, Chunguang(1); Wang, Hao(1); Fan, Shiyi(1); Yan, Bingxiang(1); Li, Zhuohang(1); Wang, Pengchong(2); Liu, Wenyao(1,3)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 12057  Issue:   DOI: 10.1117/12.2606991  Published: 2021  
  Abstract:Endoscopic imaging systems are widely used in non-invasive diagnosis of internal tissues in biomedical applications. The imaging clarity and resolution of current fiber-optic endoscopes is far less than that of electronic endoscopes. However, the electronic endoscope has the loss of information related to the principle of the three primary colors of image transmission, which makes the color reproduction ability poor. In order to solve this problem, this paper proposes a hyperspectral imaging system that combines acousto-optic tunable filter (AOTF) and fiber endoscope. The system can obtain images at any wavelengths and obtain spectral information of samples. The system eliminates the loss of information related to the three-color principle. In this paper, firstly, a hyperspectral imaging system based on fiber endoscope is designed, then we test the performance of the system by imaging the resolution target, and finally evaluates the imaging and spectral resolution of the system. The experimental results show that the hyperspectral imaging system based on fiber endoscope has greater advantages than a single fiber endoscope system. The imaging resolution and image contrast of the system have been further improved, and the spectral bandwidth is about several nanometers. Any filtering center wavelength in the visible light range can be quickly selected through random access or continuous tuning, which provides more auxiliary information and convenience for medical diagnosis. The additional spectral information increases the reliability of medical diagnosis based on the data provided by the fiber endoscope. © 2021 COPYRIGHT SPIE.
  Accession Number: 20215211375449
• Record 52 of
  
  Title:Research on edge enhancement of optical image based on acousto-optic filtering
  
  Author(s):Chu, Yukun(1); Chen, Liqun(1); Wang, Hao(1); Zhang, Chunguang(1); Liu, Wenyao(1,2); Wang, Pengchong(1,3); Fan, Shiyi(1); Yan, Bingxiang(1); Li, Zhuohang(1)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 12057  Issue:   DOI: 10.1117/12.2606997  Published: 2021  
  Abstract:Acousto-optic tunable filters (AOTF) are widely used in hyperspectral imaging systems as filtering devices. It has the advantages of stable structure, fast tuning and high portability. This paper report the tuning of AOTF by controlling the incident angle and obtains the relationship between the angle of the incident light and the wavelength of the diffracted light. The characteristic of angular spectrum selection of AOTF was demonstrated experimentally. A spatial filter system of acousto-optic method is designed by combining AOTF and Fourier lens. The functions which enhance imaging contrast of the system are completed by a single AOTF device. Using this system the edge enhanced image of resolution target was acquired. Different from using a diaphragm for spatial filtering, this filtering method based on acousto-optic effects is continuously adjustable, real-time and stable, and provides a new idea for enhancing the contrast of optical images. © 2021 COPYRIGHT SPIE.
  Accession Number: 20215211375450
• Record 53 of
  
  Title:RF spectrum measurement of the versatile microcavity soliton combs
  
  Author(s):Hu, Hao(1); Wang, Ruolan(1); Chen, Liao(1); Wang, Weiqiang(2); Zhang, Chi(1); Zhang, Wenfu(3); Zhang, Xinliang(1)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 11894  Issue:   DOI: 10.1117/12.2602760  Published: 2021  
  Abstract:Dissipative Kerr solitons generated in microresonators driven by a continuous wave pump laser have promise for widespread applications in spectroscopy and telecommunications. From the perspective of basic physics research, DKSs exhibit rich nonlinear phenomena and serve as a unique platform to study nonlinear physics. In this paper, an optimized all-optical radio frequency (RF) spectrum analyzer, also named frequency domain light intensity spectrum analyzer (f-LISA), is used to characterize the various stable soliton states. Results show that the optimized f-LISA achieves a measurement bandwidth of 2.2 THz and a frame rate of 20.62 MHz. Therefore, the versatile RF spectral patterns of stable two-soliton states have successfully recorded by f-LISA. More importantly, the relative azimuthal angles between two solitons within the round-Trip can be extracted by applying an inverse Fourier transform to the RF spectra, indicating that the ultra-fast and broadband RF spectral measurement enable the visualization of soliton motion. It is believed that the f-LISA can function as a powerful and useful tool to monitor the rich nonlinear dynamical phenomena such as soliton number switching in the microresonators © COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.
  Accession Number: 20215211394014
• Record 54 of
  
  Title:Histogram clustering for rapid time-domain fluorescence lifetime image analysis
  
  Author(s):Li, Yahui(1,2); Sapermsap, Natakorn(3); Yu, Jun(4); Tian, Jinshou(1,2); Chen, Yu(3); Li, David Day-Uei(5)
  Source: Biomedical Optics Express  Volume: 12  Issue: 7  DOI: 10.1364/BOE.427532  Published: July 1, 2021  
  Abstract:We propose a histogram clustering (HC) method to accelerate fluorescence lifetime imaging (FLIM) analysis in pixel-wise and global fitting modes. The proposed method's principle was demonstrated, and the combinations of HC with traditional FLIM analysis were explained. We assessed HC methods with both simulated and experimental datasets. The results reveal that HC not only increases analysis speed (up to 106 times) but also enhances lifetime estimation accuracy. Fast lifetime analysis strategies were suggested with execution times around or below 30 µs per histograms on MATLAB R2016a, 64-bit with the Intel Celeron CPU (2950M @ 2GHz). © 2021 OSA - The Optical Society. All rights reserved.
  Accession Number: 20212610574504
• Record 55 of
  
  Title:Precise dynamic characterization of microcombs assisted by an RF spectrum analyzer with THz bandwidth and MHz resolution
  
  Author(s):Wang, Ruolan(1); Chen, Liao(1); Hu, Hao(1); Zhao, Yanjing(1); Zhang, Chi(1); Zhang, Wenfu(2); Zhang, Xinliang(1)
  Source: Optics Express  Volume: 29  Issue: 2  DOI: 10.1364/OE.415933  Published: January 18, 2021  
  Abstract:The radio frequency (RF) spectrum of microcombs can be used to evaluate its phase noise features and coherence between microcomb teeth. Since microcombs possess characteristics such as high repetition rate, narrow linewidth and ultrafast dynamical evolution, there exists strict requirement on the bandwidth, resolution and frame rate of RF measurement system. In this work, a scheme with 1.8-THz bandwidth, 7.5-MHz spectral resolution, and 100-Hz frame rate is presented for RF spectrum measurement of microcombs by using an all-optical RF spectrum analyzer based on cross-phase modulation and Fabry Perot (FP) spectrometer, namely FP-assisted light intensity spectrum analyzer (FP-assisted LISA). However, extra dispersion introduced by amplifying the microcombs will deteriorate the bandwidth performance of measured RF spectrum. After compensating the extra dispersion through monitoring the dispersion curves measured by FP-assisted LISA, the more precise RF spectra of microcombs are measured. Then, the system is used to measure the noise sidebands and line shape evolution of microcombs within 2s temporal window, in which dynamic RF combs variation at different harmonic frequencies up to 1.96 THz in modulation instability (MI) state and soliton state are recorded firstly. Therefore, the improved bandwidth and resolution of FP-assisted LISA enable more precise measurement of RF spectrum, paving a reliable way for researches on physical mechanism of microcombs. © 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
  Accession Number: 20210509853124
• Record 56 of
  
  Title:Static full-Stokes fourier transform imaging spectropolarimeter capturing spectral, polarization, and spatial characteristics
  
  Author(s):Bai, Caixun(1,2); Li, Jianxin(3); Zhang, Wenfei(1); Xu, Yixuan(3); Feng, Yutao(2)
  Source: Optics Express  Volume: 29  Issue: 23  DOI: 10.1364/OE.443350  Published: November 8, 2021  
  Abstract:A static full-Stokes Fourier transform imaging spectropolarimeter incorporating a liquid-crystal polarization modulator (LPM) and birefringent shearing interferometer (BSI) is reported. It can decode the polarization information at each wavelength along the spatial dimension of a two-dimensional data array. The LPM has a high-speed time-division architecture and employs two ferroelectric liquid crystals and two wave plates to produce four polarization states, providing full-Stokes polarimetric information with a high signal-to-noise ratio. The BSI comprises two birefringent crystal plates and generates an optical path difference with good linear distribution for broadband interference, allowing a fast and high-precision spectral recovery. The optimized design of LPM and BSI are introduced in detail. Subsequently, the signal reconstruction is verified through simulations and experiments. The proposed scheme is highly efficient, exhibits a higher spectral resolution, and constitutes a compact technical approach to realize high-dimensional optical measurement. © 2021 Optical Society of America
  Accession Number: 20214611144751
• Record 57 of
  
  Title:Antireflective and superhydrophilic structure on graphite written by femtosecond laser
  
  Author(s):Lou, Rui(1,2); Li, Guangying(1,2); Wang, Xu(1); Zhang, Wenfu(1); Wang, Yishan(1); Zhang, Guodong(3); Wang, Jiang(3); Cheng, Guanghua(3)
  Source: Micromachines  Volume: 12  Issue: 3  DOI: 10.3390/mi12030236  Published: March 2021  
  Abstract:Antireflection and superhydrophilicity performance are desirable for improving the properties of electronic devices. Here, we experimentally provide a strategy of femtosecond laser preparation to create micro-nanostructures on the graphite surface in an air environment. The modified graphite surface is covered with abundant micro-nano structures, and its average reflectance is measured to be 2.7% in the ultraviolet, visible and near-infrared regions (250 to 2250 nm). The wettability transformation of the surface from hydrophilicity to superhydrophilicity is realized. Besides, graphene oxide (GO) and graphene are proved to be formed on the sample surface. This micro-nanostructuring method, which demonstrates features of high efficiency, high controllability, and hazardous substances zero discharge, exhibits the application for functional surface. © MDPI AG. All rights reserved.
  Accession Number: 20211210104091
• Record 58 of
  
  Title:A Real-Time Star Tailing Removal Method Based on Fast Blur Kernel Estimations
  
  Author(s):Hou, Yaxian(1,2,3); Zhao, Rujin(1,2,3); Ma, Yuebo(1,2,3); He, Longdong(1,2,3); Zhu, Zifa(1,2,3)
  Source: Mathematical Problems in Engineering  Volume: 2021  Issue:   DOI: 10.1155/2021/8819277  Published: 2021  
  Abstract:The number of star points and the accuracy of star centroid extraction are the key factors that affect the performance of the star sensor under high dynamic conditions. The motion blur results in the star point trailing, which consequently leads to the decline of star centroid extraction accuracy and in some cases lead to extraction failure. In order to improve the dynamic performance of the star sensor, in this work, we propose a real-time star trailing removal method based on fast blur kernel estimation. First, in order to minimize the influence of noise on parameter estimation, we use principal component analysis (PCA) in the dual-frequency spectrum domain to estimate the angle of blur kernel. In addition, an adjustable weighting method is proposed to estimate the length of blur kernel. So, we are able to quickly estimate the high-precision blur kernel based on a single degraded image. Moreover, an area filtering method based on the hyper-Laplacian prior recovery algorithm is also proposed. This algorithm quickly reconstructs the star points in the tracking windows and effectively removes the star point tailing in real time. The computational efficiency of the proposed algorithm is 5 times superior to the traditional method and 15 times superior to the existing accelerated iterative method. The experimental results show that the proposed algorithm removes the trailing star quickly and effectively, under low SNR. In addition, the proposed method effectively improves the number of extracted star points and the accuracies of star centroids. © 2021 Yaxian Hou et al.
  Accession Number: 20211010043642
• Record 59 of
  
  Title:Demonstration of an external cavity semiconductor mode-locked laser
  
  Author(s):Yuan, Meiyan(1,2); Wang, Weiqiang(1); Wang, Xinyu(1,2); Wang, Yang(1,2); Yang, Qinghua(3); Cheng, Dong(1,2); Liu, Yang(1,2); Huang, Long(1,2); Zhang, Mingran(1,2); Liang, Bo(1,2); Zhao, Wei(1,2); Zhang, Wenfu(1,2)
  Source: Optics Letters  Volume: 46  Issue: 19  DOI: 10.1364/OL.428794  Published: October 1, 2021  
  Abstract:Electrically pumped semiconductor mode-locked lasers (SMLs) are promising in a wide range of applications due to compact size, high energy efficiency, and low cost. However, the long gain interaction length increases the spontaneous emission noise. In this Letter, an external cavity structure is adopted to improve the SML noise performance, as well as the flexibility to adjust the repetition rate. Two external cavity SMLs with repetition rates of 255 MHz and 10 GHz are demonstrated. For the 10 GHz SML, the signal-noise-ratio and radio frequency linewidth of the fundamental frequency reach 81.1 dB and 40 Hz, respectively. The high performance makes the laser a promising light source for microwave and communication applications. © 2021 Optical Society of America
  Accession Number: 20213910957797
• Record 60 of
  
  Title:Frequency Comb Distillation for Optical Superchannel Transmission
  
  Author(s):Prayoonyong, Chawaphon(1); Boes, Andreas(2); Xu, Xingyuan(3); Tan, Mengxi(4); Chu, Sai T.(5); Little, Brent E.(6); Morandotti, Roberto(7); Mitchell, Arnan(2); Moss, David J.(4); Corcoran, Bill(1)
  Source: Journal of Lightwave Technology  Volume: 39  Issue: 23  DOI: 10.1109/JLT.2021.3116614  Published: December 1, 2021  
  Abstract:Optical frequency combs can potentially provide an efficient light source for multi-terabit-per-second optical superchannels. However, as the bandwidth of these multi-wavelength light sources is increased, it can result in low per-line power. Optical amplifiers can be used to overcome power limitations, but the accompanying spontaneous optical noise can degrade performance in optical systems. To overcome this, we demonstrate wideband noise reduction for comb lines using a high-Q microring resonator whose resonances align with the comb lines, providing tight optical filtering of multiple combs lines at the same time. By distilling an optical frequency comb in this way, we are able to reduce the required comb line OSNR when these lines are used in a coherent optical communications system. Through performance tests on a 19.45-GHz-spaced comb generating 71 lines, using 18 Gbaud, 64-QAM sub-channels at a spectral efficiency of 10.6 b/s/Hz, we find that noise-corrupted comb lines can reduce the optical signal-to-noise ratio required for the comb by ∼9 dB when used as optical carriers at the transmitter side, and by ∼12 dB when used as a local oscillator at the receiver side. This demonstration provides a method to enable low power optical frequency combs to be able to support high bandwidth and high-capacity communications. © 1983-2012 IEEE.
  Accession Number: 20214111016872