Moving conveyor control point for a supermarket checkout has a photoelectric barrier to monitor the conveyor crosswise and to switch it off as a purchase item breaks the barrier.

摘要

Laser beams (2) monitor a moving conveyor (1) almost flush with its surface. At the start of the conveyor there is a wide mirror surface (3) only a couple of millimeters high. A light transmitter emits a beam of light that hits one of the mirror surfaces. An infrared luminous diode or laser diode can be used to emit this light. The beam is reflect as a zigzag many times over the conveyor.