Patent ID: 8094527
Filing Date: 2012-01-10
Classification: G11B

Abstract:
1. An optical disc apparatus comprising: a light source; an objective lens which focuses light that is emitted from the light source on a recording surface of an optical disc; a photo detecting portion which receives reflected light that is reflected by the optical disc to perform photoelectric conversion; an objective lens actuator which moves the objective lens along a focus direction; a focus control portion which performs focus control such that a state is realized where a focus position of the objective lens is always matched on the recording surface by controlling the objective lens actuator; a first signal generating portion which generates a first signal that is obtained by processing signal which is output from the photo detecting portion, and which shows a peak in case where the focus position of the objective lens is matched on the recording surface; a second signal generating portion which generates a second signal that is obtained by slicing the first signal at a prescribed level and digitalizing; and a movement stopping portion the prescribed condition is that the second signal is asserted by existence of the recording surface that is a target to be reproduced or to be recorded, and thereafter the second signal is negated and then remains in the negated state for a predetermined time interval calculated by formula (1) below: where t: an actually measured movement time which is determined based on the first signal and which is required for the focus position of the objective lens to move from the surface of the optical disc to the recording surface when the objective lens is moved at a prescribed speed by the objective lens actuator, α: a coefficient which fulfils 0<α<1, WD: distance from tip of the objective lens to the surface of the optical disc when the focus position of the objective lens is matched on the recording surface, L: distance from the surface of the optical disc to the recording surface, v v