OPTICAL PICKUP DEVICE-USE OPTICAL ELEMENT, COUPLING LENS AND OPTICAL PICKUP DEVICE

摘要

Since the diffraction structure of an object lens (16) has optical characteristics in which when a light-source wavelength changes to be longer, a spherical aberration at a light flux passed through such a diffraction structure is reduced, a spherical aberration can be more favorably corrected for a change in refractive index of an object lens with a change in temperature and a change in wavelength of a light source with a change in temperature. In addition, when 1.1 >= (n1 x lambda1)/(n3 x lambda3) >= 0.9 is satisfied, the quantity of light of a diffraction light flux applied to the information recording surface of a high-density DVD via the diffraction structure of the object lens (16) and the quantity of light of a diffraction light flux applied to the information recording surface of a CD are increased to effectively restrict information writing errors and reading errors.