JPH04133585A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To prevent the occurrence of picture quality deterioration caused by disturbance, etc., from adjacent tracks at the time of reproduction by finding the optimum tracing position of the 1st video head in a recording mode. CONSTITUTION:The reproduced output of a video head is supplied to an envelope detection circuit 13 and the optimum tracing position at which the maximum envelope value is obtained is discriminated by envelope detection. As a result, a drive signal is supplied to a piezo-electric element 9 from a piezo-electric element drive circuit 19 and a video head 11a is displaced to the optimum tracing position. Since a video head 11b for recording is provided with a level difference of one-track pitch against video heads 11a and 11b for reproduction only, the head 11b does not overwrite in a preceding video track and recording is performed without forming any unnecessary guard band.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a magnetic recording/reproducing apparatus, and particularly to a magnetic recording/reproducing apparatus that enables dynamic tracking control during recording.

(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 reproduction control pulse from the control head 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 the monostable multivibrator and then given to the phase comparator, and the user can adjust the time constant of the monostable multivibrator to
Tracking adjustments are being made. 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 ensure reliable tracing on the track. However, because the head width is large, during recording, the next track is overwritten on a part of the previous track, and during playback, adjacent tracks are also traced, resulting in problems such as edge and crosstalk. The image quality deteriorates due to interference from adjacent tracks.

In addition, in conventional magnetic recording and reproducing devices that employ a video head that can be moved by a piezoelectric element or the like, envelope detection is performed on the reproduction output of the recording track, and the piezoelectric element is driven based on the detected output. The absolute position of the video head during playback is determined to enable optimal tracing according to the recording track pattern. However, even in this case, the video head is fixed at a predetermined position on the rotating cylinder during recording. That is, it is impossible to control the video head during recording, and it is necessary to increase the width of the head in order to reliably trace the track, resulting in problems such as overwriting and guard bands.

(Problem to be Solved by the Invention) As described above, in the conventional magnetic recording/reproducing device described above, it is necessary to increase the head width in order to reliably trace the track, and overwriting occurs during recording. However, there was a problem in that the image quality deteriorated due to interference with adjacent tracks during playback.

The present invention has been made in view of such problems, and includes:
By making it possible to detect the absolute position of the video head during recording and playback, recording tracks can be formed without overwriting or guard bands.
It is an object of the present invention to provide a magnetic recording and reproducing device that can prevent image quality deterioration due to interference with adjacent tracks during reproduction.

[Structure of the Invention] (Means for Solving the Problems) A magnetic recording and reproducing device according to the present invention includes a piezoelectric element that is displaced perpendicularly to a track pattern based on a drive signal, and a piezoelectric element that has a width of one track pitch. first and second video heads that are formed to have the same width and have a step of one track pitch width and that are attached to the piezoelectric element back and forth in the track pattern advancing direction; and these first and second video heads. an envelope detection circuit that detects the envelope of the playback output of the playback output; a reference sawtooth wave generation circuit that generates a sawtooth wave corresponding to the playback mode; and a reference sawtooth wave generation circuit that generates a sawtooth wave corresponding to the playback mode; Tracking that outputs a pattern output based on the displacement direction and displacement amount of the first video head corresponding to a track pattern in a recording mode by determining the displacement direction and displacement amount of the first video head in which the envelope increases. and a piezoelectric element drive circuit that creates the drive signal based on the output of the tracking correction means and the output of the reference sawtooth wave generation circuit and supplies it to the piezoelectric element in a recording mode. .

(Function) In the present invention, the first head is used as a read-only head. Even in the recording mode, the reproduction output of the first head is applied to the envelope detection circuit and subjected to envelope detection. The tracking correction means provides a pattern output from the output of the envelope detection circuit to the piezoelectric element drive circuit for displacing the first video head according to the track pattern. Thereby, the piezoelectric element drive circuit outputs a drive signal to the piezoelectric element to displace the first head according to the track pattern. The second head has a step difference of one track pitch width from the first head and is provided one behind the other in the track pattern advancing direction, and when the first head is displaced according to the track pattern, the second head Recording is performed using a fixed track pattern using the head.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. 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 enlarged perspective view showing a piezoelectric element and a video head in FIG. 1.

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). 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 where the tape speed is the same as that during recording. In the case of tape speed, a sawtooth wave is generated that is sequentially displaced from the start of the trace and displaced by one track pitch at the end of the trace. In the case of n-times speed playback (n-1)) a sawtooth wave is generated to displace the rack pitch. In the case of slow playback, at a tape speed of 1/n, the displacement is (n-1) track pitches in the opposite direction to that at n times the speed.

A piezoelectric element 9 whose one end is fixed and a piezoelectric element 10 (not shown) are attached to the rotating cylinder 6.
At the other end, there are video heads 11a and 11b (hereinafter referred to as below) that trace the I-rack of the odd field.

A head (also referred to as A head 11) is attached. Further, at the other end of the piezoelectric element 10, there is a video head 12a (not shown) for tracing even field tracks.

12b (hereinafter also referred to as B head 12) is attached. The states of the piezoelectric elements 9 and 10 change based on the drive signal, so that the A head 11 and the B head 12 can be displaced perpendicularly to the track pattern. Reproduction outputs from the A head 11 and the B head 12 are given to an envelope detection circuit 13.

The envelope detection circuit 13 performs envelope detection on the reproduced outputs of the A head 11 and the B head 12 and outputs the result to the envelope maximum value calculation circuit 14 . The envelope maximum value calculation circuit 14 calculates the maximum value of the envelope at a predetermined sampling point and outputs it to the addition circuit 15.

As shown in FIG. 2, the piezoelectric element 9 is provided on a helad base 21. As shown in FIG. As described above, the piezoelectric element 9 is driven based on the drive signal, and its tip side moves in a direction away from or close to the head base 21, that is, in a direction perpendicular to the track pattern. At the tip of the piezoelectric element 9, there are two video heads 11a and llb arranged in front and back in a direction perpendicular to the movable direction of the piezoelectric element 9, that is, in the tracing direction.
(A head 11) is attached at the video head attachment portion 22.23. Further, the video head mounting portions 22 and 23 at the tip of the piezoelectric element 9 have a step difference between them, and the video heads 11a and 11b are attached with a step difference that is the same as the track pitch width. That is, the front video head 11a (read-only head) in the tracing direction can trace the previous track, while the rear video head 11b can trace the next track. Note that the video head 11a
, 11b are formed to have the same track width as the recording track width of the magnetic tape 4. In addition, the video head 11a
, 11b are formed with mutually different azimuth angles.

Therefore, adjacent track interference is reduced.

Note that a piezoelectric element 10 and a video terminal 12 (not shown)
The configurations of a and 12b (B head 12) are also similar to those shown in FIG.
The rear video head 12b can trace the next track at the same time as the head 2a (playback-only head) traces the previous track. Also, the track width of the video heads 12a and 12b is the same as that of the magnetic tape 4.
The width of the recording track is the same as that of the recording track. Note that the video heads 12a and 12b are the video heads 11b and I, respectively.
It is formed with the same azimuth angle as la.

On the other hand, the reproduced outputs from these A head 11 and B head 12 are also given to a video 1 field storage RAM 16 and a video signal comparison circuit 17. Video 1 field memory R
The AM 16 stores, for example, one field of the reproduction output of the video head Ila and outputs it to the video signal comparison circuit 17. The video signal comparison circuit 17 is also supplied with the playback output of the video head 11b, and by comparing the playback outputs before and after one field, it is possible to determine whether the video is a previously recorded video or a video recorded immediately before. Head 11b, 1
2b). 1
If the reproduction outputs before and after the field substantially match, it is determined that the video recorded immediately before has been reproduced, and the video signal comparison circuit 17 does not output a correction output to the addition circuit 15.
Furthermore, if the playback outputs before and after one field do not match, it is determined that the previously recorded video has been played back, and the video signal comparison circuit 11 outputs a correction output to change the trace track. is output to the adder circuit 15.

The adder circuit 15 adds the output of the envelope maximum value calculation circuit 14 and the output of the video signal comparison circuit 17 and provides the result to the tracking correction circuit 18 . The tracking correction circuit 18 outputs the A head 11 and the B head 1 from the output of the addition circuit 15.
The optimal displacement direction and amount of displacement of 2 are determined, and a track pattern correction output is 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 outputs a drive signal based on the output of the mix amplifier 8. As mentioned above, this drive signal changes the state of the piezoelectric element 9.10, and the video heads 11a11b, 11a11b,
12a and 12b are adapted to be displaced.

Next, the operation of the magnetic recording/reproducing apparatus configured as described above will be explained with reference to FIGS. 3 and 4. FIG. 3 is an explanatory diagram showing the track pattern of the magnetic tape 4,
FIG. 4 is an explanatory diagram showing a portion A in FIG. 3 in an enlarged manner.

The rotation of the capstan motor 1 causes the magnetic tape 4 to run, and the rotating cylinder 6 rotates, thereby
As shown in FIG. 3, the video head 11a, '11
Video track 3 by b, 12a, 12b
0 is traced. At the time when the reproduction mode is started, the A head 11 and the B head 12 trace in a substantially linear pattern. The piezoelectric element drive circuit 16 includes piezoelectric elements 9,
By changing the state of 10, the A head 11 and the B head 1
2 is vibrated perpendicular to the track pattern. In this way, the optimal trace position where the envelope of the reproduction output from the A head 11 and the B head 12 becomes maximum is determined.

That is, the envelope detection circuit 13
The reproduced output from the B head 12 is envelope-detected, and the detected output is output to the envelope maximum value calculation circuit 14. The envelope 1 maximum value calculation circuit 14 calculates the maximum value of the envelope detection level at a predetermined sampling point. The tracking correction circuit 18 adjusts the A head 11 based on the output of the envelope maximum value calculation circuit 14.
And outputs a track pattern correction output for displacing the A head 11 and the B head 12 so that the envelope of the reproduced output of the B head 12 is maximized. This track pattern correction output is given to the piezoelectric element drive circuit 16 via the mix amplifier 8. Piezoelectric element drive circuit 1
6 applies a drive signal to the piezoelectric elements 9 and 10, and drives the A head 11 and B head so as to trace substantially on the video track 30.
The head 12 is displaced.

In this embodiment, even when a recording mode is specified, playback output is output from the playback-only video heads 11a and 12a. That is, as shown in Figure 4,
Immediately after the video head 12a reproduces the track 31 in a predetermined n field, the video head 12b traces and records the next track 32. Next (n+1
> In the field, the video head 11a having the same azimuth as the video head 12b traces and reproduces the recording track 32, and then the video head 11
The playback output from the video heads 11a and 12a, in which recording is performed by tracing the next track 33, is given to the envelope detection circuit 13, and as in the case of recording, the optimum trace position where the maximum envelope can be obtained is determined by envelope detection. be judged. In this way, the piezoelectric element drive circuit 19
A driving signal is applied to the piezoelectric elements 9 and 10, and the video heads 11a and 12a are displaced to the optimum tracing position. As a result, the recording video heads 11b and 12
The video heads 11b and 12b for recording are also displaced to the optimum tracing position and sequentially records in the same track pattern as the previous track, and the video head 11a is for reproduction only.
, 11b are formed with a level difference of one track pitch, so that recording is performed without overwriting the previous video track and without forming unnecessary guard bands.

Note that the playback output before and after one field obtained by tracing the previous and subsequent video tracks 30 is the video signal comparison circuit 1.
7, and the video signal comparison circuit 17 determines whether the video was recorded in the past or just before by comparing the playback outputs before and after one field. . If the video has been recorded in the past, a correction output is given to the addition circuit 15 to trace the correct video track.

As described above, in this embodiment, two video heads Ila and 11b each having a step width of one track pitch and a step difference of one track pitch are provided at the tip of the piezoelectric element 9 front and back in the tracing direction, and the piezoelectric element 9 is moved based on the drive signal. By changing the state of , these two video heads lla and 11b are displaced by the same amount. In the recording mode, one of the video heads 11a plays back the previous track, and the video head 11a plays back the previous track so that the envelope of this playback output is maximized.
By displacing , the tracing position of the video head 11b for tracing and recording the next track is determined, and it is possible to always record a constant pattern without overwriting or guard bands. For this reason,
Even during reproduction, interference with adjacent tracks does not occur, and the quality of the reproduced image can be improved.

Furthermore, even when recording is subsequently performed on a magnetic tape recorded with another VTR, it is possible to record in the same video track pattern as the video track pattern used when recording with the other VTR. Therefore, recording and reproduction compatibility is extremely high.

[Effects of the Invention] As explained above, according to the present invention, since the optimum tracing position of the first video head is determined in the recording mode, the trace position of the first video head is determined without overwriting or guard banding. This has the effect that a constant recording track can be formed and image quality deterioration due to interference with adjacent tracks during reproduction can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the magnetic recording/reproducing device according to the present invention, FIG. 2 is a perspective view showing the piezoelectric element and video head in FIGS. 1, and FIG. 3 is a track diagram of the magnetic tape 4. An explanatory diagram showing the pattern, FIG. 4 is an explanatory diagram showing a portion A in FIG. 3 in an enlarged manner. 7... Reference sawtooth wave generation circuit, 9... Piezoelectric element, 11... Video head, 13... Envelope detection circuit, 14... Envelope maximum value calculation circuit, 18... Tracking correction circuit, 19...Piezoelectric element drive circuit. Figure 2

Claims (1)

[Scope of Claims] A piezoelectric element that is displaced in a direction perpendicular to a track pattern based on a drive signal; first and second video heads attached to the piezoelectric element in front and back in the traveling direction; an envelope detection circuit for detecting envelopes of playback outputs of these first and second video heads; a reference sawtooth wave generation circuit that generates a sawtooth wave; and a displacement direction and amount of displacement of the first video head whose envelope increases at a predetermined sampling point of the track pattern from the output of the envelope detection circuit in a recording mode. tracking correction means for outputting a pattern output based on the displacement direction and amount of displacement of the first video head corresponding to a track pattern in a recording mode; and a piezoelectric element drive circuit that creates the drive signal based on the output of the wave generation circuit and supplies the drive signal to the piezoelectric element.