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Robust laser stripe extraction for three-dimensional reconstruction based on a cross-structured light sensor

APPLIED OPTICS 2017年第4期56卷 823-832页

作者： He, Leiying Wu, Shanshan Wu, Chuanyu Zhejiang Sci Tech Univ Fac Mech Engn & Automat Hangzhou 310018 Zhejiang Peoples R China

Cross-structured light sensor architecture for 3D reconstruction was established. An improved center of mass method was proposed for laser stripe extraction. For each initial laser stripe center point, the center of mass method was performed along the normal direction that was calculated using the Hessian matrix. The normal directions can be used to divide the laser stripe center points into two categories. Laser stripe extraction experiments showed that the proposed method is fast and robust. 3D reconstruction of a cylinder was used to analyze reconstruction accuracy, with relative accuracy of less than 0.15 mm. 3D reconstruction of a shoe last showed that cross-structured light sensors can obtain more abundant information than single-structured light sensors. (C) 2017 Optical Society of America

关键词： image processing algorithms Laser beams Laser light Laser materials processing Structured light Three dimensional reconstruction

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Gas detection using absorption properties of liquid crystals

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OPTICS EXPRESS 2017年第26期25卷 32532-32538页

作者： Wolowelsky, K. Gil, A. Elkabets, M. Rotschild, C. Technion Israel Inst Technol Fac Mech Engn Haifa Israel CI Syst Ltd Migdal Haemeq Israel

Optical gas imaging is critical for many applications, but its use is currently limited by complexity and cost. Here we experimentally demonstrate a low cost solution based on an alternating bispectral IR filter. This filter is based on liquid crystal having absorption lines, which overlap those of hydrocarbon gases, and depend on the orientation of the liquid crystal molecules. An alternating voltage modulates the orientation and thus the transmittance in the absorption bands, giving rise to different on-to-off intensity ratios for gases, and any clutter emission. Our demonstration of refrigerant gas R134a detection shows a high gas to clutter contrast and opens the way for using this method in many low cost applications. (C) 2017 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： Fourier transform infrared spectroscopy image processing algorithms Multispectral imaging Optical properties Refractive index Wire grid polarizers

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Spectroscopic super-resolution fluorescence cell imaging using ultra-small Ge quantum dots

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OPTICS EXPRESS 2017年第4期25卷 4240-4253页

作者： Song, Mingying Karatutlu, Ali Ali, Isma Ersoy, Osman Zhou, Yun Yang, Yongxin Zhang, Yuanpeng Little, William R. Wheeler, Ann P. Sapelkin, Andrei V. Queen Mary Univ London Sch Phys & Astron London E1 4NS England Bursa Orhangazi Univ Elect & Elect Engn TR-16310 Bursa Turkey Kings Coll London Nikon Imaging Ctr London WC2R 2LS England Queen Mary Univ London Sch Elect Engn & Comp Sci London E1 4NS England Univ Edinburgh Inst Genet & Mol Med Edinburgh EH4 2XU Midlothian Scotland Edinburgh Super Resolut Interdisciplinary Consort Edinburgh EH4 2XU Midlothian Scotland

We demonstrate a spectroscopic imaging based super-resolution approach by separating the overlapping diffraction spots into several detectors during a single scanning period and taking advantage of the size-dependent emission wavelength in nanoparticles. This approach has been tested using off-the-shelf quantum dots (Invitrogen Qdot) and in-house novel ultra-small (similar to 3 nm) Ge QDs. Furthermore, we developed a method-specific Gaussian fitting and maximum likelihood estimation based on a Matlab algorithm for fast QD localisation. This methodology results in a three-fold improvement in the number of localised QDs compared to non-spectroscopic images. With the addition of advanced ultrasmall Ge probes, the number can be improved even further, giving at least 1.5 times improvement when compared to Qdots. Using a standard scanning confocal microscope we achieved a data acquisition rate of 200 ms per image frame. This is an improvement on single molecule localisation super-resolution microscopy where repeated image capture limits the imaging speed, and the size of fluorescence probes limits the possible theoretical localisation resolution. We show that our spectral deconvolution approach has a potential to deliver data acquisition rates on the ms scale thus providing super-resolution in live systems. Published by The Optical Society

关键词： image processing algorithms Live cell imaging Optical imaging Structured illumination microscopy Three dimensional imaging Ultraviolet radiation

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High-precision lateral distortion measurement and correction in coherence scanning interferometry using an arbitrary surface

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OPTICS EXPRESS 2017年第16期25卷 18703-18712页

作者： Ekberg, Peter Su, Rong Leach, Richard KTH Royal Inst Technol Ind Metrol & Opt Prod Engn SE-10044 Stockholm Sweden Univ Nottingham Fac Engn Mfg Metrol Team Nottingham NG7 2RD England

Lateral optical distortion is present in most optical imaging systems. In coherence scanning interferometry, distortion may cause field-dependent systematic errors in the measurement of surface topography. These errors become critical when high-precision surfaces, e.g. precision optics, are measured. Current calibration and correction methods for distortion require some form of calibration artefact that has a smooth local surface and a grid of high-precision manufactured features. Moreover, to ensure high accuracy and precision of the absolute and relative locations of the features of these artefacts, requires their positions to be determined using a traceable measuring instrument, e.g. a metrological atomic force microscope. Thus, the manufacturing and calibration processes for calibration artefacts are often expensive and complex. In this paper, we demonstrate for the first time the calibration and correction of optical distortion in a coherence scanning interferometer system by using an arbitrary surface that contains some deviations from flat and has some features (possibly just contamination), such that feature detection is possible. By using image processing and a self-calibration technique, a precision of a few nanometres is achieved for the distortion correction. An inexpensive metal surface, e.g. the surface of a coin, or a scratched and defected mirror, which can be easily found in a laboratory or workshop, may be used. The cost of the distortion correction with nanometre level precision is reduced to almost zero if the absolute scale is not required. Although an absolute scale is still needed to make the calibration traceable, the problem of obtaining the traceability is simplified as only a traceable measure of the distance between two arbitrary points is needed. Thus, the total cost of transferring the traceability may also be reduced significantly using the proposed method. Published by The Optical Society under the terms of the Creative Commons Attrib

关键词： Atomic force microscopy image processing image processing algorithms Imaging systems Nanopositioning equipment Optical aberrations

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Surface topography acquisition method for double-sided near-right-angle structured surfaces based on dual-probe wavelength scanning interferometry

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OPTICS EXPRESS 2017年第20期25卷 24148-24156页

作者： Zhang, Tao Gao, Feng Jiang, Xiangqian Univ Huddersfield Huddersfield W Yorkshire England

This paper proposes an approach to measure double-sided near-right-angle structured surfaces based on dual-probe wavelength scanning interferometry (DPWSI). The principle and mathematical model is discussed and the measurement system is calibrated with a combination of standard step-height samples for both probes vertical calibrations and a specially designed calibration artefact for building up the space coordinate relationship of the dual-probe measurement system. The topography of the specially designed artefact is acquired by combining the measurement results with white light scanning interferometer (WLSI) and scanning electron microscope (SEM) for reference. The relative location of the two probes is then determined with 3D registration algorithm. Experimental validation of the approach is provided and the results show that the method is able to measure double-sided near-right-angle structured surfaces with nanometer vertical resolution and micrometer lateral resolution. (C) 2017 Optical Society of America

关键词： image processing algorithms Scanning electron microscopy Scanning probe microscopy Scanning tunneling microscopy Surface light scattering White light interferometry

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Demonstration of long-distance hazard-free wearable EEG monitoring system using mobile phone visible light communication

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OPTICS EXPRESS 2017年第2期25卷 713-719页

作者： Rachim, Vega Pradana Jiang, Yubing Lee, Hyeon-Seok Chung, Wan-Young Pukyong Natl Univ Dept Elect Engn Busan 48513 South Korea

A wearable electroencephalogram (EEG) is a small mobile device used for long-term brain monitoring systems. Applications of these systems include fatigue monitoring, mental/emotional monitoring, and brain-computer interfaces. However, the usage of wireless wearable EEG systems is limited due to the risks posed by the wireless RF communication radiation in a long-term exposure to the human brain. A novel microwave radiation-free system was developed by integrating visible light communication technology into a wearable EEG device. In this work, we investigated the system's performance in transmitting EEG data at different illuminance level and proposed an algorithm that functions at low illuminance levels for increased transmission distance. Using a 30 Hz smartphone camera, the proposed system was able to transmit 2.4 kbps of error-free EEG data up to 4 meter, which is equal to similar to 300 lux using an aspheric focus lens. (C) 2017 Optical Society of America

关键词： Analog to digital converters image processing image processing algorithms Modulation techniques Signal processing Visible light

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Single-photon three-dimensional imaging at up to 10 kilometers range

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OPTICS EXPRESS 2017年第10期25卷 11919-11931页

作者： Pawlikowska, Agata M. Halimi, Abderrahim Lamb, Robert A. Buller, Gerald S. Leonardo MW Ltd Crewe Rd North Edinburgh EH5 2XS Midlothian Scotland Heriot Watt Univ Sch Engn & Phys Sci Inst Photon & Quantum Sci Edinburgh EH14 4AS Midlothian Scotland

Depth and intensity profiling of targets at a range of up to 10 km is demonstrated using time-of-flight time-correlated single-photon counting technique. The system comprised a pulsed laser source at 1550 nm wavelength, a monostatic scanning transceiver and a singleelement InGaAs/InP single-photon avalanche diode (SPAD) detector. High-resolution three-dimensional images of various targets acquired over ranges between 800 metres and 10.5 km demonstrate long-range depth and intensity profiling, feature extraction and the potential for target recognition. Using a total variation restoration optimization algorithm, the acquisition time necessary for each pixel could be reduced by at least a factor of ten compared to a pixel-wise image processing approach. Kilometer range depth profiles are reconstructed with average signal returns of less than one photon per pixel. (C) 2017 Optical Society of America

关键词： High power lasers image processing image processing algorithms image quality Optical components Optical testing

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Exposure-fusion-based dot-grid image acquisition and recognition for sheet metal strain analysis

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APPLIED OPTICS 2017年第35期56卷 9706-9715页

作者： Shi, Bao-Quan Zhang, Li-Kun Yao, Chen-Song Du, Shu-Xing Ye, JunJie Xidian Univ Minist Educ Key Lab Elect Equipment Struct Design Xian 710071 Shaanxi Peoples R China

Dot-grid images are usually captured for grid strain analysis during sheet metal forming. Due to the strong reflective characteristic of the metallic surfaces, the recorded dot-grid images often have poor quality, low positioning accuracy, and low recognition rate. Therefore, an exposure-fusion-based dot-grid image acquisition and recognition approach is proposed. First, multiple dot-grid images are captured at different exposure levels. Subsequently, the recorded multi-exposure dot-grid images are fused into a new high-quality dot-grid image based on exposure fusion technology. Finally, a dot-grid image recognition procedure is developed to detect the dot-grids in the new dot-grid image. Both synthetic and real dot-grid images were tested to verify the performance of the novel approach. When synthetic dot-grid images were tested, the maximum positioning error was up to 6.044 pixels if they were recognized in the traditional way, whereas the maximum positioning error was reduced to 0.132 pixels if the novel approach was adopted. When real dot-grid images were tested, the lowest recognition rate is only 50.52% if they were recognized in the traditional way. Nevertheless, the recognition rate can reach about 91% if the novel approach was employed. These experimental results show the superiorities of the novel approach. (C) 2017 Optical Society of America

关键词： Digital image processing Edge detection image processing algorithms Optical measurement Speckle patterns Strain measurement

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Capillary red blood cell velocimetry by phase-resolved optical coherence tomography

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OPTICS LETTERS 2017年第19期42卷 3976-3979页

作者： Tang, Jianbo Erdener, Sefik Evren Fu, Buyin Boas, David A. Harvard Med Sch Massachusetts Gen Hosp Athinoula A Martinos Ctr Biomed Imaging Charlestown MA 02129 USA Boston Univ Dept Biomed Engn Neurophoton Ctr Boston MA 02215 USA

We present a phase-resolved optical coherence tomography (OCT) method to extend Doppler OCT for the accurate measurement of the red blood cell (RBC) velocity in cerebral capillaries. OCT data were acquired with an M-mode scanning strategy (repeated A-scans) to account for the single-file passage of RBCs in a capillary, which were then high-pass filtered to remove the stationary component of the signal to ensure an accurate measurement of phase shift of flowing RBCs. The angular frequency of the signal from flowing RBCs was then quantified from the dynamic component of the signal and used to calculate the axial speed of flowing RBCs in capillaries. We validated our measurement by RBC passage velocimetry using the signal magnitude of the same OCT time series data. (C) 2017 Optical Society of America

关键词： Dynamic light scattering image processing algorithms image quality Phase measurement Phase shift Three dimensional imaging

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Advanced Infrared Technology and Applications: introduction

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APPLIED OPTICS 2018年第18期57卷 AITA1-AITA4页

作者： Strojnik, Marija D'Acunto, Mario Rogalski, Antoni Mario D’Acunto Antoni Rogalski 10.1364/AO.57.0AITA1

This special issue of Applied Optics on Advanced Infrared Technology and Applications collects significantly expanded refereed papers presented at the conference of the same name, held in Quebec City, Canada, Sept. 27 to Sept. 30, 2017. All the authors who participated at the conference were contacted and invited to contribute to this special issue. Furthermore, the AO dedicated issue on AITA was open to contributions from other practitioners of IR, through direct contact and a call for papers published in AO. (C) 2018 Optical Society of America

关键词： Adaptive optics Diffuse reflectance spectroscopy Electron beam lithography image processing image processing algorithms Thermal infrared detectors

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