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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: A comparison of the performance of three frequency-domain real filters: square root, Foucault, and Hoffman is presented, which shows that the square-root filter is the first derivative of the object phase function.
Abstract: Methods of imaging phase objects are considered. First the square-root filter is inferred from a definition of fractional-order derivatives given in terms of the integration of a fractional order called the Riemann-Liouville integral. Then we present a comparison of the performance of three frequency-domain real filters: square root, Foucault, and Hoffman. The phase-object imaging method is useful as a phase-shift measurement technique under the condition that the output image intensity is a known function of object phase. For the square-root filter it is the first derivative of the object phase function. The Foucault filter, in spite of its position, gives output image intensities expressed by Hilbert transforms. The output image intensity obtained with the Hoffman filter is not expressed by an analytical formula. The performance of the filters in a 4f imaging system with coherent illumination is simulated by use of VirtualLab 1.0 software.

24 citations

Journal ArticleDOI
TL;DR: This work shows experimental results for image processing using an acousto-optic light modulator (AOLM) where the image can be edge enhanced with respect to the input object and relates this technique to the fractional Hilbert transform and the fractionsal derivative image-processing operations.
Abstract: We show experimental results for image processing using an acousto-optic light modulator (AOLM) where the image can be edge enhanced with respect to the input object. We can select which edges are enhanced and the degree to which they are enhanced by changing the amplitude of the acoustic wave of the AOLM. We relate this technique to the fractional Hilbert transform and the fractional derivative image-processing operations and discuss its application to phase-only input images.

24 citations

Journal ArticleDOI
01 Aug 1995
TL;DR: Quantitative simulation results indicate that the MPEG compression throughput is greatly improved by digital resampling and spatial filtering without significant loss of image quality.
Abstract: Spatial filtering is an effective method for improving MPEG compression in fixed and variable rate control applications. This paper presents a unique architecture for adaptive spatial filtering based on digital resampling that improves MPEG compression throughput. An overview of a digital resampling and an adaptive spatial filtering system is also presented. Quantitative simulation results indicate that the MPEG compression throughput is greatly improved by digital resampling and spatial filtering without significant loss of image quality. >

24 citations

Patent
09 Feb 1996
TL;DR: In this article, a spatial filter is selectively positioned between a hybrid fore-optic and a hybrid reimaging optic, both of which include a diffractive optic, to obtain the proper positioning of the spatial filter relative to the intermediate image.
Abstract: Disclosed is a tunable multispectral optical apparatus for forming a spectrally processed image of a scene having finite angular extent or alternatively a point source of light, both of which may include multispectral components. A spatial filter is selectively positioned between a hybrid fore-optic and a hybrid reimaging optic, both of which include a diffractive optic. Spectral selectivity is obtained by proper positioning of the spatial filter relative to the intermediate image formed by the hybrid fore-optic before impinging on the hybrid reimaging optic. The tunable multispectral optical apparatus of the present invention may take the form of a bandpass filter or a bandstop filter depending only on the choice of spatial filter--blocking or passing selective wavelength components of the intermediate image.

24 citations

Journal ArticleDOI
TL;DR: Application of spatial frequency filtering techniques gives powerful tools for the automation of screening of biomedical microsamples and experimental applications to cytological and cytogenetical samples are shown.
Abstract: Application of spatial frequency filtering techniques gives powerful tools for the automation of screening of biomedical microsamples. Band-pass filtering provides a size selection of objects, whereas high-pass filtering combined with a subsequent reduction of the field size enables the separation of the superposition of the field and the object spectrum. Besides the theoretical background and numerical evaluations, experimental applications to cytological and cytogenetical samples are shown.

24 citations


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