| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a pickup lens which can be used actually for at least three kinds of optical disks. <P>SOLUTION: A plurality of circular bands exist at one side of a pickup lens, when the side in which a loop zone is formed is divided into a first region including an optical axis, a second region of a concentric circular state being adjacent to the outside of the first region, and a third region of a concentric circular state being adjacent to the outside of the second region, laser beams of wavelength λ1, λ2, λ3 of a range corresponding to the first region are condensed respectively to information recording media of which the substrate thickness are t1, t2, t3, laser beams of wavelength λ1, λ2, of a range corresponding to the second region are condensed respectively on information recording media of which the substrate thickness are t1, t2, on the other hand, the laser beam of the wavelength λ3 of a range corresponding to the second region is not condensed on information recording medium of which the substrate thickness is t3, the laser beam of wavelength λ1 of a range corresponding to the third region is condensed on information recording medium of which the substrate thickness is t1, on the other hand, the laser beams of wavelength λ2, λ3 of a range corresponding to the third region are not condensed respectively on information recording media of which the substrate thickness are t2, t3. <P>COPYRIGHT: (C)2011,JPO&INPIT |
