| 摘要 |
An objective lens for use in an optical pickup apparatus has a diffractive optical surface. A first light flux having a first wavelength of »1 is converged as a first number diffraction order diffracted-ray other than the zero-th order diffracted-ray onto an information recording plane of the first optical information recording medium having a thinner protective substrate t1 by the diffractive optical surface and a second light flux having a second wavelength of »2 (»1 < »2) is converged as a second number diffraction order diffracted-ray other than the zero-th order diffracted-ray onto the information recording plane of the second optical information recording medium having a thicker protective substrate t2 (t1 < t2) by the diffractive optical surface. The second number diffraction order is different from the first number diffraction order. |
