JPS63122043A - Tracking control method - Google Patents

Abstract

PURPOSE:To contrive the simplification of a circuit constitution by only recording the pilot signal of a single frequency so as to apply the tracking control to which plural reproducing heads reproduces the signal of a predetermined system in reproducing an information signal. CONSTITUTION:The inputted video signal of one field is divided into four systems by a recording digital signal processing circuit 11 and outputted while being shifted by a 1/4 field period. A reference oscillator 13 generates a reference signal giving a pilot signal frequency, the signal is inputted to a phase comparator 15 to which the phase is compared with the phase of the output of a voltage controlled oscillator 16 and the comparison output controls the oscillator 16. Moreover, the wavelength of the frequency of the reference signal is selected to be one integer-th number to that of the shift quantity of the adjacent track and in supplying the signal of the frequency to each head at the same phase, the phases on the tape are coincident between tracks. Thus, the tracking control is applied depending on the phase of a reproduced reference signal at reproduction. Thus, the circuit constitution is simplified.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a tracking control method, and in particular, for a large number of tracks parallel to each other on a recording medium, tracking is performed every n tracks (n
The present invention relates to a tracking control method in a system in which information signals of a plurality of systems are recorded so that information signals of the same system are arranged in the integer of 2 or more, and the information signals are reproduced from the recording medium.

[Conventional technology]

In recent years, it has become common to digitize various information signals and record and reproduce them in the above-mentioned systems. On the other hand, the band of a digitized information signal is extremely wide compared to that of an analog information signal, and as a result, it becomes necessary to perform high-density magnetic recording, and for example, the track pitch is also wide (impossible).

On the other hand, if a tracking error occurs during reproduction of a digital information signal, the probability of code error occurrence increases significantly. Although it is possible to correct this with a so-called error correction code, it is not preferable to improve the correction ability of the error correction code because it increases redundancy. Therefore, improving the tracking accuracy in this type of system is a major theme.

On the other hand, as a conventional tracking control method in this type of system, a control signal (CTL) with a frequency corresponding to the track pitch is sent to the end of a tape-shaped recording medium.
) is recorded with a fixed head, and the tracking error signal is obtained by reproducing this and comparing the phase with a reference signal (CT
L method), pilot signals having four different frequencies are sequentially recorded on each track by being superimposed with an information signal, and during playback, tracking is performed by comparing the levels of pilot signals reproduced from both adjacent tracks of the control target track. A method of obtaining an error signal (four-frequency method), etc. has been used.

[Problem that the invention seeks to solve]

However, in the CTL method, tracking control is not performed based on information obtained from the recording track, so for example, if the linearity of the track is impaired, or if the CTL playback head is installed incorrectly. Therefore, accurate tracking control signals may not be obtained.

Although the four-frequency system can solve the problems of the CTL system, it ends up limiting the band of the information signal because four types of pilot signals are superimposed on the information signal. Particularly in the case of digital signals, the lower end of the recording band extends to about 100 KHz, so it is impossible to superimpose as many as four different frequencies.

Furthermore, when recording information that has a large amount of information per unit time, such as a video signal, it is difficult to record it as a single digital signal, so it is necessary to convert it into a multichannel system, and divide the video signal for one field into multiple tracks. and are being recorded. In this case, it is necessary to determine which system of video signals is recorded on the track at the time of reproduction, and if this is not possible, it is impossible to recombine the divided video signals. When determining the recorded system, it is desirable to reproduce the video signal divided into n systems by dedicating n reproducing heads to each of them, since this eliminates the need for various switching circuits in the circuit configuration.

In this case, the n playback heads must be controlled to reliably trace only the track in which the desired system of video signals is recorded.

Further, even if the number of heads is n/i (i is an integer), if there are a plurality of heads, the track to be traced by each head, that is, the system to be reproduced must always be a determined system.

For example, in the above-mentioned CTL method, this can be achieved by recording a CTL with n track pitch periods, but in the case of the above-mentioned 4-frequency method, it can only cope with one of the cases where n = 4.2. .

The present invention has been made in view of the above-mentioned problems, and is based on n (n≧2)
When reproducing information signals from a recording medium in which information signals of a system are recorded cyclically at n-track cycles, tracking control is performed using a single frequency so that multiple playback heads can each play back a windowed system of signals. The purpose of the present invention is to provide a tracking control method that can be realized simply by recording pilot signals of .

[Means for solving problems]

For this purpose, in the tracking control method of the present invention, information signals of the same system are arranged every n tracks (n is an integer of 2 or more) for a large number of parallel tracks on a recording medium. In a system for recording multiple systems of information signals and reproducing the information signals from the recording medium, the phases of both adjacent tracks are opposite to the phase of the control target track in the plurality of trunks. A single-frequency pilot signal shifted by the same amount in the direction is recorded together with an information signal in a recording pattern of nXi ) rack periods (i is an integer), and when the information signal is reproduced, tracking control is performed based on the phase of the reproduced pilot signal. The system is configured to do this.

[Operation] With the above-described configuration, a plurality of playback heads can each trace only the track to be played so that one of the n adjacent tracks can be specified as the track to be controlled. Tracking control can be performed.

〔Example〕

Hereinafter, the present invention will be explained in detail using examples.

Fifth (A) and (B) are diagrams showing the head configuration of a digital VTR as an embodiment of the present invention. In the figure Ha,
Hb, Hc, and Hd are rotating video heads, and are mounted on the cylinder 1 with a phase difference of 90° from each other. Further, the head Ha and the head Hc each have an azimuth angle of +00, and the head Hb.

It is assumed that the heads Hd each have an azimuth angle of -θ0.

Further, the magnetic tape 2 is wound around the cylinder 1 over an angular range of 180' or more, and the magnetic tape 2 is wound around the cylinder 1 over an angular range of 180' or more.
The digital video signal for one field is sent to heads Ha and H.
It is assumed that recording is performed on four tracks formed by b, He, and Hd. Therefore, at this time, the cylinder 2 rotates at 600 revolutions per second, and each track is formed in 1/120 second.

Figures 1 (A) and (B) show the digital V in this embodiment.
FIG. 3 is a diagram for explaining a recording pattern by TR. In FIG. 1(A), each head Ha, Hb.

Hc, Hd shall be traced on the tape 2 in the direction shown by arrow 3, and pi, p2 . p3. p4 is 9 to each other
0' indicates pilot signals having different phases, and the frequency of this pilot signal is a single frequency of about 50 KHz. By the way, the phase of each pilot signal here is the phase on tape 2, and if the phases of adjacent tracks are shifted by 90°, the playback phase will shift by 90' when they are played back with the same head. Indicates that. FIG. 1(B) shows pi, p2. p3. p
FIG. 4 is a diagram showing the phase relationship of No. 4 as a vector.

Next, the principle of tracking control according to this embodiment will be explained using FIGS. 2(A) and 2(B). Now, Figure 2 (A
), when the pilot signal recorded on the control target track is pi and the pilot signals recorded on both adjacent tracks are p2 and p4, the head is in just track state with respect to the control target track. If so, the composite phase vector of the pilot signal reproduced from the head matches pi. On the other hand, when the head deviates from the control target track to the track where p2 is recorded, the composite phase of the reproduced pilot signal changes as shown in Pml in FIG. When the signal is shifted toward the track that is currently being played, the composite phase of the reproduced pilot signal changes as shown by Pm2 in FIG. 2(B).

FIG. 3 is a diagram showing the schematic configuration of the digital VTR of this embodiment, and FIG. 4 is a timing chart showing the waveforms of the part numbered in FIG.

First, the video signal input from the terminal 10 is digitally processed by the recording digital signal processing circuit 11, and the video signal of one field is divided into four systems of digital signals, each having a period of 174 fields (1/240 seconds). Output at the shifted timing. The reference oscillator 13 generates a reference signal giving the frequency of the pilot signal, and this reference signal is supplied to the phase comparator (PC) 15 via the R side of the switch 14. In the PCl5, the output signal of the voltage controlled oscillator (VCO) 16 and the reference signal are phase-compared, and this comparison output is passed through the low-pass filter (LPF).
) 17 and the R side of switch 18 to control the vCO.

By the way, the frequency of this reference signal is set to have a wavelength that is an integral fraction of the amount of shift of adjacent tracks due to diagonal track formation, and an integral multiple of 240Hz. If a signal of the same frequency as the reference signal is supplied with the same phase, the phases on the tape 2 will all match between the tracks.

Delay circuit (DL) 19. 20. 21 is for shifting the input signal by 1/4 wavelength of the reference signal, and these outputs have a phase shifted by 90°, 180°, and 270', respectively, with respect to the output signal of the VCO 16, and When the output of C016 is the pilot signal pi, the outputs of DL19 and 20.21 are respectively p2. p3°p4.

The four-phase PG generator 25 generates signals for each head Ha and Hb based on the rotational phase of the rotary cylinder 5 in FIG. 5(A).

Figure 4 (a), (b), (c) shows four types of phase pulses (PG) that indicate the recording and reproducing timing of Hc and Hd.
This occurs as shown in (d). 26 is an 8-multiplier such as a PLL, which generates a signal having a frequency eight times that of PG (as shown in FIG. 4(e)). This signal (e) is the switch 22゜2
3.24, and as a result, the pilot signal that is output from switch 22 eight times while one track is formed is switched between pl and p2, and similarly output from switch 23.24. The pilot signals to be used are pi and p
3. They can be switched between pi and p4, respectively.

The aforementioned four systems of digital signals are received by the mixer 12a.

12b, 12c, and 12d, respectively, are mixed with the pilot signals generated as described above, and the signals are mixed with the pilot signals generated as described above by switches 27a and 27.
b.

H side of 27c, 27d and switches 28a, 28b
, 28c.

The signals are recorded by the heads Ha, Hb, Hc, and Hd via the head 28d. Switches 28a, 28b, 28c, 28d
are turned on and off by the aforementioned PGs (a), (b), (c), and (d), respectively.

Through the process described above, a single frequency pilot signal having a phase as shown in FIG. 1(A) is recorded together with the digital video signal.

Next, the operation of the apparatus of this embodiment during reproduction will be explained.

Switches 27a, 27b, 27c, and 27d are connected to the P side, respectively, and each head Ha, A reproduced signal is obtained from Hb, Hc, and Hd. These four systems of reproduction signals are supplied to a reproduction digital signal processing circuit 29, where the original video signal is restored and outputted from a terminal 30 as a reproduction video signal.

On the other hand, the reproduction signals of the four systems go through BPFs 31a and 31b, respectively.

31c and 31d, and the pilot signal components are separated and
be done. Here, as is clear from FIG. 1(A), the area al
, a3. a5. The pilot signal reproduced from a7 is always pl. On the other hand, when the pulse signal (e) output from the 8-multiplier 26 is at a high level, each head Ha, Hb, Hc, Hd is in the area al, a3° a5 . Since we will trace a7, at this time switch 32a
.

If 32b, 32c, and 32d are connected to the H side, the adder 33
The pilot signal input to is pl.

Therefore, the pilot signal output from the adder 33 is the pl reproduced by the two heads tracing on the tape.
This is the average signal of . The output of this adder 33 is converted to PCl5. LP
F17. The signal is smoothed by supplying it to a PLL circuit consisting of a VCO 16. However, in PCl5, only the error signal that is being reproduced in the area where the pilot signal pl is reproduced is valid, so this is sent to the sample and hold circuit (S/H).
) The sample is held at 35. This allows VC
From O16, a reference signal of pl with smoothed out position variations for the installation of the four heads, and from DLL9.20.21, p2, p3. A reference signal of p4 will be obtained.

On the other hand, from the L side terminals of the switches 32a, 32b, 32c, and 32d, the heads Ha, Hb, Hc, and Hd are in the area a2°a.
4. a6. A pilot signal separated from the reproduced signal tracing a8 is output. The phase of this pilot signal changes depending on the track deviation with respect to the control track. Now, the phase of each pilot signal is shown in Figure 1 (B
), when each head deviates to the right in Figure 1 (A) with respect to the control target track, the phase of the reproduced pilot signal rotates clockwise, and when it deviates to the left, it rotates counterclockwise. Rotate to .

Therefore, in the PCs 34a, 34b, 34c, and 34d, a tracking error signal is obtained by comparing the phases of the pilot signal of the control target track and the reproduced pilot signal. However, in this case, each head Ha, Hb.

Hc and Hd are respectively in the area a2. a4. a6. Since only the error signal tracing a8 is valid, the signal indicating this timing (Fig. 4 (f), (g), (h)
.

(shown in (i)) is connected to the inverter 35. anime) 36
a.

36b, 36c, and 36d, and the gate 37a
.

37b, 37c, and 37d. As a result, only valid tracking error signals are input to the adder 38, and the output of the adder 38 is supplied to the capstan control circuit 40 via the LPF 39. The capstan control circuit 40 controls the running of the tape 2 by the capstan 41 and the pinch row 42 in a direction that compensates for the track deviation.

In the digital VTR of the above-described embodiment, tracking control can be performed simply by superimposing a pilot signal of a single frequency, so that a wide band of digital video signals can be obtained. Furthermore, since the reference phase for forming this error signal is obtained based on signals reproduced from various positions in the width direction of the tape, the influence of jitter on the tracking error signal during reproduction by the rotating head can be kept to a minimum. I can do it. Further, since the phase of the pilot signal recorded on the control target track of each head is always the same, the configuration of the switching circuit system when configuring the circuit can be simplified. Furthermore, since the tracking error signal is formed using the reproduction signals of all the heads, it is possible to deal with variations in the mounting position of each head, and it is possible to obtain an extremely good tracking control signal.

Note that the tracking control method of the present invention is not limited to the arrangement of pilot signals in the above embodiments,
Other arrangements are also possible.

Figures 6 to 8 each show four I-field video signals.
FIG. 7 is a diagram showing another example of the arrangement of pilot signals in the case of dividing and recording into four tracks as a system signal. In the figure pi, p2. p3. The meaning of p4 is the same as that in FIG. 1(A), and the shaded area indicates that no pilot signal is recorded.

The recording pattern shown in Figure 6 is always at the bottom end of each track.
l, and p in the other part that occupies most of the track.
t, p2. p3. p4 is recorded cyclically for each track. Considering that tracking control is performed using the recording pattern described above, a reference pilot signal is formed by the PL reproduced from the lower end of each track, and a pilot signal reproduced from other parts and this reference pilot signal are generated. Tracking control will be performed based on the phase difference between the two. In this case, compared to the recording pattern shown in FIG. 1(A), the reliability of the phase of the reference pilot signal at the upper end of the track is lower, but the tracking control signal can be obtained from almost the entire area of the track. Therefore, it is suitable for tracking tracks with degraded linearity.

In the recording pattern shown in FIG. 7, one track in every four tracks records a pilot signal at the bottom end of each track, and pl is recorded in the other parts as in the case of FIG.

p2. p3. Record p4 cyclically. In this case p
A reference pilot signal is formed only from the reproduced signal from the lower end of the track where i is recorded, and tracking control is performed based on the phase difference between the pilot signal reproduced from other parts and this reference pilot signal. In this pattern, the reliability of the phase of the reference pilot signal decreases on the track where p4 is recorded, but each head records only one type of pilot signal, compared to the example in Figure 6. This greatly simplifies the circuit configuration.

In Fig. 8, the tracks that can be controlled targets are T, ,T
2. T3. T4. TIs, which exist every two tracks as shown in the figure. Only pl is recorded on the control target track, and areas a2, a4, . a6.
a8 has p2. p4 is recorded. That is, the area al of the head where the control target track is to be traced.

a3. a5. A reference pilot signal is formed by the regenerated pilot signal from s7, and this and area a2. a
4. a6. This is intended to obtain a tracking control signal based on the phase difference with the reproduced pilot signal from a8.

However, in this case, since the direction of the tracking error signal is reversed for each control target track, the tracking error signal must be appropriately inverted using an inverting amplifier or the like.

In all the embodiments so far, one field of video signal is
Although the embodiment has been described in which recording is divided into two tracks, the number of divided tracks, that is, the number of information signal systems can be set arbitrarily, and the following six information signal systems are cyclically recorded. The recording pattern when recording in the 9th
This will be explained using FIGS. 1 and 10 as examples.

In Figure 9, pi', p2', p3'
, p4'.

p5/ and pe/ indicate six pilot signals whose phase difference on the recording medium is 60° from each other. 9th
The recording pattern shown in the figure is such that a pilot signal of pI' is recorded at the bottom end of each track, and the pilot signal pl' is reproduced from the bottom end of the track where the pilot signal is recorded.
is used to form a reference pilot signal, and tracking control is performed in the same manner as in the case of FIG. Even if the phase difference between the pilot signals between adjacent tracks is 60 degrees as in this example, tracking control can be performed in the same way, although the S/N is lower than in the case of 90 degrees.

Furthermore, even when recording six systems of information signals cyclically, the above-mentioned pi, p2. p3. This can be done with p4. An example of the recording pattern is shown in FIG.

In the recording pattern shown in FIG. 10, each track is divided into ten areas a1 to alO in the width direction of the tape, and control target tracks are every three tracks as shown by Ta, Tb, and Tc. In this pattern, the period of the recording pattern of the pilot signal is six track periods, which is suitable for recording a digital video signal using six heads.

〔Effect of the invention〕

As explained above, according to the present invention, n
When a recording medium in which information of a system (n≧2) is recorded is played back by multiple heads, each head can trace the information signal of the desired system in a good tracking state, and switching circuits etc. The circuit configuration can be simplified.

In addition, the pilot signal to be recorded only needs to be of a single frequency (this does not limit the band of the information signal to be recorded.Furthermore, the phase difference of the pilot signal between adjacent tracks can be set arbitrarily, so the information signal It is possible to arbitrarily set the number of systems.

[Brief explanation of the drawing]

FIGS. 1(A) and (B) are diagrams showing recording patterns by a digital VTR as an embodiment of the tracking control method of the present invention, and FIGS. 2(A) and (B) are diagrams showing recording patterns in the embodiment of the present invention. FIG. 3 is a diagram showing a schematic configuration of a digital VTR as an embodiment of the present invention. FIG. 5 (A) and (B) are diagrams showing the head configuration of a digital VTR as an embodiment of the present invention,
FIGS. 6 to 10 are diagrams showing other examples of the phase arrangement of pilot signals on the tape, respectively. In the figure, 2 is a magnetic tape as a recording medium, 11 is a recording digital signal processing circuit, 12a, 12b, 12
c. 12d is an adder, 13 is a reference oscillator, 16 is a voltage controlled oscillator, 19. 20. 21 are delay circuits, 22
゜23 and 24 are switches, 25 is a 4-phase PG generator,
26 is an 8-multiplier, 29 is a reproduction digital signal processing circuit,
34a, 34b, 34c, 34d are phase comparators, 38 is an adder, 40 is a capstan control circuit, 4
1 is a capstan, a1 to alo are areas into which the track is divided, pi, p2. p3. p4 are respective pilot signals. Figure 6 Figure 7 Figure 8

Claims (1)

[Claims] Multiple systems of information signals are recorded on a large number of parallel tracks on a recording medium so that the same system of information signals is arranged every n tracks (n is an integer of 2 or more), and the information is transferred from the recording medium. In a system for reproducing signals, a pilot signal of a single frequency is transmitted to n×i tracks in which the phases of both adjacent tracks are shifted by the same amount in opposite directions with respect to the phase of the control target track among the plurality of tracks. A tracking control method in which a recording pattern of a period (i is an integer) is recorded together with an information signal, and when the information signal is reproduced, tracking control is performed based on the phase of a reproduced pilot signal.