| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a pickup lens that can be practically used for at least three kinds of optical disks. <P>SOLUTION: A plurality of orbicular zones are present on one surface of a pickup lens. When the surface formed with the orbicular zones is divided into a first area including an optical axis, a concentric second area adjacent to the outside of the first area, and a concentric third area adjacent to the outside of the second area, laser beams of wavelengths λ1, λ2 and λ3 in a range corresponding to the first area are condensed respectively to information recording media whose substrate thicknesses are t1, t2 and t3. While the laser beams of wavelengths λ1 and λ2 in a range corresponding to the second area are condensed respectively to the information recording media whose substrate thicknesses are t1 and t2, the laser beam of a wavelength λ3 in the range corresponding to the second area is not condensed to the information recording medium whose substrate thickness is t3, and while the laser beam of a wavelength λ1 in a range corresponding to the third area is condensed to the information recording medium whose substrate thickness is t1, the laser beams of wavelengths λ2 and λ3 in the range corresponding to the third area are not condensed to the information recording media whose substrate thicknesses are t2 and t3. <P>COPYRIGHT: (C)2013,JPO&INPIT |
