Patent ID: 6839142
Filing Date: 2005-01-04
Classification: G03F,H01J

Abstract:
1. A laser interferometer displacement measuring system, comprising: a laser light source; an interferometer for dividing laser light of wavelength λ emitted from said laser light source into a reference path beam and a measurement path beam to interfere said reference path beam with the measurement path beam having been reflected from a subject body; a light detector for detecting the light subjected to the interference in said interferometer, in which a variation in length of an optical path of the measurement path beam caused by a movement of the subject body is n (a natural number) times a displacement of the subject body; and means for suppressing a relative peak intensity, with respect to a baseline of a frequency spectrum, of a peak of frequency component f=Nv/λ(N is a natural number of 1 to 2n and not equal to n) of a signal indicative of the amount of received light, the signal being generated in said light detector due to a movement of said subject body at speed v.