Optical disk recorders using disks coatings close to outer surfaces with optical path extending through a thick transparent substrate
US5420834A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 24, 1994 |
| Grant date | May 30, 1995 |
| Priority date | — |
| Expiry date | May 24, 2014 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B2007/0013
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A magnetooptical disk has two axially space-apart translucent recording layers. Each translucent recording layer is axially closer to an outer surface of the disk than to the other recording layer. This geometry enables closely axially disposing a magnetic field biasing means to each of the recording layers from opposite axial sides of the disk, respectively. Laser beams are axially introduced into the disk to pass through one of the translucent recording layers in a defocussed state to reach a second recording layer in a focussed state. In this manner, recording in the second layer is effected by a modulated magnetic bias field using a constant intensity laser beam. Two sets of laser beams and magnetic biasing means are provided for recording on both data in both of the recording layers.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.