| 摘要 |
An objective lens unit for an optical pickup used for recording and/or reproducing information signals from an optical disc. The objective lens unit includes a resin layer (21) having, sequentially from an object side, a first surface S1 as an aspherical surface and a second surface S2 as an aspherical surface, at least one of the first surface and the second surface including a diffractive surface, and a lens of glass (22) having the second surface S2 as an aspherical surface and a third surface S3 as an aspherical surface. The lens unit is corrected for the chromatic aberration on an image surface on the optical axis with respect to the light of a reference wavelength not larger than 420 nm within several nm of the reference wavelength, with the numerical aperture of the lens unit being not less than 0.8. This objective lens unit is able to converge the laser light close to the limit of diffraction on the image surface.
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