JPH11203645A - Method of tracking control in information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tracking control method capable of more securely tracking without decrease in recording capacity in a high-density information recording medium performing tracking-control in a servo system. SOLUTION: On this recording medium, information recording tracks I, II, m...VII, in which data blocks (1-1), (2-2),... and gap parts 3, 3,... are alternately continued, are arranged in parallel to the travelling direction and also side by side and a servo burst part 4 is provided in a continuous area 3A of gap parts over each of the information recording tracks I, II,...VII. Then, in the tracking control, a plural error signals are prepared at the same time from the servo burst-signal recorded in the servo burst-signal recording parts (5-1), (5-2),... of the servo burst-part 4 and the tracking is controlled by using the most probable signal among the error signals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tracking control method for an information recording medium, and more particularly, to an information recording medium for performing servo type tracking control without substantially reducing the recording capacity. The present invention relates to a tracking control method that enables reliable tracking.

[0002]

2. Description of the Related Art In an information recording medium such as a tape streamer, the track density is increased in order to improve the recording density and reduce the size, and a servo signal for tracking is used in place of the conventional open loop control by a stepping motor. Various techniques have been proposed for controlling the position of the recording / reproducing head with high precision by recording. The present inventors have already applied for a patent for the novel technology relating to the above high-density recording medium as an information recording medium and a recording / reproducing method thereof (Japanese Patent Application No. 8-33709).

In the information recording medium disclosed in the above-mentioned application, a plurality of information recording tracks in which data blocks and gap portions are alternately arranged are arranged in parallel and parallel to the traveling direction, and the gap portions extending over each information recording track are arranged. Is a medium in which a specific servo burst portion is formed in a direction perpendicular to the running direction in a continuous area of the medium. In recording / reproducing on such a recording medium, a recording / reproducing head having a plurality of head gaps is used, and recording / reproducing from the center of an information recording track is performed based on a change in the intensity of a reproduced signal obtained from a servo burst section. A deviation of the position of the head is detected, and the position of the recording / reproducing head is controlled with high accuracy based on the deviation.

[0004]

In the tracking control of the so-called multi-gap servo system used in the information recording medium as described above, a tracking error occurs if a part of the servo burst portion is defective. I do. Moreover, as a result of increasing the track density of the information recording medium, the tracking control is affected by minute defects that have not been a problem so far.

In the tracking control of the multi-gap servo system, if a servo burst portion has a defect, a normal data block (sector) following the servo burst portion is also processed as a defective block and cannot be used as a data storage area. . As a result, not only is the recording capacity substantially reduced, but also the production yield of the medium is significantly affected, so that it is not possible to satisfy the practical requirement of providing an inexpensive and large-capacity information recording medium.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to substantially reduce the recording capacity of an information recording medium having a high density and performing servo type tracking control as described above. An object of the present invention is to provide a tracking control method for an information recording medium capable of performing more reliable tracking without reduction.

[0007]

To solve the above-mentioned problems, the present invention relates to a tracking control method for an information recording medium, wherein the information recording medium has a data block of a predetermined length and a gap portion alternately. A plurality of information recording tracks are arranged in parallel and parallel to the traveling direction,
In a continuous area of the gap portion over each of the information recording tracks, a servo burst portion formed by alternately arranging a servo burst signal recording portion and a signal non-recording portion in a direction orthogonal to the traveling direction is provided, The servo burst signal recording portion extended perpendicularly to the traveling direction is formed with a length that is at least twice the arrangement pitch of the information recording tracks. A plurality of error signals are generated at a time from the servo burst signals recorded in the servo burst signal recording section, and tracking is controlled using the most probable signal among the error signals.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a tracking control method for an information recording medium according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic plan view showing a partially enlarged information recording track and a servo burst portion of an information recording medium applied to the tracking control method of the present invention.
FIG. 2 is a schematic plan view showing the relationship between the position of the head gap of the recording / reproducing head and the servo burst signal to be used. FIG. 3 is a waveform diagram showing an example of a reproduced signal strength and a composite signal output from four head gaps.
FIG. 4 is a principle diagram showing the generated error signal and the position of the recording / reproducing head.

The tracking control method of the present invention is applied to the information recording medium disclosed in Japanese Patent Application No. 8-33709. As shown in FIG. 1, such an information recording medium includes a plurality of information recording tracks (1-1, 2-1,...) Of a predetermined length and a plurality of information recording tracks (3, 3,. .. VII) are arranged parallel to and parallel to the traveling direction.

FIG. 1 shows, for convenience of explanation, reference numerals (I, II,...).
The case where there are seven information recording tracks as shown in VII) is illustrated, and only a portion related to tracking control of the information recording medium is extracted and shown. The set of one data block in each of the information recording tracks (I, II,... VII) is denoted by code (1-1, 1-2... 1-7), and the set of the next data block is denoted by code (2--1). 1,2-2 ... 2-
7).

In the information recording medium shown in FIG. 1, the information recording tracks (I, II,... VI) are provided in a continuous area (3A) of the gap portion over each information recording track (I, II,.
A data ID signal section (9, 9,...) Corresponding to I) and a servo burst section (4) are provided. The data ID signal section (9) is provided as necessary for the purpose of recording information such as a distance from a data recording start point and a track number. The servo burst section (4) has a head (7) (recording /
Provided for controlling tracking of the reproducing head. The servo burst section (4) includes a servo burst signal recording section (5-1, 5-2 ...) and a signal non-recording section (6-1, 5-2).
6-2...) Are alternately arranged in a direction orthogonal to the traveling direction.

The servo burst signal recording sections (5-1, 5-2,...) Extended in the direction perpendicular to the running direction are arranged at an array pitch (track arrangement interval) of the information recording tracks (I, II,... VII). (L) is formed with a length of twice or more, preferably twice as long as the signal non-recording portions (6-1, 6-2,...).
Are formed with the same length as the servo burst signal recording sections (5-1, 5-2...). Moreover, the servo burst signal recording section (5-1, 5-2...) And the signal non-recording section (6-1, 5-2)
6-2...) Are set so as to be located, for example, substantially at the center of the information recording tracks indicated by reference numerals (II), (V) and (VII) when they are extended in the traveling direction. .

A head (7) disposed opposite to the recording surface of the information recording medium reads and writes signals.
One or more head gaps (recording / reproduction head gaps), preferably four head gaps (8-1) to
(8-4) are provided at intervals equal to the arrangement pitch (L) of the information recording tracks (I, II,... VII), and the head (7) is provided with these head gaps (8-1, 8-2).
..) Simultaneously read or write signals.

In the tracking control of the information recording medium, four head gaps (8-1, 8-
2) are provided, and the servo burst signal recording sections (5-1, 5) of the servo burst section (4) are used.
.-2), the deviation of the position of the head (7) from the center of the information recording tracks (I, II,... VII) is detected. Then, based on the detected deviation, at least one head gap (8-
1), (8-2)... Or (8-4) is positioned in the servo burst signal recording section (5-1, 5-2...) To control tracking.

That is, at least one of the head gaps (8-1), (8-2)... Or (8-4) corresponds to the servo burst signal recording section (5-1), (5-2).
-7) and the signal non-recording portions (6-1), (6-2)... Or (6-7), in other words, the four head gaps (8-1) to (8). The head (7) is controlled so that the phase difference between the reproduction signals of the two pairs of head gaps in (-4) is 90 degrees. In addition, as the reproduction signal intensity, an appropriate value such as a magnitude between peaks, an average of absolute values, and an integrated value of amplitude can be adopted.

The tracking control is basically as described in the above publication. Specifically, the first to fourth four head gaps (8-1,
8-2...), The positions of the head (7) shown in FIG. 2, that is, the head gap (8-1) are the information recording tracks. When the displacement from the position corresponding to the center of (I) in the direction of the information recording track (VII) is obtained, changes in the reproduction signal intensities (A) to (D) are obtained as waveform outputs as shown in FIG. . The symbols (I), (II)... (V) in FIG.
Each shows the position of the information recording track in FIG.

Therefore, first, four head gaps (8
., 8-2...) Detect the rising edge of the servo burst signal, and measure the reproduction signal intensities (A) to (D) of the servo burst signal as a starting point. Next, a cosine signal (X) = (A−
C), a sine signal (Y) = (BD) as a composite signal is generated, and an error signal is obtained under the following conditions.

[0018]

When Y> 0 and | Y |> | X |, a cosine signal (X) is used as an error signal. When X> 0 and | X |> | Y |, a sine signal (Y) is used. ) Is an error signal. If Y <0 and | Y |> | X |, a cosine signal (X) is an error signal. If Y <0 and | X |> | Y |, a sine signal is used. (Y) is an error signal (| X |, | Y | are the absolute values of the cosine signal (X) and the sine signal (Y), respectively). The waveforms of the cosine signal (X) and the sine signal (Y) are shown in FIG. e)
And (f).

The relationship between the error signals can be represented, for example, as a substantially square Lissajous figure composed of sides (α), (β), (γ) and (δ), as shown in FIG. Then, each side (α), (β), (γ) and (δ) of the Lissajous figure
Corresponds to each waveform section shown in FIGS. 3 (e) and 3 (f). Then, each information recording track (I, II,... VII)
4 corresponds to the intersection of the coordinate axes in FIG. 4, so that the head gap (8-1, 8-2...) Is always positioned on the intersection of the coordinate axes in the control of the head (7). What is necessary is to control.

For example, if the output of the head gap (8-2) is 1 in the state of the head (7) shown in FIG. 2, the outputs of the head gaps (8-1) and (8-3) are both 0. .5, the output of the head gap (8-4) is 0, the cosine signal (X) is 0, and the sine signal (Y) is 1
(Corresponding to the position of the symbol (A) in FIG. 4).

On the other hand, when the head (7) is displaced in the direction of the information recording track (II), the head gap (8-
Although the outputs of 2) and (8-4) do not change, the output of the head gap (8-1) is larger than 0.5 and the output of the head gap (8-2) is smaller than 0.5. Therefore, the cosine signal (X) has a positive value. That is, in FIG. 4, this means that the position of the head (7) has moved from the code (A) to the code (A '), and the amount of movement corresponds to the magnitude of the position error of the head (7). The magnitude of such an error can be calculated from the slope of a line drawn from the center of the coordinate axis to the symbol (A ') on the Lissajous figure. The moving amount of the head (7) can be calculated as the magnitude of the angle from the following relationship, for example.

[0022]

[Table 2] When the head is moving on the side (α), tan ^-1 (X / Y) When the head is moving on the side (β), tan ^-1 (Y / X) The head is on the side (γ) When moving on tan ^-1 (X / Y) When the head is moving on side (δ), tan ^-1 (-Y / X)

As described above, when two sets of difference signals are used, there is no influence of a change in the reproduction signal due to a change in the contact state between the recording surface of the medium and the head (7). Control with higher resolution is possible as compared with the case where two difference signals are used.

In the tracking control method of the present invention as described above, accurate tracking is performed even if there is a slight defect in the servo burst signal recording section (5-1, 5-2...) Of the servo burst section (4). For this purpose, a plurality of error signals are created at once from the servo burst signals recorded in the servo burst signal recording units (5-1, 5-2...), And the most probable signal among the error signals is subjected to the tracking control. It is important to use.

Specifically, as described above, the first to fourth 4
The reproduced signal strengths (A) to (D) output from the two head gaps (8-1, 8-2...) Become waveform signals as shown in FIG. 3 with the displacement of the head (7), and For example, the combination of the combined signals [AC] and [BD]
It can be handled as a combination of two synthesized signals having phases substantially different from each other by about 90 °. Moreover, the synthesized signal [A
+ C] = [B + D] = constant,
Using such a relationship, one head gap (8-1,
Or 8-4) is generated from the output signals of the other three head gaps, so that a combination of the same type of combined signal as the combination of the combined signals [AC] and [BD] is obtained. can get.

As a combination of the two synthesized signals having phases substantially different from each other by 90 °, in addition to the combination of the synthesized signals [AC] and [BD], the synthesized signals [AC] and [(A + C) −
2D], the combination of the combined signals [2B- (A + C)] and [AC], and the combination of the combined signals [BD] and [(B
+ D) -2C], and a combination of the combined signals [BD] and [2A- (B + D)].

Then, for example, a servo burst signal recording section (5-1,...) Which outputs a reproduction signal strength (B) by calculating a combination of the combined signals [AC] and [(A + C) -2D]. Or, if 5-2) is not accurately reproduced due to a defect, accurate tracking can be performed.
Similarly, the combined signals [2B− (A + C)] and [A−
C], the servo burst signal recording unit (5-1, 1) that outputs the reproduction signal strength (D) is calculated.
... or 5-2) has no problem even if a defect occurs.
Can track accurately.

Further, in the same manner, the servo burst signal recording unit (5-) which outputs the reproduced signal strength (A) by calculating the combination of the combined signals [BD] and [B + D-2C].
There is no problem even if a burst error occurs in 1, 2,... Or 5-2), and the combined signals [BD] and [2A- (B
+ D)], the servo burst signal recording unit (5-1,
... or 5-2), there is no problem even if a burst error occurs, and any of them can be accurately tracked.

That is, in the present invention, two or more combinations of the combined signals are calculated, and the tracking is controlled by the most likely combination of the combined signals.
.. Or 5-2) can be accurately tracked even if there is a defect.

In the above embodiment, for example, all combinations of the four synthesized signals are calculated and compared, and a unique combination is determined by detecting a unique signal. Then, a servo burst signal recording unit (5
-1, ... or 5-2) is defective.
The signal obtained from the servo burst signal recording unit is excluded from the control information for tracking, and the signals obtained from the other servo burst signal recording units are averaged and handled as a deviation signal as described above. As a result, the position of the head (7) can be controlled with high precision with respect to the high-density information recording tracks (I, II,... VII).

Therefore, according to the tracking control method of the present invention, even if a defect occurs in the servo burst signal recording section (5-1,... Or 5-2) of the servo burst section (4), information recording is performed. Since the tracks (I, II,... VII) can be reliably tracked, the data blocks (1-1, 2)
-1,..., 2-2...) Can be sufficiently used, and the recording capacity is not substantially reduced, and the production yield of the medium is not reduced.

[0032]

As described above, according to the tracking control method for an information recording medium according to the present invention, a plurality of error signals are generated and the most probable signal among the error signals is used. Even if there is a defect in a specific servo burst signal recording section, accurate tracking can be performed.
As a result, the recording capacity of the medium can be sufficiently ensured, and the production yield of the medium does not decrease.

[Brief description of the drawings]

FIG. 1 is a schematic plan view showing an information recording track and a servo burst portion of an information recording medium applied to a tracking control method of the present invention in a partially enlarged manner.

FIG. 2 is a schematic plan view showing a relationship between a position of a head gap of a recording / reproducing head and a servo burst signal to be used.

FIG. 3 is a waveform chart showing an example of a reproduced signal strength and a composite signal output from four head gaps.

FIG. 4 is a principle diagram showing an error signal to be created and a position of a recording / reproducing head.

[Explanation of symbols]

 1-1, 2-1 ...: data block 1-2, 2-2 ...: data block 3: gap section 3A: continuous area of gap section 4: servo burst section 5-1, 5-2 ...: servo burst signal Recording section 6-1, 6-2 ...: No signal recording section 7: Head 8-1, 8-2 ...: Head gap I, II, ...: Information recording track

Claims (4)

[Claims] 1. A tracking control method for an information recording medium, wherein the information recording medium includes a plurality of information recording tracks in which a data block of a predetermined length and a gap portion are alternately continuous in parallel with and parallel to a traveling direction. Are arranged in
In a continuous area of the gap portion over each of the information recording tracks, a servo burst portion formed by alternately arranging a servo burst signal recording portion and a signal non-recording portion in a direction orthogonal to the traveling direction is provided, The servo burst signal recording portion extended perpendicularly to the traveling direction is formed with a length that is at least twice the arrangement pitch of the information recording tracks. A tracking control method comprising: generating a plurality of error signals at a time from a servo burst signal recorded in the servo burst signal recording unit; and controlling tracking by using a most probable signal among the error signals. . 2. The tracking according to claim 1, wherein a tracking is controlled by using a recording / reproducing head provided with four or more head gaps and positioning at least one of said head gaps in a servo burst signal recording section. Control method. 3. The length of a servo burst signal recording portion of a servo burst portion on an information recording medium is set to twice the arrangement pitch of information recording tracks, and four head gaps are provided at intervals equal to the arrangement pitch. 3. The tracking control method according to claim 1, wherein the tracking is controlled using the recording / reproducing head. 4. A reproduction signal intensity (A) output from each of four head gaps of a recording / reproduction head.
Based on (D), among the synthesized signals generated from these,
A combination of two synthesized signals whose phases are different from each other by approximately 90 °, that is, a combination of the synthesized signals [AC] and [BD], a combination of the synthesized signals [AC] and [(A + C) -2D], The synthesized signals [2B- (A + C)] and [A-
C], the combined signals [BD] and [(B + D)
-2C] or the combined signals [BD] and [2A]
4. The tracking control method according to claim 3, wherein two or more combinations of − (B + D)] are calculated, and tracking is controlled by a combination of the most probable synthesized signals. 5.