Spatial filter

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

SAR Image Despeckling Using a Space-Domain Filter With Alterable Window

Abstract: In this letter, a modified bilateral filter suitable for synthetic aperture radar (SAR) image despeckling, named space-domain filter with alterable window (SFAW), is proposed. SFAW features geometric adaptivity, in both spatial and similarity functions, respectively driven by the following: 1) the local coefficient of variation ( CV) and 2) the joint probability density function model of two pixels having the same reflectivity. Tests on synthetic and real SAR images show that SFAW notably smoothes speckle with unperceivable detail blurring and achieves better performances than other related methods.

Optical spatial filter

Abstract: An optical filter 10 for filtering spatial frequencies from an output of an optical imaging system comprises a substantially transparent, or reflective, optical element 12 having a plurality of light refracting, or reflecting, segments 18 arranged on a surface thereof. Each of the plurality of segments 18 is provided with a predetermined angle of refraction, or reflection, distinct from adjacently located segments 18, wherein the different angles of refraction, or reflection, and the arrangement of the segments 18 on the optical element 12, are determined based on a desired spatial frequency transfer function for the filter 10. The optical spatial filter 10 reduces errors in optically formed images by accurately confining a broadened Point Spread Function (PSF) to a desired spot size.

A new algorithm for SAR image despeckling using an enhanced Lee filter and median filter

Abstract: Speckle noise usually occurs in synthetic aperture radar (SAR) images , and SAR data is processed coherently. Speckle filters commonly are adaptive filters using local statistics such as mean and standard deviation, such as the Lee and its enhanced filters and median filter. They adapt the filter coefficients based on data within a fixed moving window, and this brings in contradiction between the quality of speckle noise suppression and the capability of preserving image details. The Lee filter decreases speckle noise well in homogeneous regions, and the enhanced filter performs well both in the homogeneous and heterogeneous areas. But it does not effectively maintain image edges and details, while depressing SAR image noise. The median filter does well in decreasing impulse noise. In this paper, we propose an improved algorithm fusing the enhanced Lee filter and median filter based on spatial filtering of SAR image speckle. The experiment proves it has a good performance in preserving edges and details while filtering images.

Arrangement for optical image processing

Abstract: For electro-optical image conversion as well as for optical image processing by spatial filtering, a two-dimensional optical filter is provided which comprises a microstructured grid, the openings of which are designed as a matrix of windows, the windows being provided with electrostatically movable thin-film closures. The window openings are controlled by electrostatic charges which are provided by an electron beam. This matrix of light valves can preferably be used as a electro-optical converter as well as a Fourier filter in an optical computer.

Optical correlator using electronic image preprocessing

Abstract: An optical processing system uses spatial filtering to recognize two-dimensional functions and images. Images of real objects are captured with a television camera. The electronic signals representing the two-dimensional function or image are electronically preprocessed, such as by edge enhancement techniques or by applying a curvature function, and displayed on a narrow-band-phosphor cathode ray tube or television monitor. The monitor image is used directly as the input to an incoherent holographic correlator. Alternatively, the monitor image is used to modulate a source of coherent radiation such as a laser via a spatial light modulator to generate a modulated optical signal which is the input to a coherent holographic correlator. Analyzer circuitry with an optical detector at the correlation plane analyzes the shape of the correlation function to determine the intensity and position of its peak. The input to the CRT or monitor may also be in the form of non-optically generated electronic signals representative of a two-dimensional function for display in graphic form by the CRT or monitor.