Patent ID: 7283435

Claim:
An optical disc device, comprising: converging means for converging a light beam toward an information storage medium, a focus actuator for moving the converging means substantially perpendicularly to an information layer of the information storage medium, spherical aberration changing means for changing spherical aberration occurring on a converging position of the light beam converged by the converging means, driving means for operating the spherical aberration changing means, light-receiving means for receiving light reflected from the information storage medium of the light beam, converging state detecting means for detecting a signal according to a converging state on the information layer of the information storage medium of the light beam based on a signal of the light-receiving means, focus control means for driving the focus actuator based on a signal of the converging state detecting means and performing control so that the light beam is converged on a desired position of the information layer of the information storage medium, spherical aberration detecting means for detecting a signal, based on a signal of the light-receiving means, according to an amount of spherical aberration occurring on the converging position of the light beam on the information layer of the information storage medium, spherical aberration control means for driving the driving means based on a signal of the spherical aberration detecting means and performing control so that spherical aberration is almost 0, and spherical aberration signal correcting means for amplifying a signal of the converging state detecting means by a predetermined gain and then adding the signal to a detection signal of the spherical aberration detecting means.