Method and apparatus for detecting a track and focus errors in an optical head
US4841508A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Dec 28, 1987 |
| Grant date | Jun 20, 1989 |
| Priority date | — |
| Expiry date | Dec 28, 2007 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B7/0909
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A method and apparatus for detecting a track and focus errors in an optical head comprises a step of dividing light beam which is reflected from a recording medium into at least a first, second, and third light beams belonging to first, second and third cross sectional regions thereof, and means therefor. The first region is expressed in its cross sectional position by the equations, ##EQU1## the second region is expressed in its cross sectional position by the equations, ##EQU2## the third region is excluded from said first and second regions and expressed in its cross sectional position by the equations, ##EQU3## where P is a pitch of pits or pregrooves of the recording medium, .lambda. is a wavelength of the light beam, .delta. is a value which is from equal to or more than zero to equal to or less than a maximum moving distance of the object lens in a direction of a track error, d is a diameter of the light beam which is reflected, X is an axis which is parallel to a track error direction to intersect the light axis of said light beam which is reflected, and Y is an axis which is orthogonal to the X to intersect said light axis. The track error is detected in accordance with th…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.