Patent ID: 7889620

Claim:
An optical pickup device, comprising: a light source that emits light with a wavelength λ 1 and light with a wavelength λ 2 that is longer than the wavelength λ 1 , to an optical disk from adjacent positions; an optical receiver that detects light reflected from the optical disk; and an astigmatism-generating element that generates light used for focus control in a condition that a focusing position on one of two perpendicular cross sections including an optical axis of the light reflected from the optical disk is located ahead of the optical receiver and a focusing position on the other cross section is located behind the optical receiver, wherein the astigmatism-generating element is a Fresnel mirror configured to include a plurality of reflecting mirrors; a level difference between the reflecting mirrors that are adjacent to each other is a value in a range from a depth of substantially (natural number/2) times the wavelength λ 1 to a depth of substantially (natural number/2) times the wavelength λ 2 , from a region where the light with the wavelength λ 1 is incident toward a region where the light with the wavelength λ 2 is incident; the reflected light incident on the Fresnel mirror is converging light; the Fresnel mirror is disposed to be inclined at a predetermined angle with respect to the converging light; the level difference is corrected to be deeper as a region where the reflected light is incident is at a larger incident angle and to be shallower as a region where the reflected light is incident is at a smaller incident angle; and the light with the wavelength λ 1 is incident on a side of the Fresnel mirror on which the reflected light is incident at a larger incident angle and the light with the wavelength λ 2 is incident on a side of the Fresnel mirror on which the reflected light is incident at a smaller incident angle.