| 摘要 |
PROBLEM TO BE SOLVED: To enable even optical disks different from each other in the thickness of a substrate to be correctly reproduced with one optical pickup by providing a polarizing hologram element transmitting one component among the component of the ordinary ray and the component of the extraordinary ray of light beams heading to an optical disk and diffracting other component. SOLUTION: When an optical disk D of a thick substraste is reproduced, light beams emitted from a semiconductor laser element 11 transmit a beam splitter 12 to be converted into parallel light rays by a collimating lens 15. The component becoming an ordinary ray in regard to the optical axis of a polarizing hologram element 16 among the light beams from the lens 15 does not receive the action of the hologram surface 16a and is made incident on an objective lens 13. These light beams are correctly focused on the signal recording surface D1 of the optical disk D. Besides, when a second optical disk of a thin substrate is reproduced, the component becoming an extraordinary ray in regard to the optical axis of the element 16 receives the action of the surface 16a and the light beams are correctly focused on the recording surface D2 of the optical disk D. |
