Device for optically scanning information tracks on a plane using two subbeams
US6512732B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Dec 12, 1996 |
| Grant date | Jan 28, 2003 |
| Priority date | — |
| Expiry date | Dec 12, 2016 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B7/0943
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A device for optically scanning an information plane having tracks. Radiation is supplied by a radiation source focused on the information plane by an objective system. The beam reflected by the information plane is incident on a dividing element, for example a grating which divides the beam into two halves along a dividing line. Two sub-gratings at both sides of the dividing line each form a detection beam from one half of the beam, which detection beams are detected each by a detector. A focus error signal is generated from the detector signals by forming a difference signal of the two detector signals and dividing this difference signal by the sum signal of the two detector signals. The focus error signal is relatively insensitive to the position accuracy of the detectors with respect to the detection beams.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.