Passage of mobile object detection process - using optical scanning and comparison of bar=code targets which may be obstructed by moving object

摘要

The process involves repetitive optical scanning of a bar-code target (14) to allow detection of the passage of an object (10) with a fixed path of motion between the scanning appts. (16) and a bar-code target (14). The target (14) carries a unique bar-code (16) on its upper half and the complementary code pattern (18) on its lower half. Both codes are scanned simultaneously and a difference signal is formed electronically. Passage of an object (10) will change the difference signal detected by the appts. The location of the object is determined by comparing scanned codes with those stored in memory. ADVANTAGE - Reliable detection of passage of objects or automatic vehicles.