Patent ID: 8427922

Claim:
An optical pickup device, comprising: a laser light source; an objective lens for converging laser light emitted from the laser light source on a recording medium; an astigmatism element for imparting astigmatism to the laser light reflected on the recording medium to distance a position of a first focal line apart from a position of a second focal line in a propagating direction of the laser light, the first focal line being defined by convergence of the laser light in a first direction, the second focal line being defined by convergence of the laser light in a second direction perpendicular to the first direction; an angular adjuster for changing propagating directions of light fluxes in four division areas one from the other, the four division areas being obtained by dividing a light flux area of the laser light reflected on the recording medium by a first straight line and a second straight line respectively parallel to the first direction and the second direction, and perpendicularly intersecting with each other; a photodetector including eight sensors individually receiving eight light fluxes obtained by dividing the light fluxes in the four division areas by a third straight line and a fourth straight line respectively rotated with respect to the first straight line and the second straight line by 45 degrees; a computing circuit for generating a tracking error signal based on signals from the sensors; and a gain adjusting circuit for adjusting a gain of the signal from the sensor in such a manner that a direct-current component of the tracking error signal resulting from positional displacements of the sensors is cancelled, based on the positional displacements of the sensors in a parallel direction to a light receiving surface of the photodetector.