JPS6190318A - Tracking servo method - Google Patents

Abstract

PURPOSE:To improve accuracy and recording density by making the track width of a head narrower than the total width of two adjoining tracks and adopting such servo as to maximize the amplitude of a beat component of each reproducing tracking servo signal. CONSTITUTION:On tracks T1 and T2 for tracking servo, signals for tracking servo with different frequencies f1 and f2 are recorded. A head HD scans for reproducing bestriding the tracks T1 and T2 and the track width W of the head is set smaller than the total of the track widths W1 and W2 of the tracks T1 and T2. And such track servo is adopted that the amplitude of the beat component of the tracking servo signals reproduced from the tracks T1 and T2 by the head HD will be maximized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a tracking servo system using a tracking servo signal.

[Conventional technology]

BACKGROUND ART In recent years, as recording and reproducing apparatuses have become more densely recorded, there has been a movement to shorten recording wavelengths and narrow track widths to realize high-density recording.

As a result, accurately aligning the head with the track, ie, tracking servo, has become an important issue.

Various types of tracking servo systems have been proposed in the past, one of which is known as a tracking servo system using a track servo signal used in video tape recorders. This uses two types of tracking servo signals with different frequencies, fl and f, and tracks fl, -'1#' in track order.
Tracking servo signals of different frequencies are alternately recorded in l# along with information signals, so that the frequencies of the tracking servo signals differ between two adjacent tracks.

Generally speaking, in a video tape recorder that performs azimuth recording, the next track is formed so as to partially overlap the previously formed track, and for this reason, the width of the formed track is smaller than that of the head. narrower than the track width.

Therefore, during playback, the head scans not only the track from which the information signal is to be played back, but also its adjacent tracks at the same time. The tracking servo signal is regenerated. The amplitude of this tracking servo signal increases as the head deviates from the track from which the information signal is being reproduced, so the tracking servo signal from the adjacent track is detected from the signal reproduced by the head, and the amplitude is minimized. By performing tracking servo, the head can be aligned with the track on which the information signal is to be reproduced.

Other tracking servo systems used for magnetic disks, etc., are equipped with a dedicated tracking servo disk and head, and use signals reproduced from this disk to generate information signals such that the amplitude of this signal is maximized. It performs tracking servo of the head that reproduces and scans recorded tracks. ← Hair ≠ ≠ Ax and a half [Problem to be solved by the invention] In the conventional technology used in the video tape recorder mentioned above,
Since the track width of the head is wider than the width of the track formed on the recording medium, it is not possible to increase the accuracy of tracking servo.

That is, in FIG. 3, Ti, T, , T are tracks, HD is a head, the tracks T, , T have a width of W, and a tracking servo signal of frequency f is overlapped with an information signal. Track T has a width of Wl and a frequency of 1. It is assumed that the tracking servo signal is recorded. Also, the track width W of the head HD is wider than wtl or WR (
(machi-cho)

Now, assuming that track T is a track on which an information signal is to be reproduced by the head HD, five states <a> to (e) can be assumed when performing tracking servo for this head HD. Here, state (a).

In (e), since the head HD is entangled with the track T and is greatly deviated, the amplitude of the tracking servo signal of the frequency f reproduced from the adjacent track TI or T is not the minimum, but the amplitude of the tracking servo signal is not the minimum. , the head HD is subjected to tracking servo.

On the other hand, the head HD is located on the adjacent track T1. T
.

The state (C) in which the head HD is exactly aligned with the track T is the state in which the head HD is exactly aligned with the track T, and at this time, the tracking servo signal of frequency etc. ) has the smallest amplitude.

However, one end of the head HD is track T, 1T8.
Even in the state (b) where the other end coincides with the boundary line of the track T, , and the state (d) where the other end coincides with the boundary line of the track T1, the tracking servo signal of the frequency f reproduced by the head) ID is The amplitude is the same as in state (C). That is, even if the head HD is in any state between state (d) and state (d), the amplitude of the tracking servo signal of frequency f reproduced by the head HD is kept at a minimum. Therefore, even if the state of the head HD changes from state (C) within the range from state (b) to state (d), it is determined that the head HD is correctly aligned with track T2, and this becomes a tracking error. .

Therefore, such track T1. When T, , T, are used as tracking servo tracks, and the tracking servo of the ↑R report signal writer head is performed using the tracking servo signal of frequency aft obtained from the head HD, the state of the head H1) (b) Corresponding to (d), an irreversible tracking error occurs in the information signal reproducing head.

In addition, in the prior art used for the magnetic disk described above, if there is a difference between the track width of the tracking servo disk and the track width of the playback head, the playback head will not be able to track the tracking servo track as in the above conventional technology. Even if there is a deviation from the state in which the tracking servo mechanism accurately matches, if the deviation is within a certain range, the amplitude of the signal reproduced from the tracking servo track is maintained at its maximum, resulting in a region where the servo mechanism does not operate.

In order to solve the above problem, it is possible to make the tracking servo track to be formed equal to the track width of the head, but if this is done, the compatibility of the media is not guaranteed, so it is necessary to Track narrowing is limited and high ffl! Recording will be restricted.

SUMMARY OF THE INVENTION An object of the present invention is to provide a track servo system that eliminates such problems, improves the accuracy of track servo, and allows narrowing of the track.

[Means for solving problems]

To this end, the present invention makes the frequencies of tracking servo signals recorded between two adjacent tracks different, and these two tracks are recorded with a head having a track width narrower than the total width of these two tracks. The tracking servo mechanism is operated according to the amplitude of the beat component of the tracking servo signal reproduced from these two tracks, and the tracking servo is performed so that the amplitude of the beat component is maximized. This is what I did.

〔Example〕

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

FIG. 1 is an explanatory diagram showing an embodiment of a tracking servo system according to the present invention, and parts corresponding to those in FIG. 3 are given the same reference numerals.

In FIG. 1, track Tl + Tt constitutes a tracking servo track, and is called track T.

A tracking servo signal of frequency f1 is recorded in the track T! is the frequency f! Tracking servo signals are recorded. Head HD is track T,
, T, and has a width w1. of track T1*Tt. W, then the track width W of the head Hl) is set so that w < wt + wt.

This tracking servo track is connected to the head 1-1D.
-tJXfi raced live on the hill, track T1. Tracking servo is performed using a tracking servo signal reproduced from T. This tracking servo will be explained with reference to FIG. In addition, in FIG. 2, l is a reproduction amplifier, 2 is a low-pass filter, and 3 is a tracking servo mechanism.

A reproduction signal from the head HIJ is amplified by a reproduction amplifier 1 and then supplied to a low-pass filter 2. This reproduced signal includes a tracking servo signal of frequency f1 reproduced from track TI in FIG. 1 and a tracking servo signal of frequency f reproduced from track T. separates the beat components of these tracking servo signals.

Therefore, the frequency f1 in the reproduction signal output from the reproduction amplifier l. Let the tracking servo signals of f be s and a Sl, respectively, and S, = asin2πf, t8@ = bsin2rf, t, then the beat component S output from the low-pass filter 2
, is expressed as follows.

8Hocabsin:2r(fl ft)t...
...=...(1) Beat component s from this low-pass filter 2
it is supplied to the tracking servo mechanism 3 to form a signal corresponding to its amplitude (oc; 1b), which then generates the beat component S1. Tracking servo is performed so that the maximum

Incidentally, in the tracks T, , T, a tracking servo signal of frequency f1 and a tracking servo signal of frequency f are recorded with the same amplitude.

For this reason, as long as the head HD is on the tracking servo track, a-)-b is always constant. Therefore, in order for the amplitude of the beat component S□ expressed by the above equation (1) to be maximum, it is necessary that a = b. This is obtained when the center of the head HD is located on the boundary line of the tracks T, , T, in FIG.

In this embodiment, tracking servo is performed so that the head f-11) is in this state, and even if the head HD deviates slightly from this state, tracking servo is performed, and therefore, W (W,
As long as the conditions of + W, are satisfied, the tracks T, , T
Even if the widths of , , and , are narrower than the track width W of the head HD, tracking servo can be performed with high accuracy, and high recording density can be realized.

By the way, the tracking servo tracks T, , T shown in FIG. 1 can be used exclusively for tracking servo, in which no information signals are recorded. In the case of a magnetic disk device, the tracking servo track shown in FIG. In order to maximize
Tracking servo may be applied so that the head HD scans, and the information signal may be reproduced by a head that reproduces and scans the track on which the motion information signal is recorded in conjunction with the head HD.

Further, in such a magnetic disk, information signals may also be recorded on the tracking servo track. In this case, a head for reproducing the information signal is provided separately from the head HD for reproducing the tracking servo signal. As mentioned above, the tracking servo signal is extracted from the signal reproduced by the tracking servo head using an appropriate low-pass filter, and the signal reproduced by the information signal head is extracted using an appropriate high-pass filter. ,
The information signal is extracted as before except for the mixed tracking servo signal.

In yet another embodiment, a tracking servo signal is recorded in the lower layer of the magnetic medium and an information signal is recorded in the upper layer of the magnetic medium using heads with different gap lengths and azimuth angles.

By using the azimuth effect of each head without using a low-pass filter or high-pass filter as in the above embodiment, it is possible to reproduce a tracking servo signal from one head and an information signal from the other head. .

In these two embodiments, tracking servo can only be applied during playback, but one embodiment in which tracking servo can be applied also during recording will be described next.

That is, the magnetic medium is composed of high coercive force magnetic powder and low coercive force Mi magnetic powder, and the tracking servo signal is composed of high coercive force magnetic powder and the information signal is composed of low coercive force magnetic powder so that the azimuth angles are different from each other, or they are Record signals in different frequency bands. In this case, by appropriately selecting the coercive force of these magnetic powders, once the tracking servo signal is recorded, there is no need to re-record it, and even if the information signal is previously recorded, the tracking servo signal will disappear. You can avoid it.

Furthermore, in this case, if the tracking servo signal is recorded at the factory when the disk is shipped, the tracking servo signal can be simultaneously detected by the information signal reproducing head during use.

This embodiment will be described in more detail with reference to FIGS. 4(a) and 4(b). It should be noted that FIG. 5A is a plan view of the disk, and FIG. 2B is a cross-sectional view of the disk.

In the figure (a), Φ), T1. Ill is a track on which a tracking servo signal is recorded, and these tracks T, , T are formed of high coercive force magnetic powder, but due to the magnetic field strength of the recording head, they are mainly formed in the lower layer R1 of the magnetic medium. It is formed. Further, the frequency of the tracking servo signal C recorded on every other track T is f1m, and the frequency of the tracking servo signal C recorded on every other track T is f! It is.

S is a track on which an information signal is recorded, and is formed mainly of low coercive force magnetic powder of a magnetic medium, and is formed equally spanning two tracks T1 r T*. Since the track S is mainly formed of low coercive force magnetic powder,
It is mainly formed in the upper layer Ra of the magnetic medium due to the magnetic field strength of the recording head.

With this configuration, tracking servo is performed so that the center of the head HD precisely coincides with the boundary line between two adjacent tracks T□, T.

〔Effect of the invention〕

As explained above, according to the present invention, the accuracy of the tracking servo is greatly improved, and the track width can be narrowed to improve the recording density, thereby solving the problems of the prior art. It is possible to solve this problem and provide a tracking servo system with excellent functionality.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an embodiment of the tracking servo system according to the present invention, and FIG. 2 is a block diagram showing a reproducing system for the tracking servo signal shown in FIG. FIG. 3 is an explanatory diagram showing an example of a conventional tracking servo system, and FIG. 4 is an explanatory diagram showing another embodiment of the tracking servo system according to the present invention. T, , T,...Track, HD...
... Head, 1 ... Playback amplifier, 2 ...
・Low-pass filter, 3... Tracking servo mechanism. :”1-t Figure 2 (o) (b) (c) (d)
(e) Fang 4 (a) (b)

Claims (5)

[Claims] (1) Two types of tracking servo signals with different frequencies are used to record different types of tracking servo signals between adjacent tracks, and the track width of the head is made smaller than the total width of the two adjacent tracks. A tracking servo method characterized in that track servo is performed such that the amplitude of the beat component of the tracking servo signal reproduced from each of the two adjacent tracks by the head is maximized. (2) The tracking servo method according to claim (1), wherein the track is a track dedicated to tracking servo that is provided separately from a track on which a desired information signal is recorded. (3) The tracking servo method according to claim (1), wherein a desired information signal is recorded on the track together with the tracking servo signal. (4) In claim (3), the information signal is recorded in an upper layer of a recording medium, and the tracking servo signal is recorded in a deeper layer of the recording medium at an azimuth angle different from that of the information signal. A tracking servo method that is characterized by: (5) In claim (3), the recording medium is a mixture of two types of magnetic powder having different coercive forces, and the tracking servo signal is transmitted to the magnetic powder having a high coercive force, and the information signal is transmitted to the magnetic powder having a high coercive force. A tracking servo system characterized by recording on the magnetic powder having a low coercive force.