| 摘要 |
PURPOSE:To make the size of a device small and to simplify the constitution, by changing an output of one semiconductor laser depending on the recording or reproduction of information and splitting one irradiated laser beam with a beam splitter. CONSTITUTION:A laser beam LB modulated according to an information signal Vs from a semiconductor laser 21 is split into a beam LB1 of a large optical output for information recording and a beam LB2 of a small optical output for information reproduction at a beam splitter 26, the information is recorded on an optical disc 9, the reflected light from the optical disc 9 of the beam LB2 is led to a photodetector 13 for tracking and focusing control. In reproducing the information recorded on the disc 9, since the beam splitter 26 is rotated by 180 deg. and the ratio of transmission and reflection is incerted, most of the optical output of the laser beam LB becomes the laser beam LB2 for information reproduction and is made incident to the disc 9 via the same optical path at information recording and is made incident to the detector 13 through reflection. |
