| 摘要 |
<P>PROBLEM TO BE SOLVED: To focus laser light suitable for each of a plurality of information recording surfaces provided in an information recording medium. <P>SOLUTION: An optical pickup device 1 includes a collimator lens 13 displaced on an optical axis AX from a reference position and changing a shape of the laser light. An objective lens 15 is so constituted that the size of a spot formed by the objective lens 15 is minimized in a position separated from the surface on a light source 10 side of the information recording medium 20 by a designed center thickness regulated by expression (1):L<SB>c</SB>=(L<SB>0</SB>+L<SB>n</SB>)/2 when the collimator lens 13 is positioned in the reference position, wherein L<SB>c</SB>: the designed center thickness, L<SB>0</SB>: a distance between the surface on the light source side of the information recording medium and an information recording surface positioned closest to the surface, L<SB>n</SB>: a distance between the surface on the light source side of the information recording medium and an information recording surface positioned furthest from the surface. <P>COPYRIGHT: (C)2011,JPO&INPIT |
