JPH08329491A - Optical disk device - Google Patents

Abstract

PURPOSE: To cancel DC offset operation at high speed by detecting the DC offset of a tracking error signal by means of a DC offset detector and outputting it to an offset detecting instrument. CONSTITUTION: When an optical disk is rotated, a fine adjustment indicator 34 sends a signal FD to a driving amplifier 31 and finely move a bobbin 2 by a current complied with the signal FD. A DC offset detector 23 sends the detected signal to a converter 24 of a measuring instrument 27. Thus, the converter 24 performs A/D conversion of the signal, sends it to a microcomputer 25 as the offset data and sends cancel instructing data based on the state of the displacement of a tracking position to a D/A converter 26. The converter 26 D/A converts the instructed data and sends a cancel instructing signal to a variable resistor 28. Consequently, a tracking error signal from which the DC offset of a signal TE is automatically removed is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk device for reproducing or recording an optical disk, and more particularly to an optical disk device used as an external storage device of a computer.

[0002]

2. Description of the Related Art As optical discs, read-only audio CDs, read-only CD-ROMs, recordable optical discs for additional recording, rewritable magneto-optical discs, etc. have been put to practical use. Development for application and high performance is actively carried out.

Information tracks are spirally or concentrically formed on these optical disks, and information signals are recorded as very small pit rows on the tracks.

Therefore, in the optical disc apparatus for reproducing the information signal of these optical discs, the light beam is focused on the information pits by the focus servo control, and the light spot of the light beam is made on the pit row by the tracking servo control. Must be tracked with high accuracy.

In recent years, in order to properly reproduce the recorded information signal, automatic adjustment has been performed by introducing a microcomputer so as to optimize the state of following the track.

A conventional optical disk device will be described below with reference to the drawings. FIG. 4 shows the structure of the optical pickup.

The optical pickup 12 has an objective lens 1, which is held by a bobbin 2. The bobbin 2 is mounted on the carriage 4 via a suspension spring 3 so that it can be finely moved in the radial direction of the optical disk. The carriage 4 is supported by a linear guide 5 so as to be capable of coarse movement in the radial direction of the optical disc (arrow A), and a position sensor 6 for detecting the relative position of the bobbin 2 and the carriage 4 is provided on the carriage 4. Further, a carriage coil 7 is adhered and fixed to the carriage 4. The carriage coil 7 is arranged so as to intersect with the magnetic flux from the magnet 8 to the linear guide 5 in the magnetic circuit constituted by the magnet 8, the yoke 9 and the linear guide 5.

A linear guide 5 and a spindle motor 11 are mounted on the base 10. Spindle motor 1
1, an optical disk is chucked via a clamper (not shown). The laser coupler 13 is composed of a laser diode that emits a light beam, an optical system that guides the emitted light beam onto an optical disc, an optical sensor that converts reflected light from the optical disc into an electric signal, and the like.
The optical pickup 12 reads out the data from the pit train engraved on the track 14 of the optical disc by the laser coupler 13.

FIG. 5 is an explanatory view of the tracking servo operation. When the optical disk is driven to rotate, the track locus 14
When the optical disk has eccentricity, the eccentricity causes the optical disk to swing in the direction of arrow D. When the track shake occurs, the bobbin 2 is moved to the arrow E so that the laser beam emitted by the laser coupler 13 scans the track 14.
It is necessary to move in the direction of and follow. The tracking servo operation, which is the following operation, is performed by the inductive force of the magnetic field generated by the tracking coil 15 and the magnet 16 that are adhesively fixed on the bobbin 2. In order to perform this tracking servo operation, a signal indicating an error in the tracking direction, that is, a tracking error signal is required.

A method called a three-beam method will be described with reference to FIG. 6 as a method of generating a tracking error signal. As shown in FIG. 6A, a main beam 17 for reading a signal recorded on an optical disk and sub-beams 18 and 19 for generating a tracking error signal are tangential to the main beam 17 in the track 14 direction. They are arranged symmetrically in the front-back direction. And the secondary beams 18, 1
The reflected light of 9 is the sensor 20 and the sensor 2 shown in FIG.
The tracking error signal is obtained by calculating the difference (= E−F) between the electric signals E and F obtained by converting the electric signals E and F by 1.

FIG. 7 shows the waveform of the tracking error signal at each position on the track. FIG. 7B shows the main beam 1.
7 is right above the pit train and shows the state of following the track. When the main beam 17 is directly above the pit train, the diffraction due to the pit trains of the two sub-beams 18 and 19 becomes balanced (E = F), and the tracking error signal at this time is shown in FIG. It becomes zero as indicated by the symbol (b). Further, in FIGS. 7A and 7C, since the diffraction due to the pit rows of the two sub beams becomes unbalanced (E> F or E <F), the tracking error signal at this time is as shown in FIG.
As shown by the reference sign (a) or the reference sign (c) in (d), it has both positive and negative polarities.

However, FIG. 7 (d) shows an ideal tracking error signal waveform, and the actual tracking error signal waveform has a variation in the light amount of the two sub-beams 18 and 19 and the sensitivity of the sensors 20 and 21. Due to the variation, the tracking error signal at the position of FIG. 7 (b) does not become zero as shown by the symbol (b) in FIG. 7 (e), but includes the DC offset ODC. Performing the tracking servo control based on the tracking error signal including the DC offset ODC is not preferable because the light beam follows at a position deviated from just above the track. Therefore, it is necessary to remove the DC offset ODC in advance.

Next, the operation of the conventional automatic DC offset adjustment will be described with reference to FIGS.
First, when the optical disk is rotated by the spindle motor 11 in a state where the light beam is focused on the pit row on the optical disk by the focus servo, the eccentricity of the optical disk causes the sub-beam to cross the track.
The error signal of tracking output from FIG.
It becomes a continuous sine wave as shown in (a). Then, the DC offset detector 23 composed of an LPF (Low Pass Filter) such as a capacitor and a resistor extracts a DC offset of a sine wave and converts a DC offset signal as shown in FIG. 9B into an A / D converter. To 24.

An offset measuring device 27 including an A / D converter 24, a microcomputer 25, and a D / A converter 26 measures the signal level of a DC offset signal input to the A / D converter 24, The microcomputer 25 controls the D / A converter 26 so that the tracking error signal becomes zero according to the signal level of the DC offset signal (= tracking positional deviation) when the tracking error signal should be zero. The instruction signal is output to the resistance changer 28.

As a result, for example, the resistance changer 28, which is an electronic volume whose resistance value changes according to the input, changes according to the change of the signal level of the instruction signal = V0 → V1.
As shown in FIG. 10A, the resistance value changes from R0 to R1, and the DC offset of the tracking error signal changes as shown in FIG. In this way, it is possible to automatically obtain the tracking error signal from which the DC offset of the tracking error signal has been removed.

Further, since the track 14 is drawn in a spiral shape on the optical disk, if the track 14 is made to follow the track 14 for a long time, the target track moves to the outer peripheral side and the bobbin 2
Will deviate from the range that can be followed. When the carriage 4 moves beyond the range that can be followed in this way, the carriage 4 moves in the direction of the arrow F, so that the track 14 is included in the range that can be followed by the bobbin 2 again, and data can be continuously read. Of.

In this case, the carriage 4 operates so that the position error signal PE, which is the relative position between the bobbin 2 and the carriage 4, becomes sufficiently small. For example, as shown in FIG. 11, the position error signal PE is detected using the position sensor 6 and the light shielding plate 29 fixed to the bobbin 2, and the light shielding amount is adjusted to a predetermined amount.

Next, the structure and operation of the tracking servo controller will be described with reference to FIG.

The tracking servo is a tracking servo loop for controlling the bobbin 2 in the tracking direction,
The carriage servo loop is configured to suppress a position error corresponding to the position error signal PE, and the following operation is performed in a steady state.

First, in the tracking servo loop, the tracking controller 30 composed of a filter or the like performs a filtering process based on the tracking error signal TE from which the offset has been removed, and outputs the drive signal D1.

The drive amplifier 3 is responsive to the drive signal D1.
At 1, the drive current of the tracking coil is generated, and the tracking error signal TE operates so as to be zero.

Next, in the carriage servo loop, the carriage controller 32 composed of a filter or the like filters the position error signal PE and outputs a drive signal D2. Then, in accordance with the drive signal D2, the carriage drive amplifier 33 generates a drive current for the carriage coil, and controls so that the position error signal PE becomes zero.

[0023]

By the way, conventionally, as the tracking error signal TE, a sine wave signal obtained because the sub beam crosses the track due to the eccentricity of the optical disk when the optical disk for tracking is rotated is used. Since the frequency of the wave signal is as low as several tens to several hundreds Hz, the cutoff frequency of the LPF is set to several tens Hz in order to obtain the direct current offset by the direct current offset detector 23 including the LPF including the capacitor and the resistor.
It was necessary to set the following.

Therefore, the D / A in the offset measuring device 27
After changing the resistance value of the resistance changer 28 by the instruction signal from the converter 26, the A / D converter 2 is changed by the time constant of the LPF.
4, it was necessary to wait for the DC offset of the tracking error signal to be captured again.

As a result, there is a problem that it takes a long time to automatically adjust the DC offset.

Also, with the pickup standing upright,
That is, in the case of no control, there is a problem that the DC offset cannot be automatically adjusted in a state where the center of the carriage 4 and the center of the objective lens 1 are displaced by the suspension spring 3 being deflected by the weight of the objective lens 1 and the bobbin 2. .

More specifically, the position of the bobbin 2 in the horizontal state (the center of the carriage 4 and the objective lens 1 shown in FIG. 12A).
12B, the position of the bobbin 2 is lowered due to its own weight (the center of the carriage 4 is deviated from the center of the objective lens 1), so that an accurate tracking error signal can be obtained. There was a problem that the automatic adjustment could not be performed accurately because it exceeded.

Therefore, a first object of the present invention is to provide an optical disk device capable of automatically adjusting a DC offset at high speed. A second object of the present invention is to provide an optical disk device capable of automatically adjusting the DC offset at high speed regardless of the installed state of the pickup.

[0029]

In order to solve the above-mentioned first problem, the invention according to claim 1 holds a bobbin which holds a means for condensing a laser beam and can be finely moved in a radial direction and a normal direction of an optical disk. An optical disk device having a carriage capable of roughly moving the bobbin in the radial direction and a servo unit for scanning a spot of a laser beam focused by the focusing unit on a target track. A tracking error signal generating means for generating a tracking error signal indicating a tracking state with respect to a track; and a DC offset detecting means having a low pass filter for detecting a DC offset of the tracking error signal and outputting a DC offset signal, A DC offset that cancels the DC offset of the tracking error signal based on the DC offset signal. And removal means, the fine movement of the bobbin in a substantially radial direction of the optical disk, and is configured by including a reciprocating fine motion means for reciprocating, a.

In order to solve the second problem, a second aspect
According to the invention, a bobbin that holds a condensing means for a laser beam and can be finely moved in a radial direction and a normal direction of an optical disc, a carriage that can roughly move the bobbin in the radial direction, and the condensing means collects the light. And a relative position detecting means for outputting a relative position error signal indicating a relative position between the bobbin and the carriage, the optical disc device having servo means for scanning a spot of the generated laser light on a target track. A relative position control means for controlling the relative position of the bobbin and the carriage to be substantially constant based on an error signal, a tracking error signal generation means for generating a tracking error signal indicating a tracking state of the light spot with respect to a track, and a low pass filter. DC for detecting a DC offset of the tracking error signal and outputting a DC offset signal A offset detecting means, a DC offset removing means for canceling a DC offset of the tracking error signal based on the DC offset signal, and a reciprocating fine moving means for finely moving and reciprocating the bobbin in a substantially radial direction of the optical disc. Be prepared and configured.

[0031]

According to the first aspect of the invention, the tracking error signal generating means generates a tracking error signal indicating the tracking state of the light spot with respect to the track and outputs it to the DC offset detecting means.

In parallel with this, the reciprocating fine moving means finely moves and reciprocates the bobbin substantially in the radial direction of the optical disk to raise the frequency of the tracking error signal.

The DC offset detecting means detects the DC offset of the tracking error signal having the increased frequency by the low pass filter and outputs the DC offset signal to the DC offset removing means.

As a result, the DC offset removing means cancels the DC offset of the tracking error signal based on the DC offset signal.

Therefore, the DC offset is removed based on the tracking error signal whose frequency is increased by the reciprocating fine movement means, and the cutoff frequency of the low pass filter is increased, that is, the time constant of the low pass filter is decreased. Therefore, the DC offset can be canceled at high speed.

According to the second aspect of the invention, the relative position detecting means outputs the relative position error signal indicating the relative position of the bobbin and the carriage.

The relative position control means controls the relative position of the bobbin and the carriage to be substantially constant based on the relative position error signal.

On the other hand, the tracking error signal generating means is
A tracking error signal indicating the tracking state of the light spot with respect to the track is generated and output to the DC offset detecting means.

In parallel with this, the reciprocating fine movement means finely moves and reciprocates the bobbin substantially in the radial direction of the optical disk to raise the frequency of the tracking error signal.

The DC offset detecting means detects the DC offset of the tracking error signal having the increased frequency by the low pass filter and outputs the DC offset signal to the DC offset removing means.

As a result, the DC offset removing means cancels the DC offset of the tracking error signal based on the DC offset signal.

Therefore, with the relative position control means controlling the relative position of the bobbin and the carriage to be substantially constant, the reciprocating fine movement means removes the DC offset on the basis of the tracking error signal having a high frequency. The cutoff frequency of the low-pass filter is high, that is, the time constant of the low-pass filter is small when the relative position of the carriage is kept almost constant regardless of the installation state (horizontal installation or vertical installation) of the optical disk device. Therefore, it is possible to reliably and quickly cancel the DC offset regardless of the installation state of the optical disk device.

[0043]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described with reference to the drawings.

(First Embodiment) FIG. 1 shows the configuration of an optical disk device according to the first embodiment of the present invention.

The optical disk device includes a spindle motor 11 for rotating an optical disk (not shown), an optical pickup 12 for reading recorded information from the optical disk rotationally driven by the spindle motor 11, and outputting a read signal through an optical coupler 13. A differential device 22 that outputs a tracking error signal TE based on a read signal, a DC offset detector 23 that detects a DC offset of the tracking error signal TE and outputs a DC offset signal, and a tracking based on the DC offset detection signal. While outputting the error cancel instruction signal so that the error becomes zero,
An offset measuring device 27 that outputs a fine movement control signal, a resistance changer 28 that is an electronic volume whose resistance value changes based on an error cancel instruction signal, a tracking error signal TE that is configured by a filter, and the like are removed. A tracking controller 30 that performs a filtering process based on the output signal and outputs a drive signal D1, and a drive amplifier 3 that generates a drive current for a tracking coil according to the drive signal D1.
1 and a position error signal PE composed of a filter, etc.
The carriage controller 32 that outputs a drive signal D2 by filtering based on the drive signal, the carriage drive amplifier 33 that generates a drive current for the carriage coil based on the drive signal D2, and the bobbin 2 based on the fine movement control signal FC. And a fine movement indicator 34 that outputs a fine movement instruction signal FD for finely moving back and forth in the radial direction to the drive amplifier 31.

The offset measuring unit 27 A / D-converts the DC offset signal and outputs it as DC offset data, and according to the input DC offset data, the state of tracking positional deviation is determined. A microcomputer 25 for outputting cancel instruction data so that the tracking error signal becomes zero, and a D / A converter 26 for D / A converting the input cancel instruction data and outputting a cancel instruction signal. Is configured.

Next, the operation will be described. First, the optical disc is rotated and driven by the spindle motor 11 in a state where the light beam is focused on the pit row on the optical disc (not shown) by the focus servo. At this time, the fine movement indicator 3
The reference numeral 4 outputs to the drive amplifier 31 a fine movement instruction signal FD for reciprocating the bobbin 2 in the radial direction for fine movement based on the fine movement control signal FC.

The drive amplifier 31 generates a drive current for the tracking coil according to the fine movement instruction signal FD, and the bobbin 2
Is slightly moved back and forth in the direction of symbol A in FIG. This reciprocating fine movement operation increases the speed at which the sub-beams 18 and 19 (see FIG. 6) cross the track as compared with the case where the reciprocating fine movement operation is not performed.
2B, the frequency becomes higher than that in the conventional example of FIG. 8A, and the DC offset detector 23 is provided to extract the DC offset of the tracking error signal TE. It is possible to set a high cutoff frequency of the LPF composed of a capacitor, a resistor and the like. Therefore, the time constant of the LPF can be reduced.

The DC offset detector 23 outputs a DC offset signal to the A / D converter 24 of the offset measuring unit 27 based on the detected DC offset.

As a result, the A / D of the offset measuring device 27
The converter 24 A / D converts the DC offset signal and outputs it to the microcomputer 25 as DC offset data.

The microcomputer 25 outputs the cancel instruction data to the D / A converter 26 so that the tracking error signal becomes zero according to the state of tracking positional deviation based on the input DC offset data.

The D / A converter 26 D / A converts the input cancel instruction data and outputs a cancel instruction signal to the resistance changer 28.

As a result, the resistance changer 28 changes its resistance value based on the cancel instruction signal so that the DC offset becomes zero.

As a result, it is possible to automatically obtain the tracking error signal from which the DC offset of the tracking error signal TE is removed. Further, as described above, the time constant of the LPF can be reduced by finely moving the bobbin back and forth, and the DC offset of the tracking error signal TE can be removed at high speed.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to the drawings.

FIG. 3 shows a block diagram of the optical disk device of the second embodiment. In FIG. 3, the same parts as those in the embodiment of FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

The second embodiment differs from the first embodiment in that
A relative position controller 35 for outputting a relative position control signal CCP for controlling the relative position of the bobbin 2 and the carriage 4 to a predetermined position based on the position error signal PE, a fine movement instruction signal FD and a relative position control signal CCP. An adder 36 that outputs a correction fine movement instruction signal FD1 for finely moving the bobbin 2 back and forth in the radial direction while maintaining the relative position between the bobbin 2 and the carriage 4 at a predetermined position by adding the drive amplifier 31, It is a point equipped with.

Next, the operation will be described. First, the optical disk is rotated by the spindle motor 11 in a state where the light beam is focused on the pit row on the optical disk (not shown) by the focus servo. At this time, the relative position controller 35
Is set so that the position error indicating the relative position between the bobbin 2 and the carriage 4 becomes zero, that is, the center position of the objective lens 1 held by the bobbin 2 and the center position of the carriage 4 become substantially equal (see FIG. )) The relative position control signal CCP for control is output to the adder 36.

Further, the fine movement indicator 34 outputs a fine movement instruction signal FD for reciprocating the bobbin 2 in the radial direction for fine movement.

As a result, the adder 35 adds the relative position control signal CCP and the fine movement instruction signal FD and outputs it as the corrected fine movement instruction signal FD1 to the drive amplifier 31.

The drive amplifier 31 generates a drive current for the tracking coil on the basis of the correction fine movement instruction signal FD1 from the adder 36, and the bobbin 2 is almost even when the pickup is placed upright as shown in FIG. 4 (a). A fine reciprocating motion can be performed around a position where the center of the objective lens 1 and the center position of the carriage 4 are substantially equal (corresponding to the reference position when horizontal).

By this reciprocating fine movement operation, the sub beams 18, 1
Since the speed at which 9 crosses the track becomes large, the tracking error signal TE changes as shown in FIG.
The frequency is higher than in the case of the conventional example of (a), and the cutoff frequency of the LPF formed by a capacitor, a resistor and the like provided in the DC offset detector 23 to extract the DC offset of the tracking error signal TE. Can be set higher. Therefore, the time constant of the LPF can be reduced.

Then, the DC offset detector 23 outputs a DC offset signal to the A / D converter 24 of the offset measuring device 27 based on the detected DC offset.

As a result, the A / D of the offset measuring device 27
The converter 24 A / D converts the DC offset signal and outputs it to the microcomputer 25 as DC offset data.

The microcomputer 25 outputs the cancel instruction data to the D / A converter 26 so that the tracking error signal becomes zero according to the state of tracking positional deviation based on the input DC offset data.

The D / A converter 26 D / A converts the input cancel instruction data and outputs a cancel instruction signal to the resistance changer 28.

As a result, the resistance changer 28 changes its resistance value based on the cancel instruction signal so that the DC offset becomes zero.

As a result, it is possible to automatically obtain the tracking error signal from which the DC offset of the tracking error signal TE is removed. Further, as described above, the time constant of the LPF can be reduced by finely moving the bobbin back and forth, and the DC offset of the tracking error signal TE can be removed at high speed.

Further, according to the second embodiment, the relative position of the bobbin and the carriage can be kept substantially constant regardless of the installed state of the optical pickup 12 (horizontal installation and vertical installation). Regardless of the installation state of 12, the DC offset can be canceled reliably and at high speed.

[0070]

According to the first aspect of the invention, the DC offset removing means removes the DC offset based on the tracking error signal whose frequency is increased by the reciprocating fine movement means, and the cutoff of the low pass filter. Since the frequency can be increased, that is, the time constant of the low pass filter can be reduced, the waiting time at the time of detecting the DC offset due to the time constant of the low pass filter can be reduced, and the DC offset can be canceled at high speed. It is possible to configure an optical disk device.

According to the second aspect of the present invention, the relative position control means controls the relative position of the bobbin and the carriage to be substantially constant based on the relative position error signal, and the DC offset removing means uses the reciprocating fine movement means to control the frequency. The DC offset is removed based on the tracking error signal that has increased, and the relative position of the bobbin and the carriage is kept almost constant regardless of the installation state (horizontal installation or vertical installation) of the optical disk device. Since the cutoff frequency of the low-pass filter can be increased, that is, the time constant of the low-pass filter can be reduced, the DC offset can be canceled reliably and at high speed regardless of the installation state of the optical disk device.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an optical disk device according to a first embodiment of the present invention.

FIG. 2A is a configuration diagram for explaining the operation of the optical disc apparatus according to the first embodiment of the present invention. FIG. 2B is a waveform diagram for explaining the operation of the optical disc apparatus according to the first embodiment of the present invention.

FIG. 3 is a configuration diagram of an optical disc according to a second embodiment of the present invention.

FIG. 4 is a configuration diagram of a conventional optical pickup.

FIG. 5 is a configuration diagram of a conventional optical pickup.

FIG. 6A is an operation explanatory view of a three-beam system of a conventional pickup, and FIG. 6B is a layout diagram of a three-beam system sensor of a conventional pickup.

FIG. 7 (a) is an operation explanatory view of a conventional pickup with a three-beam method. (B) is an operation explanatory view of a conventional pickup with a three-beam method. (C) is an operation explanatory view of a conventional pickup with a three-beam method. (E) Waveform diagram for explaining the operation of the conventional 3-beam system

FIG. 8 is a block diagram of a conventional optical disc.

9A is a waveform diagram for explaining an operation of a conventional optical disc device. FIG. 9B is a waveform diagram for explaining an operation of a conventional optical disc device.

10A is a waveform diagram for explaining the operation of the conventional optical disc device. FIG. 10B is a waveform diagram for explaining the operation of the conventional optical disc device.

FIG. 11 is an operation explanatory diagram of a conventional optical disc device.

FIG. 12 (a) is an operation explanatory diagram of a conventional optical disc device. (B) is an operation explanatory diagram of a conventional optical disc device.

[Explanation of symbols]

 1 Objective Lens 2 Bobbin 3 Suspension Spring 4 Carriage 6 Position Sensor 11 Spindle Motor 12 Optical Pickup 13 Laser Coupler 22 Differential Device 23 DC Offset Detector 24 A / D Converter 25 Microcomputer 26 D / A Converter 27 Offset Measuring Device 28 Resistance Changer 30 Tracking Controller 31 Drive Amplifier 32 Carriage Controller 33 Carriage Drive Amplifier 34 Fine Motion Indicator 35 Relative Position Controller 36 Adder

Claims (2)

[Claims] 1. A bobbin capable of finely moving a laser beam in a radial direction and a normal direction of an optical disk while holding a focusing means, a carriage capable of roughly moving the bobbin in the radial direction, and the focusing means. An optical disk apparatus having servo means for scanning a spot of a laser beam generated on a target track, the tracking error signal generating means for generating a tracking error signal indicating a tracking state of the light spot with respect to the track, and a low-pass filter. A direct current offset detecting means for detecting a direct current offset of the tracking error signal and outputting a direct current offset signal; and a direct current offset removing means for canceling the direct current offset of the tracking error signal based on the direct current offset signal, Finely reciprocating the bobbin in the radial direction of the optical disk Optical disk apparatus characterized by comprising a reciprocating fine motion means for. 2. A bobbin which holds a means for condensing a laser beam and can be finely moved in a radial direction and a normal direction of an optical disk, a carriage which can roughly move the bobbin in the radial direction, and a condensing means. An optical disk device having servo means for scanning a spot of a laser beam generated on a target track, the relative position detecting means outputting a relative position error signal indicating a relative position of the bobbin and the carriage,
Relative position control means for controlling the relative position of the bobbin and the carriage to be substantially constant based on the relative position error signal,
A DC offset detection which has a tracking error signal generating means for generating a tracking error signal indicating a tracking state of the light spot to a track and a low pass filter, detects a DC offset of the tracking error signal and outputs a DC offset signal. Means, and a DC offset removing means for canceling the DC offset of the tracking error signal based on the DC offset signal,
An optical disc device comprising: a reciprocating fine movement means for finely moving and reciprocating the bobbin in a substantially radial direction of the optical disc.