Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1984-03-20
1986-12-16
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
250231SE, H01J 314
Patent
active
046298860
ABSTRACT:
An optical scale reader comprises a light source for radiating a beam of coherent light on a reflective scale, a half mirror for mixing light beams from the light source which are reflected and diffracted by the scale for interference with each other, an optical system for causing the interfering light beams leaving the half mirror on its opposite sides to be 90.degree. out of phase with each other so that the light beams will fall on the half mirror at a particular angle of incidence, photodetectors for detecting the interfering light beams, respectively, which have left the half mirror, and a signal processor for processing first and second electric signals which are supplied from the photodetectors and 90.degree. out of phase with each other to generate a signal indicative of the distance which the scale has moved. There is also disclosed a position control device incorporating the optical scale reader.
REFERENCES:
patent: 3756723 (1973-09-01), Hock
patent: 3796498 (1974-03-01), Post
patent: 3891321 (1975-06-01), Hock
patent: 3904295 (1975-09-01), Hock et al.
patent: 4334779 (1982-06-01), Domey et al.
patent: 4358201 (1982-11-01), Makosch
Akiyama Koji
Iwaoka Hideto
Kojima Moonray
Nelms David C.
Yokogawa Hokushin Electric Corporation
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