JPH0644596A - Optical disk device - Google Patents

Abstract

PURPOSE:To eliminate the offset of a track error signal by supplying no current to a positioner coil when the mean value of the offset value of the track error signal becomes larger than a prescribed value CONSTITUTION:A track error offset detecting circuit 12 monitors the offset of the track error signal TE21 at all times and finds its mean value TEL. An arithmetic circuit 14 compares the mean value TEL with a limit value VE from a level setting circuit 13 and outputs a signal to an output control circuit 15 when VE<=TEL. The control circuit 15 disconnects a filter arithmetic part 11 and a current amplifier 10 from each other with the signal to prevent a current from flowing to the positioner coil 7. Consequently, an objective 3 follows up an optical head 9 and the offset of the track error signal TE21 is eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention, when information is read from an information string recorded concentrically or spirally on an optical disk medium, searches the information string by a track coarse position control operation to perform a track minute position control operation. The present invention relates to an optical disc device for reading information by causing an objective lens to follow an information string designated by.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram showing an example of a conventional optical disk device, and FIG. 6 is a characteristic diagram showing accelerations of an optical head and an objective lens in the seek operation of the example of FIG.

When information is read from an information string (track) recorded concentrically or spirally on an optical disk medium, an information string (track) is searched by a track coarse position control operation and specified by a track minute position control operation. As shown in FIG. 5, the conventional optical disc apparatus that reads information by causing the objective lens to follow the generated information string moves the objective lens 33 to the target track while moving the objective lens 33 in the moving position. The objective lens position detector 34 to be detected, a filter calculation unit 41 for performing phase compensation processing on the output signal of the objective lens position detector 34, and a movement range signal (predetermined movement range of the objective lens 33). Vm) 45 and the output signal of the filter calculation unit 41, and the optical head 3 based on the signal from the comparator 42. A positioner speed controller 43 for outputting a signal for moving the, positioner coil 37 converts the output signal of the positioner velocity control unit 43 in the current
And a current amplifier 40 for supplying

In the optical disc device configured as described above, the coarse track position control operation and the fine track position control operation in the positioning operation are first performed by an instruction from a higher-level device (for example, an arithmetic processor) up to the target track of the objective lens. A move command is issued to move 33.
At this time, if the movement to the target track is performed by the track minute position control operation, it is predetermined 1
A signal for moving the track is sent from the host device to the track coil 3 by an amount corresponding to the moving distance to the target track.
By applying it to 2, the objective lens 33 is moved to the target track. The amount of movement of the objective lens 33 at this time is monitored by the objective lens position detector 34, and the output signal of the objective lens position detector 34 is phase-compensated and output in the filter calculation unit 41. The comparator 42 is
The output signal and the movement range signal (V
m) 45. When the output signal of the objective lens position detector 34, which indicates the amount of movement of the objective lens 33, becomes larger than the movement range signal (Vm) 45, the positioner speed control unit 43 causes the positioner coil 3 via the current amplifier 40.
An optical head 3 which supplies a current to the laser light source 7 and has a laser light source 38
9 is moved in the same direction as the moving direction of the objective lens 33.

Acceleration 5 of the optical head in this moving operation
As shown in FIG. 6, 1 is smaller than the acceleration 52 of the objective lens at the time of rising, but increases with time and becomes larger than the acceleration 52 of the objective lens.

[0006]

As described above, the conventional optical disk device has the following problems when the track coarse position control operation and the track minute position control operation in the positioning operation are performed.
Since the acceleration of the optical head becomes larger than the acceleration of the objective lens, the objective lens deviates from the optical axis and an offset occurs in the track error signal, which makes the tracking servo unstable or unable to pull in. have.

[0007]

An optical disk device according to the present invention comprises an objective lens for focusing laser light for reading information recorded in an information sequence provided concentrically or spirally on an optical disk medium, and the objective. A vertical position control unit for moving the objective lens in a vertical direction with respect to the optical disc medium in order to focus the lens on the optical disc medium, and a fine position control unit for causing the laser beam to follow the information sequence. And a track coarse position control unit for searching the specified information string on the optical disc medium, the photodetector receiving reflected light from the optical disc medium, and the output signal of the photodetector. Track error offset detection circuit for detecting the offset value of the track error signal that is generated, Filter arithmetic unit that performs phase compensation processing on the clock error signal, a level setting circuit that sets a predetermined value, and an operation that compares the output signal of the track error offset detection circuit with the output signal of the level setting circuit. A circuit and an output control circuit for inputting an output signal of the filter arithmetic unit and an output signal of the arithmetic circuit and controlling the output signal of the filter arithmetic unit by the output signal of the arithmetic circuit, the output control circuit The drive current based on the output signal of is applied to the minute position control section.

[0008]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a waveform diagram showing waveforms of input signals and output signals of the track error offset detection circuit of the embodiment of FIG.
3 is a circuit diagram showing the details of the track error offset detection circuit of the embodiment of FIG. 1, and FIG. 4 is a waveform diagram showing the waveform of the output signal of the circuit of FIG.

In FIG. 1, an optical head 9 includes a laser light source 8, a beam splitter 5, a rising mirror 16, an objective lens 3, an objective lens position detector 4, a photodetector 6, a track coil 2 and a focus error detector (not shown). ), A focus actuator (not shown), and a positioner coil 7, and the optical disk medium 1 is moved in the radial direction by supplying a current to the positioner coil 7. The laser light emitted from the laser light source 8 is emitted from the beam splitter 5
Then, the incident laser light is incident on the objective lens 3 via the raising mirror 16, and the incident laser light is focused on the recording surface of the optical disc medium 1 to read information.

On the recording surface of the optical disc medium 1, information is recorded in a concentric or spiral information string (track), and the information can be optically read from this track. The reflected light from the optical disc medium 1 returns to the objective lens 3 again, a part of which is separated by the beam splitter 5 and is incident on the photodetector 6 and the focus error detector (not shown). The reflected light that has entered the focus error detector is converted into an electric signal, filtered, and then input to the focus actuator. The focus actuator operates so as to keep the distance of the objective lens 3 to the recording surface of the optical disc medium 1 constant according to the input signal. The reflected light incident on the photodetector 6 is converted into an electric signal and output as a track error signal (TE) 21. The track error signal (TE) 21 is input to the filter calculation unit 11 and the track error offset detection circuit 12. The filter calculation unit 11 performs a phase compensation process on the track error signal (TE) 21 according to the frequency of the track coil 2,
The output signal is sent to the output control circuit 15. The track error offset detection circuit 12 obtains the average value of the offset values of the track error signal (TE) 21 and outputs an offset value average value signal (TEL) 22. The offset value average value signal (TEL) 22 is input to the arithmetic circuit 14. The arithmetic circuit 14 uses the limit value signal 2 indicating the limit value (VE) preset in the level setting circuit 13.
3 and the offset value average value signal (TEL)
Are compared and the result is sent to the output control circuit 15. The output control circuit 15 sends a signal obtained by controlling the output signal of the filter calculation unit 11 according to the output signal of the calculation circuit 14 to the current amplifier 10. The current amplifier 10 converts the output signal of the output control circuit 15 into a current and moves the positioner coil. Send to 7. The positioner coil 7 is thereby provided with an optical head 9
To move.

The optical disk device configured as described above is
By an instruction from a host device (for example, an arithmetic processor),
When a movement command for moving the objective lens 3 to the target track is issued, a current is supplied to the positioner coil 7 to move the optical head 9. At this time, the acceleration of the objective lens 3 caused by the track coil 2 and the acceleration of the optical head 9 caused by the positioner coil 7 become larger than the acceleration of the objective lens 3 after a certain period of time. An offset occurs in the error signal (TE) 21, and therefore an offset also occurs in the filter calculation unit 11. At this time, as shown in FIG. 2A, the track error offset detection circuit 12 constantly monitors the offset of the track error signal (TE) 21, and as shown in FIG. 2B, its average value (TEL). Therefore, the arithmetic circuit 14 determines that the level setting circuit 13
From the track error offset detection circuit 12, and outputs a signal to the output control circuit 15 if VE ≦ TEL, and the output control circuit 15 outputs the signal. Thus, the connection between the filter calculation unit 11 and the current amplifier 10 is cut off so that no current flows through the positioner coil 7. As a result, the objective lens 3 catches up with the optical head 9 and the track error signal (TE) 21
The offset of is gone.

In the case of VE> TEL, the arithmetic circuit 14 does not output a signal, and therefore the output control circuit 15 keeps the filter arithmetic unit 11 and the current amplifier 10 connected, so that the current is supplied to the positioner coil 7. Then, the optical head 9 moves.

Track error offset detection circuit 12
Is a low pass filter (LPF) including a resistor 17 and a capacitor 18, as shown in FIG. Resistance 1
By appropriately selecting the value of 7 and the value of the capacitor 18, the high frequency signal of the track error signal (TE) 21 is cut and the offset value average value signal (TEL) of only the low frequency signal as shown in FIG. ) 22 can be output.

[0015]

As described above, in the optical disk device of the present invention, the track error offset detection circuit constantly monitors the offset value of the track error signal during the seek operation, and the average value becomes larger than the predetermined value. At this time, by controlling the acceleration of the optical head by preventing the current from flowing through the positioner coil, there is an effect that the objective lens can be made to follow the optical head to eliminate the offset of the track error signal. Therefore, there is an effect that a stable tracking operation can be performed without a track error offset due to the deviation of the optical axis.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a waveform diagram showing waveforms of an input signal and an output signal of the track error offset detection circuit of the embodiment of FIG.

3 is a circuit diagram showing details of a track error offset detection circuit of the embodiment of FIG.

FIG. 4 is a waveform diagram showing a waveform of an output signal of the circuit of FIG.

FIG. 5 is a block diagram showing an example of a conventional optical disc device.

6 is a characteristic diagram showing the acceleration of the optical head and the objective lens during the seek operation of the example of FIG.

[Explanation of symbols]

 1 Optical Disk Medium 2 Track Coil 3.33 Objective Lens 4.34 Objective Lens Position Detector 5 Beam Splitter 6 Photo Detector 7 37 Positioner Coil 8 38 Laser Light Source 9 39 Optical Head 10 40 Current Amplifier 11 41 Filter Operation Unit 12 Track error offset detection circuit 13 Level setting circuit 14 Arithmetic circuit 15 Output control circuit 16 Start-up mirror 17 Resistor 18 Capacitor 21 Track error signal (TE) 22 Offset value average value signal (TEL) 23 Limit value (VE) 42 Comparator 43 Positioner speed control unit 45 Moving range signal (Vm) 51 Optical head acceleration 52 Objective lens acceleration

Claims (2)

[Claims] 1. An objective lens for converging a laser beam for reading information recorded in an information sequence provided concentrically or spirally on an optical disc medium, and the objective lens is focused on the optical disc medium. A vertical position control unit for moving the objective lens in the vertical direction with respect to the optical disc medium, a fine position control unit for causing the laser beam to follow the information sequence, and the designated position on the optical disc medium. In an optical disc device including a track coarse position control unit for searching an information string, a photodetector that receives reflected light from the optical disc medium and an offset value of a track error signal generated from an output signal of the photodetector are detected. Track error offset detection circuit and phase compensation processing for the track error signal A filter operation unit, a level setting circuit for setting a predetermined value, an operation circuit for comparing the output signal of the track error offset detection circuit and the output signal of the level setting circuit, and an output signal of the filter operation unit. And an output control circuit for inputting the output signal of the arithmetic circuit and controlling the output signal of the filter arithmetic unit by the output signal of the arithmetic circuit, and the drive current based on the output signal of the output control circuit is provided. An optical disk device characterized in that a voltage is applied to a minute position control section. 2. The optical disk device according to claim 1, wherein the track error offset detection circuit is composed of a low pass filter.