| 摘要 |
<P>PROBLEM TO BE SOLVED: To facilitate adjustment to a correct S/N ratio by multilayer recording and enable the device size to be reduced. <P>SOLUTION: The refractive indices of a first layer 4 and a second layer 5 are made different by appropriately condensing laser beams onto the vicinities of interfaces of an optical recording medium in which a plurality of interfaces are formed between the first layer and the second layer and forming modulation of the refractive indices not so intense as to form a blank mark and/or forming a record mark entailing changes in the shapes of the interfaces, which are thereby caused to function as reflective faces. This enables determination of the presence or absence of any mark (reproduction of recorded signals) to be accomplished by utilizing the optical path length difference (phase difference) of reflected beams arising between any mark-formed part and elsewhere. As this is phase difference detection, it is possible to avoid a tradeoff relationship between enhancement of the reproduced signal level and restraint of crosstalk in the depthwise direction, adjustment to a correct S/N ratio is made easier than by the conventional void recording system. No laser power strong enough to record any void (blank) is needed, and both the light source and the device can be reduced in size. <P>COPYRIGHT: (C)2013,JPO&INPIT |
