Patent ID: 7599276

Claim:
An optical head device comprising: a light source; an objective lens for converging an emitted light emitted from the light source on an optical recording medium; a photo-detector for receiving a reflected light reflected by the optical recording medium; an optical separator element for separating the emitted light and the reflected light; and a birefringence correcting element for correcting an influence of birefringence of a protection layer of the optical recording medium on the emitted light or reflected light, wherein the birefringence correcting element has an optic axis whose direction in a plane of the birefringence correcting element changes as a function of an intra-plane position thereof on the birefringence correcting element and a phase difference between a polarized light component polarized in a direction parallel to the optic axis and another polarized light component polarized in a direction vertical to the optic axis changes as a function of intra-plane positions thereof on the birefringence correcting element.