Patent ID: 7304920
Filing Date: 2007-12-04
Classification: G11B

Abstract:
1. An optical head that records information on an optical disk and/or reproduces information recorded thereon, comprising: condensing means of condensing light on said optical disk to generate an optical spot; light receiving means of receiving a beam reflected by said optical disk; tracking error signal detecting means of detecting positional deviation of said optical spot from said information track on the basis of a signal detected by said light receiving means; and optical disk tilt detecting means of detecting a tilt in said optical disk relative to an optical axis of said condensing means on the basis of said tracking error signals, wherein said light receiving means has a plurality of light receiving areas that separate light upon reception so that a first sub-light-receiving-area receives a central area of said reflected beam, while a second sub-light-receiving-area receives a peripheral area of said reflected beam, said first sub-light-receiving-area is an almost rectangle having long sides equivalent to or longer than the diameter of a beam incident on said light receiving means and short sides shorter than the diameter of the beam incident on said light receiving means, the long sides extending in a direction perpendicular to the information tracks, said tracking error signal detecting means detects a first sub-tracking-error-signal in a received light signal obtained from said first sub-light-receiving-area and a second sub-tracking-error-signal in a received light signal obtained from said second sub-light-receiving-area, and said optical disk tilt detecting means compares said first sub-tracking-error-signal with said second sub-tracking-error-signal to detect a phase difference in signal waveform which may occur when said optical spot crosses said information track which phase difference indicates a tilt of a normal of the optical disk in a plane containing an optical axis of the condensing means, which plane is normal to a tangent of the information track of the optical disk.