Patent ID: 8085631

Claim:
A tracking control device for converging a main beam and a sub beam on an information recording medium having plural information layers, and controlling a convergence point of the main beam to scan a track on the information layer, the tracking control device comprising: a tracking error signal detecting section which detects a tracking error signal depending on a positional displacement between the convergence point of the main beam, and the track on the information layer; and a tracking control section which controls the convergence point of the main beam to scan the track, based on the tracking error signal detected by the tracking error signal detecting section, wherein the tracking error signal detecting section includes: a sub push-pull signal correcting section which corrects a sub push-pull signal to be generated from returning light of the sub beam in such a manner that a track crossing component of a main push-pull signal to be generated from returning light of the main beam, and a track crossing component of the sub push-pull signal to be generated from the returning light of the sub beam are cancelled; a low pass filter which reduces a high frequency component of the sub push-pull signal corrected by the sub push-pull signal correcting section; and a tracking error signal generating section which subtracts a sub push-pull signal passing the low pass filter from the main push-pull signal to thereby generate the tracking error signal; the tracking error signal detecting section includes a switch which switches between a first state where the sub push-pull signal passing the low pass filter is inputted to the tracking error signal generating section, and a second state where the sub push-pull signal before the input to the sub push-pull signal correcting section is inputted to the tracking error signal generating section; and the tracking control device further includes: an information layer number detecting section which detects the number of the information layers of the information recording medium, and a switching control section which controls the switch to the first state, if at least two information layers are detected by the information layer number detecting section, and controls the switch to the second state, if one information layer is detected by the information layer number detecting section.