| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an optical head device in which cross-talk is reduced during reproduction of a multi-layer optical disk. <P>SOLUTION: In the optical head device in which light emitted from a light source is reflected by an information recording layer of an optical disk and guided to a photodetector, a hologram element in which a region is divided is provided in an optical path from the optical disk to the photodetector. The region of the hologram element includes a diffraction grating, transmittance of respective regions making diffraction light is set so that a first region having high transmittance, a second region having low transmittance, and a third region having intermediate transmittance are arranged in order from the outside, and stray light which causes cross talk and which is light from a layer different from the information recording layer is reduced by the photodetector. <P>COPYRIGHT: (C)2009,JPO&INPIT |
