JPH01317203A - Video signal recording and playback device - Google Patents

Abstract

PURPOSE:To produce a desired control signal within a cylinder and to control the inside of the cylinder by detecting the local magnetic field generated by a magnetic field generating device via a magnetic head fixed to a rotary drum at a point close to this drum. CONSTITUTION:When an AC power supply is applied to a magnetic field generating device 1, a magnetic field is generated at a point extremely close to the device 1. Thus an induced current flows to a magnetic head 3a or 3b when this head passes through a point close to the device 1. This current signal is amplified by a preamplifier and a control signal is produced by a monostable multivibrator which stabilized at 3T/4. Then the head 3a (or 3b) is kept under a recording state for a period during which a cylinder is turned by 3/4 right after the head 3a passes through a point close to the device 1. The head 3a (3b) is reset to a reproduction state after the 3/4-turn of the cylinder. As a result, an R/P control signal can be transmitted within the cylinder with no contact with a rotary drum.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a video signal recording and reproducing apparatus equipped with a preamplifier in a rotating cylinder. .

BACKGROUND OF THE INVENTION In a VTR for recording and reproducing wideband video signals, a preamplifier is built into a rotating cylinder and the wiring capacity between the magnetic head and the preamplifier is reduced to achieve a wider band. In addition, in such a VTR, it is effective to rotate the rotary drum at a higher speed or to divide the recording into multiple channels for recording and reproduction. However, since the number of magnetic heads increases when multi-channel divisional recording and reproduction is performed, a rotary transformer for transmitting recording and reproduction signals is also required. This hinders the miniaturization, weight reduction, and cost of the equipment.

Therefore, by sharing the magnetic head and rotary transformer during recording and playback, or by using one rotary transformer for the two magnetic heads fixed at 180 degrees on the rotating drum, recording and playback signals can be transmitted. There arises a need to reduce the number of transmission paths. To do this, it is necessary to transmit the R/P control signal and head switching signal within the cylinder, and conventionally a slip ring or the like has been used as a means for transmitting the signal.

FIG. 6 shows a video signal recording and reproducing apparatus with a built-in preamplifier cylinder using the conventional R/P control signal transmission method.

In the figure, 31 is a magnetic head, 32 is a preamplifier,
33 is a rotary transformer, 34, 35, 36 is a switching transistor, 37 is an inverter circuit, 38 is a slip ring, 39 is a switch, 40 is a recording amplifier, 41
is a regenerative amplifier. Furthermore, the portion surrounded by a broken line indicates that it is inside the cylinder.

When the R/P control signal is H, the switching transistors 34 and 35 are both in the ON state and the switching transistor 36 is in the OFF state, and the recording current flows to the magnetic head, equivalent to that shown in FIG. 7(a). On the other hand, when the R/P control signal is L, switching transistors 34 and 35 are both OFF, and switching transistor 36 is ON.
The state becomes equivalent to that shown in FIG. 7(b), and the minute reproduction signal detected by the magnetic head is amplified by the preamplifier 32 and sent to the reproduction system.

Problems to be Solved by the Invention In the example shown in Fig. 6, a slip ring is used as a means for transmitting the R/P control signal into the cylinder, so it is particularly difficult for the cylinder to rotate at high speed. If this happens, there is a problem that the slip ring will wear out severely and the life of the device will be shortened.

In view of the above, an object of the present invention is to provide a video signal recording and reproducing device with a built-in preamplifier cylinder, which is equipped with a non-contact signal transmission device that does not wear out.

Means for Solving the Problems The present invention provides a video signal recording and reproducing device equipped with a preamplifier in a rotating cylinder, in which a magnetic head fixed to a rotating drum is placed near the magnetic head when it is in a tape winding position. A switch that installs a magnetic field generator capable of generating a local magnetic field, connects a control signal generation circuit to the preamplifier connected to the magnetic head, and switches a signal path to the magnetic head to the control signal generation circuit. This is a video signal recording and reproducing device characterized by connecting.

According to the above-described configuration, the present invention generates a desired control signal inside the cylinder by detecting the local magnetic field generated by the magnetic field generating device at a point near the magnetic head fixed to the rotating drum, and this signal causes the inside of the cylinder to be controlled. It controls the

Embodiment FIG. 1 shows a video signal recording and reproducing apparatus using a control signal transmission method according to an embodiment of the present invention. 1 is a magnetic field generator, 2 is an AC power supply, 3a13b is a magnetic head,
4 is a rotating cylinder, and 5 is a magnetic tape. When AC power is applied to the magnetic field generating device 1, a magnetic field is generated in the immediate vicinity.

Since the rotating cylinder 4 rotates counterclockwise at a constant speed, when the magnetic head 3a or 3b passes near the magnetic field generating device 1 as shown in FIG. 1, an induced current flows in the magnetic head 3a or 3b, respectively. In this embodiment, this induced current is used to transmit a desired control signal into the cylinder.

First, a method of transmitting the R/P control signal into the cylinder will be explained. Figure 2 shows the R/P in one embodiment of the present invention.
A block diagram of a control signal transmission method is shown. 6 is a magnetic head, 7 is a preamplifier, 8 is a rotary transformer, 9.10.
11 is a switching transistor, 12 is an inverter circuit, 13 is a comparator, 14 is a monostable multivibrator, 15 is a recording/reproduction changeover switch, 16 is a recording amplifier, 17 is a reproduction amplifier, 18 is a magnetic field generator, and 19 is a magnetic field generator operation. The switch 20 is an AC power source. Furthermore, the portion surrounded by a broken line indicates that it is inside the cylinder.

During recording, since the R/P control signal is H, the magnetic field generator operation switch 19 is turned on, and an alternating current flows through the magnetic field generator 18, generating a magnetic field in the vicinity thereof. FIG. 3 shows this situation in the form of a time chart. Here, the magnetic head 6 is connected to the magnetic field generating device 1 like the magnetic head 3a in FIG.
Let te be the time when the cylinder is near 8, and the cylinder is 1
Let T be the rotation time. FIG. 3(a) shows the alternating current flowing through the magnetic field generator 18, and FIG. 3(b) shows that the induced current by the magnetic field generator 18 flows into the magnetic head 6 at time tfI. This signal is shown in the same figure (
C) is amplified by the preamplifier 7, and the same figure (d) is amplified by the preamplifier 7.
), the noise portion is cut by the comparator 13. Furthermore, as shown in FIG. 2(e), a monostable multivibrator 14 stabilized at 3T/4 generates a control signal triggered by the output signal of the comparator, and this signal is connected to each switching transistor.

That is, when this control signal becomes H, the switching transistors 9, 10, and 11 are turned ON, ON, and OFF, respectively, and the recording current is transmitted to the magnetic head 6 via the rotary transformer 8, equivalent to that shown in FIG. 7(a). flows. Then the third
As can be seen from Figure (e), at time ti++3T/4, the control signal becomes L, and the switching transistor 9.
10111 are turned OFF, OFF, and ON, respectively, and no recording current flows through the magnetic head 6. In other words, in FIG. 1, immediately after the magnetic head 3a passes near the magnetic field generating device 1, the magnetic head 3a is in the recording state until it makes 3/4 rotation of the cylinder, and when it completes 3/4 rotation, the magnetic head 3a enters the reproduction state. It returns to the state.

The magnetic head 3b also switches between recording and reproduction using the same circuit in a different system with a phase difference of T/2 from the magnetic head 3a, and while the two magnetic heads are in contact with the tape, the recording state is always maintained, and the magnetic field generating device is in the recording state. Make sure that the nearby area is always in a reproducing state.

Also, during reproduction, since the R/P control signal is L, the magnetic field generator operation switch 19 is in the OFF state, and the magnetic field generator 18
No alternating current flows and no magnetic field is generated. Therefore, the output of the monostable multivibrator 14 is always L, so the switching transistors 9, 10, and 11 are turned off.
, OFF, and ON, and the preamplifier 7 operates as shown in FIG. 7(b).

As described above, in the apparatus shown in FIG. 1, if the system shown in FIG. 2 is used, it becomes possible to transmit the R/P control signal into the cylinder without contacting the rotating drum.

Second, a method of transmitting the head switching signal into the cylinder will be explained. FIG. 4 shows a block diagram of a head switching signal transmission system in an embodiment of the present invention. 21a and 21b are magnetic heads, 22 al 22
b is a preamplifier, 23 is a comparator, 24 is a monostable multi-vib break, 25 is a flip-flop, 26 is a head switch, 27 is a rotary transformer, 28 is a regenerative amplifier, 28 is a magnetic field generator, and 30 is an AC power source.

Furthermore, the portion surrounded by a broken line indicates that it is inside the cylinder.

Here, t is the time from when the magnetic head 21a or 21b is in the vicinity of the magnetic field generator 29 like the magnetic head 3a in FIG. 1 until it touches the recording track on the tape, and the time it takes for the cylinder to rotate once A time chart when T is shown in FIG. FIG. 5(a) shows the alternating current flowing through the magnetic field generator 29, and FIG.
), when the magnetic head 21a comes close to the magnetic field generator 29, the induced current by the magnetic field generator 29
1a. Similarly, the magnetic head 21
When b comes to a point near the magnetic field generator 29, the same figure (C)
As shown in FIG. 2, an induced current by the magnetic field generator 29 flows to the magnetic head 21b.

These signals are sent to preamplifiers 22a and 22b, respectively.
After being amplified by , the signal is added as shown in FIG. 2(d), and the noise portion is cut by the comparator 23 as shown in FIG. 2(e). Furthermore, as shown in the figure (f), a control signal is generated by a monostable multivibrator 24 that is stabilized at t, and is connected to a flip-flop 25 that operates according to the falling edge of this signal. I am getting a wave signal. If the magnetic heads 21a and 21b are located at 180 degrees from each other on the rotating drum and the number of rotations of the drums is constant, the output signal of the flip-flop 25 should be a rectangular wave with period T.

As can be seen from FIG. 4, this signal becomes a control signal for the head switch 26, which switches the signals detected by the magnetic heads 21a and 21b at a cycle of T/2 and outputs the signals to the regenerative amplifier via the rotary transformer 27. There is.

As described above, in the apparatus shown in FIG. 1, if the system shown in FIG. 4 is used, it becomes possible to transmit the head switching signal into the cylinder without contacting the rotating drum.

Although the embodiment shown in FIG. 2 and the embodiment shown in FIG. 4 have been explained separately, these circuits can be combined to form an R/P
Needless to say, both the control signal and the head switching signal can be transmitted in a non-contact manner.

As described in detail, according to the present invention, it is possible to transmit a control signal into the cylinder without contacting the rotating drum by using the induced current generated by the magnetic head fixed to the rotating drum. It is possible to prevent equipment life from being shortened due to wear.

[Brief explanation of the drawing]

FIG. 1 is a video signal recording and reproducing device according to an embodiment of the present invention, FIG. 2 is a block diagram of an R/P control signal transmission device in the same embodiment, FIG. 3 is a time chart in the same system, and FIG.
The figure is a block diagram of the head switching signal transmission device in the same embodiment, Figure 5 is the time chart 1 in the embodiment of Figure 4, and Figure 6 is a built-in preamplifier cylinder using the conventional R/P control signal transmission system. type video signal recording and reproducing device,
FIG. 7 is an equivalent diagram of the inside of the cylinder during recording and reproduction. 1.18.29...Magnetic field generator, 2.20.30.
・・AC power supply + 3a+ 3b+ 6+ 21
a+ 21b...magnetic head, 7+ 22 a,
22 b... Preamplifier, 8.27... Rotary transformer, 9, 10111... Switching transistor, 13.23... Humparator, 14.24...
Monostable multivibrator, 25... flip-flop. Name of agent Patent attorney Toshio Nakao and 1 other = 12 = Figure 7 (α) ■

Claims (1)

[Claims] a magnetic head fixed to a rotating drum; a preamplifier connected to the magnetic head and provided within a rotating cylinder; and capable of generating a local magnetic field in the vicinity of the magnetic head when the magnetic head is at a position other than the tape winding position. A video signal recording and reproducing apparatus comprising: a magnetic field generating device; a control signal generating circuit connected to the preamplifier; and a switch provided in the control signal generating circuit for switching a signal path to the magnetic head.