Patent ID: 8072850

Claim:
A method of adjusting spherical aberration and defocus for an information recording or reproducing apparatus, irradiating a recording medium with converged light, detecting reflected light from the recording medium generated by the irradiation of the converged light, recording or reproducing information to the medium by using tracking error signal and readout signal of the information recorded in the medium generated from the reflected light, comprising: searching a first position in which an amplitude of said tracking error signal is within a predetermined range from the maximum value of the tracking error signal in two dimensional plane that is formed by quantity of spherical aberration and quantity of defocus included in the converged beam by adjusting the optical system; writing marks on the recording medium based on results of searching the first position; searching a second position in which an amplitude of said readout signal is maximum in said two dimensional plane using said first position as starting point for the search by adjusting the optical system, said readout signal being retrieved from said marks; and compensating said spherical aberration and defocus in the converged light by using the quantity of spherical aberration and the quantity of defocus corresponding to said second position.