JPS6244327B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a video signal recording system, in which a rotational phase error of a rotary head caused during recording due to disturbance is detected as a comparison signal, and a phase error voltage obtained from this comparison signal and a reference signal is used. By displacing the rotary head in the longitudinal direction of the tracks accordingly, the horizontal synchronization signals recorded on each track can be recorded in a simple manner so that they are aligned with high accuracy between the tracks, resulting in less crosstalk and improved S/ It is an object of the present invention to provide a recording method capable of obtaining stable and high-quality images of N.

In helical scan magnetic recording and reproducing devices such as VTRs, which record and reproduce video signals by sequentially forming tracks on a magnetic tape that are inclined with respect to the longitudinal direction of the magnetic tape using a rotating head, it is possible to reproduce more stable and high-quality reproduced images. In order to obtain this, it is necessary to perform recording with higher precision in so-called H alignment, in which the recording positions of each recording horizontal synchronizing signal between adjacent tracks are aligned in a line.

FIG. 1 shows a block system diagram of an example of a conventional video signal recording system. In the figure, a video signal to be recorded that has entered an input terminal 1 is supplied to a video signal recording system 2 and a reference signal generation system 3, respectively. The video signal recording system 2 processes the video signal into a signal format suitable for magnetic recording and outputs it to rotary heads 10a and 10b, which rotate integrally with a rotary drum 9, which will be described later, and have, for example, different azimuth angles. . On the other hand, the reference signal generation system 3 separates the vertical synchronizing signal from the input video signal and shapes the waveform of the signal, for example, 30
A symmetric square wave of Hz is generated as a reference signal and supplied to the phase comparator 4.

The rotating drum 9 is rotated by a drum motor 8, and magnets 11a and 11b are attached at positions facing each other at 180 degrees. Since the magnets 11a and 11b are configured to cross in front of the pick up head 5 as the rotary drum 9 rotates, a rotation detection signal is output from the pick up head 5 every time the magnets 11a and 11b pass, and a comparison signal is generated. system 6. A trapezoidal wave signal synchronized with the rotational phase of the rotary drum 9 is generated by the comparison signal generation system 6 and sent to the phase comparator 4.
The signal is supplied to the reference signal, where the phase is compared with the reference signal. As a result, a phase error voltage corresponding to the error in the rotational phase of the rotating drum is extracted from the phase comparator 4 and supplied to the disk drive control system 7. This disc control system 7 keeps the rotational speed of the drum motor 8 constant and at the same time controls the rotational phase to match the reference signal using the phase error voltage from the phase comparator 4. For example, when the rotational speed of the rotary drum 9 becomes faster than the steady speed, the phase of the output comparison signal of the comparison signal generation system 6 advances, and the phase error voltage from the phase comparator 4 decreases correspondingly, causing disk drive control. The system 7 reduces the rotational speed of the drum motor 8, thereby maintaining the rotational speed and rotational phase of the rotating drum 9 in a constant steady state.

In this way, the drum servo system rotates the rotary drum 9 and the rotary heads 10a and 10b so that the rotational speed and rotational phase are constant, so that the rotary drum 9 is rotated approximately 180 degrees as shown by the one-dot chain line. The input video signal is recorded on the magnetic tape 12, which is attached to the magnetic tape 12 and is made to run in the longitudinal direction thereof, by sequentially forming tracks that are inclined with respect to the longitudinal direction of the magnetic tape 12. The vertical synchronizing signal recording position and the horizontal synchronizing signal recording position of the track are aligned in a fixed direction.

However, in reality, the rotating heads 10a and 10b
The disadvantage is that the time axis of the video signal drifts due to disturbances such as rotational irregularities, and the recording positions of the horizontal synchronizing signals are not necessarily aligned in a certain direction with high precision. When a magnetic tape in which the horizontal synchronizing signal recording positions are not precisely aligned is reproduced, there is a drawback that crosstalk from adjacent tracks becomes noticeable. This drawback does not cause any major problems in terms of the tape speed, track width, etc. used in conventional magnetic recording and reproducing devices such as VTRs, and crosstalk from adjacent tracks can usually be adequately dealt with by using the azimuth recording method. .

However, from the viewpoint of realizing a method for recording video signals for as long as possible on a magnetic tape of limited length, as the running speed of magnetic tape decreases,
The above-mentioned drawbacks become noticeable as a negative effect due to a decrease in the actual track width, a deterioration in the S/N due to a decrease in the recording level, etc. This negative effect causes crosstalk and a deterioration in the S/N of the reproduced image, and depending on the picture, The quality of the reproduced image was degraded.

The present invention eliminates the above-mentioned drawbacks, and an embodiment thereof will be described below with reference to FIGS. 2 to 4.

FIG. 2 shows a block system diagram of an embodiment of the video signal recording system according to the present invention. In the figure, the same components as in FIG. 1 are denoted by the same reference numerals, and their explanations will be omitted. In FIG. 2, an input terminal 13 receives a video signal to be recorded. Here, in the specification of this application, "video signal" of course refers to a black and white video signal or a color video signal, but a modulated digital signal obtained by pulse code modulating an audio signal or other analog information signal is a composite video signal. It also includes digital signals that are present at the video signal position.

The color video signal input from the input terminal 13 is
The signal is supplied to a low-pass filter 14 and a band filter 15, respectively, and is also supplied to a vertical synchronization signal separation circuit 16, where the vertical synchronization signal is separated and output. This vertical synchronizing signal is counted down to 1/2 by a monostable multivibrator (hereinafter abbreviated as "monomulti") 17 and then supplied to the phase comparator 4 via a pulse shaping circuit 18. Each of the circuits 16 to 18 has the same configuration as the reference signal generation system.

On the other hand, the rotation detection signal detected by the pickup head 5 triggers the monomultis 19 and 20 alternately every half rotation of the rotating drum 9. Pulses alternately taken out from the monomultis 19 and 20 every half rotation of the rotary drum 9 are applied to the flip-flop 21 to trigger it. As a result, a symmetrical square wave whose period corresponds to one revolution of the rotary drum 9 is extracted from the flip-flop 21, converted into a trapezoidal wave by the trapezoidal waveforming circuit 22, and then supplied to the phase comparator circuit 4. The circuits 19 to 22 described above have the same configuration as the comparison signal generation system 6.

That is, the phase comparator 4 compares the phases of the reference signal from the pulse shaping circuit 18 and the trapezoidal wave (comparison signal) from the trapezoidal wave forming circuit 22 obtained in the same manner as before, and adjusts the phase difference according to the phase difference between them. While the phase error voltage is supplied to the disc control system 7, in this embodiment, the rotating heads 10a and 10b are fixed to one end of the bent bimorphs 23a and 23b, which will be described later.
to control the amount and direction of mechanical displacement.

On the other hand, the input color video signal is applied to the rotary heads 10a, 10b via a well-known video signal recording system. That is, the luminance signal is extracted from the color video signal by the low-pass filter 14, the pedestal level is clamped by the clamp circuit 24, and then passed through the pre-emphasis circuit 25 and the white/dark clip circuit 26 to the frequency modulator 2.
7, where it is frequency modulated. This frequency modulated luminance signal is supplied to a mixer 32 after its low frequency components are removed by a high frequency filter 28 so as to be multiplexed with a low frequency modulated carrier color signal, which will be described later.

Further, the carrier color signal is separated and extracted from the input color video signal by the band filter 15,
This carrier color signal passes through an ACC circuit 29 and a color signal processing circuit 30, and is frequency-converted to a frequency lower than that of the frequency-modulated luminance signal, and in one field period, the phase advances by 90 degrees every horizontal scanning period. In the next field period, the phase is delayed by 90 degrees every horizontal scanning period, which is alternately applied to each field, and then supplied to the low-pass filter 31, where unnecessary frequency components are removed and mixed. 32, where it is frequency division multiplexed with the frequency modulated luminance signal. The frequency division multiplexed signal taken out from the mixer 32 is supplied via a recording amplifier 33 to rotary heads 10a and 10b having different azimuth angles, and these alternately capture one track per field. They are formed and sequentially recorded on a magnetic tape 12 that is run at a constant speed by a stun servo system (not shown). FIG. 4 is a diagram showing an example of a track pattern on the magnetic tape 12, where t ₁ , t ₂ , and t ₃ are tracks on which one field of the frequency division multiplexed signal is recorded, and 38 is a track that is scanned in the direction of arrow 39. One of the rotating heads 10a or 10b is shown. Further, the solid line portions in each track t ₁ , t ₂ , t ₃ indicate the horizontal synchronizing signal recording position.

By the way, according to this embodiment, the rotary head 10
a, 10b are mechanically connected to the rotating drum 9 and rotating head 10 by bent bimorphs 23a, 23b.
The displacement is made to correct the influence of the rotational phase error of a and 10b. That is, in Figure 2,
As shown in FIG. 3, which is an enlarged view of the part surrounded by the broken line A, piezoelectric plates 35 and 36 made of piezoelectric elements such as piezoelectric ceramics are laminated on both sides of the conductive flexible plate 34 so that their bending polarities are in opposite directions. A rotary head 10 is attached to the tip of the bent bimorph 23a.
The gap surface of a is fixed so as to slightly protrude from the circumferential surface of the rotating drum 9, while the rear end of the bent bimorph 23a is fixed to a support 37 that is rotated integrally with the rotating drum 9. Depending on the polarity and voltage value of the phase error voltage from the comparator 4, the tip of the bent bimorph 23a is mechanically displaced to the left or right in FIG.
a is also mechanically displaced. This is exactly the same for the rotating head 10a and the bent bimorph 23b.

Therefore, conventionally, if the rotational speed of the rotary drum 9 were to be reduced due to some disturbance while the magnetic tape 12 was running, the horizontal synchronization signal that should originally be recorded at the position 40 on the track _t3 shown in FIG. However, according to this embodiment, the rotation phase of the rotary drum 9 is Corresponding to the error, the output phase error voltage of the phase comparator 4 increases, and in response to this increase, the bent bimorph 23a or 23b:
The rotary head 10a or 10b is mechanically displaced in a direction that offsets the phase advance of the rotary drum 9.
As a result, if a horizontal synchronizing signal is to be recorded at the position indicated by the broken line 41 in FIG.
The signal is recorded at the original position shown by , and the influence of the rotational phase error caused by the disturbance is canceled out, and the horizontal synchronizing signal recording positions between each track are aligned in a certain direction with high accuracy.

When the magnetic tape 12 recorded in this manner is reproduced, crosstalk components from adjacent tracks can be reduced compared to the conventional method, and a reproduced image with a good S/N ratio can be obtained. In particular, H-order accuracy is required. This method is suitable for application to a long-time video signal recording method.

In addition, in the present invention, the bent bimorph 23
a, 23b are controlled by the rotary heads 10a, 10b.
This is done based on a signal that detects the rotational phase error of It is not necessary to use the method of sharing the four output signals, and other methods may be used. Furthermore, piezoelectric bending elements other than the bending bimorph may be used to move the rotary heads 23a and 23b in the longitudinal direction of the track, and in short, an electro-mechanical transducer may be used.

As described above, the video signal recording system of the present invention includes an electro-mechanical conversion element that mechanically displaces a rotary head in the longitudinal direction of the track recorded by the rotary head, and a rotation phase of the rotary head from a servo system. and a circuit for controlling the electro-mechanical transducer so that the horizontal synchronization signal recording positions of the video signals recorded on the tracks are aligned between the tracks by canceling out this rotational phase error using an error detection signal. The horizontal synchronizing signal recording position on the tracks of the magnetic tape can be more precisely aligned between each track, and the residual deviation (residual rotational phase error) caused by the servo system of the conventional rotating head can also be canceled out. The residual deviation of jitter components below 15 Hz can be reduced to zero, resulting in stable, high-quality images with low crosstalk and good S/N ratio even in long-duration recording and playback systems with low tape speeds. In addition, the output phase error voltage of the phase comparator used in the phase control system of the servo system of the rotating head can be shared as the signal obtained by detecting the rotational phase error of the rotating head. Therefore, it has features such as a simple circuit configuration and low cost.

[Brief explanation of the drawing]

Fig. 1 is a block system diagram showing an example of the conventional method, Fig. 2 is a block system diagram showing an embodiment of the present invention system, and Fig. 3 is an enlarged perspective view showing an embodiment of the main part of Fig. 2. , FIG. 4 is a track pattern diagram for explaining the operation of the system of the present invention. 4... Phase comparator, 5... Pickup head, 7... Disk control system, 8... Drum motor, 9... Rotating drum, 10a, 10b... Rotating head, 11a, 11b... Magnet, 13...
... Color video signal input terminal, 14 ... Low-pass filter for luminance signal separation, 15 ... Bandpass filter for carrier color signal separation, 16 ... Vertical synchronization signal separation circuit, 1
7, 19, 20... Monostable multivibrator (mono multi), 18... Pulse shaping circuit, 21...
...Flip-flop, 22...Trapezoidal waveforming circuit,
23a, 23b...bent bimorph, 34...
Conductive flexible plate, 35, 36...piezoelectric plate.

Claims (1)

[Claims] 1. A reference signal generated by a reference signal generation system from a video signal to be recorded, and a rotation detection signal extracted from a pick-up head in synchronization with the rotation of a rotating body to which a rotating head is attached. The phase of the comparison signal generated by the comparison signal generation system is compared by a phase comparator, and the output phase error signal of the phase comparator is applied to the rotation motor of the rotary body through the disc control system, thereby controlling the rotation of the rotary body. In the method of recording video signals by sequentially forming tracks inclined with respect to the longitudinal direction of the magnetic tape by the rotary head, the rotary head has a servo system that controls the phase to be synchronized with the reference signal phase. An electro-mechanical transducer for mechanically displacing the information in the longitudinal direction of the track recorded by the rotary head, and a rotational phase error detection signal of the rotary head from the servo system cancel this rotational phase error and record the data on the track. 1. A video signal recording method comprising: a circuit for controlling the electro-mechanical conversion element so that horizontal synchronizing signal recording positions of recorded video signals are aligned between tracks. 2. A patent claim characterized in that an output phase error voltage of a phase comparator used in a phase control system of a servo system of the rotary head is shared as a signal obtained by detecting a rotational phase error of the rotary head. The video signal recording method according to item 1.