GB1279819A - Improvements in and relating to character recognition - Google Patents

Abstract

1279819 Character recognition INTERNATIONAL BUSINESS MACHINES CORP 18 Nov 1969 [20 Nov 1968] 56310/69 Heading G4R [Also in Division G2] Characters arranged in predetermined positions on a record carrier are recognized by imaging the record carrier through each of a series of holographic filters in turn on to a matrix of photo-cells arranged in positions corresponding to the predetermined positions, and generating in response to detection by a photo-cell of light passed by such a filter a signal indicative of the character to which that filter corresponds. The holographic filters are arranged in series on a film strip and are passed in turn through the optical system. Each character on the record carrier produces a spot of light on a photo-cell having a position corresponding to that of the character on the record carrier, when the matching filter is in position. Each illuminated photocell gates a character-identifying code into a storage location respective to the character position in a store. A given filter can be produced by passing coherent monochromatic laser light to a fully-reflecting mirror to produce a parallel beam and through a lens to a semipermeable mirror to produce a convergent beam. The parallel beam passes through the semipermeable mirror, and the two beams, which are concentric, illuminate a mask having a charactershaped transmitting portion and a central spot aperture to which the convergent beam converges. The light passing through the mask passes to the film via a Fourier-transforming lens. Alternatively, the spot aperture could be outside the character so that, during recognition, the zero-order diffraction image of the record carrier will not be superposed on the first-order image of the spot on the photo-cell. A plurality of filters could be superposed, each producing a spot on a respective photo-cell or respective combination of photo-cells on recognition "match", or a plurality of filters could be arranged side-by-side on the film strip, being inserted into the light path in turn by a rotating mirror or prism. To differentiate between similar characters, filters may comprise two or more superposed holograms associated with common contours of the similar characters and significant feature(s) of one of the characters, respectively, having low and high scattering intensity respectively.