JPS609930Y2 - magnetic recording and reproducing device - Google Patents

Description

[Detailed explanation of the invention] A recording/playback device that records video signals on magnetic tape, the so-called V
As shown in FIG. 1, in a TR, normally, two rotating magnetic heads HA and H are mounted with an angular spacing of 180°, and a tape 1 is obliquely mounted on a tape guide drum 2 over an angular range of approximately 180°. The head H
Rotate so that A and HB rotate once in one frame,
As shown in FIG. 2, diagonal tracks TA and Ta are alternately formed in each field by heads HA and H8.

Then, the track T formed by the heads HA and HB
The running speed of the tape 1 is selected so that a so-called guard band is formed between ^ and Ta.

Furthermore, in consideration of the fact that the head will scan across two or more tracks during slow-motion playback or still playback, measures should be taken to prevent horizontal synchronization signals from other tracks from being mixed in as noise. Therefore, as shown in FIG. 2, the recording positions PM of the horizontal synchronizing signals are aligned between tracks TA5-TB%.

That is, between adjacent tracks, the recording start positions of the tracks recorded on the magnetic tape 1 are sequentially separated by one horizontal section (I
H) 1. The diameter of the guide drum is selected so that the guide drums are shifted by a certain distance.

By the way, with such a recording/reproducing machine, the amount that can be recorded on one tape is limited to about one hour, although it depends on the length of the tape and other factors.

However, programs such as movies and sports often last more than one hour, and when recording such programs, it is desirable to be able to record as long as possible on a tape of limited length.

One possible method for increasing the recording amount is to reduce the track width and therefore the width of the guard band.

However, in order to do this, it is necessary to reduce the gap width of the head, but with the current manufacturing technology, it is difficult to make the gap width much smaller than the conventional one.

For this reason, a method of recording without forming a guard band, that is, in such a way that each track is in contact with each other, can be considered.

When such a recording method is used, crosstalk from adjacent tracks becomes a problem during reproduction, and therefore it is required to eliminate or reduce this crosstalk by some method.

A method to solve this problem has already been proposed.

That is, as mentioned above, two rotating magnetic heads HA and HB
When using heads HA and H, as shown in FIG.
The angles of inclination of the gaps gA and g8 of B with respect to the scanning direction shown by the arrow 3 are made to be different from each other.

Since the video signal is generally recorded by angle modulation, for example, FM modulation, when the heads HA and HB are configured as described above, the track TA formed by the head HA, as shown in FIG. Even if the tape speed is selected to be slow so that the track TB and the track TB formed by the head HB are in contact with each other, that is, there is no guard band,
During reproduction, crosstalk is significantly reduced due to the so-called azimuth loss due to the difference in slope of the gaps gA and ga between the heads HA and Hn.

Therefore, since the track pitch can be reduced, the recording amount can be increased.

However, when recording at a slow tape speed, for example, when the tape speed is set to the speed shown in Figure 2, the diameter of the guide drum is changed to the same speed as shown in Figure 2. If the horizontal synchronizing signal recording positions P and 4 on each track are not changed, as shown in FIG. 3, they will not be aligned.

In other words, the recording start positions of the tracks on tape 1 will be shifted by 0.7 IH (1.5×) between adjacent tracks, and the recording positions P14 of the horizontal synchronization signals will not be aligned. be.

However, during this playback, the widths of heads H8 and HB are wider than the track width, so for example, when playing track TA with head HA, the same amount of tracks TB before and after it are played back, as shown in FIG. As a result, crosstalk between the horizontal synchronizing signals in the reproduced signals from the tracks Tn before and after this occurs, deteriorating the image quality.

In view of the above-mentioned points, this invention makes it possible to almost eliminate the influence of horizontal synchronizing signal crosstalk without changing the diameter of the guide drum or the tape speed as before.

Hereinafter, an example of the magnetic recording/reproducing apparatus according to this invention will be explained with reference to FIGS. 4 to 6.

That is, in this invention, the pair of rotating magnetic heads and HB are not installed with an angular spacing of 180°, but rather with an angle α slightly smaller than 180°, as shown in FIG. α is shifted by an angle corresponding to 0.25H.

Further, in this example, the head H8 is mounted on an electromechanical transducer, such as the bimorph plate 4.

As is well known, this bimorph plate is made up of two plates made of piezoelectric elements glued together, and when a voltage is applied to this bimorph plate 4, it is distorted according to the magnitude of the applied voltage. Due to the distortion of this bimorph plate, Ha is mounted so as to move in a direction perpendicular to the scanning direction.

If a video signal is recorded by the rotating magnetic heads HA and HB at a slow tape speed in the same way as the recording shown in FIG. 3, the recording pattern will be as shown in FIG. 5.

That is, each video signal for one frame, for example, one field in the first half, is sent to the head HA on the track TA19.
Each field is recorded in the form of TA2......, and the second half of the field is track TBI? on the head HB. Ta2...... are recorded respectively, but head HB reaches track TB□ 0.25H earlier than in the case of FIG.

As Ta2...... starts to take shape, the tracks TA□ and Tnl, TA2 and TB□...
. . ., the recording positions PH of the horizontal synchronizing signals are aligned as shown in FIG.

In this case, the horizontal synchronizing signals are not aligned between tracks T,1 and TA□, tracks TB2 and TA3, . . . .

To reproduce a magnetic tape recorded in this manner, the following procedure is performed.

That is, FIG. 6 shows an example of a playback system of the device according to this invention, and this example is designed to be able to play back even a conventional recorded tape having a recording pattern as shown in FIG. This is an example.

Reference numerals 11 and 12 are switches which are switched between when reproducing a conventional recorded tape and when reproducing a recorded tape according to this invention described above, and the state shown in the figure is when reproducing a tape recorded according to this invention.

That is, in this reproducing state, a predetermined DC voltage is applied to the bimorph plate 4 from the DC power source 10, and the head HB is moved in the direction in which the tape 1 travels in a direction perpendicular to the scanning direction. The width of the gap gn is moved by an amount wider than the width of the track, and the tape is scanned in this state.

Then, at this time, HA is set to the same tracking phase as during recording.

In this way, as shown at the right end of FIG. 5, the head H^ is moved to the track TA1. which is to be scanned by this head. Ta
2...and the track TB1 whose horizontal synchronization signals are aligned among the tracks adjacent to these tracks? Now, only a part of Ta2...... is scanned, while head H8 is scanning the track TBI? which this head should scan. Ta2・・・・・・・・・
...and the tracks TA□, Ta2, for which the horizontal synchronization signals are aligned respectively with respect to these tracks...
...will scan only a part of it.

The signals reproduced by the heads HA and HB thus configured are supplied to a limiter circuit 7 through amplifiers 5 and 6, respectively, and the output of this limiter circuit 7 is supplied to a frequency demodulation circuit 8 where it is demodulated. , the demodulated video signal is taken out at the output terminal 9.

As described above, the heads HA and HB always scan only the tracks in which the recording positions of horizontal synchronization signals are aligned, and crosstalk of horizontal synchronization signals from adjacent tracks becomes almost no problem. .

Next, when playing back a conventional recorded tape, switches 11 and 12 are switched to the opposite state from that shown.

Then, the output of the head H8 passes through the amplifier 6, is supplied to the delay circuit 13, is delayed by 0.25H, and is supplied to the limiter circuit 7.

That is, in this device, the head HB reaches the track TB of the magnetic tape 1 0.25H earlier than the conventional device.
However, this delay circuit 13 causes the head H to start scanning.
Since the output of B is delayed by 0.25H, the outputs of heads HA and HB supplied to the limiter circuit 7 are similar to the conventional one in which the angular interval between these heads HA and HB is 180°. Become.

Therefore, the same reproduction as before is performed.

Note that at this time, no DC voltage is applied to the bimorph plate 4 from the power source 10, and the scanning position of the head HB cannot be changed.

As described above, according to this invented device, the recording position of the horizontal synchronization signal can be aligned with one of the adjacent tracks by simply changing the angular spacing between a pair of heads. It can be recorded as follows.

During playback, a pair of heads scans the two tracks in which the recording positions of the horizontal synchronization signals are aligned, thereby preventing crosstalk between the horizontal synchronization signals from tracks adjacent to the playback signals. It is possible to eliminate the influence of

Moreover, in this invention, no design changes are made to the diameter of the guide drum of the rotary head device commonly used in the past, so even tapes recorded with the conventional device can have the delay circuit on one side. Just by providing it for the head output, the same playback as before can be achieved.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of a rotary head device of a conventional device; FIG. 2 is a diagram showing an example of its recording pattern; FIG. 3 is a diagram showing an example of a recording pattern when the tape speed is slowed;
FIG. 4 is a diagram showing an example of a rotary head device of this invented device, FIG. 5 is a diagram showing an example of its recording pattern, and FIG. 6 is a system diagram showing an example of a reproduction system of this invented device. HA and HB are a pair of rotating magnetic heads, 1 is a magnetic tape, 2 is a guide drum, and 4 is a bimorph plate.

Claims (1)

[Scope of utility model registration request] At least a pair of rotating magnetic heads scan a recording medium in such a manner as to partially scan adjacent tracks, thereby forming one track each and recording a video signal. The horizontal synchronizing signals are aligned with one of the adjacent tracks, and during reproduction, at least one of the rotating magnetic heads can move in a direction perpendicular to the direction of rotation thereof, and By controlling the position in a direction perpendicular to the direction of rotation, each of the rotating magnetic heads scans only a track to be scanned and a portion of the one track to which the horizontal synchronization signal is aligned. A magnetic recording and reproducing device designed to scan.