Method and device for detecting focal point
US4636625A · kind A · utility
6Cited by
1References
3Claims
0Family size
Assignee
Inventors
Key dates
| Filing date | Sep 5, 1985 |
| Grant date | Jan 13, 1987 |
| Priority date | — |
| Expiry date | Sep 5, 2005 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B7/0945
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
Less than half of a laser beam reflected from an optical information storage medium through an objective lens is detected by a detector having two light detecting areas. The sum of output signals from the light detecting areas of the detector is employed to detect when the objective lenas enters a focusing range. The difference between the output signals is employed to detect when the laser beam is focused on the optical information storage medium.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.