| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an optical pickup in which deterioration of a signal by influence of wave front aberration and astigmatism, and a good multi-level signal is obtained stably. <P>SOLUTION: This is an optical pickup performing one or more of recording, reproducing, and erasing of multi-level information for an information recording medium by level variation of strength of reflected light. The optical pickup is provided with an objective lens for converging light on the information recording medium, and has such constitution that when astigmatism of light fluxes before incidence on the objective lens of the optical pickup is assumed to W<SB>AS</SB>[λrms], and when astigmatism when parallel light fluxes having ideal wave front are transmitted through the objective lens single body and a substrate of the information recording medium is assumed to W<SB>OL</SB>[λrms], the light fluxes before incident on the objective lens having W<SB>AS</SB>and the objective lens single body having W<SB>OL</SB>and the light fluxes transmitted through the substrate of the information recording medium are constituted of an optical system satisfying a numerical formula. <P>COPYRIGHT: (C)2006,JPO&NCIPI |
