Radiant energy – Photocells; circuits and apparatus – Photocell controls its own optical systems
Patent
1989-04-10
1990-08-28
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Photocell controls its own optical systems
356400, G01N 2186
Patent
active
049528157
ABSTRACT:
A projection exposure apparatus for projecting the image of an object on a first plane onto a second plane through a projection optical system, comprising: reference mark device provided in the vicinity of said second plane; illumination device for illuminating said reference mark device from a side opposite to said projection optical system with respect to said second plane; separation device for separating an illuminating light beam, transmitted by said reference mark device and forming the image of said reference mark device in the vicinity of said first plane through said projection optical system, into two light beams respectively passing through mutually different two areas in the pupil of said projection optical system; detection device comprising at least a pair of light receiving elements respectively receiving said light beams separated by said separation device and releasing signals corresponding to the intensities of said light beams; and position control device for detecting the position of the image plane of said projection optical system with respect to said reference mark device, based on the output signals of said detection device, and varying the optical path length between said first plane and said reference mark device.
REFERENCES:
patent: 4558949 (1985-12-01), Uehara et al.
patent: 4650983 (1987-03-01), Suwa
patent: 4780616 (1988-10-01), Nishi et al.
patent: 4794426 (1988-12-01), Nishi
patent: 4829193 (1989-05-01), Nishi
patent: 4856905 (1989-08-01), Nishi
Le Que Tan
Nelms David C.
Nikon Corporation
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