| 摘要 |
PROBLEM TO BE SOLVED: To obtain an optical head which can perform accurate setting of the focus of an objective lens to a desired information recording layer in a plurality of information recording layers. SOLUTION: The optical head is equipped with a spherical aberration correcting means 24 to correct a spherical aberration due to difference in the transmission thickness of a light-transmitting protective layer 11C for converged light when the converged light is selectively made to irradiate a plurality of information recording layers. When the converged light by objective lenses 12, 14 is made to selectively irradiate a plurality of information recording layers, the spheric aberration correcting means 24 of the optical head is adjusted in such a manner that the corrected state of the spheric aberration by the means 24 is preliminarily optimized for the transmission thickness of the light- transmitting protective layer 11C corresponding to a specified information recording layer in a plurality of information recording layers. |
