Abstract: Apparatus and method for detection of leading and trailing edges of objects moving along a defined path. A light radiation source directs a light beam toward a beamspot on the path. Light reflected from the beamspot is received by two light sensors. An edge of an object moving along the defined path substantially blocks the light from being received by one light sensor. Circuitry is provided for distinguishing the difference in reflected light received at each light sensor and determining whether the leading edge or trailing edge of the object is blocking the reflected light. Length of detections (leading and trailing edges) and time interval between the detections of the leading and trailing edge are processed to provide information about the object such as height of the leading and trailing edges of the object and length of the object. Further processing of leading and trailing edge detections can detect overlapped objects having relatively uniform surfaces.

Abstract: Apparatus and method for detection of leading and trailing edges of objects moving along a defined path. A light radiation source directs a light beam toward a beamspot on the path. Light reflected from the beamspot is received by two light sensors. An edge of an object moving along the defined path substantially blocks the light from being received by one light sensor. Circuitry is provided for distinguishing the difference in reflected light received at each light sensor and determining whether the leading edge or trailing edge of the object is blocking the reflected light. Length of detections (leading and trailing edges) and time interval between the detections of the leading and trailing edge are processed to provide information about the object such as height of the leading and trailing edges of the object and length of the object. Further processing of leading and trailing edge detections can detect overlapped objects having relatively uniform surfaces.