JPS5933618A - Detecting system of track position shift - Google Patents

Abstract

PURPOSE:To detect the position shift of a reproducing head, by decreasing the gap width of a reproducing head less than the track width and providing the position shift detecting heads at both sides of the track width direction to detect the presence or absence of correlation of the reproduced signal given from the detecting head. CONSTITUTION:The reproducing head given from a reproducing head 9 is multiplied by the reproducing signal given from a position shift detecting head 10 to obtain a product signal. At the same time, a product signal is obtained by multiplying the reproducing signal from the head 9 and the reproducing signal from a position shift detecting head 11. These product signals are integrated by an integration circuit having a time constant large enough to the cycle of a data signal. Each signal obtained from the integration circuit varies in response to the correlation of two reproducing signals having amplitudes multiplied by each other. Then the position shift can be detected for a track 7 of the head 9 by comparing the amplitudes of output signals given from each integration circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a track position shift detection method that is suitable for magnetic disk storage devices and the like and is used to cause a playback head to follow a track recorded with a guard band.

It is a well-known fact that in recent years, as information processing capabilities have improved, there has been an increasing need for increased recording capacity, and the recording density of recording media has been increasing year by year. In order to increase the recording density, it is necessary to increase the linear recording density in the moving direction of the recording medium and the track density in the direction perpendicular to this. For large magnetic disk storage devices, the track density has increased from 500 to 700 tracks per inch over the past decade.
The number increased to 800 books, and around 1985, 1 book was published.
It is expected that there will be more than 1,000 copies.

Therefore, the track pitch, which was about 50 pm, has become narrower to 32 to 36 pmK, and furthermore, it has to be about 25 pm.

On the other hand, as the track density increases in this manner, an increase in noise due to misalignment of the reproduction head with respect to the track becomes a problem. The following is a detailed explanation of this problem.
7<Explain.

FIG. 1 is an explanatory diagram showing the mechanism of noise generation due to misalignment of a reproducing head with respect to a track.

In FIG. 1, if we consider two trunks 1.2 that are adjacent to each other, these tracks 1.2 are naturally recorded by the recording head, but when recording information, the -C recording medium and 1. A relative displacement occurs between the recording head and the recording head, so that tracks 1 and 2 are not parallel, but are closer together or farther apart.

Therefore, if the track hit is Wp and the relative maximum positional deviation between the recording medium and the recording head is ΔS, then the track width Ww is Ww ”= W p−2ΔS . . .
・・・・・・ Track 1 is set to (1) so that a guard band 3 with a width of 2ΔS is formed between tracks.
．． 2, tracks 1 and 2 can be recorded without interfering with each other.

On the other hand, in a magnetic disk storage device, when recording data, a data signal is supplied to the recording head to saturate the recording medium, and the recording medium is magnetized to saturation along the track where old data is recorded. New data is recorded while data is being erased, forming a single track.

Now, regarding track 1, when the old data was recorded, the recording head was misaligned, so the old data track 1' was recorded in a crooked manner as shown by the dotted line, and then the new data was recorded on trunk 1''. When recorded along track 1' of the old data, it curves as shown in the solid line. 4.5, old data will remain without being deleted.

When reproducing track 1'' recorded in this way, the reproducing head also deviates from the track by the maximum positional deviation ΔS in the same way as the recording head. (When in the playback state where When the playback head is still in the playback state as indicated by 6', the playback head also scans the portion 5 where the old data remains and generates a new data signal proportional to Ww 2ΔS. An amount of the old data signal proportional to 2ΔS is obtained.Since the old data signal is noise, the S/N ratio in this case is Ww 2ΔS 2 ΔS, and Wp = 25.4 p m , ΔS=
],, 5 p m, - the above formula (1) a, ra,
The S/N is about 6.47, which is 20~
Does not reach 30dB.

In order to reduce noise caused by unerased old data and improve S/N, the gap width of the endogenous head is made narrower by 2ΔS than the track width Ww, as shown by reference numeral 6'' in FIG. Even if the head deviates from the track by ±ΔS, it is sufficient to prevent the head from protruding from track 1''. However, in this case, the effective playback width WR of track 1'' is WR = WP 6ΔS, and if Wp and ΔS are set to the above values and -C, then WR = 16.4 p m. Therefore, there is a drawback that the amplitude of the reproduced signal is significantly reduced by 7.

Therefore, it becomes necessary to make the playback track follow the track. For this purpose, it is better to detect the positional deviation of the playback head with respect to the trunk and adjust the position of the endogenous head using a control signal corresponding to the positional deviation.

Reproduction: As a means of detecting the positional deviation of the RAD, conventionally,
A technique is known in which all the positional deviation detection heads are used on both sides of the playback head in the track width direction, and the amplitudes of the reproduction signals obtained from each of the positional deviation detection heads are compared (Japanese Patent Application Laid-Open No. 56-11102). -119973). However, in this prior art, as shown in FIG.
If there is, even though the playback head is misaligned, the old data will be played back due to the gutter to detect the shift of one position, resulting in an error in the detection of the misalignment of the playback head. However, there was a drawback in that the endogenous head could no longer accurately follow the track.

An object of the present invention is to eliminate the drawbacks of the prior art described above, and to provide a track position that allows a playback head to always accurately follow a track and to obtain a playback signal with a large amplitude and an improved S/N ratio. The present invention provides a method for detecting deviation.

In order to achieve this object, the present invention provides positional deviation detection heads on both sides in the L/rack width direction of a reproducing head having a gap width slightly narrower than the track width, and detecting the position of the reproducing head with respect to the reproduced signal Jsf from the reproducing head. The present invention is characterized in that it is possible to detect the presence or absence of correlation between the respective reproduction signals from the displacement detection head, and to detect the positional displacement of the reproduction head based on the presence or absence of correlation.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is an explanatory diagram showing an embodiment of the track position deviation detection method according to the present invention, in which 7 is a track, 8 is an unerased portion of old data, 9 is a playback head, and 10.11 is a position deviation detection head. It is.

In the same figure, -C, there is an unerased portion 8 of 111 data on the first side of track 7, and the recording medium t has an arrow ['-+1X
Assume that the object is being transported in the direction. The internal head 9 that scans the track 7 is formed so that its gap width is slightly narrower than the width of the track 7, and displacement detection rads 10 and 11 are provided on both sides of the reproducing head 9 in the track width direction. , playback head 9, positional deviation detection head to, 1
1 forms a composite head. When the gap width of the positional deviation detection head 10.11 is equal and the center of the endogenous head 9 in the track width direction coincides with the center O of the track, the positional deviation detection head 10.1
1 scans both ends of the track 7 over the same width to reproduce data signals of the same amplitude, and the gap between the reproducing head 9 and the phase shift detection head 10°11 is on the same straight line in the track width direction. Each head 9. The arrangement of the positional deviation detection heads io, it with respect to the beef cow/throat 9 is set so that the phases of C) raw signals obtained from to, 11 match.

As mentioned above, the composite head has -
C, state A where there is no deviation from tracks 1 to 'Li11', state 13 where the track position is off by 1w in one direction, or state C where the track position IM is off in the other direction, etc.
Due to such a one-off shift, the amplitude of the reproduced signal obtained from the C1 reproducing head 9 and the LID shift detection head 10 and 11 changes.

Therefore, for a displacement x of the center line of the internal head 9 in the track width direction with respect to the center line 0 of the track 7, the respective outputs from the playback head 9 (7th position 9 detection head 10° 11) The amplitude of the Kaigi signal changes as shown in Figure 3, 73e.

In FIG. 3, the horizontal axis represents the amount of positional deviation X, and the vertical axis represents the amplitude of each reproduced 1 inch. The solid line represents the change in the amplitude of the internal 1 inch of the atdM raw head 9, and the It is symmetrical about the axis. The dashed line indicates the part 8 of the old data left unerased (Figure 2)
The two-dot chain line C shows the reduction in the amplitude of the output signal of the positional deviation detection head 11 when there is no Ii7. ' represents the change in the amplitude of the misalignment detection head 100 birth number 18, and since these changes in amplitude are symmetrical about the axis of X=0, G7. lN-4 detection head 10.11
By comparing the 4-axis widths of the PJ raw signals from the PJ raw signals, it is possible to detect a 1-1 shift in the playback head 9, and adjust the internal head 9 so that the amplitudes of those 14" raw 1 numbers are equal to each other. By performing the 2nd yen adjustment, the playback head 9 is placed in the trunk 7 so that the first position is 0.
can be made l.

However, in reality, as shown in Figure 2, 11''
Due to the deletion of data, there is a remaining part 8.

When the positional deviation detection head 11 scans this portion 8, a reproduced signal will naturally be obtained. Therefore, the change in the amplitude of the reproduced signal obtained from the positional deviation detection head 11 is as follows.
As shown by the dotted line d in FIG. 3, when comparing the amplitude of this reproduced signal and the generated signal from the positional deviation detection head 10,
x-0, that is, a position just D from the center line O of track 7, is considered to be the correct position of the self-generating head 9 with respect to track 7, and the position of the playback head 9 cannot be accurately aligned. , the ability to follow the track will be reduced.

Furthermore, as mentioned earlier, the positional deviation @X is set to 11' Ill
Or, if it is attempted to be lower than that, the absolute value of the reproduction signal of the positional deviation detection heads to, ti becomes small. For example, even in the case of the magnetoresistive magnetic head, which currently has the highest sensitivity, the output voltage per 1 μm is at most 30 μV, □, while the input equivalent noise of the amplifier is 4 t'V.
Since r□ is 8 degrees, it is difficult to obtain a resolution of 1/8 p +n or less.

By the way, in FIG. 2, the reproduction signals obtained by scanning the trap 7 with the reproduction head 9 and the positional deviation detection heads 10 and 11 are all in phase. On the other hand, the old data in the unerased portion 8 of the old data has a random phase with respect to the new data recorded on the track 7, and there is no correlation between the new and old data.

Therefore, the reproduction signal from the P] raw head 9 and the reproduction signal from the misalignment detection head IO are multiplied to obtain a -C product signal,
Still, the reproduction signal from the reproduction head 9 and the endogenous signal from the positional deviation detection head 11 are multiplied to obtain a product signal, and these product signals are processed by an integrating circuit with a time constant sufficiently large with respect to the period of the data signal. Integrate. The amplitudes of the respective signals obtained from the integrating circuit vary depending on the correlation of the two reproduced signals to be multiplied.

Next, regarding this point, Figure 4 (a), (b), (
C), (dn.

(e) will be explained in more detail.

FIG. 4(a) shows the reproduced signal from the reproducing head 9 (FIG. 2), and FIG. 4(b) shows the reproduced signal from the positional deviation detection head 10 (FIG. 2) by scanning the track 7. of,
FIG. 2C shows reproduction signals obtained by scanning the portion 8 of the old data left unerased by the positional deviation detection head 111 (FIG. 2).

Since the reproduction signal from the positional deviation detection head 10 is in phase with the reproduction signal from the reproduction head 9, when these reproduction signals are multiplied by the multiplier circuit, the obtained product signal is
As shown in Figure (d), the signal becomes a positive amplitude signal. Therefore, by integrating this product signal using an integrating circuit with a sufficiently large time constant, an output signal with a large amplitude can be obtained. On the other hand, the reproduced signal from the positional deviation detection head 11 (Fig. 4(C)
)) is the reproduction signal from the reproduction head 9 (Fig. 4(a)).
Since the phase is random with respect to
As shown in Figure (e), the signal becomes a signal whose amplitude changes from positive to negative. Therefore, by integrating this product signal using an integrating circuit with a sufficiently large time constant, an output signal with a small amplitude close to zero can be obtained.

Now, in FIG. 2, if a positional deviation occurs in the x>O direction, the larger the positional deviation in this direction, the larger the amplitude of the reproduced signal from the positional deviation detection head 10, and the larger the positional deviation in this direction. Since the amplitude of the reproduced signal due to scanning the unerased portion 8 of the old data from 11 also increases, the amplitude of the output signal obtained by integrating the signal shown in FIG. The amplitude of the output signal obtained by integrating the signal shown in Figure (e) becomes smaller and smaller.

Conversely, when a positional shift occurs in the x < 0 direction, the greater the positional shift in this direction, the greater the amplitude of the output signal obtained by integrating the signal shown in Figure 4(d). The amplitude of the output signal obtained by integrating the signal shown in FIG. 4(e) becomes increasingly large. Therefore, by comparing the amplitudes of the output signals from the respective integration circuits, the endogenous head 9
It is possible to detect the positional deviation of the track 7 with respect to the track 7.

Regarding the time constant of the above dC integration circuit, the frequency of the recorded data is approximately several hundred kHz to 10 MHz, whereas the frequency of the signal to be corrected for track position deviation may be at most several kHz. From Fig. 4(d),(e)
Set so that hundreds to thousands of pulses of the waveform shown in can be integrated. In this way, FIG. 4(d).

Since the product signal in (e) is integrated with a very small time constant of J' with respect to the pulse period, the amplitude ratio of the output signal from each integrating circuit becomes extremely large, and the position of the playback head 9 is accurately determined. Adjustment is possible, and the influence of noise can be sufficiently suppressed, resulting in a high C8/N.

In addition, if there is no part 8 of the old data left unerased.

From the positional deviation detection heads io and ti, reproduced signals are obtained by scanning the track 7, and the amplitude of each reproduced signal varies depending on the positional deviation. The product signal of the reproduction signal No. 1 with the detection head 10 and the product signal of the reproduction signal with the reproduction head 9 and the position detection head 9 both have positive amplitudes as shown in FIG. 4(d). The signals are different in amplitude depending on the magnitude and direction of the positional shift. Therefore, the amplitudes of the outputs m obtained by integrating the respective product signals are also different from each other, and by comparing the amplitudes of these output signals, it is possible to detect the position error of the reproduced signal.

FIGS. 5(a) and 5(b) are plan views showing specific examples of the composite head, respectively, as viewed from the side that contacts the -0 recording medium.

Figure 5 (a) tj: Shows a specific example of an inductive head, 12
゜13.14, 15, 16.17 are magnetic cores, 18゜1
9.20 is a gap, and 21, 22.23 are windings.

The reproducing head 9 is composed of a magnetic core 12, 13 and a winding 21, and has a gap 1 slightly narrower than the track width.
8 is formed. The positional deviation detection head 10 is composed of a magnetic core 14.15 and a winding 22, and a gap 19 is formed.
1 is composed of a magnetic core 16, 17 and a winding 23, and a gap 20 is formed. The gaps 19 and 20 of the misalignment detection heads to and ii have the same width, and are arranged on the same straight line as the gap 18 of the reproducing head 9.

FIG. 5(b) shows a specific example of a magnetoresistive head,
24. ．． 25.26 is a magnetoresistive sensor, 27.28
is a magnetic shield, and 29 and 30 are gaps.

The reproducing head 9 is constituted by a magnetoresistive sensor 24 and magnetic shields 27, 28 forming a gap 29°30, and the positional deviation detection head 10 is constituted by a magnetoresistive sensor 25 and magnetic shields 27, 28. The positional deviation detection head 11 is constructed by forming a gap 29.30 between the magnetoresistive sensor 26 and the magnetic shield 27.28. The width of the magnetoresistive sensor 24 is made slightly narrower than the track width, and the width of the magnetoresistive sensor 25.
26 have the same width. The magnetoresistive sensors 24, 25, and 26 are arranged on the same straight line, and
The magnetic shields 27 and 28 are magnetoresistive sensors 24 and 2.
5.26. With this better configuration, the magnetic shields 27, 28 can be shared by the read head 9 and the misalignment detection head 10, 11.

As described above, by configuring the compound -\rad, when track 7 (Fig. 2) is scanned, playback current 9
, reproduction signals of the same phase can be obtained from the positional deviation detection heads 10 and 11. In addition.

It is clear that the composite head is not limited to the specific examples shown in FIGS. 5(a) and 5(b).

It is clear that the present invention can be applied not only to magnetic disk storage devices, but also to other recording and reproducing devices that require position adjustment of a reproducing head with respect to a track, such as a video recorder.

As explained above, according to the present invention, even if there is an unerased portion of the old information signal, it is possible to detect the positional deviation of the playback head with respect to the track with a S/N of 11 or less and with high accuracy. The reproducing head can be made to follow the track very accurately, and the disadvantages of the above-mentioned prior art can be overcome by reproducing the large-amplitude, high-S/N information signal from the i-rack. Excellent except 41. It is possible to provide a full range of track misalignment detection methods with the following functions.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a mechanism for generating noise due to fi'l misalignment of the playback head with respect to the trunk; FIG. A characteristic diagram showing the amplitude change of the reproduced signal of each head with respect to the track position deviation in Fig. 2, Fig. 4(a),
(b), (C), (d), (e) are waveform diagrams of No. 1d to explain the operation of Fig. 2, Fig. 5 (a), (b)
) d is a plan view showing a specific example of a compound henode. 7...i rack, 8...I■data unerased portion, 9...[(1 cow-\throat, 10.11... position (K shift detection--throat. Early l Figure 20) 0 Kaya 3rd 5 Nagi-83-

Claims (1)

[Scope of Claims] 1. In a track position deviation detection method in which a playback head follows a track recorded with a guard band, the gap width of the playback head is slightly narrower than the width of the track. The first one is on both sides of the playback head in the track width direction. A second positional deviation detection head is provided, and a second positional deviation detection head is provided, and a second positional deviation detection head is provided for detecting the reproduction signal from the reproduction head. 2nd digit + g
, the first . Obtain a second signal, and obtain the first signal. A track positional deviation detection method, characterized in that a positional deviation of the reproducing head with respect to the track can be detected by a second signal. 2. In claim 1, the first and second signals are a reproduction signal from the endogenous head and the first and second signals. A track positional deviation detection method characterized in that the signals are obtained by multiplying a reproduced signal from a second positional deviation detection head and integrating the respective signals.