Automatic focusing apparatus

Details Automatic focusing apparatus Automatic focusing apparatus

2006-10-17

2006-10-17

Rutledge, D. (Department: 2851)

Photocopying

Projection printing and copying cameras

Step and repeat

C355S067000, C355S072000, C378S034000, C378S035000, C250S492200

Reexamination Certificate

active

07123345

ABSTRACT:
An automatic focusing apparatus comprises a stage holding a substrate, an objective lens disposed facing the substrate surface, an illumination optics illuminating the substrate surface with a spotted light beam from an oblique direction, a photodetector detecting reflected light from the substrate surface, a position detection circuit detecting a vertical position of the substrate surface from an electric signal obtained from the photodetector to output a position signal, a correction circuit monitoring the position signal in real time and subtracting a surplus exceeding a signal change corresponding to a surface shape change of the substrate from the position signal, when a change amount per unit time of the position signal exceeds a predetermined level and outputting a corrected position signal, and a stage control circuit controlling the vertical position of the stage based on the corrected position signal.

REFERENCES:
patent: 4698513 (1987-10-01), Tojo et al.
patent: 6639677 (2003-10-01), Ina et al.
patent: 6714281 (2004-03-01), Amano et al.
patent: 2002/0048006 (2002-04-01), Mishima
patent: 5-297262 (1993-11-01), None
patent: 6-102011 (1994-04-01), None
patent: 2003-75122 (2003-03-01), None
Ogawa et al.; “Method of Adjusting the Level of a Specimen Surface”; U.S. Appl. No. 10/666,241, filed Sep. 22, 2003.

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