JPH0676254A - Device for detecting track deviation amount of dt head - Google Patents

Abstract

PURPOSE:To detect a track deviation amt. of a DT head at a high speed and with high accuracy. CONSTITUTION:Reproduced signals of A channel and B channel outputted from reproducing heads 52A, 52b in the DT head 5 are supplied to an RF envelope signal detection circuit 7, and RF envelope signals SA1, SB1 superposed with a change component by the track deviation amt. and a wobbling component are detected here. Then, by a tracking error detection circuit 8, a wobbling compont is extracted and a tracking error signal SC is outputted. The tracking error signal SC corresponds to the track deviation amt. of the DT head 5. Thereby, since the track deviation amt. is detected only using the RF envelope signal, a wobbling frequency is possible to be increased, and thus, the track deviation amt. is detected at a high speed and with high accuracy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a track shift amount detecting device for a DT head.

[0002]

2. Description of the Related Art Recent VTRs are required to improve the recording density of magnetic tapes. As one means for achieving this, a narrow track is being developed. With the progress of narrow tracks, it has become necessary to perform tracking at high speed and with high accuracy so that the reproducing head accurately follows a recorded track.

As a method of causing the reproducing head to follow the recording track, a method of using a DT (dynamic tracking) head has been conventionally known. As is well known, the DT head is a reproducing head mounted on an actuator such as a piezoelectric element. During reproduction, tracking is performed by detecting a deviation amount between the reproducing head and the track and correcting the deviation amount with an actuator.

As a method of detecting the amount of deviation between the reproducing head and the track, the reproducing head is wobbled.
There is a way to do it. In this method, the envelope signal of the reproduction RF signal output from the reproduction head when the reproduction head is wobbled is extracted. On the other hand, the amount of displacement of the reproducing head due to wobbling is detected by a strain gauge or the like, and the amount of increase / decrease of the envelope signal is synchronously detected with this amount of displacement to detect the amount of track deviation of the reproducing head.

[0005]

By the way, as described above, the recent magnetic tape has a narrow track, and in order to perform tracking adjustment of the reproducing head with respect to such a narrow track, for example, a wobbling frequency is used. Therefore, it is necessary to detect the track deviation amount at high speed and with high accuracy.

However, if the wobbling frequency is set too high, the frequency may exceed the natural frequency of the actuator in some cases. In this case,
Since the actuator causes high-order vibrations and it becomes impossible to accurately detect the displacement amount of the actuator, there is a problem that it becomes impossible to accurately detect the track deviation amount of the reproducing head.

Further, as a method for detecting the track deviation amount of the reproducing head, a detecting method utilizing the fact that the reproducing signal read timing is changed when the reproducing head causes a track deviation when reproducing an azimuth recorded signal However, since the change amount of the read timing of the reproduction signal is extremely small, it is very difficult to detect the change amount of the read timing in the case of the narrow track, which is not suitable for practical use.

Therefore, the present invention has solved the above-mentioned problems, and even in a narrow track, the track deviation of the DT head capable of detecting the deviation amount between the reproducing head and the track at high speed and with high accuracy. A quantity detecting device is proposed.

[0009]

In order to solve the above-mentioned problems, in the present invention, a DT for reproducing a magnetic tape in which two channels are simultaneously recorded by azimuth magnetic recording.
In a track deviation amount detecting device for a head, a set of reproducing heads for simultaneously reproducing two tracks recorded on a magnetic tape at the same time, a wobbling means for wobbling the reproducing heads with a predetermined amplitude, and a reproducing RF output from the reproducing heads. A reproduction RF envelope signal extracting means for extracting an envelope signal of the signal and a wobbling component extracting means for extracting a wobbling component from the reproduction RF envelope signal are provided.

[0010]

In FIG. 1, the rotational speed of the capstan and the control signal CTL are supplied to the microprocessor 1,
Here, a drive signal for driving the reproducing heads 52A and 52B of the DT head 5 is generated. This drive signal also includes a wobbling signal.

On the other hand, the reproduction signals of the A and B channels output from the reproduction heads 52A and 52B are RF.
The RF envelope signals SA1 and SB1 which are supplied to the envelope signal detection circuit 7 and in which the change amount due to the track deviation amount D (FIG. 7) and the wobbling component are superimposed are detected (FIGS. 8A and 8A). .

Next, the wobbling component is extracted by the tracking error detection circuit 8 and the tracking error signal S
C (FIG. 8 (S)) is output. The tracking error signal SC corresponds to the track deviation amount D of the reproducing heads 52A and 52B. The tracking error signal SC is added to the drive signal by the adder circuit 2 (FIG. 1), and this is supplied to the actuator 51 of the DT head 5 via the filter 3 and the amplifier 4. As a result, the reproducing heads 52A and 52B are driven so as to correct the track deviation amount D.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a track deviation amount detecting device for a DT head according to the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a drive unit for a DT head to which a track shift amount detecting device for a DT head according to the present invention is applied. In the figure, a microprocessor 1 receives a capstan rotation speed from a capstan FG (not shown) and a control signal CTL reproduced from a magnetic tape T. Then, in the microprocessor 1, D based on the rotation speed of the capstan and the control signal CTL.
A drive signal for the T head 5 is generated and supplied to the adder circuit 2. The drive signal includes a wobbling signal for wobbling the DT head 5.

The output of the adder circuit 2 is supplied to the actuator 51 of the DT head 5 via the filter 3 and the amplifier 4. The DT head 5 is built in the drum 6, and as shown in FIG.
The reproducing heads 52A and 52B for reproducing 1 and T2 are provided. A channels and B channels are simultaneously recorded on the tracks T1 and T2 by azimuth recording.

Further, as shown in FIG.
The width b1 of the tracks A1 and 52B is wider than the width b2 of the tracks T1 and T2.
It is set to coincide with the boundary of T2. By this, the centers of the reproducing heads 52A and 52B and the track T
An offset α is provided between the center of T1 and the center of T2.

In the case of the just track, the boundary between the reproducing heads 52A and 52B coincides with the boundary between the tracks T1 and T2, and when the DT head 5 is wobbled, both reproducing heads are reproduced as shown in FIG. 3A. 52
A and 52B meander over both tracks T1 and T2.

At this time, the widths of the reproducing heads 52A and 52B tracing the tracks T1 and T2, respectively, are as shown in FIG.
As shown in B, the dimensions are symmetrical. Playback head 52A,
The reproduced RF signal output from 52B is supplied to the RF envelope signal detection circuit 7 (FIG. 1). Here, FIG. 3C
The reproduced RF envelope signals of the A channel and the B channel are extracted as shown in (3) and are supplied to the tracking error detection circuit 8.

If the DT head 5 is displaced toward the track T1 by 1/2 of the wobbling amplitude as shown in FIG. 4A, the trace width of the track T1 changes as shown in FIG. 4B. The trace width of the track T2 is constant. Therefore, the reproduced RF envelope signal changes for the A channel as shown in FIG.
The channel amount is constant.

On the contrary, when the DT head 5 is displaced to the track T2 side by 1/2 of the wobbling amplitude as shown in FIG. 5A, the trace width of the track T2 is changed as shown in FIG. 5B. Thus, the trace width of the track T1 becomes constant. Therefore, as shown in FIG. 6C, in the reproduced RF envelope signal, the A channel is constant and the B channel is changed.

Now, the output of the RF envelope signal detection circuit 7, that is, the RF envelope signal of the A channel and B
The RF envelope signal of the channel is supplied to the tracking error detection circuit 8, and the track deviation amount D of the DT head 5 is detected by the procedure described below.

FIG. 6 shows details of the tracking error detection circuit 8. Now, for example, it is assumed that the tracks T1 and T2 meander in a predetermined range L as shown in FIG. Assuming that the DT head 5 is moving on an accurate track, the track deviation amount D of the DT head 5 is the same as the moving amount of the tracks T1 and T2.

The A-channel RF envelope signal SA1 and the B-channel RF envelope signal SB1 input to the tracking error detection circuit 8 have the track shift amount D as shown in FIGS. 8A and 8A, respectively. The waveform has a wobbling component superimposed on the change component. The wobbling is performed at a high frequency such that the period is shorter than the period of the tracks T1 and T2.

Here, since the connecting portion between the reproducing head 52A and the reproducing head 52B overlaps longer than the wobbling amplitude, the track shift amount D is larger than the wobbling amplitude.
Even when is small, the wobbling component is superimposed only on the signal SA1 or SB1 output from the reproducing head 52A or 52B on one side, that is, the side opposite to the side on which the tracks T1 and T2 have moved. That is, in the case of the just track, the wobbling component is not detected, and the detection ratio of the wobbling component increases as the track deviation amount D increases.

These RF envelope signals SA1 and S
B1 are band pass filters 81A and 81B, respectively.
(FIG. 6). This band pass filter 8
The pass bands of 1A and 81B are, for example, about 400 to 5 kHz, and the output signals SA2 and SB2 thereof are shown in FIG.
As shown in (d), the waveform has only the wobbling component extracted.

The output signals SA2 and SB2 are output to peak hold circuits 82A and 82B and subtraction circuits 83A and 83B.
Is supplied to. In the peak hold circuits 82A and 82B, the signal SA input as shown in FIGS.
2, the peak signals SA3 and SB3 are taken out from SB2, and are supplied to the subtraction circuits 83A and 83B.

Then, in the subtraction circuit 83A on the A channel side, the band pass filter 81 is converted from the peak signal SA3.
The output signal SA2 of A is subtracted to form a signal SA4 in which the wobbling component has moved to the positive side, as shown in FIG. Further, in the B-channel side subtraction circuit 83B, the peak signal SB3 is subtracted from the output signal SB2 of the band pass filter 81B, so that the wobbling component is moved to the negative side as shown in FIG. It becomes SB4.

Output signal SA of subtraction circuits 83A and 83B
4 and SB4 are low-pass filters 84A and 84A, respectively.
84B, where low-frequency components SA5 and SB5 are extracted as shown in FIGS. Output signals SA5 and SB5 of the low pass filters 84A and 84B
Are added by the adder circuit 85, and as a result, a tracking error signal SC corresponding to the track deviation amount D of the DT head 5 is obtained as shown in FIG.

This tracking error signal SC is supplied to the adder circuit 2 (FIG. 1), where the microprocessor 1
And is supplied to the actuator 51 of the DT head 5. As a result, the actuator 51 is driven so as to correct the track deviation amount D of the DT head 5.

Even when the widths of the reproducing heads 52A and 52B are narrower than the widths of the tracks T1 and T2, the track deviation amount D can be detected. However, the reproducing head 5
If the width of 2A, 52B becomes narrower, the S / N ratio of the reproduced signal becomes worse, and if the width of the reproducing heads 52A, 52B becomes too wide, the adjacent tracks of the same azimuth will also be reproduced at the same time. Good results are obtained by setting the width of the heads 52A and 52B to about 1.5 times the width of the tracks T1 and T2.

[0031]

As described above, according to the present invention, in a track deviation detecting device for a DT head which reproduces a magnetic tape in which two channels are simultaneously recorded by azimuth magnetic recording, two tracks of the magnetic tape are simultaneously recorded. A set of reproducing heads for simultaneously reproducing data, a wobbling means for wobbling the reproducing head with a predetermined amplitude, a reproducing RF envelope signal extracting means for extracting an envelope signal of a reproducing RF signal output from the reproducing head, and a reproducing RF envelope. The wobbling component extracting means for extracting the wobbling component from the signal is provided.

Therefore, according to the present invention, the track deviation amount of the reproducing head can be detected without using the displacement amount of the reproducing head, so that the wobbling frequency of the reproducing head can be increased. For example, it is possible to detect the track deviation amount of the reproducing head with respect to the narrow track at high speed and with high accuracy.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a DT head driving device to which a track deviation amount detecting device for a DT head according to the present invention is applied.

FIG. 2 is a diagram illustrating an example of a DT head.

FIG. 3 is a diagram for explaining movement of a reproducing head and a reproduction RF envelope signal in the case of a just track.

FIG. 4 is a diagram for explaining the movement of the reproducing head and the reproducing RF envelope signal when the DT head 5 is displaced toward the track T1 side.

FIG. 5 is a diagram for explaining the movement of the reproducing head and the reproducing RF envelope signal when the DT head 5 is displaced toward the track T2 side.

FIG. 6 is a configuration diagram showing an example of a tracking error detection circuit 8.

FIG. 7 is a diagram illustrating a track deviation amount D of a DT head that occurs when tracks T1 and T2 are misaligned.

FIG. 8 is a diagram illustrating a waveform of a signal in the tracking error detection circuit 8.

[Explanation of symbols]

 1 Microprocessor 2 Addition Circuit 3 Filter 4 Amplifier 5 DT Head 6 Drum 7 RF Envelope Signal Detection Circuit 8 Tracking Error Detection Circuit 51 Actuator 52A, 52B Playback Head 81A, 81B Band Pass Filter 82A, 82B Peak Hold Circuit 83A, 83B Subtraction circuit 84A, 84B Low pass filter 85 Addition circuit T Magnetic tape T1, T2 Track

Claims (3)

[Claims] 1. A track shift amount detecting device for a DT head for reproducing a magnetic tape in which two channels are simultaneously recorded by azimuth magnetic recording, wherein a set of reproducing heads for simultaneously reproducing two simultaneously recorded tracks of the magnetic tape. Wobbling means for wobbling the reproducing head with a predetermined amplitude, reproducing RF envelope signal extracting means for extracting the envelope signal of the reproducing RF signal output from the reproducing head, and the wobbling component from the reproducing RF envelope signal. A track deviation detecting device for a DT head, comprising a wobbling component extracting means for extracting. 2. The track deviation amount detecting device for a DT head according to claim 1, wherein a width of the reproducing head is different from a width of the track. 3. The DT according to claim 1, wherein the center of the reproducing head and the center of the track are displaced from each other.
Head track deviation detection device.