Optical disc drive

A method for getting the focal point of light transferred to a focus controllable range by an optical disc drive, the optical disc drive comprising:

• a light source;
• a focusing section for focusing the light emitted from the light source;
• a focus shifting section for shifting the 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;
• 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;
• and a focus error signal generating section for generating a focus error signal based on the light quantity signals,
• wherein the method comprises the steps of:
• (a) generating a first control signal in response to the focus error signal and supplying the first control signal to the focus shifting section such that the focal point of the light being shifted toward the data storage layer is decelerated at a first acceleration;
• and
• (b) generating a second control signal and supplying the second control signal to the focus shifting section after the step (a) such that the focal point of the light is decelerated at a second acceleration and that the absolute value of the second acceleration is smaller than that of the first acceleration.

A processor for use in an optical disc drive, the optical disc drive comprising:

• a light source;
• a focusing section for focusing light emitted from the light source;
• a focus shifting section for shifting the 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;
• 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;
• and a focus error signal generating section for generating a focus error signal based on the light quantity signals,
• wherein the processor includes:
• a first shifting control section for generating a control signal in response to the focus error signal and supplying the control signal to the focus shifting section such that the focal point of the light being shifted toward the data storage layer is decelerated at a first acceleration;
• and
• a second shifting control section for generating another control signal and supplying the control signal to the focus shifting section such that the focal point of the light is decelerated at a second acceleration and that the absolute value of the second acceleration is smaller than that of the first acceleration.

A computer program product for use with an optical disc drive for focus control purposes, the optical disc drive comprising:

• a light source;
• a focusing section for focusing the light emitted from the light source;
• a focus shifting section for shifting the 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;
• 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,
• wherein the computer program product causes the optical disc drive to perform steps of:
• (a) generating a first control signal in response to the focus error signal and supplying the first control signal to the focus shifting section such that the focal point of the light being shifted toward the data storage layer is decelerated at a first acceleration;
• and
• (b) generating a second control signal and supplying the second control signal to the focus shifting section such that the focal point of the light is decelerated at a second acceleration and that the absolute value of the second acceleration is smaller than that of the first acceleration.