Patent ID: 7864639

Claim:
An optical disk apparatus comprising: four photodetectors which detect reflective light from an optical disk; a signal generating unit which obtains an all-addition signal corresponding to a wobbling guide groove which is formed on the optical disk from detected signals of the four photodetectors; a determination unit which determines a type of the optical disk; a slice level switch unit which performs switching to a slice level according to the type of the optical disk determined by the determination unit; a timing signal generating unit which generates first and second timing signals in accordance with an amplitude level of the all-addition signal from the signal generating unit and the slice level switched by the type of the optical disk from the slice level switch unit; a wobble signal generating unit which outputs a signal which is amplified with a low gain amount by the first timing signal in a case where first and second arithmetic signals, which are generated for a wobble signal on the basis of signals output from the four photodetectors, are at a high amplitude level, and outputs a signal which is amplified with a high gain amount by the second timing signal in a case where the first and second arithmetic signals are at a low amplitude level; an output unit which outputs a wobble signal by subtracting the second arithmetic signal from the first arithmetic signal output from the wobble signal generating unit; and a gain control unit which obtains a ratio between a high amplitude value and a low amplitude value of the wobble signal output from the output unit, and controls switching of the gain amount of the wobble signal generating unit based on the ratio.