Magneto-optic playback apparatus including astigmatic diffracting means
US4989189A · kind A · utility
10Cited by
5References
9Claims
0Family size
Assignee
Inventors
Key dates
| Filing date | Aug 22, 1988 |
| Grant date | Jan 29, 1991 |
| Priority date | — |
| Expiry date | Aug 22, 2008 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B11/10576
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
Apparatus for playing-back information on a magneto-optic recording element includes a diffraction grating for splitting a read beam reflected from the recording element and modified by the recorded information into three beams. Two of such beams (i.e., the upper and lower first order diffracted beams) are used in a differential detection scheme to recover the recorded information, and the third beam (i.e., the zero order beam) is used to provide focus and/or tracking information.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.