| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a coupling lens that is used in combination with an objective lens having a numerical aperture of 0.75 or above, that can effectively correct longitudinal chromatic aberration occurring in the objective lens by the axial mode hop of a bluish purple semiconductor laser light source, and that can reduce change in the spherical aberration generating by the change in the image magnification of the objective lens when the light source having variance of oscillation wavelength by manufacturing deviations is used, and also to provide an optical pickup and recording/reproducing device using this coupling lens. <P>SOLUTION: The coupling lens is arranged in the optical path between a light source 11 generating light with a wavelength of 550 nm or below and an objective lens 15 with a numerical aperture of 0.75 or above. The coupling lens has the ability to change the divergence angle of divergent light emitted from the light source and has a zonal diffraction structure. In addition, the coupling lens has a wavelength characteristic such that, if the wavelength of an incident optical flux is changed to the longer side, the spherical aberration of the outgoing optical flux is changed in the direction of insufficient correction and that, if changed to the shorter side, the spherical aberration is changed in the direction of excessive correction. <P>COPYRIGHT: (C)2004,JPO |
