A bar code scanner employs a digitizer for the signal produced by a photodetector in response to light reflected from a bar code symbol. The digitizer uses a first derivative of the signal to detect peaks, and determines the amount of movement of the signal after each peak to see if a threshold amount...http://www.google.es/patents/US5272323?utm_source=gb-gplus-sharePatente US5272323 - Digitizer for barcode scanner
