Optical playback system having increased depth-of-field
US4179708A · kind A · utility
21Cited by
3References
8Claims
0Family size
Assignee
Inventors
Key dates
| Filing date | Feb 27, 1978 |
| Grant date | Dec 18, 1979 |
| Priority date | — |
| Expiry date | Feb 27, 1998 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B7/12
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
Recovery from a record of information recorded in an elongated information track comprising depressed areas alternating along the length of the track with relatively non-depressed areas, is effected by an optical playback system. The playback system employs means for illuminating a focusing lens with a light beam having a cross-section forming a closed band of light, such as an annulus, to thereby increase the depth-of-field of the resulting focused spot formed on the information track. Light detection means, responsive to light diffracted by the track provides an output signal representative of the recorded data.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.