Optical disc device

1. An optical disc device which can record and reproduce information by irradiating a face of an optical disc with laser light from an objective lens and perform label printing by irradiating the other face of the optical disc with the laser light from the objective lens, comprising:

a circuit for forming a focus error signal for a focus servo based on a reflection light from the optical disc exposed to the laser light; and

a data processing unit which can feedback-control a position to which the objective lens is moved by a focusing actuator, based on the focus error signal,

wherein when performing the label printing, the data processing unit feedforward-controls a position to which the objective lens is moved by the focusing actuator based on control data for the label printing,

an operation resolution of the focusing actuator in the feedforward control is made higher in comparison to an operation resolution of the focusing actuator in the feedback control,

in the feedback control, a control accuracy of a position of the objective lens with respect to a position of a focal point on the optical disc is ±1 micrometer or smaller, and

in the feedforward control, a control accuracy of a position of the objective lens with respect to a position of a focal point on the optical disc is between ±10 and ±30 micrometers.

2. The optical disc device of claim 1 , wherein the data processing unit has: an analog-to-digital conversion circuit which converts the focus error signal into digital data; a servo control circuit which an output of the analog-to-digital conversion circuit is input to and which produces servo control data; and a digital-to-analog conversion circuit which converts the servo control data output by the servo control circuit or the control data for label printing into analog signals, the optical disc device further comprising a driver circuit which amplifies an output of the digital-to-analog conversion circuit and supplies the resultant signals to the focusing actuator,

wherein the driver circuit is arranged so that its gain can be switched, and

the gain is switched and controlled so that the gain used in the feedforward control becomes smaller than the gain used in the feedback control.

3. The optical disc device of claim 2 , wherein the driver circuit is arranged so that its voltage gain can be switched.

4. The optical disc device of claim 1 , wherein the data processing unit has: an analog-to-digital conversion circuit which converts the focus error signal into digital data; a servo control circuit which an output of the analog-to-digital conversion circuit is input to, and which produces servo control data; a digital-to-analog conversion circuit for servo which converts servo control data output by the servo control circuit into analog signals; a digital signal processing circuit which reproduces record information read out from an optical disc; and an audio digital-to-analog conversion circuit which converts audio information reproduced by the digital signal processing circuit or the control data for label printing into analog signals, the optical disc device further comprising

a focusing driver circuit which amplifies an output of the digital-to-analog conversion circuit for servo or an output of the audio digital-to-analog conversion circuit and supplies the resultant to the focusing actuator, and

an audio driver circuit which amplifies an output of the audio digital-to-analog conversion circuit and outputs the resultant outside,

wherein an input of the focusing driver circuit is connected with an output of the digital-to-analog conversion circuit for servo when the feedback control is used to control a position to which the objective lens is moved by the focusing actuator, and

an input of the focusing driver circuit is connected with an output of the audio digital-to-analog conversion circuit, and the control data for label printing is supplied to an input of the audio digital-to-analog conversion circuit when the feedforward control is used to control the position to which the objective lens is moved by the focusing actuator.

5. An optical disc device which can record and reproduce information by irradiating a face of an optical disc with laser light from an objective lens and perform label printing by irradiating the other face of the optical disc with the laser light from the objective lens, comprising:

a circuit for forming a focus error signal for a focus servo based on a reflection light from the optical disc exposed to the laser light; and

a data processing unit which can feedback-control a position to which the objective lens is moved by a focusing actuator, based on the focus error signal,

wherein when performing the label printing, the data processing unit feedforward-controls a position to which the objective lens is moved by the focusing actuator based on control data for the label printing, and

when performing the feedforward control, the data processing unit switches and controls a gain of a driver circuit of the focusing actuator so as to become smaller than the gain in the feedback control.

6. The optical disc device of claim 5 , wherein the data processing unit performs a learning process which includes previously acquiring and storing, in a memory, the control data for label printing for determining a position of the objective lens in a focal point direction so that a quantity of reflection light reflected off the other face of the optical disc becomes maximum while moving a laser irradiation position in circumferential and radial directions of the optical disc, and uses the control data read out from the memory in the feedforward control.