JP3271198B2 - DT head track deviation detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Recent VTRs have been required to improve the recording density of magnetic tapes. As one means for achieving this, a narrow track is being promoted. As the use of narrow tracks has progressed, it has become necessary to perform high-speed and high-accuracy tracking for causing a reproducing head to accurately follow a recorded track.

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

[0004] 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 that. In this method, an envelope signal of a 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 or decrease of the envelope signal is synchronously detected based on the amount of displacement, thereby detecting the amount of track deviation of the reproducing head.

[0005]

By the way, as described above, a recent magnetic tape is formed into a narrow track. In order to perform tracking adjustment of a reproducing head with respect to such a narrow track, for example, the frequency of wobbling is set. , It is necessary to detect the track shift amount with high speed and 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 higher-order vibration, and it is impossible to detect an accurate displacement amount of the actuator, there is a problem that it is impossible to accurately detect a track shift amount of the reproducing head.

As a method of detecting the track shift amount of the reproducing head, a detecting method utilizing the fact that when the reproducing head causes a track shift when reproducing a signal recorded in azimuth, the read timing of the reproduced signal changes. However, since the amount of change in the read timing of the reproduced signal is very small, it is very difficult to detect the amount of change in the read timing in the case of a narrow track, and is not suitable for practical use.

Accordingly, the present invention has been made to solve the above-mentioned problem, and a track shift of a DT head capable of detecting a shift amount between a reproducing head and a track at a high speed and with high accuracy even in a narrow track. A quantity detection device is proposed.

[0009]

In order to solve the above-mentioned problems, according to the present invention, there is provided an apparatus for detecting a track shift amount of a DT head which reproduces a magnetic tape recorded simultaneously on a plurality of channels. A plurality of reproduction heads for simultaneously reproducing the plurality of tracks, wobbling means for wobbling the reproduction head at a predetermined amplitude, a reproduction RF envelope signal extraction means for extracting an envelope signal of a reproduction RF signal output from the reproduction head, A wobbling component extracting means for extracting a wobbling component from the reproduced RF envelope signal; extracting an RF envelope signal for each channel by the reproduced RF envelope signal extracting means from outputs of the plurality of reproducing heads wobbled by the wobbling means; Extracted for each channel From each of the RF envelope signal, and extracts the wobbling component of each channel by wobbling component extraction means, a predetermined signal processing to the signals of the wobbling component extracted for each said channel
Signal processing for each channel that has undergone predetermined signal processing.
In this case, one track shift amount is detected by calculation .

[0010]

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

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

Next, a wobbling component is extracted by a tracking error detection circuit 8 to generate a tracking error signal S.
C (FIG. 8C) is output. This tracking error signal SC corresponds to the track shift amount D of the reproducing heads 52A and 52B. The tracking error signal SC is added to the drive signal by the adding 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. Thus, the reproducing heads 52A and 52B are driven so as to correct the track deviation D.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a track shift 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 driving apparatus for a DT head to which the apparatus for detecting a track deviation amount of a DT head according to the present invention is applied. In FIG. 1, a microprocessor 1 receives a capstan rotation number from a capstan FG (not shown) and a control signal CTL reproduced from a magnetic tape T. Then, in the microprocessor 1, based on the rotation speed of the capstan and the control signal CTL, D
A drive signal for the T head 5 is generated and supplied to the addition circuit 2. The drive signal includes a wobbling signal for wobbling the DT head 5.

The output of the adder 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 the signals T1 and T2 are provided. Channels A and B are simultaneously recorded on tracks T1 and T2 by azimuth recording.

Further, as shown in FIG.
The width b1 of A and 52B is wider than the width b2 of tracks T1 and T2.
It is set to coincide with the boundary of T2. As a result, the center of the reproducing heads 52A and 52B and the track T
1, an offset α is provided between 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. When the DT head 5 is wobbled, as shown in FIG. 52
A and 52B meander over both tracks T1 and T2.

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

When the DT head 5 is shifted toward the track T1 by half the wobbling amplitude as shown in FIG. 4A, for example, the trace width of the track T1 changes as shown in FIG. 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 component is constant.

Conversely, when the DT head 5 is shifted toward the track T2 by half the wobbling amplitude as shown in FIG. 5A, the trace width of the track T2 changes as shown in FIG. Thus, the trace width of the track T1 becomes constant. Therefore, as shown in FIG. 9C, the reproduced RF envelope signal has a constant amount for the A channel and changes for the B channel.

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

FIG. 6 shows details of the tracking error detection circuit 8. Now, it is assumed that, for example, the tracks T1 and T2 meander in a predetermined range L as shown in FIG. Here, assuming that the DT head 5 is moving on an accurate trajectory, the track shift amount D of the DT head 5 is the same as the movement 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 a track shift amount D as shown in FIGS. A waveform in which the wobbling component is superimposed on the change component is obtained. Note that wobbling is performed at such a high frequency that the cycle is shorter than the cycle of the tracks T1 and T2.

Here, since the connection between the reproducing head 52A and the reproducing head 52B overlaps longer than the wobbling amplitude, the track shift amount D is smaller than the wobbling amplitude.
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, on 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 ratio of the detected wobbling component increases as the track shift amount D increases.

These RF envelope signals SA1, S
B1 is a band pass filter 81A, 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 their output signals SA2 and SB2 are shown in FIG.
As shown in (d), a waveform is obtained by extracting only the wobbling component.

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

In the subtraction circuit 83A on the A channel side, the band pass filter 81
The output signal SA2 of A is subtracted, and becomes a signal SA4 in which the wobbling component moves to the plus side as shown in FIG. Further, in the subtraction circuit 83B on the B channel side, the peak signal SB3 is subtracted from the output signal SB2 of the band-pass filter 81B, and a signal such that the wobbling component moves to the minus side as shown in FIG. SB4.

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

The tracking error signal SC is supplied to an adder 2 (FIG. 1), where the microprocessor 1
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 shift amount D of the DT head 5.

The track deviation D can be detected even when the widths of the reproducing heads 52A and 52B are smaller than the widths of the tracks T1 and T2. However, the reproducing head 5
If the width of the reproduction heads 2A and 52B is reduced, the S / N ratio of the reproduction signal is deteriorated, and if the width of the reproduction heads 52A and 52B is too wide, the adjacent tracks of the same azimuth are reproduced at the same time. Good results can be 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, the present invention relates to a DT for reproducing a magnetic tape recorded simultaneously on a plurality of channels.
In a head track deviation amount detecting device, a plurality of reproducing heads for simultaneously reproducing a plurality of tracks simultaneously recorded on a magnetic tape, a wobbling means for wobbling the reproducing head with a predetermined amplitude, and a reproducing RF output from the reproducing head Reproducing RF for extracting signal envelope signal
An envelope signal extracting unit for extracting a wobbling component from the reproduced RF envelope signal; A signal is extracted, and a wobbling component extracting unit extracts a wobbling component for each channel from each RF envelope signal extracted for each channel, and a predetermined wobbling component signal is extracted for each channel . Signal processing is performed and predetermined signal processing is performed.
By adding the signals of the respective channels, one track shift amount is detected.

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

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a DT head driving device to which a device for detecting a track deviation amount of 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 illustrating the movement of a reproducing head and a reproduced 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 reproduced RF envelope signal when the DT head 5 is shifted to the track T1 side.

FIG. 5 is a diagram illustrating the movement of the reproducing head and the reproduced RF envelope signal when the DT head 5 is shifted toward the track T2.

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

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

FIG. 8 is a diagram for explaining signal waveforms in the tracking error detection circuit 8;

[Explanation of symbols]

 DESCRIPTION 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 Reproduction 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 (1)

(57) [Claims] An apparatus for detecting a track shift amount of a DT head for reproducing a magnetic tape recorded simultaneously on a plurality of channels, comprising: a plurality of reproducing heads for simultaneously reproducing a plurality of simultaneously recorded tracks on the magnetic tape; Wobbling means for wobbling the head with a predetermined amplitude; reproduction RF envelope signal extraction means for extracting an envelope signal of a reproduction RF signal output from the reproduction head; wobbling component for extracting the wobbling component from the reproduction RF envelope signal Extracting means for extracting an RF envelope signal for each channel from the outputs of the plurality of reproducing heads wobbled by the wobbling means by the reproduced RF envelope signal extracting means, and extracting each RF envelope signal for each channel. Enbero The wobbling component extracting means extracts a wobbling component for each channel from the loop signal , performs predetermined signal processing on the signal of each wobbling component extracted for each channel , and performs the predetermined signal processing. Signal for each channel
A DT head track shift amount detecting device for detecting one track shift amount.