OPTICAL ELEMENT AND ITS MANUFACTURE, OPTICAL HEAD, AND OPTICAL RECORDING AND REPRODUCING DEVICE

摘要

PROBLEM TO BE SOLVED: To reproduce and record a signal even when birefringence is caused on an optical recording medium by using the optical element which has a low extinction ratio to ordinary light or extraordinary light below a specific value and varies in diffraction efficiency with a polarizing direction. SOLUTION: An optical element 2 used for an optical head has 70% transmissivity and 30% diffraction efficiency by having its extinction ratio (ratio of transmissivity to diffraction efficiency) decreased in the polarizing direction of light emitted by a light source 1. The element has characteristics of 100% diffraction in a polarizing direction perpendicular to the polarizing direction of light on a going way. The coherent light of a light source 1 is converged by an objective 5 and information is recorded in or reproduced from the recording layer of the optical recording medium 6. When this optical element 2 is used, optical detectors 7 and 8 are irradiated with light however large birefringence is caused on the optical recording medium 6, so the information can be recorded in and reproduced from the recording layer of the optical recording medium 6.