Device and method for measuring birefringence in an optical data carrier
US6023332A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jan 14, 1999 |
| Grant date | Feb 8, 2000 |
| Priority date | — |
| Expiry date | Jan 14, 2019 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B7/26
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A device for measuring birefringence in an optical data carrier has a laser light source with a polarization modifier, a beamsplitter, a polarizer, a photodetector, and a controller operatively connected to the photodetector. The laser light source illuminates various spots on the optical data carrier by means of a laser beam. The photodetector receives a reflected laser beam, converts it into an electric signal and supplies this signal to the controller, which determines a value for the birefringence in the illuminated spot on the optical data carrier. Furthermore, the device is provided with a transparent reference element with known birefringence properties, a mirror, and for directing the laser beam towards the reference element in a first calibration position; directly towards the mirror in a second calibration position; and towards the optical data carrier during non-calibration time. In the first calibration position the controller calculates a first calibration value from the signal received from the photodetector, said first calibration value corresponding to a given birefringence in the optical data carrier, and in the second calibration position the controller calculates…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.