| 摘要 |
PURPOSE:To enable good recording and reproducing regardless of the kinds of media by setting the substrate thicknesses of the plural media having different refractive indices of the substrates according to the refractive indices. CONSTITUTION:The exit luminous flux of a semiconductor laser 1 is transmitted through a beam splitter 2 and is then imaged as a microspot 7 onto a medium surface 6 of the recording medium having a transparent protective substrate 5 by a condenser lens 3, by which the recording or reproducing of information is executed. The 1st recording medium having the substrate 5 of the thickness D1 and refractive index N1 and the 2nd recording medium having the substrate 5 of the thickness D2 and refractive index N2 are so constituted that the refractive indices N1, N2 and thicknesses D1, D2 thereof satisfy the relations N1>N2, D2<D1. The good recording and reproducing are thus executed regardless of the kinds of the media by setting the substrate thicknesses according to the refractive indices.
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