Optical pickup apparatus and optical recording medium drive employing the same
US6144623A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jan 28, 1998 |
| Grant date | Nov 7, 2000 |
| Priority date | — |
| Expiry date | Jan 28, 2018 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B7/0912
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A transmission-type holographic optical element has a four-segment holographic surface divided into four regions of equal areas by virtual dividing lines which are perpendicular to each other. The first dividing line is at an angle with respect to the track direction of an optical disk and the second dividing line is at an angle with respect to the radial direction of the optical disk before tracking phase adjustment. The first dividing line coincides with the track direction of the optical disk and the second dividing line coincides with the radial direction of the optical disk after tracking phase adjustment. A four-segment photodetection part is divided into four photodetection parts of equal areas by a dividing line substantially parallel to the radial direction of the optical disk and a dividing line perpendicular thereto. Parts of a main beam diffracted in two regions located on first diagonal positions of the four-segment holographic surface are condensed as condensed spots on adjacent positions of the first dividing line of the four-segment photodetection part on opposite sides, and parts of the main beam diffracted in the remaining two regions located on second diagonal po…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.