JPH077540B2 - Tracking control method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tracking control method, and particularly to a plurality of tracks arranged in parallel on a recording medium, every n tracks (n tracks).
Relates to a tracking control method in a system in which information signals of a plurality of systems are recorded so that the information signals of the same system are arranged in an integer of 2 or more) and the information signals are reproduced from the recording medium.

[Conventional technology]

In recent years, various information signals have been digitized, and recording / reproduction has been frequently performed in the system as described above. On the other hand, the band of the digitized information signal is extremely wider than that of the analog information signal, and accordingly, it is necessary to perform high-density magnetic recording or the like, and, for example, the track pitch cannot be widened.

On the other hand, if a tracking error occurs during reproduction of the digital information signal, the probability of occurrence of code error increases significantly. Although this may be corrected by using a so-called error correction code or the like, it is not preferable to improve the correction capability 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) having a frequency corresponding to the track pitch at the end of the tape-shaped recording medium is used.
Is recorded at a fixed head, and is reproduced to obtain a tracking error signal by phase comparison with a reference signal (CTL method). A pilot signal having four different frequencies is sequentially recorded as an information signal for each track. A method (four-frequency system) has been used in which a tracking error signal is obtained by superimposing recording and comparing the reproduced pilot signal levels from both adjacent tracks of the control target track during reproduction.

[Problems to be solved by the invention]

However, in the CTL system, tracking control is not performed based on the information obtained from the recording track, so if, for example, the linearity of the track is impaired, or due to an error in mounting the CTL playback head, etc. An accurate tracking control signal may not be obtained.

Further, in the 4-frequency system, the problem of the CTL system can be solved, but since four kinds of pilot signals are superimposed on the information signal, the band of the information signal is limited. Especially in the case of digital signals, the lower end of the recording band is 10
Since it extends to about 0 KHz, it is impossible to superimpose four kinds of frequencies.

Further, for example, when recording information having a large amount of information per unit time such as a video signal, it is difficult to record it as a digital signal of one system, and it is converted into a multichannel, for example, a video signal for one field is divided into a plurality of tracks. It is being divided and recorded. In this case, it is necessary to determine which system of video signal is recorded in the track at the time of reproduction, and if this is not possible, it is impossible to recompose the divided video signals. When discriminating the recorded system, it is desirable to reproduce the video signals divided into n systems by dedicating n reproduction heads, respectively, in the sense that various switching circuits are not required as a circuit configuration.

In this case, the n reproducing heads must be controlled so as to reliably trace only the track on which the video signal of the desired system is recorded.

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

This can be realized, for example, by recording the CTL of n track pitch cycles in the above-mentioned CTL method.
In the case of the frequency system, the number of systems n is an integer fraction of 4, that is, n
= 4 or 2 can be dealt with only.

The present invention has been made in view of the above problems, and n (n ≧ 2)
When the information signal is reproduced from the recording medium in which the information signal of the system is cyclically recorded at the n track cycle, a plurality of reproduction heads are used for tracking control so that the signals of the specified system can be reproduced. It is an object of the present invention to provide a tracking control method which can be realized only by recording a pilot signal.

[Means for solving problems]

For such a purpose, in the tracking control method of the present invention, information signals of the same system are arranged for every n tracks (n is an integer of 2 or more) for a number of tracks arranged in parallel on the recording medium. In a system for recording a plurality of systems of information signals and reproducing the information signals from the recording medium,
A pilot signal of a single frequency in which the phases of both adjacent tracks are shifted in the opposite directions by the same amount with respect to the phases of the control target tracks in the plurality of trunks is transmitted in n × i track periods (i is an integer of 1 or more). A recording pattern is recorded together with an information signal, and when reproducing the information signal, a reference signal indicating the phase of the pilot signal to be reproduced from the control target track is formed, and the phase of the reference signal and the actually reproduced pilot signal. The tracking error signal is formed based on the difference between the tracking error signal and the phase, and tracking control is performed according to the tracking error signal.

[Work]

With the above-described configuration, tracking control is performed so that a plurality of reproduction heads trace only the tracks to be reproduced so that the control target track can be defined as one of the adjacent n tracks. be able to.

〔Example〕

 Hereinafter, the present invention will be described in detail with reference to examples.

Fifth (A) and (B) are diagrams showing the head structure of a digital VTR as an embodiment of the present invention. Ha, Hb, Hc, Hd in the figure
Are rotating video heads, each on cylinder 1
It is installed with a 90 ° phase difference. Also head
Ha and head Hc each have an azimuth angle of + θ °, and head H
b and head Hd each have an azimuth angle of -θ °.

The magnetic tape 2 is wound around the cylinder 1 over an angle range of 180 ° or more, and a digital video signal for one field is sent to the heads Ha, Hb, Hc, H while the cylinder 2 makes one revolution.
It shall be recorded on the four tracks formed by d. Therefore, at this time, the cylinder 2 rotates 60 times per second, and each track is formed in 1/120 second.

FIGS. 1A and 1B are digital VTs in this embodiment.
It is a figure for demonstrating the memory pattern by R. First
In the figure (A), each head Ha, Hb, Hc, Hd shall be traced on the tape 2 in the direction shown by the arrow 3, and p1, p2,
p3 and p4 represent pilot signals whose phases differ by 90 ° from each other, and the frequency of these pilot signals is a single frequency of about 50 KHz. By the way, here, the phase of each pilot signal is the phase on the tape 2, and when the phase is shifted by 90 ° in the adjacent track, when they are reproduced at the same head, the reproduction phase is shifted by 90 °. Indicates that FIG. 1 (B) is a diagram showing the phase relationship of p1, p2, p3, and p4 as a vector.

Next, the principle of tracking control according to this embodiment will be described with reference to FIGS. 2 (A) and 2 (B). When the pilot signal recorded in the control target track is p1 and the pilot signals recorded in both adjacent tracks are p2 and p4 as shown in FIG. 2 (A), the head is the control target track. On the other hand, in the just-track state, the combined phase vector of the pilot signal reproduced from the head coincides with p1. On the other hand, when the head deviates from the control target track to the track on which p2 is recorded, the composite phase of the reproduction pilot signal is shown in FIG. 2 (B).
When it changes like Pm ₁ and shifts to the track where p4 is recorded, the composite phase of the playback pilot signal is shown in Fig. 2 (B).
Change like Pm ₂ in.

FIG. 3 is a diagram showing a schematic configuration of the digital VTR of the present embodiment, and FIG. 4 is a timing chart showing waveforms of respective portions in FIG.

First, the video signal input from the terminal 10 is digitally processed by the recording digital signal processing circuit 11, and the one-field video signal is divided into four digital signals, which are 1/4 field period (1/240 seconds) each. It is output at the shifted timing. The reference oscillator 13 generates a reference signal that gives 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 PC 15, the output signal of the voltage controlled oscillator (VCO) 16 and the reference signal are phase-compared, and the comparison output controls the VCO via the low-pass filter (LPF) 17 and the R side of the switch 18.

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

The delay circuits (DL) 19, 20, and 21 respectively input the input signal to 1 / of the reference signal.
It is for shifting by 4 wavelengths, and these outputs are VCO
The output signals of 16 are shifted by 90 °, 180 ° and 270 ° respectively, and the output of VCO16 is changed to pilot signal p1.
Then, the outputs of DL19, 20, and 21 are p2, p3, and p4, respectively.

The 4-phase PG generator 25 is the rotary cylinder 5 in FIG. 5 (A).
As shown in FIGS. 4 (a), (b), (c) and (d), four kinds of phase pulses (PG) indicating the recording / reproducing timing of each head Ha, Hb, Hc, Hd based on the rotation phase of Occur.
Reference numeral 26 is an 8-multiplier such as a PLL, which generates a signal (shown in FIG. 4 (e)) having a frequency eight times that of PG. This signal (e) controls the switches 22, 23 and 24 so that the pilot signal output from the switch 22 eight times during the formation of one track is switched between p1 and p2. , Similarly, the pilot signals output from the switches 23 and 24 are p1 and p3, p1.
Can be switched between p4 respectively.

The above-mentioned 1-system digital signal is mixed in the mixers 12a, 12b, 12c,
12d is mixed with the pilot signals generated respectively as described above, and recorded at the heads Ha, Hb, Hc, Hd via the R side of the switches 27a, 27b, 27c, 27d and the switches 28a, 28b, 28c, 28d, respectively. It The switches 28a, 28b, 28c and 28d are the aforementioned PGs, respectively.
It is turned on / off by (a), (b), (c) and (d).

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

Next, the operation of the apparatus of this embodiment during reproduction will be described.
The switches 27a, 27b, 27c, 27d are connected to the P side respectively, and PG
The switches 28a, 28 are formed by (a), (b), (c), and (d).
By controlling b, 28c, 28d, a reproduction signal can be obtained from each head Ha, Hb, Hc, Hd. The reproduction signals of these four systems are supplied to the reproduction digital signal processing circuit 29, where the original video signal is restored and output from the terminal 30 as a reproduction video signal.

On the other hand, the reproduced signals of the four systems are supplied to the BPFs 31a, 31b, 31c and 31d, respectively, and the pilot signal components are separated. Here, as is apparent from FIG. 1A, the pilot signal reproduced from the areas a1, a3, a5, and a7 is always p1. On the other hand, a multiplier
When the pulse signal (e) output from 26 is at high level, the heads Ha, Hb, Hc, Hd trace the areas a1, a3, a5, a7, so that the switches 32a, 32b, 32c, 32d are set to H level at this time. If connected to the side, the pilot signal input to the adder 33 will be p1. Therefore, the pilot signal output from the adder 33 is the average signal of p1 reproduced from the two heads tracing on the tape. For the phase difference due to head mounting error, add the output of this adder 33 to PC15, LPF
It is smoothed by supplying it to a PLL circuit composed of 17, VCO16. However, in the PC 15, only the error signal during the reproduction of the area where the pilot signal p1 is reproduced is effective, so that this is sample-held by the sample-hold circuit (S / H) 35. As a result, the reference signal of p1 from VCO16, in which the variations in the mounting positions of the four heads are smoothed,
From DL19, 20, and 21, reference signals of p2, p3, and p4 are obtained, respectively.

On the other hand, from the L side terminals of the switches 32a, 32b, 32c, 32d, the head H
A pilot signal is output in which a, Hb, Hc, and Hd are separated from the reproduced signal while tracing the regions a2, a4, a6, and a8. The phase of this pilot signal changes according to the track shift with respect to the control track. Now, if the phase of each pilot signal is in the relationship shown in FIG. 1 (B), when each head is shifted to the right side in FIG. 1 (A) with respect to the control target track, the phase of the reproduced pilot signal is clockwise. It rotates to the left, and when it shifts to the left, it rotates counterclockwise.

Therefore, in the PCs 34a, 34b, 34c, 34d, the reference signals p1, p2, p3, p4 having a phase corresponding to the phase of the pilot signal of the control target track of each head Ha, Hb, Hc, Hd and the reproduction pilot signal from each head A tracking error signal is obtained by comparing the phases of the signals. However, in this case, each head Ha, Hb, Hc, H
Only the error signals during the tracing of the areas d2, a4, a6, and a8 in d are valid, so signals indicating this timing are shown in FIGS. 4 (f), (g), (h), and (i). ) Inverter
35 and AND gates 36a, 36b, 36c and 36d are used to control the gates 37a, 37b, 37c and 37d. This adds 38
Is input to the capstan control circuit 40 via the LPF 39. 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 roller 42 in a method of compensating for the track deviation.

In the digital VTR of the above-described embodiment, tracking control can be performed only by superimposing a single-frequency pilot signal, so that a wide band of the digital video signal can be taken. Further, since the reference phase for forming this error signal is obtained based on the signals reproduced from various positions in the width direction of the tape, the influence on the tracking error signal by the jitter during reproduction by the rotary head is suppressed to a small level. be able to. Also, since the phase of the pilot signal recorded in the control target track of each head is always the same,
This makes it possible to simplify the configuration of the switching circuit system when configuring the circuit. Further, since the tracking error signal is formed by using the reproduction signals of all the heads, it is possible to deal with the variation in the mounting position of each head, and it is possible to obtain a very good tracking control signal.

The tracking control method of the present invention is not limited to the arrangement of the pilot signals in the above embodiment,
Other arrangements are possible.

FIGS. 6 to 8 show four video signals for one field, respectively.
It is a figure which shows the other example of arrangement | positioning of the pilot signal in the case of dividing and recording into four tracks as a system signal. The meanings of p1, p2, p3, and p4 in the figure are the same as those in FIG. 1 (A), and the shaded area indicates that the pilot signal is not recorded.

The recording pattern in Fig. 6 is always p1 at the bottom of each track.
, And p1, p for the other parts that occupy most of the track.
Record 2, p3, p4 cyclically for each track. Considering that tracking control is performed by the above recording pattern,
The p1 reproduced from the lower end of each track forms a reference alliance pilot signal, and tracking control is performed based on the phase difference between the pilot signal reproduced from the other part and this reference alliance pilot signal. In this case, as compared with the recording pattern shown in FIG. 1A, the reliability of the phase of the referral spirot signal at the upper end of the track is lowered, but the tracking control signal can be obtained from almost the entire area of the track. Since it is possible, it is suitable when performing tracking on a track whose linearity has deteriorated.

In the recording pattern of FIG. 7, there is one track for recording a pilot signal at the lower end of each track for every four tracks, and for the other parts, p1, p2, p3 and p4 are cyclical as in the case of FIG. To record. In this case, the tracking control is formed based on the phase difference between the pilot signal reproduced from the other part and the reference signal which is reproduced only from the lower end of the recorded track of p1. I do. In this pattern, the reliability of the phase of the reference signal is reduced in the track recorded with p4, but only one kind of pilot signal is recorded in each head. In comparison, the circuit configuration is greatly simplified.

In FIG. 8, the tracks that can be control targets are T ₁ , T ₂ ,
T ₃ , T ₄ , and T ₅ , which are present every two tracks as shown in the figure.
Only p1 is recorded in the control target track, and p2 and p4 are recorded in the areas a2, a4, a6 and a8 of both adjacent tracks. That is, the head control a1, a3, which should trace the control target track,
The reproduction pilot signal from a5, s7 forms a reference allot pilot signal, and the tracking control signal is obtained by the phase difference between this and the reproduction pilot signal from the regions a2, a4, a6, a8. However, in this case, since the direction of the tracking error signal is inverted for each control target track, the tracking error signal must be appropriately inverted by an inverting amplifier or the like.

In the above-described embodiments, all 1 field video signals are 4
Although the embodiment has been described in the case of dividing and recording into one track, the number of divided tracks, that is, the number of systems of the information signal can be set arbitrarily, and the following 6 systems of the information signal are cyclically. 9th recording pattern when recording on
This will be described with reference to FIGS. 10 and 10.

In FIG. 9, p1 ', p2', p3 ', p4', p5 'and p6' represent six pilot signals having a phase difference of 60 DEG on the recording medium. The recording pattern of FIG. 9 is such that the pilot signal of p1 'is recorded at the lower end of each track, and the reference signal is formed by using p1' reproduced from the lower end of the track where the pilot signal is recorded. The tracking control is performed in the same manner as in the case of FIG. Even if the phase difference of the pilot signals between adjacent tracks is 60 ° as in this example, the S / N ratio is better than that of 90 °.
However, the tracking control can be performed in the same manner, although it decreases.

Further, even when the information signals of 6 systems are cyclically recorded, the above-mentioned p1, p2, p3 and p4 can be used. 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 a10 in the width direction of the tape, and the control target track is T
As shown by a, Tb, Tc, every 3 tracks. In this pattern, the period of the recording pattern of the pilot signal is 6 track periods, which is suitable for recording a digital video signal with 6 heads.

〔The invention's effect〕

As explained above, according to the present invention, n track periods
When a recording medium on which information of a system (n ≧ 2) is recorded is reproduced by a plurality of heads, each head can trace an information signal of a desired system in a good tracking state, such as a switching circuit. The circuit configuration can be simplified.
Further, the recorded pilot signal only needs to have a single frequency, and does not limit the band of the recorded information signal. Further, since the phase difference of the pilot signal between adjacent tracks can be set arbitrarily, the pilot signal can be recorded at a desired track period (n × i), and the number of systems (n) of the information signal which is an integral fraction of this period is also arbitrary. Can be set to.

[Brief description of drawings]

1 (A) and 1 (B) are views showing recording patterns by a digital VTR as one embodiment of the tracking control method of the present invention, and FIGS. 2 (A) and 2 (B) are embodiments of the present invention. Fig. 3 for explaining the principle of tracking control
FIG. 4 is a diagram showing a schematic structure of a digital VTR as one embodiment of the present invention, FIG. 4 is a timing chart showing waveforms of respective portions in FIG. 3, and FIGS. 5 (A) and 5 (B) are one embodiment of the present invention. FIG. 6 is a diagram showing the head configuration of a digital VTR as an example, and FIGS. 6 to 10 are diagrams showing other examples of the phase arrangement of the pilot signals on the tape. In the figure, 2 is a magnetic tape as a recording medium, 11 is a recording digital signal processing circuit, 12a, 12b, 12c and 12d are adders, and 1 is an adder.
Reference numeral 3 is a reference oscillator, 16 is a voltage controlled oscillator, 19, 20 and 21 are delay circuits, 22, 23 and 24 are switches, 25 is a 4-phase PG generator, 26 is an 8-multiplier, and 29 is a reproduction digital signal processing. circuit,
34a, 34b, 34c, and 34d are phase comparators, 38 is an adder, 40 is a capstan control circuit, 41 is a capstan, a1 to a10 are track divided areas, and p1, p2, p3, and p4 are pilot signals, respectively. Is.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinsuke Yamashita 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Souichi Kashida 770 Shimonoge, Takatsu-ku, Kawasaki-shi, Kanagawa Prefecture Inside the Tamagawa Works of Canon Inc. (72) Inventor Mitsuhiro Otokawa 770 Shimonoge, Takatsu Ward, Kawasaki City, Kanagawa Inside the Tamagawa Works of Canon Inc. (56) Reference JP-A-58-41469 (JP, A) JP-A-63 -121165 (JP, A) JP-A-63-121163 (JP, A)

Claims (1)

[Claims] 1. A plurality of systems of information signals are recorded so that information systems of the same system are arranged for every n tracks (n is an integer of 2 or more) with respect to a large number of tracks arranged in parallel on a recording medium. In a system for reproducing the information signal from a recording medium, a pilot having a single frequency so that the phases of the control target tracks in the plurality of tracks are mutually shifted by the same amount in opposite directions. A signal is recorded together with an information signal at an n × i track period (i is an integer of 1 or more), and when reproducing the information signal, a reference signal indicating a phase of a pilot signal to be reproduced from the control target track is formed, A tracking error signal is formed based on the difference between the phase of the reference signal and the phase of the actually reproduced pilot signal, and tracking control is performed according to the tracking error signal. Tracking control method.