Patent ID: 8451699

Claim:
An optical information reproduction device for reproducing information from an optical information recording medium, comprising: a light source that emits a laser beam; a condensing unit that generates a near-field light and condenses the laser beam on the optical information recording medium; a rotation unit that rotates the optical information recording medium; a light quantity detection unit that detects light quantity of return light from an area where the near-field light is generated; a gap control unit that controls a gap between the condensing unit and the optical information recording medium based on the light quantity of the return light detected by the light quantity detection unit; a tilt calculation unit that calculates, in a state where the gap is controlled by the gap control unit, an inclination amount between the condensing unit and the optical information recording medium based on the light quantity of the return light detected by the light quantity detection unit; a tilt error signal generation unit that generates from the inclination amount calculated by the tilt calculation unit a tilt error signal, which is a signal from which a fluctuation component of the return light generated due to decentering of the optical information recording medium is removed; and a tilt control unit that controls the inclination between the condensing unit and the optical information recording medium based on the tilt error signal generated by the tilt error signal generation unit, wherein the light quantity detection unit includes a light quantity detection unit for decentering detection that detects a light quantity of a part of the return light, in order to detect the fluctuation component of the return light generated due to decentering of the optical information recording medium, the light quantity detection unit for decentering detection is located in a position where the detected light quantity of the part of the return light changes in response to the fluctuation of the return light generated due to decentering of the optical information recording medium, and the tilt error signal generation unit generates the tilt error signal based on the inclination amount and the light quantity of the part of the return light detected by the light quantity detection unit for decentering detection.