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- 摘要
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Linking luminance and lightness by global contrast normalization
摘要： In the present experiment we addressed the question of how the visual system determines surface lightness from luminances in the retinal image. We measured the perceived lightness of target surfaces that were embedded in custom-made checkerboards. The checkerboards consisted of 10 by 10 checks of 10 different reflectance values that were arranged randomly across the board. They were rendered under six viewing conditions including plain view, with a shadow-casting cylinder, or with one of four different transparent media covering part of the board. For each reflectance we measured its corresponding luminance in the different viewing conditions. We then assessed the lightness matches of four observers for each of the reflectances in the different viewing conditions. We derived predictions of perceived lightness based on local luminance, Michelson contrast, edge integration, anchoring theory, and a normalized Michelson contrast measure. The normalized contrast measure was the best predictor of surface lightness and was almost as good as the actual reflectance values. The normalized contrast measure combines a local computation of Michelson contrast with a region-based normalization of contrast ranges with respect to the contrast range in plain view. How the segregation of image regions is accomplished remains to be elucidated.
关键词： lightness/brightness perception,contrast,segmentation,surface reflectance
更新于2025-09-04 15:30:14
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Color and brightness encoded in a common L- and M-cone pathway with expansive and compressive nonlinearities
摘要： Lights near 560 nm appear brighter when flickered, whereas lights near 520 or 650 nm appear yellower. Both effects are consistent with signal distortion within the visual pathway—brightness changes at an expansive nonlinearity, and hue shifts at a compressive one. We previously manipulated the distortion products generated by each nonlinearity to extract the temporal properties of stages of the L- and M-cone pathways that signal brightness and color before (early stages) and after (late stages) each nonlinearity. We find that the attenuation characteristics of the early and late stages are virtually identical in both pathways: The early temporal stage acts like a band-pass filter peaking at 10–15 Hz, while the late stage acts like low-pass filter with a cut-off frequency near 3 Hz. We propose a physiologically relevant model that accounts for the filter shapes and incorporates both nonlinearities within a common parvocellular pathway. The shape of the early band-pass filter is consistent with antagonism between center signals and more sluggish and delayed surround signals, while the late filter is consistent with a simple two-stage low-pass filter. Modeling suggests that the brightness change and hue shift are both initially caused by the half-wave rectification and partition of signals into ON and OFF components. However, the hue shift is probably caused by the additional effects of a later nonlinearity that compresses chromatic red and green signals. Plausible sites for the expansive half-wave rectifying nonlinearity are after surround antagonism, possibly from horizontal cells, but the compressive nonlinearity is likely to be after the late filter.
关键词： lightness/brightness,color,nonlinearity,temporal vision,flicker sensitivity,vision models
更新于2025-09-04 15:30:14
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Imaging With 3-D Aperture Synthesis Radiometers
摘要： The spatial resolution is still a problem in passive microwave remote sensing, especially in low frequency. In recent years, the satellite formation flying has been proposed. Based on this technique, a large array is able to be synthesized in orbit to achieve higher spatial resolution. However, it is a big challenge for the control system to constrain all the satellites in a coplane in orbit. The 3-D array configuration is a good choice for a synthesized array based on satellite formation flying. In this paper, the complete formulation of visibility functions, including system imperfections, in a 3-D aperture synthesis radiometer (3-D ASR) is derived. The array factor of a 3-D ASR is defined. The reconstructed modified brightness temperature (BT) is a 3-D linear convolution of the modified BT and the array factor. Based on this relationship, the reconstruction method for a practical 3-D ASR is studied. The numerical results demonstrate that the reconstruction method is correct and stable. Finally, a discussion is given to analyze several existing methods that were proposed to reconstruct BT image for 3-D arrays in radio astronomy and earth observation. Compared with these existing methods, our imaging method is more suitable for earth observation based on the technique of satellites formation flying in low earth orbit. In addition, according to the derivations, some mature techniques that were developed for 2-D ASRs may be applied to 3-D ASRs.
关键词： visibility functions,image reconstruction,array factor,3-D aperture synthesis radiometers (3-D ASRs),modified brightness temperature (BT)
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE 7th Global Conference on Consumer Electronics (GCCE) - Nara, Japan (2018.10.9-2018.10.12)] 2018 IEEE 7th Global Conference on Consumer Electronics (GCCE) - Introduction of using Unified Glare Rating for visual comfort evaluation considering the brightness difference between VDT and its ambience
摘要： In order to determine a more comfortable brightness of a video display terminal (VDT), a preliminary investigation was carried out. The result shows the difference of brightness between VDT and ambient, as a factor used to affect visual comfort, is more important than brightness of VDT. For lamp system, Unified Glare Rating (UGR) is used to evaluate the influence of luminous on visual comfort. In this paper, an formula to evaluate the influence of the difference of the display equipment and the ambient brightness on visual comfort of VDT is introduced. The evaluation formula are verified by a test of 20 sample and proved to be basically feasible. More experiments will be carried out in order to get further validation or more correction factors.
关键词： ambient,visual,display,brightness,comfort,UGR
更新于2025-09-04 15:30:14
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Indolizine-Cyanine Dyes: Near Infrared Emissive Cyanine Dyes with Increased Stokes Shifts
摘要： Molecular engineering strategies designed to red-shift cyanine dye absorptions and emissions further into the near infrared (NIR) spectral region are explored. Through the use of a novel donor group, indolizine, with varying cyanine bridge lengths, dye absorptions and emissions were shifted deeper into the NIR region than common indoline-cyanines. Stokes shifts resulting from intramolecular steric interactions of up to ~60 nm in many cases were observed and explained computationally. Molecular brightnesses of up to 5,800 deep into the NIR region were observed. Structure-property relationships are explored for the 6 indolizine-cyanine dyes with varying cyanine bridge length and indolizine substituents showing broad absorption and emission tunability. The dyes are characterized by crystallography, and the photophysical properties are probed by varying solvent for absorption and emission studies. Computational data show involvement of the entire indolizine π-system during light absorption, which suggests these systems can be tunable even further into the NIR region through select derivatizations.
关键词： Photophysical Properties,Stokes Shifts,Near Infrared Emissive,Molecular Brightness,Indolizine-Cyanine Dyes
更新于2025-09-04 15:30:14
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Detection of high flux synchrotron radiation based on diamond detector for HEPS
摘要： High Energy Photon Source (HEPS) with a beam energy of 6 GeV and emittance less than 1.0 nm rad will be constructed in China, which can provide high-brightness hard X-ray in the order of 1022 (phs/s/mm2/mr2/0.1%B.W.). The broadband and high-brightness monochromatic beam flux and white beam flux need new detector other than the ion chambers for measurement in case of saturation under high-flux conditions. The Diamond X-ray detector for the beam position monitoring and high brightness X-ray detection is developing for High Energy Photon Source in China. The diamond detector has advantages over other detector materials: a low atomic number resulting in a low absorption cross-section when used as beam position monitor and a high radiation and wide linear range when used as beam intensity measuring. In this paper, the polycrystalline chemical-vapour-deposition diamond detectors with an aluminium contact have been tested at 1W2B beamline at Beijing Synchrotron Radiation Facility (BSRF). A transmission-mode diamond X-ray detector is designed to simultaneously measure the X-ray flux, beam position in real time.
关键词： HEPS,High brightness synchrotron radiation,Beam position,Diamond detector
更新于2025-09-04 15:30:14
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Variance Based Brightness Preserved Dynamic Histogram Equalization for Image Contrast Enhancement
摘要： This paper proposes a novel variant of Brightness Preserving Dynamic Histogram Equalization (BPDHE) having more brightness preserving capability with less computational time. This variant, called Variance based Brightness Preserve Dynamic Histogram Equalization (VBBPDHE) uses the interclass and intraclass variance information to segment out the histogram recursively. This variant does not need the smoothing operation of input histogram and also no need to compute local maxima or minima to segment out the histogram unlike BPDHE. Visual analysis, quality metrics and execution time clearly demonstrate the efficiency of the proposed VBBPDHE over well-known existing methods.
关键词： variance,color,image contrast enhancement,histogram equalization,brightness preservation
更新于2025-09-04 15:30:14
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Towards a user preference model for interior lighting Part 1: Concept of the user preference model and experimental method
摘要： The objective and subjective factors influencing human-centric lighting design and their effect on the user of the lighting system are analysed with the aim of developing a user preference model. It is discussed how to apply this user preference model in the Internet of Things network structure of luminaires in order to obtain an ‘Internet of Luminaires’ for good user acceptance. The method of a visual experiment intended to elucidate these concepts and contribute to the user preference model is described. In the experiment, subjects assessed scene brightness, visual clarity, colour preference and scene preference in a real room. Modelling equations of these attributes will be shown and discussed in Part 2 of this work.
关键词： human-centric lighting,user preference model,colour preference,scene preference,visual clarity,scene brightness,Internet of Luminaires
更新于2025-09-04 15:30:14