Patent Number: 7,612,888

Title: Method and apparatus for measuring heterodyne optical interference utilizing adjustable polarizing plate

Abstract: A method and an apparatus for measuring optical heterodyne interference in which a reference light and a measurement light differing in frequency is generated. The measurement light is S- or P-polarization light which is irradiated on a target through a polarization light beam splitter, and the reference light is P or S-polarization light which is reflected by a mirror. Interference of the measurement light from the target and the reference light reflected from the mirror is obtained by a light receiving element so as to measure a surface condition or detecting a surface detect on the target. A polarizing plate which is arranged before the light receiving element has an axis rotated so that a signal from the light receiving element becomes a minimum when the reference light is selectively shut off by a light shut off mechanism arranged before the polarization light beam splitter.

Inventors: Serikawa; Shigeru (Nakai, JP)

Assignee: Hitachi High-Technologies Corporation

International Classification: G01B 11/00 (20060101)

Expiration Date: 1/03/02017