US Patent 7394049 Optical disk apparatus and pickup unit

An optical disk apparatus includes a light emitting unit, a light detecting unit, a tracking error signal generating unit, and a tracking control unit. The light emitting unit emits a single light beam onto an optical disk. The light detecting unit includes at least three light detecting portions, each being configured to receive light reflected off the optical disk and produce corresponding output. The at least three light detecting portions are arranged in a track direction of the optical disk. The tracking error signal generating unit generates at least two types of the tracking error signal using the outputs from the at least three light detecting portions. The tracking control unit performs tracking control on the optical disk on the basis of the tracking error signal.