| 摘要 |
PROBLEM TO BE SOLVED: To reproduce optical disks different from each in base material thickness by one optical pickup in a compatible manner. SOLUTION: During reproducing of a thin optical disk, no voltage is applied to a TN type liquid crystal 4. At this time, the half of a short wavelength laser beam emitted from a semiconductor laser 1 is reflected by a half mirror 2 and transformed into a parallel light by a collimator lens 3, its polarizing direction is rotated by 90 degrees by the TN type liquid crystal 4, transmitted through almost the entire part of a polarizing filter 5, made incident on an objective lens 6 and converged in a signal recording surface 7a. During reproducing of an optical disk having a standard thickness, a voltage is applied to the TN type liquid crystal 4. At this time, a laser beam emitted from the collimator lens 3 is shielded for its outer peripheral part by the polarizing filter 5, made incident on the objective lens 6 and converged in the signal recording surface 7a. |
