GB1394602A - Document reading apparatus - Google Patents

Abstract

1394602 Record reader DATA RECOGNITION Ltd 14 April 1972 17346/72 Addition to 1317885 Heading G4M [Also in Division H3] An optical record reader has light transmitted to a transparent plate 24A via optical fibres 42 and has optical fibres 43 transmitting reflected light to a photo-cell 52 on a printed circuit board 51. Light from a source 53 is transmitted to a plurality of positions via channels 47 and to a reference photo-cell 52. Reflected light from each position is transmitted to a respective photo-cell. The reference photo-cell is used to modify the supply to the light source to compensate for variations in intensity, e.g. due to ageing and to compensate for temperature variations varying the sensitivity of the transistors. Each record is pressed against a guide by angled rollers (Fig. 2, not shown), and passes over surface 24 of plate 24A. The record has locations preprinted in colours to which the reader is not sensitive and each required location is marked by a line through the location. Each mark is situated between two clock pulse marks 65a, 65b in a clock pulse track. A faulty mark has the lower half of a location blacked out and read circuitry is arranged to cancel this mark. The final clock pulse 67 is wider than usual and is detected by blanking out two adjacent windows (41b, 41c, Fig. 2, not shown), of the clock track reader. Pulses representing marked data are fed to two threshold detectors arranged to operate at different voltages, one representing a definite mark, the other a doubtful mark (Fig. 9, not shown). The outputs of both detectors may be stored and compared on read-out. An item of data having both marks is correct, one having only one mark is either rejected or referred to an operator for checking.