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Single-shot digital phase-shifting Moire patterns for 3D topography

APPLIED OPTICS 2021年第4期60卷 A84-A92页

作者： Guo, Haiyun Zhou, Haowen Banerjee, Partha P. Univ Dayton Electroopt & Photon Dayton OH 45469 USA

A simple and robust technique of Moire topography with single-image capture and incorporating digital filtering along with a four-step digitally implemented phase-shifting method is introduced for three-dimensional (3D) surface mapping. Feature details in the order of tens to hundreds of microns can be achieved using interferometrically generated structured light to illuminate the object surface. Compared to the traditional optical phase-shifting method, a digital phase-shifting method based on Fourier processing is implemented with computer-generated sinusoidal patterns derived from the recorded deformed fringes. This enables a single capture of the image that can be used to reconstruct the 3D topography of the surface. Single-shot imaging is simple to implement experimentally and avoids errors in introducing the correct phase shifts. The feasibility of this technique is verified experimentally, and applications to metallic surfaces are demonstrated. (C) 2020 Optical Society of America

关键词： image processing algorithms Moire patterns Moire topography Spatial frequency Surface light scattering Surface mapping

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Evaluation of image quality and patient exposure in fluoroscopy using a phantom: Is there any clinical relevance

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EUROPEAN JOURNAL OF RADIOLOGY 2021年 138卷 109607-109607页

作者： Tsalafoutas, I. A. Tsapaki, V Triantopoulou, I Hamad Med Corp OHS Dept Radiat Safety Sect Doha Qatar Konstantopoulio Hosp Med Phys Unit Athens 14233 Greece

Objective: To investigate the impact of X-ray preset acquisition protocol settings on fluoroscopy image quality (IQ) and radiation exposure. Materials & Methods: A quality control (QC) phantom was imaged with a modern digital C-arm system, using various preset fluoroscopy protocols. IQ was assessed using human observers and in-house software for automated evaluation, based on contrast-to-noise ratios of details and their background. Patient radiation exposure was evaluated using the displayed Incident Air-Kerma and Kerma-Area Product values. Results: Protocol selection affects radiation exposure by a factor of about 3. IQ evaluation showed that acquisition protocols produce images with quite different characteristics. The visual IQ evaluation method was time consuming and cumbersome. The automated method, utilized the visual IQ evaluation results for calibration of detection thresholds. However, it failed to reproduce these results for all images and details types. In some images, digital image processing created artifacts which affected the pixel value distributions around details in a way that could be handled only by the human vision. Conclusion: Manufacturers provide many preset protocols designated for specific clinical uses, which have large impact on IQ characteristics and radiation exposure. However, protocol settings' selection rationale is essentially a "black box" for the end user. Though QC phantoms are currently used for IQ evaluation, they are not appropriate for drawing firm conclusions concerning the expected performance of each protocol in clinical practice. Currently, there is no consensus on the optimum technical characteristics of preset protocols for specific procedures. More work is needed in this area.

关键词： Digital fluoroscopy image quality image artifacts image processing algorithms Radiation exposure

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Breaking diffraction limit of far-field imaging via structured illumination Bessel beam microscope (SIBM)

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OPTICS EXPRESS 2019年第5期27卷 6068-6082页

作者： Perinchery, Sandeep Menon Haridas, Aswin Shinde, Anant Buchnev, Oleksandr Murukeshan, Vadakke Matham Nanyang Technol Univ Sch Mech & Aerosp Engn Singapore 639798 Singapore Ctr Opt & Laser Engn 50 Nanyang Ave Singapore 639798 Singapore Univ Southampton Optoelect Res Ctr Bldg 53 Univ Rd Southampton SO17 1BJ Hants England

Breaking the diffraction limit in imaging microscopes with far-field imaging options has always been the thrust challenge for optical engineers and biologists over the years. Although structured illumination microscopy and Bessel beam assisted imaging has shown the capability of imaging with sub-diffraction resolutions, they rely on the use of objective lenses with large numerical apertures (NA). Hence, they fail to sustain resolutions at larger working distances. In this context, we demonstrate a method for nanoscale resolution imaging at longer working distances, named as Structured Illumination Bessel Microscopy (SIBM). The proposed method is envisaged for both biological and engineering applications that necessitate high imaging resolutions at large working distances. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： Fluorescence microscopy image processing image processing algorithms Imaging techniques Liquid crystal modulators Optical imaging

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Extracting phase distortion from laser glints on a remote target using phase space plenoptic mapping

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS 2019年第7期36卷 1964-1971页

作者： Wu, Chensheng Paulson, Daniel A. Rzasa, John R. Davis, Christopher C. Univ Maryland Elect & Comp Engn Dept College Pk MD 20742 USA Univ Maryland Bioengn Dept College Pk MD 20742 USA Univ Maryland Robert E Fischell Inst Biomed Devices College Pk MD 20742 USA

Directed energy systems rely on the phase conjugation concept to focus laser beams remotely through turbulent environments. In application, a major problem exists where the beacon signal may be neither well defined upon generation nor free from speckle patterns in its vicinity. Such phenomena make it challenging to extract accurate phase information from the scene of a laser beacon and to direct a phase conjugated beam toward the target. In this work, we propose and demonstrate the use of a plenoptic sensor system that images the 4D phase space of multiple glints on a target. A phase retrieval algorithm is designed and applied to reveal the phase distortion from irregular glint patterns. The reconstruction results are verified through comparison with the phase retrieval from a well-defined beacon that alternates its on/off illumination in adjacent frames. As a result, we show that the multi-glint interference problem can be solved using the plenoptic sensor system, which further broadens the application scenarios for directed energy systems. (C) 2019 Optical Society of America

关键词： image processing image processing algorithms Phase conjugate lasers Phase retrieval Systems design Wave front sensing

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Ultra-fast, universal super-resolution radial fluctuations (SRRF) algorithm for live-cell super-resolution microscopy

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OPTICS EXPRESS 2019年第26期27卷 38337-38348页

作者： Han, Yubing Lu, Xiao Zhang, Zhimin Liu, Wenjie Chen, Yuchen Liu, Xu Hao, Xiang Kuang, Cuifang Zhejiang Univ State Key Lab Modern Opt Instrumentat Coll Opt Sci & Engn Hangzhou 310027 Zhejiang Peoples R China Shanxi Univ Collaborat Innovat Ctr Extreme Opt Taiyuan 030006 Shanxi Peoples R China Zhejiang Univ Ningbo Res Inst Ningbo 315100 Peoples R China

For a long term, spatial resolution of fluorescence microscopy was strictly restricted by the diffraction limit. To solve this problem, various super-resolution technologies have been developed. Super-resolution radial fluctuations (SRRF), an emerging type of super-resolution microscopy, directly analyze raw images and generate super-resolution results without fluorophore localization, thereby showing more advantages in handling high-density data. Here, by speeding up the process of the algorithm with graphics processing unit (GPU) and programming with Python language, we expand the universality and improve the computing speed of the SRRF algorithm. We further apply our SRRF algorithm in different live-cell super-resolution microscopy methods with two types of fluorescence fluctuation sources: (i) direct stochastic optical reconstruction microscopy (dSTORM) in which fluorophores themselves blink under specific buffer and laser condition and (ii) structural illumination microscopy (SIM) and modulated Airyscan in which fluorescence fluctuations are artificially introduced with modulated laser illumination. With improved spatiotemporal resolution and image quality, our SRRF algorithm demonstrates its capability in live-cell super-resolution imaging, indicating its wide applications in life sciences. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： Diffraction limit Green fluorescent protein image processing algorithms image quality Speckle patterns Total internal reflection

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Femtosecond laser micro-machining enabled all-fiber mode selective converter

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OPTICS LETTERS 2019年第24期44卷 5941-5944页

作者： Zhang, Cong Li, Zhuoying Fu, Songnian Tang, Ming Liu, Deming Huazhong Univ Sci & Technol Wuhan Natl Lab Optoelect Wuhan 430074 Peoples R China Huazhong Univ Sci & Technol Sch Opt & Elect Informat Wuhan 430074 Peoples R China

We demonstrate a compact all-fiber mode selective converter enabled by femtosecond laser micro-machining on the few-mode fiber (FMF) facet. By introducing a micro-structure into the FMF core, we can achieve a pi spatial phase difference to the fundamental mode of light to be converted. Theoretical optimization reveals that various high-order modes, including LP11, LP02, and LP21 modes, can be selectively converted by various micro-structures on the FMF facet, with a mode extinction ratio of more than 25 dB and mode coupling efficiency of better than 45% over the C-band. Finally, a proof-of-concept experiment is conducted by inscribing a micro-slot on the two-mode fiber facet for the LP01 to LP11 mode conversion. A micro-slot with a width of 6.7 mu m and a depth of 5.4 mu m is fabricated under the optimal femtosecond laser parameters. A LP01 to LP11 mode conversion with an average insert ion loss of 2.7 dB is realized over the C-band, together with a mode intensity profile correlation efficient of more than 65%. Efficient higher-order mode conversion is feasible with a precise femtosecond laser micro-machining. (C) 2019 Optical Society of America

关键词： Extinction ratios Femtosecond lasers image processing algorithms Mode conversion Spatial light modulators Tunable lasers

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Dynamic control of polarization mismatch and coma aberrations in rod-GRIN assemblies

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OPTICS EXPRESS 2019年第10期27卷 14144-14151页

作者： Bagramyan, Arutyun Galstian, Tigran Univ Laval Dept Phys Engn Phys & Opt Ctr Opt Photon & Laser 2375 Rue Terrasse Quebec City PQ G1V 0A6 Canada TLCL Opt Res Inc 2375 Rue Terrasse Quebec City PQ G1V 0A6 Canada Lensvector Inc 2375 Rue Terrasse Quebec City PQ G1V 0A6 Canada

We describe the use of stacked electrically tunable liquid crystal lenses (TLCLs). along with rod gradient index (GRIN) fixed focus lenses, for endoscopic applications. Architectural and driving conditions are found for the optimization of total aberrations of the assembly. Particular attention is devoted to the coma and polarization aberrations. The coma aberration is reduced by stacking two TLCLs with "opposed" pre-tilt angles (all molecules are in the same plane), and then two such doublets are used with cross oriented molecules (in perpendicular planes) to reduce the polarization dependence. The obtained adaptive rod-GRIN lens enables a focus scan over 80 mu m (with exceptionally low RMS aberrations <= 0.16 mu m), making possible the high-qualit), observation of neurons at various depths. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： Gradient index lenses image processing algorithms image quality Lens design Liquid crystal lenses Rod lenses

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Performance evaluation of an implantable sensor for deep brain imaging: an analytical investigation

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OPTICAL MATERIALS EXPRESS 2019年第9期9卷 3729-3737页

作者： Nazempour, Roya Liu, Changbo Chen, Yuwen Ma, Cheng Sheng, Xing Tsinghua Univ Beijing Natl Res Ctr Informat Sci & Technol Dept Elect Engn Beijing 100084 Peoples R China Tsinghua Univ IDG McGovern Inst Brain Res Beijing 100084 Peoples R China

Imaging neural activities at the cellular level in the deep brain is essential to understand the structure and functions of nervous systems. Recently developed fully implantable optical sensors have the capability to capture fluorescence signals within the deep tissue;however, their potential for high-quality imaging is not clear. In this paper, we develop a simplified model to analytically study the photon transport in the biological tissue, and utilize it to understand the optical performance of an implantable fluorescence imager. Spatial resolution of the implanted imager is calculated, and imaging qualities for groups of neurons in two- and three-dimensional configurations are evaluated. The results here establish feasible solutions to design implantable optical sensors and predict their performance for biomedical applications. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： Green fluorescent protein image processing algorithms image quality image sensors Magnetic fields X ray computed tomography

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Integrated multi-channel optical system for bacteria characterization and its potential use for monitoring of environmental bacteria

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BIOMEDICAL OPTICS EXPRESS 2019年第3期10卷 1165-1183页

作者： Buzalewicz, Igor Suchwalko, Agnieszka Trzcinski, Pawel Sas-Paszt, Lidia Sumorok, Beata Kowal, Katarzyna Kozera, Ryszard Wieliczko, Alina Podbielska, Halina Wroclaw Univ Sci & Technol Fac Fundamental Problems Technol Dept Biomed Engn Bioopt Grp 27 Wybrzeze S Wyspianskiego St Wroclaw Poland QUANTUP 30-9 Litewska St Wroclaw Poland Res Inst Hort Agrotech Dept Rhizosphere Lab 1-3 Konstytucji 3 Maja St Skierniewice Poland Warsaw Univ Life Sci SGGW Fac Appl Informat & Math 159 Nowoursynowska St Warsaw Poland Univ Western Australia Sch Comp Sci & Software Engn 35 Stirling Highway Perth WA 6009 Australia Wroclaw Univ Environm & Life Sci Clin Inject Dis Dept Epizootiol & Vet Adm 45 Grunwaldzki Sq Wroclaw Poland

The potential use of a novel multichannel optical system towards fast and nondestructive bacteria identification and its application for environmental bacteria characterisation on the strain level is presented. It is the first attempt to use the proposed optical method to study various bacteria species (Gram-negative, Gram-positive) commonly present in the environment. The novel configuration of the optical system enables multichannel examination of bacterial colonies and provides additional functionality such as registration of two-dimensional (2D) distribution of monochromatic transmission coefficient of examined colonies, what can be used as a novel optical signature for bacteria characterization. Performed statistical analysis indicates that it is possible to identify representatives of environmental soil bacteria on the species level with the 98.51% accuracy and in case of two strains of Rahnella aquatilis bacteria on the strain level with the 98.8% accuracy. The proposed method is an alternative to the currently used preliminary bacteria examination in environment safety control with the advantage of being fast, reliable, nondestructive and requiring minimal sample preparation. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： image processing image processing algorithms Light diffraction Light transmission Ptychography Transmission coefficient

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Optimization of stereoscopic imager performance by computer simulation of geometrical calibration using optical design software

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OPTICS EXPRESS 2019年第13期27卷 17819-17839页

作者： Gorevoy, Alexey, V Machikhin, Alexander S. Batshev, Vladislav, I Kolyuchkin, Vasiliy Ya Russian Acad Sci Sci & Technol Ctr Unique Instrumentat Lab Acoustoopt Spect 15 Butlerova Str Moscow 117342 Russia Natl Res Univ Moscow Power Engn Univ Inst Automat & Comp Engn Dept Elect Engn & Introscopy 14 Krasnokazarmermaya Str Moscow 111250 Russia Bauman Moscow State Tech Univ Dept Radioelect & Laser Technol 5 2 Ya Baumanskaya Str Moscow 105005 Russia

Stereoscopic imagers are widely used in machine vision for three-dimensional (3D) visualization as well as in non-destructive testing for quantitative characterization of cracks, delamination and other defects. Measurement capability in these systems is provided by a proper combination of the optical parameters and data processing techniques. Conventional approach to their design consists of two sequential stages: optical system design and optimization of calibration and image processing algorithms. Such two-stage procedure often complicates both the hardware and the software, and results in a time-ineffective design procedure and cost-ineffective solution. We demonstrate a more effective approach and propose to estimate errors of 3D measurements at the early optical design stage. We show that computer simulation using optical design software allows not only optimizing optical parameters of the imager but also choosing the most effective mathematical model of the system and the equipment necessary for calibration. We tested the proposed approach on the design of miniature prism-based stereoscopic system and analyzed the impact of various factors (aberrations, tolerances, etc.) as on the image quality, so on the quality of calibration and 3D measurements accuracy. The proposed joint design approach may be highly effective for various measurement systems and applications when both optical parameters and image processing algorithms are not defined in advance and are necessary to be optimized. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： Camera calibration Digital image processing image processing algorithms image quality Optical design software Optical systems

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