Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1983-09-19
1987-03-31
Westin, Edward P.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
250237G, 340347P, G01D 534
Patent
active
046545247
ABSTRACT:
A method and apparatus for measuring a minute linear or rotational displacement of a linearly movable or rotary member relative to a stationary member, wherein the stationary member is provided with a plurality of photodetectors arranged at regular linear or angular intervals along a predetermined linear or circular length D, and the linearly movable or rotary member is provided with a plurality of narrow slots arranged at regular linear or angular intervals along the same linear or circular length as the above-mentioned linear or circular length. The length D on the stationary member is equally divided by n, which is a positive integer, and each of the photodetectors is positioned at one of the dividing points or positions. The length D on the linearly movable or rotary member is equally divided by n.+-.m, where m is a positive number sufficiently smaller than n, and each of the slots is positioned at one of the dividing points or positions. The two members face each other across a small gap and are so arranged that when illuminated through the slots, the photodetectors receive successively different amounts of light and consequently produce outputs of successively different levels. When plotted against the successive positions of the photodetectors in the linear or circular arrangement, the outputs form a wave, the phase of which changes greatly upon minute linear or rotational displacement of the two members with the slots and photodetectors thereon relative to each other. The linear or rotational displacement is measured by measuring the phase change, and a very high degree of accuracy of measurement is attained by statistically processing the outputs of the photodetectors. The slots and the photodetectors may be replaced by any other suitable elements which interact with each other to produce a variable amount of information.
REFERENCES:
patent: 4250380 (1981-02-01), Iyeta
patent: 4342909 (1982-08-01), Accattino
patent: 4496835 (1985-01-01), Boella et al.
patent: 4507647 (1985-03-01), Minami et al.
patent: 4529964 (1985-07-01), Minami et al.
Shimadzu Corporation
Westin Edward P.
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