Correction elements to lower light intensity around an optical axis of an optical head with a plurality of focal points
US5754512A · kind A · utility
43Cited by
5References
19Claims
0Family size
Assignee
Inventors
Key dates
| Filing date | May 29, 1996 |
| Grant date | May 19, 1998 |
| Priority date | — |
| Expiry date | May 29, 2016 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B2007/0006
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An optical head apparatus which records or reproduces signals stably on optical disks having different thicknesses. A correction hologram element or a correction filter is provided between a light source and a 2-focus lens in order to decrease optical intensity at a portion distant from the optical axis or to change the optical path length. The light which passes the correction hologram element or a correction filter is converged by the 2-focus lens as a micro-spot on an optical disk. The 2-focus lens comprises a hologram lens which diffracts a part of the light beam and an object lens.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.