Coma correction in optical head with astigmatism for focusing error detection
US4709139A · kind A · utility
15Cited by
4References
5Claims
0Family size
Assignee
Inventors
Key dates
| Filing date | Apr 3, 1986 |
| Grant date | Nov 24, 1987 |
| Priority date | — |
| Expiry date | Apr 3, 2006 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B7/1381
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
In an optical head having a plate-like half mirror functioning both as a beam splitter and for producing an astigmatism usable in detecting a focusing error, an optical element is provided for correcting a coma introduced by the half-mirror. Such optical element for correcting coma desirably includes a plate-like element inclined oppositely to the plate-like half mirror in respect to an optical axis of the head.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.