Optical head device and optical information apparatus.

摘要

An optical head device includes: a light source for emitting a light beam; an objective lens for converging the light beam on an information storage medium; a hologram for receiving the light beam reflected by the information storage medium and generating diffracted light from the light beam, the hologram having such a polarization anisotropy that it diffracts light in a second polarization state more strongly than light in a first polarization state which is different from the second polarization state; and a photodetector including a plurality of photodetective sections for receiving a part of the diffracted light and outputting a photocurrent in accordance with the intensity of the part of the diffracted light. The optical head device further comprises an optical means disposed between the objective lens and the hologram for causing the polarization state of the light beam reflected by the information storage medium to be the second polarization state; and the hologram is disposed so that the distance between the hologram and the objective lens is shorter than the distance between the hologram and the photodetector.