JPS59117877A - Tracking control system of magnetic picture recording and reproducing device - Google Patents

Abstract

PURPOSE:To make noise on a screen standstill at all times by using a signal sampling and holding as a phase error signal in a VTR of a tracking system using a pilot signal. CONSTITUTION:A head switching signal A is inputted from a terminal 31 at forward and reverse quick traversing reproduction, and a signal C synchronized with the rise or fall of a signal B frequency-divided by 1/2 is obtained, the signal is inputted to a monostable multivibrator 34 and a pulse output signal D of a short time interval is obtained. On the other hand, a tracking error signal E inputted from a terminal 11 is smoothed and inputted to a sample holding circuit 36 as a sampled signal source. The pulse output signal D is inputted to the sample holding circuit 36 as a sample pulse and a signal G sampled and held is outputted. This output signal G has less level fluctuation and this signal is used as a phase error signal of the capstan phase system to apply the circuit phase control of a motor, then the noise on the screen is made standstill at all times.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a tracking control method for a helical scan type magnetic recording/reproducing device (hereinafter simply referred to as a VTR), and particularly relates to a tracking control method for a helical scan type magnetic recording/reproducing device (hereinafter simply referred to as a VTR). VT to perform tracking '#JU Misaki using pilot signal
The present invention relates to a tracking control method during fast-forward playback in forward and reverse directions in R.

Conventional structure and its problems Traditionally, in a two-head helical scan type VTR, fast-forward playback in the forward and reverse directions is currently not possible.
This is used in H3 type VTRs and the like, and uses a method to always keep the noise on the screen still.

The method for realizing the above is to divide the 30H7 control torque recorded on the control track formed in the longitudinal direction of the magnetic tape by n according to the speed ratio of the fast forward, so that the frequency is always 30 Hz. 7, the rotational phase 10I of the motor was controlled as a reference signal for obtaining the phase error signal of the capstan phase determination system. However, in a new format VTR system in which the video head that records and plays the video signal regenerates the pilot signal and performs tracking, there is no control track in the longitudinal direction of the magnetic tape, so the control signal is frequency-divided as described above. I am no longer able to use any means to do so.

Purpose of the Invention The purpose of the present invention is to provide a method that can always keep the noise on the screen still when performing fast-forward playback in the forward and reverse directions, even in the tracking method using the pilot signal described above, similar to conventional VTRs. This is what we propose.

Structure of the Invention The present invention records a pilot signal for tracking control together with a video signal on a magnetic tape as a group of inclined discontinuous recording tracks, and processes the reproduced pilot signal to obtain a tracking error signal. This is a tracking method that controls the relative position between the recording trunk and the reproduction scanning locus of the reproduction magnetic head, and during fast-forward reproduction in the forward and reverse directions, the tracking error signal is divided by a percentage of the head switching signal. A tracking control system for magnetic recording and reproducing devices that controls the rotational phase of the motor by sampling and holding a pulse signal synchronized with the rising or falling edge and using the sample-and-hold output signal as a phase error signal for the Cagstano phase control system. .

DESCRIPTION OF EMBODIMENTS Before describing the present invention in detail, a method for creating a trunking error signal using a pilot signal will be described.

How to Create a Tracking Error Signal Using Pilot Signals 1) Various methods have been proposed, ranging from one to four types of signals. Here, a four-frequency pilot signal method using four types of pilot signals will be explained as an example.

FIG. 1 is a schematic diagram of a recorded magnetization trajectory on a tape by the four-frequency pilot signal method, and FIG. 2 is a block diagram of a reproducing circuit for obtaining a tracking error signal.

In FIG. 1, A1. B1. A2-... is each recording track of one field recorded on the magnetic tape by the A head and the B head. Arrow 1 indicates the scanning direction of the rotation throat. Each recording track contains 11
Valley and peak signals of frequencies indicated by f4 are sequentially recorded for each field. The recording order of the pilot signals is as shown in Figure 1, and the frequencies of the pilot signals are shown in Table 1. is set to the value shown.

Table 1 In Table 1, fH indicates the frequency of the horizontal synchronization signal, and 6.5fH is the frequency e that is 6.5 times the frequency of the horizontal synchronization signal.
d.

The frequency difference of the pilot signals between the valley recording tracks is the first
As shown in the figure, the frequency is fH or 3fH.

And the head is Ai (1-1, 2゜3, -...)
When scanning the trunk, the frequency difference between the pilot signal of the scanning track and the pyro and throat signals recorded in the adjacent track on the right on the paper is always fH, and that on the left is always 3fH. The head is B□ (i=1.
2.3. - - When scanning the track, the relationship is opposite to that described above, and the frequency difference between the pilot signals between the scanning track and the adjacent track on the right is always 3fH, and that on the left is always fH.

Since the pilot signal is a relatively low frequency signal around 100 KHz, the pilot signal recorded on the adjacent track can be reproduced as a crosstalk signal without the head scanning the adjacent track. For example, the pilot signal obtained when the head on-tracks the A2 trunk and performs playback scanning is f4. f2. f3
．． It is a composite signal of f4, and its level is highest at f4.
Next f2. f3 is played back at the same level. When the head slightly deviates from track A2 toward track B2 and performs reproduction scanning, the level of the reproduction pilot signal obtained is f.
lJ\ decreases in the order of 4 r 12 + j' 3. Therefore, the difference signal fH between the pilot signal on the main scanning track and each number 7412113 recorded on both adjacent tracks
and 3fH, respectively, and compare the reproduction levels of both signals, it is possible to know the amount and direction of deviation of the head from the main scanning track.

FIG. 2 is a block diagram of a reproducing circuit for obtaining a tracking error signal. In FIG. 2, a reproduced RF signal in which a video signal and a pilot signal are combined is input from a terminal 2. Circuit 3 is a low pass filter, regeneration R
Separate and extract only the pilot signal from the F signal. The pilot signal obtained in this poem is a composite signal of the main scanning track and the pilot signals recorded on both adjacent tracks.

Circuit 4 is a balanced modulation circuit, and the above-mentioned composite signal and terminal 5
Multiply by the reference signal supplied from Supply from terminal 5,
The supplied reference signal is a pilot signal having the same frequency as the pilot signal recorded on the main scanning track. For example, when the head reproduces and scans the track A2 in FIG. 1, the input signal of the balanced modulation circuit 4-\ is f.
2*f 4 , f 3 , and the reference signal supplied from terminal 5 is f 4 .

Therefore, the output signal of the balanced modulation circuit 4 is f 2 T f4
The sum and difference signals of each signal of r f 3 and the signal of f 4 are output. Circuit 6 is a tuned amplifier circuit tuned to an fH signal, and circuit 7 is a 3fH tuned amplifier circuit. Circuits 8 and 9 are detection rectifier circuits, and circuit 1° is a level comparison circuit. Therefore, each pilot signal taken out as a crosstalk signal from both adjacent tracks is separated and taken out as a difference signal from the pilot signal recorded on the main track, and then sent to the level comparison circuit 10. A signal corresponding to the level difference is output to the terminal 11. As for the signal obtained at the terminal 11, when the reproduction level of fH is higher than the reproduction level of 3fH, a potential of 10 is taken out according to the level difference, and in the opposite case, a potential of - is taken out. The signal output to the terminal 11 includes information on the amount and direction of track deviation of the head, and therefore can be used as a tracking error signal. However, a tracking error signal that is actually suitable for practical use requires further processing. This is because, as is clear from Fig. 1, the direction of head deviation and the beat signal (fH or 3fH
) are opposite to each other. In FIG. 2, circuit 12 is an analog inversion circuit, and circuit 1
Reference numeral 3 denotes a serial switch which is switched according to the level of the head switching signal supplied from the terminal 14. Therefore, for example, when the head scans the A track, the signal obtained at the terminal 11 is output as is to the terminal 15, and when the head scans the B track for reproduction, the signal obtained at the terminal 11 is inverted in analog form and output. . Therefore, regardless of the A or B track, the signal obtained at the terminal 16 always outputs a potential of 10 when the head deviates to the right from the track to be scanned, and always a potential of - when the head deviates to the left. Therefore, if the tracking error signal obtained at the terminal 15 is sent to the capstan motor as a phase error signal and the tape feed rate is controlled, the head will always scan on-track on the main scanning track. Become.

The above is an overview of the method for obtaining a tracking error signal using four types of pilot signals.

The present invention processes the signal obtained at the terminal 11 or terminal 15 in FIG. 2 by the method described later, and always makes the noise on the screen still when performing fast-forward playback in the forward-A direction and in the reverse direction. This paper proposes a method that can do this. The present invention will be explained in detail below.

In the tracking method described above, the reference pilot signal f1. input from the terminal 5 to the balanced modulation circuit 4 in FIG. f2+f3. When f4 is fixed to a single value, the output signal of the comparator circuit 1o changes as shown in FIG. 3, assuming that the zero reference is when the levels of the crosstalk signals fH and 3fH match. Here, a case will be described in which, for example, 6x speed fast-forward playback is performed. First, FIG. 4 shows the locus of the rotary head when a recorded pattern recorded at normal speed is reproduced in the forward direction at five times the normal speed. 21, 22° and 23 are the scanning trajectories of the head during 5x speed reproduction.

fl, which is input to the terminal 5 in FIG. 2 during fast-forward playback.

If one of the reference signals having different frequencies of f2, f3, and f4 can be extracted in succession, for example, if the reference signal of fl is selected, the fourth The output of the comparator circuit 1o of FIG. 2 when scanning as shown in the figure is performed is shown in FIG. 5 when expressed in correspondence with the head switching signal.

Next, fast forward playback in the reverse direction will be explained.

FIG. 6 shows the locus of the rotary head when a recording pattern recorded at normal speed is reproduced in the opposite direction at five times the normal speed.

24, 25, 26, and 2 are the scanning trajectories of the head. In this case, as in the forward direction, if the reference pilot signal f1 is taken out continuously, the output of the comparator circuit 1o in Fig. 2 when scanning is performed as shown in Fig. 6 corresponds to the head switching signal. When expressed in this way, it becomes as shown in FIG.

In the present invention, the output of the comparator circuit 1o in FIG.
The signal smoothed by @ is sampled and held using a pulse signal synchronized with the rising edge or falling edge of the signal obtained by dividing the head switching signal, and the sample-and-hold output signal is used as the phase error signal of the capstan phase control system to control the motor. This is to perform rotational phase control.

In addition, the head switching signal is used as a sample pulse.
The reason for using the frequency-divided signal is that, as shown in Figures 6 and 7, the signal obtained by smoothing the tracking error signal during fast-forward playback becomes a signal of 6 cycles in the 2-cycle period of the henodic switching signal. This is because if the sample is synchronized with a pulse signal every time the signal rises or falls, the polarity of the tracking error signal will be reversed every time the signal is sampled and held, making stable rotational phase control impossible.

Next, the configuration of an embodiment of the present invention is shown in FIG. 8 and will be explained using the operational waveform diagram in FIG. 9.

A head switching signal A is inputted from a terminal 31, and this head switching signal is inputted to a monostable multivibrator 33 which is triggered by the rising edge 9 or falling edge of a signal port whose frequency is divided by % by a % frequency dividing circuit 32. Then, the output of the monostable multivibrator 33 is obtained by dividing the frequency of the head switching signal to obtain a pulse output signal having an appropriate time width synchronized with the signal port. The pulse output signal 11 of the monostable multivibrator is input to the monostable multivibrator 34 which is triggered by this falling or rising edge, and a pulse output signal 2 having a relatively shorter time width than its output is obtained. - The tracking error signal E of the terminal 11 with the same number shown in FIG. 2 described above is input to the blade terminal 11. This embodiment shows the case of fast-forward playback at five times the speed in the forward direction.

This tracking error signal E is smoothed by a smoothing circuit 35, and the output signal of the smoothing circuit 35 is inputted to a sample hold circuit 36 as a sampled signal source. Incidentally, since the signal E is smoothed, the phase of the signal is delayed by T in time. Further, by inputting the pulse output signal 2 of the monostable multivibrator 34 mentioned above to the sample hold circuit 36 as a sample pulse, a part of the level of the varying tracking error signal is sampled,
The held output signal T is obtained as the output of the sample and hold circuit 36 described above.

The output signal G of the second sample and hold circuit 36 has almost no level fluctuation, and can be used as a phase error signal for the capstan phase control system to control the rotational phase of the motor. It should be noted that the same thing as above occurs when the droplet feed is played back in the reverse direction, so the explanation will be omitted.

Effects of the Invention According to the configuration of the present invention, in a VTft having a tracking method using a pilot signal, by using the sampled and held signal described above as the phase error signal of the capstan phase control system, a stable rotational phase of the capstan motor can be achieved. In other words, stable tape feeding control is performed, and the noise on the screen can always be kept still as in the case of using conventional control signals.

Furthermore, in the embodiment of the present invention, by changing the delay amount of the monostable multi-vib break 33 shown in FIG. 8, the scanning locus of the head can be softened and the position of noise on the screen can be freely changed.

[Brief explanation of drawings]

Fig. 1 is a diagram schematically showing the recorded magnetization locus on the tape by the four-frequency pilot signal method, Fig. 2 is a circuit block diagram for obtaining a tracking error signal, and Fig. 3 is a diagram showing the recording pattern in the configuration of Fig. 2. On the other hand, Figure 4 shows the output waveform of the comparator circuit when the reproduction reference pilot signal is set to a single frequency.
Figure 5 is a diagram showing the trajectory of the rotary head when fast-forwarding playback at double speed; Figure 5 is a diagram showing the relationship between the navel inoting signal and the output of the comparison circuit when playing fast-forwarding at five times the speed in the positive direction; Fig. 7 is a diagram showing the trajectory of the rotary head when fast forward playback is performed at 5x speed in the reverse direction. Fig. 7 is a diagram showing the relationship between the head switching signal and the output of the comparison circuit when fast forward playback is performed in the reverse direction at 5x speed. The figure is a block diagram of one embodiment of the tracking control method of the present invention, and FIG. 9 is an operational waveform diagram in the configuration of FIG. 8. 2...l'tF signal input terminal, 3...-Low pass filter, 4-...Balanced modulation circuit, 5...Reference pilot signal input terminal, 6...Tuned amplifier circuit ,
7--tuned amplifier circuit, 8, 9...-detection rectifier circuit, 10--level comparison circuit, 11--tracking error output terminal, 12--analog inversion circuit, 13 --Electronic switch, 14--Head switching signal terminal, 15-Phase error output terminal, 21,2
2゜23- Head trajectory during forward fast forward playback, 24゜25.26.27 - Head trajectory during reverse fast forward playback, 31- Head switching signal input terminal, 32-
% frequency divider circuit, 33--monostable multi-pipe rake, 34--semi-stable multivibrator, 35--
Smoothing circuit, 36-...- Sample Holt circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3 Figure 4 Figure 8 Figure 9

Claims (1)

[Claims] A magnetic recording and reproducing device that records and reproduces video signals as a group of inclined discontinuous recording tracks on a magnetic tape using a rotating magnetic head, which uses 44 types of pilot signals of different frequencies for tracking control sieves during recording. are sequentially switched for each recording track and recorded on the magnetic tape by a rotating magnetic head along with a video signal as a recording track inclined with respect to the longitudinal direction of the magnetic tape, and during playback, records adjacent to the front and rear of the recording track to be reproduced are recorded. In the tracking side leg method, the relative position between the recording trunk and the reproducing scanning locus of the reproducing magnetic head is controlled using a tracking error signal corresponding to the level difference of the crosstalk signal of the pilot signal reproduced from the trunk. During fast-forward playback in the reverse direction, a tracking error signal is obtained using a fixed configuration with a reference pilot signal for obtaining a tracking error signal, and the tracking error signal is synchronized with the rise or fall of a signal obtained by dividing the head switching signal by %. A tracking control method for a magnetic recording/reproducing device characterized in that a sample and hold is performed using a pulse signal, and the rotational phase of a motor is controlled using the sample and hold output signal as a phase error signal of a cab stan phase control system.