JPS63173280A - Servo-pattern for tracking - Google Patents

Abstract

PURPOSE:To surely execute a detection by constituting the titled pattern by arraying a first pattern which has placed two-frequency signals having each different frequency alternately in the width direction of a track in a two-track period, and a second pattern repeated in an (n)-track period. CONSTITUTION:After reading the data of a sector N in a data sector 4, burst signals 5, 6 are reproduced simultaneously, frequency components f1, f2 of the burst signal 5, 6 are discriminated by a discriminating circuit, and if one signal exists, an amplitude sampling signal of a servo-burst signal is generated. This signal is generated once each, four times in total, in accordance with servo-burst signals G, H, I and J. In this state, the servo-burst signals G, H are not detected, but the servo-burst signals I, J are detected so that the amplitudes of the servo- burst signals I, J become equal. In case an off-track of a +1 track has been generated, the servoburst signal G and J are detected by the same amplitude, therefore, it can be decided that the off-track of the +1 track exists.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a tracking servo pattern for an apparatus having a servo mechanism that performs tracking using a pattern signal formed on a data recording surface.

[Prior Art] A first conventional example is a servo pattern using a two-frequency signal (hereinafter referred to as a two-frequency servo pattern) shown in FIG. A servo pattern 2.3 is recorded before each data sector 1, shifted by half a track pitch. The servo patterns 2.3 are burst signals of different frequencies f, . . . f2, and are simultaneously reproduced by heads running on the track. A frequency discrimination circuit separates this signal into a signal having an f1 configuration and a signal having an f2 configuration, and controls the head positioning mechanism so that the component ratio thereof becomes 1.

As a second conventional example, there is a staggered burst type servo pattern shown in FIG.
These are mutually different pulse trains having pulses with different pulse intervals, such as double and 2.5 times. Also, C, D, E,
F is usually a burst signal of the same frequency. Pulse train A
, H, the pulse intervals are measured, and the pulse intervals can be discriminated based on the length of the pulse intervals and how many pulse intervals are present. After detecting at least one pulse train A or B of the pulse trains A and H, a timing signal for sampling burst signals C, D, E, and F for servo control is generated, and the burst signals C, D, Measure the amplitude of each reproduced signal E and F. The head positioning mechanism is controlled based on the measured amplitude ratio of each reproduction signal.

[Problems to be Solved by the Invention] As mentioned above, in the first example of the conventional servo pattern, the same servo pattern is repeated every two tracks.
There was a problem in that the servo's retraction limit was relatively narrow at +1 track.

In addition, in the second example of the conventional servo pattern, the same servo pattern is repeated every 4 tracks, so the servo pull-in limit can be set as wide as +2 tracks.
When discriminating H, it is necessary to accurately discriminate relatively close pulse intervals such as 1, 2, and 2.5 times the bit interval T, and reliable operation is difficult under the influence of noise. There was a problem.

The present invention has been made to solve these conventional problems, and an object of the present invention is to provide a tracking servo pattern that has a wide servo pull-in limit and that allows reliable control.

[Means for Solving the Problems 1] In order to achieve the above object, the present invention provides a first pattern in which three-frequency signals having mutually different frequencies are arranged alternately in the track width direction at two track periods; A second pattern that repeats at a period of n tracks (n>2) is arranged in the longitudinal direction of the tracks.

[Function] With the above configuration, the servo pattern can be detected by utilizing the ease and reliability of detecting the first pattern in which signals of two types of frequencies are simultaneously reproduced by the head running on the track. It has become possible to detect the leading edge and widen the servo pull-in limit by making use of the degree of freedom in the configuration of the second pattern.

[Embodiment] FIG. 1 shows an example of fJSi according to an embodiment of the present invention, where 4 is a data sector, 5 is a burst signal of frequency afl, 6 is a t<-x tote signal of frequency afe, G, H.

I and J are servo control burst signals (hereinafter referred to as servo burst signals) having the same frequency.

In the above configuration, let us now consider the case where the header runs on track 4n+2. After reading the data in sector N in data sector 4, the head simultaneously reproduces burst signals 5 and 6, and frequency components 'fl,
f! The circuit is configured in such a way that the signals are discriminated by a discrimination circuit, and if one of the signals is present, an amplitude sampling signal of the servo burst signal is generated. Here one frequency fluf
The reason why signals with different frequencies are used is that if the same frequency were used, the signals would cancel each other out due to six phase shifts, making detection by the discrimination circuit unstable. In addition, since the frequency of f, , f* is selected to be different (usually lower) than the data recording frequency, the amplitude sampling signal of the servo burst signal, which will not be detected erroneously within the data sector 4, is the same as the servo burst signal. G, H, 1, J
is generated a total of four times, once for each signal. Servo burst signals G, H, and I are synchronized with the amplitude sampling signal of the servo burst signal.

Measure the amplitude of J. Now, servo burst signals G, H
is not detected, and the servo burst signal 1. J is detected,
Control is performed so that the amplitudes of servo burst signals I and J are equal. For example, if we consider the case where an off-track of +1 track occurs, the servo burst signals G and J
are detected with the same amplitude, it is determined that there is +1) rack off-track. Next, considering the case where +2 track off-track occurs, servo burst signals G and H are detected with the same amplitude. However, this
This is equivalent to the case where -2 tracks of off-track occur, so it becomes impossible to determine the amount of off-track. Therefore, the pull-in limit of the servo control in the embodiment shown in FIG. 1 is +2 tracks, which is equivalent to the second conventional example, but the advantage is that the beginning of the servo signal can be reliably detected by the dual-frequency servo pattern detection. There is.

FIG. 2 shows a second example of the embodiment, where 7 is a data sector;
8 is a burst signal with a frequency f, which is longer in time than the burst signal 5 shown in FIG. By making the first burst signal 8.9 longer in time, it is possible to apply the same servo system as in the conventional example shown in FIG. can also be applied. In other words, this servo pattern has the advantage of being compatible with the two servo methods.

In the configuration shown in Figure 2, the head is now on track 4n+.
2, after reading the data in data sector N, the head simultaneously reproduces burst signals 8 and 9, uses a discrimination circuit to discriminate between frequency components 1 and f2 of burst signal 8.9, and selects either one of them. If the signal is present, an amplitude sampling signal of the servo burst signal is generated. In this case, the servo burst signal M is synchronized with the amplitude sampling signal.

N is detected, and the amplitudes of the servo burst signals M and N are controlled to be equal.

Furthermore, as a modification of the embodiment shown in FIG. 2, which is not shown, one of the burst signals 8, 9 and the servo burst signals in FIG. It is conceivable to place it in In addition, the servo system of the first conventional example and the first embodiment are applied simultaneously.

According to this method, the linearity of the detected track position error signal can be improved by aF.
If you drive at a position that is slightly shifted from directly above the truck but does not overlap the adjacent truck, the burst signal 9
is not reproduced, the accuracy of the position error amount decreases. However, according to this method, even in this state, two of L, M, and N are always detected in the servo burst signal, and the position error amount can be accurately detected.

FIG. 3 shows a third example of the embodiment, where lO is a data sector, 1
1 is a burst signal with frequency atr, 12 is a burst signal with frequency aft, and burst signals 11 and 12 have the same time length as burst signals 8 and 9 in FIG. The burst signals 13 and 14 are eight burst signals having a frequency f and a short time length, and are placed temporally apart. burst signal 15
and 16 are short burst signals having a frequency af2 and are arranged temporally apart.

Consider the case where the head runs on track 4n+2 with the above configuration. After reading the data in sector N of data sector 10, the head uses a discrimination circuit to discriminate between the frequency component signals of 0 frequency f1 and f2 that simultaneously reproduce burst signals 11 and 12, and if either signal exists, amplitude sampling is performed. Configure the circuit to generate a signal. The amplitude sampling signal is generated three times, with the first signal being
After discrimination, the frequency f and the amplitude of the acid component frequency at2 component signals are measured at the same time. The next two times are at frequency f.

Only the presence or absence of the frequency f2 component signal is detected. In this case, the ft component signal and the f2 component signal are measured to have the same amplitude, and then the f2 component signal is detected twice. For example, if we consider the case where an off-track of +1 track occurs, first the frequency f, the acid component frequency a
ft component signals are detected with the same amplitude, followed by frequency f.

Since the signal of the component is detected and finally the signal of the frequency f2 component is detected, it can be determined that there is an off-track of +1)-rack. Next, considering the case where an off-track of +2 track occurs, first the frequency @f, the component and the frequency f
Two component signals are measured with the same amplitude and the frequency a fr acid component signal is subsequently detected twice. Since this is equivalent to the case where there is an off-track of -2 tracks, it becomes impossible to determine the amount of off-track. Therefore, the servo pull-in limit is +2 tracks, which is equivalent to the conventional example shown in FIG. 6, but the time length of the servo signal can be shortened.

Also, reliable operation is performed.

A fourth example of the embodiment is based on the burst signals 13, 14 . ts, the time length of 16 is the burst signal 1
The time length is approximately the same as 1.12. This allows amplitude measurements on all eight-stroke signals. Next, the first set of burst signals and the second . Either one of the third burst signal sets is placed on the track centerline.

Figure 4 is 2. This is a case where the third burst signal is placed on the track center line.

In the configuration shown in Figure 4, now the head is track 4n+
2, create an amplitude sampling signal in the same way as the embodiment shown in Fig. 3, measure the amplitude of the burst signal 18°19 with the first amplitude sampling signal, and calculate the same amplitude measurement value. obtain.

The amplitude of the burst signal 22 is measured using the second amplitude sampling signal, and it is found that the signal has a frequency f2. In the third amplitude sampling signal, no burst signal is measured. In other words, the detection of a signal with frequency f22 in the second amplitude sampling signal indicates that the head is running near track 4n+2. The amplitude ratio of the burst signal 18.19 measured with the first amplitude sampling signal gives the position error.

For example, if we consider the case where an off-track of +1 track occurs, after first measuring the amplitude of the burst signal 18.19, no burst signal is measured in the second amplitude sampling signal, and in the third The amplitude of the burst signal 23 is measured by the amplitude sampling signal, and the frequency f2
It can be seen that this is a signal. From this, it can be determined that there is an off-track of +1 track.If there is an off-track of +2 track in the 0th order, a signal with a frequency f and a component is detected in the second amplitude sampling signal, and the third amplitude sampling signal is detected. Nothing is detected in the signal, which means
Since this is equivalent to the case where there is an off-track of -2 tracks, the servo pull-in limit is +2 tracks. The advantage of this pattern is that the linearity of the position error signal can be ensured. For example, consider the case where there is an off-track of about +0.5 tracks from track 4n+2.

In the first amplitude sampling signal, the burst signal 19L
However, the second amplitude sampling signal measures the amplitude of the burst signal 22, and the third sampling measures the amplitude of the burst signal 23. Therefore, the off-track amount can be accurately calculated based on the amplitude ratio of the burst signals 22 and 23.

[Effects of the Invention] As explained above, the tracking servo pattern of the present invention includes a first pattern in which three-frequency signals having different frequencies are arranged alternately in the track width direction at two track periods, and n Since the second pattern, which is repeated at the track period, is arranged in the longitudinal direction of the track, reliable detection is possible and the servo pattern has a wide servo pull-in limit.

[Brief explanation of the drawing]

Fig. 1 is a diagram of a servo pattern showing a first example of an embodiment of the present invention, Fig. 2 is a diagram of a servo pattern showing a second example of the embodiment, and Fig. 3 is a diagram of a servo pattern showing a third example of the embodiment. FIG. 4 is a diagram showing a servo pattern showing a fourth example of the embodiment of the present invention, and FIGS. 5 and 6 are diagrams showing conventional servo patterns. Agent Patent Attorney 1) Haru KitatakeFigure 1Figure 2Figure 3Figure 4Figure 5Figure 6

Claims (1)

[Claims] In a tracking servo pattern of a device having a servo mechanism that performs tracking using a pattern signal formed on a data recording surface, a first pattern in which two-frequency signals having mutually different frequencies are arranged alternately in the track width direction at two track periods. and a second pattern that repeats at a period of n tracks (n>2) are arranged in the longitudinal direction of the track.