JPS5823659B2 - Kaiten Hetsudonosokudo Seigiyo Cairo - Google Patents

Description

[Detailed Description of the Invention] Recording video signals etc. on a tape using a rotating head,
Further, when reproducing from this, it is necessary to always keep the rotational speed of the rotary head constant.

Conventionally, a speed control circuit for this purpose is configured as shown in FIG. 1, for example.

That is, in the figure, 1 and 2 are rotating magnetic heads, which are rotated 180 degrees to each other.
The magnetic tapes are mounted at angular intervals of
It runs diagonally across an 80° angle range.

Although not shown, magnetic pieces that rotate together with the heads 1 and 2 are provided, and detection magnetic heads 5 and 6 are also provided on the fixed part, so that when the magnetic pieces come to the rotation angle position indicated by A, the head 5 A pulse signal PA is obtained, and a pulse signal PD is obtained from the head 6 when the rotation angle position shown by D is reached a little later than this.

Then, the pulse signal PA (FIG. 2A) obtained from the head 5 is supplied to the monostable multivibrator 8 through the amplifier 7, and from this pulse signal PB (
B) in the same figure is obtained, which is supplied to the trapezoidal wave generator 9, from which a trapezoidal wave signal PC (C in the same figure) is obtained, which is supplied to the sampling circuit 10, while the pulse signal obtained from the head 6 PD (D in the same figure) is supplied to the sampling circuit 10 through the amplifier 11, the slope part of the trapezoidal wave signal pc is sampled by the pulse signal PD, and its output is supplied to the motor 3 through the hold circuit 12 and the DC amplifier 13. Ru.

Therefore, the rotation of the motor 3 is controlled so that the middle part of the slope part of the trapezoidal wave signal pc is always sampled.
Heads 1 and 2 rotate at a constant speed of 30 Hz.

In this case, for example, a phase control circuit for synchronizing the head 1 and 20 rotational phases with the video signal to be recorded during recording is as follows.

That is, the vertical synchronization signal Pv (FIG. 2 E) extracted from the video signal to be recorded is supplied to the monostable multivibrator 14, from which a frame synchronization pulse signal pF (FIG. 2 F) is obtained, which is a trapezoidal signal. A trapezoidal wave signal PG (G) is obtained from the wave generator 15, which is then supplied to the sampling circuit 16, while a pulse signal PD from the head 6 obtained through the amplifier 11 is fed to the delay monostable multi-channel This is supplied to the vibrator 17 to obtain a pulse signal PH (H in the figure) with an appropriate pulse width, which is further supplied to the monostable multivibrator 18 to obtain a pulse signal PI (which is a delayed version of the pulse signal PD). ■) in the figure is obtained, and this is supplied to the sampling circuit 16, where the slope part of the trapezoidal wave signal PG is sampled by the pulse signal P1, and its output is supplied to the monostable multivibrator 8 of the speed control circuit through the hold circuit 19. By changing the time constant of the pulse signal p
The pulse width of B and thus the position of the sloped portion of the trapezoidal signal pc is changed.

Therefore, the rotation of the motor 3 is controlled so that the middle part of the slope of the trapezoidal wave signal pG is always gated, and the heads 1 and 2 rotate so that their rotational phases are synchronized with the vertical synchronization signal pv.

However, in this conventional circuit, based on the pulse signal PA obtained from one detection head 5,
The comparison signal pc is the other detection spatula.

Since the phase is compared with the same (30 Hz pulse signal PD) obtained from Doro, and detection is performed only once per rotation, there is a drawback that the response speed of the control is slow.

Furthermore, in this case, the distance between the heads 5 and the 60-degree angle has to be relatively small, so there is also a drawback that the detection sensitivity is low.

The present invention eliminates these drawbacks, and the speed control circuit according to the present invention will now be explained together with the phase control circuit with reference to FIGS. 3 and 4.

In FIG. 3, reference numerals 21 and 22 are rotating magnetic heads, which are mounted at an angular interval of 180° from each other as described above.
is rotated in the direction of the arrow, and the magnetic tape (not shown) is caused to run diagonally along the guide drum 4 over an angular range of 180 degrees.

In the present invention, although not shown in the drawings, magnetic pieces that rotate together with the heads 21 and 22 are provided, and detection magnetic heads 25 and 26 are provided at positions of the fixed part that are approximately symmetrical to the rotation axes of the heads 21 and 220. When the magnetic piece is at the rotation angle position indicated by Pl, the head 25 outputs a pulse signal S.
A is obtained, and when the rotational angle position shown by P2 is reached by rotating approximately 180 degrees from this point, the head 26 outputs a pulse signal sB.
be obtained.

Then, the pulse signal SA (fourth pulse signal) obtained from the head 25 is
A) is supplied to the synthesizer 28 through the amplifier 27, while a pulse signal SB (B in the same diagram) obtained from the head 26 is supplied to the delay monostable multivibrator 3 through the amplifier 29.
0, from which a pulse signal Sc (C in the same figure) is obtained,
This is further supplied to the monostable multivibrator 31, and by adjusting the time constant of the monostable multivibrator 30 in advance and selecting the pulse width of the pulse signal Sc, the monostable multivibrator 31 allows the magnetic piece to P
The pulse signal sD (
D) in the same figure is obtained.

Then, this pulse signal SD is supplied to the synthesizer 28 and synthesized with the Tehalus signal SA.
One composite pulse signal SE (E in the figure) is obtained every half rotation.

This composite pulse signal SF is supplied to the monostable multivibrator 32, and from this, for example, the width τ is 8TrL.
sec pulse No. m SF (FIG. F) is obtained, and this is supplied to the monostable multivibrator 33, from which, for example, a pulse signal SG (with the same pulse width τ2 < 8 m sec) is obtained.
G) in the figure is supplied to the trapezoidal wave generator 34 to obtain a trapezoidal wave signal sH (H in the figure), which is supplied to the sampling circuit 35, and a synthesized pulse signal from the synthesizer 28. S.

is supplied to the sampling circuit 35, and the slope portion of the trapezoidal wave signal sH is sampled by the composite pulse signal sE,
The output is supplied to the motor 23 through a hold circuit 36 and a DC amplifier 37.

Therefore, so that the middle part of the slope part of the trapezoidal wave signal sH is always sampled by the composite pulse signal SE,
That is, the middle part of the slope part of the trapezoidal wave based on the pulse signal SA is sampled by the pulse signal sD based on the pulse signal SH, and conversely, the middle part of the slope part of the trapezoidal wave based on the pulse signal SB is sampled by the pulse signal SA. The rotation of the motor 23 is controlled so as to be sampled,
Heads 21 and 22 rotate at a constant speed of 30 Hz.

For example, a phase control circuit for synchronizing the rotational phases of the heads 21 and 220 with the video signal to be recorded during recording can be configured as follows.

That is, the vertical synchronization signal P extracted from the video signal to be recorded
v (■ in Figure 4) is supplied to the monostable multivibrator 38, which generates a frame synchronized pulse signal SJ (J in the same figure).
This is supplied to the trapezoidal wave generator 39 to obtain the trapezoidal wave signal SK (K in the same figure), which is then sent to the sampling circuit 4.
0, and on the other hand, the pulse signal SA from the head 25 obtained through the amplifier 27 is supplied to the protection monostable multivibrator 41 to obtain a pulse signal SL of an appropriate pulse width (L in the same figure), This is further supplied to the monostable multivibrator 42 to obtain a pulse signal sM (M in the figure) which is a delayed version of the pulse signal SA, which is then supplied to the sampling circuit 40 to obtain a slope portion of the trapezoidal wave signal SK. is sampled using a pulse signal sM, and its output is supplied to the motor 23 through a hold circuit 43 and a DC amplifier 37.

Therefore, the rotation of the motor 23 is controlled so that the middle part of the slope part of the trapezoidal wave signal sK is always sampled, and the rotation phase of the heads 21 and 22 is set to the vertical synchronization signal p.
Rotate in synchronization with v.

Note that switching of the reproduction output from the heads 21 and 22 during reproduction is not shown, but for example, a flip-flop circuit is set by the pulse signal SA, and the pulse signal S
This can be done using the signal sN (N in FIG. 4) obtained by resetting by D.

According to the circuit of the present invention described above, the comparison signal based on the pulse signal SA obtained from one detection head 25 is phase-compared with the signal S1) based on the pulse signal sB obtained from the other detection head 26, and The other detection head 2
The comparison signal based on the signal sB obtained from 6 is compared in phase with the pulse signal SA obtained from one of the detection heads 25, and since detection is performed twice per rotation, the control response speed is becomes faster.

Furthermore, since the angular spacing between the heads 25 and 260 is a large angle close to 180°, the detection sensitivity is increased.

When phase control is also performed, in the conventional circuit shown in FIG. 1, the time constant of the monostable multivibrator 8 is changed after an error signal is obtained at the time of the pulse signal PIO, and the pulse width of the pulse signal PB is changed. However, as in the above-described circuit of the present invention, the error signal from the sampling circuit 40 for phase control is used for speed control. When the signal is combined with the error signal from the sampling circuit 35 for supplying the signal to the motor 23, such a control delay does not occur.

Note that the signal generator that generates the two detection signals that indicate the rotational position of the rotating head is not limited to an electromagnetic one that combines a magnetic piece and a fixed magnetic head as shown in the example in the figure, but may also be an optical one. An electrostatic material may also be used.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of the conventional circuit, Fig. 2 is a waveform diagram for explaining it, Fig. 3 is a system diagram of an example of the circuit of the present invention, and Fig. 4 is a waveform diagram for explaining it. be. 21 and 22 are rotating magnetic heads, 23 is a motor, 25 and 26 are fixed magnetic heads as first and second signal generators, 30 to 33 are monostable multivibrators, 34
is a trapezoidal wave generator, 35 is a sampling circuit, and 36 is a ° hold circuit.

Claims (1)

[Claims] 1. One magnetic body attached to a rotating body, and first and second signal generators that are provided with an angular interval slightly smaller than 180° in the rotational direction of the rotating body and detect passage of the magnetic body. a monomulti delay circuit that delays the output signal of the second signal generator by a time such that the angular spacing is substantially equivalent to 180°; an output signal of the monomulti delay circuit and the first signal; It has a synthesizer that synthesizes the output signals of the generator, and a trapezoidal waveform circuit to which the output signal of the synthesizer is supplied, and the output signal of the trapezoidal waveform circuit and the output signal of the synthesizer are compared in phase. A speed control circuit for a rotary head, wherein the rotational speed of the rotary body is controlled by a comparison error signal.