Patent ID: 7158453
Filing Date: 2007-01-02
Classification: G11B

Abstract:
1. A tracking control system for outputting a tracking control signal for performing tracking control of an optical pickup including a plurality of light detecting sections each of which detects, via a lens, reflected light of a light beam applied to an optical disk, converts the detected light into an electric signal, and outputs the signal, the tracking control system comprising: a differential phase tracking error signal generating section for generating and outputting a differential phase tracking error signal based on a difference in phase between signals output from the plurality of light detecting sections; a differential amplitude tracking error signal generating section for generating and outputting a differential amplitude tracking error signal based on a difference in value between signals output from the plurality of light detecting sections; a balance correction amount calculating section for obtaining a direct-current component of the differential amplitude tracking error signal, and obtaining and outputting, as a balance correction amount, a value by which the differential phase tracking error signal should be shifted in accordance with the direct-current component of the differential amplitude tracking error signal such that a direct-current component of the differential phase tracking error signal approaches a given reference potential; a balance changing section for shifting the differential phase tracking error signal in accordance with the balance correction amount, thereby outputting the shifted signal as a differential phase tracking error signal after balance change; and a tracking control section for generating and outputting the tracking control signal in accordance with the differential phase tracking error signal after balance change, wherein the tracking control section outputs the tracking control signal such that the optical pickup is moved in accordance with a drive value shift signal output from the balance correction amount calculating section, and the balance correction amount calculating section includes: a program storing section for storing a program; a CPU for executing the program, outputting the drive value shift signal for giving an instruction to move the optical pickup to a first tracking position closer to the outer edge of the optical disk than a position under tracking control and to a second tracking position closer to the inner edge of the optical disk than the position under tracking control, obtaining a value, as a conversion factor, by dividing a difference in the direct-current component of the differential phase tracking error signal between when the optical pickup is at the first tracking position and when the optical pickup is at the second tracking position by a difference in the direct-current component of the differential amplitude tracking error signal between when the optical pickup is at the first tracking position and when the optical pickup is at the second tracking position, and obtaining a value according to a product of the direct-current component of the differential amplitude tracking error signal and the conversion factor, thereby outputting the obtained value as a balance value; and a balance correction section for outputting the balance correction amount in accordance with the balance value.