Small gap measuring apparatus

Details Small gap measuring apparatus Small gap measuring apparatus

1985-03-01

1987-08-11

Evans, F. L.

Optics: measuring and testing

By polarized light examination

With light attenuation

250201, G01B 1100

Patent

active

046858059

ABSTRACT:
An apparatus for optically measuring the very small gap between a reference plane and a substrate parallel to the reference plane. A beam of energy converging on the reference plane is reflected by the substrate and a spot of reflected beam is formed on a detecting plane at a different position. An array of detecting elements for detecting the size of the spot on the detecting plane is adjusted in position in such a manner that the center of the spot coincides with the center of any one of the detecting elements, thereby preventing any error of the in-focus detecting position due to the deviation between the center of the spot and the center of the detecting element.

REFERENCES:
patent: 3990798 (1976-11-01), White
patent: 4079247 (1978-03-01), Bricot et al.
patent: 4315201 (1982-02-01), Suzuki et al.
patent: 4636626 (1987-01-01), Hazama et al.

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