Radiant energy – Photocells; circuits and apparatus – Photocell controls its own optical systems
Patent
1983-12-20
1986-02-11
Westin, Edward P.
Radiant energy
Photocells; circuits and apparatus
Photocell controls its own optical systems
250204, 354 4, G01C 308
Patent
active
045700591
ABSTRACT:
An automatic focus control device for adjusting the height of a lens above a surface of a workpiece used in an exposure apparatus for exposing the sample with a light beam including a first light emitting device for emitting a first light ray to a sample; a second light emitting device for emitting a second light ray to the sample. First and second light detecting devices for detect the second and first light rays reflected by a surface of the sample, respectively. The first and second light detecting device have a plurality of light detecting elements. A discriminating device discriminating between an inclination of the sample and a variation of the height of the lens above the surface of the sample on the basis of an output of the first and second light detecting devices. The first light emitting device and the first light detecting device are symmetrically located with respect to the second light emitting device and the second light detecting device in relation to a center axis of a light beam for exposing the sample.
REFERENCES:
patent: 4233502 (1980-11-01), Bouwhuis et al.
patent: 4257705 (1981-03-01), Hosoe et al.
Fujitsu Limited
Westin Edward P.
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