Patent ID: 7440362

Claim:
An optical disc drive comprising: a light source; a focusing section for focusing light emitted from the light source; a focus shifting section for shifting a focal point of the light by changing the position of the focusing section perpendicularly to a data storage layer of a given optical disc in accordance with a control signal which is a train of pulses; a light receiving section for receiving, at multiple areas, the light reflected from the data storage layer and generating light quantity signals representing quantities of the light received at the respective areas; a focus error signal generating section for generating a focus error signal based on the light quantity signals; and a control section for generating the control signal in response to the focus error signal such that the focal point of the light is transferred to a focus controllable range in which a focus control is able to be performed on the data storage layer, wherein the control section generates the control signal such that the focal point of the light being shifted toward the data storage layer is decelerated initially at a first acceleration and then at a second acceleration, the absolute value of the second acceleration being smaller than that of the first acceleration and the control signal for decelerating the focal point of the light at the second acceleration at least includes a first type of pulses that accelerate the focal point toward the focus controllable range and a second type of pulses that accelerate the focal point away from the focus controllable range, wherein the control section suspends controlling the focal point of the light after a first peak of the focus error signal is detected at the data storage layer, and wherein the control section further controls the focal point of the light to be shifted toward the data storage layer, in the case where an amplitude of the focus error passes a second peak at the data storage layer.