JPH03156718A - Rotary magnetic head device - Google Patents

Abstract

PURPOSE:To reduce impact jitter by improving the symmetricity of head arrangement to cancel impact jitter caused at recording and impact jitter caused at reproduction. CONSTITUTION:Dummy heads 30,31,32,33 whose tip shape and projection are nearly equal to those of other heads are arranged just in the middle between recording exclusive heads 7,8 or 9,10 and between reproduction exclusive heads 3,4 or 5,6 and just in the middle between a high fidelity head 11 or 12 and the reproduction exclusive heads 3,4 or 5,6. Then the heads are arranged at an equal angular interval of 30 deg. in the circumferential direction as a whole. When the dummy heads are used in this way, the selecting range of each head interval is widened and the impact jitter at recording and reproduction is entirely cancelled. Thus, a high picture quality picture with less video jitter is obtained by using other heads than the recording heads for the reproduction.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the arrangement and shape of a rotating magnetic head of a helical scan VTR in which a recording head and a reproducing head are separate heads.

[Conventional technology]

V that allows high-fidelity FM audio recording with conventional home VTRs
The rotating magnetic head (hereinafter simply referred to as head) of the TR is arranged as shown in FIG. 2 in the same figure
is a rotating magnetic head device (hereinafter referred to as cylinder), and heads 17.18 and 19.20 are for recording Nfi (R/
P) double azimuth head, head 17.19
is for EP, and head 18.20 is for SP. head 1
1.12 is a high-fidelity audio recording/reproducing head (hereinafter referred to as a high-fidelity head), and head 152C is a flying erase head.

Each head rotates at a constant speed in the direction of the arrow.

Although not visible in the figure, they are arranged with a predetermined step in the direction of the rotation axis. In such a VTR, there may be a need to provide a read-only head for purposes such as monitoring recorded signals.

[Problem to be solved by the invention]

In such a case, the number of heads increases and the head arrangement becomes complicated. In such cases, the playback head is affected by other heads, especially jitter (referred to as impact jitter) caused by tape vibration at the moment when another head starts contacting the tape or leaves the tape during recording and playback. )
It is necessary to give sufficient consideration to

The present invention relates to means for reducing impact jitter when a recording head and a reproducing head are different.

[Means to solve the problem]

The present invention aims to reduce impact jitter by canceling the impact jitter that occurs during recording and the impact jitter that occurs during playback by improving the symmetry of the head arrangement. The present invention will be explained in detail below based on FIG.

FIG. 5 shows one possible head arrangement.

The figure shows azimuth recording like a VB2 VTR.
This is an example of the arrangement when having both SP and EP recording modes.

A magnetic tape 1 is guided by guides 13 and 16 and is wrapped around a cylinder 2 by more than 180 degrees. It is assumed that each head is rotating in the direction of the arrow. The difference between the layout of FIG. 5 and FIG. 2 is that a new read-only head double azimuth head 3.
4 and 5.6 were added, and the recording-only double azimuth heads 7.8, 9, and 10 were replaced with R/P heads 17 and 18.
, 19.20. There are also two flying erase heads. For this reason, double azimuth reproduction-only heads 5.4, 3, and 6 are placed at the position of the flying erase hect shown in Figure 2 and its symmetrical position, and the flying erase head is placed between the recording-only double azimuth head and the high-fidelity head. It is placed.

In the example shown in Figure 3, the head arrangement is not at equal intervals in the circumferential direction,
Impact jitter becomes a problem. This will be explained below.

The point in time shown in FIG. 3 is exactly the point in time when the flying erase head leaves the tape or enters the tape. At this point, the recording-only double azimuth head 9.10 is scanning the tape by 30 degrees, and the reproduction-only double azimuth head 5.6 is scanning the tape by 90 degrees.In other words, when recording, the recording-only double azimuth head 9 .10 scans 30°, impact jitter occurs due to the flying erase head, and this is recorded on the tape. The same applies to the recording-only double azimuth head 7.8. During playback, jitter occurs due to flying erase hect when the playback-only double azimuth head 5.6 scans the tape 90 degrees.

The same applies to the reproduction-only double azimuth heads 3 and 4, in which the reproduction signal is subject to time axis fluctuations. Figure 4 shows the time when the playback-only double azimuth head 5.6 scans the tape by 60 degrees, and the recording-only double azimuth head 9 during recording.
．． As can be seen from FIG. 4, where 10 indicates the head position at the time when the tape has been scanned through 90°, no head begins to touch or leave the tape at these times. In other words, impact jitter that is recorded when the tape is scanned at 30 degrees and cancels it during playback is also affected by impact jitter that is recorded in advance in the recorded signal so that it cancels out the impact jitter that occurs when the tape is scanned at 90 degrees during playback. Nor. In other words, jitter during recording and jitter during playback are not canceled and appear in the playback signal.

[For production]

In the present invention, by arranging the heads shown in FIG. 5 at equal intervals, the impact jitter that occurs during recording and the impact jitter that occurs during reproduction are canceled.

〔Example〕

An embodiment of the present invention will be described with reference to FIGS. 1 and 5. FIG. FIG. 1 shows the head arrangement of the present invention.

The difference between Fig. 1 and Fig. 5 is the flying erase head 15.
14 is placed close to the high-fidelity heads 11 and 12. Head 12.13, as described below.

Preferably, the head 11.14 has a similar shape to the other double azimuth heads 3°4.3, 6.7, 8.9.10. In the embodiment shown in FIG. 1, the influence of impact jitter due to the flying erase head described in connection with FIG. 3 will be investigated. FIG. 5(,) shows the head position at the time when impact jitter occurs due to the flying erase head. The reproduction-only double azimuth heads 3 and 6 are at the point when the tape has been scanned through 120°, and the recording-only double azimuth heads 9 and 10 are at the time when the tape has been scanned at 60°. At this point, impact jitter is recorded or causes time axis fluctuations in the reproduced signal. FIG. 5(b) shows the double azimuth head 5.0 which is used exclusively for reproducing the signal recorded at the time point shown in (4).
6 indicates the head position at the time of playback. In this case, no impact jitter occurs due to the flying erase head, but instead, a recording-only double azimuth head 7 is used.
．． 8, impact jitter occurs. Therefore, the shape of the recording-only double azimuth head is 7.8.

Protrusion amount and nearby flying erase hect 1
3. If the hi-fi heads 12 have approximately the same shape and protrusion amount, and the spacing (60°) between these heads is accurate,
Jitter during recording and jitter during playback are canceled.

This cancellation does not need to be exactly the same in shape, protrusion amount, or head spacing, as long as it is within a certain error range. Figure 5 (C) shows that the recording-only double azimuth head 7.8
This shows the head position when the playback-only double azimuth head 5.6 scans the tape 120°, which is subject to impact jitter.At this point, impact jitter occurs due to the playback-only double azimuth head 6.4, and this is the recording-only double It is recorded on tape by an azimuth head 7.8. Therefore, if the shape and protrusion of the read-only double azimuth head 5.4 are almost the same as those of the flying erase head 13 and the high-fidelity head 12, and the spacing between each head is exactly equal, the impact jitter caused by the read-only head 6.4 during recording can be reduced. Flying erase head 1 during playback
5, and the impact jitter caused by the /SS sphere head 12. To summarize the above, 4 double azimuth heads 3, 4.3, 6.7, 8.9.1
0 and adjacent head pairs, 13.12 and 11.14
If the shapes and protrusion amounts of the heads are approximately the same and these heads are arranged at equal intervals, all impact jitter caused by the flying erase head (or high-fidelity head) during recording and reproduction will be eliminated.

As is clear from the above description, impact jitter caused by other heads is also canceled if the above conditions are satisfied.

Flying erase head 13 located close to Fig. 6
(or 14) and the head 12 (or 11
) is attached to the cylinder 2, and FIG. (
α) is a view of the rotary cylinder 21 seen from below, and as shown in Figure 6 (Fig. 0, which is a view of the head section from the radial direction)
In addition, these heads are arranged in the same way as normal double azimuth heads for recording and reproducing video signals, and have a similar shape.

The difference is that these heads are not double azimuth, and there is usually a rotation axis direction (see Figure 6) between these heads.
, ), there is a step in the direction perpendicular to the paper surface).

As shown in the figure, the flying erase head 15. /'The head 12 for IFAI is glued to the tip of the HERADO PACE 22, and the head base 22 is attached to the rotating cylinder 21 with the screw 25.
Fixed. These heads are located in a window 24 provided in the rotating cylinder 3. These heads are attached to the head base 22 and wrapped by a wrapping machine, as shown in FIG. 6(,). The tips of the heads each form approximately one arc-shaped part. In other words, they form a single arc shape.

These relationships are the same as those of a double azimuth head for recording and reproducing video signals.

FIG. 6Cb) is a view seen from the radial direction, and as shown in the figure, the high-fidelity head 12 is a head with an azimuth angle, and the flying erase head 15 is a head with an azimuth angle of O, and these heads usually track. The example shown in Figure 0, in which the widths are different and the track center heights are also different, is an example in which a step is created by changing the thickness of the head. As shown in the figure, the difference in height between the center of the track width of the hi-fi head 12 and the center of the track width of the flying erase head 13 is,! If feff is required, the difference in the thickness of these heads is 2et as shown in the figure, and if the center of the head track width of each head is made to coincide with the center of the head thickness, the distance between the centers of these head track widths is d. Particularly in VB2 VTRs, the flying erase head is located at a higher position than other heads, so the above method of changing the head thickness is suitable. Minute height adjustments can be made by providing a height adjustment screw on each head and deforming the head base in the same way as a normal double azimuth head.

Further, as shown in FIG. 7, although the hi-fi head 12° and the flying erase head 15 are placed close to each other, it is of course possible to use separate hect bases.

That is, the hi-fi helad 12 is glued to the helad base 25 and attached to the rotating cylinder 21 with a set screw 27. The flying eraser 13 is glued to the helad paste 26 and attached to the rotating cylinder 21 by screws 28. In such a case, it is extremely easy to provide a step between these heads, and it is sufficient to insert a spacer of an appropriate thickness between either head base and the rotating cylinder 210.

As shown in Figures 6 and 7, the hi-fi Hecht 12
and flying erase head 13 to create other double unmasked heads 3, 4°5, 6, 7, 8 for video recording and playback.
．． It can be made into almost the same shape as 9 and 10.

Above, we have described an example in which there are 21 seconds of recording time modes, SP and EP, and the recording-only head and playback-only head are double azimuth heads, but as is clear from the above, there is only one type of recording time mode. These recording-only double azimuth heads 7.8.9, 10. Even if the read-only double azimuth heads 3, 4, and 5.6 are each single heads, the shape of the head tip is not much different from that of the double azimuth head, and the same impact jitter canceling effect can be obtained.

Furthermore, it is obvious that the present invention cannot be applied even when the recording-only double azimuth head 7.8.9.10 is not a recording-only head but a recording/reproducing head.

Another embodiment of the present invention will be described with reference to FIG. 8. In this embodiment, the high-fidelity head 11 or 12 and the flying erase head 14 or 15 are not placed close to each other, and the reproduction-only double azimuth heads 3 and 4 are .5.6. Recording-only head 7.8.9, 10. Hi-fi head 11.12
, the flying erase heads 13 and 14 are arranged at equal intervals of 45 degrees as shown in the figure. As mentioned above, the tip shape (scanning direction curvature and protrusion amount) of the single head 11, 12° 13.14 can be made almost the same as that of the double azimuth head 3, 4.5t6.7, 8.9.10. As is obvious from the description up to now, the 8th
In the arrangement shown in the figure, the impact jitter during recording and the impact error during playback can cancel each other out.

In addition, in Fig. 8, the reproduction-only double azimuth head 5
．． 4 (or 5.6) and recording-only double azimuth head 7
．． 8 (or 9.10) is set to 90° because the wider the interval, the greater the effect of canceling jitter other than the impact jitter accompanying recording/reproduction separation. This is for the reasons described below. The jitter that is particularly noticeable on the playback screen due to recording/reproduction separation is the frequency component of around 1 kHz, which in VB2 VTRs becomes vertical line bends and horizontal color stripes. Jitter caused by recording/reproduction separation is caused by a difference in cylinder rotational phase between when a signal is recorded and when a signal is reproduced. This rotational phase difference is the angular difference between the recording head and the reproducing head, which is 90° in the arrangement shown in FIG. If this angle difference can be made very small,
The smaller the angle difference, the better.

The smaller it is, the closer it is to self-recording and replaying. However, when it cannot be made smaller for various reasons (for example, the size of the head base), another phenomenon occurs. The dominant phenomenon in this case is that a specific frequency jitter determined by the head angle difference is canceled during recording and reproduction. This is a phenomenon in which jitter frequency components that have the same phase at the recording head position and the reproducing head position are canceled. Assuming that the distance between the recording head and the reproducing head is 45°, the frequency component to be canceled is 8 per rotation.
This results in jitter components that change periodically and their multiples. If the cylinder is rotating at 30Hz, the canceled component will be 240 x nHz (%: natural number).If the head spacing is 90°, this will be 120 x nHz.
It becomes gz. In other words, the larger the head spacing, the shorter the interval between canceled jitter frequency components, and the more frequency components are canceled during reproduction.

As shown in Figures 6 and 7, the shapes of the tips of the adjacent heads are 1.
If the head is a part of an approximately circular arc shape and its curvature is approximately equal to that of other heads, the effect of canceling impact jitter is very large. However, even if the tips of these heads have independent arcuate shapes, they have a canceling effect if they are very close to each other and are not considered as two consecutive impacts.

FIG. 9 shows still another embodiment of the present invention. This embodiment is located exactly in the middle of the recording-only head 7.8 or 9.10 and the reproduction-only head 3, 4, or 5.6 of the example shown in FIG. 5. Dummy heads 30 and 5 each having a tip shape and protrusion that are approximately the same as the other heads are placed exactly in the middle of 5 and 6.
1,52.55, each head has a total of 50
They are arranged at equal intervals in the circumferential direction at intervals of . By using a dummy head in this way,
It is possible to expand the selection range of each head spacing and cancel all impact jitter during recording and playback. Note that the dummy heads 30, 51, 32, and 33 do not require precise posture adjustment, so for example, the head chip can be directly bonded to the rotating cylinder 21 as it is, and the cost increases by adding the dummy heads. can be reduced by a very small amount.

〔Effect of the invention〕

According to the present invention, with a simple configuration, a high-quality image with little video jitter can be obtained with a rotating magnetic head device including a high-fidelity head and a flying erase head when playing back with a head separate from the recording head. .

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the head arrangement in a cylinder according to an embodiment of the present invention, FIG. 2 is a diagram showing the head arrangement in a cylinder of a conventional VTR, and FIG. 5 is a diagram showing an example of a possible head arrangement. Figure 4 shows the head position at different cylinder rotational phases with the head arrangement shown in Figure 6, and Figure 5 shows the head position at different cylinder rotational phases with the arrangement shown in Figure 1. , FIG. 6 is a diagram showing a no-ify head and a flying erase head placed close to each other,
7 is a diagram showing another embodiment of FIG. 6, FIG. 8 is a diagram showing the head arrangement of another embodiment of the present invention, and FIG. 9 is a diagram showing still another embodiment of the present invention. be.

Claims (1)

[Claims] 1. Recording-only or recording/reproducing head (7, 8, 9, 1
0), read-only heads (3, 4, 5, 6) and other heads (11, 12, 13, 14, 30, 31, 3).
2, 33), wherein the heads arranged in close proximity are regarded as one head, and the heads are arranged at equal intervals in the circumferential direction. 2. At least one of the heads arranged close to each other heads (11, 12, 13, 14, 30, 31, 32
, 33). The rotary magnetic head device according to claim 1. 3. The rotary magnetic head device according to claim 1 or 2, wherein the tips of the heads arranged close to each other are each formed into a part of a circular arc shape. 4. Closely arranged heads (12, 13 or 11, 14
) are fixed on the same head base (22). 5. Closely arranged heads (12, 13 or 11, 14
5. The rotary magnetic head device according to claim 4, wherein the head thicknesses of the two heads are different from each other. 6. Recording only or recording/reproducing head (7, 8 or 9,
2. The rotary magnetic head device according to claim 1, wherein the read-only head (3, 4, or 5, 6) is arranged at an interval of 90 degrees from each other, with the proximity head being regarded as one head.