Emitter-detector assembly for a reflex photoelectric object detection system
First Claim
1. An object detection system comprisinga retroreflector;
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wherein the object detection system has a quality factor Q that is greater than 0.25, where the quality factor is given by the expression;
Q=(Rs Srf)/(Rd Srr Gmax)in which Rs is a signal produced by the emitter-detector assembly in response to returned light from a retroreflector, Srf is the size of the field of view in steradians of the light detection area, and Srr is the size in steradians of the light beam that is subtended by the retroreflector, Rd is the signal produced by the emitter-detector assembly in response to returned light from a 100% uniformly diffuse surface, and Gmax is a maximum reflectance of the retroreflector compared to light returned from a 100% uniformly diffuse surface.
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Accused Products
Abstract
A system for sensing the presence of nearby objects includes an emitter-detector assembly and retroreflector. The emitter-detector assembly has a light emission area from which light is transmitted toward the retroreflector. The retroreflector returns that light to a light detection area of the emitter-detector assembly which produces a signal indicating an unbroken light path. Objects passing near the assembly interrupt the light path thereby providing an indication of their presence. The light emission area and the light detection area are concentric to each other which enables the light detection area to have close proximity to the light emission area. That parameter optimizes response to light from the retroreflector, while minimizing response to light reflected by other objects.
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Citations
16 Claims
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1. 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 object detection system has a quality factor Q that is greater than 0.25, where the quality factor is given by the expression;
Q=(Rs Srf)/(Rd Srr Gmax)in which Rs is a signal produced by the emitter-detector assembly in response to returned light from a retroreflector, Srf is the size of the field of view in steradians of the light detection area, and Srr is the size in steradians of the light beam that is subtended by the retroreflector, Rd is the signal produced by the emitter-detector assembly in response to returned light from a 100% uniformly diffuse surface, and Gmax is a maximum reflectance of the retroreflector compared to light returned from a 100% uniformly diffuse surface. - View Dependent Claims (2, 3, 4, 5)
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6. An object detection system comprising:
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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. - View Dependent Claims (7, 8, 9)
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10. An emitter-detector assembly for object detection system having a retroreflector, the emitter-detector assembly comprising:
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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. - View Dependent Claims (11, 12, 13, 14, 15, 16)
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Specification