Patent ID: 6317395
Filing Date: 2001-11-13
Classification: G11B

Abstract:
An optical disc device comprising;a rotation means for rotating a recording medium to a predetermined number of rotations,a focusing means for focusing and irradiating a light beam on the recording medium,a first shift means for shifting a light beam focused on the recording medium across a track,a second shift means for shifting the focal point of the light beam focused by said focusing means in a direction substantially perpendicular to an information-recording surface on the recording medium,a light detection means for receiving reflected light from the recording medium,a focusing condition detection means for detecting the focusing condition of the light beam irradiated on the information-recording surface based on an output signal of said light detection means,a focus control means for driving said second shift means based on an output signal of said focusing condition detection means so as to control the focusing condition of said light beam on the information-recording surface to a predetermined condition,a track displacement detection means for detecting a positional displacement between the light beam on the recording medium and a track based on an output of said light detection means,a tracking control means for controlling the drive of said first shift means according to an output signal of said track displacement detection means so as to position the light beam on the recording medium on the track,a reproduction speed setting means for varying the reproduction speed according to the kind or recorded condition of information on the recording medium, anda reproduction speed detection means for measuring and detecting an actual reproduction speed,whereby on varying the reproduction speed of the recording medium from a first to a second reproduction speed by said reproduction speed setting means, the gain or frequency characteristic of said focus control means or said tracking control means is varied based on a detected value by said reproduction speed detection means, at least until an actual reproduction speed has shifted to the second reproduction speed, so as to provide a stable reproduction operation during a transition period of the actual reproduction speed from the first to the second reproduction speed.