Focusing control method for label side of lightscribe discs

A label side focusing control method, comprising the following steps:

• (1) focusing on a label side of a disc according to a predetermined base voltage, and detecting and recording light summed signals corresponding to each spoke of a plurality of spokes along a path;
• (2) finding a largest light summed signal from light summed signals and subtracting other light summed signals from the largest light summed signal to generate an error signal;
• (3) multiplying the error signal according to a gain to generate a gain signal;
• (4) adding the gain signal to the base voltage to generate an upper reference voltage and subtracting the gain signal from the base voltage to generate a lower reference voltage;
• (5) taking the upper reference voltage and the lower reference voltage as a focusing control voltage to control a pickup head to circle once around the label side to detect and record the light summed signals;
• (6) finding a largest light summed signal corresponding to each spoke, and taking a corresponding voltage of the largest light summed signal corresponding to each spoke as a focusing control voltage with respect to the corresponding spoke;
• and
• (7) approaching each focusing control voltage corresponding to each spoke by curve fitting to generate an approximate control focusing voltage curve.