T.V. MOTION DETECTOR WITH FALSE ALARM IMMUNITY

A motion detector which compares the video signal from a camera to a camera signal from an earlier scene and produces an alarm signal if an edge of any object has changed its position, but protects against false signals. A phase detector is used to sense movement in only the edges of objects and a vertical coincidence circuit requires object movement in several vertical video lines to prevent false signals from such small items as raindrops. Several adjacent horizontal areas must also show movement in order to activate an alarm.