Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1989-09-20
1991-06-25
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
250237G, G01D 534
Patent
active
050269852
ABSTRACT:
In the reference-position detection method and apparatus for detecting a reference position of a scale, first and second patterns are disposed on the scale so that respective detection timings shift inversely to each other in response to a deviation in attitude of the scale. The first and second patterns are detected with timings different from each other by corresponding first and second sensors, and the reference position of the scale is determined according to outputs of respective sensors. Hence, even if the attitude of the scale changes from a predetermined attitude due to an inclination of the scale or a deviation in position of the scale, it is possible to exactly detect the reference position of the scale. Accordingly, it becomes also possible to increase the performance of a displacement measuring apparatus.
REFERENCES:
patent: 3728551 (1973-04-01), Culver et al.
patent: 4064435 (1977-12-01), Stebbins
patent: 4145608 (1979-03-01), Shirasaki et al.
patent: 4477189 (1984-10-01), Ernst
patent: 4868385 (1989-09-01), Nishimura
Navy Technical Disclosure Bulletin, vol. 3, No. 7, published Jul., 1978, Arnolds Jansons, pp. 51-54.
Ishii Satoshi
Ishizuka Koh
Nishimura Tetsuharu
Tsukiji Masaaki
Canon Kabushiki Kaisha
Le Que Tan
Nelms David C.
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