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Time-multiplexed multi-view three-dimensional display with projector array and steering screen

OPTICS EXPRESS 2018年第12期26卷 15528-15538页

作者： Xia, Xinxing Zhang, Xiangyu Zhang, Lei Surman, Phil Zheng, Yuanjin Nanyang Technol Univ Sch Elect & Elect Engn 50 Nanvang Ave Singapore 639798 Singapore

A novel time-multiplexed multi-view three-dimensional (3D) display has been implemented using a projector array to provide the image source and an angular steering-screen module to generate multiple high density horizontal views. The liquid crystal (LC)-based steering screen was specially developed to deflect light beams over a small range and operate in synchronism with the projector array with the use of a customized FPGA driver. The prototype produces vivid color 3D scenes with smooth parallax to multiple viewers. The experimental results verify the proposed multi-projection time-multiplexed multi-view 3D display method that uses a steering screen to produce dense views. Displaying both static and dynamic 3D contents is achieved in our implemented 36-view 3D display prototype. The results of crosstalk measurements are given and analyzed to evaluate the display performance. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： Flat panel displays Holographic displays image processing algorithms Optical systems Pico projectors Three dimensional television

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Radiometric calibration methods for day/night whole sky imagers and extinction imagers

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APPLIED OPTICS 2019年第21期58卷 5663-5673页

作者： Shields, Janet E. Karr, Monette E. Univ Calif San Diego Scripps Inst Oceanog Marine Phys Lab 9500 Gilman Dr La Jolla CA 92093 USA

This paper discusses the new radiometric calibration methods and results that we have developed to apply to day/ night whole sky imager data and extinction imager data. Day/night whole sky imagers detect the presence and location of clouds and categorize them by opacity. The new day and night doud algorithms for these instruments are documented elsewhere, and these algorithms depend on the use of the new calibrations we have developed. In this paper, we document our calibration methods for determining the absolute radiance of the whole sky imager scene at each pixel in the images as well as the results of the calibrations. The extinction imagers are new systems we developed that determine beam transmittance and path extinction for horizontal paths through the atmosphere. These instruments and their algorithms are documented elsewhere, and they also depend on the new calibration results. The extinction imager algorithms only require relative radiances, as opposed to absolute radiances. The calibration steps for the two instruments are quite similar, and they include dark correction;linearity calibration, which corrects for nonlinearities in the signal versus flux relationship;absolute calibration (for the whole sky imager);and uniformity calibration, which corrects for pixel-to-pixel nonuniformities. These developments include methods for handling uniformity calibrations in a system using a fisheye lens and the calibration of both visible and short-wave IR systems. This paper presents both the new methods and results in support of the papers documenting the algorithms. (C) 2019 Optical Society of America

关键词： Atmospheric optics Extinction coefficients image processing algorithms Infrared systems Low light levels Radiometric calibration

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Precision optical path alignment system for point diffraction interferometer based on image information

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APPLIED OPTICS 2019年第14期58卷 3703-3711页

作者： Zhao, Zhuo Li, Bing Kang, Xiaoqin Chen, Lei Wei, Xiang Xi An Jiao Tong Univ State Key Lab Mfg Syst Engn 99 Yanxiang Rd Xian 710054 Shaanxi Peoples R China Xi An Jiao Tong Univ Int Joint Res Lab Micro Nano Mfg & Measurement Te Xian 710049 Shaanxi Peoples R China

In a point diffraction interferometer, the existence of alignment error between an objective convergent spot and a diffraction pinhole can lead to wavefront error and diffraction intensity reduction. Meanwhile, the contrast of the point diffraction interferograms probably decreases in this procedure. These changes will have significant influence on its inspection precision. A precise alignment system of an optical path for a point diffraction interferometer is proposed in this paper. First, diffraction theory is used to analyze the mathematical relationships of alignment error to diffraction wavefront error and numerical aperture and wavefront error to pinhole size. Then, according to the requirement, the scheme of an optical path alignment system is designed. In this stage, alignment images as well as intensities of a reflected and diffracted beam from the point diffraction plate will be acquired. In addition, an image processing algorithm for measuring alignment error is designed, and a mathematical model between quantities of measurement and control is constructed. Finally, implementation and experiment of this method are also introduced. Misalignment situations, including lateral translation, longitudinal defocus, and tilt error, are well eliminated, and the quality of interferograms is also improved. From the results, it can be concluded that the system is of desirable precision and efficiency. (C) 2019 Optical Society of America

关键词： Diffraction theory Extreme ultraviolet lithography image processing algorithms Optical elements Point diffraction interferometry Power spectral density

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Employment of Fizeau fringe disintegration to magnify small phase variations

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS 2020年第11期37卷 A62-A68页

作者： Wahba, Hamdy H. Ramadan, Wael A. El-Tawargy, Ahmed S. Damietta Univ Fac Sci Phys Dept New Damietta Ciiy 34517 Egypt Taif Univ Phys Dept Fac Sci At Taif 21974 Al Haweiah Saudi Arabia

When an object produces a small phase variation not less than the minimum phase variation detectable by the used system and more than the system's noise, the object is considered as a tiny (or small) object. The measurement of interferometric phase differences evolved from a tiny optical phase object has gained attention in recent years due to its usefulness in accurate detection of nanometric dimensions. In the current work, a Fizeau wedge interferometer is used as an aberrationless method to amplify phase variations of a tiny object. The phase object is inserted between the two semi-reflecting/partially transmitting plates making a smallwedge angle in between. The fast Fourier transformation (FFT) spectrum of the obtained interferograms is characterized by some frequency equidistant peaks. The number of these peaks is related to the number of the interfered rays and each peak represents a set of two-beam interferences. We applied a mask to select one of these peaks and reproduced its corresponding optical phase map via employing inverse fast Fourier transformation. The produced map contains the magnified phase variation with a magnification factor equal to 2 times the selected peak's order. Experimental verification of two different phase object samples to amplify their phase variations with different amplification factors is performed. An integrated magnified phase by the object is calculated to test the validity of the proposed method. It is found that the magnification according to the selection of different FFT peaks is a little bit deviated from the expected magnification factors which is referred to ignoring refraction of the optical rays by the object. In spite of these deviations, good results are obtained. (C) 2020 Optical Society of America

关键词： Fizeau interferometry Holographic recording materials image processing algorithms Interferometry Phase measurement Ray tracing

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Denoising the space-borne high-spectral-resolution lidar signal with block-matching and 3D filtering

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APPLIED OPTICS 2020年第9期59卷 2820-2828页

作者： Zheng, Zhuofan Chen, Weibiao Zhang, Yupeng Chen, Sijie Liu, Dong Zhejiang Univ Coll Opt Sci & Engn State Key Lab Modern Opt Instrumentat Hangzhou 310027 Zhejiang Peoples R China Chinese Acad Sci Shanghai Inst Opt & Fine Mech Shanghai 201800 Peoples R China

The constituents and structures of the atmosphere directly or indirectly affect the radiative energy budget of the Earth;thus, there is an urgent need to measure these components. Space-borne lidar is a powerful instrument for depicting the global atmosphere. Several space-borne lidars with spectral discrimination filters are proposed and even currently being developed, including the Chinese Aerosol-Cloud High-Spectral-Resolution Lidar (ACHSRL) onboard the Aerosol Carbon Detection Lidar satellite. However, the long distance from the satellite to the atmosphere near the Earth surface weakens the signal strength and debilitates the detection accuracy of space-borne lidar. Furthermore, due to absorption of Rayleigh scattering when it passes through the spectral discrimination filter, the signal-to-noise ratio in the molecular channel decreases. The traditional denoising method is to average the echo signals both vertically and horizontally, but the high speed of the satellite (7.5 km/s) and the varying atmosphere structure will blur detected layer features. A novel method to reduce the signal noise level of ACHSRLis proposed in this paper. Astate-of-the-art algorithm for imaging denoising, block matching 3D filtering (BM3D), is employed. As ACHSRL has not been launched, a simulation study is performed. In the simulation experiment, we connect adjacent lidar signal profiles into one 2D matrix and treat it as an image. Unlike the existing lidar denoising algorithm which uses neighboring profiles to smooth, BM3D performs frequency domain transformation of the signal image and then searches for a similar patch in a given block to conduct collaborative filtering. This algorithm not only achieves denoising, but also preserves aerosol/cloud feature details. After denoising by BM3D, the peak signal-to-noise ratios of echo signals in all channels are improved and the retrieval accuracy of particulate optical properties is also refined, especially for the retrieval of the extinc

关键词： Atmospheric composition Extinction coefficients image processing image processing algorithms Mie theory Rayleigh scattering

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Efficient algorithms for the soft: Morphological operators

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IEEE TRANSACTIONS ON PATTERN ANALYSIS AND MACHINE INTELLIGENCE 1996年第11期18卷 1142-1147页

作者： Zmuda, MA Tamburino, LA USAF WRIGHT LABAACAWRIGHT PATTERSON AFBOH 45433

This correspondence presents two soft morphological algorithms that process multiple images simultaneously. The first algorithm performs best when the structuring elements contain less than 19 points;whereas, the second algorithm should be used for larger structuring elements. Theoretical and experimental analyses show these algorithms are faster than the conventional algorithm.

关键词： mathematical morphology soft morphology image processing algorithms efficient algorithms

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Phase imaging microscopy under the Gabor regime in a minimally modified regular bright-field microscope

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OPTICS EXPRESS 2021年第26期29卷 42738-42750页

作者： Mico, Vicente Trindade, Karina Angel Picazo-Bueno, Jose Univ Valencia Dept Opt & Optometria & Ciencias Vis C Doctor Moliner 50 Burjassot 46100 Spain

Quantitative phase imaging (QPI) is nowadays a powerful tool for visualization and analysis of biological processes. QPI is usually attained from specifically designed optical microscopes retrieving phase information in a quantitative way. In this paper we report on an extremely simple, low cost and compact way to update a standard bright-field microscope with coherent sensing capabilities. It is based on the in-line Gabor holography concept and only needs to replace the illumination broadband source of the regular microscope with a coherent one. The proposed methodology is completed by the recording of a digital in-line Gabor hologram instead of regular imaging conditions and by the numerical processing of the recorded hologram to finally achieve QPI. The selection of the defocus distance is critical to finally achieve high quality phase imaging, so calibration considering phase and amplitude test targets is presented for the proper definition of such defocus distance. In addition, the selected configuration is experimentally validated using different samples (microbeads, cheek cells and alive spermatozoa). All the experiments are implemented in a regular Olympus BX-60 upright microscope using a 20X 0.46NA objective lens. The proposed method shows how to convert a regular microscope into a holographic one with probably the minimum needed modifications and with the main limitation coming from the Gabor imaging conditions (weak diffractive samples and twin image presence). (C) 2021 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

关键词： Digital image processing image processing algorithms image quality Imaging systems Optical microscopy Wave front sensing

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Reduction of speckle noise in digital holography using a neighborhood filter based on multiple sub-reconstructed images

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OPTICS EXPRESS 2022年第6期30卷 9222-9232页

作者： Chen, Kai Chen, Li Xiao, JiaQi Li, JinYang Hu, YiHua Wen, KunHua Guangdong Univ Technol Sch Phys & Optoelect Engn Guangzhou 510006 Peoples R China Guangdong Univ Technol Guangdong Prov Key Lab Informat Photon Technol Guangzhou 510006 Peoples R China

The application of digital holography in several fields is limited since speckle destroys the original information of the reconstructed image. This paper proposes a neighborhood filter based on multiple sub-reconstructed images according to the random distribution of speckle noise. In this method, the denoised value is equal to the weighted sum of neighboring pixel values, and the weight is calculated by the degree of correlation between different positions of multiple sub-holograms. The experimental results show that the method can greatly reduce the speckle noise, and its noise reduction performance is superior to traditional digital image processing algorithms. (C) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

关键词： Digital image processing image processing algorithms Speckle noise Speckle patterns Speckle reduction Three dimensional imaging

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Three-dimensional ultrahigh resolution optical coherence tomography imaging of age-related macular degeneration

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OPTICS EXPRESS 2009年第5期17卷 4046-4060页

作者： Chen, Yueli Vuong, Laurel N. Liu, Jonathan Ho, Joseph Srinivasan, Vivek J. Gorczynska, Iwona Witkin, Andre J. Duker, Jay S. Schuman, Joel Fujimoto, James G. MIT Dept Elect Engn & Comp Sci Cambridge MA 02139 USA MIT Elect Res Lab Cambridge MA 02139 USA Tufts Med Ctr New England Eye Ctr Boston MA 02116 USA Univ Pittsburgh Sch Med Dept Ophthalmol UPMC Eye Ctr Pittsburgh PA 15261 USA

Ultrahigh resolution optical coherence tomography (OCT) enhances the ability to visualize different intra retinal layers. In age-related macular degeneration (AMD), pathological changes in individual retinal layers, including photoreceptor inner and outer segments and retinal pigment epithelium, can be detected. OCT using spectral/Fourier domain detection enables high speed, volumetric imaging of the macula, which provides comprehensive three-dimensional tomographic and morphologic information. We present a case series of AMD patients, from mild drusen to more advanced geographic atrophy and exudative AMD. Patients were imaged with a research prototype, ultrahigh resolution spectral/Fourier domain OCT instrument with 3.5 mu m axial image resolution operating at 25,000 axial scans per second. These cases provide representative volumetric datasets of well-documented AMD pathologies which could be used for the development of visualization and imaging processing methods and algorithms. (C) 2009 Optical Society of America

关键词： image processing algorithms Line scan cameras Optic nerve Retinal nerve fiber layer Three dimensional imaging Visual acuity

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Object-independent structural image analysis: History and modern approaches

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JOURNAL OF OPTICAL TECHNOLOGY 2014年第11期81卷 642-650页

作者： Lutsiv, V. R. Malashin, R. O. St Petersburg Natl Res Univ Informat Technol Mech St Petersburg Russia SI Vavilov State Opt Inst St Petersburg Russia

This paper discusses the history of the appearance and development of structural image analysis. The characteristic disadvantages and advantages of the structural methods that are used and the prerequisites for improving them are analyzed for each of the historical stages. The material culminates with a description of the features of the organization and possibilities of the optimum modern algorithms for structural analysis and a treatment of directions in which they can be improved further. (C) 2015 Optical Society of America.

关键词： image analysis image processing algorithms image recognition devices Machine vision Neural networks Remote sensing

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