US Patent 7847812 Focusing control method for reading/writing optical disc

A label pattern can be created on a label side of an optical disc under well focus control. An optical disc is first loaded in an optical disc drive with the label side thereof facing to an optical head of the optical disc drive. Then, the optical head is actuated along a focusing direction. Meanwhile, a light intensity addition signal is generated in response to optical signals reflected from the optical disc and received by the optical head. A closed-loop control operation of the optical head is performed according to the light intensity addition signal after the light intensity addition signal up-crosses a threshold. Then, a label pattern can be defined on the label side of the optical disc with the closed-loop control operation.