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Spatial filter

About: Spatial filter is a research topic. Over the lifetime, 6170 publications have been published within this topic receiving 100451 citations.


Papers
More filters
Journal ArticleDOI
TL;DR: Using psychophysical masking, an analog to receptive field end stopping and length tuning in psychophysical spatial filters tuned to a wide range of spatial frequencies is demonstrated, suggesting that both first- and second-order visual processing is involved in end-stopped spatial filters.
Abstract: Psychophysical spatial filters or channels are usually modeled after simple-cell receptive fields, although many cortical cells are end stopped and length tuned. Using psychophysical masking, we demonstrate an analog to receptive field end stopping and length tuning in psychophysical spatial filters tuned to a wide range of spatial frequencies. Specifically, masking is maximal when the mask is approximately 5–6 arcmin longer than the target but is reduced when the mask exceeds this length, consistent with the properties of end-stopped cells. The strength and the extent of psychophysical end stopping appear to be determined by the filter’s spatial-frequency tuning, but length tuning varies with target length. The latter implies that spatial filters tuned to the same spatial frequency could have different length tuning and that there is no fixed length-to-width ratio of filter size. Phase effects suggest linear length summation but nonlinear psychophysical end stopping, which suggests that both first- and second-order visual processing is involved in end-stopped spatial filters.

30 citations

Patent
02 Jan 2004
TL;DR: In this article, the authors used a pump source to induce gain at the lasing threshold in a wide region, a spatially coherent monochromatic light beam is emitted perpendicular to the film surface from the entire gain region.
Abstract: Lasing at the edge of the reflection band or at a defect state within the reflection band of a thin one-dimensional feedback structure is used to create a large-area, thin-film laser source with transverse dimensions that can be much greater than the film thickness. Angular confinement of radiation propagating perpendicular to the layers leads to a spreading of the beam inside the medium which is much greater than the diffraction divergence. This enhances the spatial extent of correlation at the output surface of the thin film. When a pump source induces gain at the lasing threshold in a wide region, a spatially coherent monochromatic light beam is emitted perpendicular to the film surface from the entire gain region. Alternate embodiments of the present invention include a passive spatial filter and an active amplifier.

30 citations

Patent
21 Jun 1999
TL;DR: An optical inspection station for inspecting a substrate may include a first surface and a second surface as mentioned in this paper, where light reflected from both the first and second surfaces of the substrate is detected by a light detector and a controller may determine a surface characteristic of the first surface from the detected light.
Abstract: An optical inspection station for inspecting a substrate. The substrate may include a first surface and a second surface. Light is reflected from both the first and second surfaces of the substrate. The light reflected from the first surface is detected by a light detector. A controller may determine a surface characteristic of the first surface from the detected light. The system may include a spatial filter that filters the light reflected from the second surface. The spatial filter eliminates the optical noise that may be created by the light reflected from the second surface.

30 citations

Proceedings ArticleDOI
Sylvie Mayrargue1
27 Apr 1993
TL;DR: It is shown that a spatial filtering can recover the transmitted signals under two conditions, namely that both the number of sensors and the numberof paths be larger than the length of the intersymbol interference, which is assumed to be finite.
Abstract: The author considers the problem of signal recovery by a multisensor receiver in a multipath propagation channel. She shows that a spatial filtering can recover the transmitted signals under two conditions, namely that both the number of sensors and the number of paths be larger than the length of the intersymbol interference, which is assumed to be finite. Thereby, signal recovery is realized without beamforming, i.e. without forming a beam towards one of the paths while cancelling the others, which would require a number of sensors much larger than the number of paths. Spatial filtering is able to cancel a multipath jammer, provided that an additional number of sensors, equal to the ISI (intersymbol interference) length of the jammer, is available. The spatial filtering is obtained adaptively by a blind algorithm, the CMA, which relies on the property of the transmitted signal to have a constant modulus. Simulation results on the present spatial CMA were compared with results for a temporal single-sensor CMA. The latter failed to recover a correct signal constellation while spatial CMA succeeded, even in a noisy environment plus a jammer. >

30 citations

Patent
28 Sep 1989
TL;DR: In this article, a laterally unguided diffraction region in which light from a set of waveguides is re-imaged in accordance with the Talbot effect is used to provide a spatial filtering effect to select a desired array mode.
Abstract: A semiconductor laser array with features providing good beam quality at high powers, first by employing a laterally unguided diffraction region in which light from a set of waveguides is re-imaged in accordance with the Talbot effect and two arrays of waveguides may be used to provide a spatial filtering effect to select a desired array mode. This provides a laser array with increased power per unit solid angle, and with additional advantages of ability to scale the device up to larger arrays, ability to control the electrical excitation of the device for better optimization, and improved modal discrimination. A second aspect of the invention is the use of a resonance condition in an antiguide array, to produce a uniform near-field intensity pattern and improved coupling and device coherence. This resonance structure may be combined with the Talbot-effect structure to suppress the out-of-phase mode, or the out-of-phase mode may be suppressed by other means, such as by introducing interelement radiation losses or absorption losses in the antiguide array.

30 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202321
202265
202181
2020144
2019180
2018179