Optical head device
US4983002A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 5, 1988 |
| Grant date | Jan 8, 1991 |
| Priority date | — |
| Expiry date | Oct 5, 2008 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B27/144
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
An optical head device which consists of a semiconductor laser for emitting a light flux, a plano-parallel optical element operable to diffract the light flux into a zero-order diffracted light beam and a plurality of diffracted light beams, a condenser lens for converging the diffracted light beams on an information bearing surface of an optical disc to form respective light spots thereon, and a photo-electric detector assembly adapted to receive, and convert into electric signals, the light beams which have been reflected from the information bearing surface of the optical disc and then passed through the optical element via the condenser lens. The plano-parallel optical element of unique construction which is employed is effective to reduce the ratio of intensity of the positive and negative first-order transmitted and diffracted light beams relative to the intensity of the zero-order transmitted and diffracted light beam to a considerably small value and also to provide a favorable tracking sensor output characteristic.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.