Patent ID: 7724626

Claim:
An optical information recording/reproducing apparatus comprising: an optical pickup including: a laser light source, a beam separation means which separates a laser beam emitted by the laser light source into a main beam and at least two sub beams, a converging optical system which converges the main beam and the sub beams and forms three separate convergence spots on a recording surface of an optical information record medium on which guide grooves are formed at preset pitches, and a photodetector which is placed to receive each of reflected beams of the three convergence spots from the optical information record medium with a photoreceptor surface divided into at least two faces; a push-pull signal generation circuit which generates push-pull signals regarding the main beam and the sub beams respectively by executing proper operations to photoelectric signals obtained from the photoreceptor surfaces of the optical pickup; a differential push-pull signal generation circuit which generates a differential push-pull signal by adding all or part of the push-pull signals regarding the sub beams together, amplifying the added signal by an amplification factor K, and subtracting the amplified signal from the push-pull signal regarding the main beam; and an amplification factor control means which changes the amplification factor K depending on the interval between the guide grooves of the optical information record medium, wherein the amplification factor K satisfies an expression K=K 1 *K 2 , K 1 is a value obtained by dividing a light quantity detected at main beam spot by a sum of light quantities detected at two sub beam spots, and K 2 is a compensation coefficient for compensating for the difference between a modulation degree of a push-pull signal obtained from the main beam spot and a modulation degree of a push-pull signal obtained from the sub beam spots.