JPH02247853A - Rotation controller for rotary magnetic head drum - Google Patents

Abstract

PURPOSE:To promote the control sensitivity of a motor for a rotary magnetic head drum by comparing a reference phase signal obtained by dividing a horizontal synchronizing signal of a video signal with a rotation detecting pulse signal of each revolution of the rotary magnetic head drum in phase. CONSTITUTION:With regard to such a system that one field of a television video signal is divided into segments 22, 23..., each having parallel three tracks to be recorded and reproduced in turn on a magnetic tape 21, it is necessary to rotate the rotary magnetic head drum 7 at 5,400 r.p.m. as about three times as much as the conventional speed. Therefore, the pulse signal obtained from a rotation detecting pulser 8 under 5,400 r.p.m. i.e. 90 revolutions per sec as every 1/90sec is compared in phase with the reference phase signal obtained by dividing the horizontal synchronizing signal of the video signal every 1/3sec, and the motor 12 is rotationally controlled by an obtained phase error signal. That is, since a control can be obtained every 1/90sec, the motor control is feasible with higher accuracy than the case of obtaining the reference phase signal from a vertical synchronizing signal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a rotation control device for a rotating magnetic head drum in a video tape recorder for recording and reproducing high-definition television video signals.

[Conventional technology]

In conventional helical scan video tape recorders, which have been widely used, magnetic tape is wound spirally around a rotating magnetic head drum equipped with a magnetic head.
The rotating magnetic head drum is rotated while the magnetic tape is moved at a constant speed, and the magnetic head slides and scans the magnetic tape to record television video signals in parallel straight tracks. In this case, as shown in FIG. 3, one field of the video signal has been recorded on each of the video signal tracks 32, 33, . . . in the central portion 31a of the magnetic tape 31. In addition, the magnetic tape 31
An audio signal and a control signal to be described later are recorded on both edge portions 31b and 31c, respectively.

Tracks 32 and 33 of the above television video signal...
The width of the magnetic head is a minute dimension of about 20 μm at the minimum, and the magnetic head records such narrow tracks at equal intervals and accurately traces them during playback (in order to do this, the rotation of the rotating magnetic head drum must be controlled). As such a rotation control method, the one shown in FIG. 4 is known.

That is, when the video signal is applied to the vertical synchronization separation circuit 41, the vertical synchronization signal is separated, the frequency is divided by the 1/2 frequency divider circuit 42, and the waveform is shaped by the shaping circuit 43.
The reference phase signal is input to the phase comparator circuit 44 as a reference phase signal.

On the other hand, a rotating magnetic head drum 4 with a rotation speed of 1800 revolutions per minute
After passing through a delay circuit 47 for setting a constant initial phase with respect to a reference phase signal, a pulse signal generated from a rotation detection balsa 46 that detects each rotation of the rotation sensor 5, that is, 30 pulse signals per second, passes through a delay circuit 47 for setting a constant initial phase with respect to a reference phase signal. The signal is waveform-shaped by a pulse shaping circuit 48, and is further inputted to a phase comparison circuit 44 for phase comparison with the reference phase signal, thereby obtaining a phase error signal. After this phase error signal is amplified by an error amplifier 49, it is applied to a motor 50 that rotates a rotary magnetic drum 45, and at the same time controls the rotation of the motor 50. The information is recorded on the edge portion 31c of the magnetic tape 31 shown in FIG. 3 as a control signal during playback.

As described above, the motor 50'8 etc. control the rotation of the rotating magnetic head drum 45, and
As shown in FIG. 3, images are sequentially recorded on the magnetic tape 31 by one field per track by the two heads 45a and 45b provided on the magnetic tape 5.
Once per rotation of the rotating magnetic head drum 45, that is, once per rotation of the rotating magnetic head drum 45.
Rotation control is performed once per frame (2 fields).

By the way, in new television video signals such as high-definition systems, the horizontal scanning line is 112 per frame.
There are as many as 5, and the necessary frequency bandwidth is also about 30 MHz, and recording thereof requires about three times the frequency band compared to the conventional method.

Therefore, for example, a method has been considered in which the magnetic head is rotated at three times the conventional speed, that is, 5,400 revolutions per minute, and one field of video is recorded on the magnetic tape by dividing it into three segment tracks. There is. That is, during playback, during one field period, the above three fields constituting this one field are
The tracks of the book are played back one after the other and stitched together 1/3 in the vertical direction of the screen to reproduce one field. In this case as well, the reference signal for controlling the rotating magnetic head drum is still obtained from the vertical synchronization signal, and one pulse from the rotation detection pulser is generated every 1790 seconds. Similarly, a phase error signal can only be obtained for each frame. That is, a phase error signal is obtained only every six tracks.

[Problems to be Solved by the Invention] However, as described above, if the phase error signal is detected only once for six tracks, (1) the phase control sensitivity per track decreases. That is, the rotation control of the rotating magnetic head drum becomes insufficient, resulting in an increase in video jitter during playback. Also, the joints of the three tracks are shifted to the left and right,
This has the problem that skew distortion tends to occur.

[Means to solve the problem]

The rotation control device for a rotating magnetic head drum according to the present invention includes:
In order to solve the above problems, a rotating magnetic head drum is rotated in a video tape recorder that divides one field of a television video signal into three parallel segment tracks and sequentially records and reproduces them on a magnetic tape. In the control device, the phase of the reference phase signal obtained by dividing the horizontal synchronization signal of the television video signal and the rotation detection pulse signal generated by detecting the rotation of the rotating magnetic head drum every rotation is compared. The present invention is characterized in that the motor of the rotating magnetic head drum is controlled by the phase error signal obtained.

[For production]

By configuring as described above, a reference phase signal can be obtained, for example, every ⅓ of the horizontal period, that is, every 1/9o seconds. In addition, the rotating magnetic head drum rotates at three times the speed of conventional ones, so it rotates at 5,400 revolutions per minute, or 9 per second.
A pulse signal is obtained from the rotation detection pulser every 1/90 seconds at 00 rotations. Therefore, the phase of the pulse signal obtained from this rotation detection pulser is compared with the reference phase signal obtained by frequency-dividing the horizontal synchronization signal, thereby obtaining a phase error signal, which is used to rotate the motor of the rotating magnetic head drum. can be controlled.

That is, since the control signal is obtained every 1/90 seconds, it is possible to control the motor B with higher precision than when obtaining the reference phase signal from the vertical synchronization signal. Therefore, it is possible to reduce video jitter that tends to occur during playback, as well as reduce or prevent skew distortion that tends to occur at the seam of each track when configuring one field screen, and avoid deterioration in image quality. I can do it.

〔Example〕

An embodiment of the present invention will be described below based on FIGS. 1 and 2.

A case will be described in which a high-visibility television video signal is recorded by a helical scan video tape recorder.

In this embodiment, it is necessary to record a frequency band approximately three times larger than that of a conventional home video tape recorder. Therefore, as shown in FIG. 2, one field of video signal is divided into three segment tracks 22', 22", and 22# in the central portion 21a of the magnetic tape 21, and the track per field is lengthened. In other words, a track group 22 consisting of three segment tracks 22' to 22#, and a track group 23 consisting of the next three segment tracks 23' to 23''. One frame of the video signal is formed by these. Note that both edge portions 21 of the magnetic tape 21
b and 21c form recording bands for audio and control signals to be described later, respectively.

In such a recording format, the rotating magnetic head drum must be rotated at three times the conventional speed, that is, 5400 revolutions per minute.

The control circuit for the above-mentioned rotating magnetic head drum is as shown in FIG.

That is, the video signal of the television signal is applied to the input side of each of the horizontal synchronization separation circuit 1 and the vertical synchronization separation circuit 2, and the horizontal synchronization separation circuit 1
The output side of is connected to the input side of the counter circuit 4, while the output side of the vertical synchronization separation circuit 2 is connected to the input side of the 1/2 frequency divider circuit 3, and the output side of the 1/2 frequency divider circuit 3 is It is configured to be input to the counter circuit 4.

The output side of the counter circuit 4 is connected to the input side of a shaping circuit 5, and the output side of this shaping circuit 5 is connected to the input side of a phase comparison circuit 6.

On the other hand, the output of a rotation detection pulser 8 that detects the rotation of the rotating magnetic head drum 7 every rotation is applied to the phase comparison circuit 6 through a delay circuit 9 and a pulse shaping circuit 10.

The output side of the phase comparison circuit 6 is connected to the input side of an error amplifier 11, and the output side of the error amplifier 11 is connected to a motor 12 that rotates the rotating magnetic head drum 7 via a rotation control mechanism (not shown). There is.

Note that the rotating magnetic head drum 7 has two holes at 180° intervals.
magnetic heads 7a and 7b are provided. The rotating magnetic head drum 7 rotates at 5400 revolutions per minute, ie, 900 revolutions per second, during recording and reproduction.

In the above configuration, when a high-visibility control television video signal is input to the horizontal synchronization separation circuit 1 and the vertical synchronization separation circuit 2, the horizontal synchronization signal is separated in the horizontal synchronization separation circuit 1 and applied to the counter circuit 4. . In the counter circuit 4, 1125/3, that is, 37
A reference pulse signal is generated by the rising or falling signal of every fifth horizontal synchronizing signal.

On the other hand, in the vertical synchronization separation circuit 2, the vertical synchronization signal of the video signal is separated, frequency-divided by the 1/2 frequency divider circuit 3, and then inputted to the counter circuit 4.
Reset.

The time interval of the reference pulse signal generated every 375 rising or falling signals of the horizontal synchronization signal is 1/90.
On the other hand, since the time interval of the vertical IU] signal whose frequency is divided by 1/2 is 1/30 seconds, the reference pulse signal generated by the counter circuit 4 is generated by the vertical synchronization signal every 3 pulses. It will be output while being synchronized. Note that even in the high-definition system, horizontal scanning lines are interlaced, so the horizontal synchronization 14 wave number is set to an odd multiple of the vertical synchronization frequency, the period of one field is l/60 seconds, and the period of one frame is i / It is 30 seconds.

The above reference pulse signal! - is shaped into a trapezoidal wave or the like in the shaping circuit 5 to form a reference phase signal, which is input to the phase comparison circuit 6.

On the other hand, for every rotation of the rotating magnetic head drum 7, two pulses are generated from the rotation detection balsa 8.
After being delayed by a delay circuit 9 for setting a constant initial phase, an edge signal of the L pulse signal is extracted in a pulse shaping circuit 10, and this edge pulse is applied to a phase comparator circuit 6 to compare the phase with the reference phase signal. By comparing, a phase error signal (voltage) is obtained. This phase error signal is amplified by an error amplifier 11 and then applied to a motor 12 that rotates a rotary magnetic head drum 7 via a control mechanism (not shown). As a result, motor 1
The rotation of the magnetic tape 21 is controlled, and the edge portion 21c of the magnetic tape 21 shown in FIG.
The rotation control signal is recorded on a control signal recording band provided in the control signal recording band, and becomes a rotation control signal during playback.

2 provided on the rotating magnetic head drum 7 at 180° intervals.
The magnetic heads 7a and 7b sequentially record video signals in a pattern as shown in FIG. 2 while slidingly scanning the magnetic tape 21 moving in one direction.

Here, the rotating magnetic head drum 7 rotates at three times the rotational speed of the conventional one, so 5400 rotations per minute, that is, 90 rotations per second.
Rotates 0 times. Therefore, it rotates three times in one frame period, that is, 1/30 second, and records a six-segment track. That is,
One field consists of three segment tracks, one
/ Two segment tracks are recorded every 90 seconds. Further, the reference phase signal is outputted every 1790 seconds as described above, and the rotation detection balsa 8 also generates a pulse every 1/90 seconds, so the motor 12 that rotates the rotating magnetic head drum 7 is outputted every 1/90 seconds. The rotation is controlled every second, that is, every two segment tracks.

If such rotation control is performed using the conventional method of using the vertical synchronization signal as the reference pulse, it can only be performed every frame, that is, every 6 segment tracks. According to the invention, it is important to keep the rotation control sensitivity of the rotating magnetic head drum 7 sufficiently high, thereby suppressing jitter and distortion of reproduced images.

In the above embodiment, the case of recording a television signal using the high-definition system (2) was explained, but even in a conventional television system, for example, the NTSC system,
It can be applied in exactly the same way when recording and reproducing at twice the speed.

However, in this case, one frame of horizontal synchronization signal 525
A reference phase signal is generated every 525/3, that is, every 175 horizontal synchronization signals. Therefore, in this case as well, 3 (2
The rotation of the rotary magnetic head drum 7 can be controlled by one reference phase signal per segment track.

〔Effect of the invention〕

The rotation control device for a rotating magnetic head drum according to the present invention includes:
As described above, in a rotation control device for a rotating magnetic head drum of a video tape recorder that divides one field of a television video signal into three parallel segment tracks and sequentially records and reproduces them on a magnetic tape, The phase obtained by comparing the phase between the reference phase signal obtained by frequency-dividing the horizontal synchronization signal of the above-mentioned TV Dibon video signal and the rotation detection pulse signal generated by detecting the rotation of the rotating magnetic head drum every rotation. The configuration is such that the motor of the rotating magnetic head drum is controlled by the error signal.

This allows once every two segment tracks,
That is, since the phase error signal can be detected three times per frame, the control sensitivity of the motor that drives the rotating magnetic head drum can be maintained sufficiently high. Therefore, it is possible to reduce or prevent the occurrence of jitter in the reproduced image and skew distortion at the seam of three segment tracks, and it is possible to reproduce a stable image.

[Brief explanation of drawings]

1 and 2 show an embodiment of the present invention, in which FIG. 1 is a block diagram showing the configuration of a rotation control device;
FIG. 2 is an explanatory diagram showing a recording pattern on a magnetic tape. 3 and 4 show conventional examples.
The figure is an explanatory diagram showing a recording pattern on a magnetic tape.
FIG. 4 is a block diagram showing the configuration of the rotation control device. 1 is a horizontal synchronous separation circuit, 2 is a vertical synchronous separation circuit, 4 is a counter circuit, 6 is a phase comparison circuit, 7 is a rotating magnetic head drum, 8 is a rotation detection pulser, 12 is a motor, 21 is a magnetic tape, 22'-- 22#23' to 23# are segment tracks.

Claims (1)

[Claims] 1. One field of a television video signal is divided into three parallel
In a rotation control device for a rotating magnetic head drum in a video tape recorder that divides into segment tracks and sequentially records and plays back on a magnetic tape, a reference obtained by frequency-dividing the horizontal synchronizing signal of the above-mentioned television video signal is used. The motor of the rotating magnetic head drum is controlled by a phase error signal obtained by comparing the phase of the phase signal with a rotation detection pulse signal generated by detecting the rotation of the rotating magnetic head drum every rotation. A rotation control device for a rotating magnetic head drum, characterized in that: