| 摘要 |
PURPOSE:To make a microswitch or the like unnecessary to simplify the constitution and to perform high-precision sequence control without positional adjustment, by detecting the reflected light from a recording medium of an optical beam used for recording and reproducing to obtain an accurate position signal of the recording medium. CONSTITUTION:When a recording medium 1 is moved and the end of the recording medium 1 reaches the position of an optical beam 10, the optical beam 10 is reflected by the recording medium 1, and reflected light 11 passes through a 1/4 wavelength plate 8 and is reflected by a polarizing beam splitter 7 and is made incident to a photodetector 9. At this time, the movement speed of the recording medium is switched to a low speed for recording in accordance with a timing signal issued from the photodetector 9, and a focusing lens is set to a focus position. Thereafter information is recorded by the optical beam 10. |
