| 摘要 |
PURPOSE:To use one device also for reproduction by using a main beam both for recording and reproducing. CONSTITUTION:When recording, a main beam Bw from a light source 1 is projected vertically onto a medium S through the second PBS 5 the first PBS 4 a beam splitter 3. On the other hand, a sub-beam Bm is emitted from a light source 2 and reflected by the beam splitter 3 and the reflected light is projected onto the medium S. When reproducing, the main beam is put out and only the sub-beam Bm is irradiated on the medium S lowering its intensity. The beam Bm reflected by the medium S is splitted by the first PBS 4, and the first light is received by the second light converting device 8 through a quarter wavelength plate 4c and the first interference filter 4d. The first light is emitted from the third face of the first PBs 4, and nearly 100% of it, is reflected by the second PBS 5 and received by the first photoelectric converting device 7 through an interference filter 6.
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