| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an optical pickup capable of recording/reproducing information to/from a different optical information recording media while making an objective lens and a coupling lens in common. <P>SOLUTION: When a coupling lens and an objective lens are made of materials satisfying an equation (3), a combination of (▵fB<SB>OBL</SB>/f<SB>OBL</SB><SP>2</SP>) and (▵fB<SB>OBL</SB>/f<SB>OBL</SB><SP>2</SP>) is decided to satisfy an equation (1), and (▵fB<SB>OBL</SB>/f<SB>OBL</SB><SP>2</SP>) is decided to satisfy an equation (2), whereby color aberrations for luminous fluxes of wavelengths λ1 and λ2 are corrected with good balance: (1) -0.016≤(▵fB<SB>OBL</SB>/f<SB>OBL</SB><SP>2</SP>)+(▵fB<SB>CPL</SB>/f<SB>CPL</SB><SP>2</SP>)≤-0.01; (2) 0.052≤▵fB<SB>OBL</SB>/f<SB>OBL</SB><SP>2</SP>≤0.1; (3A) 50≤νd<SB>OBL</SB>≤65; (3B) and 50≤νd<SB>CPL</SB>≤65. <P>COPYRIGHT: (C)2008,JPO&INPIT |
