Opto-electronic sensor
First Claim
1. An apparatus for measuring the distance between first and second reference points, comprising;
- in combination;
A. a frame defining said first reference point;
B. a reflective reference surface defining said second reference point, movably associated with said frame;
C. a source of light fixed in said frame for directing light toward said reference surface;
D. a first light detector, fixed in said frame immediately adjacent to said light source for detecting primarily light which is retro-reflected from said reference surface and generating a first detector signal;
E. a second light detector, fixed in said frame at a lateral distance from said light source and from said first light detector, for detecting primarily light which has been angularly reflected by said reference surface and for generating a control signal;
F. circuit means, connected to said second light detector and to said source of light for so controlling the intensity of light provided by said source of light that said control signal from said secondary control detector remains substantially constant;
whereby the magnitude of said first signal is independent of change in the coefficient of reflectance of said reflecting surface.
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Accused Products
Abstract
An instrument for giving electrical indications of the distance between two reference points includes a light source, a primary light-sensitive detector and a secondary light-sensitive control detector. Both detectors may be photodiodes. In one embodiment, the light from the source is reflected from a reference plane and is intercepted by the primary detector and by the secondary control detector. The secondary control detector is part of a control loop which adjusts the intensity of the light source in such a manner that the photo current through the secondary control detector remains constant, thus providing compensation for changes in brightness and sensitivity due to aging, soiling and other influences.
25 Citations
9 Claims
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1. An apparatus for measuring the distance between first and second reference points, comprising;
- in combination;
A. a frame defining said first reference point; B. a reflective reference surface defining said second reference point, movably associated with said frame; C. a source of light fixed in said frame for directing light toward said reference surface; D. a first light detector, fixed in said frame immediately adjacent to said light source for detecting primarily light which is retro-reflected from said reference surface and generating a first detector signal; E. a second light detector, fixed in said frame at a lateral distance from said light source and from said first light detector, for detecting primarily light which has been angularly reflected by said reference surface and for generating a control signal; F. circuit means, connected to said second light detector and to said source of light for so controlling the intensity of light provided by said source of light that said control signal from said secondary control detector remains substantially constant; whereby the magnitude of said first signal is independent of change in the coefficient of reflectance of said reflecting surface. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
- in combination;
Specification