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

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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Depth-dependent dispersion compensation for full-depth OCT image

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OPTICS EXPRESS 2017年第9期25卷 10345-10354页

作者： Pan, Liuhua Wang, Xiangzhao Li, Zhongliang Zhang, Xiangyang Bu, Yang Nan, Nan Chen, Yan Wang, Xuan Dai, Fengzhao Chinese Acad Sci Shanghai Inst Opt & Fine Mech Lab Informat Opt & Optoelect Technol Shanghai 201800 Peoples R China Univ Chinese Acad Sci Beijing 100049 Peoples R China Jiangnan Univ Sch Sci Wuxi 214122 Peoples R China

A depth-dependent dispersion compensation algorithm for enhancing the image quality of the Fourier-domain optical coherence tomography (OCT) is presented. The dispersion related with depth in the sample is considered. Using the iterative method, an analytical formula for compensating the depth-dependent dispersion in the sample is obtained. We apply depth-dependent dispersion compensation algorithm to process the phantom images and in vivo images. Using sharpness metric based on variation coefficient to compare the results processed with different dispersion compensation algorithms, we find that the depth-dependent dispersion compensation algorithm can improve image quality at full depth. (C) 2017 Optical Society of America

关键词： Effective refractive index image processing algorithms image quality image quality assessment Point spread function Spatial frequency

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Negative optical radiation force and spin torques on subwavelength prolate and oblate spheroids in fractional Bessel-Gauss pincers light-sheets

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS image SCIENCE AND VISION 2017年第7期34卷 1246-1254页

作者： Mitri, F. G. Chevron Area Technol ETC 52 Santa Fe NM 87508 USA

Fractional Bessel-Gauss light-sheets [J. Opt. 19, 055602 ( 2017)], which correspond to finite optical "slices" in 2D and possess asymmetric slit openings and bending characteristics, are examined from the standpoint of optical radiation force and spin torque theories for a subwavelength spheroid with arbitrary orientation in space. The vector angular spectrum decomposition method in addition to the Lorenz gauge condition and Maxwell's equations are used to determine the Cartesian components of the incident radiated electric field of the Bessel-Gauss light-sheets. In the framework of the dipole approximation, the numerical results for the Cartesian components of the optical radiation force and spin torque vectors show that negative forces ( oriented in the opposite direction of wave motion) and spin torques arise depending on the beam parameters, the orientation of the subwavelength spheroid in 3D space, and its aspect ratio (i.e., prolate versus oblate). The spin torque sign reversal reveals that counter-clockwise or clockwise rotations around the center of mass of the spheroid can occur. The results find important applications in the application of auto-focusing light-sheets in particle manipulation, rotation, and optical sorting devices. (C) 2017 Optical Society of America

关键词： Electric fields image processing algorithms Magnetic fields Numerical simulation Optical force Wave propagation

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Automated multimodal spectral histopathology for quantitative diagnosis of residual tumour during basal cell carcinoma surgery

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BIOMEDICAL OPTICS EXPRESS 2017年第12期8卷 5749-5766页

作者： Boitor, Radu Kong, Kenny Shipp, Dustin Varma, Sandeep Koloydenko, Alexey Kulkarni, Kusum Elsheikh, Somaia Schut, Tom Bakker Caspers, Peter Puppels, Gerwin van der Wolf, Martin Sokolova, Elena Nijsten, T. E. C. Salence, Brogan Williams, Hywel Notingher, Ioan Univ Nottingham Sch Phys & Astron Univ Pk Nottingham NG7 2RD England Circle Nottingham Ltd NHS Treatment Ctr Lister Rd Nottingham NG7 2FT England Royal Holloway Univ London Math Dept Egham TW20 OFX Surrey England Nottingham Univ Hosp NHS Trust Dept Pathol QMC CampusDerby Rd Nottingham NG7 2117 England Erasmus Univ Med Ctr Rotterdam Dept Dermatol Rotterdam Netherlands RiverD Int Marconistr 16 NL-3029 AK Rotterdam Netherlands East Surrey Hosp Canada Ave Redhill RH1 5RH Surrey England Nottingham Univ Hosp NHS Trust Ctr Evidence Based Dermatol QMC CampusDerby Rd Nottingham NG7 2UH England

Multimodal spectral histopathology (MSH), an optical technique combining tissue auto-fluorescence (AF) imaging and Raman micro-spectroscopy (RMS), was previously proposed for detection of residual basal cell carcinoma (BCC) at the surface of surgically-resected skin tissue. Here we report the development of a fully-automated prototype instrument based on MSH designed to be used in the clinic and operated by a non-specialist spectroscopy user. The algorithms for the AF image processing and Raman spectroscopy classification had been first optimised on a manually-operated laboratory instrument and then validated on the automated prototype using skin samples from independent patients. We present results on a range of skin samples excised during Mohs micrographic surgery, and demonstrate consistent diagnosis obtained in repeat test measurement, in agreement with the reference histopathology diagnosis. We also show that the prototype instrument can be operated by clinical users (a skin surgeon and a core medical trainee, after only 1-8 hours of training) to obtain consistent results in agreement with histopathology . The development of the new automated prototype and demonstration of inter-instrument transferability of the diagnosis models are important steps on the clinical translation path: it allows the testing of the MSH technology' in a relevant clinical environment in order to evaluate its performance on a sufficiently large number of patients.

关键词： image analysis image processing algorithms Micro Raman spectroscopy Optical coherence tomography Raman microscopy Raman spectroscopy

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Eddy current pulsed thermography for ballistic impact evaluation in basalt-carbon hybrid composite panels

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APPLIED OPTICS 2018年第18期57卷 D74-D81页

作者： Zhang, Hai Sfarra, Stefano Osman, Ahmad Sarasini, Fabrizio Netzelmann, Udo Perilli, Stefano Ibarra-Castanedo, Clemente Maldague, Xavier P. V. Univ Laval Comp Vis & Syst Lab Dept Elect & Comp Engn Quebec City PQ G1V 0A6 Canada Fraunhofer Inst Nondestruct Testing IZFP Dept Inspect Components & Assemblies D-66123 Saarbrucken Germany Univ Aquila Dept Ind & Informat Engn & Econ I-67100 Laquila Italy Tomsk Polytech Univ Thermal Control Methods Lab Tomsk 634050 Russia Univ Appl Sci Saarland Htw Saar D-66117 Saarbrucken Germany Sapienza Univ Rome Dept Chem Engn Mat Environm I-00184 Rome Italy Univ Toronto Dept Mech & Ind Engn Ctr Adv Diffus Wave Technol CADIFT 5 Kings Coll Rd Toronto ON M5S 3G8 Canada

In this paper, eddy current pulsed thermography was used to evaluate ballistic impact damages in basalt-carbon hybrid fiber-reinforced polymer composite laminates for the first time, to our knowledge. In particular, different hybrid structures including intercalated stacking and sandwich-like sequences were used. Pulsed phase thermography, wavelet transform, principle component thermography, and partial least-squares thermography were used to process the thermographic data. Ultrasound C-scan testing and X-ray computed tomography were also performed for comparative purposes. Finite element analysis was used for validation. Finally, an analytical and comparative study was conducted based on signal-to-noise ratio analysis. (C) 2018 Optical Society of America

关键词： image processing image processing algorithms Spatial resolution Thermal imaging Wavelet transforms X ray computed tomography

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