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 mo...
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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
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 ch...
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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.
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 patie...
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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 imageprocessing 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.
We present results from non-interferometric quantitative phase imaging (QPI) for thickness estimation and morphological analysis of human spermatozoa. QPI along with algorithms for imageprocessing enable localization...
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We present results from non-interferometric quantitative phase imaging (QPI) for thickness estimation and morphological analysis of human spermatozoa. QPI along with algorithms for imageprocessing 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. imageprocessing 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 imageprocessing 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
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. Now...
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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 imageprocessing 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
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
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.
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....
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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
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 st...
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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
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...
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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 imageprocessing 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.
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, d...
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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
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