The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Feb. 08, 2000
Filed:
Jan. 14, 1999
Ifunga Test Equipment B.V., , NL;
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 a second calibration value, corresponding to a situation essentially without any birefringence at all in the optical data carrier. These calibration values are used for determining the birefringence in a given spot on the optical data carrier.