Radiant energy – Photocells; circuits and apparatus – Photocell controls its own optical systems
Patent
1983-03-07
1986-03-18
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Photocell controls its own optical systems
250204, G01V 120
Patent
active
045770956
ABSTRACT:
Disclosed is an automatic focusing apparatus which comprises an objective disposed in opposition to a substrate with patterns formed thereon, a first line sensor disposed at a first focal point of the focal length of the objective, second and third line sensors which are disposed closer to and farther from the objective by a given distance with respect to second and third focal points of the focal length of the objective, first to third differential circuits for differentiating the output signals from the first to third line sensors, a detecting circuit for detecting a displacement of the substrate from a predetermined proper distance between the objective and the substrate on the basis of the output signals from the first to third differential circuits, and a correcting device for correcting the displacement on the basis of the output signal from the detecting circuit. Thus, a single optical system is used for automatically correcting focus and pattern inspection.
REFERENCES:
patent: 3967110 (1976-06-01), Rogers et al.
patent: 4220850 (1980-09-01), McEachern
patent: 4230940 (1980-10-01), Minami et al.
patent: 4333716 (1982-06-01), Sakane et al.
patent: 4341953 (1982-07-01), Sakai et al.
patent: 4349254 (1982-09-01), Jyojiki et al.
Brophy J. Jon
Nelms David C.
Tokyo Shibaura Denki Kabushiki Kaisha
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