| 摘要 |
<p>An optical head device includes a light blocking region disposed on a light flux of a reflected light beam resulting from reflection by a recording layer on which a blue light beam is focused, and blocks, when there are at least two recording layers on a blue light beam incident side of the recording layer on which the blue light beam is focused or on a side thereof opposite to the blue light beam incident side, reflected light beams resulting from reflection by the at least two recording layers which are incident on a region in a photodetector where the reflected light beams resulting from the reflection by the at least two recording layers interfere with each other. The light blocking region is not formed on an optical axis of the reflected light beam resulting from the reflection by the recording layer on which the blue light beam is focused.</p> |
