Nippon Kogaku K.k.

Kenichi Kodama

Akikazu Tanimoto

Junji Hazama

Hisao Izawa

Yoichi Hamashima

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.

Growing community of inventors

Kawasaki, Japan

Kenichi Kodama