Focusing apparatus for projection optical system

Details Focusing apparatus for projection optical system Focusing apparatus for projection optical system

1984-11-02

1987-03-17

Wan, Gene

Radiant energy

Photocells; circuits and apparatus

Photocell controls its own optical systems

250205, G01J 136

Patent

active

046509836

ABSTRACT:
A focusing apparatus for projection optical system is provided with a projection optical system and an image-forming optical system. The projection optical system is disposed to project an image of an alignment mark formed on a photo mask or reticle onto a light-reflective substrate and also to reverse-project onto the photo mask the light image of the alignment mark projected on and reflected by the substrate. The image-forming optical system forms an overlap image from the reverse-projected reflected image and the alignment mark on the photo mask.

REFERENCES:
patent: 2493558 (1950-01-01), Thompson
patent: 3945731 (1976-03-01), Graser, Jr.

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