Topic
Contrast (vision)
About: Contrast (vision) is a research topic. Over the lifetime, 10379 publications have been published within this topic receiving 221480 citations.
Papers published on a yearly basis
Papers
More filters
••
TL;DR: The contrast threshold for perception of square wave gratings as depending on spatial frequency is measured for varying viewing distances, adaptation and exposure time as mentioned in this paper, where the luminance varied between 14 and 110 cd/m2.
Abstract: The contrast threshold for perception of square-wave gratings as depending on spatial frequency is measured for varying viewing distances, adaptation and exposure time The luminance varied between 14 and 110 cd/m2; target distances were 1, 31, and 7 m Exposure times ranged from 15 msec to 1 sec and unlimited A distinct minimum threshold contrast is observed for a definite spatial frequency, which depends on the viewing distance and luminance A decrease in exposure time causes a less significant minimum Exposure times from 40 to 15 msec do not alter the curve decisively With exposure times less than 2 msec and spatial frequencies somewhat above 002 lines/min of arc the optical transfer function of the eye can be measured by determination of thresholds
88 citations
••
TL;DR: The internal noise of an image has been utilised to produce a noise-induced transition of a dark image from a state of low contrast to that of high contrast.
Abstract: In this study, a dynamic stochastic resonance (DSR)-based technique in spatial domain has been proposed for the enhancement of dark- and low-contrast images. Stochastic resonance (SR) is a phenomenon in which the performance of a system (low-contrast image) can be improved by addition of noise. However, in the proposed work, the internal noise of an image has been utilised to produce a noise-induced transition of a dark image from a state of low contrast to that of high contrast. DSR is applied in an iterative fashion by correlating the bistable system parameters of a double-well potential with the intensity values of a low-contrast image. Optimum output is ensured by adaptive computation of performance metrics - relative contrast enhancement factor ( F ), perceptual quality measures and colour enhancement factor. When compared with the existing enhancement techniques such as adaptive histogram equalisation, gamma correction, single-scale retinex, multi-scale retinex, modified high-pass filtering, edge-preserving multi-scale decomposition and automatic controls of popular imaging tools, the proposed technique gives significant performance in terms of contrast and colour enhancement as well as perceptual quality. Comparison with a spatial domain SR-based technique has also been illustrated.
88 citations
••
TL;DR: In this paper, the average contrast of image speckle patterns was used to measure surface roughness and correlation length of the objects from the experimental curve of the contrast variation versus the point spread of the imaging system.
Abstract: As a practical monitoring tool for measurements of surface roughness properties, a new instrument is actually constructed on the basis of using the average contrast of image speckle patterns. With this instrument an experimental investigation on the contrast variation of image speckle patterns is conducted systematically for various surface roughnesses of the objects under different conditions of an optical imaging system. It is found that the roughness and correlation length of the objects can be precisely determined from the experimental curve of the contrast variation versus the point spread of the imaging system. The present method using image speckle patterns is superior to the previous one which uses the contrast variation of speckle patterns in the diffraction field.
88 citations
••
TL;DR: It is suggested that STLASCA most effectively utilizes the number of pixels, thus achieving maximized speckle contrast, and thereby maximizing the variation of the laser speckel contrast image.
Abstract: Laser speckle contrast imaging is a technique used for imaging blood flow without scanning. Though several studies have attempted to combine spatial and temporal statistics of laser speckle images for reducing image noise as well as preserving acceptable spatiotemporal resolution, the statistical accuracy of these spatiotemporal methods has not been thoroughly compared. Through numerical simulation and animal experiments, this study investigates the changes in the mean speckle contrast values and the relative noise of the speckle contrast images computed by these methods with various numbers of frames and spatial windows. The simulation results show that the maximum relative error of the mean speckle contrast computed by the spatiotemporal laser speckle contrast analysis (STLASCA) method, in which the speckle contrast images are computed by analyzing the 3-D spatiotemporal speckle image cube, is approximately 5%, while it is higher than 13% for other methods. Changes in the mean speckle contrast values and the relative noise computed by these methods for animal experiment data are consistent with the simulation results. Our results demonstrate that STLASCA achieves more accurate speckle contrast, and suggest that STLASCA most effectively utilizes the number of pixels, thus achieving maximized speckle contrast, and thereby maximizing the variation of the laser speckle contrast image.
88 citations
•
23 Feb 2010TL;DR: In this article, a method is provided that obtains input to perform a color change to one or more instruments presented on a graphical display, for each instrument affected by the color change, a determination is made regarding whether a threshold level of contrast exists between a symbol graphic of the instrument and the background colors.
Abstract: Aspects of the disclosed subject matter are directed to customizing the colors of instruments that are used to convey vehicle readings. In accordance with one embodiment, a method is provided that obtains input to perform a color change to one or more instruments presented on a graphical display. For each instrument affected by the color change, a determination is made regarding whether a threshold level of contrast exists between a symbol graphic of the instrument and one or more background colors. If a threshold level of contrast does not exist, the contrast ratio between the symbol graphic and one or more background colors is adjusted to at least the threshold level. Then the method causes the graphical display to render the one or more instruments in accordance with the received color selections.
88 citations