| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an objective lens for an optical pickup, which is suitable for the optical pickup used to record and reproduce information in an optical recording medium increased in a recording density by narrowing a pitch of tracks, which has a small size and in which a correction of a chromatic aberration is effectively conducted and a laser beam can be collected to a diffraction limit. <P>SOLUTION: The objective lens 15 for the optical pickup has a numerical aperture of 0.8 or more and corrects the chromatic aberration of an image point on an optical axis for a light having a wavelength range of several nm or less with 420 nm or less used as a reference. The lens 15 comprises a first lens group GR1 having a composite surface S<SB>2</SB>of a refractive surface S<SB>2r</SB>and a diffraction surface S<SB>2d</SB>, and a second lens group GR2 having a positive refractive power, sequentially constituted from a light source side so that the composite surface of the first lens group is constituted by adding a diffraction surface having a positive refractive power onto an aspherical surface having a negative refractive power and a lens for constituting the second lens group is a single lens including at least one aspherical surface. <P>COPYRIGHT: (C)2003,JPO |
