Patent ID: 8208360

Claim:
An optical pickup device, comprising: a light source configured to emit light toward an optical disk; an objective lens configured to converge the outgoing light from the light source on the optical disk; an optical receiver configured to reflected light, the reflected light being the outgoing light passed through the objective lens after the outgoing light is reflected on the optical disk; and an astigmatism generation element interposed between the objective lens and the optical receiver, the astigmatism generation element generating light for focus control purpose that produces focal points in front of and behind the optical receiver within two mutually orthogonal cross-sectional planes including an optical axis of the reflected light; wherein the astigmatism generation element is a Fresnel mirror that has a plurality of orbicular zones and steps connecting adjacent orbicular zones to each other and that takes the orbicular zones as reflecting mirrors; and wherein a depth of the steps is set to substantially one-half of a wavelength of the light, and a portion of the Fresnel mirror at a center of the Fresnel mirror is thicker than each of the steps.