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Improving the performance of interferometric imaging through the use of disturbance feedforward

JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS image SCIENCE AND VISION 2017年第5期34卷 A10-A21页

作者： Boehm, Michael Glueck, Martin Keck, Alexander Pott, Jorrg-Uwe Sawodny, Oliver Max Planck Inst Astron Konigstuhl 17 D-69117 Heidelberg Germany Univ Stuttgart Inst Syst Dynam Waldburgstr 17-19 D-70563 Stuttgart Germany

In this paper, we present a disturbance compensation technique to improve the performance of interferometric imaging for extremely large ground-based telescopes, e.g., the Large Binocular Telescope (LBT), which serves as the application example in this contribution. The most significant disturbance sources at ground-based telescopes are wind-induced mechanical vibrations in the range of 8-60 Hz. Traditionally, their optical effect is eliminated by feedback systems, such as the adaptive optics control loop combined with a fringe tracking system within the interferometric instrument. In this paper, accelerometers are used to measure the vibrations. These measurements are used to estimate the motion of the mirrors, i.e., tip, tilt and piston, with a dynamic estimator. Additional delay compensation methods are presented to cancel sensor network delays and actuator input delays, improving the estimation result even more, particularly at higher frequencies. Because various instruments benefit from the implementation of telescope vibration mitigation, the estimator is implemented as a separate, independent software on the telescope, publishing the estimated values via multicast on the telescope's ethernet. Every client capable of using and correcting the estimated disturbances can subscribe and use these values in a feedforward for its compensation device, e.g., the deformable mirror, the piston mirror of LINC-NIRVANA, or the fast path length corrector of the Large Binocular Telescope Interferometer. This easy-to-use approach eventually leveraged the presented technology for interferometric use at the LBT and now significantly improves the sky coverage, performance, and operational robustness of interferometric imaging on a regular basis. (C) 2017 Optical Society of America

关键词： image processing algorithms image quality Large telescopes Nulling interferometry Phase shift Stellar interferometry

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Enhanced Coherent BOTDA System Without Trace Averaging

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Journal of Lightwave Technology 2017年第4期36卷 871-878页

作者： Nan Guo Liang Wang Huan Wu Chao Jin Hwa-Yaw Tam Chao Lu Liang Wang Huan Wu Chao Jin Hwa-Yaw Tam Chao Lu 871

We propose and experimentally demonstrate a scheme of a coherent Brillouin time domain analysis (BOTDA) system without any trace averaging. Assisted by a commercial integrated coherent receiver with a local oscillator generated through single sideband modulation from the same laser source, the Brillouin signals carried on a stable intermediate frequency (IF) are extracted by electrical/digital filters and then recovered to baseband by digital signal processing. This increases the signal-to-noise ratio and avoids the need of trace averaging and enables real-time signal acquisition. To eliminate the Brillouin gain fluctuation, two adjacent Brillouin time-domain traces stimulated by two sequential orthogonal pump pulses are recovered after the IF signals are detected in a real-time manner. Based on this configuration, a spatial resolution of 4 m and Brillouin frequency shift uncertainty of 1.473 MHz are realized in distributed temperature sensing over 40.63 km range. With the nonlocal means algorithm and distributed Raman amplification integrated into the system, the BFS uncertainty is enhanced to 0.843 MHz and better spatial resolution of 2 m over the same sensing fiber is achieved.

关键词： Coherent receivers Coherent systems image processing algorithms Laser sources Spatial resolution Wavelength division multiplexers

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Biophotonics - A Powerful Tool for Non-invasive and Labelfree Cell- and Tissue Screening

Biophotonics - A Powerful Tool for Non-invasive and Labelfre...

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Conference on Lasers and Electro-Optics (CLEO)

作者： Popp, Juergen Friedrich Schiller Univ Jena Inst Phys Chem Helmholtzweg 4 D-07743 Jena Germany Leibniz Inst Photon Technol Albert Einstein Str 9 D-07744 Jena Germany

In this presentation, we will highlight our recent advances in translating biophotonic approaches with special focus on linear and non-linear Raman spectroscopy towards routine clinical applications with focus on infe... 详细信息

ISBN: (纸本)9781943580279

关键词： Clinical applications image processing algorithms Laser surgery Multimodal imaging Raman spectroscopy Tissue

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Single-shot and phase-shifting digital holographic microscopy using a 2-D grating

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OPTICS EXPRESS 2016年第9期24卷 9480-9488页

作者： Yang, Taeseok Daniel Kim, Hyung-Jin Lee, Kyoung J. Kim, Beop-Min Choi, Youngwoon Korea Univ Sch Biomed Engn Seoul 136701 South Korea Korea Univ Dept Phys Seoul 136701 South Korea

We demonstrate digital holographic microscopy that, while being based on phase-shifting interferometry, is capable of single-shot measurements. A two-dimensional (2-D) diffraction grating placed in a Fourier plane of a standard in-line holographic phase microscope generates multiple copies of a sample image on a camera sensor. The identical image copies are spatially separated with different overall phase shifts according to the diffraction orders. The overall phase shifts are adjusted by controlling the lateral position of the grating. These phase shifts are then set to be multiples of pi/2. Interferograms composed of four image copies combined with a parallel reference beam are acquired in a single shot. The interferograms are processed through a phase-shifting algorithm to produce a single complex image. By taking advantage of the higher sampling capacity of the in-line holography, we can increase the imaging information density by a factor of 3 without compromising the imaging acquisition speed. (C) 2016 Optical Society of America

关键词： Diffraction gratings Holographic microscopy image processing image processing algorithms Phase shift Phase shifting interferometry

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Speckle-suppressed full-field imaging through a scattering medium using a supercontinuum

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OPTICS EXPRESS 2016年第23期24卷 26338-26343页

作者： Zheng, Yipeng Si, Jinhai Tan, Wenjiang Ren, Yu Hu Tong, Junyi Hou, Xun Xi An Jiao Tong Univ Sch Elect & Informat Engn Key Lab Phys Elect & Devices Shannxi Key Lab InformatPhoton TechMinist Educ Xianning Xilu 28 Xian 710049 Peoples R China Xian Univ Technol Dept Appl Phys Xian 710048 Peoples R China

We demonstrate speckle-suppressed full-field imaging through a scattering medium using incoherent supercontinuum (SC) illumination. The patterns in images obtained using SC illumination were found to be more easily identifiable than those in images acquired using coherent direct laser illumination due to the speckle suppression. Even when the optical depth reached 12.3, the patterns remained identifiable. As one of the potential applications, we also demonstrated the imaging for a high-pressure diesel spray using SC illumination. (C) 2016 Optical Society of America

关键词： Digital image processing image processing algorithms Imaging systems Optical depth Speckle noise Speckle patterns

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Investigation on slice direction dependent detectability of volumetric cone beam CT images

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OPTICS EXPRESS 2016年第4期24卷 3749-3764页

作者： Han, Minah Lee, Changwoo Park, Subok Baek, Jongduk Yonsei Univ Sch Integrated Technol Inchon South Korea Yonsei Univ Yonsei Inst Convergence Technol Inchon South Korea US FDA Silver Spring MD USA

We investigate the detection performance of transverse and longitudinal planes for various signal sizes (i.e., 1 mm to 8 mm diameter spheres) in cone beam computed tomography (CBCT) images. CBCT images are generated by computer simulation and images are reconstructed using an FDK algorithm. For each slice direction and signal size, a human observer study is conducted with a signal-known-exactly/background-known-exactly (SKE/BKE) binary detection task. The detection performance of human observers is compared with that of a channelized Hotelling observer (CHO). The detection performance of an ideal linear observer is also calculated using a CHO with Laguerre-Gauss (LG) channels. The detectability of high contrast small signals (i.e., up to 4-mm-diameter spheres) is higher in the longitudinal plane than the transverse plane. It is also shown that CHO performance correlates well with human observer performance in both transverse and longitudinal plane images. (C) 2016 Optical Society of America

关键词： Computer simulation image processing algorithms image quality image quality assessment Imaging systems Reconstruction algorithms

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Controlled angular and radial scanning for super resolution concentric circular imaging

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OPTICS EXPRESS 2016年第20期24卷 22581-22595页

作者： Du, Xian Anthony, Brian MIT Lab Mfg & Prod 77 Massachusetts Ave Cambridge MA 02139 USA

Poor motion estimation and subsequent registration are detrimental to super-resolution (SR). In this paper, we present a camera sampling method for achieving SR in concentric circular trajectory sampling (CCTS). Using this method, we can precisely control regular radial and angular shifts in CCTS. SR techniques can be subsequently applied ring by ring in radial and angular dimensions. Not only does the proposed camera sampling method eliminate the transient behavior and increases the sampling speed in CCTS, it also preserves the SR accuracy. Our experimental results demonstrate that our approach can accurately discriminate SR pixels from blurry images. (C) 2016 Optical Society of America

关键词： image processing algorithms image quality image reconstruction image registration Imaging techniques Motion estimation

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Laser induced ultrasonic phased array using full matrix capture data acquisition and total focusing method

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OPTICS EXPRESS 2016年第19期24卷 21921-21938页

作者： Stratoudaki, Theodosia Clark, Matt Wilcox, Paul D. Univ Bristol Dept Mech Engn Bristol BS8 1TR Avon England Univ Nottingham Fac Engn Div Elect Syst & Opt Univ Pk Nottingham NG7 2RD England

Laser ultrasonics is a technique where lasers are employed to generate and detect ultrasound. A data collection method (full matrix capture) and a post processing imaging algorithm, the total focusing method, both developed for ultrasonic arrays, are modified and used in order to enhance the capabilities of laser ultrasonics for nondestructive testing by improving defect detectability and increasing spatial resolution. In this way, a laser induced ultrasonic phased array is synthesized. A model is developed and compared with experimental results from aluminum samples with side drilled holes and slots at depths of 5 - 20 mm from the surface. (C) 2016 Optical Society of America

关键词： High power lasers image processing algorithms image quality Laser arrays Laser sources Phased arrays

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Self-calibration single-lens 3D video extensometer for high-accuracy and real-time strain measurement

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OPTICS EXPRESS 2016年第26期24卷 30124-30138页

作者： Shao, Xinxing Eisa, Mohammed Mokhtar Chen, Zhenning Dong, Shuai He, Xiaoyuan Southeast Univ Dept Engn Mech Nanjing 210096 Jiangsu Peoples R China

The accuracy of strain measurement using a common optical extensometer with two-dimensional (2D) digital image correlation (DIC) is not sufficient for experimental applications due to the effect of out-of-plane motion. Although three-dimensional (3D) DIC can measure all three components of displacement without introducing in-plane displacement errors, 3D-DIC requires the stringent synchronization between two digital cameras and requires complicated system calibration of binocular stereovision, which makes the measurement rather inconvenient. To solve the problems described above, this paper proposes a self-calibration single-lens 3D video extensometer for non-contact, non-destructive and high-accuracy strain measurement. In the established video extensometer, a single-lens 3D imaging system with a prism and two mirrors is constructed to acquire stereo images of the test sample surface, so the problems of synchronization and out-of-plane displacement can be solved easily. Moreover, a speckle-based self-calibration method which calibrates the single-lens stereo system using the reference speckle image of the specimen instead of the calibration targets is proposed, which will make the system more convenient to be used without complicated calibration. Furthermore, an efficient and robust inverse compositional Gauss-Newton algorithm combined with a robust stereo matching stage is employed to achieve high-accuracy and real-time subset-based stereo matching. Tensile tests of an Alalloy specimen were performed to demonstrate the feasibility and effectiveness of the proposed self-calibration single-lens 3D video extensometer. (C) 2016 Optical Society of America

关键词： Digital image processing image processing algorithms image sensors Strain measurement Three dimensional imaging Three dimensional measurement

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Noncontact detection of Teflon inclusions in glass-fiber-reinforced polymer composites using terahertz imaging

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APPLIED OPTICS 2016年第36期55卷 10215-10222页

作者： Zhang, Jin Wang, Jie Han, Xiaohui Cui, Hong-Liang Shi, Changcheng Zhang, Jinbo Shen, Yan Jilin Univ Coll Instrumentat & Elect Engn Changchun 130061 Peoples R China Chinese Acad Sci Chongqing Inst Green & Intelligent Technol Key Lab Multiscale Mfg Technol Res Ctr Terahertz Technol Chongqing 400714 Peoples R China Harbin FRP Inst Harbin 150036 Peoples R China Chongqing Polycomp Int Corp Chongqing 400082 Peoples R China

We employed terahertz (THz) time-domain spectroscopy (TDS) imaging technology, a new nondestructive testing method, to detect the inclusions of glass-fiber-reinforced polymer (GFRP) composites. The refractive index and absorption coefficient of two types of GFRP composites (epoxy GFRP composites and polyester GFRP composites) were first extracted, and GFRP composites with Teflon inclusions were examined, including an epoxy GFRP solid panel with a smaller Teflon inclusion hidden behind a larger Teflon inclusion, and polyester GFRP solid panels with Teflon inclusions of various sizes, at different depths. It was experimentally demonstrated that THz TDS imaging technology could clearly detect a smaller inclusion hidden behind a larger inclusion. When the reflected THz pulse from the inclusion did not overlap with that from the front surface of the sample, removal of the latter before Fourier transform was shown to be helpful in imaging the inclusions. With sufficiently strong incident THz radiation, inclusion insertion depth had little impact on the ability of the THz wave to detect inclusions. However, as the thickness of the inclusion became thinner, the inclusion detection ability of the THz wave deteriorated. In addition, with a combination of reflected C-scan imaging and B-scan imaging using the reflected time-domain waveform, both the lateral sizes and locations of the inclusions and the depths and thicknesses of the inclusions were clearly ascertained. (C) 2016 Optical Society of America

关键词： Absorption coefficient image processing image processing algorithms Imaging techniques Refractive index Terahertz imaging

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