JPS6246421A - Tracking method for magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To attain accurate tracking with a simple mechanism by using a head having two different head gaps in width and detecting the frequency characteristics of a reproducing signal to execute tracking. CONSTITUTION:When a narrow gap Ga of the tracking head 2 having two different head gaps Ga, Gb in width is disengaged from a track T, the gain of a high frequency component is reduced because the frequency characteristic of the gap Ga has its peak in the high frequency band, so that the output signal gain of a detector 10 is reduced. An differential amplifier 12 outputs a signal corresponding to the disengagement under the status that the gap Gb is held on the track and its disengaged side can be decided on the basis of said output signal. Thus, the positions of the signal reproducing head 1 and the head 2 are controlled by supplying a tracking error signal obtained from the output signal of the amplifier 12 to a reproducing head block circuit to attain accurate tracking.

Description

[Detailed description of the invention] I was born and raised in Japan. The present invention relates to a tracking method, particularly a magnetic disk.

A magnetic recording and reproducing device for recording and reproducing video signals, audio signals, etc. on a magnetic recording medium such as a magnetic tape, and for causing a recording and reproducing head to follow a track provided on the magnetic recording medium. Regarding tracking methods.

In general, tracks are formed on a magnetic disk in a concentric or spiral shape, and in a method of recording diagonally with a rotating head using a magnetic tape, tracks are formed diagonally. Therefore.

When recording and reproducing information on these recording media,
It is necessary to perform tracking servo to make the recording/reproducing head follow the track.

As such a tracking method, various methods have been proposed in the past, but the following four types are the main ones.

(a) A method of forcibly displacing a single magnetic head in the width direction of a recorded track and detecting changes in the playback output signal level, a method called the "wobbling method" or "mountain climbing method" belongs to this method.

(b) A method of recording pilot signals for tracking along with video, audio signals, etc. during recording using methods such as frequency multiplexing or time division; ATF for 8mm VTRs;
, DTP systems use this method.

(C) A method of obtaining magnetic head position information by using a plurality of magnetic heads and detecting the output signal level of the track being followed or its adjacent track.

(d) A method of recording servo information using means such as forming tracking grooves on an information recording medium, a servo surface disk 8 used in a hard disk device, a DRAw, etc.
Ute, Gako. Use the method, 1:: Mouth is closed.
shall be. The various methods described above have the following problems.

(a) In the "wobbling method", a magnetic "rad" is excited using an electromechanical transducer, and the off-track amount and its direction are thereby detected.

However, the vibrations are transmitted to the magnetic recording medium.

The time axis of the reproduced signal fluctuates, and this time axis fluctuation causes, for example, jitter in the video signal, causing deterioration in image quality.

In addition, the "mountain climbing method" requires a circuit to store the immediately preceding error signal, and in order to improve tracking accuracy, it is necessary to reduce the amount of displacement per time.
When the amount of displacement is reduced.

It becomes impossible to follow high frequency disturbances such as eccentric components of the magnetic disk, resulting in a problem that the bandwidth of the servo loop becomes narrow. 111:.

(b) Record pilot signals for tracking
In this method, the pilot signal is converted into video and audio signals.1. i;'1. ′ When recording with wave number multiplexing, video and audio signals can be recorded.
The disadvantage is that the frequency range that can be achieved by 1:1 becomes narrower, the amount of information decreases, and one-frequency gaps and beats occur. Furthermore, if the pilot signal is recorded by time division multiplexing such as sector servo, the servo signal can only be obtained discretely and the sampling frequency is usually low, resulting in a dead time element and limiting the loop bandwidth of the servo system. It has the disadvantage of being stored away.

(c) Although the method of using multiple magnetic heads has the advantage that servo signals can be obtained continuously for one hour, it also causes various problems because it reproduces a part different from the main head. Mechanisms for holding and transferring, signal transmission systems, and electrical systems such as head amplifiers have become increasingly complex, and there are only a few examples of them being put to practical use.

(d) The method of forming tracking grooves is used in audio LP records (although not 11K recording), but it has the disadvantage that it is not suitable for random access due to its structure. In addition, the method of optically tracing mechanical grooves using a laser beam, as used in the DRAv system, has problems with defects in the recording medium and damage caused by dust.
The disadvantage is that the tracking is disturbed. On the other hand, the servo disk system, which is often used in hard disk drives, has the drawback that tracking is disturbed due to differences in thermal expansion based on the temperature 4 inside the drive.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a tracking method for a magnetic recording/reproducing device that can perform accurate tracking with a relatively simple mechanism.

- The second feature of the present invention is that the recording/reproducing head follows the track provided on the magnetic recording medium.
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111, the magnetic head used for tracking is designed to have a head gap with at least two gap widths.
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to reduce the reproduction signal obtained from the magnetic head.
1:□ Separate into high frequency component and high frequency component,
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1. Amplify the two signals separately at a predetermined amplification factor, and adjust the recording/reproducing head and the front according to the difference between these two signals.
:The relative position between the magnetic head and the track is controlled.

action In the present invention, the reproducing output voltage by the magnetic head.

This technique skillfully utilizes the principle that the magnetic head has frequency characteristics dependent on the gap width of the head gap provided in the magnetic head. A with different gap widths, 82
A head gap is formed on the magnetic head, and the frequency characteristics of the reproduction output voltage from this magnetic head are monitored to determine whether the magnetic head is following the track normally, whether the ped gap A side has deviated from the track, or whether the head gap It is possible to determine whether the B side has deviated from the track and to perform accurate tracking with a relatively simple mechanism.

Daiarashi Team The present invention will be described below based on examples. The following embodiment is an example in which the method according to the present invention is applied to a still video floppy playback device. Generally still video floppy (
According to the NTSC standard, frequency bands are assigned as shown in Figure 2, and FM-modulated video signals are recorded. That is, the color signal (Chrominance) is 1.2 to 1,3
M) Luminance signal (Lua+1
nance) are respectively allocated and recorded in the 6.0 MHz to 7.0 MHz to 7.5 MHz high frequency band. FIG. 3 is a graph showing frequency analysis of the reproduced signal using a spectrum analyzer when the signal recorded in this manner is reproduced. As shown in this graph, the synchronization tip of the luminance signal (at 6 MHz in this example).

Color signal carrier waves R-Y, B-Y (in this example, 1.2 and H
z, 1.3 MHz) always exists, and its output level does not change depending on the content of the video signal and is constant.

FIG. 4 is a graph showing the frequency characteristics of the reproduction output voltage using the width of the head gap as a parameter in the magnetic recording and reproduction apparatus. It can be seen that the frequency at which the maximum output is obtained changes depending on the width of the head gap. The wider the head gap width, the lower the frequency band in which maximum output can be obtained.

FIG. 5 shows a magnetic head used for tracking in the present invention. This magnetic head is formed with head gaps having two different gap widths: a narrow head gap Ga and a wide head gap Gb. However, this head is wound with a single coil, and electrically functions as one head. That is, one part of one head forms a wide head gap, and another part forms a narrow head gap. As mentioned above, the frequency band in which the maximum output can be obtained depends on the head gap width, but the frequency characteristic of the narrow head gap Ga has a peak at the synchronous tip frequency position in Fig. 3, and that of the wide head gap Gb. It is preferable that each gap width is set so that the frequency characteristic has a peak at the carrier frequency position of the color signal shown in FIG.

FIG. 1(a) is a block diagram of an embodiment of a still video floppy playback device using the method according to the present invention. In this embodiment, a tracking head 2 is provided independently in addition to the signal reproducing head 1 to perform tracking.

Both heads are configured to move in conjunction with each other at regular intervals. The signal reproducing head 1 is a head having a normal gap width.1. The tracking head 2 is
This is a head having a head gap with two different gap widths as shown in FIG. The output signal of the signal reproducing head 1 is applied to a video signal processing circuit 4 via a preamplifier 3, and a reproduced video signal is obtained at an output terminal 5. on the other hand,
The output signal of the tracking head 2 is amplified through a preamplifier 6 and then divided into two systems. One is the low frequency component (1.2 to 1.3 MHz) that passes through the bandpass filter 7.
), and the other is the high frequency component (6Ml(z)) that passes through the bandpass filter 8. The detector 9 detects and outputs the envelope of this low frequency component, and the detector 10 detects the high frequency component. Detect and output the envelope.

Here, the output signal of the detector 9 is amplified by a predetermined amplification/factor (including attenuation) by the amplifier 11, and this amplified signal and the output signal of the detector 10 are provided to the differential amplifier 12.

Now, as shown in FIG. 6(b), in a state where the head gap G is properly placed on the track T, that is, in an on-track state, the amplification factor of the amplifier 11 is appropriately changed, and the differential amplifier 12 is adjusted. Adjust so that the output is zero. By adjusting in this manner, it is possible to know that the head has gone off-track simply by monitoring the output of the differential □ amplifier 12. For example, consider a case where the side of the narrow head gap Ga deviates from the track T, as shown in FIG. 6(a). Since the frequency characteristic of the head gap Ga is set to have a peak at the synchronization tip (6 MHz), that is, in the high frequency band, this head gap Ga
deviates from the track T, the gain of the high frequency component decreases, and the output signal gain of the detector 10 decreases. Since the wide head gap Gb remains on-track, there is no change in the gain of the low frequency component, and the two input signals of the differential amplifier 12 are eventually balanced, and the differential amplifier 12 receives this difference. Outputs a signal according to the Conversely, as shown in FIG. 6(C), if the frequency characteristic of the head gap Gb is deviated from that of the wide head gap Gb, the frequency characteristic of the gap Gb is similar to the carrier wave of the color signal (1.2 to 1.3M).
Hz), that is, it is set to have a peak in the low frequency band, so the gain of the low frequency component is reduced, and the differential amplifier 12 outputs a signal of opposite polarity.

As described above, when the tracking is off, the differential amplifier 12 outputs a signal corresponding to the degree of the off-tracking.
From the polarity of the signal, it can be determined which side the signal has deviated from. Note that the output signal of the differential amplifier 12 is given to a sample and hold circuit 13, where synchronization signals H,
The signal is sampled and held for the time period during which 5YNC exists, and is outputted to the output terminal 14 as a tracking error signal. Accurate tracking can be achieved by configuring a feedback loop control system that supplies this tracking error signal to a playback head block drive circuit (not shown) to control the positions of the signal playback head 1 and the tracking head 2. can be done.

The synchronizing signals H, 5YNC can be obtained as follows based on the output signal from the signal reproducing head 1. As described above, the output signal of the signal reproducing head 1 is amplified by the preamplifier 3 and provided to the video signal processing circuit 4. Here, the demodulated signal as a baseband video signal is applied to the synchronization separation circuit 15, and based on this, the phase and
A synchronized signal) 1.5YNC is generated.

FIG. 1(b) is a block diagram of another embodiment of a still video floppy playback apparatus using the method according to the present invention.

In this embodiment, the dual-purpose head 16 is made to perform the functions of both the signal reproducing head 1 and the tracking head 2, and the head is unified, the mechanical system and circuit system are simplified, and the adjustment part is simplified. I'm doing less. The dual-purpose head 16 is a head having head gaps with two gap widths as shown in FIG. It will be done. The following operation is the same as that of the embodiment shown in FIG. 1(a), so the explanation will be omitted. Note that since the dual-purpose head 16 has two head gaps, the reproduction frequency characteristics will be different from those of the signal reproduction head 1. However, since the reproduction signal is an FM modulated wave, the video signal processing circuit 4 There are no harmful effects to the processing.

Although the method according to the present invention is applied to a still video floppy reproducing device, it is of course possible to apply the method to other magnetic recording and reproducing devices. However, in systems that record azimuth without using a guard band, such as the current 172-inch VTR (VH5 system and β system), the azimuth effect differs depending on the playback frequency, so a correction circuit is required. . Therefore, the present invention is most preferably used in devices such as still video floppies that have guard bands between recorded magnetic tracks.
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As described above, the method according to the present invention is similar to the conventional method.
: 1 problem 1 t)) An°L'C solved 6: t 1 t-r! ：■ There is no need to vibrate the head, eliminating the harmful effects of vibration.

■ No need to record special pilot signals;
Since it has a wide information band and is versatile, it can be widely applied to devices that perform magnetic recording.

(2) As shown in FIG. 1(b), if a dual-purpose head is used, a single head can be used, the mechanism becomes simple, and the system can be made smaller and lighter.

■ Since there is no need to form tracking grooves, there are no problems when performing random access, and there are few negative effects from dust.

As described above, according to the present invention, in a tracking method for a magnetic recording/reproducing device, a head having a head gap with two different gap widths is used to detect the frequency characteristics of a reproduced signal to perform tracking. This makes it possible to perform accurate tracking with a relatively simple mechanism.

[Brief explanation of drawings]

FIGS. 1(a) and (b) are block diagrams of an embodiment of a still video floppy playback device using the method according to the present invention, and FIG. 2 is a typical frequency when recording information on a still video floppy. A graph showing the allocation. Figure 3 is a frequency analysis graph of a general playback signal of a still video floppy.
Fig. 4 is a graph showing the frequency characteristics of the reproduction output voltage using the width of the head gap as a parameter, Fig. 5 is an explanatory diagram of the magnetic head used in the present invention, Fig. 6(a), (
b) and (C) are explanatory diagrams showing the positional relationship between the track and the head gap. 1... Signal reproduction head 2... Tracking head 3... Preamplifier 4... Video signal processing circuit 5... Output terminal 6... Preamplifier 7.8... Bandpass filter 9.10 ... Detector 11 ... Amplifier 12 ... Differential amplifier 13 ... Sample hold circuit 14 ... Output terminal 15 ... Synchronization separation circuit 16 ... Dual-purpose head 17 ... Preamplifier G ...Bed gap Gb...Wide head gap T...Track

Claims (3)

[Claims] (1) A tracking method for a magnetic recording and reproducing device for causing a recording and reproducing head to follow a track provided on a magnetic recording medium, the magnetic head used for tracking having at least two different gap widths. forming a gap, separating the reproduced signal obtained from the magnetic head into a low frequency component and a high frequency component, and amplifying the low frequency component and the high frequency component separately at a predetermined amplification factor. A tracking method for a magnetic recording and reproducing apparatus, characterized in that the relative positions of the recording and reproducing head and the magnetic head and the track are controlled according to the difference between the two amplified signals. (2) A tracking method for a magnetic recording/reproducing apparatus according to claim 1, wherein the recording/reproducing head and the magnetic head used for tracking are composed of the same head. (3) A tracking method for a magnetic recording/reproducing device according to any one of claims 1 to 2, wherein the track is recorded using a guard band method.