Patent ID: 7054241

Claim:
An optical disc apparatus comprising: a light source for irradiating a light beam onto a data side of an information recording medium; converging means for converging said light beam; transferring means for transferring said converging means in such a way that the distance between said converging means and said data side changes; photo-receiving means for receiving returned light of the light beam reflected by said data side; converging state detecting means for generating a signal according to a converging state of the light beam on the data side of said information recording medium based on a signal from said photo-receiving means; focus controlling means for outputting a drive signal to said transferring means based on a signal from said converging state detecting means and controlling said light beam in such a way that said light beam is in a predetermined converging state; tilting means for tilting said converging means; tilt calculating means for determining at least one coefficient of an approximate function used for approximating a shape of said data side based on said drive signal and determining an amount of tilt of said data side at an arbitrary radius position using said determined at least one coefficient and the approximate function; and tilt controlling means for driving the tilting means according to said amount of tilt and irradiating the light beam onto said data side in a direction substantially perpendicular to said data side.