JPH04205811A - Magnetic recording/reproduction device - Google Patents

Abstract

PURPOSE:To achieve on-track positively by learning a curve of a recording track pattern and tracing the recording track according to the curve of this recording track pattern at the time of reproduction. CONSTITUTION:A pattern learning memory circuit 13 memories a pattern output from an envelope maximum value operation circuit 12. Also, an addition circuit 14 gives an output of the envelope maximum value operation circuit 12 to a track pattern compensation circuit 15 and gives an output of the pattern learning memory circuit 13 to the track pattern compensation circuit 15 at the time of reproduction mode according to dynamic tracking for displacing a head. Then, the track pattern compensation circuit 15 judges an optimum displacement direction and displacement quantity of a video head where a maximum envelope is obtained from an output of the addition circuit 14 and then outputs track pattern compensation output of a mix amplifier 8, thus achieving a positive on-track.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a magnetic recording/reproducing device, and in particular, to a magnetic recording/reproducing device that enables reliable on-track recording regardless of bending of the recording track. Regarding.

(Prior Art) Conventionally, when a home video tape recorder (hereinafter referred to as a VTR) plays back a magnetic tape recorded on another VTR, it is necessary to adjust tracking defects caused by mechanical errors. There is a need. The roll pulse from the control head to the reproducing controller 1 and a predetermined reference signal are phase-compared by a phase comparator, and the rotation of the capstan motor is controlled based on the output of the phase comparator. The reference signal is delayed by a monostable multivibrator and then given to the phase comparator, and the user performs tracking adjustment by adjusting the time constant of the monostable multivibrator. Further, recently, VTRs having a digital tracking adjustment function that processes the tracking operation by digital calculation by employing software servo have become popular. These tracking adjustments allow the video head to accurately trace the magnetic tape tracks.

However, the track pattern may be curved due to variations in mechanical precision and adjustment errors in the tape running system. This curve is different for each VTR, and other VTRs
When playing back a magnetic tape recorded on a magnetic tape, the video head may not be able to reliably trace the recorded track.

For this reason, in conventional magnetic recording and reproducing devices, the head width of the video head is made sufficiently large to reliably trace the recording track. However, since the head width is large, there is a problem in that adjacent tracks are also traced and image quality deteriorates due to adjacent track disturbances such as edges and crosstalk.

Further, tracking may be adjusted by employing a movable head that can be displaced in the width direction of the recording track. Even in this case, 1 minute from the start to the end of tracing the recording track.
Within the field period, the head is fixed at a predetermined position in the track width direction, and near the trace start and end positions, the head does not reliably on-track, and the head is constantly movable in order to obtain the maximum envelope. There is also a problem in that jitter and crosstalk become even worse when the distance is displaced.

(Problems to be Solved by the Invention) As described above, in the conventional magnetic recording/reproducing device described above, since the head width is increased in consideration of the curvature of the track pattern, the image quality deteriorates due to interference with adjacent tracks. There was a problem with this.

The present invention has been made in view of such problems, and includes:
It is an object of the present invention to provide a magnetic recording/reproducing device that can reliably on-track by learning the curvature of a recording track pattern and tracing the recording track according to the curvature of the recording track pattern during reproduction.

[Structure of the Invention] (Means for Solving the Problems) A magnetic recording and reproducing device according to the present invention includes a video head attached thereto, and a piezoelectric device that displaces the video head in a direction perpendicular to a track pattern based on a drive signal. an envelope detection circuit for detecting an envelope of the playback output of the video head, a reference sawtooth wave generation circuit for generating a sawtooth wave corresponding to the playback mode, and a detection circuit for detecting the envelope of the playback output of the video head, a reference sawtooth wave generation circuit for generating a sawtooth wave corresponding to the playback mode, and a detection circuit for detecting the envelope of the playback output of the video head, and a reference sawtooth wave generation circuit for generating a sawtooth wave corresponding to the playback mode; A tracking shift is performed by changing the phase, and the amount of displacement of the video head at which the envelope is maximized is determined at a predetermined sampling point of the track pattern from the output of the envelope detection circuit, and a pattern output based on this amount of displacement is output. track pattern correction means; a pattern learning storage circuit for storing the pattern output obtained by the track pattern correction means; and the driving based on the pattern output stored by the pattern learning storage circuit and the output of the reference sawtooth wave generation circuit. When the output of the piezoelectric element drive circuit that creates a signal and supplies it to the piezoelectric element and the envelope detection circuit decreases below a predetermined threshold, the search mode is designated again and the track pattern correction means is sent to the pattern learning storage circuit. and control means for retaking the pattern output of and updating the memory.

(Function) In the present invention, when the search mode is specified, the track pattern correction means calculates the amount of displacement of the track pattern to obtain a mosquito-sized envelope by performing tracking shift, and outputs a pattern output based on this amount of displacement. do.

A pattern learning storage circuit stores this pattern output.

The piezoelectric element drive circuit drives the piezoelectric element based on the pattern output stored by the pattern learning and storage circuit to displace the video head in the direction perpendicular to the track pattern (width direction). When the output of the envelope detection circuit becomes smaller than a predetermined threshold, the control means again specifies the search mode and causes the pattern learning and storage circuit to store the pattern output that provides the maximum envelope. This allows constant on-tracking regardless of the curvature of the track pattern.

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings. FIG. 1 is a block diagram showing an embodiment of a magnetic recording/reproducing apparatus according to the present invention.

The rotation of the capstan motor 1 is transmitted to the capstan 2, and the rotation of the capstan 2 causes the magnetic tape 4 to run between it and the pinch roller 3.

The rotation of the capstan motor 1 is detected by a rotation detection circuit 5. The rotation detection circuit 5 also detects the rotation of the rotation cylinder 6 and outputs a detection pulse to the reference sawtooth wave generation circuit 7. The reference sawtooth wave generating circuit 7 generates a reference sawtooth wave having a period based on the detection pulse and outputs it to the mix amplifier 8. That is, the rotation detection circuit 5 counts how many rotation pulses (FG pulses) are generated from the capstan 2 during the rotation period of the rotation cylinder 6, and calculates the number of rotation pulses (FG pulses) generated from the capstan 2.
Determine the playback tape speed (playback mode) of the The reference sawtooth wave generating circuit 7 generates a sawtooth wave signal according to the playback mode, and does not generate a sawtooth wave during normal playback at the same tape speed as during recording. When the tape speed is twice that during recording, a sawtooth wave is generated that sequentially displaces the tape from the start of the trace and displaces it by one track pitch at the end of the trace. In the case of n-times speed playback (n-1)) a sawtooth wave that displaces the rack pitch is generated. In addition, in the case of slow playback, at 1/n tape speed, the direction is opposite to that at n times speed (
n-1) Displacement equal to J ~ rack pitch.

A piezoelectric element 9 with one end fixed is attached to the rotating cylinder 6, and a video head 10 is attached to the other end of the piezoelectric element 9.
is installed. The state of the piezoelectric element 9 changes based on a drive signal, thereby making it possible to displace the video head 10 in a direction perpendicular to the track pattern.

The playback output from the video head 10 is given to an envelope detection circuit 11. The envelope detection circuit 11 performs envelope detection on the playback output of the video head 10 and outputs the detected signal to the envelope maximum value calculation circuit 12 .

When a search mode is specified by a control device (not shown), the envelope maximum value calculation circuit 12 outputs a pattern output for changing the phase of the video head and the track pattern (tracking shift) to the addition circuit 14, and Find the maximum value of the envelope at predetermined n sampling points of the track pattern,
The pattern output at this time is output to the pattern learning storage circuit 13.

The pattern learning storage circuit FI 613 stores the pattern output from the envelope maximum value calculation circuit 12. The pattern learning storage circuit 13 outputs the stored pattern output for each sampling point to the addition circuit 14. The update signal generation circuit 18 compares the envelope value (maximum envelope value) at the time of on-track with the envelope value of each sampling point currently being traced, and determines that m (m<n) of the sampling points are below a predetermined threshold. If the value also decreases, an update signal is output to the pattern learning storage circuit 13. When the pattern learning memory circuit 13 receives the update signal, the envelope maximum value calculation circuit 1
The pattern output from 2 is taken in and the stored pattern output is updated.

Note that, upon generation of the update signal, the control device (not shown) specifies the search mode again.

The adder circuit 14 provides the output of the envelope maximum value calculation circuit 12 to the track pattern correction circuit 15 in the search mode, and provides the output of the pattern learning storage circuit 13 to the track pattern correction circuit 15 in the playback mode using dynamic tracking that displaces the head. . The track pattern correction circuit 15 determines the optimal displacement direction and displacement amount of the video head for obtaining the maximum envelope from the output of the addition circuit 14, and outputs a track pattern correction output to the mix amplifier 8. The mix amplifier 8 adds and amplifies the reference sawtooth wave and the track pattern correction output, and outputs the result to the piezoelectric element drive circuit 16. The piezoelectric element drive circuit 16 provides a drive signal based on the output of the mix amplifier 8 to the piezoelectric element 9 via the slip ring 17. As described above, this drive signal changes the state of the piezoelectric element 9, causing the video head 10 provided at the tip to be displaced. Note that piezoelectric element drive circuit 1
6 is a control device (not shown) that stops driving the piezoelectric element 9 when a search mode is specified at the start of playback, and a playback mode using dynamic tracking that displaces the head, and when a search mode is specified again. , and output a drive signal to the piezoelectric element 9.

Next, the operation of the magnetic recording/reproducing apparatus configured as described above will be explained with reference to the explanatory diagram of FIG. 2. Figure 2 (a
) to (f) show the relationship between the recording track pattern and the head trace, and FIGS. 2(a') to (f') show the envelopes in FIGS. 2(a) to (f), respectively. Note that in FIG. 2, upward arrows indicate sampling points.

Assume that a magnetic tape recorded by another VTR is to be played back. A control device (not shown) specifies a search mode, first stops the operation of the piezoelectric element drive circuit 16, and performs reproduction for one field period with the video head 10 fixed. As shown by the solid line in FIG. 2(a), the track pattern 20 is curved due to variations in mechanical precision and adjustment errors in the tape running system. The magnetic tape 4 travels due to the rotation of the capstan motor 1, and the rotary cylinder 6 rotates, so that the video head 10 traces approximately in a straight line as shown by the broken line in FIG. 2(a).

Next, the control device performs tracking shift as shown in FIGS. 2(b) and 2(c). In this way, the trace position where the envelope 1 of the playback output from the video head 10 is maximum is determined. That is, the envelope detection circuit 11 performs envelope detection on the playback output from the video head 10 and sends the detected output to the envelope maximum value calculation circuit 12.
Output to. The envelope maximum value calculation circuit 12 calculates the maximum value of the envelope detection level at a predetermined sampling point. In the state shown in Fig. 2(b), the second
As shown in Figure (b'), the maximum envelope is obtained at the center of one field period. Also, Figure 2 (C)
In the state shown in FIG. 2 (C'), the maximum envelope is obtained near the start and end of one field period. The envelope maximum value calculation circuit 12 calculates the amount of track displacement (the amount of track bending) at which the maximum value of the envelope is obtained at each sampling point, and corrects the track pattern by adding the track pattern output indicating this amount of track displacement via the adding circuit 14. Output to circuit 15.

The track pattern correction circuit 15 outputs a track pattern correction output for displacing the video head 10 so that the envelope of the reproduction output of the video head 10 is maximized based on the output of the envelope maximum value calculation circuit 12. This track pattern correction output is given to the piezoelectric element drive circuit 16 via the mix amplifier 8. The piezoelectric element drive circuit 16 provides a drive signal to the piezoelectric element 9,
Video head 1 is moved so as to trace approximately on track 20.
Displace 0.

In this way, as shown in FIG. 2(d), the video head 1
0 traces the recorded track pattern 20 while being displaced approximately in accordance with the curvature of the track.

On the other hand, the output of the envelope maximum value calculation circuit 12 at this time is also given to the pattern learning storage circuit 13. The pattern learning/memory circuit 13 stores the amount of displacement of track patterns recorded on other VTRs for each sampling point. Thereafter, the output of the pattern learning storage circuit 13 is applied to the track pattern correction circuit 15 via the addition circuit 14. The track pattern correction circuit 15 outputs a track pattern correction output based on the output of the pattern learning storage circuit 13 to the mix amplifier 8. As a result, the piezoelectric element 9 is displaced, and tracing following the curve of the recording track 20 is performed.

Here, it is assumed that tracking failure occurs again.

In this case, since the trace pattern of the head 10 is fixed by the output of the pattern learning and storage circuit 13, the recording track pattern 2 is fixed as shown in FIG. 2(e).
The head trace (wavy line) deviates from 0 (solid line). In this case, the output of the envelope detection circuit 11 decreases as shown in FIG. 2(e'). The update signal generation circuit 18 compares the output of the envelope detection circuit 11 with the threshold shown in FIG. 2(d'), and when the output of the envelope detection circuit 11 becomes smaller than the threshold at m sampling points, the update signal is generated. is output to the pattern learning storage circuit 13. As a result, the control device (not shown) designates the search mode again, and performs the tracking shift while maintaining the trace pattern of the head 10. The envelope maximum value calculation circuit 12 calculates the pattern displacement amount for obtaining the maximum envelope again, and outputs a pattern output. The pattern learning storage circuit 13 takes in the pattern output from the envelope maximum value calculation circuit 12 according to the update signal and updates the record. Piezoelectric element 9
is displaced based on the pattern output from the pattern learning/memory circuit 13, and traces approximately on the recording track 20, as shown in FIG. 2(f).

In this way, in this embodiment, the pattern output that provides the maximum envelope is stored in the pattern learning/memory circuit 13, and by displacing the head using this pattern output, even if the recording track is curved, it can be reliably recorded. This makes it possible to stay on track. Therefore, even when reproducing a magnetic tape recorded on another VTR, reliable on-track is possible, and the head width can be made relatively small. Therefore, it is possible to prevent adjacent track disturbances such as edge and crosstalk from occurring. Further, after on-tracking, the trace pattern of the video head is fixed based on the pattern output stored by the pattern learning/memory circuit 13, so that adverse effects on the screen such as jitter and screen shaking can be prevented. Furthermore, even if tracking becomes defective again, the search mode is performed without changing the trace pattern of the video head, and on-tracking can be achieved in a short time.

[Effects of the Invention] As explained above, according to the present invention, the curvature of the recording track pattern is learned and the recording track is traced according to the curvature of the track pattern during playback, so that regardless of the curvature of the recording track, the recording track can be reliably traced. This has the advantage that it is possible to stay on track.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a magnetic recording/reproducing apparatus according to the present invention, and FIG. 2 is an explanatory diagram for explaining the operation of the embodiment. 7. Reference sawtooth wave generation circuit, 8. Mix amplifier, 9. Piezoelectric element, 10. Video head, 11. Envelope detection circuit, 12..
Envelope maximum value calculation circuit, 13... Pattern learning storage circuit, 15... Track pattern correction circuit, 16... Piezoelectric element drive circuit, 18... Update signal creation circuit.

Claims (1)

[Claims] A piezoelectric element to which a video head is attached, which displaces the video head in a direction perpendicular to a track pattern based on a drive signal, and an envelope detection circuit which detects an envelope of a playback output of the video head. , a reference sawtooth wave generation circuit that generates a sawtooth wave corresponding to a playback mode, and a tracking shift that changes the phase between the video head and the track pattern in the search mode to detect the track from the output of the envelope detection circuit. track pattern correction means for determining the amount of displacement of the video head that maximizes the envelope at a predetermined sampling point of the pattern and outputting a pattern output based on the amount of displacement; and pattern learning for storing the pattern output obtained by the track pattern correction means. a piezoelectric element drive circuit that creates the drive signal and supplies it to the piezoelectric element based on the pattern output stored by the pattern learning memory circuit and the output of the reference sawtooth wave generation circuit; and the envelope detection circuit. control means for designating the search mode again when the output of the track pattern correction means falls below a predetermined threshold value, and for causing the pattern learning and storage circuit to retake the pattern output from the track pattern correction means to update the memory. magnetic recording and reproducing device.