Patent ID: 6775208
Filing Date: 2004-08-10
Classification: G11B

Abstract:
In an optical information reproducing apparatus, a method for controlling a focus speed of a pick-up head while performing a layer jump operation over a multi-layer optical disk, the optical information reproducing apparatus comprising the pick-up head, an actuator and a counter, the pick-up head comprising an objective lens positioned over a first focus of the multi-layer optical disk and generating an RF level signal in response to a signal reflected from the multi-layer optical disk, the actuator being electronically coupled to the pick-up head for driving the objective lens to perform the layer jump operation in response to a kick pulse signal, the counter for generating a counter value in response to the kick pulse signal, the method comprising:sending the kick pulse signal to the actuator for kicking the objective lens out of the first focus, and concurrently starting the counter for generating the counter value; processing the RF level signal and the counter value for generating a speed control data according to a predetermined procedure; and driving the objective lens to a second focus through the actuator in response to the speed control data, wherein the predetermined procedure comprises the steps of: (a) differentiating the RF level signal with time for generating an RF differential value; (b) checking whether the polarity of the RF differential value is positive; (c) if NO in step (b), checking whether the counter value exceeds a predetermined counter value; and (d) if NO in step (c), executing step (a), if YES in step (c), generating the speed control data.