Patent ID: 6934228

Claim:
An optical head comprising: a semiconductor laser; means for generating a plurality of reflected light beams from at least one forward spot on an optical disk in which a light-converging optical system converges light emitted from the semiconductor laser onto the optical disk having a periodic structure in a radial direction of the optical disk so as to form the at least one focused spot on the optical disk, the plurality of reflected light beams having polarities of intensity distribution variations which are substantially inverted to each other when the periodic structure crosses the at least one focused spot on said disk; an optical detection system which splits the plurality of reflected light beams and detects the split reflected light beams; and an electrical circuit which provides a focus error signal of the at least one focused spot and a tracking error signal from the plurality of reflected light beams; and wherein the electrical circuit adds respective focus error signals of the plurality of reflected light beams so that variations in the focused error signals caused by the intensity distribution variations cancel each other out, to provide a difference signal between the focus error signals, amplifies respective tracking error signals of the plurality of reflected light beams of which the polarities are substantially inverted from each other with a gain proportional to a ratio of a total amount of a reciprocal of each of the reflected light beams when one of the at least focused spot is on an information track of the optical disk, and then takes a difference between the respective amplified tracking error signals to provide a tracking error signal for the optical head.