Objective lens, optical pickup device and method for producing optical element for optical pickup device

An optical pickup apparatus, comprising:

• a first light source to emit a first light flux having a first wavelength of λ1;
• a second light source to emit a second light flux having a second wavelength of λ2(λ1<λ2);
• a light converging system including an objective lens, to converge the first light flux through a protective substrate having a thickness of t1 onto an information recording plane of a first optical information recording medium so as to conduct recording and/or reproducing information for the first optical information recording medium, and to converge the second light flux through a protective substrate having a thickness of t2 (t1<t2) onto an information recording plane of a second optical information recording medium so as to conduct recording and/or reproducing information for the second optical information recording medium;
• the objective lens comprising:
• an optical element provided in an optical path;
• and
• a diffractive optical surface formed on at least one surface of the optical element;
• wherein the first tight flux is converged as a first number diffraction order diffracted-ray other than the zero-th order diffracted-ray onto the information recording plane of the first optical information recording medium having the protective substrate by the diffractive optical surface and the second light flux 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 the protective substrate by the diffractive optical surface;
• wherein the second number diffraction order is a lower number diffraction order than the first number diffraction order;
• and
• wherein the diffractive optical surface has a diffractive characteristic to make a second focal length with regard to the second light flux to be larger than a first focal length with regard to the first light flux.