Patent ID: 7257053
Filing Date: 2007-08-14
Classification: G11B

Abstract:
1. An optical disk apparatus, comprising: a converging means for converging and irradiating a light beam from a light source toward a rotating information carrier; a focus displacement signal detection means for generating a signal in accordance with a positional displacement of a focus of the light beam with respect to an information surface of the information carrier; a focus shifting means for shifting the converging means in a direction normal to the information surface of the information carrier; a focus control means for driving the focus shifting means in accordance with the signal from the focus displacement signal detection means, and performing a control such that the focus of the light beam follows the information surface of the information carrier; an information surface detection means for detecting whether the focus of the light beam is near the information surface of the information carrier based on an amount of a light beam reflected from the information carrier, if the focus control means is in an inoperative state; and a collision evasion means for changing a displacement direction of the converging means from a direction approaching the information carrier to a direction away from the information carrier in accordance with an information surface detection signal and when the focus control means is in an inoperative state, said collision evasionmeans generating a driving signal for the focus shifting means such that the converging means is displaced in a direction away from the information carrier if a signal is generated by the information surface detection means, otherwise, the converging means is displaced with a predetermined slope in a direction approaching the information carrier.