Printing apparatus having an in-focus detector

Details Printing apparatus having an in-focus detector Printing apparatus having an in-focus detector

1981-03-10

1983-07-26

Wintercorn, Richard A.

Photocopying

Projection printing and copying cameras

Identifying, composing, or selecting

250557, 250575, 250578, 355 45, G03B 2752, G03B 2770

Patent

active

043951171

ABSTRACT:
A printing apparatus in which the image of a mask is projected onto a wafer by an imaging optical system and printed on the wafer. This apparatus has a detector for detecting the in-focus or lack of focus conditions of the mask image projected onto the wafer. This detector effects the detection by optically detecting the optical spacing between the mask and the wafer. The detection of such spacing is accomplished by causing a detection light to impinge on the wafer through a projection optical system and detecting the amount of displacement of the position of the reflected light in a plane optically parallel to the wafer.

REFERENCES:
patent: 3917399 (1975-11-01), Buzawa et al.

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