| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an optical element for an optical pickup device, capable of properly recording and/or reproducing information in a high density DVD, a conventional DVD, and all CD's while securing a sufficient spot light amount, a coupling lens, and the optical pickup device. <P>SOLUTION: This optical element has optical characteristics which reduce a spherical aberration more in a luminous flux passed through a diffraction structure when the diffraction structure of an objective lens 16 is changed to make a light source wavelength longer. Thus, the spherical aberration is corrected better with respect to the refraction index change of the objective lens accompanying a temperature change, and the wavelength fluctuation of a light source accompanying the temperature change. By satisfying 1.1≥(n1×λ1)/(n3×λ3)≥0.9, the amount of a diffraction luminous flux applied to the information recording surface of a high density DVD and the amount of a diffraction luminous flux applied to the information recording surface of a CD via the diffraction structure of the objective lens 16 are increased. Thus, the occurrence of information writing or reading errors is effectively suppressed. <P>COPYRIGHT: (C)2008,JPO&INPIT |
