Optical disk device

An optical disk device comprising:

• an optical pickup of outputting a main beam and sub-beams preceding and following the main beam onto an optical disk,
• wherein, in order to reproduce information recorded on the optical disk, a digitally modulated signal and a focusing error signal are detected based on a reading spot of the main beam of the optical pickup, and a tracking error signal is detected based on reading spots of the preceding and following sub-beams of the optical pickup,
• the optical disk device further comprising:
• a tracking error signal generation circuit connected to a first output terminal through which a preceding sub-beam returning light signal is obtained, the preceding sub-beam returning light signal being an electrical signal obtained by converting returning light of the preceding sub-beam of the optical pickup, and a second output terminal through which a following sub-beam returning light signal is obtained, the following sub-beam returning light signal being an electrical signal obtained by converting returning light of the following sub-beam of the optical pickup, wherein the tracking error signal generation circuit generates the tracking error signal based on the preceding and following sub-beam returning light signals from the first and second output terminals;
• a tracking control circuit of receiving the tracking error signal of the tracking error signal generation circuit and performing tracking control based on the tracking error signal;
• a defect period detection circuit of detecting a defect period of the optical disk and outputting a first defect period signal, and a second defect period signal indicating a second defect detection period in which detection of entry into a defect period is later and detection of exit from the defect period is earlier than those of the first defect period signal, based on the preceding sub-beam returning light signal from the first output terminal or the preceding and following sub-beam returning light signals from both the first and second output terminals;
• a hold circuit of receiving the first defect period signal of the defect period detection circuit and holding the tracking control by the tracking control circuit based on the first defect period signal;
• an AGC circuit connected to a third output terminal through which a main beam returning light signal is obtained, the main beam returning light signal being an electrical signal obtained by converting returning light of the main beam of the optical pickup, wherein the AGC circuit generates an RF signal obtained by normalizing an amplitude of the main beam returning light signal to a predetermined value;
• and
• an AGC hold circuit of fixing a gain of the AGC circuit to a predetermined value during the second defect detection period indicated by the second defect period signal of the defect period detection circuit.