Optical pick-up device for both focus and error tracking detection
US4687916A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jul 12, 1985 |
| Grant date | Aug 18, 1987 |
| Priority date | — |
| Expiry date | Jul 12, 2005 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B7/1381
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An optical pick-up device suitable for use in an optical disk memory system includes a semiconductor laser unit which emits a laser light beam which, in turn, passes through a beam splitter, a quarter-wave plate, and an objective lens to impinge on an optical disc thereby forming a light spot thereon. The light is then reflected from the disc and this reflected light passes through the objective lens and the quarter-wave plate and its direction of advancement is altered by the beam splitter to move into a convergent lens. Then, as the reflected light further advances, it is partly blocked by a tracking error detecting sensor and the remaining non-blocked portion of the reflected light impinges upon a focusing error detecting sensor. The objective and convergent lenses have f.sub.0 and f.sub.1 as their focal distances, respectively, and, preferably, ratio f.sub.0 /f.sub.1 is set equal to or larger than approximately 10.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.