Patent Number: 6,166,817

Title: Optical displacement measurement system for detecting the relative movement of a machine part

Abstract: An optical displacement measurement system can detect a position of an object with an enhanced degree of resolution by providing, a coherent beam La is focussed on the lattice plane of a diffraction grating 1 by a first focussing element 4 and, at the same time, a first pair of diffracted beam Lb1, Lb2 are collimated and made to irradiate a reflection optical system 3 perpendicularly by a second focussing element 5. Thus, if the optical axis of the first diffracted beam Lb1 is displaced, the first diffracted beam Lb1 follows the same optical path and focussed on the lattice plane of the diffraction grating at the same spot when reflected by the reflection optical system so that the optical axis of the second diffracted beam Lb2 produced from the first diffracted beam Lb1 as the latter is diffracted will never be displaced. Therefore, the second diffracted beam that is free from any displacement of the optical axis is made to interfere with another second diffracted beam to detect the phase difference thereof and determine the displaced position of the diffraction grating 1.

Inventors: Kuroda; Akihiro (Kanagawa, JP)

Assignee: Sony Precision Technology Inc.

International Classification: G01D 5/38 (20060101); G01D 5/26 (20060101); G01B 011/02 ()

Expiration Date: 12/26/2017