JPH0426964Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magnetic recording and reproducing device, and can be applied to, for example, a simultaneous playback video tape recorder (VTR).

[Background technology and its problems]

A simultaneous playback VTR is a system in which when a video signal is recorded by a recording head mounted on a rotating drum, this recorded signal is played back by a playback head installed parallel to the recording head. ,
It is a highly reliable VTR in that it can record while checking the recorded state of the video signal on the tape one by one using the playback signal, and the configuration shown in FIG. 2 has been used in the past.

That is, in FIG. 2, the video signal VIDEO input to the recording system 10 is passed through the low-pass filter 11,
FM modulation circuit 13 via clamp circuit 12
and after being FM modulated, the recording amplifier circuit 14
The signals A and 14B are amplified to a sufficiently large signal level necessary for recording, and recorded on the magnetic tape 1 as a recording medium by the A and B recording heads RA and RB.

Thus, the video signal recorded on the tape by the recording system 10 is reproduced by the A and B reproduction heads CA and CB of the reproduction system 20, and the reproduced signal is sequentially passed through the reproduction amplifier circuit 21 and the limiter 22. The FM demodulated reproduced video signal CVID is sent as an output of the reproduction system 20 and checked on a monitor, for example. As shown in FIG. 3, the recording head and the reproducing head are arranged close to each other on the same drum DR so that recording and reproducing can be performed almost simultaneously.

In the configuration shown in Figure 2, if clogging occurs in the head (a condition in which the gap of the head is clogged with magnetic material powder), it will need to be cleaned or replaced.
If this clogging occurs, the reproduction output of the reproduction system 20 will drop to an extremely low signal level, so it can be determined by detecting this.

However, in this case, when clogging occurs and a reproduction signal with a sufficient signal level cannot be obtained through tape 1 to heads CA and CB, the magnetic flux due to the recording current in recording head RA or RB is The recording system 10 and the reproducing system 20 may be unnecessarily coupled because the reproducing head CA and CB directly adjoin each other, and the reproducing system substrate pattern is disposed near the recording system substrate pattern. Therefore, there is a problem in that it is difficult to reliably determine the occurrence of a clogged state due to the influence of unnecessary signals generated in the reproduction system.

In order to prevent unnecessary coupling between the recording system 10 and the reproducing system 20, it is conceivable to make the magnetic shield more complete, for example, but this inevitably increases the size of the structure and cannot be said to be a practically effective means.

[Purpose of invention]

The present invention has been devised in consideration of the above points, and is a magnetic recording system in which clogging detection is virtually unaffected even if there is an unnecessary coupling between the recording system and the reproducing system. The aim is to obtain a playback device.

[Summary of the idea]

In order to achieve this purpose, in this invention,
A slicer is provided to remove small-level unnecessary signals induced in the reproduction system by unnecessary coupling, so that signal components based on unnecessary coupling are not generated at the output end of the reproduction system.

〔Example〕

Hereinafter, an embodiment of the present invention will be described in detail with reference to FIG. 1, in which parts corresponding to those in FIG. 2 are denoted by the same reference numerals.

The recording system 10 of the simultaneous playback VTR has the same structure as the conventional device shown in FIG. They are different.

The slicer 30 includes diodes D1 and D connected in antiparallel to each other that receive the output signal S1 of the regenerative amplifier circuit 21 via coupling capacitors C1 and C2.
2, and provides the limiter 22 with a slice output S2 obtained at a connection point Z between the cathode of the diode D1 and the anode of the diode D2.

Therefore, the voltage at the connection point X on the anode side of the diode D1 is equal to the voltage at the connection point Z as shown in FIG. 4A.
When the first slice voltage VU is higher than the first slice voltage VU, which is higher by the forward voltage VD with respect to VM, the voltage becomes conductive and the signal at the connection point X is applied to the limiter 22. Similarly, in diode D2, the voltage at connection point Y is the voltage at connection point Z.
When it becomes lower than the second slice voltage VL, which is lower than the forward voltage VD from VM, it becomes conductive and provides the signal at the connection point Y to the limiter 22.

The slicer 30 also includes voltage dividing resistors R1, R2, and R3 connected in series between the power supply +B and the ground.
It has a bias circuit consisting of resistors R1 and R2.
By connecting the middle point of the connection to the connection point X, a bias voltage VA (FIG. 4A) is applied to the connection point X.
Thus, the connection point X via the coupling capacitor C1
When the signal vx arrives, the voltage at the connection point X changes with the bias voltage VA as the operating point.
This causes the diode D1 to conduct during the period T1 during which the voltage rises above the first slice voltage VU, and the output signal
vxo (FIG. 4B) is generated at connection point Z.

Also, the midpoint of the connection between resistors R2 and R3 is the connection point Y
A bias voltage is applied to the connection point Y by being connected to
VB (Figure 4A) is given. In this way, when the signal vy arrives at the connection point Y via the coupling capacitor C2, the voltage at the connection point Y fluctuates with the bias voltage VB as the operating point, and during the period T2 in which it is lower than the second slice voltage VL. Diode D2 is made conductive to output signal vyo (Figure 4B)
is generated at the connection point Z.

In the configuration shown in FIG. 1, when no clogging occurs in the head, the recording amplifier circuit 14A
The video signal VIDEO, which has been amplified to a large signal level at 14B and 14B, is recorded on tape 1 at a predetermined recording level by recording heads RA and RB, reproduced by reproduction heads CA and CB, and sent to slicer 30 via reproduction amplification circuit 21. It is given as an input signal S1.

At this time, the input signal S1 of the slicer 30 is
A signal vx is applied to the connection point X via the capacitor C1 and fluctuates with the bias voltage VA as the operating point.
(FIG. 4A), and at the same time, a signal vy (FIG. 4A) which is secondly applied to the connection point Y via the capacitor C2 and fluctuates with the bias voltage VB as the operating point is obtained.

Therefore, when the instantaneous value vx of the input signal S1 becomes higher than the first slice voltage VU during the positive half period of the input signal S1, the diode D1 is made conductive, and the output signal vxo is lowered by the forward voltage VD (FIG. 4B). is supplied to connection point Z on the output side. In a section where the instantaneous value does not exceed the slice voltage VU, the diode D1 cannot be made conductive, so the voltage at the connection point Z maintains a constant value VM.

On the other hand, when the instantaneous value vy of the input signal S1 becomes lower than the second slice voltage VL at the negative half frequency of the input signal S1, the diode D2 is made conductive and the output signal vyo is higher by the forward voltage VD (see Fig. 4). B)
is supplied to connection point Z. However, in this case as well, the diode D2 cannot be made conductive in a section where its instantaneous value does not exceed the slice voltage VL, so the voltage at the connection point Z maintains a constant value VM.

Therefore, from the perspective of the input signal S1 of the slicer 30, the difference between the first slice voltage VU and the operating point VA for its positive half cycle |VU−VA|=|VD
−V1/2| becomes the slice level SL (Fig. 4A), and for the negative half cycle, the difference between the second slice voltage VL and the operating point VB |VU−VB|=|VD
-V1/2| becomes the slice level SL.

Here, the voltage V1 is the potential difference between the connection points X and Y, and can be changed by selecting the value of the bias resistor R2 as necessary.
VA and VB, and therefore the slice level SL can be set.

Therefore, when no clogging occurs, the reproduced signal is applied to the limiter 22 through the slicer 30, and the output signal S2 lowers the signal level of the input signal S1 by the slice level SL, as shown by the solid line L1 in FIG. It has a signal level similar to that of the playback video signal CVID, and this is sent out as the reproduced video signal CVID. Incidentally, a broken line L2 in FIG. 5 shows, for comparison, the relationship between the output signal S1 of the regenerative amplifier circuit 21 and the input signal S2 of the limiter 22 when the slicer 30 is not installed.

On the other hand, if clogging occurs in the head, the regenerative amplifier circuit 21 generates a sufficient signal level.
Since the reproduced signal of RI (FIG. 5) cannot be sent out, the content of the input signal S1 of the slicer 30 becomes an insufficient signal at the signal level of a signal due to unnecessary coupling not via the tape 1.

This low signal level signal is applied to the connection points X and Y through capacitors C1 and C2, which causes the voltage to fluctuate with the bias voltages VA and VB as the operating points, but since the fluctuations are small, the slice voltages VU and VL are I can't get over it.

Therefore, in this state, diodes D1 and D2
Since there is no conduction, the output signal S2 is no longer output from the slicer 30 to the connection point Z. In this way, the output signal S2 is sliced and not output as shown in FIG.

As described above, according to the circuit shown in FIG. 1, when a reproduced signal with a sufficient signal level is captured through the intervention of the slicer 30, the reproduced video signal CVID can be obtained. When a reproduced signal is captured, the unnecessary signal can be removed, so the presence or absence of clogging can be reliably detected simply by determining whether an output signal is obtained from the reproduction system. In this way, the slice level SL can be easily set as required by selecting the value of the resistor R2, and unnecessary signals can be easily removed.

In fact, according to the conventional configuration shown in FIG. 2, the output signal level of the regenerative amplifier circuit 21 due to unnecessary coupling is reduced to -
If it is not attenuated to 50 dB, it will not be possible to detect whether clogging has occurred based on whether or not an output signal is obtained from the reproduction system, but according to the configuration shown in Figure 1, the slice level SL can be reduced by ~
Setting it to around -30 will reduce the level of unnecessary signals.
Even at 30 dB or more, it is possible to suppress the signal output from the reproduction system when clogging occurs. Therefore, the restrictions on wiring patterns and distances between heads that have been imposed for clogging detection can be relaxed accordingly.

An example of a slicer in which the slice level is set to about the forward voltage of a diode is a slicer made by simply arranging two diodes D3 and D4 in antiparallel as shown in FIG.

Furthermore, the element for setting the slice voltage is not limited to those using diodes as shown in Figures 1 and 6; in short, any element that exhibits low voltage characteristics for a predetermined signal level can be used. Furthermore, the present invention is not limited to video tape recorders;
The present invention can also be applied to other magnetic recording and reproducing devices in which unnecessary coupling between the recording system and the reproducing system is a problem.

[Effect of idea]

As described above, according to the present invention, since the reproduction system is provided with a slicer that removes unnecessary signals that appear due to unnecessary coupling between the recording system and the reproduction system, clogging can be detected reliably.

[Brief explanation of the drawing]

Fig. 1 is a block diagram including a partial connection diagram showing the configuration according to an embodiment of the present invention, Fig. 2 is a block diagram showing the configuration of a conventional device, and Fig. 3 shows the mounting of the recording head and reproducing head on the drum. A schematic diagram for explaining the position; FIG. 4 is an operational waveform diagram of each part in the slicer 30 of FIG. 1; FIG. 5 is a schematic diagram showing the relationship between the amplitude levels of the input signal and output signal of the slicer 30;
FIG. 6 is a connection diagram showing the configuration of another slicer. 1...tape, 10...recording system, 20...playback system, 30...slicer, RA, RB...recording head, CA, CB...playback head.

Claims (1)

[Scope of utility model registration request] In a magnetic recording and reproducing apparatus that includes a recording head and a reproducing head on a rotating head, and in which the following reproducing head reproduces a recording signal recorded on a recording medium by a preceding recording head, the reproducing system includes a recording system and a reproducing system. 1. A magnetic recording and reproducing apparatus comprising a slicer for removing low-level components of a reproduced signal that appear due to unnecessary coupling of .