JPS6010441A - Tracking control system - Google Patents

Abstract

PURPOSE:To put a reproducing head onto a regular track in a short time at a start time or the like by providing an analog operating circuit which multiplies reproduced pilot signals themselves or multiplies said pilot signal with a signal obtained by shifting the phase of the reproduced pilot signal at 90 deg. and detecting two kinds of differential frequency signal from the output of this operating circuit and detecting the level difference between them to obtain a tracking control signal. CONSTITUTION:In case of reproducing, 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 to extract pilot signal frequency components. The output of the low-pass filter 25 is inputted to an analog operating circuit 26. The analog operating circuit 26 is what is called a squaring circuit where the signal inputted to an input terminal 41 is branched into two and branched signals are led to two inputs of a multiplier 42 and the output signal of the multiplier 42 is taken out from an output terminal 43, and differential frequency signal components required for generation of the tracking control signal are obtained only from the reproduced pilot signal.

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 a tracking control method using a four-frequency pilot signal. Regarding.

[Technical background of the invention and its problems]

As one of the tracking control methods for helical scan VTRs, etc., Japanese Patent Application Laid-Open No. 116120/1982 "Writing or reading head position control method and device" is disclosed.
A four-frequency dragging signal (-
A method is known in which a pilot signal (4' pilot signal) is recorded on each track along with an information signal during recording, and the tracking control signal is obtained using this pilot signal during playback.

That is, lfx fx l' Ifz-fs l'
Four frequency classes ft, fz, fs, fa that satisfy the condition of Ifs-fa 1 = 1:3:1 or 3:1:3
Prepare pilot signals of f! and send them to each track 1 on the recording medium as shown in FIG. ~f2~f3~f
4~f! ......, and when playing back, the playback number is played from at least one track adjacent to the track to be played back in 2 and 2, and this is the same as when recording. In order, a 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 case of a VTR, generally the lower band of the low frequency conversion color subcarrier is used for the signal frequency, so at the same time as the pilot signal from the playback track, the pilot signal from the adjacent tracks on the right and left is also used. is often played.

For example, as shown in FIG. 1, when a track in which a pilot signal of frequency ft is recorded is played back by head 2,
It is considered that at least pilot signals fl, fz, and fs are reproduced.

At this time, the difference frequency difference signal is Ift-fxl-1fs
- There are two types of fsl. In this case, as the head 2 shifts to the track side of the arrow signal f1 or the track side of fs, 1ft-fz1 or tj:
The level of the difference frequency signal of fsl changes, and the degree of deviation to each track changes.

Ru. Similarly, is head 2 fs, fa, ft? When moving to the track where the pilot signal is recorded, l fz-fs I and l fs-f4I -1fs- respectively.
f41 and D4f11-1j"4f11 and l fl-fa
A difference frequency signal of 1 is obtained. 1f1fx l = I
fs-fa I=M, Dg fs 1=Ifi-f
Assuming that a l = 3M, it depends on the width of track 1 and the width of head 20, but when the head 2 is near the center of track 1 in a so-called tracking state, the difference frequency signal between M and 3M will determine which track. You can also get it when playing. 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; There was a drawback that if the head came off the regular track for some reason, it took a strange amount of time to place the head on the regular track. For example, VT of inclined azimuth recording method
In the case of R, if the phases of the frequency permutations of the reproduction signal and the reference signal are exactly two track pitches apart, then the azimuth of the head corresponds to the four turns of recording on the track, and tracking is correct. Even though this is done, tracking control for two track pitches is performed, and tracking takes time.

On the other hand, one of the functions required for a VTR is
There is so-called continuous shooting, in which a new recording is made following the previous recording. In this case, if there is a disturbance in the regularity of the frequency permutation of the pilot signal before and after continuous shooting, tracking will also be disturbed. For example, if the pilot signal is fl-
Assuming that it is recorded at frequencies fa~f3~f4~f1..., and if the no'4 pilot signal frequency on the last recorded track is fs, then the pilot signal will start recording from 14 at the next recording. There must be.

A similar problem is thought 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. That is, the pilot signal on the PCM audio track is the same as the pilot signal on the video track.
It has a frequency permutation of 2~f3~f4~fx...,
The frequency of the pilot signal recorded on the video track on the same helical track and a predetermined combination, for example f
l and fz, ft and fs, fs and f4, f< and fl
This combination is selected.

Therefore, this regularity must be maintained even during dubbing.

[Purpose of the invention]

The object of this invention is to control tracking that allows the playback head to be placed on the correct track in a short time at startup, etc., and that also maintains the regularity of the frequency order of the 1,000-lot signal during continuous shooting and dubbing. The goal is to provide a method.

[Summary of the invention]

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

That is, the present invention provides 1f on each track on the recording medium.
t-fa I: Ifg-fs l: Ds-f4
4 types of frequencies ftaf*mfs that satisfy 1=A:B:A
, a pilot signal of f< is cyclically recorded together with an information signal, and upon playback, a tracking control signal having a polarity and level corresponding to the dragging shift is generated based on the playback pilot signal, and this tracking control signal is used for playback. In the method of making the signal follow the track, an analog arithmetic circuit is provided that multiplies and matches the reproduced pilot signal itself, or multiplies and matches the reproduced pilot signal and a signal obtained by shifting the phase of this by 90 degrees, and this arithmetic circuit The basic feature is that two types of difference frequency signals are detected from the outputs of the two types, and the level difference is further detected to obtain a tracking control signal.

In addition, this invention can be used to convert ft, fz
, fs, and fa, and after detecting its level, extract a frequency component of 1/4 of the switching frequency ft of the reproduced pilot signal from this level detection output, and By detecting the peak value of the frequency component, the track in which the pilot signal of frequency ft is recorded is determined, and the signal generation state of the pilot signal generating means is corrected based on the detection timing of this peak value. This is how it was done.

〔Effect of the invention〕

According to this invention, since the tracking control signal is obtained only from the regenerated pilot signal, there is no need to match the phase of the frequency permutation of the regenerated tracking signal and the reference signal, unlike in systems that use reference signals, and during normal regeneration, the regenerated The head can be placed on a regular track in a short time. Particularly in the case of a VTR, as long as the azimuth of the head corresponds to the recording pattern on the tape, it is possible to quickly shift to the correct dragging state.

In addition, even when dubbing is performed during splicing, the frequency sequence of the pilot signal changes from f1 to f2 to f3 to f4 to ft for each track, or the combination of pilot signal frequencies between the video track and the PCM audio track. Since this regularity is maintained, even if playback is performed from a recording medium after continuous shooting or post-recording, good playback without any dragging errors is possible.

[Embodiments of the invention]

1ft-ftl: D-fsl' Ds (41
=A: Taking the case where BAA is 1:3:1 as an example, fl
.

Each pilot signal frequency of fx, fs, f4 is f
It is expressed as follows: J=N f2'=N0M fs=N+4M f<=N+3M. In the case of a VTR, for example, N*
6. s fH-Mkifu (fH: horizontal synchronization frequency), 6.5 fa a fa ”47.5 f in fl
E a fs middle 10.5fm, fa middle 9.5f11
selected.

When such pilot signals of frequencies f*, fa, fs, f4 are recorded on each track on a recording medium in the frequency sequence fl~f2~f3~f4~f1...
The following table shows the frequency relationship of various signals in each track during playback.

However, fpo a /PRe fpL represent the reproduction pilot signal frequencies from the reproduction track and the tracks that are momentarily in contact with the right and left of the cornering track, respectively.

In the above example, A:B:A is 1:3:1, and this ratio ζ is arbitrary and can be changed in various ways, such as 3:1:3, 1:5:1, etc. In particular, when l:fi:l or n:l:n, it is most preferable that n is kikyo.

Figure 2 shows a tiger used in a VTR to which this invention is applied.
An example of the configuration of a king control system is shown.

In the figure, a reference oscillator 1 oscillates at a frequency that is a common multiple of each pilot signal frequency fx, fa, fs, fa. The frequency is divided up to twice the signal cylinder wave number. Based on the track switching signal 14, the control circuit 13 controls the counter 12 every time during recording.
4 #2f! , . . . The counter 12 is reset and the frequency division ratio is switched so that signals with frequencies of , . . . are obtained.

The output of the force 177 and 12 is input to I by the free lag flop 15.
The frequency is divided by A, and the frequency is fl, fa # for each track.
y changes as fs s f4 a fs a...
After the signal is converted into a signal with a density of 50%, high frequency components are removed by a filter J6 to form a pilot signal, which is mixed with an information signal 18 such as a video signal or a PCM audio signal by a mixer 17, and then sent to a recording amplifier No. 9 and a recording signal. /The signal is supplied to the head 2, for example, a rotating magnetic head, via the playback switch 20. In this way, fl-f*~f3~f4~f1...
The pilot signals of the frequency permutations are recorded superimposed on the information signal 18.

On the other hand, during playback, head 2 is played back and switch 2
0 and the reproduced signal 2 extracted via the regenerative amplifier 22
3 is input to the low/(') filter tacho 5 via the AGC circuit 24, and the pilot signal frequency component is extracted. The output of the Ronos filter 25 is input to an analog arithmetic circuit 26.

-r Narok'(s'I n circuit 26 is an example t if f
fi 31 PI (a) As shown in K, the signal input to input terminal 4 is split into two and introduced into two inputs of multiplier 42, and the output signal of multiplier 42 is taken out from output terminal 43. It is a so-called squaring circuit, and its output signal is as follows, assuming that the input signals from the playback track and the signals from the adjacent tracks on the left and right are ω11, Slnωpt, and girlω3t. It is expressed as

(sinω11-1-sir+ω, t+sinω3t
)2=sin2ω, t+5in2ω, t−+−8
m2ω3 t −1-25ina+1 t X Sin
011 t +28in (dl t xsf+ ω3
t +27n (6, i X5in (d 3 tay
s2ωst)+((2)(ω!+ωg)t−■(ω1−
ω2) t) ten ((2) (ω!+ω3) l −ays
(ω1-ω5)t)+(■(ω2+ω5)t-■(ω2
-ω3)t) 100 t-1-cos'(ωl+ω,)t-1-co
o(ω1+ωs)t (■(ω1-ωx)t+咋(ωl
-ωs)t+possible(ω8-ω3)t)・・・・・・・・・
・・・・・・・・・(1) Here Q) 8 ((d r
(d R) t, Q16 (ω1-ωs) t is the difference frequency signal component between the pilot signal from the reproduction track and the pilot signals from the adjacent tracks on the left and right, and according to the above equation, M, 3M. It is an ingredient. That is, the difference frequency signal component necessary to generate the dragging control signal can be obtained from only the reproduced pilot signal without using a reference signal as in the conventional method.

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/IP 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.

Output detection circuits 3o and s of these filters 28 and 29
The signal is applied to both input terminals of the differential amplifier 320 through the respective input terminals i, and the level difference between the two is detected.

Then, the level difference detection signal which is the output of the differential amplifier 32 is input to the polarity switching circuit 33, and the polarity is inverted for each FJ raw track by the track switching signal -@14' in this circuit 33. A tracking control signal 34 is generated having a polarity depending on the direction of the tracking deviation and a level depending on the magnitude of the tracking deviation. In the case of a VTR, this control signal 34 is used to control a capstan motor that drives the tape or to move the 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.
It is also possible to use a multiplier 42 which multiplies the signal inputted to 1 and a signal obtained by shifting the phase of this signal by +90° or 190° by a 90° phase shifter 44. The output signal L of such an analog arithmetic circuit is expressed as a linear equation.

(ainω11+iinω, 1-)-sinω3 t
) x (cosω, j-1-cosω, 1+■ω5
t) = sin ω lt
g t +sir+ (11, t Xcnsa+, t
-4-sinω3txcr+sω, t-)-sinω
1t x CQ! IQ13 t +: inω1 t −4
"yy+ω31-)-sin ω3 tX(2)ω3t-nO) 11IIn(ω to 1G'3)t+s"(ωg+ωs)L
(”(ω1-6)2 ) t+・an (rdl (
d3) tsin(61g -6-・H) t) -
・(2) In this way, when the analog arithmetic circuit shown in FIG. 3(b) is used, as in the case of the square circuit shown in FIG. The difference frequency A6 component necessary to generate the tracking control signal such as ω3) can be obtained, and the output does not include the DC component that existed in equation (1).
There is an advantage that the dynamic range of the arithmetic circuit 26 itself and the circuits at the succeeding stage can be effectively utilized.

On the other hand, the output (reproduction) of the low-pass filter 25 and the pilot signal) are also supplied to the H band-pass filter 35.

This band pass filter 35 has four types of frequencies 11tfl
, fa , fa , f4 reproduction/4' pilot signals of arbitrary one type of frequency/1 (i=one of 1.2, 3.4). The output of the band filter 35 is detected by a detection circuit 36, and its level is detected.The output of the detection circuit 36 also includes the influence of noise components at frequencies near fi. Therefore, the output of the detection circuit 36 is guided to a filter 37 consisting of a bandpass or low-pass filter, and the switching frequency of the regenerated pilot signal (this is equal to the field frequency in the case of a VTR, for example, 60 Hz for NTSC and 50 Hz for PAL). 1/4 of the frequency component is extracted.As a result, the filter 37 outputs a sinusoidal signal representing a level change of the 1,000-lot signal with the frequency fl.

Next, the output of the filter 37 is led to a peak detection circuit 38, and a peak value detection signal 39 is obtained which indicates the timing at which the head 21 traces the track in which the pilot signal with the peak frequency ft is recorded. . This peak value detection signal 39 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 39 immediately before starting the continuous shooting mode or the post-recording mode, and corrects the generation timing (phase of frequency permutation) of the newly recorded No. 9 pilot signal. .

That is, if the unrecorded pilot signal frequency fl is fl in the final recorded track during continuous shooting, the pilot signal of frequency f2 is recorded in the next track. As mentioned above, this is a specific 1f+7! of the regenerated pilot signals. frequency f,
Since we know the track where the pilot signal is recorded, we can check the pilot of this fi (the h's again on the 4th track counting from here, counting from the latest track where U is recorded) P. The counter 12 may be controlled so that the Ilot Buddhist name is recorded. More specifically, fi2fx is assumed, and if the counter 12 is reset and the fx no/lot signal is generated, then when the peak value detection signal 39 is obtained, that is, f
When the regenerated pilot signal 1 is detected, the counter 12 may be reset by taking into account the delay time of the system.

In other words, even when dubbing is performed on a PCM audio track, the signal should be recorded on the PCM audio track using the peak value detection signal 39 that indicates the timing at which the reproduction pilot signal of fl is obtained from the already recorded video track. 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 permutation of pilot signals before and after continuous shooting, and the regularity of the combination of pilot signal frequencies between the video track and the PCM l-rack during post-recording. .

Note that it is preferable to correct the generation timing of the pilot signal 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 with various modifications.For example, in addition to the analog calculation circuit 26 shown in FIGS. It is also possible to use a square law detection circuit.

Further, in the embodiment, the polarity switching circuit 33 is used as a differential amplifier if
3 Placed after z, band pass filters 28, 29
It may be inserted after 0 or after the detection circuits 30 and 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.
) (b) is a diagram showing an example of the configuration of an analog arithmetic circuit according to the present invention. DESCRIPTION OF SYMBOLS 1... Track, 2... Head, 11... Reference oscillator, 12... Presettable counter, 13... Control circuit, 15... Flip-flop, 16... Filter, 17... Pexa, 20...Record/playback switching switch, 21...Head, 25...Low nose filter, 26...Analog calculation circuit, 27...Dividing circuit, 28.29...Pantono and filter I', 30.3
1... Detection circuit, 32... Differential amplifier, 33...
Polarity switching circuit, 34...ζ racking system a1 signal, 3
5...Band pass filter, 36...Detection circuit, 3
7... Filter, 38... Peak detection circuit.

Claims (2)

[Claims] (1) Ifl-fz I : If-f31'
Ifs-f4I = 4A:B:4 frequencies f1 z f 1 e f 3a Ifs-f4I = 4A:B:F4 has a pilot signal generation means that selectively generates pilot signals of f1, and these pilot signals are f1~f2~f3
The cycles of ~f4~f1... are recorded cyclically in wave number order on each track on the recording medium, and during playback, the polarity and repeat ( In a tracking control method in which a tracking control signal having a signal is generated to make the playback head follow the first track, the playback pilot signal itself is multiplied, or the playback pilot signal is multiplied by 90 degrees with the playback) 3. Detects two types of difference frequency signals from the output of the subtractor circuit, and detects the level difference between these two types of difference frequency signals. means for generating the tracking control signal; and means for generating the tracking control signal from the endogenous pilot signal.
means for extracting a pilot signal of any one frequency among lef2hfs and fa; four stages for detecting the level of the pilot signal outputted by this means; and a level detection output obtained by this means. means for extracting a frequency component of 1/4 of the switching frequency of the regenerated pilot signal from the regenerated pilot signal, means for detecting a peak value of the frequency component extracted by this means, and a timing at which the peak value is detected by this means. A dragging control method characterized in that the pilot signal generating means 7) means for correcting the t9 pilot signal generation state. (2) Pilot signal frequency fs a fx z f
saf4 is 6.5f summer l in ft, 7-5f ha in f
10.5 fi in fa. The tracking control method according to claim 1, wherein f<*9.5 fn (fH is the horizontal synchronization frequency).