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Multidispersed bubble-size measurements by interferometric particle imaging at scattering angles of 90° and 45°

APPLIED OPTICS 2018年第36期57卷 10496-10504页

作者： Zhang, Hongxia Wang, Xiaolei Sun, Jinlu Jia, Dagong Liu, Tiegen Tianjin Univ Coll Precis Instrument & Optoelect Engn Tianjin 300072 Peoples R China Tianjin Univ Key Lab Optoelect Informat Technol Minist Educ Tianjin 300072 Peoples R China

Measurements of multidispersed bubble diameter are important in hydraulics, biology, and other such fields. Interferometric particle imaging (IPI) systems are used to measure the bubble diameter. In geometric approximation, the scattering angle cannot be greater than 2 arccos m. We propose a universal method for calculating the bubble diameter at wide scattering angles and use an IPI system to measure the bubble-size distribution at 90 degrees and 45 degrees. The particle size distributions measured at two angles are consistent with each other. The results of this study indicate that this method is suitable for measuring the bubble-size distribution. (C) 2018 Optical Society of America

关键词： Fourier transforms High power lasers image processing algorithms Particle scattering Scattering Spatial frequency

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Algorithm for detecting artificial objects against natural backgrounds

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JOURNAL OF OPTICAL TECHNOLOGY 2018年第6期85卷 338-342页

作者： Pronin, S., V Russian Acad Sci IP Pavlov Inst Physiol St Petersburg Russia

This paper describes an algorithm for distinguishing between images of two classes of objects: artificial and natural. An approximation to the image is generated using graphical elements similar to the receptor fields of neurons in the primary visual cortex (Zone VI). We show that the approximation-error distribution for natural-object images lies at higher values of the approximation error than that for artificial-object images. This difference makes it possible to detect artificial objects against natural backgrounds. (C) 2018 Optical Society of America

关键词： Bandpass filters image processing algorithms image recognition Nonlinear spatial filtering Spatial frequency Visual system

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Automated calibration of multi-camera-projector structured light systems for volumetric high-speed 3D surface reconstructions

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OPTICS EXPRESS 2018年第25期26卷 33278-33304页

作者： Deetjen, Marc E. Lentink, David Stanford Univ Dept Mech Engn Stanford CA 94305 USA

It is challenging to calibrate multiple camera-projector pairs for multi-view 3D surface reconstruction based on structured light. Here, we present a new automated calibration method for high-speed multi-camera-projector systems. The method uses printed and projected dot patterns on a planar calibration target, which is moved by hand in the calibration volume. Calibration is enabled by automated image processing and bundle-adjusted parameter optimization. We determined the performance of our method by 3D reconstructing a sphere. The accuracy is -0.03 +/- 0.09 % as a percentage of the diameter of the calibration volume. Applications include quality control, autonomous systems, engineering measurements, and motion capture, such as the preliminary 3D reconstruction of a bird in flight we present here. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： Camera calibration image processing image processing algorithms Stray light Structured light Temporal resolution

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Research on high-resolution imaging technology based on light field manipulation for a lenslet-based plenoptic camera

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APPLIED OPTICS 2018年第33期57卷 9877-9886页

作者： Liu, Xincheng Ma, Haotong Ren, Ge Qi, Bo Xie, Zongliang Chu, Junqiu Bai, Junjie Chinese Acad Sci Key Lab Opt Engn Chengdu 610209 Sichuan Peoples R China Chinese Acad Sci Inst Opt & Elect Chengdu 610209 Sichuan Peoples R China Univ Chinese Acad Sci Beijing 100039 Peoples R China

In this paper, an aberration correction method for an extended target is proposed to solve the problem of the lenslet-based plenoptic camera not imaging clearly under the influence of aberrations. We propose a light field manipulation method to improve performance of the light field imaging system. The principle of this method is that the sub-aperture images extracted from the raw light field image are offset when the light field imaging system is affected by aberrations, and the symmetrical arrangement of the sub-aperture image array is destroyed. By repairing the symmetrical arrangement of the sub-aperture image array, the influence of phase aberrations on the imaging system can be eliminated, and the resolution of the plenoptic camera can be improved. We use an image correlation algorithm to process the sub-aperture images of the plenoptic camera, calculate and compensate each sub-aperture image's displacement caused by aberrations, and restore the symmetrical arrangement of the sub-aperture image array;then, a corrected high-resolution refocused image can be generated. In particular, this method uses only the raw light field information obtained by the plenoptic camera in a single exposure, without adding other hardware devices. Furthermore, it takes the extended target itself as the reference image, so the ideal position need not be calibrated in advance. Also, the parallax information of the sub-aperture images is retained, and the method is simple and easy to use. Numerical simulation and experimental results show that the technology proposed in this paper can work well for high-resolution imaging of a plenoptic camera with phase aberrations. This method can be potentially applied to analyze lens aberration, media-induced image distortion such as water turbulence in underwater imaging, and atmospheric turbulence in remote imaging. It may have important application prospects in the fields of astronomical object detection, remote sensing, etc. (C) 2018 Optical

关键词： Atmospheric turbulence image metrics image processing algorithms Imaging systems Laser guide stars Underwater imaging

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Terahertz pulse time-domain holography with balance detection: complex-domain sparse imaging

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APPLIED OPTICS 2019年第34期58卷 G61-G70页

作者： Kulya, Maksim Petrov, Nikolay V. Katkovnik, Vladimir Egiazarian, Karen ITMO Univ Digital & Display Holog Lab St Petersburg Russia Tampere Univ Fac Informat Technol & Commun Tampere Finland

We investigated the peculiarities of the terahertz pulse time-domain holography principle in the case of raster scanning with the balance detection system. The noise in this system represents a Skellam distribution model, which differentiates it from systems based on a photoconductive antenna. We analyzed this Skellam model and provided both numerical and experimental investigations. We found that the variance of the noise in the balance detection system does not depend on the true signal. Complex-domain images obtained in this model are filtered by block-matching algorithms adapted for spatio-temporal and spatiospectral volumetric data. We presented a new cube complex-domain filter algorithm that uses block matching in all 3D data sets simultaneously in spatial and frequency coordinates. A combination of temporal and complex-domain filters allows us to expand the dynamic range of terahertz frequencies for which we can obtain amplitude/phase information. Experimental data demonstrate an improvement in the quality of the resultant images both in the time domain and complex-spectral domain. The simulation and experimental results are in good agreement. (C) 2019 Optical Society of America

关键词： Electric fields image processing algorithms Photoconductivity Spatial frequency Terahertz spectroscopy Wave front sensing

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Endoscopic image enhancement with noise suppression

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HEALTHCARE TECHNOLOGY LETTERS 2018年第5期5卷 154-157页

作者： Xia, Wenyao Chen, Elvis C. S. Peters, Terry Univ Western Ontario Med Biophys 1151 Richmond St London ON Canada Robarts Res Inst 1151 Richmond St North London ON Canada

Stereoscopic endoscopes have been used increasingly in minimally invasive surgery to visualise the organ surface and manipulate various surgical tools. However, insufficient and irregular light sources become major challenges for endoscopic surgery. Not only do these conditions hinder image processing algorithms, sometimes surgical tools are barely visible when operating within low-light regions. In addition, low-light regions have low signal-to-noise ratio and metrication artefacts due to quantisation errors. As a result, present image enhancement methods usually suffer from heavy noise amplification in low-light regions. In this Letter, the authors propose an effective method for endoscopic image enhancement by identifying different illumination regions and designing the enhancement design criteria for desired image quality. Compared with existing image enhancement methods, the proposed method is able to enhance the low-light region while preventing noise amplification during image enhancement process. The proposed method is tested with 200 images acquired by endoscopic surgeries. Computed results show that the proposed algorithm can outperform state-of-the-art algorithms for image enhancement, in terms of naturalness image quality evaluator and illumination index.

关键词： biomedical optical imaging desired image quality different illumination regions endoscopes endoscopic image enhancement endoscopic surgery enhancement design criteria existing image enhancement methods heavy noise amplification illumination index image enhancement image enhancement process image processing image processing algorithms insufficient light sources irregular light sources low signal-to-noise ratio low-light region medical image processing medical robotics minimally invasive surgery naturalness image quality evaluator noise suppression stereoscopic endoscopes surgery surgical tools

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Computer Aided Detection of Dental Implant Crown Defects

Computer Aided Detection of Dental Implant Crown Defects

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7th International Advances in Applied Physics and Materials Science Congress and Exhibition (APMAS)

作者： Bocekci, V. G. Demir, O. Marmara Univ Fac Technol Dept Elect & Elect Engn TR-34722 Istanbul Turkey

A dental implant is an artificial tooth root that is placed into to hold a replacement tooth or bridge. Crown is the apparent part of the dental implant. Detection of crown defects is important for health of the patient before the surgery. In this study, a computer aided detection system developed to analyze tooth dental implant crown digital images to detect defects. The developed system detects various implant defects such as fractures, cracks, dents, spots and roughness. Micro fractures are detected using morphologic operations by the system. Dents and spots are also detected using this image processing techniques. Textural analysis can be performed on digital images to detect different roughness and porosity areas on dental implant. The developed system prevents waste of time and decreases costs. Using the system also will increase patients' satisfaction.

关键词： structural failure of materials image analysis image processing algorithms

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Quantitative label-free technique for morphological evaluation of human sperm-a promising tool in semen evaluation

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OSA CONTINUUM 2018年第4期1卷 1215-1225页

作者： Poola, Praveen Kumar Jayaraman, Varshini Chaithanya, K. Rao, Durga John, Renu Indian Inst Technol Hyderabad Dept Biomed Engn Kandi 502285 Telangana India Univ Hyderabad Sch Life Sci Dept Anim Biol Hyderabad 500046 Telangana India Oasis Ctr Reprod Med Hyderabad 500034 Telangana India

We present results from non-interferometric quantitative phase imaging (QPI) for thickness estimation and morphological analysis of human spermatozoa. QPI along with algorithms for image processing enable localization and quantification of subcellular structures of spermatozoa, including the acrosomal, nuclear, mid-piece, and tail regions. This approach based on the transport of intensity equation (TIE) using a simple bright-field microscope renders quantitative phase image with nanometric depth sensitivity, allowing the precise subcellular structural resolution of human spermatozoa. We demonstrate the potential of TIE in real-time phase imaging and the morphological analysis of spermatozoa. We first calibrate the TIE using micro-beads and a standard phase target of known dimensions. image processing for quantitative volume estimation of nuclei and acrosomal regions is carried out on the reconstructed quantitative phase images. We also apply a Hilbert transform-based image processing algorithm to the retrieved phase for visualization of vacuoles present on the sperm head. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： image processing image processing algorithms Imaging techniques Interference microscopy Phase imaging X ray imaging

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Effect of illuminating wavelength on the contrast of meibography images

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OSA CONTINUUM 2018年第3期1卷 1041-1054页

作者： Peral, Assumpta Alons, Jose Gomez-Pedrero, Jose A. Univ Complutense Madrid Fac Opt & Optometria Dept Optometry & Vis C Arcos de Jalon 118 Madrid 28037 Spain Univ Complutense Madrid Opt Dept Appl Opt Complutense Grp Fac Opt & Optometria C Arcos de Jalon 118 Madrid 28037 Spain Indizen Opt Technol C Santa Engracia 6 Madrid 28010 Spain

Evaluation of the Meibomian glands morphology is becoming a popular assessment for dry eye. This evaluation is usually done by imaging the glands on the everted lids while they are illuminated with infrared light. Nowadays techniques to determine gland condition and dropout are based on grading scales with which meibography images are subjectively evaluated. In this work, we have measured the contrast of Meibomian gland images from ten subjects and for a range of wavelengths of the monochromatic illuminating light. We have used a xenon lamp and a monochromator as a light source, and a semiautomatic image processing technique for measuring the image contrast from 600 nm to 1050 nm. Contrast values inside glands are from 0.025 to 0.015 and between glands from 0.06 to 0.04. The greater values of contrast are obtained when Meibomian glands are illuminated with a wavelength close to 600 nm. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： image processing image processing algorithms image sensors Imaging techniques Infrared radiation Visible light

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Experimental Demonstration of a Flicker-Free Scheme for Optical Camera Communication

Experimental Demonstration of a Flicker-Free Scheme for Opti...

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Asia Communications and Photonics Conference and Exhibition (ACP)

作者： Zhongwei Jiang Jing He Jin Shi Yi Liu Qi Tang Hunan University Changsha China Shenzhen Institute of Information Technology Shenzhen China

In this paper, a flicker-free scheme based on Manchester modulation is proposed and demonstration for OCC. Experimental results show that the BER performance is not affected by ISO under the visible image.

ISBN: (纸本)9781943580705

关键词： Bit error rate image processing image processing algorithms image sensors Modulation Visible light

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