Patent ID: 7843788

Claim:
An optical recording medium driving device, comprising: head means for irradiating a laser light onto an optical recording medium and detecting a reflected light from the optical recording medium to read out a signal, the head means having a focus servo mechanism and a spherical aberration correction mechanism for the laser light; evaluation signal generating means for generating, based on the reflected light detected by the head means, an evaluation signal that serves as an indicator of a quality of the readout signal; focus servo means for driving the focus servo mechanism according to a focus error signal generated based on the reflected light detected by the head means to perform a focus servo operation; spherical aberration correction means for driving the spherical aberration correction mechanism according to a spherical aberration correction value to perform a spherical aberration correction operation; focus bias means for adding focus bias to a focus loop including the focus servo means; and control means for setting a first adjustment value based on the evaluation signal obtained in response to the focus servo means altering the spherical aberration correction value, and based on a limit value set for the spherical aberration correction value value, wherein the control means obtains values of the evaluation signal in response to sequentially altering the spherical aberration correction value by a predetermined alteration value, determines, based on the obtained results, whether or not an optimum evaluation signal value exists within a range defined by a plurality of spherical aberration correction values including a newly altered one, and when the optimum evaluation signal value does not exist within the range defined by the plurality of spherical aberration correction values, further determines whether or not a spherical aberration correction value to be altered next is not smaller than the limit value, and when the result of this determination indicates that the spherical aberration correction value to be altered next is not smaller than the limit value, sets a spherical aberration correction value based on the limit value as the first adjustment value.