Topic
Spatial filter
About: Spatial filter is a research topic. Over the lifetime, 6170 publications have been published within this topic receiving 100451 citations.
Papers published on a yearly basis
Papers
More filters
TL;DR: A technique for real-time joint spectral-spatial matched filtering that is able to use both color and shape in recognizing objects is presented.
31 citations
05 Jun 1996
TL;DR: A noise reduction IC for consumer television has been designed that contains a spatial filter for Gaussian noise and a temporal filter for clamp noise, and includes a noise level estimator for optimal filtering under varying reception conditions.
Abstract: A noise reduction IC for consumer television has been designed. The IC contains a spatial filter for Gaussian noise and a temporal filter for clamp noise. To reduce clamp noise, the average value of the pixels in a line-segment are filtered rather than individual pixels. This reduces the cost of the temporal filter significantly, enabling the use of embedded memory. Analog interfaces are provided, as well as a line-locked clock generator. The chip includes a noise level estimator for optimal filtering under varying reception conditions. The average gain of the spatial filter is around 3 dB, whereas the temporal filter yields up to 8 dB improvement on clamp noise.
31 citations
Patent•
24 Apr 1997
TL;DR: In this paper, a laser bar code symbol scanner embodying a narrow band-pass optical filtering system of novel construction is presented, where a first optical filter element is installed over the light transmission aperture of the scanner housing, and has wavelength selective properties which transmit only light having wavelengths from slightly below a predetermined wavelength in the visible band of the electromagnetic spectrum (e.g., greater than slightly below 670 nanometers).
Abstract: A laser bar code symbol scanner embodying a narrow band-pass optical filtering system of novel construction. A first optical filter element is installed over the light transmission aperture of the scanner housing, and has wavelength selective properties which transmit only light having wavelengths from slightly below a predetermined wavelength in the visible band of the electromagnetic spectrum (e.g., greater than slightly below 670 nanometers). A second optical filter element is installed within the housing, along the focused laser return light path between the light focusing element and the light detecting element, and transmits only light having wavelengths from slightly above the predetermined wavelength (e.g., less than slightly above 670 nanometers). Collectively, the first and second optical filter elements cooperate to form a narrow wavelength band-pass filtering system centered about the predetermined wavelength, providing improved signal-to-noise ratio. As a result of the present invention, aesthetically unappealing electro-optical components mounted within the scanner housing are hidden from plain view, while the optical filtering elements of the system can be easily and inexpensively manufactures and used without compromising the signal-to-noise ratio performance of the laser scanner.
31 citations
TL;DR: It is concluded that human testing is required to evaluate the filter effectiveness and that human perception models must be improved to account for the spatio-temporal filtering of image sequences.
Abstract: Digital temporal and spatial filtering of fluoroscopic image sequences can be used to improve the quality of images acquired at low X-ray exposure. In this study, we characterized a nonlinear edge preserving, spatio-temporal noise reduction filter, the bidirectional multistage (BMS) median filter of Arce (1991). To assess image quality, signal detection and discrimination experiments were performed on stationary targets using a four-alternative forced-choice paradigm. A measure of detectability, d', was obtained for filtered and unfiltered noisy image sequences at different signal amplitudes. Filtering gave statistically significant, average d' improvements of 20% (detection) and 31% (discrimination). A nonprewhitening detection model modified to include the human spatio-temporal visual system contrast-sensitivity underestimated enhancement, predicting an improvement of 6%. Pixel noise standard deviation, a commonly applied image quality measure, greatly overestimated effectiveness giving 67% improvement in d'. We conclude that human testing is required to evaluate the filter effectiveness and that human perception models must be improved to account for the spatio-temporal filtering of image sequences.
31 citations
TL;DR: Customized optical filtering and light-dependent neural filtering were implemented in an ideal-observer model for an L-alternative forced-choice visual task and were consistent with the experimental data in the assessment of the effect of HO aberrations as a function of light level.
Abstract: Customized optical filtering and light-dependent neural filtering were implemented in an ideal-observer model for an L-alternative forced-choice visual task. The model was applied to a contrast threshold visual task with adaptive optics correction of ocular higher-order (HO) aberrations under different light regimes, for which experimental data have previously been obtained (J. Mod. Opt.55, 791, 2008). A separability measure was used to assess the model-observer performance and to investigate the joint effect of optical and neural filtering. The numerical results were consistent with the experimental data in the assessment of the effect of HO aberrations as a function of light level.
31 citations