US PATENT SUBCLASS 359 / 559
.~ Using Fourier transform spatial filtering

Current as of: June, 1999
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359 /   HD   OPTICS: SYSTEMS (INCLUDING COMMUNICATION) AND ELEMENTS

558  DF  DIFFRACTION {3}
559.~ Using Fourier transform spatial filtering {5}
560  DF  .~.~> For convolution (cross-correlation)
561  DF  .~.~> For correlation
562  DF  .~.~> For changing zeroth order intensity
563  DF  .~.~> With diffraction grating
564  DF  .~.~> With photographic media

DEFINITION

Classification: 359/559

Using Fourier transform spatial filtering:

(under subclass 558) Subject matter wherein an optical

Fourier transform is taken of a diffracted beam of light and a spatial filter is placed at the Fourier transform plane to spatially limit the output optical wave to those having Fourier transform coefficients passed by the filter.

(1) Note. A spatial filter is generally an emulsion mask having a transparent annular region in an otherwise opaque region used to eliminate undesired radiation that diverges from the optical axis beyond the confines of the transparent region.

(2) Note. A spatial filter is sometimes referred to as a mask used as an aperture to cause diffraction of the light beam passing therethrough.

(3) Note. A Fourier transform of a wave function is the amplitude representation of the components of each fre-quency of a given wavefront.

(4) Note. Amplitude and phase information over a discrete spatial area of the diffracted energy pattern is obtained by placing a lens at one focal length from the aperture to produce a "Fourier Transform", and the aperture at the second focal plane of the lens creates a diffraction pattern.

SEE OR SEARCH THIS CLASS, SUBCLASS:

29, for Fourier transform holography. SEE OR SEARCH CLASS

382, Image Analysis,

181+, for pattern recognition where an image analyzing system possesses the capability of identifying discrete patterns, subclasses 210+ for spatial filtering wherein the optical image of each pattern to be recognized is transformed into a light amplitude distribution that is proportional to the two dimensional Fourier Transform of the pattern image, subclasses 276+ for mathematical image transformation or pre-recognition processing transformation of an image into another representation to facilitate the acquisition or subsequent recognition of imaging patterns, and subclasses 280+ for Fourier, Hadamard, or Walsh Transform of an image prior to the recognition processing.

708, Electrical Computers: Arithmetic Processing and Calculating,

821, for Fourier transform computation in electrical analog computers.