| 摘要 |
Between a semiconductor laser and a polarizing beam splitter, a polarization direction control element, including a liquid crystal polymer layer divided into a plurality of concentric circle regions having different optical axis directions, is provided. A voltage is applied to the liquid crystal polymer layer at the time of recording. Since the polarization direction control element acts as a full wavelength plate for incident light, the light exiting the polarizing beam splitter has an intensity distribution identical to that of the incident light and the rim strength in an objective lens lowers. No voltage is applied to the liquid crystal polymer layer at the time of reproduction. Since the polarization direction control element operates as a half wavelength plate for rotating the polarization direction of the incident light more toward the central portion, the light exiting the polarizing beam splitter has an intensity becoming lower toward the central portion as compared with the incident light, and the rim strength in an objective lens increases. |
