JPH0262881B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention includes a plurality of magnetic heads mounted on a rotating body, a magnetic tape tilted at a predetermined angle and run along the rotation locus of the magnetic heads, and The present invention relates to a rotating head type magnetic recording and reproducing apparatus that sequentially records and reproduces signals as a recording locus inclined with respect to the longitudinal direction of the magnetic tape using a head.

Conventional Structures and Problems There is a video tape recorder (VTR) as a typical rotating head type magnetic recording/reproducing device.

In recent years, there has been a remarkable increase in the recording density of VTRs due to improvements in magnetic tapes or the adoption of magnetic tapes using new recording media. In particular, the recording track pitch is already approximately 20 μm in the VHS 6-hour recording mode, but if alloy tape or vapor-deposited tape is adopted as a new recording medium in the future, a recording track pitch of several μm will be sufficient for image quality. is expected to be obtained. Now, when the track pitch becomes narrow like this, the problem is how to make the playback head follow the recording track correctly during playback, and also how to make the playback head follow the recording track correctly when recording with multiple recording heads. The problem is how to keep the recording track widths equal (in other words, how to keep the gap height positions of a plurality of recording heads (hereinafter referred to as recording head heights) equal). In particular, the importance of keeping the heights of the recording heads equal is important for the following reasons.

(1) For example, a 2-head helical scan VTR
When recording without the guard between tracks in azimuth recording, change the track pitch.
If the relative height of the heads is 10 μm, and the relative height of the heads deviates by 3 μm, the track width on one side will be 13 μm and the other track width will be 7 μm, resulting in a large difference in recording track width. It is desirable to keep the relative height difference between the two heads to about 10% or less, but in this case, the relative height difference needs to be 1 μm or less, and the track pitch must be
When it is about 5 μm, it is necessary to keep the relative height difference between the two heads to about 0.5 μm or less, but it is extremely difficult to achieve such precision mechanically.

(2) In addition to the importance of relative height, the accuracy of absolute height is also important. For example, in a 2-head helical scan VTR, the track pitch is 5 μm.
If the installation height of the rotary head deviates by 5 μm from the tape travel restriction position, the relative position between the fixed head and the audio signal recording position will change by a time equivalent to one field of the video signal. A time lag may occur, resulting in a timing lag between video and audio when exchanging tapes with other decks. Although this problem can be corrected initially using a standard tape, the problem cannot be prevented if the mounting height of the rotary head changes over time. The head height temporarily decreased to 20μ due to changes over time.
If the tape is misaligned by m, there will be a timing difference of two frames between the audio signal recorded by the fixed head and the video when the tape is interchanged with another deck, resulting in an inconvenient situation where the video and sound will be played back out of sync. .

In addition, 8mm video, for which standardization work is currently underway, is configured to convert the audio signal into a PCM signal, compress the time axis, and record it as an extension of the video signal recording track. The accuracy of the center L value (the length from the center of the video signal recording track to the tape edge) is approximately ±
The absolute height accuracy of the head height, including changes over time, must be within ±40 μm.

Now, there is a method for electrically automatically adjusting the first relative height, which is adopted in the V-2000 system developed by both Philips and Grundeitz. This method is very effective as a means of automatically adjusting the curvature of the recording track to match the curvature of the recorded track during playback. In a tracking system (hereinafter referred to as DTF), it is difficult to maintain stable absolute height accuracy of the rotating head. This is because, in the above method, the magnetic heads mounted on a movable piezoelectric plate are each attached to a rotating cylinder at 180° positions, and one of the heads is fixed with the piezoelectric drive voltage set to zero during recording. and the piezoelectric driving voltage of the latter magnetic head is controlled so that the height of the other magnetic head matches the height of the former magnetic head, so that the relative heights of the two magnetic heads match. controlled as follows. However, piezoelectric elements that are fixed with a driving voltage of zero during recording are subject to deviations due to changes in the environment such as time and temperature and humidity, even when the driving voltage is zero. The height of the mounted magnetic head will also change, and the height of the fixed head cannot be guaranteed.

Purpose of the Invention The present invention develops the above method to provide a device that automatically controls the relative height of two recording heads, guarantees the absolute height, and performs track-to-track playback (DTF) during playback. This is what we provide.

Structure of the Invention In order to record by automatically controlling the relative and absolute heights of a plurality of rotating magnetic heads during recording, one magnetic head is fixedly attached to a rotating cylinder and other recording heads are fixedly attached to the rotating cylinder. The head is attached to a rotating cylinder via a movable plate, and the height of the head attached via the movable plate is controlled by a signal obtained by measuring the difference in height from the recording head. The purpose is to prevent the head from performing tracking.

DESCRIPTION OF EMBODIMENTS FIG. 1 shows a specific example of the structure of a magnetic head attached to a rotating cylinder (or rotating drum or rotating head bar) in the present invention.

In FIG. 1, four magnetic heads A, B, A', and B' are arranged on a rotating cylinder 1.
The head A is fixed to the cylinder 1 via a fixed head base 3. The heads A' and B are mounted on a movable plate 4 made of, for example, a piezoelectric element, and are attached to the cylinder 1 using 6 as a fulcrum. Head B' is similarly attached to the cylinder via movable plate 5 with 7 as a fulcrum. and head A
and B, and A' and B' are mounted at 180 degrees from each other. 2 is the rotation axis of the rotating cylinder.

Now, when recording, two heads, A and B, are used to record, and the height of the B head is controlled to match the height of the A head, using the height of the A head as a reference. The control method will be described later), the second
A diagonal recording trajectory is sequentially formed on the tape as shown in the figure. A and B in FIG. 2 indicate tracks recorded by the A head and B head, and V _H and V _t indicate the scanning direction of the rotary head and the running direction of the tape, respectively. By doing this, the relative and absolute heights of the two recording heads A and B can be matched, and the recording track widths of the A and B tracks in FIG. 2 can be kept equal. Become.

When playing, use magnetic heads A' and B' to play.
Since both are mounted on a movable plate, it is possible to follow the curvature of the recording track for reproduction. Although the method of following the curvature of the recording track during playback is not directly related to the gist of the present invention, it is the method adopted in the V-2000 system described above, that is, the method of following the curvature of the recording track during recording, that is, a pilot signal for detecting track deviation is sent to each recording track during recording. A method has already been put into practical use in which the recording track is recorded and the track deviation is detected from the reproduced pilot signal to control the height of the piezoelectric element movable plate to follow the curve of the recording track.

Also, when performing so-called azimuth recording where the gap angles of the two recording heads A and B are different,
It is desirable that a head with the same azimuth as recording head A be placed at position A', and a head with the same azimuth as recording head B at position B'. With this configuration, mutually adjacent heads A, B' and B can be
Each of A' is a reverse azimuth head, and crosstalk during reproduction between adjacent heads is reduced (because adjacent heads normally reproduce the same track, the reproduction output level of adjacent heads deteriorates due to azimuth loss). In addition, by configuring this way, when playing still images (still playback), it is possible to
A field still image can be obtained by reproducing using the head of B', and two tracks with different azimuths can be reproduced as in the case of still reproducing using B' and A', which have different azimuths. This eliminates the problem of frame still images, and allows you to obtain stable still images without blur, even for moving images. Although B and B′ are not in a 180° positional relationship,
Stable still images can be reproduced by setting the gap distance between B and B' on the order of several hundred microns according to the recording format determined by the cylinder diameter, tape speed, tape width, etc. . At present, heads with a gap of several hundred microns between the two heads are already in practical use in VHS and VTR. The two heads A and B' are also set to have the same gap distance as the two heads A' and B. If it is desired to widen the gap between two adjacent heads, it is possible to maintain image stability by using a delay line to delay the reproduction signal of one head during special reproduction such as still reproduction. For example, during normal playback, heads A'B' are used, and during still playback, heads B' and B are used to delay the B head playback signal using a delay line, thereby reducing skew distortion and vertical screen wobble. can be eliminated.

Now, the method of automatic height adjustment of the recording head mentioned above will be described. In Fig. 3, A head,
Recorded track A ₁ B ₁ recorded by head B,
When A ₂ ... is formed sequentially, a low frequency pilot signal (for example, about 200 KHz) is recorded during the instantaneous period of W ₁ , W ₂ W ₃ (a period about one horizontal scanning period of a television signal), and its Immediately after, instantaneous reproduction periods R ₁ , R ₂ , and R ₃ are provided, and between adjacent tracks, the pilot recording period W ₁ of the previous recording track and the instantaneous reproduction period R ₂ of the subsequent recording track are aligned in the track width direction. It is formed. And W
The section R section is set, for example, to correspond to the vertical blanking period of the television signal.

With this configuration, the pilot recorded at the timing shown in FIG. 4a reproduces the recording pilot signal of the previous recording track as crosstalk (leakage magnetic field) at the timing b. That is,
The pilot signal of W ₁ recorded on A ₁ track is
It is played back as crosstalk in instantaneous playback section _R2 when recording B1 track, and then _the pilot signal of _W2 recorded on track _B1 is played back as crosstalk in instantaneous playback section _R3 when recording _A2 track. , a signal as shown in FIG. 4b is obtained. Figure 4b
In the reproduction signal, instantaneous reproduction signals from the A head and B head appear alternately, but the height of one head B (Fig. 1) is adjusted so that the reproduction pilot signals from the A head and B head that appear alternately are equal. By controlling the height, the heights of both heads can be matched. In this case, since A head is fixed, A
As long as the head is installed accurately, the absolute height will be automatically guaranteed.

Figure 5 shows another configuration example, and 1' to 7' are 1 to 7 in Figure 1.
7 respectively. The A head and B head are mounted at 180° positions. in this case,
During normal playback, if the azimuths of the A head and B' head are different, playback that follows the curvature of the recording track cannot be performed, but during special playback, various special playbacks can be achieved using the B head and B' head. be able to. Also, A head, B head,
When both B' heads have the same gap angle, both normal reproduction and special reproduction are possible using the B and B' heads. However, in this case, B and B' are not arranged at 180 degrees, so for example, B
It is necessary to delay the head reproduction signal using a delay line to match the timing.

In addition, in Figure 5, if head A', which has the same azimuth as head A, is placed at position B', then head A' and head B can be used to perform tracking that follows the curvature of the recorded track, allowing normal playback. , special playback can be performed. However, in this case as well, since the B head and the A' head are not arranged at 180 degrees, it is necessary to match the timing by, for example, delaying the reproduction signal of the A' head with a delay line.

Effects of the Invention According to the present invention, by using one fixed head and a plurality of heads mounted on two movable plates, the heights of two recording heads can be adjusted in terms of relative height and absolute height. Both can be controlled, and during playback, DTF operation that can follow the curvature of the recording track can be performed, and the head height can be adjusted electrically and automatically without mechanical precision. It can be well controlled.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing the arrangement of heads mounted on a rotating head cylinder used in a helical scan VTR according to an embodiment of the present invention, and FIG. 2 is a helical scan VTR.
FIG. 3 is a plan view schematically showing a recording track on a magnetic tape in a VTR. FIG. 4 is a diagram showing the recording pilot and reproducing pilot in the recording track pattern of FIG. 3, and FIG. 5 is a diagram showing the arrangement of the heads mounted on the rotary head cylinder in another embodiment of the present invention. FIG. 1... Rotating cylinder, 2... Rotating shaft, 3... Fixed head base, 4, 5... Movable plate composed of piezoelectric elements, etc., A, B, A', B'... Magnetic head.

Claims (1)

[Scope of Claims] 1. A first magnetic head fixedly placed on a rotating body, and a height position that is adjusted by an electric signal to be located at a rotational angle of 180 degrees with respect to the first magnetic head. a second magnetic head attached to the rotating body via a controllable first movable plate; and a second magnetic head located close to the first magnetic head whose height position can be controlled by an electric signal. At the time of recording, the third magnetic head is attached to the rotating body via a movable plate. A signal is sequentially recorded on the magnetic tape as a recording locus in the longitudinal direction of the magnetic tape by the first magnetic head and the second magnetic head. 1. A rotary head type magnetic recording and reproducing apparatus characterized in that a reproduction signal is obtained using one of the three magnetic heads. 2 The gap azimuth of the first magnetic head and the third
The gap azimuths of the magnetic heads are equal and the second
2. The rotary head type magnetic recording/reproducing apparatus according to claim 1, wherein the gap azimuth of the first magnetic head is different from the gap azimuth of the first and third magnetic heads. 3 The gap azimuth of the second magnetic head and the third
The gap azimuths of the magnetic heads are equal and the first
2. A rotary head type magnetic recording/reproducing apparatus according to claim 1, wherein the gap azimuth of the first magnetic head is different from the gap azimuth of the second and third magnetic heads. 4. A first magnetic head fixedly mounted on a rotating body, and a first magnetic head whose height position can be controlled by an electric signal so as to be located at a rotational angle of 180 degrees with respect to the first magnetic head. A second magnetic head is attached to the rotating body via a movable plate, and a second magnetic head, which is located close to the first magnetic head and whose height position can be controlled by an electric signal, is attached to the rotating body via a second movable plate. It has at least a third magnetic head attached to the rotating body, and a fourth magnetic head close to the second magnetic head and attached on the second movable plate, When recording on a magnetic tape running at a predetermined angle along the magnetic tape, the first and second magnetic heads sequentially record signals on the magnetic tape as a recording trajectory inclined with respect to the longitudinal direction of the magnetic tape. . A rotation characterized in that during reproduction, the third magnetic head and the fourth magnetic head or the third magnetic head and the second magnetic head are used to obtain a reproduced signal. Head type magnetic recording/reproducing device. 5 The gap azimuths of the first magnetic head and the third magnetic head are equal, and the gap azimuths of the second magnetic head and the fourth magnetic head are equal,
5. The rotary head type magnetic recording/reproducing apparatus according to claim 4, wherein the first magnetic head and the second magnetic head have different gap azimuths. 6. The third and fourth magnetic heads are used during normal playback at the same running speed as the tape running speed during recording, and the third and second magnetic heads are used during still image playback when tape running is stopped. A rotary head type magnetic recording and reproducing apparatus according to claim 5, characterized in that: