LIGHT CURTAIN AND AN INPUT APPARATUS BASED THEREON FOR A DATA PROCESSING SYSTEM

摘要

A light curtain having a light source which emits a light beam which propagates in an area to be monitored by the light curtain and then strikes an optical detector surface. The area to be monitored is arranged in the vicinity of a translucent disc and is oriented parallel to the latter. The light source and detector surface are arranged on that side of the disc which faces away from the area to be monitored. The path of the light beam from the light source to the detector surface runs twice through the plane of the disc and via two mirrors arranged on the edge of the area to be monitored.