| 摘要 |
PURPOSE:To generate a signal indicating the presice position of a condenser lens to an optical head by moving the condenser lens, a beam splitter and a mirror simultaneously in the tracking direction and by detecting the reflected light through the beam splitter by two-divided optical sensors. CONSTITUTION:The laser light from a semiconductor laser 2 is made incident to the beam splitter 21 through a polarized beam splitter 5 and divided into two light rays by the reflected surface 23 and the transmitted light is changed at its optical path rectangularly and condensed on a recording medium 17 through a condenser lens 7 as an optical spot 16. The reflected light from the recording medium 17 is made incident from the reflecting surface 8 of a polarized beam splitter to two-divided optical sensors 19, 20 through a half mirror 9 to detect a focal position error and a tracking position error. On the other hand, the reflected light from the beam splitter 21 is made incident to a two-divided optical sensor 18 and the output of the sensor 18 moves the condenser lens 7, the beam splitter 21 and the mirror 22 simultaneously in the tracking direction. |
