Optical disc drive and control method thereof

An optical disc drive comprising:

• a pickup module including an objective lens to focus a laser beam on a surface of a recording layer of an optical disc;
• and
• a servo-control unit arranged to generate a focus driving signal to drive the objective lens included in the pickup module to focus the laser beam on a target track of the optical disc, based on a focus error signal obtained from a signal corresponding to a quantity of the laser beam reflected from the surface of the optical disc,
• wherein a high frequency broadband control and a low frequency broadband control of the focus error signal are performed such that the objective lens can track the surface of the recording layer of the optical disc and travel in an optical axis of the laser beam and wherein the high frequency broadband control is performed prior to the low frequency broadband control.

An optical disc drive comprising:

• a pickup module including an objective lens to focus a laser beam on a surface of a recording layer of an optical disc;
• and
• a control unit arranged to perform a focus servo-control of the pickup module using a high frequency broadband control and a low frequency broadband control of a focus error signal obtained from a signal corresponding to a quantity of the laser beam reflected from the surface of the optical disc,
• wherein the high frequency broadband control is performed prior to the low frequency broadband control.

An optical disc drive, comprising:

• a pickup module comprising an objective lens to focus light on target layer of an optical disc in accordance with a focus driving signal and at least one photodetector to generate an electrical signal proportionate to the light reflected from each of the layers of the optical disc;
• an amplifier electrically coupled to the photodetector to receive the electrical signal, to generate therefrom a focus error signal indicative of an error in a position of the objective lens, and to generate therefrom a plurality of independent focus control signals;
• and
• a servo-controlling unit electrically coupled to the amplifier to generate the focus driving signal such that a signal level of the focus error signal is bound to within a target degree of error, the servo-controlling unit operable into a plurality of states in accordance with signal levels of the focus control signals in which the servo-controlling unit, while in a first of the states, provides the focus driving signal in accordance with the level of the focus error signal and, while in a second of the states, compensates the focus driving signal for an offset in the level of the focus error signal that precludes the focus error signal from being bound to within the target degree of error.

A method for focusing an objective lens onto an optical disc in an optical disc drive, the method comprising:

• receiving an electrical signal proportionate to light reflected from a target layer of the optical disc;
• generating a focus driving signal proportionate to a signal level of a focus error signal determined from the received electrical signal;
• positioning the objective lens relative to the optical disc in accordance with the focus driving signal;
• determining after a predetermined time interval whether the signal level of the focus error signal is bound to within a target degree of error;
• compensating the focus driving signal for an offset in the signal level of the focus error signal such that the focus error signal is bound to within the target degree of error subsequent to the lapsing of the time interval;
• and
• positioning the objective lens relative to the optical disc in accordance with the compensated focus driving signal.