JP3355826B2 - Tracking error detection method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects a tracking error signal from a disk-shaped optical recording medium, particularly a disk-shaped optical recording medium in which guide grooves are formed along the track direction and preformat information and data are recorded. And a tracking error detecting method and apparatus.

[0002]

2. Description of the Related Art Conventionally, as a disk-shaped optical recording medium,
A read-only optical recording medium, a rewritable optical recording medium, and a magneto-optical recording medium rewritable by optical modulation or magnetic field modulation have been proposed.

In particular, the magneto-optical recording medium (hereinafter, simply referred to as a magneto-optical disk) is currently classified into a continuous groove format and a sample servo format.

[0004] Among these two formats,
In the former continuous groove format method, a preformat area and a data area are recorded for each sector (for example, 1360 bytes) along the track center.
In the preformat area, preformat information such as a parameter such as a sector mark, a verify check, and an ID indicating a sector position and preformat information such as an address are recorded as prepits. Guide grooves for tracking error detection are formed on both sides of the preformat area and the data area.

[0005] In recent years, a small magneto-optical disk having a diameter of, for example, 64 mm, in which the recording density of the magneto-optical disk is improved, has been used. In this small magneto-optical disk, in order to increase the data recording density, the guide grooves are formed in a meandering shape based on the preformat information, thereby eliminating the need for the prepits. That is, the guide groove is formed based on a signal obtained by synthesizing a reference signal having a predetermined frequency and the preformat information, and is formed in a meandering shape. Therefore, in this small-sized magneto-optical disk, data is stored at the center of the track, and preformat information is recorded in the meandering guide groove, so that the preformat area and the data area exist in the same space. It has become.
When a reproduction signal is obtained from this small-sized magneto-optical disk, it is performed by detecting the data recorded in the data area with the reproduction head. , The above data can be detected while detecting a tracking error signal.

In particular, in this small-sized magneto-optical disk, since the guide groove is formed in a meandering shape based on a composite signal of the reference signal and the preformat information, the tracking error signal taken out from the reproducing head is demodulated. Thereby, preformat information can be obtained. For this reason, in this small-sized magneto-optical disk, data detection and preformat information are performed simultaneously, and prepits for obtaining preformat information are unnecessary as described above.

Here, the tracking error signal is
It can be obtained by the push-pull method. Actually, for example, a DC offset is added to the push-pull signal due to a lens shift of the objective lens used in the pickup device or a disk skew. Therefore, it is necessary to remove the DC offset by a meandering frequency component of the small optical disk. is there.

For this reason, the applicant of the present application has disclosed in
A technique for removing the DC offset is disclosed in the specification and the drawings of Japanese Patent Publication No. 1680. For example, a tracking error detection device 30 having the circuit configuration shown in FIG. The light amount detection signal R from the right detector input from the input terminal 31 is supplied to an amplitude detector 32 for detecting the amplitude of the wobble component. The light amount detection signal L from the left detector input from the input terminal 33 is supplied to an amplitude detector 34 for detecting the amplitude of the wobble component. The amplitude detection signal W (R) of the right wobble component detected by the amplitude detector 32 and the amplitude detection signal W (L) of the left wobble component detected by the amplitude detector 34 are supplied to an operational amplifier 35. This operational amplifier 35 computes the difference W (R) -W (L) between W (R) and W (L), and outputs the computed output W (R) -W (L) to a coefficient multiplier 36. To supply.
The coefficient multiplier 36 multiplies the operation output W (R) -W (L) by a coefficient K and supplies the result to the operation amplifier 37. The operational amplifier 37 is also supplied with a push-pull signal RL (hereinafter referred to as PP) via an operational amplifier 38.
Therefore, the operational amplifier 37 outputs the corrected push-pull signal PP ′ from which the offset has been removed as PP ′ = PP−K {W (R) −W (L)} (1) Output from 39.

[0009]

In the above equation (1) showing the corrected push-pull signal PP ', the coefficient K is the groove shape, groove width, and groove depth of the small magneto-optical disk. However, it was not possible to cope with variations in wobble amplitude. This is because the tracking error signal including the offset component output from the operational amplifier 38 and the signal for canceling the offset component output from the coefficient multiplier 36 show different changes depending on the type of the disk. For this reason, the push-pull signal PP 'after the correction greatly differs depending on the disk, and the disk dependency is increased.

If the pickup makes a track jump or receives a shock from the outside, the push-pull signal PP itself may have a high frequency component as high as the frequency component of the wobble. W (R) -W (L) output by 35 greatly fluctuates, and a situation occurs in which the calculation as shown in the above equation (1) becomes unnecessary. For this reason, a control that does not require the calculation shown in the above equation (1) is required.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a corrected push-pull signal having a small disk dependency, a small fluctuation of a tracking error signal, and the following equation (1). It is an object of the present invention to provide a tracking control method and apparatus that does not require the control of the operation as shown.

[0012]

A tracking error detecting method according to the present invention detects a tracking error signal by removing an offset from a push-pull signal PP obtained from a disk-shaped recording medium having a guide groove formed in a meandering shape. In a tracking error detection method, the push-pull signal PP is reflected by the light amount R of reflected light from two directions sandwiching the guide groove.
And a push-pull signal detecting step of detecting as a difference RL between L and L, and light amounts R and L in two directions obtained from the reflected light.
From the amplitude W (R) of the meandering component in two directions sandwiching the guide groove
And W (L), and the difference W (R) between the amplitudes W (R) and W (L) of the meandering components in the two directions obtained in the first meandering amplitude detecting step. A meandering amplitude difference calculating step of calculating -W (L) and a second meandering amplitude detecting step of detecting the amplitude W (RL) of the meandering component of RL which is the push-pull signal PP. Then, W (R) -W (L) calculated in the meandering amplitude difference calculating step and the push-pull signal PP detected in the push-pull signal detecting step.
And W (R−R−R) detected in the second meandering amplitude detection step.
L) and the coefficient K,

[0013]

(Equation 7)

Using the coefficient K,

[0015]

(Equation 8)

Thus, the tracking error signal from which the offset has been removed is detected.

Further, the tracking error detection method according to the present invention includes a division step of dividing the push-pull signal PP by a total light amount signal Ig which is a sum R + L of the light amounts R and L in two directions obtained from the reflected light. Then, the PP / Ig calculated in the dividing step, the W (R) -W (L) calculated in the meandering amplitude difference calculating step, and the W (RL) detected in the second meandering amplitude detecting step. ) And the coefficient K,

[0018]

(Equation 9)

Using this coefficient K,

[0020]

(Equation 10)

Thus, the tracking error signal from which the offset has been removed may be detected.

A tracking error detecting apparatus according to the present invention detects a tracking error signal by removing an offset from a push-pull signal PP obtained from a disk-shaped recording medium having a guide groove formed in a meandering shape. A push-pull signal detecting means for detecting the push-pull signal PP as a difference RL between the light amounts R and L of reflected light from two directions sandwiching the guide groove, and a push-pull signal detecting means for detecting the push-pull signal PP in two directions obtained from the reflected light. The amplitudes W (R) and W of meandering components in two directions sandwiching the guide groove from the light amounts R and L
First meandering amplitude detecting means for detecting (L);
Meandering amplitude difference calculating means for calculating the difference W (R) -W (L) between the amplitudes W (R) and W (L) of the meandering components in two directions obtained by the meandering amplitude detecting means, and the push-pull signal Second meandering amplitude calculating means for calculating the amplitude W (RL) of the meandering component of RL which is PP, and the output W (R) -W (L) of the meandering amplitude difference calculating means are calculated by the second meandering means. And a coefficient multiplying means for multiplying the output of the dividing means by a coefficient K, and outputting the output of the coefficient multiplying means by the push-pull signal. Subtract from the output of the detection means.

In this case, the coefficient multiplying means outputs the output of the dividing means

[0024]

[Equation 11]

Is multiplied by a coefficient K represented by

Further, in the tracking error detecting device according to the present invention, the push-pull signal PP detected by the push-pull signal detecting means is a sum R + L of light amounts R and L in two directions obtained from the reflected light. A push-pull divider for dividing by the total light amount signal Ig signal may be provided, and the output of the coefficient multiplier may be subtracted from the output of the push-pull divider.

In this case, the coefficient multiplying means outputs the output of the dividing means

[0028]

(Equation 12)

Is multiplied by a coefficient K represented by

[0030]

The W (R) calculated in the meandering amplitude difference calculating step described above.
By dividing -W (L) by W (RL) detected in the second meandering amplitude detection step, the groove shape, groove depth, groove width, and meandering amplitude were varied. The change in the signal for canceling the offset caused by the difference between the discs can be suppressed, and the frequency of the push-pull signal (RL) can be reduced by the influence of the frequency component of the wobble to some extent. Even when the frequency becomes high, the fluctuation of the tracking error signal can be reduced.

Further, by dividing the push-pull signal PP by the total light amount signal Ig signal, the shape of the groove,
It is possible to suppress a change in a tracking error signal including an offset component caused by a difference between disks having different groove depths, groove widths, and meandering amplitudes.

[0032]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of a tracking error detecting apparatus and method according to the present invention.

This embodiment is a tracking error detecting apparatus to which the above-described tracking error detecting method and apparatus are applied, and has a small light beam having a guide groove (groove) formed in a meandering (wobble) shape based on preformat information. The present invention is applied to a small-sized magneto-optical disk recording / reproducing apparatus for recording / reproducing an information signal on / from a magnetic disk.

FIG. 1 shows the configuration of the tracking error detecting device.

In FIG. 1, the tracking error detection device receives light amount detection signals R and L from photodetectors PD1 and PD2, which are photodetectors arranged as shown in FIG. FIG 2 shows an arrangement of an optical system such as an objective lens 22 with respect to the return light L _B from the magneto-optical disc 21. As shown in FIGS. 3A and 3B, the two photodetectors PD1 and PD2 have their detection surfaces divided into four parts.
One of the two surfaces a and b, or h and g, is used for detecting the left light amount, and the other two surfaces c and d, or f and e are used for detecting the right light amount. Of course, here, the photodetector may be only one of them if there is another means for performing the focus control. The left detector is one side a
Only the left detector may be used for detecting the left light amount, and the right detector may be used for detecting the right light amount only on one side d.

The light amount detection signal R input from the input terminal 1
Is supplied to the amplitude detector 2. The light amount detection signal L input from the input terminal 3 is supplied to the amplitude detector 4. The amplitude detector 2 and the amplitude detector 4 detect the amplitude detection signals W (R) and W (R) of the meandering component in two directions sandwiching the guide groove from the light intensity detection signals R and L in two directions obtained from the return light. ) Is the first meandering amplitude detecting means. The amplitude detection signal W (R) of the right wobble component detected by the amplitude detector 2 and the amplitude detection signal W (L) of the left wobble component detected by the amplitude detector 4 are supplied to the operational amplifier 5. The operational amplifier 5 calculates a difference W (R) -W () between the W (R) supplied from the amplitude detector 2 and the W (L) supplied from the amplitude detector 4 as the first meandering amplitude detecting means. L) is meandering amplitude difference calculating means. This operational amplifier 5
The meandering amplitude difference W (R) -W (L) output from is supplied to the divider 6.

The light amount detection signal R and the light amount detection signal L of the return light from the two directions sandwiching the guide groove are also supplied to an operational amplifier 7 which is a push-pull signal detecting means. A push-pull signal RL as an output signal of the operational amplifier 7 is an amplitude detector 8 which is a second meandering amplitude detecting means for detecting an amplitude detection signal W (RL) of a wobble component of the push-pull signal. Supplied to This amplitude detection signal W (RL) is supplied to the divider 6. The divider 6 divides the W (R) -W (L) by the W (RL),

[0038]

(Equation 13)

Is output. The output signal of the divider 6 represented by the equation (2) is supplied to a coefficient multiplier 9. This coefficient multiplier 9

[0040]

[Equation 14]

Is output. The output signal of the coefficient multiplier 9 represented by the equation (3) is supplied to the operational amplifier 10.

The light quantity detection signal R and the light quantity detection signal L are also supplied to an operational amplifier 11, and the sum signal R + L
Is calculated. This sum signal R + L (hereinafter referred to as Ig) is supplied to the divider 12. Divider 12
Divides the push-pull signal RL (hereinafter referred to as PP) by the sum signal Ig,

[0043]

(Equation 15)

Is output. The output signal of the divider 12 represented by the equation (4) is supplied to the operational amplifier 10.
The operational amplifier 10 calculates the difference between the output signal of the operational amplifier 12 expressed by the above equation (3) and the output signal of the coefficient multiplier 9 expressed by the above equation (2),

[0045]

(Equation 16)

Is output from the output terminal 13 as a tracking error signal.

Here, the coefficient K used by the coefficient multiplier 9 for multiplication is

[0048]

[Equation 17]

Is as follows.

Here, the amplitude detectors 2, 4 and 8 correspond to FIG.
As shown in FIG. 2, the input signal supplied via the terminal 14 is band-limited by the band-pass filter 15 and the full-wave rectifier 16
Then, the signal is passed through a low-pass filter 17 to detect the amplitude of the input signal, and the detection result is output from a terminal 18.

The output signal R output from the operational amplifier 7 is
-L is a push-pull signal PP including a DC offset component caused by lens shift, disk skew, and the like. In general, the change in the DC component of the push-pull signal PP has a correlation with the amount of the spot irradiated on the photodetector. That is, a disc with a large amount of spot light irradiated on the photodetector has a large DC component of the push-pull signal PP. Therefore, in this embodiment, the sum signal Ig of the operational amplifier 11 is used to make the push-pull signal PP itself less dependent on the disk.
The divider 12 divides the push-pull signal PP.

On the other hand, the output signal W output from the operational amplifier 5
(R) -W (L), that is, the amplitude of the frequency component of the wobble has a correlation with the push-pull signal PP. That is, a disk with a large amplitude of the push-pull signal PP
| W (R) -W (L) | also increases. This output signal W
The reason that (R) -W (L) is divided by W (RL) by the divider 6 is that W (RL) is the wobble component of the push-pull signal itself, so that the correlation between the push-pull amplitude and the push-pull amplitude is obtained. This is because it is the same as the disk dependence of W (R) -W (L), and also to reduce the influence of the wobble groove beat.

The effects of this embodiment having the above configuration will be described below.

First, five small magneto-optical disks were prepared according to the groove width and groove depth as shown in the following table.

[0055]

[Table 1]

FIG. 5 shows a change characteristic of the offset amount with respect to the displacement of the lens in these small magneto-optical disks. In FIG. 5, the horizontal axis indicates the amount of movement of the lens in millimeter (mm) units, and the vertical axis indicates the difference in offset light amount. The offset varies greatly depending on the amount of movement of the lens. The offsets of the discs are A type (shown as (A) in the figure), B type (shown as (B) in the figure), C type (shown as (D) in the figure), and D type (shown in the figure). Medium (D).) And E type (indicated by (E) in the figure).

FIG. 6 shows a change characteristic of the total light amount (sum signal) Ig of one photodetector with respect to the displacement of the lens in these small magneto-optical disks. In FIG. 6, the horizontal axis represents the movement amount of the lens in millimeters (mm).
The total amount of light Ig is shown on the vertical axis. Ig does not vary greatly depending on the amount of movement of the lens.
Type, B type, C type, D type and E type increase. In this case, the type order of the disks is the same as that shown in FIG. This means that, as described above, the change in the DC offset of the push-pull signal is correlated with the amount of the spot irradiated on the photodetector.

FIG. 7 shows the amplitude change characteristic of the frequency component of the wobble with respect to the lens displacement in the small magneto-optical disk shown in Table 1 above. In FIG. 7, the horizontal axis indicates the movement amount of the lens, and the vertical axis indicates the amplitude difference between the frequency components of the wobble. The amplitude difference greatly varies depending on the amount of movement of the lens. Further, the amplitude difference becomes larger as the disc changes to E type, A type, B type, D type and C type. The order of the disc types is different from the order shown in FIG. This indicates that the change of the tracking error signal including the offset and the change of the signal for canceling the offset are different depending on the disc.

FIG. 8 shows the change characteristics of the wobble component W (RL) of the push-pull signal itself with respect to the lens displacement in these small magneto-optical disks. In FIG. 8, the horizontal axis indicates the amount of movement of the lens, and the vertical axis indicates W (RL). W (RL) does not vary greatly depending on the amount of movement of the lens.
It becomes larger as it changes to A type, B type, D type and C type. This is, as described above, the amplitude W (R) -W (L) of the frequency component of the wobble.
Means that there is a correlation with the push-pull signal PP.

Next, the DC offset from the push-pull signal of the D type small magneto-optical disk is calculated using the optimum coefficient K obtained when performing tracking control with the C type small magneto-optical disk shown in Table 1 above. The case of removal will be described with reference to FIGS.

FIG. 9 shows how the DC offset included in the push-pull signal obtained from the C-type disc changes with respect to the lens shift.

(I) is a push-pull signal in a state where the offset is not canceled. (Ii) is a coefficient K = PP
/ (W (R) -W (L)) is the push-pull signal PP 'in which the conventional DC component represented by the above equation (1) is canceled. (Iii) is the above (5)
The DC component obtained by the formula is a canceled push-pull signal. Note that (iv) will be described later.

Then, the coefficient K when (iii) is obtained
FIG. 10 shows a result obtained by reproducing the D-type disc by using the above method and obtaining a push-pull signal (iii). In FIG. 10, (i) is a push-pull signal in a state where the offset is not canceled when a D-type disc is reproduced. (Ii) is a coefficient K = P
When P / (W (R) -W (L)), it is a push-pull signal obtained by the above equation (1). (Iv) will be described later.

Comparing FIG. 9 with FIG. 10, it can be seen that the tracking error control device of the present embodiment can obtain a corrected push-pull signal with small disk dependence and can reduce the fluctuation of the tracking error signal.

The tracking error detection method and device according to the present invention are not limited to the configuration shown in FIG. 1, but may have the configuration shown in FIG. 11, for example.

The other embodiment shown in FIG. 11 differs from the embodiment shown in FIG. 1 in that the output signal of the coefficient multiplier 9 shown in the above equation (2) is changed as shown in the above equation (3). PP / I
The point is that the subtraction is not performed from g but only from the push-pull signal PP output from the operational amplifier 7. This subtraction is performed by the operational amplifier 10,

[0067]

(Equation 18)

The tracking error signal shown by the following is output from the output terminal 13. The tracking error signal shown in the equation (7) is shown as a characteristic (iv) in FIGS. 9 and 10, respectively. From this,
In other embodiments, push-pull offset cancellation with less disk dependency than before can be realized,
Further, it can be seen that the fluctuation of the tracking error signal can be reduced.

[0069]

The tracking error detecting method according to the present invention is a tracking error detecting method for detecting a tracking error signal by removing an offset from a push-pull signal PP obtained from a disk-shaped recording medium having a meandering guide groove. And the difference R-L between the light amounts R and L of the reflected light from two directions sandwiching the guide groove.
A push-pull signal detecting step of detecting as L, and a second step of detecting the amplitudes W (R) and W (L) of meandering components in two directions sandwiching the guide groove from the light amounts R and L in two directions obtained from the reflected light. 1 meandering amplitude detecting step, and the amplitude W (R) of the meandering component in two directions obtained in the first meandering amplitude detecting step.
Meandering amplitude difference calculating step of calculating a difference W (R) -W (L) between the push-pull signal PP and R-L.
A second meandering amplitude detecting step of detecting the amplitude W (RL) of the meandering component of L, and calculating the push-pull signal PP detected in the push-pull signal detecting step and the meandering amplitude difference calculating step. Using W (R) -W (L) thus obtained and W (RL) detected in the second meandering amplitude detection step, a coefficient K is calculated as follows:

[0070]

[Equation 19]

Using this coefficient K,

[0072]

(Equation 20)

Thus, since the tracking error signal from which the offset has been removed is detected, the fluctuation of the tracking error signal can be reduced, and the control of the calculation can be made unnecessary.

Here, there is a division step of dividing the push-pull signal PP by the total light quantity signal Ig which is the sum R + L of the light quantities R and L in two directions obtained from the reflected light. The coefficient K is calculated using PP / Ig, W (R) -W (L) calculated in the meandering amplitude difference calculating step, and W (RL) detected in the second meandering amplitude detecting step.
To

[0075]

(Equation 21)

Using this coefficient K,

[0077]

(Equation 22)

As a result, when the tracking error signal from which the offset has been removed is detected, it is possible to obtain a corrected push-pull signal having a small disk dependency.

The tracking error detecting device according to the present invention detects a tracking error signal by removing an offset from a push-pull signal PP obtained from a disk-shaped recording medium having a meandering guide groove. A push-pull signal detecting means for detecting the push-pull signal PP as a difference RL between the light amounts R and L of reflected light from two directions sandwiching the guide groove, and a push-pull signal detecting means for detecting the push-pull signal PP in two directions obtained from the reflected light. The amplitudes W (R) and W of meandering components in two directions sandwiching the guide groove from the light amounts R and L
First meandering amplitude detecting means for detecting (L);
Meandering amplitude difference calculating means for calculating the difference W (R) -W (L) between the amplitudes W (R) and W (L) of the meandering components in two directions obtained by the meandering amplitude detecting means, and the push-pull signal Second meandering amplitude calculating means for calculating the amplitude W (RL) of the meandering component of RL which is PP, and the output W (R) -W (L) of the meandering amplitude difference calculating means are calculated by the second meandering means. And a coefficient multiplying means for multiplying the output of the dividing means by a coefficient K, and outputting the output of the coefficient multiplying means by the push-pull signal. Since the subtraction is performed from the output of the detection means, the fluctuation of the tracking error signal can be reduced, and the control of the calculation can be omitted.

Here, a push-pull for dividing the push-pull signal PP detected by the push-pull signal detecting means by a total light amount signal Ig which is a sum R + L of the light amounts R and L in two directions obtained from the reflected light. Having division means,
By subtracting the output of the coefficient multiplying means from the output of the push-pull dividing means, it is possible to obtain a corrected push-pull signal having a small disk dependency.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a schematic configuration of a tracking error control device according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of a return optical system.

FIG. 3 is a diagram illustrating a photodetector.

FIG. 4 is a diagram showing a detailed configuration of an amplitude detector.

FIG. 5 is a diagram illustrating a change characteristic of an offset amount with respect to a shift of a lens.

FIG. 6 is a diagram illustrating a change characteristic of a total light amount (sum signal) Ig of one photodetector with respect to a shift of a lens.

FIG. 7 is a diagram illustrating an amplitude change characteristic of a frequency component of a wobble with respect to a displacement of a lens.

FIG. 8 is a diagram illustrating a change characteristic of a wobble component W (RL) of a push-pull signal itself with respect to a lens shift.

FIG. 9 is a diagram illustrating how a DC offset included in a push-pull signal obtained from a C-type disc changes with lens shift.

FIG. 10 is a diagram illustrating a case where a DC offset is removed from a push-pull signal of a small D-type magneto-optical disk with an optimum coefficient K obtained when performing tracking control with a small C-type magneto-optical disk.

FIG. 11 is a circuit diagram showing a schematic configuration of another embodiment of the present invention.

FIG. 12 is a circuit diagram illustrating a schematic configuration of a conventional tracking error detection device.

[Explanation of symbols]

 2, 4, 8 Amplitude detector 5, 7, 10, 11 Operational amplifier 6, 12 Divider

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-144029 (JP, A) JP-A-4-243028 (JP, A) JP-A-6-131680 (JP, A) 501328 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G11B ^7/ 09-7/10

Claims (6)

(57) [Claims] 1. A tracking error detection method for detecting a tracking error signal by removing an offset from a push-pull signal PP obtained from a disk-shaped recording medium having a guide groove formed in a meandering shape. A push-pull signal detecting step of detecting as a difference RL between the light amounts R and L of the reflected light from two directions sandwiching the guide groove, and sandwiching the guide groove from the light amounts R and L in two directions obtained from the reflected light Amplitudes W (R) and W of meandering components in two directions
A first meandering amplitude detecting step for detecting (L), and a difference W (R)-between the amplitudes W (R) and W (L) of the meandering components in two directions obtained in the first meandering amplitude detecting step. W (L)
And a second meandering amplitude detecting step for detecting the amplitude W (RL) of the meandering component of RL, which is the push-pull signal PP, wherein the push-pull signal PP The push-pull signal PP detected in the detecting step and the W calculated in the meandering amplitude difference calculating step
Using (R) -W (L) and W (RL) detected in the second meandering amplitude detection step, a coefficient K is expressed as follows: And using this coefficient K, A tracking error signal from which an offset has been removed. 2. A division step of dividing the push-pull signal PP by a total light quantity signal Ig, which is a sum R + L of light quantities R and L in two directions obtained from the reflected light, wherein PP calculated in the division step is provided. / Ig, W (R) -W (L) calculated in the meandering amplitude difference calculating step, and W (RL) detected in the second meandering amplitude detecting step, to obtain a coefficient K: Equation 3] And using this coefficient K, 2. The tracking error detection method according to claim 1, wherein the tracking error signal from which the offset has been removed is detected. 3. A tracking error detection device for detecting a tracking error signal by removing an offset from a push-pull signal PP obtained from a disk-shaped recording medium having a guide groove formed in a meandering shape. A push-pull signal detecting means for detecting as a difference RL between the light amounts R and L of reflected light from two directions sandwiching the guide groove, and sandwiching the guide groove from light amounts R and L in two directions obtained from the reflected light Amplitudes W (R) and W of meandering components in two directions
A first meandering amplitude detecting means for detecting (L), and a difference W (R)-between the amplitudes W (R) and W (L) of the meandering components in two directions obtained by the first meandering amplitude detecting means. W (L)
, A second meandering amplitude calculating means for calculating an amplitude W (RL) of a meandering component of RL which is the push-pull signal PP, and a meandering amplitude difference calculating means. Division means for dividing the output W (R) -W (L) by the output W (RL) of the second meandering amplitude calculation means; and coefficient multiplication means for multiplying the output of the division means by a coefficient K. A tracking error detecting device for subtracting an output of said coefficient multiplying means from an output of said push-pull signal detecting means. 4. The coefficient multiplying means outputs the following expression to the output of the dividing means: 4. A multiplication by a coefficient K represented by:
The tracking error detection device according to the above. 5. A total light amount signal I, which is a sum R + L of light amounts R and L in two directions obtained from the reflected light, based on the push-pull signal PP detected by the push-pull signal detecting means.
5. The tracking error detection device according to claim 4, further comprising push-pull division means for dividing by a g signal, wherein the output of said coefficient multiplication means is subtracted from the output of said push-pull division means. 6. The coefficient multiplying means outputs the output of the dividing means as: 6. A multiplication by a coefficient K represented by:
The tracking error detection device according to the above.