JPH0227745B2 - - 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 controlling the drive of the magnetic tape accordingly, it is possible to record horizontal synchronization signals recorded on each track with a simple configuration so that they are aligned with high precision between each track, resulting in less crosstalk and excellent stability of S/N. The purpose of the present invention is to provide a recording method capable of obtaining high-quality images.

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 row.

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 rotating heads 10a and 10b, which rotate integrally with a rotating drum 9, which will be described later, and have, for example, different azimuth angles. do.
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 vertical synchronizing signal.
A 30Hz symmetrical square wave and a reference signal are generated 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 by 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 supplied to the phase comparator 4, 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 23, which is attached to the magnetic tape 23 and 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 23. 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 serious problems in terms of tape speed, track width, etc. in conventional magnetic recording and reproducing devices such as VTRs, and crosstalk from adjacent tracks can usually be adequately dealt with by 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 embodiments thereof will be described below with reference to FIGS. 2 to 5.

Figure 2 shows the first video signal recording method according to the present invention.
A block system diagram of an example is shown. 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 12 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.

As before, the phase comparator 4 generates a comparison signal generation system 6.
The voltage change value is sampled and held by the reference signal from the reference signal generation system 3 due to the phase change of the slope part of the trapezoidal wave, and the held phase error voltage is applied to the disk drive control system 7. The error voltage is supplied to phase modulator 13.

On the other hand, the gear 15 installed on the capstan 14
A rotation detection signal having a frequency proportional to the rotation speed of the capstan 14 detected by the frequency generator 16 is divided into a frequency of 1/n by the frequency divider 17 and then supplied to the phase modulator 13 . This frequency divider 17 is connected to the rotating heads 10a and 10b.
This is to obtain a movable amount that can compensate for the deviation of the horizontal synchronizing signal from the fixed position due to rotational phase error. Therefore, the frequency of the rotation detection signal (=
1/T _k ) is sufficiently low, that is, if the frequency satisfies the following condition: magnetic tape phase amount Tg (ms)≦T _k (ms) (1), the frequency divider 17 is unnecessary.

The phase modulator 13 rises in response to the frequency-divided rotation detection signal from the frequency divider 17 as shown in FIG. 4A, and falls as the pulse width changes depending on the phase error voltage from the phase comparator 4 shown in FIG. Outputs waveform pulses. 4C shows the output waveform of the monostable multivibrator in the phase modulator 13, and FIG. 4D shows the output signal waveform of the phase modulator 13. A signal using the falling edge of the rectangular wave shown in FIG. 4C, as shown in FIG. Here, the frequency is multiplied by N and restored to the frequency before division by the frequency divider 17, and then converted into a trapezoidal wave by a trapezoidal wave forming circuit (not shown) and supplied to the phase comparator 19 as a comparison signal.

The phase comparator 19 uses the reference signal from the reference signal generation circuit 20 as a sampling pulse to output the PLL 18.
The slope portion of the trapezoidal wave is sampled and held, a phase error voltage corresponding to the phase difference between both signals is outputted, and this is supplied to the disc control system 21. As a result, the disc control system 21 keeps the rotational speed of the capstan motor 22 at a predetermined constant speed at all times, and at the same time controls the rotational phase of the capstan motor 22 according to the phase error voltage from the phase comparator 19. Therefore, the magnetic tape 23 that is run by the capstan motor 22 is further driven by an amount (on the magnetic tape 34) corresponding to the rotational phase error of the rotary heads 10a, 10b in a direction that cancels out this rotational phase error. It will be.

Therefore, in the track pattern on the magnetic tape 23 shown in FIG. 3, the horizontal synchronization signal that should originally be recorded at the position indicated by the solid line 27 on track _t3 is
If recording is to be performed at the position indicated by the broken line 26 in the figure, where the phase is delayed by the rotational phase error of the rotating drum 9 and the rotating heads 10a, 10b, advance the rotational phase of the capstan motor 22. The amount of movement of the magnetic tape 23 is made greater than that in the steady state, and the horizontal synchronizing signal is recorded at the original position shown by the solid line 27 in FIG. That is, the rotational phase error A (sec) of the rotating head 10a or 10b between the two positions shown as c and d in FIG. ) has the relationship shown in the following equation.

B=TgV _D /V _T・A=K・A ...(2) However, in equation (2), V _D is the peripheral speed of the rotating drum 9 (unit: m/s), and V _T is the tape speed (unit: m/s).
s), K is V _D /V _T .

Incidentally, at the time point indicated by d in FIG. 3, the output phase error voltage of the phase comparator 4 becomes a voltage value decreased from the voltage value E up to that point as shown in FIG. The output signal of is shown in Figure 4D.
As shown by A', the period becomes longer corresponding to A in equation (2). For this reason, the capstan servo system judges as if the rotation of the capstan 14 has become slower than the normal speed, and the capstan servo system
In order to cancel B in equation (2), the running speed of the magnetic tape 23 is increased, so that the horizontal synchronizing signal is recorded not at the position of the broken line 26d but at the position of the solid line 27c where it should be recorded.

In FIG. 3, t ₁ , t ₂ , and t ₃ are tracks on which one field of video signals that have passed through the video signal recording system 2 are each recorded, and 24 is a rotary head 10 a or 10 b that is scanned in the direction of arrow 25 . The solid line portions of one of the rotary heads and each track t ₁ , t ₂ , t ₃ indicate the recording position of the horizontal synchronizing signal.

In this way, the rotational phase error of the rotary drum 9, that is, the rotary heads 10a and 10b, caused by the disturbance is removed by the capstan servo system by a distance corresponding to the rotational phase error distance on the magnetic tape.
Since the horizontal synchronizing signal recording positions between the tracks on the magnetic tape 23 are aligned in a fixed direction, highly accurate H alignment can be achieved. Magnetic tape 23 recorded in this way
When playing back images, crosstalk components from adjacent tracks can be reduced compared to the conventional
It is possible to obtain a good N value, and is particularly suitable for application to a long-term video signal recording system that requires H alignment accuracy.

Next, a second embodiment and a third embodiment of the system of the present invention will be described with reference to a block system diagram of the system of the present invention shown in FIG. However, in FIG. 5, the same components as those in FIG. 2 are given the same reference numerals, and their explanations will be omitted.

In the second and third embodiments, a variable delay circuit is used to prevent the rotary head 10 from being sufficiently offset in the first embodiment.
It is also possible to cancel out relatively short period rotational phase errors of a and 10b. That is, first, to explain the second embodiment, in FIG. 5, a color video signal inputted from an input terminal 12 is passed through a variable delay circuit 2 composed of, for example, a charge coupled device (CCD).
8.

On the other hand, the output phase error voltage of the phase comparator 4 is applied as a control voltage to a voltage controlled oscillator (VCO) 29 to control its output oscillation frequency. VCO2
The output oscillation frequency of the rotary drum 9, that is, the rotary heads 10a, 10b, changes in accordance with the rotational phase error of the rotary drum 9, that is, the rotary heads 10a, 10b. Variable control is performed to cancel the rotational phase error. In this manner, the input color video signal is supplied to the video signal recording system 2 after being delayed by the variable delay circuit 28 in accordance with the rotational phase error of the rotary heads 10a, 10b.

According to the second embodiment of the present invention, when the rotation speed of the rotary drum 9 decreases due to a disturbance, for example, the output phase error voltage of the phase comparator 4 is A clock pulse with a frequency that increases and decreases in inverse proportion to this increase is provided to a variable delay circuit 28;
The delay time is increased by making the transfer time of the variable delay circuit 28 composed of a CCD longer than that in a steady state. For this reason, the input color video signal is delayed by a length of time corresponding to the rotational phase error of the rotary heads 10a, 10b. Furthermore, when the rotational speed of the rotating drum 9 increases, the delay time becomes shorter than in the steady state. In this way, according to the second embodiment, control of the delay time using the variable delay circuit 28 is added to the drive control of the magnetic tape 23 by the control of the capstan servo system of the first embodiment. Therefore, H arrangement can be performed with higher accuracy.

Next, a third embodiment of the method of the present invention will be explained. In this embodiment, blocks 2 and 28 are
and blocks 31 to 42 shown with dashed lines instead of 30.
It has been established. That is, a color video signal input from the input terminal 12 is supplied to a band filter 31 and a low pass filter 37, respectively, and a carrier color signal and a luminance signal are separated. The carrier color signal taken out from the band filter 31 is sent to the color signal processing circuit 3.
2, the level of which is automatically controlled to a constant level, and then frequency-converted to a lower frequency range than the frequency-modulated luminance signal described later, and in one field period, the phase is 90° for one horizontal scan. The phase is advanced for each period, and in the next field period, the phase is delayed by 90 degrees for each horizontal scanning period, which is alternately performed for each field. The output low-pass conversion carrier color signal (the phase has also been shifted) of the color signal processing circuit 32 is delayed for a predetermined time by a variable delay circuit 33 as will be described later, and then supplied to the mixer 41 via a low-pass filter 36. .

On the other hand, the luminance signal taken out from the low-pass filter 37 is delayed by a variable delay circuit 38 for a predetermined period of time as described later, and then supplied to a luminance signal processing circuit 39, where it performs pedestal level clamping, pre-emphasis, white level and dark After level clipping, etc., it is frequency modulated.
The frequency modulated luminance signal taken out from the luminance signal processing circuit 39 is supplied to a mixer 41 after its low frequency components are removed by a high frequency filter 40 so that the band does not overlap with the low frequency conversion carrier color signal. The signal is frequency division multiplexed with the low-pass converted carrier color signal. The frequency division multiplexed signal taken out from this mixer 41 passes through a recording amplifier (not shown) and is sent to a rotating head 10 having different azimuth angles.
A and 10b alternately form one track for each field and are sequentially recorded.

On the other hand, a signal whose frequency changes corresponding to the rotational phase error of the rotary heads 10a and 10b taken out from the VCO 29 is sent to the clock pulse generation circuit 34.
It is supplied to the variable delay circuit 38 through which the delay time is variably controlled according to the rotational phase error, and is supplied to the frequency divider 35, where the frequency is set to 1/
After being frequency-divided into n (n is an integer), it is supplied to the variable delay circuit 33 via the clock pulse generation circuit 42.
The delay time is variably controlled according to the rotational phase error.

Here, the variable delay circuits 33 and 38 are composed of CCDs, for example, and if the number of stages of the variable delay circuit 38 is X stages, the number of stages of the variable delay circuit 33 is X/n stages. The reason why the number of stages is made different in this way is to take into consideration the difference in bandwidth between the luminance signal and the low frequency conversion carrier chrominance signal and the cost, and the bandwidth of the variable delay circuit 38 is the same as that of the variable delay circuit 28. A bandwidth of about 1/2 is sufficient. Also, variable delay circuit 3
The number of stages of 3 is because the input signal is a low frequency conversion carrier chrominance signal with a narrower bandwidth than the luminance signal, so it is not necessary to use the same variable delay circuit as the variable delay circuit 38, and an inexpensive X/n stage is used. It has been confirmed that the bandwidth is about 1/5 of that of the variable delay circuit 38. However, variable delay circuits 33 and 3
Since the delay times of the clock pulses 8 and 8 must be the same, the clock pulse frequency of the variable delay circuit 33 is set to 1/n of the clock pulse frequency of the variable delay circuit 38.

In this way, the luminance signal and the low frequency conversion carrier color signal are each delayed in response to the rotational phase error of the rotating drum 9 so that the error becomes zero, and then the luminance signal is frequency modulated. Both are frequency-division multiplexed and recorded on the magnetic tape 23 in H-alignment with high precision.

In this embodiment, the luminance signal and the low frequency conversion carrier chrominance signal are delayed by dedicated variable delay circuits 38 and 33, respectively, so H alignment can be performed with higher precision than in the second embodiment. can.

The variable delay circuits in the second and third embodiments described above are used to cancel relatively short-period rotational phase errors of the rotary heads 10a and 10b; Since the rotational phase error of the magnetic tape 23 is controlled by driving the magnetic tape 23, the effect is greater than that obtained when each is used alone, and H alignment with extremely high precision can be achieved. be able to. Furthermore, if all rotational phase errors were to be canceled out using a variable delay circuit, it would be necessary to configure a configuration such as cascading several stages of CCDs in order to obtain the necessary amount of control phase, which would increase costs and degrade performance. causing a disadvantage. However, since the variable delay circuits 28, 33, and 38 of the second and third embodiments are used for the above-mentioned purpose, the amount of control phase required is small, and there is no such disadvantage.

Note that in each of the above embodiments, the variable delay circuit 2
8, 33, and 38 are constructed using a CCD, but it goes without saying that they may be constructed using a charge transfer element such as a bucket brigade device (BBD) or other variable delay element having a similar function. .

As described above, the video signal recording method according to the present invention includes a reference signal generating means that outputs a first reference signal based on a synchronization signal obtained separately from a video signal to be recorded, and a comparison signal generating means for outputting a synchronized comparison signal; and a first for comparing the phases of the first reference signal and the comparison signal and outputting a first phase error signal corresponding to an error in the rotational phase of the rotary drum. a phase comparison means for controlling the rotational speed of a drum motor that rotates the rotating drum to a constant value, and adjusting the rotational speed of the drum so that the rotational phase of the rotating drum coincides with the first reference signal based on the first phase error signal; a rotating drum servo system having a first control means for controlling the rotation speed of the motor; and a phase modulation signal obtained by phase modulating a rotation detection signal proportional to the rotation speed of the capstan using the first phase error signal. a second phase modulation means for outputting a second phase error signal according to a phase difference between a second reference signal and the phase modulation signal;
and a second control means for controlling the rotational speed of the capstan motor for rotating the capstan to a constant value and controlling the rotational phase of the capstan motor in accordance with the second phase error signal. Since the magnetic tape is equipped with a capstan servo system having Even with the recording and reproducing method, it is possible to obtain stable, high-quality images with little crosstalk and a good S/N ratio.In addition, the reproduced signal from the previously recorded track can be used as a comparison signal to obtain the phase error signal. Since it is not used, there is no need for a reproducing head for it, and as a signal obtained by detecting the rotational phase error of the rotary head,
Since the first phase error signal of the first phase comparison means used in the phase control system of the servo system of the rotary head is shared, the circuit configuration can be made simple and low-cost, and the variable delay means for delaying a video signal to be recorded that is supplied to the rotary head; and a variable delay means for varying the delay time of the variable delay means in accordance with the first phase error signal so as to cancel the rotational phase error of the rotary head. Since the rotational phase error having a relatively long period can be canceled by the capstan servo system, and the rotational phase error having a relatively short period can be canceled by the variable delay means. Since it can be offset by varying the time, it has the advantage of being able to record H-line video signals with extremely high precision.

[Brief explanation of drawings]

Fig. 1 is a block system diagram showing an example of the conventional system, Fig. 2 is a block system diagram showing the first embodiment of the system of the present invention, Fig. 3 is a track pattern diagram explaining the operation of the system of the present invention, and Fig. 4A. ~D are signal waveform diagrams for explaining the operation of FIG. 2, respectively, and FIG.
FIG. 7 is a block system diagram showing an embodiment and a third embodiment. 3...Reference signal generation system (reference signal generation means),
4... Phase comparator (first phase comparison means), 6...
...Comparison signal generation system (comparison signal generation means), 7...
Discrete control system (first control means), 8...Drum motor, 9...Rotating drum, 10a, 10b
... Rotating head, 12 ... Color video signal input terminal, 13 ... Phase modulator (phase modulation means), 14
... Capstan, 19 ... Phase comparator (second phase comparison means), 21 ... Discrete control system (second control means), 22 ... Capstan motor,
23...magnetic tape, 28, 33, 38...variable delay circuit (variable delay means), 29...voltage controlled oscillator, VCO (variable control means), _t1 to _t3 ...track.

Claims (1)

[Scope of Claims] 1. A video signal recording method in which a rotating head sequentially forms tracks inclined with respect to the longitudinal direction of a magnetic tape to record a video signal, which is separated from the video signal to be recorded. a reference signal generating means for outputting a first reference signal based on the obtained synchronization signal; a comparison signal generating means for outputting a comparison signal synchronized with the rotational phase of the rotating drum;
a first phase comparison means for comparing the phases of the reference signal and the comparison signal and outputting a first phase error signal corresponding to an error in the rotational phase of the rotary drum; and rotation of a drum motor for rotating the rotary drum. a first control means for controlling the rotational speed of the drum motor to a constant speed and controlling the rotational speed of the drum motor so that the rotational phase of the rotating drum matches the first reference signal using the first phase error signal; a drum servo system; a phase modulation means for outputting a phase modulation signal obtained by phase modulating a rotation detection signal proportional to the rotation speed of the capstan using the first phase error signal; a second reference signal and the phase modulation signal; a second phase comparison means for outputting a second phase error signal according to a phase difference with the signal; and a second phase comparison means for controlling a rotational speed of a capstan motor that rotates the capstan to be constant, and outputting the second phase error signal. and a capstan servo system having a second control means for controlling the rotational phase of the capstan motor according to the method. 2. A video signal recording method in which video signals are recorded by sequentially forming tracks inclined with respect to the longitudinal direction of a magnetic tape using a rotating head, and is based on a synchronization signal obtained separately from the video signal to be recorded. a reference signal generating means for outputting a first reference signal; a comparison signal generating means for outputting a comparison signal synchronized with the rotational phase of the rotating drum;
a first phase comparison means for comparing the phases of the reference signal and the comparison signal and outputting a first phase error signal corresponding to an error in the rotational phase of the rotary drum; and rotation of a drum motor for rotating the rotary drum. a first control means for controlling the rotational speed of the drum motor to a constant speed and controlling the rotational speed of the drum motor so that the rotational phase of the rotating drum matches the first reference signal using the first phase error signal; a drum servo system; a variable delay means for delaying a video signal to be recorded that is supplied to the rotary head; and a variable delay means for delaying the video signal to be recorded, which is supplied to the rotary head, in accordance with the first phase error signal so as to cancel a rotational phase error of the rotary head. variable control means for varying the delay time of the means; phase modulation means for outputting a phase modulation signal obtained by phase modulating a rotation detection signal proportional to the rotational speed of the capstan with the first phase error signal; a second phase comparison means for outputting a second phase error signal according to a phase difference between the reference signal of the reference signal and the phase modulation signal; and a capstan servo system having a second control means for controlling the rotational phase of the capstan motor in accordance with the second phase error signal.