| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an optical unit used for an optical information recording and reproducing device, which overwrites information when information is recorded or reproduced in a three-dimensional manner to/from an optical recording medium. <P>SOLUTION: A diffraction lens 19 generates from light emitted from a laser 16, first light and second light which are coaxial and have different image point positions. An objective lens 22 focuses the first light directed toward the side of a reflection layer 28 within a recording layer 26 and the second light passing through the recording layer 26 to be reflected by the reflection layer 28 and directed toward the side opposite to the reflection layer 28 within the recording layer 26, at the same position. An active wavelength plate 20 switches the polarization state of the first light and the second light near the focus point between clockwise circular polarization and counterclockwise circular polarization. <P>COPYRIGHT: (C)2011,JPO&INPIT |
