| 摘要 |
PROBLEM TO BE SOLVED: To stably reproduce two kinds of optical disk different in thickness by providing a light shielding means and a phase shifter giving a part of laser light a phase difference arranged between a light source and an objective lens. SOLUTION: When a high density optical disk 13 is reproduced, a liquid crystal optical rotator 6 and a liquid crystal drive circuit 7 optically rotates luminous flux 4 so that no phase difference occurs in the luminous flux 9 by the phase shifter 10 and the luminous flux 9 becomes the polarization direction so as to transmit through a polarizing plate (luminous flux 25) as it is. On the other hand, when a CD 14 in thickness of 1.2mm is reproduced, the liquid crystal optical rotator 6 and the liquid crystal drive circuit 7 optically rotates the luminous flux 4 so that the phase difference occurs in the luminous flux 9 by the phase shifter 10, and the luminous flux 26 of the central part of the luminous flux 9 transmits through the polarizing plate 11, and the luminous flux of the peripheral part becomes the polarization direction so as to be light shielded by the polarizing plate 11. Then, only the luminous flux of the center part is made incident on the objective lens 12. |
