Optical recognition device for document identification markings - uses light reflection from photodetectors connected by optical fibres and outputs analysed by microprocessor to eliminate variation errors

摘要

The recognition device uses a light source (8) and a pair of photodetectors (9,10) each supplying a current corresponding to the light reflected from the document surface. The photodetectors (9,10) are coupled via respective amplifiers (11,12) to an A/D converter (15) in turn coupled to a microprocessor (17). The microprocessor obtains the difference between the photodetector outputs. The obtained difference values are subjected to an iteration process. The photodetectors (9,10) are located to either side of the light source (8) all three coupled via respective optical fibres to a light emission head and two reception heads (A,B) on each side. The use of two photodetectors eliminates error due to variations in the source light output.