Tracking control device, tracking control method, and optical disc apparatus

A tracking control method comprising:

• detecting, from a detection signal of an optical detector that receives light reflected from a track of a rotating optical disc, a tracking error signal, and a crossing direction, a crossing period and a crossing velocity of an objective lens with respect to the track;
• detecting an optical-disc eccentric angle of the rotating optical disc;
• generating a first tracking drive signal, on a basis of the detected tracking error signal, for driving an objective lens actuator that moves the objective lens of an optical pickup in a tracking direction;
• generating a second tracking drive signal, on a basis of the detected crossing direction and crossing period, for converging the crossing velocity into a vicinity of zero;
• and
• switching a drive signal supplied to the objective lens actuator so as to cause to execute second driving for driving the objective lens actuator on a basis of the second tracking drive signal and switch from the second driving to first driving for driving the objective lens actuator on a basis of the first tracking drive signal, thereby causing to execute the first driving;
• wherein the second driving of the objective lens actuator based on the second tracking drive signal is started at a timing when the optical-disc eccentric angle is substantially 0 degrees or 180 degrees.

An optical disc apparatus comprising:

• a spindle motor to rotate an optical disc;
• a laser light source to irradiate a track of the rotating optical disc with laser light;
• an objective lens to condense the laser light and light reflected from the track;
• an objective lens actuator to move the objective lens at least in a tracking direction;
• an optical detector to receive the light reflected from the track;
• a signal detector to detect, from a detection signal of the optical detector, a tracking error signal, and a crossing direction, a crossing period, and a crossing velocity of the objective lens with respect to the track;
• a first drive signal generator to generate a first tracking drive signal for driving the objective lens actuator that moves the objective lens of an optical pickup in the tracking direction on a basis of the tracking error signal detected by the signal detector;
• a second drive signal generator to generate a second tracking drive signal for converging the crossing velocity into a vicinity of zero on a basis of the crossing direction and the crossing period detected by the signal detector;
• a drive signal switch to switch a drive signal supplied to the objective lens actuator;
• and
• a system controller to control operation of the first drive signal generator, the second drive signal generator and the drive signal switch so as to cause to execute second driving for driving the objective lens actuator on a basis of the second tracking drive signal and switch from the second driving to first driving for driving the objective lens actuator on a basis of the first tracking drive signal, thereby causing to execute the first driving;
• wherein:
• the signal detector includes an optical-disc eccentric angle detector to detect an optical-disc eccentric angle of the rotating optical disc, and
• the system controller causes to start the second driving of the objective lens actuator based on the second tracking drive signal at a timing when the optical-disc eccentric angle is substantially 0 degrees or 180 degrees.