Patent ID: 6807133
Filing Date: 2004-10-19
Classification: G11B

Abstract:
An optical head, comprising:a laser beam source; an objective lens for condensing beam from said laser beam source on an optical disk; and a detector for detecting reflected light from said optical disk, wherein said optical head further comprises: means for generating a first focal shift signal and a first tracking shift signal by use of an inside light flux containing a light flux center of The reflected light out of the reflected light from said optical disk, and means for generating a second focal shift signal and a second tracking shift signal by use of an outside light flux enclosing said inside light flux out of the reflected light from the optical disk, and wherein a spherical aberration signal is generated based on a difference between said first focal shift signal and said second focal shift signal, and a coma aberration signal is generated based on a difference between said first tracking shift signal and said second tracking shift signal.