JPH0378687B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tracking method for correctly scanning a recording track with a magnetic head during reproduction in a magnetic recording/reproducing apparatus.

In a magnetic recording/reproducing apparatus in which adjacent tracks have different azimuths, if a track shift of the read magnetic head occurs during playback, a time axis shift of the read signal occurs due to the azimuth. Examples of inventions that attempt to determine the amount of track deviation by utilizing this are JP-A-52-21811, JP-A-53-17311, JP-A-53-144308, and JP-A-54-25807.
It has been proposed in the Publication No. However, both methods have the problem that it is difficult to separate the time axis deviation caused by fluctuations in scanning speed in the scanning direction during recording or reproduction from the time axis deviation caused by track deviation.

An object of the present invention is to detect only the time axis deviation caused by track deviation without being influenced by the above-mentioned fluctuations in scanning speed, and to detect the correct amount of track deviation.

The present invention uses an auxiliary reproducing magnetic head which is located close to the recording/reproducing magnetic head, has a different azimuth from the magnetic recording head, and is the same as the azimuth of the adjacent track. regenerating a track deviation detection pilot signal (hereinafter simply referred to as a pilot signal);
By recording a signal synchronized with this reproduction signal in the recording/reproducing head, a pilot signal with the same phase between adjacent tracks is recorded during recording, and at the same time, during reproduction, the sub magnetic head and the recording/reproducing magnetic head simultaneously record adjacent tracks. By reproducing the pilot signal of the track currently being scanned, the pilot signal will be regenerated without being affected by scanning speed fluctuations during reproduction, and the amount of track deviation will be determined from the phase difference between the pilot signals regenerated from both tracks. That is.

Figure 1 shows a two-head helical scan of the present invention.
A recording pattern of an embodiment applied to a VTR is shown in FIG. 2, which is a head arrangement diagram of a rotating magnetic head device.

In FIG. 2, magnetic head 1 is a recording/reproducing magnetic head having a positive azimuth angle (hereinafter simply referred to as a magnetic head), and magnetic head 2 is a recording/reproducing magnetic head having a negative azimuth angle (hereinafter simply referred to as a magnetic head). ), the magnetic head 3 has the same azimuth angle as the magnetic head 2, and with respect to magnetic tape scanning,
A sub-magnetic head exclusively for reproduction placed close to the position preceding the magnetic head 1, which is connected to the rotating cylinder 40.
is fixed. As shown in FIG. 1, this embodiment uses a so-called azimuth overwriting method, and the head track width of magnetic heads 1 and 2 is set to a value slightly wider than the recording track width.
The head track width of the sub magnetic head 3 is made much wider than that of the magnetic heads 1 and 2.

FIG. 3 shows a circuit block diagram of this embodiment. A pilot signal of a single frequency from the oscillator 17 is intermittently sent to an appropriate interval by a gate circuit 18 and then sent to an adder 19.
The signal is superimposed on the recording FM signal and recorded on the magnetic tape 4 by the magnetic head 2 using the recording amplifier 20. As shown in FIG. 1, the single frequency pilot signal written on the adjacent track on the magnetic tape 4 read by the sub magnetic head 3 is amplified by the regenerative amplifier 5, and only the pilot signal is extracted by the bandpass filter 6. The signals are set and shaped to the same appropriate level by the level adjuster 7, superimposed on the recording FM signal by the adding circuit 8, and recorded on the magnetic tape 4 by the magnetic head 1 via the recording amplifier 9.

A block diagram of the reproducing circuit is shown in FIG. During reproduction, the main signal and pilot signal reproduced by the magnetic head 1 are amplified by a regenerative amplifier 10.
Only a pilot signal is extracted from this signal by a bandpass filter 11, and its phase is compared by a phase comparator 12 with a pilot signal of an adjacent track also detected by the sub magnetic head 3.
In the reproducing circuit shown in FIG. 4, when there is no track deviation, the phases of the two signals input to the phase comparator 12 can be made the same. Therefore, the output of the phase comparator 12 can be set to 0 when there is no track deviation. If a track shift occurs during reproduction, the phases of these two pilot signals change.
This will be explained based on FIG. If during recording, the pilot signal is detected by sub magnetic head 3 and simultaneously recorded by magnetic head 1 without any time delay, and if there is no track shift during playback, the magnetic signal will not be affected by changes in the scanning speed during recording or playback. Head 1 and sub-magnetic head 3 reproduce pilot signals in the same phase as shown in FIG. However, if the relative positions of the magnetic heads 1 and 3 and the recording track are shifted in the track width direction by δ in the direction shown in the figure as shown by the broken line in FIG. The detection phase of
If the scanning speed is _VH , then the delay is δtanθ/ _VH , and the pilot signal reproduced by magnetic head 1 is δtanθ/VH _.
Therefore, a time lag of 2δtanθ/V _H occurs in both pilot signals. The number assigned to this amount of deviation changes as the direction of δ changes, so the magnitude and direction of the amount of deviation δ can be determined from the phase difference between the two pilot signals. Therefore, by controlling the relative position of the magnetic head and tape using the detection output of the phase comparison circuit and setting the detection output to 0, mistracking can be prevented. Furthermore, if the recording set and reproduction set are different, as in the case of compatible playback of a recorded tape, a phase difference will occur even in the correct tracking state due to the difference in the relative position of magnetic head 1 and sub-magnetic head 3, but this is fixed. This can be corrected by adjusting the phases of both pilot signals at the start of compatible playback.

The method of recording the pilot signal is not limited to that shown in FIG. 1, but it is also possible to record the pilot signal on the entire track at one frame intervals, as shown in FIG. In this case, since the sub magnetic head 3 reproduces pilot signals of tracks with different azimuths during reproduction, a sufficient D/U value is required.
In the examples shown in FIGS. 1, 2, and 9, there is only one sub magnetic head 3, and the sub magnetic head 3 is tracked only during the period when the magnetic head 2 is scanning the tape, or every 4 fields in the example shown in FIG. No deviation signal is detected. However, the amount of track deviation does not change much between adjacent tracks, and even if track deviation information for the immediately preceding field is held during a period in which no track deviation signal is detected, no significant error will occur.

Of course, a new sub-auxiliary head 21 having the same azimuth as the magnetic head 1 can also be placed near the magnetic head 2. The recording pattern at this time is number 10.
As shown in the figure. In this case, the pilot signal recorded by magnetic head 1 in FIG. In addition to the pilot signal recording described in FIG. 1 in the head 1, a new pilot signal is recorded at a spatially different location, and this recorded pilot signal is reproduced in the sub magnetic head 21, and in synchronization with this, the magnetic A new pilot signal may be recorded in head 2.

The pilot signal must be selected so as not to adversely affect the main signal in terms of space or frequency. For example, in an image signal recording and reproducing device that employs a low-frequency conversion method for color signals, the pilot signal frequency is either near the boundary between the luminance signal and color signal bands (usually around 1MHz), or the color signal has an even lower frequency range (usually around 100KHz). ) is preferred. As a spatial means, it is preferable to record the pilot signal in a vertical blanking area where the main signal does not appear on the screen or in a horizontal blanking area.

Further, in the arrangement shown in FIG. 2, the sub magnetic head 3 can be used as a reproducing head for so-called field still reproduction. This is possible by repeatedly reproducing the same track using the magnetic heads 2 and 3 when the magnetic tape is stopped using the reproduced FM signal shown in FIG.

The embodiment shown in FIGS. 1 and 2 is an embodiment in which the field still reproduction described above is also possible, but when the sub magnetic head 3 is not used for field still reproduction, the sub magnetic head 3 is moved to an adjacent track as shown in FIG. If the center of the track is scanned, pilot signals of adjacent tracks can be detected with even better S/N ratio. In this case, it is also possible to record the pilot signal over the entire track.

Although it is possible to correct the track deviation by detecting the track deviation signal and controlling the running speed of the magnetic tape 4, it is also possible to directly move the magnetic head in the track width direction to correct the track deviation. be. An example in this case is shown in FIG. The recording pattern diagram of this embodiment is the same as FIG. 6.
A block diagram of the control circuit of this embodiment is shown in FIG. The output of the phase comparator 12 in FIG.
3 sets the gain and polarity, the phase compensation circuit 22 compensates the characteristics as a servo loop, and the electromechanical transducer 1 passes through the drive amplifier 14.
5 and 16, and serves to correct track deviation. The electromechanical transducer currently in practical use is a piezoelectric bimorph plate, but other types such as a displacement device using electromagnetic force may also be used. Also, as shown in Figure 7, the sub magnetic head is
If only one track shift signal is used, the shift signal for the field period when magnetic head 1 is scanning the tape can be delayed by one field, and that signal can be used as is during the period when magnetic head 2 is scanning the tape. .

In addition, when performing so-called field still reproduction in this embodiment, for example, during reproduction, the magnetic tape 4 is stopped at a position as shown in FIG. During the period when the head 2 scans the magnetic tape 4, the signal applied to the electromechanical transducer 15 is delayed by one field and applied to the electromechanical transducer 16, and a bias voltage is applied to the electromechanical transducer 16 by an amount corresponding to the pitch between adjacent tracks. The signals may be applied to the electromechanical transducer 16 at the same time. Alternatively, the stop position may be set at a position where the magnetic head 2 correctly reproduces the track, and a bias voltage may be applied to the electromechanical transducer 15 so that the sub magnetic head 3 correctly reproduces the track. In the embodiment shown in FIG. 7, one sub magnetic head is used, but it is obvious from the above description that two sub magnetic heads can be used to constantly obtain a track deviation signal.

FIG. 11 shows an embodiment of the magnetic disk recording/reproducing apparatus of the present invention. In the case of a magnetic disk device, unlike a two-head helical scan VTR, the magnetic head is always in contact with the disk in a state capable of recording and reproducing data, so two magnetic heads 3 with different azimuths are used.
It is possible to operate with only 1 and 32. The signal recording and reproducing method is almost the same as in the above-described embodiment of the helical scan VTR. That is, when the main signal is recorded by the recording/reproducing magnetic head 32 during recording, the recording track 34 that has already been recorded by the sub magnetic head 31 is
A pilot signal synchronized with the reproduced track deviation detection pilot signal is multiplexed with the main signal and recorded on the track 35 by the recording/reproducing magnetic head 32. During reproduction, the radial positions of the sub magnetic heads 31 and 32 with respect to the disk 33 are controlled based on the phase difference between the track deviation detection pilot signals reproduced from both the sub magnetic head 31 and the recording/reproducing magnetic head 32. Continue signal to disk 33
In order to record on another track, the sub magnetic head 31 is moved onto the recording track 36 and the recording/reproducing magnetic head 32 is moved onto the recording track 37, and recording is performed in the same manner as on the recording tracks 34 and 35. . The reproduction operation is also similar to that for the recording tracks 34 and 35. The track deviation detection pilot signals to be recorded on the recording tracks 34 and 36 may be recorded in advance, including on other recording tracks, when the disk 33 is initialized. In addition, with this method, no track deviation signal is generated when a part of the recorded signal is rewritten, but this is because before recording, the track deviation signal for one rotation is detected once in playback mode, and this is memorized and recorded. Sometimes, by correcting the track deviation based on this, it becomes possible to rewrite part of the track. This method combines both azimuth recording and autotracking, and is suitable for high-density recording methods in magnetic disk devices. It is applicable to a floppy disk device for recording and reproducing digital data and a random access device for recording one-frame images.

According to the present invention, accurate tracking can be performed reliably even with a very narrow recording track width in an azimuth recording type magnetic recording/reproducing apparatus. Therefore, a very high-density magnetic recording/reproducing device can be realized, and moreover, only one type of pilot signal frequency is required, and the circuit can be manufactured at low cost. Furthermore, as described in the main text, the sub magnetic head for detecting tracking errors can be used for other purposes, and can be useful for improving functionality.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing a recording pattern on a tape according to an embodiment in which the present invention is applied to a helical scan VTR, Fig. 2 is a plan view showing the magnetic head arrangement of the embodiment, and Fig. 3 is a recording of a pilot signal. FIG. 4 is a block diagram showing a pilot signal regeneration circuit, FIG. 5 is a schematic diagram explaining the reason for generation of the track error signal of the present invention, and FIG. 6 is another embodiment of the present invention. FIG. 7 is a plan view showing a magnetic head portion of still another embodiment of the present invention; FIG. 8 is a block diagram showing a control circuit of the embodiment shown in FIG. 7; 9
10 is a schematic diagram showing a recording tape pattern according to still another embodiment of the present invention. FIG. 11 is a schematic diagram showing a recording tape pattern according to still another embodiment of the present invention.
The figure is a plan view showing an example of a recording pattern of an embodiment in which the present invention is applied to a magnetic disk recording/reproducing device. 1, 2, 32... recording/reproducing magnetic head, 3, 21,
31... Sub magnetic head, 4... Magnetic tape, 33
... Magnetic disk, 17 ... Oscillator, 12 ... Phase comparator, 15, 16 ... Electromechanical conversion element.

Claims (1)

[Scope of Claims] 1. In a magnetic recording/reproducing apparatus that records data by changing the azimuth of adjacent recording tracks, in the vicinity of at least one recording/reproducing magnetic head,
A sub magnetic head with a different azimuth from this recording/reproducing magnetic head is arranged, and during recording, a pilot signal for detecting a track deviation of an adjacent track that has already been written in the sub magnetic head is reproduced, and in synchronization with this, the recording/reproducing magnetic head is The head records the main signal and the pilot signal for detecting track deviation, and during playback, the pilot signal for detecting track deviation of the adjacent track reproduced by the sub magnetic head and the track deviation detection signal reproduced by the recording/reproducing magnetic head are recorded. Detecting the phase difference of the track deviation detection pilot signal detected from the track being scanned by the remagnetic head,
A magnetic recording/reproducing device characterized in that the relative position of a recording medium and a magnetic head is controlled by this phase difference. 2. The magnetic recording/reproducing device is a two-head helical scan type VTR, with recording/reproducing magnetic heads arranged at 180° intervals and having different azimuths, and at least one recording/reproducing magnetic head placed close to the other recording/reproducing head. 2. The magnetic recording and reproducing apparatus according to claim 1, further comprising a sub-magnetic head having the same azimuth as the magnetic head. 3 A recording/reproducing magnetic head and a sub magnetic head placed close to it are mounted on the same electromechanical transducer, and other magnetic heads are mounted on other electromechanical transducers, so that they are aligned in the direction of the rotation axis. 3. The magnetic recording and reproducing device according to claim 2, wherein the magnetic recording and reproducing device is configured to be displaced. 4. The magnetic recording and reproducing apparatus according to claim 1, wherein the pilot signal is not recorded over the entire area between adjacent recording tracks, but is recorded intermittently. 5. Claim 4, characterized in that a pilot signal is recorded in the vertical blanking interval, the horizontal blanking interval, or both of the video signal.
The magnetic recording and reproducing device described in .