To stably perform the recording and reproducing of a high density optical disk without using a double servo in an optical disk provided with a high numerical aperture(NA) objective lens.
A spherical aberration and a come aberration in the radial direction are simultaneously detected, the coma aberration generated due to the eccentricity of the objective lens 109 is corrected in real time and the allowable eccentricity of the objective lens is increased. The focal point deviation signal of the inner and outer regions of a reflected luminous flux and the tracking deviation signal are detected respectively to simultaneously detect the spherical aberration and the coma aberration and the differential signals of the detected signals are used as a spherical aberration signal and coma aberration signal.
UMEDA MARIKO
SHIMANO TAKESHI
