JPS639178Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention is a signal reproducing device in which a tape is intermittently run in the opposite direction to that during recording, and a plurality of heads with different recording azimuths are used to perform slow reproduction in the reverse direction. The present invention relates to a tape running control device in a tape running system.

First, with reference to FIG. 1, an example of a tape running control device in a VTR that enables conventional variable speed playback will be described.

Such VTRs involve a process of stopping the running of the magnetic tape for a predetermined period of time, and a process of controlling the magnetic tape.
By alternately repeating the process of running the vehicle at a standard speed by one pitch of the CTL signal, slow playback at a desired speed is performed. this
In addition to a pair of rotating magnetic heads Ha and Hb, which are divided at an angle of 180° and have different azimuths in their magnetic gaps, the VTR also has a magnetic head Hb, which has the same azimuth as the magnetic head Ha, and records video signals on the magnetic head Hb. Auxiliary rotating magnetic heads Ha' are arranged at angular intervals corresponding to 1.25H (H is the horizontal period) on the recording track (slant track) of the magnetic tape. Then, the tracks of the same field on the magnetic tape are still reproduced for (N-1) frame periods by the magnetic heads Ha, Ha', and then the tracks of the next two fields are played by the magnetic heads Ha, Hb.
Standard playback is performed for one frame period, and then the above-mentioned still playback is performed again, and by repeating this, slow playback at 1/N of the standard speed is performed.

FIG. 1 shows a control circuit for a direct current motor that directly drives a capstan in order to intermittently feed the magnetic tape in this manner. 1 is a DC motor that drives the capster, and 2 is its control circuit (drive circuit). Reference numeral 3 denotes a controller that controls whether or not the motor 1 rotates and its direction. 4 and 5 are control signal input terminals, 6
~9 are monostable multivibrators. The controller 3 is supplied with output pulses from the vibrators 7 and 9.

Input terminal 4 has an RF signal whose waveform is shown in Figure 2A.
A switching pulse SWP is supplied. The period of this pulse SWP corresponds to one frame period.
FIG. 2A shows magnetic heads Ha, Hb, and Ha' whose RF reproduction signals are switched by this pulse.

The vibrator 6 is triggered by the falling edge of the pulse SWP. FIG. 2B shows the waveform of the output pulse M6 of the vibrator 6, which rises at the falling edge of the pulse SWP. The time constant of this vibrator 6 is made to be variable according to the above-mentioned N, and here, for example, N=3 is selected, so that the time width of the output pulse M6 is longer than the 2 frame period, and the time constant of the output pulse M6 is longer than the 2 frame period, and the 3 frame period is The time constant is selected to have a value that does not exceed .

The vibrator 7 is triggered on the rising edge of the output pulse M6. FIG. 2C shows the waveform of the output pulse M7 of the vibrator 7, the rising edge of which coincides with the rising edge of the output pulse M6. This output pulse M7 is a pulse for normal rotation of the motor 1, and the motor 1 is rotated for a period of time width Tf.
A positive DC voltage is applied to. This time range
Tf is selected so as not to exceed one frame period.

The input terminal 5 is supplied with a reproduction control signal CTL whose waveform is shown in FIG. 2D. The vibrator 8 is triggered by this signal CTL.
FIG. 2E shows the waveform of the output pulse M8 of the vibrator 8. The time constant of this vibrator 8 is made variable, and if the time width τ of its output pulse M8 is varied by adjusting a tracking volume (not shown) provided in the time constant circuit, Tracking adjustment is possible.

The vibrator 9 is triggered by the falling edge of the output pulse K8. FIG. 2F shows the waveform of the output pulse M9 of the vibrator 9, which rises at the falling edge of the output pulse M8 and has a time width Tr. This output pulse M9 is a pulse for reversing the motor 1, that is, braking the motor 1, and has a time width of
A reverse DC voltage is applied to the motor 1 during the period Tr. This time width Tr is selected to a value that is sufficient for the motor 1 to stop and not to reverse rotation.

If there are multiple standard running speeds of the magnetic tape, the time constants of the vibrators 7 and 9 should be adjusted accordingly.
That is, the time width of the output pulse is varied.

Thus, during slow playback of the VTR, the magnetic tape is intermittently fed by the motor 1.

Next, the relationship among the magnetic head, recording track, and reproduction signal during slow reproduction will be explained with reference to FIGS. 3 and 4 for forward and reverse reproduction, respectively. In FIGS. 3 and 4, different Ha, Hb, and Ha' of the selected magnetic head are shown on the left side, and the vertical axis is time, and the records sequentially formed on the magnetic tape are shown in the checkered frame. Track (video signal track for each field)
A ₀ , B ₀ , A ₁ , B ₁ , A ₂ , B ₂ , ... are shown. still,
The difference in recording azimuth of recording tracks is shown by A and B.

First, FIG. 3 will be explained. L-FD shows an example of the center line of the scanning locus of the magnetic head on the magnetic tape in the standard speed forward playback mode, and the magnetic heads Hb and Ha alternately record tracks...
Regenerate the signals of B ₁ , A ₂ , B ₂ , A ₃ , B ³ ....

L-S ₁ shows an example of the center line of the scanning locus of the magnetic head on the magnetic tape in the static reproduction mode,
Recording tracks A ₂ are alternately recorded on magnetic heads Ha and Ha′.
play repeatedly. _LS2 shows another example of the scanning locus of the magnetic head on the magnetic tape in the static reproduction mode, in which recording track _A3 is repeatedly reproduced by magnetic heads Ha and Ha' alternately.

L-SFD shows an example of the center line of the scanning locus of the magnetic head on the magnetic tape in the forward slow playback mode, and the diagonally shaded part shows the part where the reproduced signal is obtained in the scanning locus. This trajectory L-SFD transitions as a trajectory L-S ₁ →L-FD→L- _S2 . That is,
In sequence, magnetic head Ha′ reproduces recorded track _A2 , magnetic head Ha reproduces recorded track _A2 , magnetic head Hb reproduces recorded track _B2 , magnetic head Ha reproduces recorded track _A3 , and so on. Recorded track _A3 is reproduced by magnetic head Ha'. The waveform of this reproduced signal (high frequency signal) is shown in FIG.

Next, FIG. 4 will be explained. L-RV shows an example of the center line of the scanning locus of the magnetic head on the magnetic tape in the standard speed reverse playback mode, and the magnetic heads Ha and Hb alternately record tracks...A ₃ ,
Regenerate the signals of B ₂ , A ₂ , ....

L-S ₁ shows an example of the center line of the scanning locus of the magnetic head on the magnetic tape in the static reproduction mode,
Recording tracks A ₂ are alternately recorded on magnetic heads Ha and Ha′.
play repeatedly. _LS2 shows another example of the scanning locus of the magnetic head on the magnetic tape in the static reproduction mode, in which recording track _A3 is repeatedly reproduced by magnetic heads Ha and Ha' alternately.

L-SRV indicates an example of the center line of the scanning locus of the magnetic head on the magnetic tape in the reverse slow reproduction mode, and the diagonally shaded portion indicates the portion of the scanning locus where the reproduced signal is obtained. This locus L-SRV transitions from the locus L-S ₂ to L-RV to L-S ₁ . That is, the magnetic head Ha' sequentially reproduces the recorded track _A3 , the magnetic head Ha reproduces the recorded track _A3 , the magnetic head Hb reproduces the recorded track _B2 , and the magnetic head Ha reproduces the recorded track _A2 . The recorded track _A2 is reproduced by the magnetic head Ha'. The waveform of this reproduced signal (high frequency signal) is shown in FIG.

By the way, the above-mentioned VTR has the following problem, especially in slow backward playback. That is, in the case of reverse slow playback, if the center line L-SRV of the scanning locus of the magnetic head on the magnetic tape in FIG. It will happen.

To prevent this, the following two conditions must be satisfied. The speed at which the magnetic head Hb scans the recording track B is extremely close to the standard speed. The aim is to ensure that the widthwise center of the working gap of the magnetic head Hb scans the widthwise center line of the recording track B.

In view of this, the present invention allows a tape on which signals are recorded by a plurality of heads with different recording azimuths on adjacent tracks to be intermittently run in the opposite direction to the running direction during recording, and when the tape stops running. Especially in a signal reproducing apparatus which sometimes continuously reproduces the signal of one track with the head of the first recording azimuth, and when the tape is running, the signal of the other track with the head of the second recording azimuth. Taking the above points into consideration, we would like to propose a tape running control device that hardly generates noise on the screen.

In such a tape running control device, the present invention has the following features:
A drive circuit that supplies drive pulses to a capstan motor that drives the tape is provided with means for adjusting the timing of generation of the drive pulses.

An embodiment of the present invention will be described below with reference to FIG. 7, in which parts corresponding to those in FIG. 1 are given the same reference numerals. This embodiment is also a case in which the present invention is applied to a control circuit for a DC motor that directly drives a capstan in a VTR similar to that described in FIG. A DC motor 1 is directly connected to a capstan (not shown). During slow reproduction, the magnetic tape is fed in steps by the motor 1, that is, by the capstan. The rotation speed of the capstan is, for example, 2 Hz when the tape runs at a standard speed. 2 is a drive circuit for this motor 1, and 20 is a frequency generator provided in relation to the motor 1. This generator 20 consists of a magnetic disk 21 (the circumferential surface of which is magnetized as N, S, N, S, etc., with, for example, 90 N and S poles each) that rotates together with the motor 1.
and a pair of flux-responsive fixed magnetic heads 22A and 22B facing the circumferential surface of the magnet disk 21. The gap between the magnetic heads 22A and 22B is selected so that the phase difference between the reproduction frequency signals F _A and F _B is 90 degrees. That is, the magnetic heads 22A, 22B
Let Lh be the interval between the magnetic poles N and S, and Lm be the pitch between the magnetic poles N and S, then Lh=(n+1/4)Lm. However, n is n=0, 1, 2, . . . . This is to supply the frequency signals FG _A and FG _B to the frequency multiplier circuit 23 to obtain a frequency signal 8FG (see FIG. 8D) multiplied by 8. This frequency signal 8FG is the motor 1
The output is the same whether the rotation is forward or reverse.
Note that the multiplication ratio of this frequency multiplier circuit 23 is arbitrary. Depending on the multiplication ratio, the magnetic heads 22A, 22
It is sufficient to select the interval B.

Next, the drive circuit 2 will be explained in detail. Reference numeral 3 denotes a controller that controls whether or not the motor 1 rotates and its direction. The controller 3 has two input terminals 3a and 3b, one input terminal 3a is supplied with a pulse width modulation signal PWM as a motor drive signal, and the other input terminal 3b is supplied with a rotation direction switching signal RD. be done.

From the input terminal 24 to the D-type flip-flop circuit 2
Start signal ST' (not shown) is connected to the D input terminal of 6.
is from input terminal 25 to its clock C input terminal.
The RF switching pulse SWP (see FIG. 2A) is supplied, and the signal from its non-inverted output terminal is supplied to the variable delay circuit 45 as timing adjustment means for the start pulse ST, and the delay circuit 45 outputs the start signal ST ( (see FIG. 8A) is output. The start signal ST is pulsed SWP (Fig. _2A ) at time P1.
This is a signal that rises with a predetermined phase relationship with (see). The delay amount of this delay circuit 45 is mainly variable during reverse slow playback, and may be zero during forward slow playback.

Brake start signal BS (see Figure 8 B, Figure 2 D)
(with respect to the control signal CTL) is supplied from the input terminal 27 to the non-inverting trigger input terminal of the monostable multivibrator 28. This brake start signal BS rises at time _P2 . The time width of the output pulse M28 (see Fig. 8G) of the monostable multivibrator 28 is
The time width is set to be appropriate for applying a brake to the motor 1 by applying a reverse voltage to the motor 1. Output pulse M28
is a signal that rises at time _P2 and falls at time _P3 .

Frequency signal 8FG from the multiplier circuit 23 (Fig. 8D
) is supplied from the input terminal 29 to the inverting trigger input terminal of the retrigger monostable multivibrator 10 via an inverter. 13 and 14 are capacitors forming a time constant circuit, which are connected in parallel to each other. A switch 15 is inserted in series with the capacitor 14. An output pulse M10 rises from the non-inverting output terminal of the vibrator 10 in synchronization with the rise of the frequency signal 8FG (see Fig. 8E).
is obtained. The time width of the output pulse M10 is τ ₀ when the switch 15 is off, and τ ₁ when it is on (τ ₁ >τ ₀ , for example, τ ₁ =1.5τ ₀ ). In addition, vibrator 1
The output pulse M10 of the inverted output terminal of 0 is not shown in FIG.

Start signal from flip-flop circuit 26
ST is supplied to each set S input terminal of RS type flip-flop circuits 30 and 31. Also, input terminal 2
A brake start signal BS from 7 is applied to the reset R input terminal of flip-flop circuit 30.
Output pulse F30 of flip-flop circuit 30
(See FIG. 8C) is a pulse that rises at time _P1 and falls at time _P2 .

The frequency signal 8FG and the output pulse M10 of the vibrator 10 are supplied to an AND circuit 32, and the output pulse is supplied to the reset R input terminal of the flip-flop circuit 31. The output pulse F31 (see FIG. 8F) of the flip-flop circuit 31 is supplied to an OR circuit 33. This output pulse F31 is a pulse that rises at the rising edge of the start signal ST and falls when the repetition period of the frequency signal 8FG becomes less than τ ₁ .

Thus, the vibrator 10, the flip-flop circuit 31, and the AND circuit 32 control the DC motor 1.
A first control circuit 34 is configured to supply DC voltage to the DC motor 1 at the start-up of the DC motor 1 until the rotational speed of the DC motor 1 reaches a predetermined value.

Output pulse F31 of flip-flop circuit 31
is supplied as a control signal to the switch 15 of the vibrator 10 via the OR circuit 35, and the switch 15 is turned on for the period of the output pulse F31 to set the time width of the output pulse M10 of the vibrator 10 to τ ₁ .
When the repetition period of frequency signal 8FG becomes smaller than τ ₁ , switch 15 is turned off and vibrator 1 is turned off.
The time width of the 0 output pulse M10 is switched to τ ₀ .
Further, the output pulse M28 of the vibrator 28 is sent to the switch 1 of the vibrator 10 via the OR circuit 35.
5 as a control signal, and its output pulse M
28 period output pulse M10 of vibrator 10
Set the time width from τ ₀ to τ ₁ (this τ ₁ can be any other value)
Switch to

The output pulse M10 of the vibrator 10 is supplied to an OR circuit 33. The output of the OR circuit 33 is then supplied to an AND circuit 36. AND circuit 3
6 is the output pulse F of the flip-flop circuit 30.
30 will also be supplied. Furthermore, vibrators 10, 2
8 output pulses M10 and M28 are output from the AND circuit 37
is supplied to

The vibrators 10, 28 and the AND circuit 37 cause a predetermined period of time (P ₂
~ _P3 ) constitutes the second control circuit 38 for supplying the pulse width modulation signal to the DC motor 1.

The outputs of the AND circuits 36 and 37 are supplied to an OR circuit 39, and the output thereof becomes a pulse width modulation signal PWM (see FIG. 8H) supplied to the DC motor 1. Therefore, when the DC motor 1 starts rotating,
In other words, when motor 1 starts up, the duty ratio remains constant until the repetition period of frequency signal 8FG becomes smaller than τ ₁ .
Based on the frequency signal 8FG, the pulse width modulation signal voltage is 100%, that is, a constant amplitude DC voltage (direct current voltage), so that the DC motor 1 starts up quickly, and thereafter the angular velocity of the DC motor 1 is constant. The pulse width modulation signal voltage with the repetition period τ ₀ (<τ ₁ ) obtained by the above calculation is supplied to the DC motor 1 and the speed servo is applied _.
(>τ ₀ ) frequency modulated signal voltage for a predetermined period (P ₂ ~
P ₃ ) is applied to the DC motor 1 to speed up the fall of the DC motor 1 and stop the motor 1 so that the magnetic tape stops at a predetermined position.

Further, the output pulse M of the vibrator 28 and the forward running control signal FWD (not shown in FIG. 8) for the tape from the input terminal 43 are supplied to an AND circuit 40, and its output is supplied to an OR circuit 42. Further, the output pulse F30 of the flip-flop circuit 30 and the reverse running control signal REV (not shown in FIG. 8) for the tape from the input terminal 44 are supplied to an AND circuit 41, and its output is supplied to an OR circuit 42. And OR circuit 42
The output is the rotation direction switching signal RD (see Figure 8 I)
becomes. This rotational direction switching signal RD is "1" when the DC motor 1 is rotating when the tape is running forward, and is "0" when braking, and is "0" when the DC motor 1 is rotating when the tape is running in reverse. It becomes "1" when braking.

Next, the variable delay circuit 45 will be explained with reference to FIG. 9 as well. FIG. 9 shows a diagram corresponding to the above-mentioned FIG. 4 and the RF switching pulse SWP of FIG. 2A in correspondence. τf indicates a field period, which corresponds to 1/2 period of the pulse SWP.

The delay amount of the delay circuit 45 has an optimum value depending on the rise time of the DC motor 1. FIG. 9 shows, for example, when the rise time of motor 1 is 1.4τf, 1τf, 0τf (however, 0τf is an ideal and does not actually exist),
The delay time of the delay circuit 45, that is, the start signal ST
When the delay time with respect to the rise time of the pulse SWP is selected as T ₁ = 0.6τf, T ₂ = 1τf, and T ₃ = 1.5τf, respectively, as shown in curves S ₁ , S ₂ , and S ₃ , the magnetic head Hb The center of the working gap in the width direction is the recording track.
This shows that the center line in the width direction of _B2 is reliably scanned.

Furthermore, since the DC motor 1 is driven by a pulse width modulation signal generated based on the frequency signal from the frequency generator 20, the speed at which the magnetic head Hb scans the recording track B is made extremely close to the standard speed. be able to.

According to the present invention described above, a tape on which signals are recorded by a plurality of heads with different recording azimuths on adjacent tracks is intermittently run in a direction opposite to the running direction during recording, and the running of the tape is stopped. In a signal reproducing device, the signal of one track is sometimes continuously reproduced by the head of the first recording azimuth, and the signal of the other track is reproduced by the head of the second recording azimuth when the tape is running. Therefore, it is possible to obtain a tape running control device that hardly generates noise. Furthermore, even if there are variations in the rise time of the DC motor that drives the tape, it can be easily adjusted so that noise is less likely to occur on the screen.

[Brief description of the drawings]

Fig. 1 is a block diagram showing a tape running control circuit of a conventional VTR, Fig. 2 is a waveform diagram, Figs. 3 and 4 are diagrams showing tracking patterns, respectively, and Fig.
6 and 6 are waveform diagrams, FIG. 7 is a circuit diagram showing an embodiment of the present invention, FIG. 8 is a waveform diagram, and FIG. 9 is a diagram showing tracking patterns and waveforms. Ha, Ha' are the heads of the first recorded azimuth, Hb
1 is a capstan motor, 2 is a drive circuit, and 45 is an adjusting means (variable delay circuit).

Claims (1)

[Scope of utility model registration request] A tape on which signals are recorded by a plurality of heads with different recording azimuths on adjacent tracks is intermittently run in the opposite direction to the running direction during recording, and when the tape stops running, the first recording azimuth is changed. The head reproduces the signal of one of the tracks with the same azimuth as that head, and when the tape is running, the head with the second recording azimuth reproduces the signal of the other track with the same azimuth as that head, so that the recording head reproduces the signal of the other track with the same azimuth as that head. A signal reproducing device for performing slow reproduction of a tape, wherein a drive circuit for supplying drive pulses to a capstan motor that drives the tape to travel is provided with means for adjusting the timing of generation of the drive pulses. Travel control device.