JPS59200590A - Controller of intermediate feed of magnetic tape in slow picture reproduction of four-frequency pilot system vtr - Google Patents

Abstract

PURPOSE:To fix a noise position all the time and eliminate the need for an external adjusting circuit by performing tracking operation in slow reproduction wherein a magnetic tape is run intermittently by a tracking error signal by a four-frequency pilot signal. CONSTITUTION:A switch 40 is closed for fine slow motion. Then, pulses from a demultiplexer 23a are inputted to a switch 12 through a rotation switching circuit 41. The switch 12 supplies a low-pass filter with signals of frequencies f1 and f2 alternately and signals of frequencies f3 and f4 alternately by the next pulse. Consequently, a tracking error is the same with the rotation of the frequencies f1, f2, f3 and f4 in normal reproduction. Then, a signal for controlling a capstan motor 26 is generated from a fine slow pulse (b) and the tracking error signal (c) and the motor 26 runs the magnetic tape 1 by one frame.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic tape feeding monthly interval device during slow image playback in a 4-frequency pilot type VTR.

Generally, VTRs are known that have a plurality of video tracks in a direction crossing the running direction of a magnetic tape.

In such a VTR, the speed of the capstan that runs the magnetic tape or the rotational speed of the rotating video head is controlled so that the rotating head properly scans the video track during playback, so-called tracking. A servo system is provided.

This servo system generally detects the position of the magnetic tape using antibacterial signals called CTLs that are recorded one after another in the running direction of the magnetic tape, but there is also known a 4-frequency pilot system. .

This 4-frequency pilot method uses the video track to
It records a pilot signal superimposed on a video signal, and as shown in FIG. Trucks T3 next to each other one after another
1T4. T5 and different frequencies f1. f2
．． f3. Circulating and recording the above pilot signal of f4,
Moreover, the frequency f1 of the pilot signal recorded on a certain track T2 and the frequency f of the pilot signal recorded on one of the tracks T3 adjacent to this track T2
2 (Cf + - f2), and the difference between the frequency f4 of the pilot signal recorded on the other track T1 < fs
) are selected so that their frequencies are constant.

Incidentally, the frequency f11f2. f3. f4 has the following relationship.

fl-f2=f3-f4-=ct f2fs-"f4fl-β In the figure, arrow A indicates the running direction of the hunting tape 1, and arrow B (-i indicates the running direction of the head.

For example, the same wave number above is f to 100 KHz f2 = 115 K-Hz f3=　160　KTTz f4 = 1451G-Tz.

It has been selected as l. 1 As a recording system and a reproducing system for the pilot signal, a second
The one shown in the figure is known. In FIG. 2, 1 is the magnetic tape, and 2a and 2b are video heads, which alternately run (rotate) in contact with the magnetic tape 1 to obtain the trunk. 6 is video head 2
A and 2b changeover switches, 4 a recording/reproduction changeover switch, 5 a preamplifier, and 6 a bandpass filter. 7
8 is a reference oscillator; 9 is an input terminal for a head switching pulse that drives the switching switch 6 of the video heads 2a and 2b;
1 is an adder, and 10 is an input terminal for chroma and luminance signals.

When recording on this VTR, the switch 4 is switched to the solid line side, and the pilot signal superimposed by the adder 9 is sent to the video head along with the video signal (chroma signal and luminance signal) from the terminal 10 via the switch 6. 2a or 2
b, and is recorded on the magnetic tape 1 as described above. The above-mentioned oscillator 8 passes through frequency dividers 11a, 11b, 11c, and 11d having different frequency division ratios to obtain the pilot signals of frequencies f1-f2-f3-f4, and these pilot signals are used by the above-mentioned head switching. The signals are sequentially and cyclically selected by a changeover switch 12 driven by a pulse, and are supplied to the adder 9 via a low-pass filter 16.

In this way, the frequency f□s f2m f3s f4
The pilot signals are recorded on the magnetic tape 1 in a circular manner on the tracks T, Tz, T3, . . . shown in FIG.

Next, during playback, the selector switch 4 is switched to the dotted line side, and the signals obtained alternately from the heads 2a and 2b (the pilot signal is superimposed on the video signal) are passed through the preamplifier 5 to the band Only the pilot signal passes through the pass filter B and reaches the mixer 14 (the processing system for the reproduced video signal is not directly related to this invention and will therefore be omitted). This mixer 14 has frequency divisions 511a, 11b, 1 from the oscillator 8.
The signals frequency-divided by 1c and 11d are supplied via the switch 12 and the low-pass filter 13, and the reproduced pilot signal is also supplied as described in 5 above, but the heads 2a and 2b should scan this reproduced pilot signal. truck,
For example, in addition to the main pilot signal recorded at Tz in FIG.
1. The pilot signal recorded in T3 is also slightly reproduced. Further, in a steady state, the signal from the filter 16 is selected by the switch 12 so that the main reproduced pilot signal and the signal passing through the low-pass filter 16 have the same frequency, for example, fl.

Therefore, from the mixer 14, the frequency ft of the above signal,
Trunk TI + T3 (7)/<Ilot signal frequency f4. The difference from f2, ie, f+ f2-α fa f+-β is obtained. These differences α and β are separated by bandpass filters 15 and 16, and separated by separate detectors 17 and '18.
The current level is detected and these are detected by the differential amplifier °19.
\Supplied. The above levels are compared in the differential amplifier 19, and a capstan (not shown) for running the magnetic tape 1, for example, is controlled by a comparison error signal, ie, a tracking error signal, from an output terminal 20. Through this control, when the heads 2a and 2b scan a certain track T2 in an appropriate state, the levels of the differences α and β become equal, and this state is stabilized.

By the way, as mentioned above, the track T on the magnetic tape 1
2 When the Y head 2a is scanning, the mixer 14
, ft f2-α fa ft-β is obtained, and the head 2a is misaligned with respect to the track T2 as shown in FIG. When moving relative to the regenerated pilot signal, the one with frequency f4 increases and the one with frequency f2 decreases among the reproduced pilot signals. Therefore, the level of the difference α−f+b decreases, and the level of the difference β−f
The 4ft level is increased and modified so that these l/bels are equal.

On the other hand, in this state, the head 2b next scans the track T37, and the mixer 14 obtains fl-f2-α f2-fa-β, and the head 2b is also relatively moved in the direction of arrow C. Ru. Among the reproduced pilot signals from the head 2b, those with frequency f+ increase, and those with frequency fa decrease. Therefore, the level of the difference α-, ft b increases, and the level of the difference β-f2 fa decreases.

As mentioned in 5 above, when the heads 2a and 2b are moved in the direction of arrow C, the direction of increase/decrease in the levels of the differences α and β is reversed for each head, and therefore the phase of the differential amplifier 19 also differs by 1806 for each head. Become something. In order to correct this, as shown in FIG.
'laO: The signal that has passed through this and the signal that has not passed through this are sent to head 2.
The terminals are alternately supplied each time a and 2b are switched.

On the other hand, when playing slow images in a VTR, if the running speed of the magnetic tape is simply slowed down, the direction of the recording track on the magnetic tape and the direction of the scanning trace of the head will not match, and furthermore, the direction of the recording track and the head Since the positional relationship with the scanning trace is random, the position of the noise on the playback screen determined by this positional relationship is also uncertain, and the noise flows on the screen.

Conventionally, when playing such slow images, in order to eliminate the flow of noise on the screen, a magnetic tape is run intermittently, and still images are played one after another from the stopped magnetic tape, effectively slowing down the image. A reproduced image is obtained. 1
:No, and when the magnetic tape is stopped, the magnetic tape stopping position is controlled so that the positional relationship between the recording track and the locus of the magnetic head is constant (so-called fine throw).

In order to control this stop position, conventionally, as described above; ff1c'
1"L signal was used. However, this case had the following drawbacks.

That is, the relationship between the eTT signal and the video track is determined by the mechanical dimensions of the CTL head and the video head, and by setting these dimensions to a certain value, the VTR.

Mutual tracking is being taken. Therefore, an external tracking volume was required to absorb mechanical variations and adjustment deviations. Even in the case of fine throw with intermittent feed, an external noise position adjustment volume is required.Also, by providing the above circuit, the operating point can be shifted from the optimum state of the operating circuit and the noise adjustment coverage range can be increased. How to mechanically perform CT
Changing the position of the L head or dropping out.

Methods such as correcting by number are known.

This invention eliminates the above-mentioned conventional drawbacks and makes it possible to reproduce slow images by intermittent feeding even in a 4-frequency pilot type VTR. The Foundation provides equipment.

An embodiment of the present invention will be described below with reference to the drawings. 6th
The figure is a block diagram of this embodiment, and FIG. 4 is a time chart showing the operation of FIG. 3.

In FIG. 6, the same reference numerals as in FIG. 2 indicate the same elements. As in the case of FIG. 2, numeral 7 is a terminal to which a head switching pulse is input, 23a is a reducer, and 23b is a mono-multi-by-break, which generates a well-known fine slow pulse. 24 is a terminal to which a tracking error pulse from the terminal 20 explained in FIG. 2 is input, 25 is a well-known clock pulse input terminal, and 26 is a capstan motor for running the magnetic tape at a constant speed. Further, 27 is a first flip-flop, 28 is a second flip-flop, 2
9 is an up/down counter, 60 is a preset circuit for the counter, 31 is a first mono-multi-bi break, 3
2 is a second mono multi-by-break, 66 is an adder, nu is a relay for switching switches 34a and 34b, 35 is a switch, 36 is a Nant gate, 37 is a comparator, and numeral is a voltage for supplying the reference voltage of the comparator. 69 is an inverter.

A head switching pulse (11) as shown in FIG. 4 is inputted from the terminal 7, and this is converted into a fine slow pulse as shown in b by the filter 2 filter a and the mono-multivibrator 23b. This pulse b is input to the recent circuit 30, and the counter 29 is preset. Furthermore, these pulses a and b are input to the reset terminal and set terminal of the first flip-flop 27, respectively! 91, the output shown in e is obtained from this flip-flop. On the other hand, an error signal shown as C is inputted from the terminal 24, and when this signal is less than the basic voltage, a high signal is obtained as the output d of the comparator 37. This signal d and the output e of the flip-flop 27 are input to a Nantes gate 66, from which an output shown at f is obtained. While the output f is low, the counter 29 counts up and adds the clock pulses from the terminal 25.

The second flip-flop 28 is the flip-flop 2
It is set at the falling edge of the output e of the counter 29, and is reset at the falling edge of the output of the counter 29, which will be described later, to output a signal shown at g. During the period when this output g is high, (12) Is the counter 29 a clock pulse? When the count value becomes the same as the preset value by the preset circuit 30, the output of the counter 29 becomes low, thereby resetting the flip-flop 28. When the output g of the flip-flop 28 rises, the first mono multivibrator 31 is triggered, and when it falls (rise via the inverter 39), the second mono multivibrator 32 is triggered. Output i of these mono multi-by-breaks 31 and 32
, j are added to the output g by an adder, and supplied to the output 35, which drives the capstan motor 26.

Further, while the output j of the second mono-multivibrator 32 is low, the switches 34aj34b are switched to the illustrated state, and the motor 26 is rotated in the normal direction.

During the period when the output j is high, the switches 34a and 34b are switched to the opposite side from that shown in the figure, and the motor 26 is supplied with current in the direction of reverse rotation. Figure 4k shows the motor 26.
The application of \*Ff (■ indicates the forward direction, ○ indicates the reverse direction) is shown.

In this way, as shown in FIG. 4 t, after one cycle of the fine slow pulse and the head switching pulse, the motor 26 is accelerated in the forward direction and then rotated in the forward direction at the normal speed.
After that, it is driven in the opposite direction and stops rapidly. period tl
(When stopped, period t2 is during intermittent feeding, and the output j
It can be seen that during the period of )・a, the speed is accelerated, and during the period when the output j is high, the speed is decelerated.

An explanation will be added regarding how the position of the noise on the playback screen becomes constant through the above operation, how to determine the pulse width of the mono multivibrator 61°, and how to form a fine slow pulse. First, to make a fine throw, the motor should rotate from the stop position to feed the tape, and then move to the next stop position without making any noise. The tape movement speed t1 in this case is the same as the fine throw in CTL,
The acceleration time and running deceleration time are determined by the rotational speed of the video head, the inclination of the recorded video track, and the relative speed of the tape. To keep the noise position constant,
Adjustments are made by changing these times. In this example, the up-down counter determines the position of the noise, sends it to the flip-flop, changes the running time of g, and automatically eliminates the noise. is adjusted to a certain position.

In the apparatus shown in FIG. 3, when performing a fine throw operation, the switch 40 is closed. As a result, the pulse from the attenuator 23a is transferred to the rotation switching circuit 41.
is input. When this pulse is not input, as in the case of FIG. 2, the frequency f1. The signal of f2f3-J'4 is circulated and supplied to the low-pass filter 13, but depending on the input of the pulse, the switch 12 switches the frequency f1. f2
signals at frequency f3. f
4 signals are alternately supplied to the low-pass filter 13. This results in a tracking error h (similar to the rotation of frequencies f1-f2-f3.fa during normal reproduction).

A signal for opening the capstan motor 26 is generated from the fine slow pulse b and the tracking error signal C explained in FIG. ) frame) proceed.

This slow speed is determined by the frequency division ratio of the head switching pulse. For example, if the normal speed is fVN and the division ratio is n-→, one frame advances every four head rotations, so the speed is Vs=2x, VN=2 The speed will be 1//2.

As described above, this invention uses a tracking error signal based on a four-frequency pilot signal to perform tracking during slow playback in which the magnetic tape is intermittently fed (-), so the following effects can be obtained. Since the positional relationship between the video trunk and the video head, that is, the noise position, is used as direct information, the noise position can always be kept constant even if there are external factors such as changes in mechanical torque or tracking deviation due to gaps between roof tiles. No additional adjustment circuit is required.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a tape butter (16) for explaining the present invention, FIG. 2 is a block diagram for explaining the present invention, FIG. 6 is a block diagram showing an embodiment of the present invention, and FIG. FIG. 4 is a time chart showing the operation of FIG. 3.

Claims (1)

[Claims] Pilot signals of different frequencies superimposed on video G are circulated and recorded on one track and one rack successively adjacent to it among a plurality of video tracks in a direction crossing the running direction of the magnetic tape. However, the difference between the frequency of the pilot signal recorded on a certain track and the frequency of the pilot signal recorded on one of the tracks adjacent to this track, and the frequency of the pilot signal recorded on the other track. The frequencies of the pilot signals are selected so that the difference between them is one foot, and when a video signal recorded on a certain track is played back, a signal with the same frequency as the pilot signal recorded on that track and the adjacent signal are selected. In a 4-frequency pilot type VTR, a signal with a frequency different from the pilot signal reproduced from both sides of the trunk is extracted and the levels of these signals are compared to obtain a tracking error signal.
A 4-frequency pilot system VT characterized in that tracking is performed using the above-mentioned tracking error signal when playing a slow image by intermittent feeding of a magnetic tape.
A control device for intermittent feeding of a calm tape during slow image playback in R.