Patent ID: 6563773
Filing Date: 2003-05-13
Classification: G11B

Abstract:
A tracking control apparatus for a disc having a physical factor changing a shape or a reflection coefficient in a tangential direction of a record track of said disc, comprising:a detecting device having a first detector, a second detector disposed adjacent to said first detector in a radial direction of said disc, a third detector disposed adjacent to said second detector in the tangential direction and a fourth detector disposed adjacent to said first detector in the tangential direction and adjacent to said third detector in the radial direction; a first amplifying device for amplifying an output signal of said first detector and an output signal of said fourth detector by a first gain; a second amplifying device for amplifying an output signal of said second detector and an output signal of said third detector by a second gain; a first adding device for calculating a first sum signal, which is a sum of the amplified output signal of said first detector and the amplified output signal of said fourth detector; a second adding device for calculating a second sum signal, which is a sum of the amplified output signal of said second detector and the amplified output signal of said third detector; a first subtracting device for calculating a difference between the first sum signal and the second sum signal and outputting the difference as a tracking error signal; a second subtracting device for calculating a first difference signal, which is a difference between the output signal of said first detector and the output signal of said fourth detector; a third subtracting device for calculating a second difference signal, which is a difference between the output signal of said second detector and the output signal of said third detector; and an amplitude comparing device for comparing amplitudes of the first difference signal and the second difference signal with each other, and determining the first gain and the second gain on the basis of a result of comparison.