Light curtain

摘要

A light curtain for the optical detection of shading objects in an area to be monitored, wherein the area to be monitored is repeatedly swept over by a collimated light beam of variable direction. The power of the light crossing the area is measured, shadow boundaries, position and size of a shading object are deduced by an evaluating control from the temporal profile of the measured power with knowledge of the temporal profile of the direction of the light beam. An optical detector area embodied as a planar optical waveguide is arranged along the edge of the area to be monitored, photoluminescent particles being integrated into said optical detector area and one or more photoelectric sensors being fitted to the optical detector area. Using the light curtain, shading objects can be detected with very good resolution, the light curtain can be robust and can have a low production cost.

主权项

1. A light curtain for the optical detection of shading objects in an area to be monitored, comprising a light source that emits a collimated light beam, said light beam being swept in the plane of an area to be monitored, an optical detector surface which is arranged along the edge of the area to be monitored and which can measure the power of said collimated light beam emitted by said light source, said optical detector surface being a planar optical waveguide in which photoluminescent particles are integrated and on which there is fitted at least one photoelectric sensor on a position along the longitudinal direction of said planar optical waveguide spaced apart from both end faces of said waveguide, said photoelectric sensor being capable of decoupling light from the waveguide mode, and thereby of generating an electrical signal whose intensity is a function of the power of the decoupled light a data processing system which computes from the temporal profile of the electrical signal of said optical detector surface and the temporal profile of the direction of the light beam the shadow boundaries on the optical detector surface and thus the position and size of at least one shading object in the plane of the area to be monitored.