Patent ID: 7200079

Claim:
An optical pickup device, comprising: a first light source to emit a first light flux having a wavelength λ 1 (380 nm<λ 1 <450 nm); a second light source to emit a second light flux having a wavelength λ 2 (600 nm<λ 2 <700 nm); and a light-converging optical system having a light-converging optical element including a diffractive structure and a correcting element arranged between the first light source and/or the second light source and the light-converging optical element; wherein the light-converging optical system converges the first light flux emitted from the first light source on an information recording surface of a first optical information recording medium through a protective layer having a thickness t 1 so that the optical pickup device conducts recording and/or reproducing information for the first information recording medium and the light-converging optical system converges the second light flux emitted from the second light source on an information recording surface of a second optical information recording medium through a protective layer having a thickness t 2 so that the optical pickup device conducts recording and/or reproducing information for the second information recording medium, wherein the light-converging optical system forms a first spot on the information recording surface of the first optical information recording medium by using N-th order diffracted light ray generated when the first light flux from the first light source passes through the diffractive structure of the light-converging optical system, and the light-converging optical system forms a second spot on the information recording surface of the second optical information recording medium by using M-th order (M≠N) diffracted light ray generated when the second light flux from the second light source passes through the diffractive structure of the light-converging optical system, and wherein on the first spot formed on the information recording surface of the first optical information recording medium, a deteriorated spherical aberration due to a wavelength change in the first light source and a deteriorated spherical aberration due to a temperature change are regulated to be within a range necessary for recording and/or reproducing of information, and on the second spot formed on the information recording surface of the second optical information recording medium, a deteriorated spherical aberration due to a wavelength change in the second light source and a deteriorated spherical aberration due to a temperature change are regulated to be within a range necessary for recording and/or reproducing of information.