| 摘要 |
<P>PROBLEM TO BE SOLVED: To efficiently extract signal light from a luminous flux including the signal light and stray light. <P>SOLUTION: A return luminous flux split in a -Z direction by a polarization beam splitter 54 is turned into convergent light by a condensing lens 61, and incident on a shield plate 62. Most of the signal light is transmitted through both of the shield plate 62 and a shield plate 63, condensed by a detection lens 58, and received by a photodetector 59. The stray light is shielded by a light shield part 62a of the shield plate 62 when an object recording layer is a recording layer L0, and is shielded by a light shield part 63a of the shield plate 63 when the object recording layer is a recording layer L1. Thus, because only the signal light included in the return luminous flux is received by the photodetector 59, a photoelectric conversion signal with a high S/N ratio is output from the photodetector 59. <P>COPYRIGHT: (C)2009,JPO&INPIT |
