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:
Apr. 22, 2003
Filed:
Jun. 13, 2000
Kabushiki Kaisha Sankyo Seiki Seisakusho, Nagano, JP;
Abstract
A phase difference plate ( ) converts states of polarization of emergent light form a laser light source ( ) and return light form an optical recording medium ( ). A diffractive element ( ) separates the return light from an optical axis leading from the laser light source ( ) to the optical recording medium ( ), and guides the return light to a photodetector ( ) 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 ( ) is arranged so as to be oriented in the radial direction of the optical recording medium ( ) (in the direction of birefringence of the optical recording medium). The azimuth and the amount of phase of the phase difference plate ( ) are set so that a peak of a signal in tensity detected by the photodetector ( ) 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 ( ) is changed.