Emitter-detector assembly for a reflex photoelectric object detection system

An object detection system comprising:

• a retroreflector;
• and
• a emitter-detector assembly having a light emission area from which a light beam is emitted toward the retroreflector and having a light detection area in which light impinging thereon from the retroreflector produces an electrical signal, wherein the light emission area and the light detection area are concentric with one extending around the other;
• wherein the light detection area is substantially equal in size to the light emission area and wherein the object detection system has a quality factor 0 that is greater than 0.25, where the quality factor is given by the expression:
• Q=∫∫[Gr(x)dS dD]/(As Ad)
• where As is the size of the light emission area, Ad is the size of the light detection area, dS is an area element of the light emitting aperture, dD is an area element of the photodetector aperture, x is the separation between the source aperture and detector aperture area elements, and Gr(x) is the relative gain of the retroreflector at the displacement x between source and detector area elements compared to the maximum attainable return.

An emitter-detector assembly for object detection system having a retroreflector, the emitter-detector assembly comprising:

• a light emission section comprising a light emitter assembly from which a light beam emanates in a first path;
• and
• a light detection section comprising a photodetector which produces an electrical signal in response to light impinging thereon from the retroreflector;
• wherein the light emitter assembly is concentric with the light detection section, and comprises a plurality of light emitters located at different angles axially around the photodetector.