JPS5916162A - Control signal reproducing device - Google Patents

Abstract

PURPOSE:To reproduce a control signal stably even in an extremely low speed, by using a magnetic flux response type head in a VTR. CONSTITUTION:A magnetic flux response type element (MR head) 54 used as a control head 19 is arranged in correspondence with control signals 41-43 on a magnetic tape 20 to reproduce these signals. The MR head 54 is connected to a power source 51 through a bias resistance 52, and an electric signal corresponding to the resistance variation of the MR head 54 is inputted to a non-inverted input side 53 of an operational amplifier 55. An amplified reproduced control signal is obtained in an amplifier output 59. A low pass filter part 64 permits only low frequency drift components due to the temperature variance of the MR head to pass through and feeds back them negatively to the operational amplifier 55, and therefore, the low frequency drift is not inputted to a waveform shaping part 71, and the reproduced control signal very stable against the low frequency disturbance is obtained in the output 59. A reference voltage obtained by dividing the power source voltage and the reproduced control signal 59 are compared with each other in voltage to obtain the control signal converted into rectangular waves in an output 69.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control signal reproducing device useful for video tape recorders and the like.

Conventionally, in video signal magnetic recording and reproducing devices using magnetic tape, such as video tape recorders, a control signal indicating the reference phase at the time of recording recorded on the magnetic tape was reproduced using a wire-wound ring head. . Such a wire-wound ring head has the characteristic that control signals can be recorded and reproduced using a single head. However, the playback output level is proportional to the relative speed between the magnetic tape on which the control signal is recorded and the wire-wound ring head.
When the relative speed is slow, the signal-to-noise ratio of the reproduction control signal becomes poor, and when the relative speed is extremely slow, or when the reproduction stops, there is a problem that the control signal is not reproduced.

The present invention solves all of the above-mentioned problems, and provides a control signal reproducing device that uses a magnetic flux-flexible head to stably reproduce signals even at extremely low speeds.

An embodiment of the present invention will be described below with reference to FIGS. 1 to 6. FIG. 1 is a schematic diagram of a main part of a video tape recorder in a playback mode using a control signal playback device according to an embodiment of the present invention. In the same figure, 1,
2 is a video head, 3 is a rotational phase detection magnet, and these are attached to a rotating disk 4. A rotational phase detector 6 is installed on the fixed part corresponding to the magnet 3. The rotating disk 4 is rotationally driven by a DC motor 6.

The output signal of the frequency generator 7 attached to the DC motor 6, the output signal of the rotational phase detector 5, and the reference oscillator 1
The output signal of 0 is supplied to the rotation rad servo circuit 8.

The output signal of the rotary head servo 8 is supplied to the DC motor through the drive circuit 9. In this way, phase control of the rotating disk 4 during reproduction is performed. magnetic tape 20
is driven at a constant speed in the direction of arrow 21 by a capstan 11 and a pinch roller (not shown). Capstan 11 is connected to pulley 12. Belt 13. It is driven by a DC motor 16 via a 14-metal pulley. A capstan servo circuit 18Vcd is supplied with an output signal of a frequency generator 16 for detecting the full rotational speed of the DC moke 15 and an output signal of a reference oscillator 100.

Furthermore, the reproduction output of the control head 19 is supplied to the capstan servo circuit 18 via the amplifier 23. These control the speed and phase of the capstan 11.

An example of a recording pattern of a magnetic tape is shown in FIG.

In Fig. 2, magnetic tonks 31, 32, 33° 34
．． 35.36 is the recorded video track and 41.4
2.43 is the recorded control signal.

FIG. 3 is a circuit diagram showing a specific example of the control signal reproducing device of this embodiment.

In the figure, numeral 54 is a magnetoresistive element (hereinafter referred to as MR head), which is a type of magnetic flux response type element used as the control node 19, and is used as a control signal as shown in Fig. 2 recorded on the magnetic tape. 41, 42, and 43, and are arranged so as to reproduce the same. The MR head 54 is connected to the power supply 51 through the entire bias resistor 52, and an electrical signal corresponding to the resistance change of the MR head 64 is input to the non-inverting side 53 of the operational amplifier 55. The resistors 56 and 57 determine the entire gain of the amplifier section 58, and an amplified reproduction control signal is obtained at the amplifier output 59. 64 is a low pass filter section,
Of the amplified output of the MR head, which has a strong temperature dependence, only the low frequency drift components due to temperature fluctuations are passed through, and by negative feedback to the operational amplifier 55 of the amplifier section 58, low frequencies that are inconvenient to the waveform shaping section 71 are removed. Drift error is removed, and a reproduction control signal that is extremely stable against low frequency disturbances is obtained at the output 59.

Reference numeral 71 denotes a waveform shaping section, which inputs the power supply voltage divided by resistors 66 and 67 as a reference voltage to 70 and compares the voltage with the reproduction control signal, thereby obtaining a rectangular wave control signal as an output 69.

In addition, the magnetic tape 2o when reproducing the control signal
If the traveling speed of the motor is stopped or extremely low, it is possible to create an AC amplifier that eliminates low frequency drift by coupling the amplifier section with a capacitor 73, as shown in FIG.

However, as shown in FIG.
5, when the output terminal 69 of the amplifier 55 stops due to the charge discharge of the capacitor 73
An output like the broken line 86 appears, and when running again, the playback control signal becomes 84.8 as shown in Figure 5.
5, an inconvenient state may occur transiently in which a rectangular wave signal cannot be formed using the reference voltage 81 of the waveform shaping section.

FIG. 6 is a waveform diagram of various parts of this embodiment under the same conditions as shown in FIG. In this embodiment, the transiently generated drift component is caused by the operational amplifier 65 and resistors 56 and 5 shown in FIG.
7, the amplifier gain or amplification is negative feedback, and the reproduction control signal 8 is different from that in Figure 6 because it enters a steady state in a short period of time.
This has the advantage that a rectangular wave signal 90.91 corresponding to 4.85 can be obtained.

As described above, according to the present invention, control signals can be accurately and stably reproduced even when the tape is running at an extremely low speed or stopped even when the temperature changes.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the main part of a video tape recorder in a playback mode using a control signal playback device according to an embodiment of the present invention, and FIG. 2 is a diagram showing a recording pattern of a magnetic tape.
Fig. 3 is a circuit diagram of the main part of the same device, Fig. 4 is a circuit diagram showing another example of the control signal regenerative amplifier of the same device, and Fig. 5 is a circuit diagram showing another example of the control signal regenerative amplifier of the same device.
This figure is an output waveform diagram of the same amplifier, and FIG. 6 is an output waveform diagram of the same device under the same conditions as the waveform diagram shown in FIG. 5. 64... Magnetoresistive (MR) head, 56
゜62...Operational amplifier (operational amplifier), 60.
61...Low pass filter, 68...
operational amplifier. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 3
Figure 4 Figure 5 #iXI] 閤

Claims (2)

[Claims] (1) A magnetic flux responsive head for reproducing a control signal recorded on a magnetic tape, an amplifier for amplifying the reproduction control signal from the magnetic flux responsive head, and a low frequency drift component separated from the output of the amplifier. A control signal reproducing device comprising: a negative feedback circuit for negatively feeding back the low frequency drift to the amplifier; and a waveform shaping circuit for shaping the output of the amplifier into a rectangular wave signal. (2) The control signal reproducing device according to claim 1, wherein the magnetically responsive head is a magnetoresistive head or a Hall effect head.