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Distance-based generation of a unicursal random path on a non-grid point set for optical polishing

APPLIED OPTICS 2023年第27期62卷 7288-7298页

作者： Feng, Yunpeng Cheng, Haobo Zhang, Shaohua Beijing Inst Technol Sch Opt & Phon Beijing 100086 Peoples R China Beijing Inst Technol Shenzhen Res Inst Shenzhen 518057 Guangdong Peoples R China Beijing Inst Technol Sch Mech Engn Beijing 100086 Peoples R China

In modern ultra-precision polishing, sub-aperture technologies are prone to mid-spatial frequency errors due to identical patterns of a path. A random tool path on a regular point set is widely used to suppress mid-spatial frequency errors. In this study, two non-grid uniform point sets, the Fibonacci and the three-directional, were introduced into optical polishing. To solve the time-consuming problem caused by a large amount of distance calculation, a distance-based weighted random (DBWR) algorithm and a linear programming and connecting (LPC) algorithm were presented. The DBWR algorithm reduces the generation time by strengthening the weight of the neighboring points in a specific direction, while the LPC algorithm adjusts the order and distance of points artificially. Then a random stitching method was proposed for the large-scale point set applying to large-sized optical surfaces, which dramatically reduced the generation time. Finally, experiments validated that the algorithms for non-grid sets can be effectively used for optical surface figuring without introducing an apparent mid-spatial frequency.(c) 2023 Optica Publishing Group

关键词： Fast Fourier transforms Freeform surfaces Magnetorheological finishing modulation transfer function Optical components Optical surfaces

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Design and Performance Verification of a LWIR Zoom Camera for Drones

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CURRENT OPTICS AND PHOTONICS 2023年第4期7卷 354-361页

作者： Park, Kwang-Woo Choi, Jonghwa Kang, Jian Agcy Def Dev Daejeon 34186 South Korea

We present the optical design and experimental verification of resolving performance of a 3x long wavelength infrared (LWIR) zoom camera for drones. The effective focal length of the system varies from 24.5 mm at the wide angle position to 75.1 mm at the telephoto position. The design specifications of the system were derived from ground resolved distance (GRD) to recognize 3 m x 6 m target at a distance of 1 km, at the telephoto position. To satisfy the system requirement, the aperture (f-number) of the system is taken as F/1.6 and the final modulation transfer function (MTF) should be higher than 0.1 (10%). The measured MTF in the laboratory was 0.127 (12.7%), exceeds the system requirement. Outdoor targets were used to verify the comprehensive performance of the system. The system resolved 4-bar targets corresponding to the spatial resolution at the distance of 1 km, 1.4 km and 2 km.

关键词： Airborne camera Ground resolve distance Long wavelength infrared modulation transfer function Signal noise ratio

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A generalized physics-based correction for adjacency effects

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APPLIED OPTICS 2025年第10期64卷 2719-2743页

作者： Castagna, Alexandre Vanhellemont, Quinten Univ Ghent Protistol & Aquat Ecol Krijgslaan 281 B-9000 Ghent Belgium Royal Belgian Inst Nat Sci Operat Directorate Nat Environm Vautierstr 29 B-1000 Brussels Belgium

Atmospheric scattering occurs over a horizontal scale of several kilometers. This results in influence from neighboring surface features on the signal recorded over a given position, reducing contrast and the accuracy of quantitative retrievals of surface reflectance from satellite imagery. This atmospheric blurring, or adjacency effect, must be accounted for when both contrast in surface reflectance and magnitude of atmospheric scattering are significant. Taking into account the adjacency effect is of particular importance for aquatic remote sensing of inland and coastal waters due to the high contrast between water and different land cover types, as well as the small spatial scale of most inland water bodies. In this paper, we present a physics-based processor to retrieve surface reflectance over all surface types, regardless of the subscene composition and sensor waveband configuration. The processor is implemented in the free and open source ACOLITE software and is composed of two modules: (1) TSDSF for the estimation of aerosol properties and (2) RAdCor for the retrieval of surface reflectance. We demonstrate the performance of the TSDSF + RAdCor processor for the Operational Land Imager (OLI) onboard Landsat 8 and the Multispectral Instrument (MSI) onboard Sentinel-2A and 2B over a set of small (<1 km2) inland waters in Belgium, and compare the performance with other common processors for these sensors, including C2RCC, POLYMER, Sen2Cor, iCOR, ACOLITE/DSF, and LaSRC. For clear sky matchups, the relative deviation against in situ data in the visible wavebands ranged between 6% and 18% for OLI, and between 14% and 31% for MSI, except for the MSI waveband centered at 443 nm where the relative deviation was 70%. In the near-infrared wavebands, the relative deviation varied from 70% to 150%, with the exception of the MSI waveband centered at 704 nm, for which the performance was 17%. Overall, the new processor outperformed the other evaluated processors in the visi

关键词： Atmospheric correction Atmospheric properties Fourier transforms modulation transfer function Rayleigh scattering Remote sensing

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Temporal fluctuations in defocus may reverse the acuity loss encountered with induced refractive errors

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION 2023年第11期40卷 2008-2018页

作者： Goswami, Sabyasachi Bharadwaj, Shrikant R. LV Prasad Eye Inst Brien Holden Inst Optometry & Vis Sci Rd 2 Hyderabad 500034 Telangana India LV Prasad Eye Inst Hyderabad Eye Res Fdn Prof Brien Holden Eye Res Ctr Rd 2 Hyderabad 500034 Telangana India

A recent template-matching model hypothesized that simulated visual acuity loss with uncorrected refractive errors maybe recovered by adding temporal defocus fluctuations up to the magnitude of the refractive error. Acuity recovery saturates or gets attenuated beyond this magnitude. These predictions were confirmed for monocular high-contrast visual acuity of 10 young, cyclopleged adults with 0.5-2.0D of induced myopia combined with the same range of temporal defocus fluctuations at 4.0 Hz frequency. The outcomes reinforce that spatial resolution may be optimized by averaging time-varying defocus over the entire stimulus presentation epoch or around the point of least defocus within this epoch. (c) 2023 Optica Publishing Group

关键词： Deformable mirrors Image metrics modulation transfer function Optical manipulation Refractive anomalies Spatial resolution

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Intraocular composition of higher order aberrations in non-myopic children

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BIOMEDICAL OPTICS EXPRESS 2023年第3期14卷 1276-1291页

作者： Hughes, Rohan P. J. Read, Scott A. Collins, Michael J. Vincent, Stephen J. Queensland Univ Technol QUT Ctr Vis & Eye Res Sch Optometry & Vis Sci Contact Lens & Visual Opt Lab Brisbane Qld 4059 Australia

This study examined anterior corneal, internal ocular, and total ocular higher order aberrations (HOA's), and retinal image quality in a non-myopic, paediatric cohort. Anterior corneal aberrations were derived from corneal topography data captured using a Placido disk videokeratoscope (E300, Medmont International), and whole eye HOA's were measured using a Hartmann-Shack wavefront sensor (COAS-HD, Wavefront Sciences). The associations between HOA's and age, sex, refractive error, and axial length were explored using correlation analyses. Data for 84 children aged between 5 and 12 years (mean +/- standard deviation spherical equivalent refraction (SER), +0.63 +/- 0.35 D;range 0.00 to +1.75 D) were included, and an eighth order Zernike polynomial was fit for 4 and 6 mm pupil diameters for both the anterior corneal and total ocular HOA's, from which internal ocular HOA's were calculated via subtraction following alignment to a common reference axis (pupil centre). Internal ocular HOA's were of greater magnitude than previous studies of adolescents and adults, however partial internal "compensation" of HOA's was observed, which resulted in reduced levels of HOA's and excellent retinal image quality. Few significant associations were observed between HOA's and age, SER, and axial length (all correlations, p > 0.001), and there were minimal sex-based differences (all comparisons, p > 0.005). Coefficients for vertical coma (C-1 3 and C-1 5 ) and spherical aberration (C40 and C60), were most strongly associated with the visual Strehl ratio based on the optical transfer function (VSOTF), which indicated that the absolute magnitudes of these Zernike coefficients have the greatest impact on retinal image quality in this paediatric cohort. These findings provide an improved understanding of the optics and retinal image quality of children's eyes.(c) 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

关键词： Image quality modulation transfer function Optical transfer functions Refractive anomalies Spherical aberration Zernike polynomials

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Influence of substrate material and geometric features of measurement slits on the measurement results of infrared optical system quality characteristics

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JOURNAL OF OPTICAL TECHNOLOGY 2023年第7期90卷 384-389页

作者： Leonov, M. B. Terletskiy, E. S. Seregin, D. A. Kometa Corp Electro Opt Surveillance Syst St Petersburg Russia

Subject of study. The influence of geometric characteristics and manufacturing technology, as well as the optical characteristics of their substrate material on the results of the line spread functions and modulation transfer measurements of long-wave infrared spectral range lenses, is studied. The aim of the study is to minimize the measurement error of these functions arising from measurement slit characteristics. Method. The theoretical computation method is used to determine the measurement error of the modulation transfer function arising from the geometrical characteristics of the measurement slits and pinhole. A practical computation method consisting of multiple measurements of the reference lens and a comparison between the measurement results and optical calcu-lations is applied to determine the measurement error of the line spread function and modulation transfer function of the reference lens, arising from the effect of the slit substrate material. Main results. The influence of the geo-metric features of the measurement slits and pinholes on the results of the line spread function and the modulation transfer function measurements is considered: the concept of the apparatus line spread function as a convolution of the true point spread function or line spread function with spatial functions of the measurement and object slits is defined. This study presents the construction of the calculation formulas of the absolute error to define the cor-rection coefficient for the finite size of the slits and pinholes used for evaluating the modulation transfer function according to the measured line spread functions. A reasonable error of the slit or pinhole size for the minimization of the modulation transfer function error is defined. The influence of the slit substrate materials (zinc selenide, calcium fluoride, and barium fluoride) as well as the metallic slit on the measurement results of the line spread function and the reference lens modulation transfer funct

关键词： Fluoride Fourier transforms modulation transfer function Optical systems Optical transfer functions Zinc selenide

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Carbon nanotube-based multiple source C-arm CT system: feasibility study with prototype system

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OPTICS EXPRESS 2023年第26期31卷 44772-44797页

作者： Moon, Seunghyuk Kang, Jungsu Kim, Youngkwang Jo, Eunha Jeong, Pilsoo Roh, Youngjun Baek, Jongduk Yonsei Univ Sch Integrated Technol Seoul South Korea KohYoung Technol Yongin South Korea Yonsei Univ Coll Comp Dept Artificial Intelligence Seoul South Korea Bareunex Imaging Seoul South Korea

To extend the field of view while reducing dimensions of the C-arm, we propose a carbon nanotube (CNT)-based C-arm computed tomography (CT) system with multiple X-ray sources. A prototype system was developed using three CNT X-ray sources, enabling a feasibility study. Geometry calibration and image reconstruction were performed to improve the quality of image acquisition. However, the geometry of the prototype system led to projection truncation for each source and an overlap region of object area covered by each source in the two-dimensional Radon space, necessitating specific corrective measures. We addressed these problems by implementing truncation correction and applying weighting techniques to the overlap region during the image reconstruction phase. Furthermore, to enable image reconstruction with a scan angle less than 360 degrees, we designed a weighting function to solve data redundancy caused by the short scan angle. The accuracy of the geometry calibration method was evaluated via computer simulations. We also quantified the improvements in reconstructed image quality using mean-squared error and structural similarity. Moreover, detector lag correction was applied to address the afterglow observed in the experimental data obtained from the prototype system. Our evaluation of image quality involved comparing reconstructed images obtained with and without incorporating the geometry calibration results and images with and without lag correction. The outcomes of our simulation study and experimental investigation demonstrated the efficacy of our proposed geometry calibration, image reconstruction method, and lag correction in reducing image artifacts.

关键词： Computed tomography Computer simulation modulation transfer function Phase imaging Projection systems Systems design

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Using reflectometry to minimize the dependence of fluorescence intensity on optical absorption and scattering

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BIOMEDICAL OPTICS EXPRESS 2023年第10期14卷 5499-5511页

作者： Arias, Augusto Anastasopoulou, Maria Gorpas, Dimitris Ntziachristos, Vasilis Tech Univ Munich Sch Med Chair Biol Imaging Cent Inst Translat Canc Res TranslaTUM D-81675 Munich Germany Helmholtz Zentrum Munchen Inst Biol & Med Imaging D-85764 Neuherberg Germany DZHK German Ctr Cardiovasc Res Partner Site Munich Heart Alliance D-81675 Munich Germany

The total diffuse reflectance RT and the effective attenuation coefficient Neff of an optically diffuse medium map uniquely onto its absorption and reduced scattering coefficients. Using this premise, we developed a methodology where RT and the slope of the logarithmic spatially resolved reflectance, a quantity related to Neff, are the inputs of a look-up table to correct the dependence of fluorescent signals on the media's optical properties. This methodology does not require an estimation of the medium's optical property, avoiding elaborate simulations and their errors to offer accurate and fast corrections. The experimental demonstration of our method yielded a mean relative error in fluorophore concentrations of less than 4% over a wide range of optical property variations. We discuss how the method developed can be employed to improve image fidelity and fluorochrome quantification in fluorescence molecular imaging clinical applications.

关键词： Attenuation coefficient Imaging systems modulation transfer function Optical absorption Optical properties Tissue optics

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Pupil-difference moments for estimating relative modulation from general mid-spatial frequency surface errors

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OPTICS LETTERS 2023年第9期48卷 2492-2495页

作者： Demars, Luke A. Suleski, Thomas J. Univ N Carolina Dept Phys & Opt Sci Charlotte NC 28223 USA

Standard surface specifications for mid-spatial frequency (MSF) errors do not capture complex surface topography and often lose critical information by making simplifying assumptions about surface distribution and statistics. As a result, it is challenging to link surface specifications with optical performance. In this work, we present use of the pupil-difference probability distribution (PDPD) moments to assess general MSF surface errors and show how the PDPD moments relate to the relative modulation.(c) 2023 Optica Publishing Group

关键词： Fourier transforms modulation modulation transfer function Optical surfaces Power spectral density Spatial frequency

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Human-vision-inspired cluster identification for single-molecule localization microscopy

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OPTICS EXPRESS 2023年第3期31卷 3459-3466页

作者： Chen, Lei Liu, Qian Chou, Keng C. Univ British Columbia Dept Chem Vancouver BC V6T1Z1 Canada Jinan Univ Coll Sci & Engn Guangzhou Peoples R China McGill Univ Inst Parasitol Montreal PQ H9X 3V9 Canada

Single-molecule localization microscopy has enabled scientists to visualize cellular structures at the nanometer scale. However, researchers are facing great challenges in analyzing images presented by point clouds. Existing algorithms for cluster identification are coordinate -based analyses requiring users to input cutoff thresholds based on the distance or density of the point cloud. These thresholds are often one's best guess with repeated visual inspections, making the cluster assignment user-dependent. Here, we present a cluster identification algorithm mimicking the modulation transfer function of human vision. This approach does not require any input parameters and produces visually satisfactory cluster assignments. We tested this algorithm by identifying the clusters of the fusion proteins of the Nipah virus on its host cells. This algorithm was further extended to analyze three-dimensional point clouds using virus-like particles as an example.(c) 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

关键词： Clouds Edge detection Fourier transforms Microscopy modulation transfer function Point spread function

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