(under subclass 559) Subject matter wherein a series of very fine, closely spaced parallel slits, or of very narrow, parallel reflecting surfaces are included in the optical system, either before or at the Fourier transform plane in order to produce a successsion of spectra when light is incident thereon at a specific angle.
(1) Note. An example of a diffraction grating is a glass substrate carrying a layer of deposited aluminum that has been pressure-ruled with a large number of fine equidistant grooves, using a diamond edge as a tool.
(2) Note. Light falling on a diffraction grating is dispered into a series of spectra on both sides of the incident beam, the angular dispersion being inversely proportional to the line spacing.
(3) Note. Phase gratings using Fourier transform filtering also belongs in this subclass.
SEE OR SEARCH THIS CLASS, SUBCLASS:
1+, for holograms and holos:graphic systems.
560, for systems using a spatial filter placed at the Fourier transform plane for convolution (cross-correlation). 561, for systems using a spatial filter placed at the Fourier transform plane for correlation.
