JPS6010443A - Tracking control system - Google Patents

Abstract

PURPOSE:To put a reproducing head onto a regular track in a short time by squaring a carrier having an optional frequency out of reproduced pilot signals f1-f4 to extract one kind of differential frequency signal and detecting its level and extracting 1/4 frequency components of the switching frequency of reproduced pilot signals thereafter to correct the pilot signal generation state. CONSTITUTION:A part of a reproduced signal 23 which is reproduced by a head 21 and is taken out through a switch 20 and a regenerative amplifier 22 is inputted to a low-pass filter 25 through an AGC circuit 24 in case of reproducing to extract frequency components of the pilot signal. The output of an analog operating circuit 26 is divided into two in a proper amplitude ratio by a dividing circuit 27, and these divided outputs are fed to both input terminals of a differential amplifier 32 through detecting circuits 30 and 31, and the level difference between them is detected and is inputted to a polarity switching circuit 33, and the polarity is inverted for every reproduced track by a track switching signal 14 to generate a tracking control signal 34 which has a polarity corresponding to the direction of tracking deviation and a level corresponding to the magnitude of tracking deviation.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a method for causing a head to follow a track during reproduction in a helical scan VTR or other recording/reproducing apparatus, and in particular, tracking control using a four-frequency pilot signal signal. Regarding the method.

[Technical background of the invention and its problems]

As one of the tracking control methods for helical scan VTRs, etc., Japanese Patent Laid-Open No. 53-116120 "1
A four-frequency tracking signal (
A method is known in which a pilot signal is recorded on each track along with an information signal during recording, and the pilot signal is used during playback to obtain a tracking control signal.

That is, l fa −fz to l/a−fsl : lf
Prepare pilot signals of four types of frequencies ft, fx, fs, /4 that satisfy the issue of s fa l = 1:3:1 or 3:1:3, and divide these as shown in Figure 1. f1~f2~f3~f4~f for each track 1 on the recording medium
＋・・・・・・Records in a circular order, and when playing back,
At least one track adjacent to the track to be played by head 2
The reproduced pilot signal is reproduced from one track, and the difference frequency signal between the reproduced pilot signal and the reference signal is detected as a reference signal having the same frequency as the reproduced pilot signal in the same order as when it was recorded.

In the case of a VTR, the pilot signal frequency is generally used in the lower band than the low frequency conversion color subcarrier.
At the same time as the pilot signal from the reproduced track, pilot signals from the adjacent tracks on the right and left are often reproduced.

For example, as shown in FIG. 1, when the head 2 reproduces a track in which a pilot signal of frequency f2 is recorded, it is considered that at least the pilot signals /l, /2, and fs are reproduced.

At this time, the difference frequency difference signal is 1.7+-fzl.

Two types of 1ft-fsl are available. In this case, the head 2 is on the track side of the mother pilot signal f1 or fa.
The level of the difference frequency signal If+ 721 or Ifz/ml changes as the signal shifts toward the track side, and the degree of shift toward each track can be seen. Similarly, head 2 is f
a, f4, fl pilot) (When moving to the track where No. H is recorded, l/2, J”31 respectively
and lfs /4LIfs −/41 and If4 h I
, 1f4-fs I and Dt-/zlO difference frequency signals are obtained. lfs, 7'zl=Ifs/41=M
, l ft fs and If< , f+l=3M,
Although it varies depending on the width of track 1 and the width of head 2, when the head 2 is near the center of track 1 in a so-called tracking state, a difference frequency signal between M and 3M can be obtained no matter which track is reproduced. . Therefore, tracking can be performed by detecting the difference frequency signals of these M and 3M and controlling the level difference between the signals with respect to a target value as a control amount for tracking.

However, this method uses a reference signal with the same frequency permutation as the regenerated pilot signal to obtain the tracking control signal from the regenerated pilot signal, so accurate tracking is possible, but If the head comes off the regular track for some reason, it takes time to place the head on the regular track. For example, in the case of a VTR with a tilted azimuth recording method, if the phases of the frequency permutations of the reproduction/arm plot signal and the reference signal are shifted by exactly two track pitches, there will be no correspondence between the azimuth of the head and the recording pattern on the track. Even though the tracking is being performed correctly, the tracking control for two track pitches is performed, which results in longer tracking time.

On the other hand, one of the functions required for a VTR is
There is a so-called continuous shooting mode in which a new recording is made following the previous recording. In this case, if the regularity of the frequency permutation of the pilot signal is disturbed before and after continuous shooting, tracking will also be disturbed. For example, the pilot signal is
Assuming that it is recorded at the frequencies of ~fx~f4~f1..., then the frequency of the #9 pilot signal at the last recorded track is fs, then the next recording will be recorded from the #9 pilot signal k/4. I have to start doing it.

A similar problem is likely to occur when post-recording is performed on a PCM audio track assigned to a part of a helical track when the audio track is converted to PCM, which is planned to be adopted in a small-sized VTR. In other words, the pilot signal on the PCM audio track is the same as the one on the video track.
It has a frequency permutation of f1~f1~f4~f1..., but it has a predetermined combination with the frequency of the nof pilot signal recorded on two video discs on the same helical track, for example, f, fl-fl, and fslfs. and f4, f4 and f
The combination l is selected. Therefore, this regularity must be maintained even during dubbing.

[Purpose of the invention]

An object of the present invention is to provide a tracking control method that can place the playback head 0 on the regular track in a short time at startup, etc., and that can maintain the regularity of the frequency order of the pilot signal during splicing and dubbing. It is about providing.

[Summary of the invention]

The present invention is a tracking control method using a four-frequency signal, in which a tracking control signal is obtained only from a reproduced pilot signal without using a reference signal during reproduction.

That is, the present invention provides Dt for each track on the recording medium.
-hl:I/z /sl:1fs-fil=A:B:A
Pilot signals of four frequencies satisfying /1+f*+f3 and fa are cyclically recorded together with information signals, and upon playback, a tracking control signal having a polarity and level corresponding to the tracking deviation is generated based on the reproduced pilot signal. In the method of making the playback head follow the track using this tracking control signal, an analog calculation circuit that multiplies and matches the playback pilot signal itself, or multiplies and matches the playback pilot signal and a signal obtained by shifting its phase by 906. is provided, two types of difference frequency signals are detected from the output of this arithmetic circuit, and the level difference is further detected to generate a tracking control signal? The basic feature is that it is designed to be obtained.

Further, the present invention provides a regenerated pilot signal with I' 1rf
s1. A multiplier is provided that multiplies the carrier signals of any one frequency among /3 and f4, and after extracting any one difference frequency signal from the output of this multiplier and detecting its level, From this level detection output, a frequency component of 1/4 of the switching frequency of the reproduction/2-lot signal is extracted, and by detecting the peak value of this frequency component, the frequency t
The track on which the UFT nof pilot signal is recorded is determined, and the pilot signal generation state of the pilot signal generation means is corrected based on the detection timing of this peak value.

〔Effect of the invention〕

According to this invention, since the tracking control signal is obtained only from the reproduced pilot signal, there is no need to match the phase of the frequency permutation of the reproduced tracking signal and the reference signal as in the method using the reference signal, and the reproducing head is moved to the regular track. It can be put on top in a short time. Particularly in the case of a VTR, as long as the azimuth of the head corresponds to the recording nozzle turn on the tape, it is possible to quickly shift to the correct tracking state.

In addition, even when dubbing is performed during continuous shooting, the frequency permutation of the pilot signal is changed to fl=fx~f3~j4~f1... for each track, or between the video track and the PCM audio track. Since the regularity of the combination of the signal frequency and the pilot signal frequency is maintained, good playback without tracking traces is possible even if playback is performed from a recording medium after post-recording in the case of splicing.

[Embodiments of the invention]

1, I'+, hl:lfn /sl:lfs 7i1
For example, if =A:B:A is 1:3:1, fsp
Each pilot signal frequency of fxzfs=f4 is f1=N/2=N+M fs=N+4M! It is expressed as <=N+3M. In the case of a VTR, for example, 6 out of N,
5/n, Mki fncfH: horizontal synchronization frequency), 6.5 fur in fl, 7.5 fn in fz + 1 in f3
0.57Hr Selected as 9.5In out of 74.

These pilot signals of frequencies f1, f2, fs, and f4 are converted into fl-fz~f3~f4~f! When recording on each track on a recording medium in the frequency permutation of...
The following table shows the frequency relationship of various signals in each track during playback.

However, fPo'/FRlfPL represents the frequency of the reproduction/common lot signal from the off-center reproduction track and the tracks adjacent to the right and left of the reproduction track.

In the above example, A:B:A was set to 1:3:1, but this ratio is arbitrary and can be changed in various ways, such as 3:1:3, 1:5:1, etc. In particular, when it is 1:n:l or n:l:1, it is most preferable that n is an odd number.

FIG. 2 shows an example of the configuration of a tracking control system used in a VTR to which the present invention is applied.

In the figure, the reference oscillator II oscillates at a frequency that is a common multiple of each pilot signal frequency fx, fs, fs, f4, and its output is guided to the Zoresettable counter 12, and the pilot signal is generated according to the control signal from the control circuit 13. The frequency is divided up to twice the frequency. Based on the track switching signal 14, the control circuit 13 controls the counter 12 for each track during recording.
The counter 12 is preset and control is performed to switch the division ratio so that a signal with a frequency of /4 + 2ft l... is obtained.

The output of the counter 12 is sent to the flip-flop 15! 0
The frequency is divided by 1/2, and the frequency for each track is ft rfz
After it is converted into a signal with a duty of 50% that changes as +fs rf4 +ft r..., the filter 16 removes the υ high frequency component and becomes a pilot signal, and the mixer 17 converts it into an information signal such as a video signal or PCM audio signal. 18 and is supplied to a head 21, for example, a rotating magnetic bed, via a recording amplifier 19 and a recording/reproduction switch 20. In this way, the zoirot signals in the frequency sequence fl-f2 to f3 to f4 to f1, .

On the other hand, during playback, the head 21 plays back the switch 2.
0 and the reproduced signal 2 extracted via the regenerative amplifier 22
3 is connected to the low-pass filter 2 via the AGC circuit 24.
5, and the frequency components of the signal are extracted. The output of the low-pass filter 25 is the analog calculation circuit 2
6 is input.

For example, as shown in FIG. 3(, ), the analog arithmetic circuit 26 branches the signal f input into an input terminal 41 into two and introduces it into two inputs of a multiplier 42, and outputs the output signal of the multiplier 42. This is a so-called squaring circuit whose output signal is taken out from the output terminal 43, and its output signal is sinω1t+sinω1t+sl by inputting the mother pilot signal from the playback track and the pilot signals from the adjacent tracks on the left and right.
When nω3t, it is expressed as follows.

(sinω1 t 0slnω2t+sA+ω3t)=
s stone ωxt +sln OJI t ten sin 2ωs
t+2slnω1tXsinωz t+2sln6
J1 t X5lnωst+2fr+ω1tXs stone ω3
t cos2 or@t ) +(ccs (ω1 +01
1) t−(Xl!+(ωH(+32) j )+(fish(ωl+ω3)t−cQg(ω1−ωs) t )+(
cos(ω2+ωs) -4(ω2-ω3)t) 1 =-1-<2ωxt +cog26Jzt+迩2ωa
t) Jutei ((t) 1+2 ω2 ) t + cos (ωl 10 ωB ) t + a
s (ω2 + ω3) - (tuft (ωl - ωg) 1 + fish (ω
1 01g) to 10nobu ((132(123)t)...
...... (1) Here, residence (cho-ω2) t and fusa (ωl-ωs) t are the difference frequency signals between the pyro, g signal from the playback track and the pilot signals from the adjacent tracks on the left and right. According to the table above, it is a component of M and 3M. That is, the difference frequency signal component necessary to generate the tracking control signal can be obtained from only the reproduced/mother pilot signal without using a reference signal as in the conventional case.

The output of the analog arithmetic circuit 26 is divided into two by a dividing circuit 27 at an appropriate amplitude ratio, and then input to band pass filters 28 and 29 to remove unnecessary components. The bandpass filters 28 and 29 are tuned to frequencies M and 3M, respectively, and the above-mentioned two types of difference frequency signals are separated and extracted by these filters 28 and 29.

The outputs of these filters 28.29 are sent to the detection circuit 30.3.
1 to both input terminals of the differential amplifier 320, and the level difference between the two is detected.

The level difference detection signal, which is the output of the differential amplifier 32, is input to the polarity switching circuit 33, where the polarity is inverted for each reproduced track by the track switching signal 14'. A tracking control signal 34 is generated having a polarity depending on the direction and a level depending on the magnitude of tracking deviation. In the case of a VTR, this control signal 34 is used to control a cab stan motor that drives a chive or to move a rotary head in the track width direction or azimuth direction, thereby causing the head to follow the track.

Note that the analog calculation circuit 26 in FIG.
In place of the square circuit, an input terminal 4 as shown in Fig. 3(b) is used.
1 and this signal f: 90' phase shift 8S44
It is also possible to use a multiplier 42 that multiplies the signals phase-shifted by υ+90° or -90°. The output signal of such an analog arithmetic circuit is expressed by the following equation.

(thωlt +sliω1t+sinω1t)X(c
asω1t+ccsω2t+tuftω5t) =sluωttXaiω1t+slnω2txcmω1
t+s stone ω3tXcosω11+sin sushi tXcosω
z t 10slnω2t Xcasω2 to 10slnωs
t
l-ω1 ) t 10sIn (ω1-ω5)t-1(
n(ω@-+773) t) Song-(2) Using the analog arithmetic circuit shown in FIG. 3(b) in this way, the third
As in the case of the square circuit shown in figure (a), uIn (ω
l-ω2) tr 5in((IJI (/13)
The difference frequency signal component necessary to generate the tracking control signal, such as
This has the advantage that the dynamic range of the circuit 6 itself and the subsequent circuit can be effectively utilized.

On the other hand, the output (regenerated A pilot signal) of the pre-Me low/thousand filter 25 is also supplied to the multiplier 35, where it is multiplied by the carrier signal output from the carrier signal generation circuit 36. The gear signal generating circuit 36 generates a signal having an arbitrary frequency of one of four types of pilot signal frequencies fl, f + /s * 74 as a carrier signal. At the output of the multiplier 35, signals of the sum and difference frequencies of the carrier signal and the reproduced/4' pilot signal are obtained, and the generation state of the difference frequency signal is shown in Table 2 below in correspondence with Table 1 above. become that way.

That is, the difference frequency signals are O, M, and 3M.

4M frequency components are obtained. The output of this multiplier 35 is guided to a gundo pass filter 37, which selects any one type (0,
A difference frequency signal of one of M, 3M, and 4M components is extracted. The output of the pantone filter 37 is detected by a detection circuit 38, thereby detecting its level.

The output of the detection circuit 38 also includes the influence of noise components of frequencies near the difference frequency signal to which the pantone filter 37 is tuned. Therefore, the output of the detection circuit 38 is filtered by a filter 39 consisting of a band pass or low pass filter.
is guided by the switching frequency of the regenerated pilot signal (this is V
For TR, equal to the field frequency, e.g. NTS
60Hz for C and 50Hz for PAL)
74 frequency components are extracted. This filter 3
9, a sinusoidal signal representing a level change of the difference frequency signal extracted by the pantonograph 9 filter 37 is obtained.

Next, the output of the filter 39 is led to a peak detection circuit 40, and its peak value is detected. Figure 4 shows the detection circuit 38
shows the change in output level over time. In the figure, P is a peak value, and the timing at which this peak value P is obtained is when the playback head traces a specific track. For example, the frequency N of the carrier signal generated by the carrier signal generation circuit 36 is f+ (6.5fn), and the frequency of the difference frequency signal extracted by the bandpass filter 37 is 4M (
4fu), when the playback head traces the track (track number 3.7...) in which the pilot signal of N+4M=fs (key 10.5/H) is recorded, the output of the detection circuit 38 The level is maximum, then to the left,
When tracing the right tracks (track numbers 2, 4, 6.8, etc.), the output level of the detection circuit 38 decreases because the N+4M=/s reproduced pilot signal becomes a crosstalk component, and furthermore, the output level of the detection circuit 38 decreases. When tracing tracks (track numbers 1, 5, etc.), the detection circuit 38
The output level of will be zero.

Therefore, the output of the detection circuit 38 is transferred to the filter 3 as described above.
9 to the peak detection circuit 40 to detect the peak value P shown in FIG.
A peak value detection signal 40' indicating the timing when tracing the track in which the no4lot signal 'i (I is one of 1, 2, 3°4, in the above example, 1=3) is recorded. is obtained. This peak value detection signal 40' is supplied to the control circuit 13. The control circuit 13 controls the counter 12 according to the timing of the peak value detection signal 40' immediately before the continuous shooting mode or the post-recording mode, and corrects the generation timing (phase of frequency sequence) of the newly recorded pilot signal.

That is, if the pilot signal frequency recorded on the last recorded track is shifted from fl during splicing, a pilot signal with a frequency of 12 is recorded on the next track. This is played as described above!
Among the pilot signals, you can find the track in which the pilot signal of a specific frequency fl is recorded, so count from here based on the latest track among the tracks in which the pilot signal of this fl is recorded. The counter 12 may be controlled so that the fl pilot signal is recorded again on the fourth track. More specifically, f l
= f r and a pilot signal of fl is generated when the counter 12 is reset.
When the peak value detection signal 40' is obtained, that is, ft
When the reproduction or pilot signal is detected, the counter 12 may be reset taking into account the delay time of the system.

Also, when dubbing on a PCM audio track, recording should be made on the PCM audio track using a peak value detection signal that indicates the timing at which a /1 playback signal is obtained from a video track that has already been recorded. What is necessary is to control the generation timing of the pilot signal.

In this way, it is possible to maintain the regularity of the frequency order of pilot signals before and after continuous shooting, as well as the regularity of the combination of Guyot's frequencies between video tracks and PCM racks during post-recording. .

Preferably, the timing of generating the pilot signal is corrected when the running speed of the recording medium reaches a specified speed, or after a certain period of time after the recording medium starts to be driven.

The present invention is not limited to the embodiments described above, and can be implemented in various modifications.For example, in addition to the analog calculation circuit 26 shown in FIGS. 3(a) and 3(b), for example, a diode A square law detection circuit using nonlinear characteristics can also be used.

Further, in the above embodiment, the polarity switching circuit 33 is connected to the differential amplifier 32.
Although it is placed after the band filter 28, 29 or the detection circuit 30, 31, it may also be inserted after the band filter 28, 29 or the detection circuit 30, 31.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the frequency arrangement of tracking pilot signals on a videotape, FIG. 2 is a configuration diagram of a tracking control system according to an embodiment of the present invention, and FIG.
) and (b) are diagrams showing an example of the analog arithmetic circuit according to the present invention, and FIG. 4 is a waveform diagram for explaining the operation of the same embodiment. 1...Track, 2...Head, 1...Reference oscillator, 12...Presetter counter, 13...
Control circuit, 15...Flip-flop, 16...Filter, 17...Mixer, 20...Record/playback switch, 21...Head, 25...Low pass filter, 26...Analog calculation Circuit, 27...Divided circuit, 28, . 29...Band pass filter, 3θ, 3
1... Detection circuit, 32... Differential amplifier, 33...
Polarity switching circuit, 34...Tracking control signal, 35
... Multiplier, 36 ... Carrier signal generation circuit, 37
... Pantone 4 filter, 38... Detection circuit, 3
9... Filter, 40... Peak detection circuit, 42.
... Multiplier, 44...90° phase shifter. Applicant's agent Patent attorney Takehiko Suzue Figure 1 (b)

Claims (2)

[Claims] (1) Ij'l/21: Ifz, ffal:
1f3f< 4 types of frequencies f that satisfy I=A:B:A
+ rfz rfs rf4 pilot signal generation means for selectively generating pilot signals;
and the pilot signal f1~f2~f3~f4~f1...
A tracking control signal having a polarity and a level corresponding to the tracking deviation is generated based on the playback signal during playback, and the playback head is applied to the track. In the tracking control method for tracking, an analog calculation circuit that multiplies and matches the reproduction/arm rotation signal itself or multiplies and matches the reproduction/arm rotation signal and a signal obtained by shifting the phase of this by 90 degrees; means for detecting two types of difference frequency signals from the output of the circuit and further detecting a level difference between these two types of difference frequency signals to generate the tracking control signal; a multiplier for multiplying carrier signals of any one frequency among fs and f4; and means for extracting any one type of difference frequency signal from the output of the multiplier;
means for detecting the level of the difference frequency signal extracted by this means; means for extracting a frequency component of 1/4 of the switching frequency of the reproduction/zoot signal from the level detection output obtained by this means; Tracking control characterized by comprising means for detecting a peak value of a frequency component obtained by this means, and means for modifying the generation state of the pilot signal generating means according to the detection timing of the peak value by this means. method. (2) Pilot signal frequency f1 rfz rfsr
f4 is f+ 6.5fH+ f@ki 7.5fu+fski 10.5fH. The tracking control method according to claim 1, wherein f4 is 9.5 fH (fH is a horizontal synchronization frequency).