Optical pickup device
US6552317B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Jun 13, 2000 |
| Grant date | Apr 22, 2003 |
| Priority date | — |
| Expiry date | Jul 23, 2020 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B7/1365
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A phase difference plate (12) converts states of polarization of emergent light form a laser light source (13) and return light form an optical recording medium (5). A diffractive element (21) separates the return light from an optical axis leading from the laser light source (13) to the optical recording medium (5), and guides the return light to a photodetector (14) on the basis of a difference between the states of polarization of the emergent light and the return light. The polarization direction of emergent light from the laser light source (13) is arranged so as to be oriented in the radial direction of the optical recording medium (5) (in the direction of birefringence of the optical recording medium). The azimuth and the amount of phase of the phase difference plate (12) are set so that a peak of a signal in tensity detected by the photodetector (14) appears while an amount of birefringence of the optical recording medium changes from 0 to a quarter wavelength of the laser light when the amount of birefringence of the optical recording medium (5) is changed.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.