Optical information storage medium reproduction apparatus and control method of the same

Abstract

In an optical information storage medium reproduction apparatus ( 10 ) for reproducing an optical information storage medium including a plurality of information recording layers each including a recording mark having a length shorter than an optical system resolution limit, reproduction laser power for reading an information recording layer closest to a reproduction-laser-incident surface of the optical information storage medium is set to be lower than reproduction laser power for reading an information recording layer farthest from the reproduction-laser-incident surface but not lower than minimum reproduction laser power that satisfies a reproduction signal characteristic that the optical information storage medium reproduction apparatus ( 10 ) requires. With the arrangement, it is possible to prevent that the information recording layer closest to the reproduction-laser-incident surface is irradiated wrongly with reproduction laser having high reproduction laser power, thereby making it possible to obtain successful reproduction quality. That is, it is possible to realize the optical information storage medium reproduction apparatus ( 10 ) that can set optimum reproduction laser power and perform stable super resolution reproduction.

1 . An optical information storage medium reproduction apparatus for reproducing an optical information storage medium in which a plurality of information recording layers are laminated, each of the plurality of information recording layers including a recording mark having a length shorter than an optical system resolution limit, wherein:
 the optical information storage medium reproduction apparatus reads an information recording layer closest to a reproduction-laser-incident surface of the optical information storage medium, with reproduction laser power that is set to be lower than reproduction laser power for reading an information recording layer farthest from the reproduction-laser-incident surface but not lower than minimum reproduction laser power that satisfies a reproduction signal characteristic that the optical information storage medium reproduction apparatus requires.   
     
     
         2 . An optical information storage medium reproduction apparatus for reproducing an optical information storage medium in which a plurality of information recording layers are laminated, each of the plurality of information recording layers including a recording mark having a length not longer than 120 nm, the optical information storage medium reproduction apparatus comprising:
 an optical system including a laser light source capable of irradiating laser light having a wavelength of not less than 400 nm but not more than 410 nm and an objective lens having a numerical aperture of not less than 0.83 but not more than 0.87, wherein:   the optical information storage medium reproduction apparatus reads an information recording layer closest to a reproduction-laser-incident surface of the optical information storage medium, with reproduction laser power that is set to be lower than reproduction laser power for reading an information recording layer farthest from the reproduction-laser-incident surface but not lower than minimum reproduction laser power that satisfies a reproduction signal characteristic that the optical information storage medium reproduction apparatus requires.   
     
     
         3 . The optical information recording medium reproduction apparatus as set forth in  claim 1 , wherein:
 the reproduction laser power with which the optical information recording medium reproduction apparatus reads the information recording layer closest to the reproduction-laser-incident surface is set to be not higher than 0.95 times the reproduction laser power for reading the information recording layer farthest from the reproduction-laser incident surface but not lower than 1.05 times the minimum reproduction laser power that satisfies the reproduction signal characteristic that the optical information storage medium reproduction apparatus requires at the time of reading the information recording layer closest to the reproduction-laser-incident surface.   
     
     
         4 . The optical information storage medium reproduction apparatus as set forth in  claim 1 , wherein:
 at the time of focus movement from an information recording layer onto another information recording layer, the optical information storage medium reproduction apparatus moves the focus from the information recording layer onto the another information recording layer with reproduction laser power being maintained to be lower than the reproduction laser power for reading the information recording layer farthest from the reproduction-laser-incident surface.   
     
     
         5 . The optical information storage medium reproduction apparatus as set forth in  claim 4 , wherein:
 the optical information storage medium reproduction apparatus moves the focus from the information recording layer onto the another information recording layer with reproduction laser power for reading one of the information recording layers that is closer to the reproduction-laser-incident surface.   
     
     
         6 . The optical information storage medium reproduction apparatus as set forth in  claim 1 , wherein:
 in a case where the optical information storage medium includes 2 information recording layers, the optical information storage medium reproduction apparatus reproduces the optical information storage medium in the order from one of the 2 information recording layers that is closer to the reproduction-laser-incident surface than the other one of the 2 information recording layers.   
     
     
         7 . A control method for controlling an optical information storage medium reproduction apparatus for reproducing an optical information storage medium in which a plurality of information recording layers are laminated, each of the plurality of information recording layers including a recording mark having a length shorter than an optical system resolution limit, said control method comprising:
 setting, at the time of reading an information recording layer closest to a reproduction-laser-incident surface of the optical information storage medium, reproduction laser power to be lower than reproduction laser power for reading an information recording layer farthest from the reproduction-laser-incident surface but not lower than minimum reproduction laser power that satisfies a reproduction signal characteristic that the optical information storage medium reproduction apparatus requires.   
     
     
         8 . The optical information recording medium reproduction apparatus as set forth in  claim 2 , wherein:
 the reproduction laser power with which the optical information recording medium reproduction apparatus reads the information recording layer closest to the reproduction-laser-incident surface is set to be not higher than 0.95 times the reproduction laser power for reading the information recording layer farthest from the reproduction-laser incident surface but not lower than 1.05 times the minimum reproduction laser power that satisfies the reproduction signal characteristic that the optical information storage medium reproduction apparatus requires at the time of reading the information recording layer closest to the reproduction-laser-incident surface.   
     
     
         9 . The optical information storage medium reproduction apparatus as set forth in  claim 2 , wherein:
 at the time of focus movement from an information recording layer onto another information recording layer, the optical information storage medium reproduction apparatus moves the focus from the information recording layer onto the another information recording layer with reproduction laser power being maintained to be lower than the reproduction laser power for reading the information recording layer farthest from the reproduction-laser-incident surface.   
     
     
         10 . The optical information storage medium reproduction apparatus as set forth in  claim 9 , wherein:
 the optical information storage medium reproduction apparatus moves the focus from the information recording layer onto the another information recording layer with reproduction laser power for reading one of the information recording layers that is closer to the reproduction-laser-incident surface.   
     
     
         11 . The optical information storage medium reproduction apparatus as set forth in  claim 2 , wherein:
 in a case where the optical information storage medium includes two information recording layers, the optical information storage medium reproduction apparatus reproduces the optical information storage medium in the order from one of the two information recording layers that is closer to the reproduction-laser-incident surface than the other one of the two information recording layers.