Optical reader and character identification system utilizing a two-dimensional diffracting means

Claim 1

A character identification system comprising: a source of collimated coherent light; a substantially plane surface having relatively opaque and transparent portions defining a character to be identified, said surface being positioned to intercept said collimated coherent light; a two-dimensional diffraction means positioned in the path of the collimated coherent light passing through said relatively transparent portions for forming a plurality of spatially disposed diffraction patterns of said character to be identified; first optical means having a determinable focal length and positioned one focal length from said surface for forming a far-field image of said plurality of diffraction patterns; a filter positioned one focal length from said first optical means substantially at said, far-field image, and being divided into a plurality of spaced discrete areas, each said area having relatively opaque and transparent portions defining the diffraction pattern of a known character; second optical means having a determinable focal length and positioned one focal length from said filter; and a plurality of light-responsive means positioned in an off-axis plane one focal length from said second optical means, each of said light-responsive means being spatially disposed in said plane at a position commensurate with a related discrete area of said filter for producing a signal in response to a predetermined amplitude of light impinging thereon.