| 摘要 |
PURPOSE:To constitute a titled device so that it is not influenced by a variation of a reflection factor, which is generated before and after recording, by providing an optical system for giving an erasing spot from both sides of a recording line. CONSTITUTION:Divergent lights emitted from semiconductor lasers 12-14 becomes parallel lights (i)-(k) by collimating lens 22-24. In this case, when the semiconductor used for recording and reproduction is denoted as 12, and the semiconductor lasers used for erasion are denoted as 13 and 14, as for the parallel light (i), its direction is changed by 90 deg. by an optical synthesizer, it passes through about the center of a deflecting beam splitter 31, a lambda/4 plate 4, a mirror 39, and an objective lens 5, and forms roughly circular optical spot in the center of a recording line of a disk. On the other hand, the parallel light (j) and (k) advance in the same direction by an optical synthesizer 33, and advance in the same way as (i) after 32, but follow such an optical path as an optical spot is formed at a position shifted by a minute distance DELTAl. The light which has been reflected by the disk 1 passes through the objective lens, the mirror 39 and the lambda/4 plate 4, its direction is changed by the deflecting beam splitter 31, and thereafter, it passes through a coupling lens 6 and a cylindrical lens 62, and reaches a photodetector 7. |
