JPS5975450A - Tracking controlling system - Google Patents

Abstract

PURPOSE:To quickly shift a reproducing head to a normal track when the reproducing head largely gets out of the normal track, by obtaining an auxiliary tracking signal which performs control for putting the reproducing head onto the normal track. CONSTITUTION:After a pilot signal frequency component is extracted from a signal reproduced by a head 23 through a switch 22, regenerative amplifier 24, and LPF26, the signal is mixed with a four frequency reference signal 28 supplied from a control circuit 13 through a filter 17 at a mixer 27. An output signal containing the component of fH-4fH frequencies is inputted into level discriminating circuits 44-46 through BPFs41-43 having center frequencies fH, 2fH, and 4fH, respectively and, when the output signal exceeds a fixed threshold, a high-level signal is inputted into a condition detecting circuit 47. When it is discriminated that the reproducing head is not on a normal track, an auxiliary tracking control signal 48 is generated and a capstan motor is controlled by a capstan controlling circuit 37, and then, the head 23 is quickly shifted to the normal track.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Substances of the Invention] The present invention relates to a tracking control method for causing a head to follow a track during playback in a controlled playback device such as a Helicalus VTR.

[Technical background of the invention and its problems]

Helical scan V T )1. As one of the tracking control methods in JP-A-53-116120, a four-frequency tracking signal (pilot signal) is recorded, as described in Japanese Patent Application Laid-Open No. 53-116120, ``Method and Apparatus for Controlling the Position of a Wording or Reading Head.'' A method is known in which a pilot signal is sometimes recorded on each track together with an information signal, and the tracking control signal is obtained using this pilot signal during reproduction.

That is, l /, −/, I: I /l −/
, l:/, -/41=J:3:1 or 3:1:
4 types of frequencies that meet the conditions of 3/I ef2 rm+/
4 pilot signals are prepared, and these are sent to f, ~f, ~fs for each track on the recording medium as shown in Fig.
Recording is performed in a frequency permutation in a cyclic order of ~f, ~f1, . . . During reproduction, a reference signal having the same frequency sequence as the pilot signal is prepared, and two types of difference frequency signals between the pilot signal from a track adjacent to the reproduction track and this reference signal are detected.

For example, as shown in FIG. 1, when the head 2 is reproducing a track in which a pilot signal of frequency f is recorded, the pilot signal frequencies of the left adjacent track and the right adjacent track are respectively fl + 'S * reference signal Since the frequency is f, the frequencies of the above two types of difference frequency signals are l/1/ll and 1ft-muI. Similarly /s
, /l, /l When reproducing a track on which pilot signals have been completely recorded, l /, -/, respectively.
l and If5-f41゜l/1/ll and If, -/I
A difference frequency signal of I, l/4-/l and 1f, -/1 is obtained. l/, -/, 1= If, 7f, I
=M, If, -mul = I/4/l I
=3M, a difference frequency signal between the M and 3M frequency waves will be obtained whenever any track is reproduced. Therefore, the difference frequency signal between M and 3M is detected from the reproduced signal, and the level difference between both signals is further detected to obtain a tracking control signal.
If tracking control is performed so that this becomes zero, for example, the reproducing head can accurately follow the track.

However, although this method allows accurate tracking, it has the disadvantage that if the head deviates from the regular track for some reason during startup or playback, it takes time to place the head on the regular track. there were.

[Purpose of the invention]

An object of the present invention is to provide a tracking control method that allows the reproducing head to be placed on a regular track in a short time at the time of startup, etc.

[Summary of the invention]

In a tracking control method using a 4-frequency pilot signal, the present invention provides a tracking control method in which the reproducing head is positive, l:11. This system is designed to identify the state of deviation when the playback head has been off the track for a long time, and to obtain an auxiliary tracking control signal that controls the playback head to be placed on the correct track in the shortest possible time. .

That is, the present invention provides l/
,-v,+:+f,-v,l:l/! -f4 +'=
A: B: Four types of frequencies f1 that satisfy A +/,, /8
, f is recorded cyclically together with the information signal, and during playback, FI is obtained from the mixed output of the playback pilot signal and a reference signal whose frequency changes cyclically for each playback track.
, FA (FI < Fs), and further, 11. In this method, a tracking control signal is obtained by detecting the level difference between the difference frequency signals between the two, and this tracking control signal is used to cause the playback head to follow the track. .

Means for detecting the presence or absence of a difference frequency signal of a frequency F, F,<Ft<Fa, and a difference frequency signal of a frequency F, Fll<FA, and these frequencies FI.

The present invention is characterized by having means for obtaining an auxiliary tracking control signal based on the detection result of the presence or absence of the difference frequency signal of FI9F4.

〔Effect of the invention〕

According to the invention, the auxiliary tracking control signal can be used, for example, to increase or decrease the tape running speed or to change the phase of the frequency sequence of the reference signal when the playback head is far off the normal track. With this, it is possible to place the reproducing head on the regular track in a short time and quickly shift to the tracking control operation using the original tracking control signal.

[Embodiments of the invention]

1/+ 7tl: I/l 7sl: 1f8/
Taking the case of 41 = A: B: A Melil: 3:1 as an example, fI.

! , , /s, f, each pilot signal frequency is /,=
It is expressed as N/, = N+M/3=N+4M f<= N+3M. In the case of a VTR, for example, 6.
5 fH, fu in M (fH: horizontal synchronization frequency),
f, 6.5 fH in ft, 7.5 fH in ft, 1 in fs,
0.5 fH* Selected as f4 happiness 9.5/H.

Pilots of such frequencies /, f, /, , /, (signals are recorded on each track on the recording medium in the frequency order of f, ~f, ~f, ~f4~f, ...) In this case, during playback, for example, the frequency permutation /
, ~f4~f, ~f, ~f, ..., there are four types of combinations of both signals, as shown in the table below, depending on the positional relationship between the playback head and the track. .

In the case of VTTI, the pilot signal frequency is generally used in the lower band than the low frequency converter J-leave carrier, 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 87
N Played often. Therefore, for each combination shown in Table 1, looking at the generation state of the difference frequency signal between the reproduced pilot signal and the reference signal from the reproduced track and the adjacent track, we find that 1) the reference signal with respect to the reproduced pilot signal is In the case of (3fH, G, /Φ~(3f
H, 2fHz fH) ~ (3fH.

0, ZH) ~ (3/H, 2fH, fH) ~ (37H + O
, fH) is generated. Similarly below,
(2) In the case of reference signal M■, (2/
T(, ZH, O) ~ (Oe / p -4fH) ~ (2
fH.

/T? , O)-・(0,fT(,4/H)~(2f
A difference frequency signal is generated at (ZH, 4) for each track if the reference signal is (3)
/H, 3/H) ~ (ZH-0; 3 ZH) ~ (fH.

4fp, 3fH) ~ (fH, 0, 37H) ~ (#7, 4
fH.

3 ZH) −°゛ A difference frequency signal is generated as shown below.

(4) If the reference signal is 0, (0*3
ZH-2fH) ~ (4fH, 3/Hp O) ~ (0°3fH, 2fH) ~ (4/ue 3 /) T , 0)
A difference frequency signal is generated as follows: ~(0,3fH+2fH)...

Here, state (1) is when the playback head is on the old track, and tracking control is possible using the tracking control signal obtained by detecting the level difference between the two types of difference frequency signals fHt 3 fIN. becomes. On the other hand, in the cases tp= +21, +3+, and ta+, the playback head is off from the regular track.
These are 7H (or 3/I() # 2/H.

By examining the occurrence of 47H, it can be distinguished from state (1) and also from each other. Namely.

Paying attention to the ZH, 27H, 4/T (period) frequency components of the mixer output that mixes the reproduced pilot signal and reference signal, in state (1), (fH) ~ (2/H, ZH) ~ ( ZH)
~(2fH,,ZH)~(fT()...In state (2), (2ZH, fH)~(ZH, 47H)~(2/H.

ZH) ~ (/, , 4 fH) ~ (2fH, fH)・
...In state (3), (ZHe 4 ZH) ~ (fT()
~(ZH, 47Tl) ~(fT() ~(ZH, 4fH)
...In state (4), (2fH) ~ (4fH) ~ (2Z
H) to (4fH)(2/T()...) and can be distinguished from each other.

If state (1) is determined, normal tracking control using the tracking servo may be continued as is.

Then, in state (2), for example, the tape running speed may be slowed down, and in state (4), conversely, it may be made faster. Condition (3) The playback head is deviated from the normal track by two track pitches, and in such a case, for example, by changing the (5"l phase of the frequency permutation of the reference signal), the frequency permutation is changed according to Table 1 above. (j).

It is sufficient to shift to either state (■) or (2).

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

FIG. 2 shows a configuration example of a tracking control system used in a VTR or the like to which the present invention is applied. In the figure, the reference oscillator IIg formula each pilot signal frequency /'+ -
It oscillates at a frequency that is a common multiple of /l, /s, and /4, and its output is led to a preset table counter 12, and the frequency is divided to twice the pilot signal frequency under the control of a control circuit 13. Based on the track switching signal 14 and the recording/reproducing mode signal 15, the control circuit 13 calculates 2f1°2/1 from the counter 12 for each track during recording.
The counter 12 is preset and the frequency division ratio is controlled so as to obtain signals of frequencies 2/S, 2/4p 2fI+, . . . .

The output of the counter 12 is divided by a flip-flop 16 so that the frequency for each track is /I tf @ #
/s + /l + /+ e... After being made into a signal with a duty of 50%, the high frequency component is removed by a filter J7 to become a pilot signal 18, which is mixed into an information signal 20 such as a video signal by a mixer 19. The mixed signals are supplied to the head 23 via the recording amplifier 21 and the recording/reproduction switch 22. In this way, each track on a recording medium such as a videotape has f1~! , ~f, ~f4~! ,
, , , are recorded in a frequency permuted manner such that the pilot signals are superimposed on the information signal.

On the other hand, during playback, the head 23 plays back the switch 2.
A part of the regenerated signal 25 extracted through the regenerative amplifier 2 and the regenerative amplifier 248 is guided to the low-pass filter 26, and the pilot signal frequency component is extracted. At this time, the control circuit 13
In response to the recording/reproduction mode signal 15, the counter 12 is set to 2f, +2f2.2/1.2/, t2f,
? The output of the filter 17 is controlled by switching and outputting the signals of the frequencies of...
Signals with frequency permutations of ~/':, -f, ~f, ~/s~... are obtained. This signal is supplied to the mixer 27 as a reference signal 28 and mixed with the pilot signal component from the low-pass filter 26.

The output of this mixer 27 includes fHe 2fH, 3/H+
4/H frequency component is included. ing. This mixer 2
The output 29 of 7 is input to a tracking control signal generation circuit 30 on one side. In the tracking control signal generation circuit 30, the passband center frequency is F1 medium/H, F, medium 3.
After separating and extracting 7 segments corresponding to the right adjacent and left adjacent difference frequency signals when the head 23 is on a regular track using the band pass filters 31 and 32 of the detector circuit 33. By detecting the difference between the two through differential amplifier 35 through 34, a tracking control signal 36 having a polarity and level corresponding to the tracking deviation is generated.
generate. This control signal 36 is for example a capstan for a capstan motor 38 that drives the tape →)"
- is applied to the control circuit 37, thereby causing the head 23 to follow the track.

On the other hand, the output 29 of the mixer 27 is [-1 in f) [(or 3fH in F3), F, in 2/, , F, in 4/)T
A bandpass filter 41 having a passband center frequency of
．． 42.43 is also input. Note that the bandpass filter 41 may be used in common with the bandpass filter 3 or 32 in the tracking control signal generation circuit 30. The outputs of these bandpass filters 41, 42, and 43 are input to level determination circuits 44, 45, and 46, respectively.

The level determination circuits 44, 45, and 46 output %fH or 3fH when the respective input signal levels exceed a certain threshold.
If 2/H and 4fH components are present, a high level signal is output, and otherwise a low level signal is output. The binary signals thus obtained at the outputs of the level determination circuits 44, 45, and 46 are input to the state detection circuit 47, and the (
Identification and detection of states 1) to (4) is performed. Since the input of this state detection circuit 47 is a binary signal, it can be realized by a conventional logic circuit.

When the state detection circuit 47 detects state (1), it does not perform any control, and when it detects state (2) or (4), it controls the capstan servo circuit 37 with the first auxiliary tracking control signal 48 to control the capstan servo circuit 37. Stan motor 38
Decrease or increase the rotation speed of As a result, the running speed of the tape is slowed down or fastened, and the head 23 is quickly moved onto the regular track. When state (3) is detected, the control circuit 13 is controlled by the second auxiliary tracking control signal 49, and the phase of the frequency sequence of the reference signal 28 is changed. That is, the generation order of the reference signals in the above table is changed from the state (■) to the state (11!1) of (■, ■, ■).

In this way, under the control of the auxiliary tracking control signals 48 and 49 output from the state detection circuit 47,
The head 23 will be able to ride on a regular track in a short time. After this, the state becomes state (1), so accurate tracking is performed using the original tracking control signal 36.

Note that the state ejection circuit 47 has the state 9yA+21, (31
, +41, and control is also performed to prevent the reproduction signal from appearing when the signal is disturbed.

This invention can be implemented with various modifications as follows. That is, in the above embodiment, the frequency permutation of the reference signal is a permutation in which the vortex number of the 1111th frequency sequence of the pilot signal is swapped, but it may also be a permutation in which the odd number of the frequency permutation of the pilot signal is swapped. The present invention can also be applied to the same permutation as the signal. Even when the frequency permutations of the reference signal and pilot signal are the same, there are four types of combinations of the two as shown in the table below.

Here, the reference signal σ) 1 phase is (3/H, 0° fly) ~ (fH, 0, 3fu) ~ (3/l (, (1,
fH) ~ (fH.

0.3fH) ~ (3fH ~ 0.fn)..., if the reference signal is ■, (0, 3/H, 2fH) ~ (0, /■■,
4. /H)~(0°3fn+2fH)~(0,fn,4
fH) ~ (0, 3fH, 2/H)..., reference signal f)
(For ■, (n, fH, 2fH) ~ (0, 3fH, 4
fH) ~ (0, fH, 2/, () ~ ('L3fH, +4
, fH) ~ (o, fH, 2/H)..., when the reference signal is ■, (/Ht 3 fH, 4/"a) ~ (fH
+ 2/T (, 3fH) ~ (f pasted 3fH, 4/II) ~
(fH, 2/I(+3/+()~(fn3 fn +
Since a difference frequency signal is generated for each track like 4/[l)..., %fH (or 3ft4), 2/H
.

By paying attention to the 4fH component, four states can be distinguished at the same time as in the above-mentioned real 1-Q example.

Furthermore, when implementing the present invention, each state may be controlled in accordance with the state only when S is continuously output for a certain period of time in the output circuit.

Furthermore, instead of changing the phase of the frequency sequence of the reference signal, the nature of the tracking control signal may be reversed.

On the other hand, regarding tracking control, instead of increasing or decreasing the running speed of the tape, the playback head may be swung in the gap direction or track width direction using a piezoelectric element, etc. In this case, the control using the auxiliary tracking signal is in the state f2.
When detecting +, +41, move the playback head approximately 1 in the above direction.
Control may be performed to move it by the track pitch.

[Brief explanation of the drawing]

FIG. 1 is a 1"7I diagram for explaining the frequency arrangement of a tracking pilot signal on a videotape, and FIG. 2 is a block diagram of a tracking control system according to an embodiment of the present invention. 1...Track , 2...Head, 11...Reference oscillator, 12...Bresettable counter, 13...
Control circuit, 16...Flip-flop, 17...Filter, 18...Pilot signal, 19...Mixer, 22...Control/regeneration changeover switch, 23...Head. 26...Low pass filter, 27-1. mixer, 28
. . . Reference signal, 30 . . . Tracking control signal generation circuit, 31, 32.・Band pass filter, 33゜3
4...Detection circuit, 35...Differential amplifier, 36...
Tracking control signal, 37... Capsun servo circuit, 38... Capstan motor, 41-43...
・First to third band pass filters, 44 to 46...
- First to second level determination circuits, 47... State detection circuit, 48.49... Auxiliary tracking control No. 1, 50.
・・Mute signal % 51 ・・Neating circuit, 5
2... Playback output. Applicant's agent Patent attorney Takehiko Suzue 1st 1
'='1 21st, I 0 T 14

Claims (7)

[Claims] (1) Each track on the recording medium has l/1−/, I
:lf, -/31:I/, -f4+=A:B:Four types of frequencies f1. ．． A pilot signal of f*-fs-f4 is cyclically recorded together with an information signal, and during playback, F+-"s (Fr
<Fs), and further detects the level difference between the difference frequency signals of Kone 7 to obtain a tracking control signal, and uses this tracking control signal to cause the playback head to follow the track. a difference frequency signal of frequency F1 or F3 from the mixed output;
means for detecting the presence or absence of a difference frequency signal of frequency Ft, where Fl <Ff <Fs, and a difference frequency signal of frequency F4, where F<F'4;
A tracking control method comprising means for obtaining an auxiliary tracking control signal based on a detection result of the presence or absence of an F4 difference frequency signal. (2) Pilot signal frequency /+, /l −fs
, /4 is /, * 6.5 fH+ /, medium 7.5
/T(t /,,:10,5/T(,/, medium 9.5
/T((f■ (is the horizontal synchronization frequency), and each difference frequency signal frequency F1 tF2 +F3.F, is fH in F1
, 2 fl□ in Ft, 3fHt in Ft, 4fH in Ft. (3) means for detecting the presence or absence of a frequency F, or a difference frequency signal between J-1 and F, , F, from the mixed output;
l: or F, and Ff e Fl as the respective passband center frequencies. Second. A third band-pass filter and a first band-pass filter that determines the output signal levels of these band-pass filters to obtain a binary signal indicating the presence or absence of a difference frequency signal between F, or F, and F, . gi2. 2. The tracking control system according to claim 1, further comprising a third level determination circuit. (4) The tracking control method according to claim 3, wherein the first bandpass filter is also used as a bandpass filter for obtaining the tracking control signal. (5) The tracking control method according to claim 1, wherein the running speed of a tape as a recording medium in a helical scan VTR is controlled by an auxiliary tracking control signal. (6) The tracking control method according to claim 1, characterized in that the phase of the frequency permutation of the reference signal is changed by the auxiliary tracking control signal. (7) The auxiliary tracking control signal moves the playback head approximately 1 in the gap length direction or track width direction.
In particular, the tracking control method according to claim 1, characterized in that the displacement is performed by the track pitch.