The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Nov. 05, 1996
Filed:
Dec. 27, 1994
Hideo Maeda, Yokohama, JP;
Hiroshi Akiyama, Yokohama, JP;
Ricoh Company, Ltd., Tokyo, JP;
Abstract
An infinitesimal displacement measuring apparatus applicable to an optical pick-up unit of an optical disk unit includes a light source for emitting a light beam, an optical system through which the light beam emitted from the light source travels to an article, a double grating unit on which the light beam reflected by the article is incident, the double grating unit having a first grating and a second grating, the first grating receiving the light beam and generating .+-.n-th order diffraction light beams, the second grating receiving the .+-.n-th order diffraction light beams from the first grating and generating .+-.m-th order diffraction light beams, a photo-detector for detecting an interference pattern formed by the .+-.m-th order diffraction light beams from the second grating of the double grating unit, and an operation circuit for carrying out an operation obtaining a displacement of the article in a direction parallel to an optical axis of the optical system based on the interference pattern detected by the photo-detector.