Patent ID: 7990835

Claim:
An optical pickup apparatus, comprising: a laser light source; an objective lens for converging a laser light emitted from the laser light source onto a recording medium; an astigmatic element for introducing an astigmatism into the laser light reflected by the recording medium so as to mutually space a first focal line position occurring by convergence of the laser light in a first direction and a second focal line position occurring by convergence of the laser light in a second direction vertical to the first direction in a propagation direction of the laser light; an angle adjusting element for mutually contradicting propagation directions of luminous fluxes, out of the laser light reflected by the recording medium, within four different luminous flux regions so that the luminous fluxes within the four luminous flux regions are mutually dispersed; a photodetector for outputting a detection signal when receiving each of the dispersed luminous fluxes; and a spherical-aberration correcting unit for correcting a spherical aberration occurring in the laser light; wherein when an intersection point of two mutually crossing straight lines respectively parallel to the first direction and the second direction is matched to an optical axis of the laser light, the angle adjusting element sets the four luminous flux regions so that two of the luminous flux regions are placed in a direction in which a set of opposite angles made by the two straight lines are aligned and remaining two luminous flux regions are placed in a direction in which an alternate set of opposite angles are aligned, and the photodetector includes first sensor section for receiving the four luminous fluxes individually and second sensor section for detecting a change of an intensity distribution of the luminous fluxes by the spherical aberration.