| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an objective lens for optical disk compatible with multiple kinds of optical disks having different protective layer thicknesses and is suitable for recording and reproducing of information for the optical disk capable of information recording having relatively thick protective layer in particular. <P>SOLUTION: The objective lens for optical disk has compatibility with the optical disk of a plurality of standards. One surface of the lens has inside region and outside region. The outside region has such a zone as to be within a prescribed range where the phase of transmitted luminous flux of a first wavelength becomes an opposite phase substantially to the phase of luminous flux of the first wavelength transmitted by the inside region and satisfies the following relation: 1.0<sinθ/NA<SB>ref</SB><1.1 and the effective numerical aperture of luminous flux of the first wavelength is approximately equal to the numerical aperture NA<SB>ref</SB>. Therein, θ is a convergent angle after objective lens transmission of light which is made incident to the most peripheral inside region among luminous flux of the first wavelength and NA<SB>ref</SB>is a numerical aperture necessary for recording and reproducing of information with respect to the first optical disk. <P>COPYRIGHT: (C)2004,JPO&NCIPI |
