Radiant energy – Photocells; circuits and apparatus – Photocell controls its own optical systems
Patent
1989-09-08
1990-11-13
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Photocell controls its own optical systems
25023113, 369 58, 369116, 346108, G01J 132, G01D 534, G11B 390
Patent
active
049703803
ABSTRACT:
A technique for trimming or making a position sensor that includes a movable encoder having a track extending along a dimension of the encoder, the track having an optical property that varies with position. The sensor also includes a light source for directing an optical input beam onto the track, such that the encoder responds by producing a modulated beam having an intensity that is a function of the optical property. The intensity of the modulated beam thereby encodes the position of the encoder. The technique of the invention comprises the steps of determining the intensity of the modulated beam with the encoder at a selected position, producing a corresponding measurement signal, and comparing the measurement signal to a predetermined target value. If the difference between the measurement signal and the target value exceeds a tolerance, the optical property at the position is modified, for example using a laser beam to ablate a portion of the track. The determining, comparing, and modifying steps are repeated one or more times for each of a plurality of positions, until all differences are within tolerance. The laser beam may be directed onto the track through an access port from a position external to the encoder, such that the encoder can be trimmed after it is fully assembled.
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Messinger Michael
Nelms David C.
The Boeing Company
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