JPS6333223B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control signal playback device for a video tape recorder or the like.

Conventionally, in a video signal magnetic recording/reproducing apparatus using a magnetic tape, such as a video tape recorder, a control signal indicating a reference phase at the time of recording recorded on the magnetic tape is reproduced by a wound ring head. In this way, the wound ring head has the advantage that control signals can be recorded and reproduced using a single head. However, since the playback output signal level is proportional to the relative speed between the magnetic tape on which the control signal is recorded and the wound ring head, if the relative speed is slow, the SN ratio of the playback control signal will be poor; Alternatively, there was a problem in that the control signal was not reproduced when it stopped.

The present invention uses a magnetoresistive head, which is a type of magnetic flux responsive magnetic head, to solve the above problems.

Hereinafter, the present invention will be explained based on illustrated embodiments.

FIG. 1 is a block diagram of the main parts of a video tape recorder in playback mode using the present invention. In the figure, 1 and 2 are video heads, 3 is a magnet for detecting rotational phase, and these are attached to a rotating disk 4. A rotational phase detector 5 is installed on the fixed part corresponding to the magnet 3.
The rotating disk 4 is rotationally driven by a DC motor 6. Frequency generator 7 attached to DC motor 6
The output signal of the rotary phase detector 5 and the output signal of the reference oscillator 10 are supplied to a rotary head servo circuit 8. The output signal of the rotating head servo circuit 8 is supplied to the DC motor 6 via a drive circuit 9. Thereby, phase control of the rotating disk 4 during reproduction is performed. The magnetic tape 20 is driven at a constant speed in the direction of an arrow 21 by a capstan 11 and a pinch roller (not shown). The capstan 11 is driven by a DC motor 15 via a pulley 12, a belt 13, and a pulley 14. The capstan servo circuit 18 is supplied with the output signal of the frequency generator 16 for detecting the rotation speed of the DC motor 15 and the output signal of the reference oscillator 10. Furthermore, the reproduction output of the control head 19 is supplied to the capstan servo circuit 18 via the control signal processing circuit 23. These control the speed and phase of the capstan 11.

An example of the recording pattern of the magnetic tape 20 is shown in FIG. In FIG. 2, magnetic tracks 31, 3
2, 33, 34, 35, and 36 are recorded video signal tracks, and 41, 42, and 43 are recorded control signals. An example of the configuration of the control head 19 is shown in FIG. 3, and a connection relationship between the control head 19 and the control signal processing circuit 23 is shown in FIG. FIG. 3A is a schematic side view of the control head 19, and the left end is the magnetic tape 2.
0 is shown. 101 is a magnetoresistive head (hereinafter referred to as MR head) which is a type of magnetic flux responsive magnetic head, and 102 is an MR used as a reference for resistance value.
It's a head. MR head 101 has magnetic tape 2
The control signal 41, 42, or 43 recorded on the 0 is placed in opposition to and reproduces the control signal. The reference MR head 102 is placed at a position where it does not reproduce the control signals 41, 42 or 43 or other signals. Figure 3A
In this case, it is placed at a position away from the magnetic tape 20. 103, 104 and 105 are each MR
The head lead wire is shown. FIG. 3B shows a schematic diagram of the control head 19 viewed from the side that contacts the magnetic tape 20. These MR heads are connected to a differential amplifier 106 as shown in FIG. Lead wire 105 is grounded. The voltage supplied to the power supply terminal 112 is connected to the resistor
MR head 1 via R ₁ and lead wire 103.
01.

On the other hand, the reference MR head 102 is supplied with the output voltage of the digital memory circuit 108 via a resistor R ₂ and a lead wire 104. Note that the digital memory circuit 108 includes a comparator 109 and a 10-bit up/down counter 1.
10, a 10-bit ladder resistance circuit 111, a voltage follower circuit 112, and a switch 113
It consists of The output signals of the MR head 101 and the reference MR head 102 are output to the differential amplifier 10.
6, and is supplied to the digital memory circuit 108 via the output terminal 107 of the control processing circuit 23 and the low-pass filter 115. Low pass filter 115 is composed of resistor 116 and capacitor 117. The cutoff frequency c of the low-pass filter 115 is set to, for example, 0.3Hz. Therefore, when the tape running speed during playback is 1/5 times or more than during recording (that is, when the frequency of the playback control signal is 6Hz or more), the playback control signal supplied to the low-pass filter 115 is After smoothing, only the DC component is supplied to the digital memory circuit 108. The comparator 109, counter 110, resistance circuit 111, and voltage follower circuit 112 that constitute the digital memory circuit 108 perform an analog-to-digital conversion operation when a clock signal is input to the CP terminal of the counter 110.

Also, by stopping the clock signal,
Performs memory operation (hold operation). A clock signal is applied to input terminal 114. When the tape running speed during playback is 1/5 times or more during recording, by closing the switch 113, the digital memory circuit 108 converts the output signal of the low-pass filter 115 from analog to digital, and further converts the output signal of the low-pass filter 115 into digital data. 111 and supplies it to resistor _R2 . For example, if the power supply voltage supplied to the power supply terminal 112 is +12V, the resistance value of the resistor _R1 is 10KΩ, the resistance value of the resistor _R2 is 5KΩ, and the low resistance values of the MR head 101 and the reference MR head 101 are both 100Ω. , low pass filter 115
A voltage of approximately 6V is obtained at the output of the terminal. This means that the system shown in FIG. 4 constitutes a negative feedback loop.

Next, the tape running speed during playback is 1/5 of the recording speed.
When the voltage is less than double, by opening the switch 113, the digital memory circuit 108 enters the hold state, and the voltage applied to the resistor _R2 is the same as when the negative feedback loop was established (approximately 6V in the above example). is given. In this state, the recorded control signals 41, 42 and 43 on the magnetic tape 20
passes the MR head 101, the output terminal 1
07, a reproduction control signal as shown in FIG. 5 is obtained. In FIG. 5, section C indicates that the magnetic tape 20 is running at the same speed as during recording, and section D indicates that the magnetic tape 20 is running at 1/5 the speed during recording. It shows.
In FIG. 5, peaks 141 and 14 of the signal waveform
2 and 143 indicate that control signals 41, 42 and 43 have been reproduced. In Figure 5, the same tape speed and 1/
Although the case of playback at a tape speed of 5 is shown, since the control head 19 uses an MR head, which is a type of magnetic flux responsive head, the control signal can be played back at any tape running speed, including stopping. Can be done. In addition, MR head 10
Since the resistance value of 1 has a strong temperature dependence, the reference MR
Head 102 and differential amplifier 106 are used to cancel out the temperature dependence. This provides a stable reproduction control signal. Also, resistor R ₁ ,
Variations in the resistance value of R ₂ and changes in resistance value due to temperature changes and changes over time are absorbed by the negative feedback loop, so a constant current is supplied to the MR head 101 and the reference MR head. That is, the control signal reproducing device of the present invention automatically changes the voltage supplied to the resistor _R2 in a video tape recorder as illustrated in FIG. As a result, the control signal can be reproduced very stably, regardless of temperature changes and changes over time, and at any magnetic tape running speed, including stoppage.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the main part of an example of a video tape recorder using the present invention in playback mode, Fig. 2 is a diagram showing an example of a recording pattern of a magnetic tape, and Figs. 3 A and B are used in the present invention. FIG. 4 is a schematic configuration diagram showing an example of a control head, FIG. 4 is a circuit configuration diagram of a main part of an embodiment of the present invention, and FIG. 5 is a waveform example diagram of an output control signal. 19... Control head, 23... Control signal processing circuit, 101... Magnetoresistive (MR) head, 102... Reference magnetoresistive (MR) head, 106... Differential amplifier,
108...Digital memory circuit, 109...
Comparator, 110...Up-down counter, 111...Ladder resistance circuit, 113...Switch, _R1 to _R3 ...Resistor.

Claims (1)

[Claims] 1. A control signal recorded on the magnetic tape for transmitting information about the positional relationship between the magnetic tape and the video head during recording is reproduced by a first magnetoresistive magnetic head. In the apparatus, a second magnetic head of a magnetoresistive type having substantially the same characteristics as the first magnetic head is used as a reference for the resistance value of the first magnetic head, and a first resistor is connected to the first magnetic head from a voltage source. A current is caused to flow through the first magnetic head through the magnetic head, and a current is caused to flow through the second magnetic head through a second resistor, thereby reducing the voltage drop in the first magnetic head and the voltage drop in the second magnetic head. amplifying the difference in voltage drop between the differential amplifiers with a differential amplifier, supplying the output voltage of the differential amplifier to a digital memory circuit through a low-pass filter, and supplying the output voltage of the memory circuit to the second resistor; A control signal reproducing device characterized in that the regenerated control signal is obtained from the output terminal of the differential amplifier. 2. In the statement of claim 1, when the running speed of the magnetic tape is above a predetermined speed, the digital memory circuit is a mere signal passing circuit, and when the running speed is below the predetermined speed, the digital memory circuit is A control signal reproducing device characterized in that it is configured to operate as a memory circuit. 3. In claim 1 or 2, the digital memory circuit includes a comparator circuit, an up-down counter having a clock input terminal, and a digital-to-analog converter, and A control signal reproducing device characterized in that clock input to the clock input terminal is prohibited in the following cases.