Radiant energy – Photocells; circuits and apparatus – Photocell controls its own optical systems
Patent
1993-07-14
1996-01-30
Sikes, William L.
Radiant energy
Photocells; circuits and apparatus
Photocell controls its own optical systems
250557, 356400, 356401, G01N 2186, H04N 100
Patent
active
054882303
ABSTRACT:
A position detecting apparatus comprises a double-beam producing device for producing two beams different in frequency from each other, which are guided to irradiate a diffraction grating on an object to be inspected in two predetermined directions, and a detector photoelectrically detecting through an objective optical system diffracted light produced by the diffraction grating, in which the double-beam producing device comprises a light source for supplying a beam of a single wavelength or multiple wavelengths, a beam splitting device for splitting the beam from the light source into two predetermined beams, a relay optical system for converging the two split beams at a predetermined position, and a frequency difference producing device disposed at or near a converging position by the relay optical system, for producing a predetermined frequency difference between the two split beams.
REFERENCES:
patent: 5004348 (1991-04-01), Magome
patent: 5196711 (1993-03-01), Matsugu
patent: 5204535 (1993-04-01), Mitzutani
patent: 5214489 (1993-05-01), Mitzutani
Mizutani Hideo
Ota Kazuya
Nguyen Tiep H.
Nikon Corporation
Sikes William L.
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