| 摘要 |
The present invention accurately operates a tilt servo even if a gap servo is operated with a small gap. A condensing unit (102) generates a near-field light and condenses a laser beam on an optical disk (1), a light quantity detection unit (104) detects light quantity of return light from an area where the near-field light is generated, a gap control unit (105) controls a gap between the condensing unit (102) and the optical disk (1) based on the light quantity of the return light, a tilt calculation unit (106) calculates, in a state of controlling the gap, an inclination amount between the condensing unit (102) and the optical disk (1) based on the light quantity of the return light, a tilt error signal generation unit (107) generates from the inclination amount a tilt error signal, which is a signal from which a fluctuation component of the return light generated due to decentering of the optical disk (1) is removed, and a tilt control unit (108) controls the inclination between the condensing unit (102) and the optical disk (1) based on the tilt error signal.
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