| 摘要 |
<P>PROBLEM TO BE SOLVED: To prevent the occurrence of crosstalk due to stray light which raises a problem when reproducing a multilayer optical recording medium in which information has been recorded by modulating reflectance in a plurality of positions in the depth direction. <P>SOLUTION: An optical system is ordinarily configured so that light reflected from an information recording layer to be reproduced enters a condenser before a photodetector at a predetermined incident angle irrespective of the information recording layer selected as a target to be reproduced. In view of this configuration, as the condenser, a hologram element is provided which selectively condenses the light having the predetermined incident angle onto a detection surface of the photodetector. As a result, light reflected from the information recording layer to be reproduced is selectively condensed onto the photodetector, thereby preventing the other reflected light components from the optical recording medium such as stray light, from being guided to the photodetector. An additional component, such as a conventional pinhole, is not required thereby. <P>COPYRIGHT: (C)2011,JPO&INPIT |
