JPS62189664A - Tracking controller - Google Patents

Abstract

PURPOSE:To attain a complete tracking control with a simple constitution by forming the tracking error signals at every frame to perform the tracking control after detecting only two types of frequencies at every other track out of the pilot signal of four types of frequencies to be reproduced. CONSTITUTION:A multiplier 3, a reference oscillator 4 and the 1st and 2nd band pass filters 5 and 6 are used to detect the difference frequencies DELTAfA and DELTAfB between two types of frequencies f1 and f3 of the reproduction pilot signal SPL which is reproduced at every other recording track and out of each recording track recorded on a magnetic tape and the frequency f2 of the reference pilot signal SREF. Then only two types of frequencies are detected at every other track out of the pilot signal of four types of frequencies to be reproduced. Then the tracking error signals are produced at every frame and the tracking control is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention provides four types of pilot signals whose frequencies change cyclically on recording trunks formed in sequence across the running direction on a recording medium. So-called 4-frequency A, which performs tracking control so that the playback head traces a predetermined track based on the frequency components of pilot signals that are sequentially recorded and played back from adjacent trunks during playback.
Regarding the TF type tracking control device, for example, the so-called 8
It is applied to 1m video playback devices, etc.

[Summary of the invention]

The present invention aims at simplifying tracking processing in a so-called 4-frequency ATF type trunking control device by detecting only two frequencies of every other track and forming a tracking error signal for each frame.
This makes it possible to perform quick and stable tracking control.

[Conventional technology]

Conventionally, as a tracking control method for video tape recorders, a plurality of pilot signals whose frequency changes cyclically are sequentially recorded on recording tracks formed in sequence across the running direction on a recording medium, and when played back, The so-called ATF performs trunking control so that the reproduction head traces a predetermined track based on the frequency components of pilot signals reproduced from mutually adjacent tracks.
For example, in a so-called 8-layer video tape recorder, four types of frequencies (,, rt, f2+ fa (rt = 10
2KHz, fz =116KHz, fs =160KH
A four-frequency ATF system is adopted in which a pilot signal of z, fa = 146 kHz) is sequentially assigned to each track on the magnetic tape and recorded. In the reproduction system of the 8 Dragon video tape recorder, four types of frequencies f, which are the same as the frequency of the pilot signal, are used.
A tracking error signal is obtained by multiplying the reproduced pilot signal by reference pyroft No. 43 of +, fz, fz, fa, and separating and detecting both side track outputs using the difference frequency component. The above four types of frequencies 9r+, fz, f3. fn (7) The reference high loft signal is the master clock (e.g. 3718#5.9
4MHz).

[Problem that the invention seeks to solve]

As mentioned above, in the playback system of the 8-Yu video tape recorder that adopts the 4-frequency ATF system, by dividing the master clock, the standards of the four frequencies ft, rg, rs, and ra, which are the same as the frequency of the pilot signal in the recording system, are created. Since a pyro-node signal was formed, there was a problem in that the circuit configuration became complicated. In particular, in machines dedicated to playing 8 Dragon video tapes, there are four types of frequencies f,...
f! There is a demand for simplification of the tracking process which requires a reference pilot signal of + [3, r4.

SUMMARY OF THE INVENTION In view of the conventional problems as described above, the present invention aims to simplify the tracking processing of a 4-frequency ATF type tracking control device in a so-called 8III VTR, etc., and to perform quick and stable tracking control. In this way, the present invention provides an ATF type tracking control device with a novel configuration that is suitable for application to playback-only machines and the like.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention has been developed to operate a reproducing head based on the frequency components of the pilot signals reproduced from each recording track in which four types of pilot signals whose frequencies change cyclically are sequentially recorded. A tracking control device that performs tracking control by forming a tracking error signal includes a circuit that extracts two types of frequency components from a pilot signal reproduced every l recording track and subtracts each signal level, and the subtraction. The present invention is characterized in that a circuit for forming a knocking error signal is provided, and tracking control is performed using a tracking error signal obtained every frame.

[Effect]

In the tracking control device according to the present invention, the reproduced 4
every other track in the pilot signal of different frequencies
Tracking control is performed by detecting only the frequency and forming a tracking error signal every frame.

An embodiment of the device will be described in detail with reference to the drawings.

The embodiment shown in the block diagram of FIG.
This is commonly used in the reproduction system of F-type 8-fin VTRs, and in this embodiment, part of the reproduced RF signal reproduced from a magnetic tape by a rotating video head (not shown) is input to the signal input terminal 1 as an input signal S1□ A reproduced pilot signal S□ extracted from the human input signal SIN by a low-pass filter (LPF) 2 is supplied to a multiplier 3.

Here, on the magnetic tape TP, as shown in FIG.
Four different frequencies r+, fz, fy
, ra (e.g., fl =102KHz, f, = 1
16KHz, Ex = 160KHz.

4 tracks T+, Tt, Tx on which the pilot signal of fa (146 KHz) was recorded together with the video signal.
, Ta are formed diagonally and closely together so as to repeat in a cyclical manner. Note that A in Figure 2 indicates normal recording (S
P) mode track pattern, B is the above SP
This figure shows a track pattern in a long recording (LP) mode in which recording is performed at a tape running speed of mode 172.

The multiplier 3 receives 41! of the pilot signal! A reference pilot signal S I of one type of frequency (for example, It = 116 KHz>) among frequencies f, , f, , r, , f of class i
IEF is supplied from the reference oscillator 4, and multiplies the reproduced pilot signal SPL by the reference pilot signal S***. The multiplication output signal of the multiplier 3 is supplied to the first DC converting circuit 7 via the first band pass filter (ΔfABPF) 5, and is also supplied via the second band pass filter (Δrs BPF) 6. It is supplied to the second DC conversion circuit 8.

The first bandpass filter 5 filters Δf A −1r + f * l = l f in the multiplication output signal.
The first DC conversion circuit 7 extracts the difference frequency component Δf of *-f s l:l+14KHz, converts the signal level of the difference frequency component ΔrA extracted by the first bandpass filter 5 into a DC current, and converts the signal level of the difference frequency component ΔrA extracted by the first bandpass filter 5 into The output S1 is supplied to a signal subtractor 9. Further, the second bandpass filter 6 filters Δfs =l rx −fs l−1r in the multiplication output signal.
A difference frequency component Δf of 44kHz is extracted. The second DC converting circuit 8 converts the signal level of the difference frequency component Δf1 extracted by the second band pass filter 9 into a DC signal, and supplies the output S to the signal subtracter 9. There is.

Then, the signal subtracter 9 subtracts each output signal of the first and second DC converting circuits 7.8, and sends the subtracted output signal directly and via the inverter IO to the switch circuit 1.
1. This switch circuit 11 is configured to select each reproduction RF signal by a reproduction video head (not shown).
The frequency-divided output of the l/2 frequency divider 14 using a D-type flip-flop to which the F switching pulse RFsw is supplied as a clock pulse from the control input terminal 12 via the inverter 13 is the switching control signal S11. The subtracted output signal directly supplied from the signal subtracter 9 and the subtracted output signal whose polarity has been inverted via the inverter 10 are alternately selected for each frame to obtain the first sample. It is supplied to a hold (S/l(+)) circuit 15 and a second sample and hold (S/Hz) circuit 18.

The first sample and hold circuit 15 receives an RF switching pulse RFs supplied to the control input terminal 12.
The tracking error signal S is obtained by sampling and holding the subtracted output signal once every l frame, with w as a sample-and-hold pulse P and a1. It is supplied as LIT+ from a signal output terminal 17 via an output amplifier 16 to a tracking servo system (not shown). .

Further, the second sample-and-hold circuit 18 uses the RF switching pulse RF□ supplied from the control input terminal 12 via the inverter 13 as a sample-and-hold pulse P 111, and the first sample-and-hold circuit 15 Sample and hold pulse P 181 and π
The level comparator 19 samples and holds the subtracted output signal at a predetermined timing with a phase difference of /2.
supply to. The level comparator 19 binarizes the signal level of the sample-and-hold output from the second sample-and-hold circuit 18 using the reference (Level V REF as a threshold) and outputs the binarized signal level from the second signal output terminal 20.

In the embodiment with the above-described configuration, the 4 RF signal contained in the reproduced RF signal is reproduced by sequentially tracing each track on the magnetic tape with a rotating video head (not shown).
Frequencies of types r,,f,.

By multiplying the reproduced pilot signal SPL of f:l, f by the reference pilot signal SIIEF of r2 in the multiplier 3, the frequency of the reference pilot signal SIIEF is determined as shown in the timing chart of FIG. f2
A period T during which the video head is tracing a recording track in which a pilot signal with a frequency f, which is shifted by a frequency of ΔfA, is recorded. The difference frequency ΔfA component between the reproduced pilot signal SPL and the reference pilot signal S□ is extracted as a tracking error component by the first band-pass filter 5, converted to DC by the first DC conversion circuit 7, and stopped. 7D traces the recorded trunk T, where the pilot signal of the above-mentioned convex pilot signal S□, whose frequency is shifted by the frequency Δf, from the frequency f2 of the convex pilot signal S□, to the playback video. The reproduced pilot signal SPL and the reference pilot signal S□ due to crosstalk from adjacent trunks during periods other than period Tc.

The difference frequency Δf, the component is the second band pass filter 6
is extracted as a tracking error component by
It is converted into DC by the DC converting circuit 8.

Then, a signal obtained by subtracting the outputs SA, S of each of the DC converting circuits 7 and 8 by a signal subtracter 9 and the signal are sent to an inverter 1
The first sample-and-hold circuit 15, to which the switch circuit 11 alternately selects and supplies the signal whose polarity is inverted by 0, is supplied by the switch circuit 11 with the signal whose polarity is inverted by the sample-and-hold pulse P, □. Period T...
A tracking error signal is formed by sampling during a period T, , T, other than Tc and holding during the period T, , Tc. Further, the second sample/hold circuit 18, which is alternately supplied with the subtracted output signal and a signal obtained by inverting the polarity of the subtracted output signal via the switch circuit 11, is operated by the sample/hold pulse P□8. The sample of the first sample and hold circuit 15
By sampling the subtracted output signal during the periods T, , Tc at a predetermined timing with a phase difference of π/2 from the hold pulse and holding it during the periods Tb, Ta, a playback mode different from the recording mode is achieved. Detection signal S that indicates the oscillation point of the tracking loop when a playback operation is performed or when the tracking loop does not lock properly. Form 1°.

Note that in the first embodiment described above, the multiplier 3, the reference oscillator 4, and the first and second bandpass filters 5.6,
A reproduction pilot signal SPL that is reproduced every other recording trunk from each recording trunk recorded on the magnetic tape.
24ffi [frequency f.

1. The difference frequency ΔrA, Δf between the frequency ft of the reference pilot signal S□, and the frequency ft of the reference pilot signal S□, is detected, but as in the second embodiment shown in FIG. The signal SPL is supplied via the Hasophia amplifier 31 to a first bandpass filter 35 that passes the IF'1 wave number component f, and a first bandpass filter 36 that passes the frequency component r3, and is then transferred onto the magnetic tape. The signal subtractor 9 directly detects two types of frequency components f, , f, of the reproduction pyro signal SPL that is reproduced every other recording track from each recording track recorded in the y) signal SPL.
The tracking error signal S is obtained by subtracting each signal level at , and inverting the polarity of the fIi calculation output signal every frame. It is also possible to form a U□.

〔Effect of the invention〕

As is clear from the description of the embodiments described above, the tracking control device according to the present invention detects only two frequencies at every other track among the pilot signals of four different frequencies to be reproduced, and generates a tracking error signal every l frame. Since tracking control is performed by forming a 4-frequency ATF system, tracking control can be performed reliably with a simple configuration, making it ideal for use in playback-only machines such as so-called 9 am VTRs that employ a 4-frequency ATF system. becomes.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a first embodiment in which the present invention is applied to a reproduction system of a 4-frequency ATF type 31V TR, and FIG. 2 is a block diagram showing the SP mode and LP mode of the magnetic tape in the above embodiment. FIG. 3 is a schematic diagram showing a recording pattern;
The figure is a timing chart for explaining the operation of the above embodiment. FIG. 4 is a block diagram showing a second embodiment of the tracking control device according to the present invention. 1.31... Signal input terminal 2... Low pass filter 3... Multiplier 4...
Reference oscillator 5.6.35.36... Bandpass filter 7.8.
...DC conversion circuit 9...Subtractor 10...Inverter 11...Switch circuit 14...1/2 frequency divider 15...Sample/hold circuit Magnetic chip 7. Figure 2

Claims (1)

[Claims] Tracking control is performed by forming a tracking error signal for a reproducing head based on the frequency component of the pilot signal reproduced from each recording track in which four types of pilot signals whose frequencies change cyclically are sequentially recorded. In a tracking control device designed to perform What is claimed is: 1. A tracking control device, comprising: a circuit for generating a tracking error signal by adjusting the tracking error signal, and performing tracking control using the tracking error signal obtained for each frame.