JPH08249687A - Tracking servosystem - Google Patents

Abstract

PURPOSE: To suppress the variations of every optical disk by correcting the reset of a tracking error signal by a correction means and removing the offset of the tracking error signal in response to a low-region driving component in which the gain of the low-region driving component extracted by a low-region means is adjusted. CONSTITUTION: A tracking error signal TE from a tracking error detecting means is inputted to the input terminal (a) of a selector 13 through a subtractor 11 constituting an offset correction means and a phase compensating device 12 for tracking servo. When the selector 13 selects the terminal (a), the output signal of the compensating device 12 is transferred to a power amplifier 14 by the selector 13 to drive a tracking actuator 15, thereby driving an objective lens 10 perpendicularly to the track of a disk. A low-region component of a driving signal is extracted by a low-pass filter 16, a gain is adjusted by a variable gain extracting means 17. an offset (j) is added thereto by an offset applying means 18 and it is subtracted from the signal TE by the subtractor 11 to correct the offset.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tracking servo device for an optical disk device.

[0002]

2. Description of the Related Art Generally, an optical disk device causes a light beam for irradiating the optical disk to follow a track of the optical disk by a tracking servo device. Conventionally, as a tracking servo device, a tracking servo sensor system of a push-pull method is used, in which diffracted light from an optical disc is detected by a two-division photodetector, and a difference between detection signals of respective divided portions of the two-division photodetector is detected. In addition to obtaining the tracking error signal, the displacement of the objective lens is detected by a lens displacement sensor, and the offset of the tracking error signal is corrected by combining the detection signal of this lens displacement sensor and the tracking error signal. Is disclosed in Japanese Patent Laid-Open No. 3-78121.

Japanese Patent Publication No. 36856/1993 discloses that
In order to reduce the offset of the tracking signal caused by tracking of the objective lens, a tracking servo device is described in which the entire pickup is moved to reduce the tracking amount of the objective lens. Further, U.S. Pat. No. 4,672,03 describes a tracking servo device that reduces the amount of displacement of an objective lens by driving the entire pickup with an output signal of a lens displacement sensor that detects the position of the objective lens. There is.

[0004]

DISCLOSURE OF THE INVENTION Problem to be Solved by the Invention
As described in Japanese Patent No. 21, the tracking error detection method of the push-pull method causes an offset in the tracking error signal when the objective lens is displaced from the reference position following the eccentricity of the optical disk or the like. Since the tracking servo device drives the objective lens so that the tracking error signal becomes 0, the tracking error signal with an offset causes the objective lens to follow the track at a position deviated from the track center of the optical disc, and Cause deterioration.

The above three tracking servo systems for avoiding this problem have the following drawbacks. In the tracking servo device described in JP-A-3-78121, the offset amount of the tracking error signal with respect to the displacement of the objective lens varies depending on the diffraction pattern of the light beam by the track on the optical disc. That is, the offset amount of the tracking error signal varies depending on the manufacturing variations of the optical disc and the optical pickup. Further, since the lens displacement sensor is attached, the cost is increased. Further, the relationship between the displacement amount of the objective lens and the detection signal of the lens displacement sensor varies from device to device due to variations in mounting of the lens displacement sensor. Therefore, even if the offset of the tracking error signal is corrected by the detection signal of the lens displacement sensor, the offset of the tracking error signal different for each optical disc or device remains.

In the tracking servo device described in Japanese Patent Publication No. 5-36856 and US Pat. No. 462703, the tracking error signal itself is not subjected to any special correction, and an objective lens is mounted instead. By moving the entire optical pickup, the amount of displacement of the objective lens is reduced. However, in order to suppress the displacement amount of the objective lens to be small so that the offset of the tracking error signal becomes sufficiently small, it is necessary to considerably increase the drive amount of the entire optical pickup.

For example, in a general optical disc, 100 μ
The eccentricity is about m, while the allowable displacement amount of the objective lens is about 20 μm so that the offset of the tracking error signal becomes sufficiently small. Therefore, it is necessary to perform eccentricity tracking of 80 μm for the entire optical pickup. A large amount of electric power is required to drive the entire optical pickup, and a motor for driving the entire optical pickup has a large volume. Further, a precise movable mechanism (bearing or the like) is required to perform eccentricity tracking control of the entire optical pickup, resulting in high cost.

The present invention can eliminate the offset of the tracking error signal caused by the displacement of the light beam without using the lens displacement sensor, and can suppress the variation among the optical disk devices, and thus the allowable amount of the displacement of the light beam. It is an object of the present invention to provide a tracking servo device which can increase the drive amount of the optical pickup and can reduce the drive amount of the entire optical pickup, and can realize a precise and accurate tracking servo at low cost.

[0009]

In order to achieve the above object, the invention according to claim 1 has a light beam moving means for moving a light beam applied to an optical disc, and tracking is performed by diffracted light from the optical disc. In a tracking servo device for obtaining an error signal and driving the light beam moving means based on the tracking error signal to cause the light beam to follow the track of the optical disc, a low-frequency drive component of the light beam moving means is extracted. Low-frequency extraction means, gain adjustment means for adjusting the gain of the low-frequency drive component extracted by the low-frequency extraction means, and the tracking error signal according to the low-frequency drive component whose gain is adjusted by the gain adjustment means And an offset correction means for correcting the offset.

According to a second aspect of the present invention, in the tracking servo apparatus according to the first aspect, there is provided direct current adjusting means for applying a direct current component to the low frequency drive component whose gain is adjusted by the gain adjusting means, and the offset correction is performed. The means is for correcting the offset of the tracking error signal according to the low frequency drive component to which the direct current component is applied by the direct current adjusting means.

According to a third aspect of the present invention, in the tracking servo device according to the first aspect, a predetermined amount driving means for driving the light beam moving means by a predetermined amount by opening the loop of the tracking servo, and the tracking error signal An offset extraction means for extracting an offset component, and a low-frequency drive component to be adjusted by the gain adjustment means from the offset component extracted by the offset extraction means when the light beam moving means is driven by the predetermined amount drive means. And a gain determining means for determining a gain.

According to a fourth aspect of the present invention, in the tracking servo apparatus according to the second aspect, the tracking servo loop is opened to drive the light beam moving means by a plurality of predetermined amounts, and the tracking error. The offset extraction means for extracting the offset component of the signal, and the gain from the correspondence relationship between the plurality of offset components extracted by the offset extraction means when the light beam moving means is driven by the predetermined amount by the predetermined amount driving means It is provided with a gain direct current component determining means for determining the gain of the low frequency drive component to be adjusted by the adjusting means and the direct current component of the low frequency drive component to be applied by the direct current adjusting means.

According to a fifth aspect of the present invention, in the tracking servo device according to the fourth aspect, the gain determining means obtains the correspondence by a linear regression calculation.

According to a sixth aspect of the present invention, in the tracking servo apparatus according to the first aspect, the tracking servo loop is opened to drive the light beam moving means with a periodic signal, and the offset correction means. Offset extraction means for extracting the offset component of the tracking error signal after offset correction; and the offset component of the tracking error signal extracted by the offset extraction means when the light beam moving means is driven by the periodic driving means is minimum. The gain adjusting means determines the gain of the low-frequency drive component to be adjusted by the gain adjusting means.

According to a seventh aspect of the present invention, in the tracking servo device according to the second aspect, the loop of the tracking servo is opened to drive the light beam moving means with a periodic signal, and the offset correcting means. Offset extraction means for extracting the offset component of the tracking error signal after offset correction, and positive correction of the offset component of the tracking error signal extracted by the offset extraction means when the light beam moving means is driven by the periodic driving means. , The direct current component of the low-frequency drive component to be applied is determined by the direct current adjusting means so that the negative maximum values become substantially equal, and by the offset extracting means when the light beam moving means is driven by the periodic drive means. Offset component of extracted tracking error signal Positive, in which a negative gain DC component determining means the sum of the maximum value to determine the gain of the low frequency drive components to be adjusted by the gain adjustment means so as to minimize.

The invention according to claim 8 is the same as claim 1,
In the tracking servo device described in 3, 4, 5, 6 or 7, the low frequency band extracting means is a filter simulating the mechanical transfer characteristic of the light beam moving means.

[0017]

According to the first aspect of the invention, the low-frequency driving component of the light beam moving means is extracted by the low-frequency extracting means, and the gain of the low-frequency driving component extracted by the low-frequency extracting means is adjusted by the gain adjusting means. To be done. Then, the offset correction means corrects the offset of the tracking error signal according to the low-frequency drive component whose gain is adjusted by the gain adjustment means.

According to a second aspect of the present invention, in the tracking servo device according to the first aspect, the direct current adjusting means applies a direct current component to the low-frequency drive component whose gain is adjusted by the gain adjusting means, and the offset correcting means is direct current. The offset of the tracking error signal is corrected according to the low frequency drive component to which the direct current component is applied by the adjusting means.

According to a third aspect of the invention, in the tracking servo apparatus according to the first aspect, the predetermined amount driving means drives the light beam moving means by a predetermined amount by opening the tracking servo loop, and the offset extracting means causes the tracking error signal. The offset component of is extracted. The gain determining means determines the gain of the low-frequency drive component to be adjusted by the gain adjusting means from the offset component extracted by the offset extracting means when the light beam moving means is driven by the predetermined amount driving means.

According to a fourth aspect of the present invention, in the tracking servo apparatus according to the second aspect, the predetermined amount driving means drives the light beam moving means by a plurality of predetermined amounts by opening the tracking servo loop, and the offset extracting means performs tracking. The offset component of the error signal is extracted. And
The gain DC component determining means is a low-frequency drive to be adjusted by the gain adjusting means from the correspondence relationship of the plurality of offset components extracted by the offset extracting means when the light beam moving means is driven by the predetermined amount driving means by the plurality of predetermined amounts. The gain of the component and the DC component of the low frequency drive component to be applied are determined by the DC adjusting means.

According to a fifth aspect of the present invention, in the tracking servo device according to the fourth aspect, the gain determining means obtains the correspondence by a linear regression calculation.

According to a sixth aspect of the present invention, in the tracking servo device according to the first aspect, the periodic drive means drives the light beam moving means with the periodic signal by opening the tracking servo loop, and the offset extraction means performs the offset correction means. The offset component of the tracking error signal after the offset correction by is extracted. The gain determining means is a low-frequency drive component to be adjusted by the gain adjusting means so that the offset component of the tracking error signal extracted by the offset extracting means is minimized when the light beam moving means is driven by the periodic driving means. Determine the gain of.

According to a seventh aspect of the present invention, in the tracking servo apparatus according to the second aspect, the periodic driving means drives the light beam moving means with the periodic signal by opening the loop of the tracking servo, and the offset extracting means and the offset correcting means. The offset component of the tracking error signal after the offset correction by is extracted. The gain direct current component determining means adjusts direct current so that the positive and negative maximum values of the offset component of the tracking error signal extracted by the offset extracting means when the light beam moving means is driven by the periodic drive means are substantially equal. Means for determining the DC component of the low-frequency drive component to be applied, and the positive and negative maximum values of the offset component of the tracking error signal extracted by the offset extraction means when the light beam moving means is driven by the periodic drive means. The gain of the low-frequency drive component to be adjusted by the gain adjusting means is determined so that the sum becomes the minimum.

According to the invention described in claim 8, claims 1, 2,
In the tracking servo device described in 3, 4, 5, 6 or 7, the low band extraction means, which is a filter simulating the mechanical transfer characteristics of the light beam movement means, extracts the low frequency drive component of the light beam movement means.

[0025]

1 shows a first embodiment of the present invention, and FIG. 2 shows an example of an algorithm of a controller in the first embodiment. The first embodiment is an embodiment of the invention described in claims 1-5. The TE shown in FIG.
This is a tracking error signal detected from the diffracted light from the optical disk by the push-pull method by a known tracking error detection means. This tracking error detecting means is, for example, in an optical disc device, a light beam is emitted from a light source onto the optical disc through the objective lens 10, and the reflected diffracted light is divided by a two-part photodetector through an optical system including the objective lens 10. Then, the difference between the detection signals of the respective divided portions of the two-divided photodetector is calculated by the arithmetic circuit to obtain the tracking error signal.

The tracking error signal TE from the tracking error detecting means passes through the subtracter 11 constituting the offset correcting means, the phase compensator 12 for tracking servo, and is input to the input terminal a of the selector 13. . When the selector 13 selects the input terminal a, the output signal of the phase compensator 12 is sent to and amplified by the power amplifier 14 by the selector 13, and the tracking actuator 15 as the light beam moving means outputs the output signal of the power amplifier 14. The objective lens 10 is driven in the direction orthogonal to the track of the optical disc. As a result, the objective lens 10 moves so that TE = 0 and tracking servo is performed, and the light beam follows the track of the optical disc.

The low-pass filter 16 as the low-pass extracting means extracts the low-pass component from the input signal of the power amplifier 14 (output signal of the selector 13) to extract the low-pass drive component of the drive signal of the tracking actuator 15. . Generally, in a range lower than several tens Hz, the objective lens 1 is proportional to the voltage applied to the tracking actuator 15.
Since the displacement of 0 occurs, the output signal of the low-pass filter 16 becomes a signal proportional to the displacement of the objective lens 10.

Since TE causes an offset proportional to the displacement of the objective lens 10, it should be possible to correct the TE offset with the output signal of the low-pass filter 16. In the present embodiment, the output signal of the low-pass filter 16 has its gain adjusted by the variable gain means 17 as the gain adjusting means, and the offset applying means 18 as the DC component determining means.
Offset J is added by
The output signal of the offset applying means 18 is subtracted from this.
The variable gain means 17 has a gain set by a coefficient K.

The offset component of TE is detected by the offset detecting means 19. The controller 20
The offset component OFS from the offset detection unit 19 is input, the gain setting value K and the offset J are output to the variable gain unit 17 and the offset application unit 18, and the voltage D is output to the input terminal b of the selector 13. Selector 1
3 is controlled by the controller 20, and the input terminals a,
The input signal of b is switched and output.

The controller 20 switches the selector 13 to the input terminal b side to open the tracking servo loop, and then applies the voltage D from the input terminal b of the selector 13 via the power amplifier 14 to the tracking actuator. The objective lens 10 is displaced by a predetermined amount over 15. Then, the controller 20 reads the offset component OFS from the offset detection means 19 at this time, and based on the relationship between the offset component OFS and the voltage D, the gain setting value K and the offset J are adjusted so that the offset of TE is appropriately corrected. To decide.

The gain setting value K and the offset J can be determined by an algorithm as shown in FIG. 2, for example. That is, the controller 20 switches the selector 13 to the input terminal b side in step 101 and applies the voltage D from the input terminal b of the selector 13 to the tracking actuator 15 via the power amplifier 14 to displace the objective lens 10 by a predetermined amount. . Then, the controller 20 sets the voltage D to − in the loop of steps 102 to 104.
The offset detection means 19 for the voltage D at each stage is sequentially switched (switched) in five stages of 2, -1, 0, 1, 2.
The offset component OFS from is read.

Here, D is not limited to a voltage, and if the selector 13 and the power amplifier 14 and the like have a circuit configuration that handles digital values, D can also be a digital value. All the components except the objective lens 10 and the tracking actuator 15 can be digital circuits. Hereinafter, D is a voltage and its unit is V (volt).

The OFS measured for each D is shown in FIG.
The relationship is as shown by ◯. The controller 20
In step 105, the relation between each D and OFS is approximated by a known linear regression calculation with a straight line OFS = K · D + J to obtain K, J.
Is calculated, and in step 106, K and J are set in the variable gain means 17 and the offset applying means 18, and step 1
By switching the selector 13 to the input terminal a side at 07, the low frequency component of the input signal of the power amplifier 14, that is, the TE offset with respect to the displacement of the objective lens 10 is appropriately corrected.

As described above, the first embodiment is an embodiment of the invention described in claim 1, and has the tracking actuator 15 as the light beam moving means for moving the light beam applied to the optical disk, A tracking error signal is obtained from the diffracted light from the tracking error detecting means, and the light beam moving means 15 is driven based on the tracking error signal to cause the light beam to follow the track of the optical disk. The low-pass filter 16 as a low-pass extracting means for extracting the low-pass drive component of the means 15, and the variable gain means 17 as a gain adjusting means for adjusting the gain of the low-pass drive component extracted by the low-pass extracting means 16. When,
Since the gain adjusting means 17 is provided with the subtracter 11 as the offset correcting means for correcting the offset of the tracking error signal according to the low-frequency drive component whose gain is adjusted, the tracking error signal generated by the displacement of the light beam is provided. The offset can be removed, and the offset variation of the tracking error signal for each device can be canceled. Therefore, the offset of the tracking error signal can be accurately corrected, the allowable amount of light beam displacement can be increased, and it is not necessary to make the entire optical pickup follow the eccentricity of the optical disk. The amount can be made small, and the device can be made at low cost and in a small size. Further, since the correction amount is extracted from the low-frequency drive component of the light beam moving means, the lens displacement sensor is not necessary, and the cost can be reduced.

The first embodiment is an embodiment of the invention as set forth in claim 2, and is an offset as a DC adjusting means for applying a DC component to the low frequency drive component whose gain is adjusted by the gain adjusting means 17. Since the offset correction means 11 is provided with the application means 18 and corrects the offset of the tracking error signal in accordance with the low-frequency drive component to which the direct current component is applied by the direct current adjustment means 18, the optical or mechanical assembly error or the electrical error is generated. It is possible to cancel the offset variation of the tracking error signal caused by the large offset.

The first embodiment is an embodiment of the present invention as set forth in claim 3, wherein the tracking servo loop is opened to drive the light beam moving means 15 by a predetermined amount and a selector 13 as a predetermined amount driving means. The controller 20, the offset detection means 19 as the offset extraction means for extracting the offset component of the tracking error signal, and the offset extraction means 19 when the light beam moving means 15 is driven by the predetermined amount driving means 13, 20. Since the controller 20 is provided as a gain determining means for determining the gain of the low-frequency drive component to be adjusted by the gain adjusting means 17 from the offset component, the offset of the tracking error signal is corrected more accurately than the invention according to claim 1. The tracking error signal for each optical disc can be turned off. You can cancel the variation of Tsu door.

The first embodiment is an embodiment of the invention described in claim 4, wherein the tracking servo loop is opened to drive the light beam moving means 15 by a plurality of predetermined amounts as a predetermined amount driving means. 13 and controller 20
And an offset detecting means 19 as an offset extracting means for extracting an offset component of the tracking error signal.
And the low range to be adjusted by the gain adjusting means 17 from the correspondence relationship of the plurality of offset components extracted by the offset extracting means 19 when the light beam moving means 15 is driven by the predetermined amount driving means 13, 20 by a plurality of predetermined amounts. The tracking error signal is provided more accurately than the invention according to claim 2 since the controller 20 is provided as a gain direct current component determining means for determining the direct current component of the low frequency drive component to be applied by the drive component gain and direct current adjusting means 18. The offset of can be corrected.

Further, the first embodiment is an embodiment of the invention described in claim 5, and the controller 20 as the gain DC component determining means obtains the correspondence by the first-order regression calculation, so that the measurement variation is canceled. You can
The offset of the tracking error signal can be corrected more accurately.

In the first embodiment, D is divided into five stages, but the number of stages may be set to any number as required. Further, the offset J and the offset applying means 1
8 is not necessary when the optical system and the circuit system are made so that OFS≈0 when D = 0. In this case, precision is required for the optical system and the circuit system, but the algorithm for determining K is simpler than that shown in FIG. For example, D is 1
The controller 20 can set K = OFS / D from the OFS measured at D.

The variable gain means 17 and the offset applying means 18 may be semi-fixed volumes, the offset detecting means 19 may be a jig, and the algorithm of the controller 20 may be implemented in the manufacturing process. That is, as the apparatus, the offset detection means 19 and the controller 20 are eliminated and the variable gain means 17 and the offset application means 18 are eliminated.
Is a semi-fixed volume, D is given by a jig, OFS is measured, and the set value of the volume may be determined by the algorithm shown in FIG.

It is more preferable to use, as the low-pass filter 16, a filter whose mechanical transfer characteristics of the tracking actuator 15 and the objective lens 10 are approximated. For example, the tracking actuator 15 and the objective lens 1
If the system of 0 is a structure supported by a spring, and the mass of the movable part is m and the spring constant is k, the transfer function from the drive voltage of the tracking actuator 15 to the displacement of the objective lens 10 is G / (m -S + d-S + k) (1) G, d: constant S = jω (ω is frequency). If the filter 16 has a characteristic of ω ₀ ² / (S ² + 2ζ · ω ₀ · S + ω ₀ ² ) (2) ζ: constant ω ₀ ² = k / m, the drive voltage of the tracking actuator 15 The transfer function up to the displacement of the objective lens 10 is equivalent to the equation (1) only with a difference of a constant multiple. (2)
The formula has the characteristics shown in FIG.

The second embodiment of the present invention is an embodiment of the invention according to claim 8 in which such a filter is used as the low-pass filter 16 in the first embodiment. In the second embodiment, the voltage corresponding to the displacement of the objective lens 10 can be more accurately estimated from the voltage applied from the previous stage of the power amplifier 14, so that more accurate offset correction of the tracking error signal can be performed. As described above, the second embodiment is an embodiment of the invention described in claim 8, and the low-frequency extraction means 16 is a filter imitating the mechanical transfer characteristic of the light beam moving means 15, so that the low-frequency extraction is performed. The extraction result of the means 16 more accurately reflects the light beam movement amount, and more accurate offset correction of the tracking error signal can be performed.

FIG. 5 shows a third embodiment of the present invention, and FIG. 6 shows an example of a controller algorithm in the third embodiment. The third embodiment is an embodiment of the invention described in claims 6 and 7. In the third embodiment, tracking error detecting means, subtractor 21, phase compensator 22, selector 2
3, power amplifier 24, tracking actuator 2
5, the objective lens 26, the low-pass filter 27, the variable gain means 28, and the offset applying means 29 are the tracking error detecting means, the subtractor 11, the phase compensator 12, the selector 13, the power amplifier 14, and the tracking in the first embodiment. Actuator 15, objective lens 10, low-pass filter 16, variable gain means 17, offset applying means 1
Same as 8.

In the third embodiment, the sine wave generator 30 is input to the input terminal b of the selector 23, and the offset detector 31 refers to the output signal of the subtractor 21 to detect its offset component. That is, the offset detector 31 refers to the tracking error signal TE 'after the offset correction by the subtractor 21 to detect the offset component.
Offset detection result OFS of this offset detector 31
Is the positive and negative peak detector 32, and the positive and negative peaks P,
N is detected.

The controller 33 adjusts J and K by an algorithm as shown in FIG. That is, the controller 33 sets the selector 23 to the input terminal b in step 201.
To the power amplifier 2 by switching the sine wave (sine wave) from the sine wave generator 30 to the input terminal b of the selector 23.
4 to the tracking actuator 25, and the objective lens 26 moves to the tracking actuator 15
Driven by the optical disc to be displaced in a sine wave shape in a direction orthogonal to the track of the optical disc.

If the sine wave from the sine wave generator 30 has a frequency equal to or lower than the cutoff frequency of the low pass filter 27, it is input to the power amplifier 24 at the output side of the low pass filter 27. The sine wave appears as it is. The displacement of the objective lens 26 causes a sinusoidal offset in TE, the output signal of the low-pass filter 27 is adjusted in gain by the coefficient K by the variable gain means 28, and the offset J is added by the offset applying means 29. The subtracter 21 subtracts the output signal of the offset applying means 29 from TE, and the offset of TE ′ from this subtractor 21 should be zero. However, if K and J have already become appropriate values. Generally, the offset of TE 'does not become 0 at this point due to various variations.

In step 202, the controller 33 minimizes (P−N) so that P≈N, that is, the positive and negative peaks of the sinusoidal offset of the tracking error signal become substantially equal to each other. Adjust.
7A and 7B show how J is adjusted. This removes the offset DC component of the tracking error signal.

Next, the controller 33 proceeds to step 20.
In step 3, K is adjusted so that (P + N) is minimized. This is performed so that the offset amplitude of the tracking error signal becomes small. FIG. 7C shows how the K is adjusted. With this, proper K and J are determined, and the low frequency component of the input signal of the power amplifier 24, that is, the objective lens 26
The offset of the tracking error signal with respect to the voltage corresponding to the displacement of is corrected. After that, the controller 33 switches the selector 23 to the input terminal a side in step 204.

The third embodiment is an embodiment of the invention described in claim 6, wherein a sine wave generator as a periodic drive means for driving the light beam moving means 25 with a periodic signal by opening the tracking servo loop. 30, an offset extraction unit 31 for extracting the offset component of the tracking error signal TE ′ after the offset correction by the offset correction unit 21, and the light beam moving unit 2 by the cycle drive unit 30.
5 is driven, the positive / negative peak as a gain determining means for determining the gain of the low-frequency drive component to be adjusted by the gain adjusting means 28 so that the offset component of the tracking error signal extracted by the offset extracting means 31 is minimized. Since the detector 32 and the controller 33 are provided, the gain of the low-frequency drive component can be accurately adjusted with a simpler algorithm than the first embodiment.

The third embodiment is an embodiment of the invention described in claim 7, wherein the loop of the tracking servo is opened to drive the light beam moving means 25 with a periodic signal, and the offset correction. The offset extraction means 31 for extracting the offset component of the tracking error signal TE ′ after the offset correction by the means 21 and the tracking error signal extracted by the offset extraction means 31 when the light beam moving means 25 is driven by the cycle drive means 30. The DC component of the low-frequency drive component to be applied is determined by the offset applying unit 29 as the DC adjusting unit so that the positive and negative local maximum values of the offset component are substantially equal to each other, and the periodic drive unit 30 drives the light beam moving unit 25. The tracking error signal extracted by the offset extraction means 31 when the Positive and negative peak detector 32 as a gain DC component determining means for determining the gain of the low-frequency drive component to be adjusted by the gain adjusting means 28 so that the sum of the positive and negative maximum values of the offset components of the signal is minimized, and the controller. 33, it is possible to perform accurate offset adjustment of the tracking error signal with a simpler algorithm than the first embodiment.

Also in the third embodiment, all the constituent elements except the tracking actuator 25 and the objective lens 26 can be constructed as digital circuits. In addition, the sine wave generator 30 and the positive and negative peak detector 3
2. Variable gain means 28 using the controller 33 as a jig
Alternatively, the offset applying means 29 may be a semi-fixed volume, and the volume may be adjusted during the manufacturing process according to the algorithm of FIG.

Further, the low-pass filter 27 is replaced with the tracking actuator 25 and the objective lens 2 as shown in the formula (2).
It is more preferable to use a filter having a mechanical transfer characteristic that is approximately equivalent to the mechanical transfer characteristic of the system of FIG. In each of the above embodiments, the tracking servo is performed by moving the objective lens by the tracking actuator. However, the light beam moving means for moving the light beam is not limited to this, and a rotary mirror such as a galvanometer mirror may be minutely moved. It is also possible to use a device that rotates to change the light beam irradiation direction. Furthermore, the subtracters 11, 21
Variable gain means 17, 28 and offset applying means 1
The relationship between the positive and negative signs of the input and output signals of Nos. 8 and 29 is not limited to that in the above-described embodiment, and can be arbitrarily designed as long as the offset of the tracking error signal is reduced as a result.

[0053]

As described above, according to the first aspect of the present invention, there is provided the light beam moving means for moving the light beam applied to the optical disc, and the tracking error signal is obtained from the diffracted light from the optical disc. In a tracking servo device for driving the light beam moving means based on the tracking error signal to cause the light beam to follow the track of the optical disc, a low range extracting means for extracting a low range driving component of the light beam moving means, A gain adjusting means for adjusting the gain of the low-frequency driving component extracted by the low-frequency extracting means, and correcting the offset of the tracking error signal according to the low-frequency driving component whose gain is adjusted by the gain adjusting means. Since the offset correction means is provided, the offset of the tracking error signal generated by the displacement of the light beam is offset. Can be removed, it can be canceled variation in offset of the tracking error signal for each device. Therefore, the offset of the tracking error signal can be accurately corrected, the allowable amount of light beam displacement can be increased, and it is not necessary to make the entire optical pickup follow the eccentricity of the optical disk. The amount can be made small, and the device can be made at low cost and in a small size. Further, since the correction amount is extracted from the low-frequency drive component of the light beam moving means, the lens displacement sensor is not necessary, and the cost can be reduced.

According to a second aspect of the present invention, in the tracking servo device according to the first aspect, there is provided direct current adjusting means for applying a direct current component to the low-frequency drive component whose gain has been adjusted by the gain adjusting means. Since the offset correction means corrects the offset of the tracking error signal according to the low frequency drive component to which the direct current component is applied by the direct current adjustment means, a tracking error caused by an optical or mechanical assembly error or an electrical offset is generated. It is possible to cancel variations in signal offset.

According to a third aspect of the present invention, in the tracking servo apparatus according to the first aspect, the tracking servo loop is opened to drive the light beam moving means by a predetermined amount, and the tracking error. Offset extraction means for extracting an offset component of the signal, and low-frequency drive to be adjusted by the gain adjustment means from the offset component extracted by the offset extraction means when the light beam moving means is driven by the predetermined amount drive means. Since the gain determining means for determining the gain of the component is provided, the offset of the tracking error signal can be corrected more accurately than the invention according to claim 1, and the variation in the offset of the tracking error signal for each optical disk can be canceled. .

According to a fourth aspect of the present invention, in the tracking servo device according to the second aspect, the tracking servo loop is opened to drive the light beam moving means by a plurality of predetermined amounts, and a predetermined amount driving means. From the correspondence relationship between the offset extracting means for extracting the offset component of the tracking error signal and the plurality of offset components extracted by the offset extracting means when the light beam moving means is driven by the predetermined amount by the predetermined amount driving means. 3. The invention according to claim 2, further comprising: a gain direct current component determining means for determining a gain of the low frequency drive component to be adjusted by the gain adjusting means and a direct current component of the low frequency drive component to be applied by the direct current adjusting means. The offset of the tracking error signal can be corrected more accurately.

According to the fifth aspect of the present invention, in the tracking servo apparatus according to the fourth aspect, since the gain DC component determining means obtains the correspondence relationship by linear regression calculation, it is possible to cancel the measurement variation. The offset of the tracking error signal can be corrected more accurately.

According to a sixth aspect of the present invention, in the tracking servo apparatus according to the first aspect, the loop of the tracking servo is opened and the light beam moving means is driven by a periodic signal. Offset extraction means for extracting an offset component of the tracking error signal after offset correction by means, and an offset component of the tracking error signal extracted by the offset extraction means when the light beam moving means is driven by the periodic driving means. And a gain determining means for determining the gain of the low-frequency driving component to be adjusted by the gain adjusting means so as to minimize the value of the low-frequency driving component. Gain adjustment can be performed.

According to a seventh aspect of the present invention, in the tracking servo device according to the second aspect, the loop of the tracking servo is opened to drive the light beam moving means with a periodic signal, and the offset correction. Offset extraction means for extracting an offset component of the tracking error signal after offset correction by means, and an offset component of the tracking error signal extracted by the offset extraction means when the light beam moving means is driven by the periodic driving means. The DC component of the low-frequency drive component to be applied is determined by the DC adjusting means so that the positive and negative local maximum values of are equal to each other, and the offset extraction is performed when the light beam moving means is driven by the periodic driving means. Offset of the tracking error signal extracted by 3. The invention according to claim 1, further comprising: a gain direct current component determining means for determining a gain of a low-frequency drive component to be adjusted by the gain adjusting means so that a sum of positive and negative maximum values of the components is minimized. The gain of the low-frequency drive component can be accurately adjusted with a simpler algorithm.

According to the invention of claim 8, claim 1,
In the tracking servo device described in 2, 3, 4, 5, 6 or 7, since the low-frequency extraction means is a filter simulating the mechanical transfer characteristic of the light beam moving means, the extraction result of the low-frequency extraction means is The amount of movement of the light beam is reflected more accurately, and more accurate offset correction of the tracking error signal can be performed.

[Brief description of drawings]

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

FIG. 2 is a flowchart showing an algorithm example of a controller in the first embodiment.

FIG. 3 is a characteristic diagram for explaining the first embodiment.

FIG. 4 is a diagram showing a transfer function of a low pass filter according to a second embodiment of the present invention.

FIG. 5 is a block diagram showing a third embodiment of the present invention.

FIG. 6 is a flowchart showing an algorithm example of a controller in the third embodiment.

FIG. 7 is a waveform chart for explaining the third embodiment.

[Explanation of symbols]

 10,26 Objective lens 11,21 Subtractor 12,22 Phase compensator 13,23 Selector 14,24 Power amplifier 15,25 Tracking actuator 16,27 Low-pass filter 17,28 Variable gain means 18,29 Offset applying means 19, 31 offset detection means 20, 33 controller 30 sine wave generator 32 positive and negative peak detector

Claims (8)

[Claims] 1. A light beam moving means for moving a light beam applied to an optical disk, wherein a tracking error signal is obtained from diffracted light from the optical disk, and the light beam moving means is driven based on the tracking error signal. In a tracking servo device for causing a light beam to follow the track of the optical disc, a low-frequency driving component extracted by the low-frequency driving component of the light beam moving means, and a low-frequency driving component extracted by the low-frequency driving component. Tracking servo which comprises: a gain adjusting means for adjusting the gain of the tracking error signal; and an offset correcting means for correcting the offset of the tracking error signal according to the low-frequency drive component whose gain is adjusted by the gain adjusting means. apparatus. 2. The tracking servo device according to claim 1, further comprising a DC adjusting unit for applying a DC component to the low-frequency drive component whose gain is adjusted by the gain adjusting unit, wherein the offset correcting unit is the DC adjusting unit. The tracking servo device is characterized in that the offset of the tracking error signal is corrected according to the low frequency drive component to which the DC component is applied. 3. The tracking servo device according to claim 1, wherein a predetermined amount driving means for driving the light beam moving means by a predetermined amount by opening the loop of the tracking servo, and an offset for extracting an offset component of the tracking error signal. Gain determining means for determining the gain of the low frequency drive component to be adjusted by the gain adjusting means from the offset component extracted by the offset extracting means when the light beam moving means is driven by the extracting means and the predetermined amount driving means. And a tracking servo device. 4. The tracking servo device according to claim 2, wherein a predetermined amount driving unit for driving the light beam moving unit by a plurality of predetermined amounts by opening the tracking servo loop, and an offset component of the tracking error signal are extracted. The offset adjusting means and the gain adjusting means should be adjusted from the correspondence relationship between the plurality of offset components extracted by the offset extracting means when the light beam moving means is driven by the predetermined amount by the predetermined amount driving means. A tracking servo device comprising: a gain of a low frequency drive component and a gain direct current component determining means for determining a direct current component of the low frequency drive component to be applied by the direct current adjusting means. 5. The tracking servo device according to claim 4, wherein the gain DC component determining means obtains the correspondence by a linear regression calculation. 6. The tracking servo apparatus according to claim 1, wherein the tracking servo loop is opened to drive the light beam moving means with a periodic signal, and the tracking after the offset correction by the offset correction means. Offset extracting means for extracting an offset component of the error signal; and the gain so that the offset component of the tracking error signal extracted by the offset extracting means is minimized when the light beam moving means is driven by the periodic driving means. A tracking servo device comprising: a gain determining unit that determines a gain of a low-frequency drive component to be adjusted by the adjusting unit. 7. The tracking servo apparatus according to claim 2, wherein the tracking servo loop is opened to drive the light beam moving means with a periodic signal, and the tracking after the offset correction by the offset correction means. Offset extraction means for extracting the offset component of the error signal, and the positive and negative maximum values of the offset component of the tracking error signal extracted by the offset extraction means when the light beam moving means is driven by the periodic driving means. The tracking error signal extracted by the offset extracting means when the direct-current component of the low-frequency drive component to be applied is determined by the direct-current adjusting means so as to be substantially equal, and the light beam moving means is driven by the periodic driving means. Offset component of positive,
A tracking servo device, comprising: a gain direct current component determining means for determining a gain of a low-frequency drive component to be adjusted by the gain adjusting means so that a sum of negative maximum values is minimized. 8. The tracking servo device according to claim 1, 2, 3, 4, 5, 6 or 7, wherein the low frequency band extracting means is a filter simulating the mechanical transfer characteristic of the light beam moving means. Tracking servo device characterized by.