JP2003203443A - Method for reproducing phase information signals in an information recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform compensation for decentering with high degree of accuracy, even if the amount of decentering of the phase patterns is large in contrast to the track density. <P>SOLUTION: The method includes the steps of: receiving a convoluted data row Pw(i) consisting of remainders obtained by dividing the original track location by 2π; generating a data row dPw(i) comprising the differential values between adjacent data in the data row Pw(i); generating a two-step differential data row δPw(i) comprising the differential values between adjacent data in the data row dPw(i); adjusting a cumulative coefficient k(i) according to the section region where the value of the two-step differential data row δPw(i) belongs; generating a differential data row dPu(i) (=δPw(i)+2π×k(i)) by applying a reconstructing process for solving the convolution process with the use of the found cumulative coefficient k(i); and obtaining a reconstructed phase information data row Pu(i) by further applying integration. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reproducing a phase information signal in an information recording apparatus, which restores an original phase information data string based on a convolutional phase information data string read by a head from an information recording medium. Regarding

[0002]

2. Description of the Related Art At present, a magnetic recording / reproducing apparatus tends to have a high recording density in order to realize a small size and a large capacity. In the field of hard disk drives, which are typical magnetic recording / reproducing devices, the areal recording density has already reached 15 Gbits / in.
More than ² (23.3 Mbits / mm ² ) devices have been commercialized, and further 40 Gbits / in ² (62.0 Mbits / m ²
Rapid technological progress is recognized toward the practical application of m ² ). It is expected that the track pitch will reach the submicron range in the near future.

In such a narrow track, a head tracking servo technique is important. In the current magnetic recording / reproducing apparatus, a pre-format information signal such as a tracking servo signal, an address information signal, and a reproduction clock signal is recorded on a disc-shaped information recording medium at regular angular intervals. By reproducing these signals at regular intervals, the head confirms the position of the head and correctly scans the target track while correcting the position.

One of such tracking servo techniques
For example, a phase servo method is known in which the time information of the reproduction signal pulse, that is, the phase information is used as the head position information (for example, refer to Patent Documents 1 and 2).

[0005]

[Patent Document 1] Japanese Unexamined Patent Publication No. 10-83640 (fifth
(Page, Figure 6)

[Patent Document 2] JP-A-11-144218 (8th Patent)
(See page 10, Fig. 7)

[0006]

When the information recording medium thus preformatted is incorporated in the information recording apparatus, the phase pattern written in the information recording medium is eccentric with respect to the rotation center of the information recording medium. Sometimes.
In this case, even if the head is stationary, the phase signal, which is the position information of the head picked up by the head, is not constant, but fluctuates in a sinusoidal manner. If this happens, tracking control cannot be performed correctly.

Therefore, it is necessary to compensate for the influence on the relative positional relationship of the head with respect to the center of rotation due to the eccentricity of the phase pattern in the information recording medium.

The present invention has been made in order to solve the above problems, and an object thereof is to enable highly accurate compensation for eccentricity even if the amount of eccentricity of the phase pattern with respect to track density is large. .

[0009]

The present invention solves the above-mentioned problems by taking the following means for the method of reproducing the phase information signal in the information recording apparatus.

A phase pattern for detecting the track position is recorded in advance on the information recording medium. The phase pattern is a repeating pattern in the radial direction. The repetition of this phase pattern causes the data convolution.

In the first step, the phase pattern on the information recording medium is read by the head to obtain a data string of phase information. The data string of the phase information is a convoluted data string that is a remainder value obtained by dividing each data of the phase information data string to be restored by a predetermined value (for example, 2π).

Next, in a second step, a difference data string having a difference value of adjacent data in the read convolutional phase information data string as a data string is generated. Further, in the third step, a second-order difference data string having a difference value of adjacent data in the difference data string as a data string is generated. Then, in the fourth step, in the second-order difference data string, a stacking coefficient is calculated according to which segmented area each data belongs to, and then restoration processing for restoring the convolution is performed to restore the data. Generate a difference data string. Finally, in a fifth step, integration processing is performed on the restored difference data string to obtain the restored phase information data string.

The above configuration can be expressed as follows if it is described in an easy-to-understand manner using symbols.

Let Pw (i) be the data string of the phase information in the convoluted state read in the first step (i = 1,2).
... N). The phase information data string to be finally restored is P
Let u (i), the stacking coefficient be k (i), and the predetermined value of convolution be α. Pu (i) = Pw (i) + α × k (i) ………………………… (1) It can be expressed as. Also, convolution involves repetition. The repetition cycle is generally represented by 2π. Therefore, if α = 2π, then Pu (i) = Pw (i) + 2π × k (i) (2).

Assuming that the difference data string generated in the second step is dPw (i), dPw (i) = Pw (i) -Pw (i-1) ... (3) is there. When the second-order difference data string generated in the third step is δPw (i), δPw (i) = dPw (i) -dPw (i-1) (4). In the fourth step, the second-order difference data string δPw
It is determined which segmental area each data item (i) belongs to, and the stacking coefficient k (i) is adjusted according to the segmental area to which it belongs. For example, in the case of the first divided area, the decrement is performed, and in the case of the second divided area, the current value is held, and the third value is held.
If it is a divided area of, it is incremented. Then, using the obtained stacking coefficient k (i), restoration processing for restoring the convolution is performed. If the restored differential data string obtained in this way is dPu (i), then dPu (i) = δPw (i) + 2π × k (i) (5). The difference data string dPu (i) restored in the final fifth step is integrated to obtain the restored phase information data string Pu (i). Letting the integration constant be γ, Pu (i) = ΣdPu (i) + γ ……………………………… (6).

Thus, the second-order difference data string δPw
(I) is used to determine the segmented area, and the stacking coefficient k (i)
Is calculated to restore the differential data string dPu (i) and further integrate to restore the phase information data string Pu (i). Therefore, even when the eccentric amount of the phase pattern on the information recording medium is large, the measurement is performed in the convoluted state. The phase signal waveform representing the original track position can be accurately restored from the generated phase signal waveform.

By using this result, the relationship between the eccentricity amount and the phase can be accurately detected. Therefore, if tracking control of the head is performed while performing eccentricity compensation using the relationship, highly accurate tracking control becomes possible.

In the above, regarding the boundary value of the divided area, modes in which the boundary value is "-π" and "π" are conceivable. As another mode, the boundary value is set to "-
3π ”,“ −π ”,“ π ”and“ 3π ”can be considered.In the former mode, the restored phase signal waveform may have a singular point where some smoothness is lost, but in the latter mode. In the mode, it is possible to suppress the occurrence of such a singular point and restore the phase signal waveform representing the track position with high accuracy.

The integration processing in the fifth step is
The average value Ea of the restored difference data string dPu (i) is used, and the average value E is calculated from the restored difference data string dPu (i).
It is preferable to numerically integrate the data string with a subtracted.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a method for reproducing a phase information signal in an information recording apparatus according to the present invention will be described in detail below with reference to the drawings.

(Embodiment 1) FIG. 5 schematically shows a pattern drawn on an information recording medium 1 such as a magnetic disk for applying a phase servo system. On the information recording surface of the disc-shaped information recording medium 1, a first area 2a and a second area 2a in which a phase pattern for detecting a track position is written.
Area 2b is provided. The phase pattern of the first area 2a and the phase pattern of the second area 2b are distinguished. The set of the first area 2a and the second area 2b forms one wedge 3. A large number of such wedges 3 are arranged at equal intervals in the circumferential direction centered on the center of the information recording medium 1. Reference numeral 4 represents one of loci on which the recording / reproducing head (see the head 18 in FIG. 4) scans the information recording medium 1.

FIG. 6 specifically illustrates two types of phase patterns. In FIG. 6, 5 is the first region 2a
The first phase pattern recorded on the second area 2b and the second phase pattern 6 recorded on the second area 2b. First
The phase pattern 5 and the second phase pattern 6 are not parallel to the radial direction of the information recording medium 1 but are inclined at a predetermined angle. The inclination direction of the first phase pattern 5 and the inclination direction of the second phase pattern 6 are opposite to each other. When the information recording medium 1 is a magnetic disk,
The magnetic phase pattern as shown in FIG. 6 can be easily obtained by magnetically transferring to a magnetic disk using a master information carrier having an array pattern of ferromagnetic thin films corresponding to the phase pattern.

When the head scans the scanning locus 4 in FIG. 5, the first reproduction signal waveform 7a corresponding to the first phase pattern 5 and the second reproduction signal corresponding to the second phase pattern 6 in FIG. Waveform 7b is obtained. A plurality of both the first reproduced signal waveform 7a and the second reproduced signal waveform 7b are generated, and detection is possible by repeating the pulse.

When the scanning locus 4 of the head changes in the radial direction, the phases of the first reproduction signal waveform 7a and the second reproduction signal waveform 7b change in the time axis direction. For example, the phases of both reproduction signals 7a and 7b when the head is scanning on the central scanning locus 4b in FIG. 6 are in the illustrated state. When the head scans the scanning locus 4a outward in the radial direction, the phase of the first reproduction signal waveform 7a advances (shifts to the left),
The phase of the second reproduced signal waveform 7b is delayed (shifted to the right). Then, the pulse interval β between both reproduction signal waveforms 7a and 7b becomes large. Conversely, when the head scans the scanning locus 4c inward in the radial direction, the phase of the first reproduction signal waveform 7a is delayed (shifted to the right) and the phase of the second reproduction signal waveform 7b is advanced (to the left). shift). Then, the pulse interval β becomes smaller.

As described above, with the change in the position of the head in the radial direction of the information recording medium 1, both reproduction signal waveforms 7a,
The phase of 7b changes and the pulse interval β also changes. Based on this, the off-track amount of the head can be detected.

Here, before starting the description of the specific technical contents of the first embodiment of the present invention, basic techniques will be described with reference to FIGS. 9 and 10 in order to facilitate understanding.

A basic technique for obtaining the phase corresponding to the position of the head for each wedge 3 shown in FIG. 5 will be described with reference to the flowchart of FIG.

In step S61, the wedge number i
Signal array V (i) of the reproduced signal corresponding to the input signal array V (i). Is detected, and in step S63,
Phase demodulation is performed on the first reproduction signal waveform 7a, and in step S64, the phase value array φa (i) corresponding to the first reproduction signal waveform 7a is acquired. On the other hand, step S
In 65, the second reproduced signal waveform 7b corresponding to the second phase pattern 6 based on the input signal array V (i).
Of the signal sequence of the second reproduction signal waveform 7b is subjected to phase demodulation in step S66.
At 67, the phase value array φb (i) corresponding to the second reproduced signal waveform 7b is acquired. Then, step S68
, The phase value array φ at the wedge number i is calculated by taking the difference between the two phase value arrays φa (i) and φb (i).
Find (i). That is, φ (i) = φa (i) −φb (i) (7). This phase value array φ (i) is the pulse interval β in FIG.
Corresponding to. The off-track amount of the head is detected based on the phase value array φ (i), and the track following automatic control is executed based on the detected off-track amount.

The phase value array φ as the difference in FIG.
(I) corresponds to β in FIG. 6, but instead of using the phase value array φ (i) as a difference for tracking control, one of the phase value arrays φa (i) and φb (i) is used. Only one may be used. Phase value array φ as a difference
If (i) is used, the sensitivity will be doubled.

In a hard disk device using the phase servo technique, a phase pattern is written on the magnetic disk before the magnetic disk is incorporated into the hard disk device.

When the preformatted information recording medium is incorporated in the information recording apparatus, the phase pattern written in the information recording medium may be eccentric with respect to the center of rotation of the information recording medium. Even if the head is stationary in the radial direction from the center of rotation of the motor, if there is eccentricity, the phase signal, which is the information on the track position, is not constant but fluctuates in a sinusoidal manner.

In recent information recording media, the track density has remarkably increased. With this increase in density, even with the same eccentricity,
The fluctuation amount of the phase signal due to the eccentricity becomes relatively large. Further, even with the same track density, the larger the eccentricity amount, the larger the variation amount of the phase signal.

If the phase signal fluctuates due to the eccentricity, the tracking control cannot be performed correctly.
Therefore, it is necessary to compensate for the variation in the phase value array φ (i) caused by the eccentricity of the phase pattern. As a countermeasure, there are the following methods.

The amount of change in the phase pattern due to the eccentricity is measured in advance and the relationship with the eccentricity is specified. For that purpose, after the information recording medium is incorporated in the information recording apparatus, the head is mechanically fixed to obtain the phase value array.

FIG. 10A shows how the phase signal waveform Su'to be restored varies sinusoidally due to eccentricity. When the fluctuation is stationary, if there is no eccentricity,
The phase signal waveform Su ′ to be restored should be kept at a constant value. However, due to the eccentricity, it fluctuates in a sine wave shape. FIG. 10B shows the phase signal waveform Sw reproduced from the information recording medium by the head. Due to the nature of the phase pattern as shown in FIG. 6, the phase signal waveform reproduced by the head is Sw in FIG. 10B, and Su ′ cannot be directly detected. However, what is necessary for eccentricity compensation is FIG.
The phase signal waveform Su ′ shown in FIG. Therefore, the original phase signal waveform Su ′ is restored from the detected phase signal waveform Sw. If this phase signal waveform Su ′ can be restored correctly,
Accurate compensation for eccentricity can be performed.

The measured phase signal waveform Sw is in a state in which the phase signal waveform Su 'to be restored is convoluted. The array of the remainder values obtained by dividing each value of the data array of the phase signal waveform Su ′ by 2π is the phase signal waveform Sw in the convoluted state actually obtained by the measurement.

Here, the convolution will be supplemented. Figure 6
Both phase patterns 5 and 6 shown in FIG. 2 are repetitive patterns in the radial direction of the information recording medium 1. The detailed state is shown in FIG. Phase pattern 9p of both reproduction signals 7a, 7b when the head passes the scanning locus 4p, and both reproduction signals 7a, 7b when the head passes the scanning locus 4r.
The phase pattern 9r of b is the same as the pattern. The reason is that the position of the intersection (for example, point P1) of the scanning locus 4p and both phase patterns 5 and 6 in the circumferential direction, and the circumferential direction of the intersection (the point R1) of scanning locus 4r and both phase patterns 5 and 6 are circumferential. This is because the position at is the same. The phase pattern 9q of both reproduction signals 7a and 7b corresponding to the scanning locus 4q intermediate between the scanning loci 4p and 4r is located in the middle of the both phase patterns 9p and 9r. Thus, the phase pattern is repeated.

Let S be the pitch of both phase patterns 5 and 6 in the circumferential direction, and θ be the inclination angle of the phase pattern 5 with respect to the radial direction. Letting R be the pitch in the radial direction where the reproduced signals have the same pattern, R = S / tan θ …………………………………………………… (8) The information recording medium 1 A stacking coefficient k is given to the rank of positions divided by the pitch R in the radial direction from the reference position.
Then, the k-th delimiter position is k × R.

Now, as shown in FIG. 11, the scanning locus position between the kth division position and the (k + 1) th division position is U (i), and k of this scanning locus position U (i). The amount of displacement from the th position to the outside in the radial direction is W
If (i), U (i) = k × R + W (i) can be expressed as (9). Similarly, U (i-1) = (k-1) * R + W (i-1) ... (10) U (i + 1) = (k + 1) * R + W (i + 1) ... (11) is assumed. What is detected by the head is W
(I-1), W (i), W (i + 1), and the actual scanning locus position U (i-1) is calculated from the detected value W (i-1), and the scanning locus position U (i) ), U (i +
1) is also obtained from the detected values W (i) and W (i + 1), respectively. W (i-1), W (i), and W (i + 1) are all in the range of 0 or more and less than R.

Here, R is converted into 2π because it has a periodicity of repetition. This is divided by R and multiplied by 2π. That is, 2π = R × 2π / R ………………………………………… (12) Pu (i) = U (i) × 2π / R ……………… …………… (13) Replace with Pw (i) = W (i) × 2π / R ………………………… (14). Then, the above formula is: Pu (i-1) = 2π × (k-1) + Pw (i-1) (15) Pu (i) = 2π × k + Pw (i) (16) Pu (i + 1) = 2π × (k + 1) + Pw (i + 1) (17) This is shown in FIG. Pw (i-1), P
w (i) and Pw (i + 1) are detected values. Pw
(I-1), Pw (i), Pw (i + 1) are all
It is in the range of 0 or more and less than 2π.

The measured phase signal waveform Sw shown in FIG. 10B is detected values Pw (i-1), Pw (i), Pw.
It is a set such as (i + 1).

The process of restoring the original smooth phase signal waveform Su 'from the measured phase signal waveform Sw is also called "unwrap". In the present specification, the unwrap is simply referred to as “restoration”. Specifically, generally, an operation as shown in FIG. 13 is performed.

Pw (i) is the measured phase signal waveform S
It is a data array of w. Pu (i) is a data array of the phase signal waveform Su to be restored.

In step S71 shown in FIG. 13, the convolutional data string Pw (i) obtained by the measurement is input. Let N be the number of wedges and prepare a variable i to count the wedges. Measurement data string Pw (i)
Is for all wedges and this is
It is represented by i = 1 to i = N.

Next, in step S72, the variable i and the stacking coefficient k (i) are initialized. Here, the stacking coefficient k (i) is a count value for adding / subtracting the phase by 2π, and its initial value is k ₀ . Stacking factor k (i)
Is an integer (natural number).

Next, in step S73, difference processing is performed on the adjacent phase data with respect to the data string Pw (i) obtained by the above measurement, and the difference data string dPw.
(I) is generated. That is, the calculation of dPw (i) = Pw (i) -Pw (i-1) (18) is executed for all wedges from variables i = 1 to i = N, A difference data string dPw (i) is generated.

Next, in step S74, it is determined whether or not each data of the differential data string dPw (i) belongs to a segmented area larger than "π". Difference data string dPw
If the value of (i) belongs to a segmented area larger than “π”, the process proceeds to step S75 and the stacking coefficient k (i) is set to 1
After decrementing (k (i) = k (i-1) -1), the process proceeds to step S78.

When the determination in step S74 is negative, the process proceeds to step S76, and the difference data string dPw (i)
It is determined whether or not each piece of data belongs to a divided area smaller than "-π". If it belongs to a segmented area smaller than “−π”, the process proceeds to step S77, and increments (k (i) = k (i) to increase the stacking coefficient k (i) by 1.
After performing -1) +1), the process proceeds to step S78.

When each data of the differential data string dPw (i) belongs to a divided area of "-π" or more and "π" or less,
The stacking coefficient k (i) is not changed, and k (i) = k
With (i-1), the process proceeds to step S78.

Next, in step S78, the measured convolutional data string Pw (i) of the current object to be processed.
The value obtained by adding 2π × k (i) to the restored phase information data string Pu (i).

Pu (i) = Pw (i) + 2π × k (i) (19) Next, in step S79, the variable i is incremented to advance the processing target by one. . Then, in step S80, the value of the variable i after the increment is N
Has not been reached, that is, whether or not the processing target still remains. If there is any, the process returns to step S73 and the same process is executed for the next target. When the processing is completed for the data string Pw (i) by all the measurements, the process proceeds to step S81, and the finally restored phase information data string Pu (i) is acquired.

From the above, the data string Pw by measurement is obtained.
The phase information data string Pu (i) representing the original track position can be restored from (i).

14 and 15 are shown in order to make the operation of FIG. 13 easier to understand visually.

FIG. 14 illustrates a case where the original phase information data string Pu (i) to be restored decreases. Data string Pu
It is assumed that (i) gradually decreases as the wedge number i increases as shown in FIG. From the state of being in the kth partitioned area A (k), beyond the kth delimiter position, (k-1)
It is assumed that the area has decreased to the th divisional area A (k-1).

FIG. 14B shows a data string Pw obtained by measurement.
(I) is shown. Pw (i) changes within the range of 0 to 2π. As the data string Pu (i) decreases, the data string Pw (i) also decreases, but when the data string Pu (i) exceeds the delimiter position k, the data string Pw (i) rises at once and from there. Will decrease again. In this way, the data string P
u (i) and the data string Pw (i) are not in a linear relationship.

FIG. 14C shows the difference dPw (i) = Pw (i) -Pw (i-1) in the data string Pw (i). Since the data string Pu (i) is gradually decreasing, the difference dPw (i) basically takes a negative value, but when it exceeds the delimiter position k, it changes to a positive value. At that time, as a general tendency, the difference dPw (i) becomes larger than “π”. Difference dPw (i) = Pw (i) -Pw
In principle, (i-1)> π is equivalent to crossing the break position from top to bottom. Therefore, it is necessary to decrement the stacking coefficient k (i) as in steps S74 to S75 of FIG.

FIG. 15 illustrates a case where the original phase information data string Pu (i) to be restored increases. Data string Pu
It is assumed that (i) gradually increases as the wedge number i increases as shown in FIG. From the state in the kth divided area A (k), beyond the kth delimiter position, (k + 1)
It is assumed that the number of cells has increased to the th segment area A (k + 1).

As the data string Pu (i) increases, the data string Pw (i) also increases as shown in FIG. 15B, but the data string Pu (i) exceeds the delimiter position k. Then, the data string Pw (i) falls all at once and increases again from there. Also in this case, the data string Pu (i) and the data string Pw (i) are not in a linear relationship. Pw
(I) changes within the range of 0 to 2π.

Difference dPw in the data string Pw (i)
(I) = Pw (i) −Pw (i−1) is shown in FIG.
As shown in, since the data string Pu (i) is gradually increasing,
Basically, it takes a positive value, but when it exceeds the delimiter position k, it is converted to a negative value. At that time, as a general tendency, the difference dPw (i) becomes smaller than “−π” (the absolute value becomes larger). Difference dPw (i) = Pw
(I) -Pw (i-1) <-π is, in principle, equivalent to crossing the break position from bottom to top. Therefore, it is necessary to increment the stacking coefficient k (i) as in steps S76 to S77 of FIG.

By the way, in the general phase restoration procedure as shown in FIG. 13, when the eccentricity of the phase pattern with respect to the track density is relatively large and the amplitude of the phase signal waveform Su ′ to be restored is large, the phase The problem arises that the restoration cannot be performed correctly. The reason is as follows. When the amplitude is small, when one segment area A (k) exceeds the delimiter position, the segment area A (k
+1), A (k-1). On the other hand, when the amplitude is large, the divided areas A (k + 2), A two steps above or two steps below
There is a possibility of shifting to (k-2). However, the process of FIG. 13 does not support that. As the amount of eccentricity increases, the stacking coefficient k (i) tends to be biased in one direction of increment or decrement.

FIG. 16 is a simulation result showing this. FIG. 16A shows a sinusoidal phase signal waveform Su ′ to be restored, which has an amplitude of 170 rad, and FIG. 16B shows a phase signal waveform Sw convolved with 2π measured by the head. And in FIG.
13C shows the phase signal waveform Su restored by the general procedure shown in FIG. As shown in FIG. 16C, the restored phase signal waveform Su is not smooth, and its amplitude is smaller than that of the phase signal waveform Su ′ to be restored. Thus, in the restoration procedure of the method of FIG. 13, when the eccentricity of the phase pattern is large, the phase signal waveform Su ′
Cannot be restored correctly.

Therefore, even if the amount of eccentricity of the phase pattern is large, it is important to correctly restore the original phase signal waveform from the measured phase signal waveform. The first embodiment of the present invention that realizes this will be described below.

FIG. 1 is a flow chart showing the procedure of a phase information signal reproducing method in the information recording apparatus according to the first embodiment of the present invention, and FIG.
3 is a flow chart showing the detailed procedure of the phase restoration processing of 3.
FIG. 3 is a waveform diagram used for explaining the operation, and FIG. 4 is a plan view showing a schematic configuration of an information recording device to which the phase information signal reproducing method of the present embodiment is applied. 5 to 7 and 9 are also applied in the present embodiment.

In FIG. 4, 1 is an information recording medium (magnetic disk), 8 is a spindle motor which supports the information recording medium 1 at its center and drives it at high speed, and 10 is a head actuator. The head actuator 10 includes an actuator arm 12 pivotally supported by a rotary shaft 11, a coil arm 14 that is connected to the actuator arm 12 and is located on the opposite side of the rotary shaft 11, and a coil attached to the coil arm 14. 13 and the actuator arm 12
A slider support beam 15 having a base end portion attached to the free end side thereof, and a fine movement actuator 16 using a thin film piezoelectric body attached to the free end side of the slider support beam 15,
The slider 17 is provided with a slider 17 attached to the tip end portion of the beam 15, and a recording / reproducing head 18 mounted on the slider 17 and the like, which is driven and controlled by a fine movement actuator 16 for minute displacement. Reference numeral 19 is a permanent magnet that is attached to the housing so as to face the coil 13, and 20 is a head positioning control unit.

The head positioning control unit 20 includes the coil 13
By supplying a drive current to the head actuator 10, the head actuator 10 is swung around the rotary shaft 11 to perform a seek operation.
The slider 17 at the tip of the head actuator 10 opposes the information recording medium 1 rotating at a high speed with a minute interval,
The head 18 reproduces the preformatted information signal from the information recording medium 1 and sends it to the head positioning controller 20.
The preformat information signal to be reproduced includes a reproduction signal having a phase pattern for tracking servo (see FIGS. 6 and 7). Head 18 for the target track
In the track following operation for positioning the track and the tracking correction operation when the track is off-track, the head positioning control unit 20 performs a predetermined calculation based on the reproduction signal for the tracking servo to generate a drive signal, and outputs the drive signal. It is sent to the thin film piezoelectric element in the fine movement actuator 16. The fine movement actuator 16 operates to control the positioning of the head 18 on the target track together with the slider 17.

FIG. 3 (a) shows the phase signal waveform Su 'to be restored, and FIG. 3 (b) shows the phase signal waveform Sw measured when it is convolved with 2π. FIG. 3C shows a step S of FIG. 1 for the measured phase signal waveform Sw.
Phase signal waveform Sdw obtained by executing the difference processing of 12
3 (d) shows the restored differential phase signal waveform Sdu obtained by executing the phase restoration process of step S13 of FIG. 1, and FIG. 3 (e) shows the integration process of step S14 of FIG. 3 shows a phase signal waveform Su obtained by executing.

The reproducing method of the phase information signal in the information recording apparatus of the present embodiment will be described below with reference to the flowcharts of FIGS. 1 and 2. The following operation is executed by the head positioning control unit 20.

In step S 11, the head 18 picks up the preformat information signal in the information recording medium 1 which rotates at high speed, and inputs it to the head positioning controller 20. The picked-up signal contains a convoluted data string Pw (i) corresponding to the phase signal waveform Sw. This data string Pw (i) has i = 1 to N
Of all wedges.

Next, in step S12, difference processing is performed on the phase data adjacent to the data string Pw (i) obtained by the above measurement, and the difference data string dPw
(I) is generated. That is, the operation of dPw (i) = Pw (i) -Pw (i-1) (20) is executed for all wedges from the variables i = 1 to i = N, A difference data string dPw (i) is generated.

Next, in step S13, a phase restoration process is performed on the differential data string dPw (i) to obtain the restored differential data string dPu (i). FIG. 3C shows the phase signal waveform Sd corresponding to the difference data string dPw (i).
Indicates w.

The detailed operation of step S13 will be described below with reference to FIG.
A description will be given based on the flowchart. The processing method of FIG. 2 is the same as the processing method of FIG. However, the target of processing is the data string Pw (i) in the case of FIG. 13, whereas it is the differential data string dPw (i) in the case of FIG.

In step S21 of FIG. 2, the difference data string dPw (i) is input.

Next, in step S22, the variable i and the stacking coefficient k (i) are initialized. Here, the stacking coefficient k (i) is a count value for adding / subtracting the phase by 2π, and its initial value is set to an appropriate value k ₀ according to the conditions.

Next, in step S23, the difference δPw (i) between the phase data adjacent to the difference data string dPw (i) is calculated. This δPw (i) will be called the second-order difference.

[0075]       δPw (i) = dPw (i) -dPw (i-1) ............ (21) Is.

In step S24, it is determined whether or not each data of the second-order difference data string δPw (i) belongs to a segmented area larger than “π”. Second-order difference data sequence δPw
If each piece of data in (i) belongs to a segmented area larger than “π”, the process proceeds to step S25, and the stacking coefficient k (i)
Decrement by 1 (k (i) = k (i-1)-
After performing 1), the process proceeds to step S28.

If the determination in step S24 is negative, the process proceeds to step S26, and the second-order difference data string δPw
It is determined whether or not each piece of data (i) belongs to a segmented area smaller than “−π”. Second-order difference data sequence δPw (i)
If each piece of data belongs to a divided area smaller than “−π”, the process proceeds to step S27, and the stacking coefficient k (i) is set to 1
Increment to increase (k (i) = k (i-1) +1)
Then, the process proceeds to step S28.

When each data of the second-order difference data string δPw (i) belongs to a segmented area of “−π” or more and “π” or less, the stacking coefficient k (i) is not changed and k (i) is not changed.
= K (i-1), the process proceeds to step S28.

The range of the second-order difference data string δPw (i) is assumed to be −2π <δPw (i) <2π.

Next, in step S28, 2π × k is added to the current second-order difference data string δPw (i) to be processed.
Difference data string dPu in which the value obtained by adding (i) is restored
(I).

DPu (i) = δPw (i) + 2π × k (i) (22) Next, in step S29, the variable i is incremented to advance the processing target by one. Then, in step S30, the value of the variable i after the increment is N
Has not been reached, that is, whether or not the processing target still remains. If there is any, the process returns to step S23 and the same process is executed for the next target. When the processing is completed for all the difference data strings dPw (i), the process proceeds to step S31, and the finally restored difference data string dPu (i) is acquired. FIG. 3D shows the differential phase signal waveform S corresponding to the restored differential data string dPu (i).
Indicates du. This phase signal waveform Sdu corresponds to a derivative of the phase signal waveform Su ′ to be restored in FIG.

After step S31 in FIG. 2, the process proceeds to step S14 in FIG. In step S14, integration processing is performed on the restored difference data string dPu (i). The integration process integrates the data obtained by subtracting the average value. That is, the restored difference data string dPu
The average value of (i) is Ea, and the difference (dPu (i) -E
By integrating a) with respect to the variable i, a data string Pu (i) of the integration result is obtained.

Pu (i) = Σ (dPu (i) −Ea) (23) FIG. 3 (e) shows the phase signal corresponding to the data string Pu (i) of the integration result. The waveform Su is shown.

In the above, the differential phase signal waveform Sdu shown in FIG. 3D is a differential waveform of the phase signal waveform Su 'to be restored in FIG. 3A. And FIG.
The integrated phase signal waveform Su shown in (e) is a waveform sufficiently approximate to the phase signal waveform Su 'to be restored. The phase signal waveform Su 'represents the original track position.

As described above, according to the reproducing method of the phase information signal in the information recording apparatus of the first embodiment of the present invention,
Even if the amount of eccentricity of the phase pattern on the information recording medium is large,
The phase signal waveform Su ′ representing the original track position can be accurately restored from the measured phase signal waveform Sw in the convoluted state. As a result, the relationship between the eccentricity amount and the phase can be accurately detected, and the eccentricity compensation can be performed using the relationship, and then the head tracking control can be performed with high accuracy.

(Embodiment 2) In Embodiment 1 described above, the restoration accuracy is greatly improved compared to the system of FIG. However, it was also found that a singular point occurs in the phase signal waveform Su restored at a plurality of points although the number is small. Therefore, the second embodiment of the present invention further improves the accuracy of restoration. The second embodiment uses the flowchart of FIG. 1 according to the first embodiment, and further, instead of FIG.
The flowchart of FIG.

The method of reproducing the phase information signal in the information recording apparatus of the second embodiment will be described below with reference to the flowchart of FIG. The processing method of FIG. 8 is a method in which the determination classification of the second-order difference data string δPw (i) is finer than that of the processing method of FIG.

Steps S41 to S43 are the same as steps S21 to S23 in FIG.

In step S44, it is determined whether or not each piece of data of the second-order difference data string δPw (i) belongs to a divided area of “3π” or more. Second-order difference data sequence δPw
If each piece of data in (i) belongs to a segmented region of “3π” or more, the process proceeds to step S45, and the decrement (k (i) = k (i−1) −2) is subtracted from the stacking factor k (i) by 2.
Then, the process proceeds to step S52.

Further, in step S46, each data of the second-order difference data string δPw (i) exceeds “π” and is “3”.
It is determined whether or not it belongs to a segmented area less than π ″, and if so, the process proceeds to step S47, and the decrement (k (i) = k (i−1) −1) that decrements the stacking coefficient k (i) by 1 is performed. )
Then, the process proceeds to step S52.

Further, in step S48, it is determined whether or not each data of the second-order difference data string δPw (i) belongs to a segmented region of “−3π” or more and less than “−π”, and if so, Proceeding to step S49, the stacking coefficient k
Incrementing (i) by 1 (k (i) = k (i-
After performing 1) +1), the process proceeds to step S52.

In step S50, it is determined whether or not each data of the second-order difference data string δPw (i) belongs to a segmented area less than “−3π”, and if so, the process proceeds to step S51. After incrementing the stacking coefficient k (i) by 2 (k (i) = k (i-1) +2), the process proceeds to step S52.

When each data of the second-order difference data string δPw (i) belongs to a segmented area of “−π” or more and “π” or less, the stacking coefficient k (i) is not changed and k (i) is not changed.
= K (i-1), the process proceeds to step S52.

The range of the second-order difference data sequence δPw (i) is -4π <δPw (i) <4π in principle.

Steps S52 to S55 are the same as steps S28 to S31 in FIG. Subsequent to step S55, the process proceeds to the integration process of step S14 of FIG.

A comparison between the method of FIG. 13 and the method of the second embodiment for performing the processing of FIGS. 1 and 8 was simulated. For example, when the wedge number N = 50, the phase signal waveform Su ′ to be restored can be satisfactorily restored up to 25 rad in the method of FIG. 13, but at 26 rad, the restored phase signal waveform Su has a disturbance. occured. On the other hand, in the second embodiment, the amplitude of the phase signal waveform Su ′ to be restored can be favorably restored up to 199 rad.

Generally, the recoverable amplitude is proportional to the wedge number N in the case of the method of FIG. 13, whereas it is proportional to N ² in the method of the present embodiment.

Further, for example, when the number of wedges N = 100, the phase signal waveform S to be restored by the method of FIG.
It could be restored well until the amplitude of u'up to 50 rad, but 5
At 1 rad, waveform distortion occurred in the restored phase signal waveform Su. On the other hand, in the second embodiment, the amplitude of the phase signal waveform Su ′ to be restored can be satisfactorily restored up to 796 rad.

According to the method of the second embodiment of the present invention, even if the amount of eccentricity of the phase pattern with respect to the track density is further increased, a singular point is not generated and the measured phase signal waveform Sw in the convoluted state is used. The phase signal waveform Su ′ representing the original track position can be restored with higher accuracy.

In any of the above-mentioned embodiments, the integration processing is to integrate the data with the average value subtracted, but in addition to this, a method of numerical integration using the Simpson's formula, A method of estimating the restored differential phase signal waveform as an approximate function and obtaining a theoretical integral function from the parameter can also be applied.

[0101]

According to the present invention, in the information recording apparatus using the phase servo system, the divided area is discriminated by using the second-order difference data string, the stacking coefficient is obtained, the difference data string is restored, and further integrated. Since the phase information data string is restored by using this method, it is possible to accurately restore the phase signal waveform that represents the original track position from the phase signal waveform measured in the convoluted state, even if the amount of eccentricity of the phase pattern on the information recording medium is large. You can

Using this result, the relationship between the eccentricity amount and the phase can be accurately detected. Therefore, if tracking control of the head is performed while performing eccentricity compensation using the relationship, highly accurate tracking control becomes possible.

[Brief description of drawings]

FIG. 1 is a flow chart showing the procedure of a method for reproducing a phase information signal in the information recording apparatus according to the first and second embodiments of the present invention.

FIG. 2 is a flowchart showing a detailed procedure of phase restoration processing according to the first embodiment of the present invention.

FIG. 3 is a waveform diagram used for explaining the operation of the phase information signal reproducing method in the information recording apparatus according to the embodiment of the present invention.

FIG. 4 is a plan view showing a schematic configuration of an information recording apparatus to which the phase information signal reproducing method according to the embodiment of the present invention is applied.

FIG. 5 is a plan view illustrating a disc-shaped information recording medium in which a preformat information signal is written as an example to which the present invention is applied.

FIG. 6 is a diagram schematically showing a phase pattern drawn on a disc-shaped information recording medium for applying the phase servo method.

FIG. 7 is a diagram showing in detail how the phase pattern of FIG. 6 is a repeating pattern.

FIG. 8 is a flowchart showing a detailed procedure of phase restoration processing according to the second embodiment of the present invention.

FIG. 9 is a flowchart showing a demodulation process of a phase information signal.

FIG. 10 is a waveform diagram showing the relationship between the phase signal waveform to be restored and the convolved phase signal waveform.

FIG. 11 is a diagram illustrating a relationship between a scanning locus position and a displacement amount.

FIG. 12 is a diagram obtained by converting FIG.

FIG. 13 is a flowchart showing the procedure of a phase signal restoration method in the basic technique.

FIG. 14 is a diagram showing the operation of FIG. 13 in an easy-to-understand manner (when decreasing).

FIG. 15 is a diagram showing the operation of FIG. 13 in an easy-to-understand manner (when increasing).

FIG. 16 is a waveform diagram used for explaining the operation of the reproducing method of the phase information signal in the information recording device in the basic technique.

[Explanation of Codes] 1 Information recording medium 2a 1st region 2b on which phase pattern is formed 2nd region 3 on which phase pattern is formed 3 Wedge 4 Scan locus 5 of recording / reproducing head 5 1st phase pattern 6 2nd Phase pattern 7a First reproduction signal waveform 7b Second reproduction signal waveform 8 Spindle motor 9p-9r Phase pattern 10 Head actuator 11 Rotating shaft 12 Actuator arm 13 Coil 14 Coil arm 15 Slider support beam 16 Fine movement actuator 17 Slider 18 Recording / reproducing head 19 Permanent magnet 20 Head positioning control unit Sw Measured phase signal waveform Su 'Phase signal waveform Sdw to be restored Phase signal waveform Sdu obtained by difference processing Phase signal waveform Su of difference obtained by phase restoration processing Integration Measurement of phase signal waveform Pw (i) obtained by processing Data sequence dPw (i) of the phase information in the convoluted state difference data sequence δPw (i) second-order difference data sequence dPu (i) restored difference data sequence Pu (i) phase information data sequence Ea restored by integration restoration Average value of the difference data sequence

Claims (5)

[Claims] 1. A first step of reading a phase pattern prerecorded as a repeating pattern in a radial direction on an information recording medium by a head to obtain a data string of phase information, and a data string of the read phase information. For generating a difference data string having a difference value of adjacent data in
And a third step of generating a second-order difference data string having a difference value of adjacent data in the difference data string as a data string, and in the second-order difference data string, each data belongs to which segmented area After calculating the stacking coefficient according to
A fourth step of performing a restoration process to restore the convolution and generating a restored difference data sequence, and performing an integration process on the restored difference data sequence to obtain a restored phase information data sequence. A method of reproducing a phase information signal in an information recording apparatus, which includes a fifth step. 2. The data string of the phase information in the first step is a convoluted data string which is a remainder value obtained by dividing each data of the phase information data string to be restored by 2π. A method for reproducing a phase information signal in the information recording apparatus according to the item 1. 3. The method for reproducing a phase information signal in an information recording apparatus according to claim 2, wherein in the fourth step, the boundary values of the divided areas are “−π” and “π”. 4. The phase information in the information recording apparatus according to claim 2, wherein in the fourth step, the boundary values of the divided areas are “−3π”, “−π”, “π” and “3π”. How to play the signal. 5. The integration process generates a data string obtained by subtracting an average value of the restored phase information data string from each data of the restored phase information data string, and numerically integrates the generated data string. The method for reproducing a phase information signal in an information recording apparatus according to any one of claims 1 to 4, which is performed by