Patent ID: 8446809

Claim:
An optical pickup device for irradiating laser light onto a recording medium having a plurality of recording layers, comprising: a light source for emitting laser light; an objective lens for converging the laser light on the recording medium; an astigmatism portion for receiving the laser light reflected on the recording medium, and provided with four or more lens areas formed around an optical axis of the laser light to impart astigmatism to the laser light individually with respect to each of the lens areas; a light flux separating portion for making propagating directions of a light flux of the laser light to be entered into each of the lens areas different from each other to separate the light fluxes from each other; and a photodetector for receiving the separated light fluxes to output a detection signal, wherein the lens areas are configured in such a manner that the light flux in each one of the lens areas is converged in a direction parallel to a first boundary out of the first boundary and a second boundary defined between the one lens area, and the other two lens areas adjacent to the one lens area around the optical axis to form a focal line at a position of a first focal length, and that the light flux is converged in a direction perpendicular to the first boundary to form a focal line at a position of a second focal length different from the first focal length, and the first boundaries of the respective lens areas are defined at such positions that the first boundaries are perpendicular to each other.