Infinitesimal displacement measuring apparatus and optical pick-up unit
US5572323A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 27, 1994 |
| Grant date | Nov 5, 1996 |
| Priority date | — |
| Expiry date | Dec 27, 2014 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B11/10576
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.