| 摘要 |
PURPOSE: To detect an optical information signal recorded on a disk accurately by detecting the signal by one beam system, in which a push-pull method is confused by astigmatism by using a two-piece hologram. CONSTITUTION: This pickup system has a disk 71, an objective lens 72, an actuator 73, a reflecting mirror 74, a polarized-beam divider 75, a collimator lens 76, a hologram laser device 80 composed of a semiconductor laser 77, a two-piece hologram 78 and a five-piece photodetector 79, a Wollaston prism 81, a condenser lens 82 and a two-piece photodetector 83. The collimator lens 76 is placed in front of the hologram laser device 80, and changes the laser beams of the semiconductor laser 77 diffracted by the two-piece hologram element 78 into parallel beams or projects P-polarized beams transmitted through the parallel beam divider 75 to the two-piece hologram element 78. |
