JPH023594B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a video signal recording and reproducing device, which separates a luminance signal track and a color signal track and records them on a recording medium in order to obtain a high-quality reproduced image.
The purpose is to automatically correct the time difference between the luminance signal and color signal during playback, and to obtain a high-quality image.

At present, magnetic recording and reproducing devices (hereinafter referred to as VTR)
The mainstream is the helical scan type, in which a rotating head forms an image track diagonally on the tape. In particular, home VTRs are smaller and have higher density. For example, in a VHS system VTR, two video heads arranged at an index angle of 180 degrees to each other on a rotating cylinder with a diameter of 62 mm transmit video signals in a 1/2-inch width. is recorded diagonally to the tape. In addition, for broadcasting VTRs, we also use portable news coverage (BNG)
There is a strong demand for smaller and lighter VTRs, and 3/4-inch U-standard VTRs are now widely available. For ENG
VTRs are required to be small and lightweight, as well as to have high image quality because they are used for broadcasting, and a search function is also important to make editing easier.
3/4 inch U standard VTR has a cylinder diameter of 110 mm.
Since the tape width is 3/4 inch, there is a limit to miniaturization, and as a recording method for video signals, the luminance signal is made into a frequency modulated wave and its reduction is removed.
Since a method of superimposing a frequency-converted carrier chrominance signal on a low frequency band is used, the bands of the luminance signal and chrominance signal are limited, and the image quality is not necessarily sufficient for broadcasting.

However, since the luminance signal and the chrominance signal are recorded and reproduced simultaneously on the same track, the time difference between the luminance signal and the chrominance signal is only a certain time difference that occurs in the circuit processing system.
It does not change depending on the conditions during playback. Fixed delay lines can therefore be used to compensate for time differences.

Next, the present invention will be explained. Fig. 1 is a plan view of the head arrangement on the cylinder, Fig. 2 is a front view of the head, Fig. 3 is a block diagram of an embodiment of this system VTR, and Fig. 4 shows the recording signal in Fig. 3. A spectrum diagram is shown. FIG. 5 is a waveform diagram of the time reference signal inserted in recording according to the present invention, FIG. 6 is a block diagram of the entire device, FIG. 7 is a waveform diagram of separating the time reference signal from the reproduced luminance signal, and FIG. An explanatory diagram of the edge after the time reference signal, FIG. 9 is a waveform diagram for creating a time difference signal, FIG. 10 is an explanatory diagram of the +/− discrimination circuit, FIG. 11 is an explanatory diagram of the counter circuit, and FIG.
13 is a diagram illustrating the operation of the tap delay line, and FIG. 14 is a diagram illustrating signal passage through the tap delay line.

In FIGS. 1 and 2, A, A' and B, B' represent two sets of heads arranged at the same height and at an index angle of 180 DEG on the circumference of the cylinder.
As a method for recording and reproducing color video signals, there is a method of recording and reproducing a frequency-modulated luminance signal in the A and A' heads, and a frequency-modulated color signal in the B and B' heads, respectively. In this way, the track width of the luminance signal can be increased, and since the color signal is not superimposed, the band can be widened, and a reproduced image with high S/N and high resolution can be obtained. Further, since the baseband signals (for example, I signal and Q signal) can be frequency-modulated and recorded as color signals, it is possible to obtain a reproduced signal with a high S/N in a high band.

The configuration of the recording and reproducing apparatus will be explained in detail below with reference to FIGS. 3 and 4.

1 is a luminance signal input terminal, 2 is an I signal input terminal,
3 is a Q signal input terminal, 4, 5, 6 are frequency modulators, 7 is a bandpass filter, 8 is a low-pass filter, 9 is an adder,
10 and 11 are recording amplifiers, 12 and 13 are video heads, 14 and 15 are regenerative amplifiers, 16 is a bandpass filter, 17 is a low-pass filter, 18, 19, and 20 are frequency demodulators, and 21 is a luminance signal. Output terminals 22 are I signal output terminals, and 23 are Q signal output terminals. In addition, Fig. 4A shows the recorded spectrum of the luminance signal,
FIG. 4B shows the recording spectrum of the color signal, where 26 is the I signal and 27 is the Q signal.

The luminance signal applied to the luminance signal input terminal 1 is
After being modulated by a frequency modulator 4 and amplified by a recording amplifier 10, it is recorded on a tape by a head 12. The luminance signal has a band of approximately 4 MHz, and in order to record and reproduce this signal with good performance, the frequency shift of modulation is set, for example, from 4.4 MHz to 6 MHz.
The recorded signal frequency spectrum is as shown in FIG. 4A. The I signal applied to the I signal input terminal 2 is modulated by a frequency modulator 5, band-limited by a bandpass filter 7 to about 3 MHz to 8 MHz, and guided to an adder 9. Further, the Q signal applied to the Q signal input terminal 3 is modulated by a frequency modulator 6, band-limited to about 2 MHz by a low-pass filter 8, and guided to an adder 9. The bandpass filter 7 and the lowpass filter 8 function to limit the band so that the spectra of the frequency modulated waves of the I signal and the Q signal do not overlap. Both signals added by adder 9 are amplified by recording amplifier 11 and then recorded on tape by head 13.
The I signal is approximately 1.5MHz, and the Q signal is 0.5MHz.
For example, for the I signal, the frequency deviation is 5 MHz to 6 MHz, and the band is approximately 3 MHz to 6 MHz.
8MHz and the frequency deviation for the Q signal.
If the frequency is 0.75MHz to 1.25MHz and the bandwidth is up to about 2MHz, a sufficient bandwidth and S/N can be obtained. Almost sufficient image quality can be obtained even if the I signal band is set to about 1 MHz. The recorded spectrum of this color signal is as shown in FIG. 4B. In this way, the luminance signal and the chrominance signal are recorded by a pair of heads having the above-described structure.

During reproduction, the luminance signal reproduced from the head 12 is amplified by a regenerative amplifier 14, guided to a frequency demodulator 18 and demodulated, and a reproduced luminance signal is obtained at an output terminal 21. On the other hand, the color signal reproduced from the head 13 is amplified by a regenerative amplifier 15 and guided to a bandpass filter 16 and a low-pass filter 17. Only the I signal is extracted by the bandpass filter 16, and only the Q signal is extracted by the low-pass filter 17, which are demodulated by the frequency demodulators 19 and 20, respectively, and the reproduced I signal is output to the I signal output terminal 22, and the Q signal is output. A reproduced Q signal is obtained at terminal 23.

The present invention is characterized in that, as mentioned above, the time axis fluctuations between the independent luminance signal head and the chrominance signal head differ accordingly depending on the state during playback, and also in the installation process when the video head is attached to the video head drum. For example, if the error is 3 microns, the time difference between the luminance signal and color signal during compatible playback will be about 500 ns. Due to these reasons, we propose a time axis corrector between the luminance signal and the color signal.

Next, a detailed explanation will be provided. FIG. 5 is a waveform diagram of a time reference signal synthesized with the I signal during recording. FIG. 6 is a block diagram of the time axis corrector. FIG. 7 shows waveform diagrams of each part.

First, we will explain the recording process. Regarding the luminance signal waveform during recording, reference numeral 28 in FIG. 5 shows a waveform near the vertical synchronization signal of the luminance signal. Next, the I signal waveform is shown at 30, and there is no signal during the vertical blanking period. Here, a time reference signal synchronized with the synchronization signal in the luminance signal is added above the no-signal level as shown in FIG. 5, 29. Regarding the addition position of this reference signal 29, this time base corrector switches the comparison and tap type delay lines within the vertical blanking period in order to eliminate large time base fluctuations for each television field (hereinafter referred to as TV). This is because Note that in a small VTR or the like, the time that one video head is responsible for recording and reproducing is one field, so it is better to synthesize the reference signal during this initial vertical blanking period. However, since the head switching position is 3 to 4 horizontal periods before the vertical blanking, if it is too close, it will be difficult to extract during reproduction due to the effects of switching transients, etc. Further, the reason why the reference signal is intentionally added to the upper side is because there is little moiré component between the I signal and the Q signal. Note that the synchronization signal is used as the reference signal for the luminance signal track. this is,
When dubbing to a TV display or other VTR,
Furthermore, when a signal is sent to a broadcasting corrector, the presence of an unrelated signal in the luminance signal will make normal operation unstable.

As described above, the signal obtained by adding the time reference signal to the I signal is applied to input terminal 2 in FIG. recorded on tape. As explained with reference to FIG. 3, the reproduced signals are reproduced to the reproduction output terminals 21, 22, and 23, respectively, and have the same waveform as at the time of recording. Then, a luminance signal is input to the input terminal 31 of the time axis corrector as shown in FIG. 6, a Q signal is input to 32, and an I signal is input to 33.

Next, FIG. 6 will be explained. 34 is a fixed delay line for the luminance signal, 35 is a time reference signal extraction circuit, 36
37 is a measurement circuit that counts and measures the signal width of the compared difference; 38 is a reference frequency oscillator for measuring the time width; 39 is a decoder circuit that converts the counted value into an analog value for delay line switching, and 40 and 41 are tap type switching delay line circuits for Q and I signals.

The operation will be explained with reference to FIG. First, the luminance signal is branched from the input terminal 31 to the fixed delay line circuit 34 and the time reference signal extraction circuit 35. The fixed delay line circuit 34 requires a delay line that delays half the time of the time axis correction range. For example +500ns,
-500ns to correct a total of 1000ns
delay line is required. The output of this circuit 34 is then led to an output terminal 42. On the other hand, the time reference signal extraction circuit 35 separates only the synchronization signal component. After that, the vertical synchronizing signal is taken out using an integrating circuit as shown in Fig. 7, 46, and the monostable multi for removing the trailing edge edge equalization pulse is operated to obtain the waveform shown in Fig. 7, 47, and then the reference signal is A monostable multi is operated in synchronization with the trailing edge of 47 to obtain a waveform 48, and a reference signal 49 is obtained by applying a gate to the synchronization signal separated from the luminance signal. On the other hand, the I signal also enters the time reference signal extraction circuit 35 from the input terminal 33, and the time reference signal is separated by the waveform 48 in FIG.

The time reference signals of the luminance signal and the color signal are obtained in the above manner. In Fig. 7, three synchronization signals are used as the reference signal, but when comparison cannot be made with one reference signal due to dropout etc.
This is because a later reference signal is used.

Next, a reference signal such as 50 in Figure 8 was obtained, but the minimum information necessary for a comparison signal between a luminance signal and a chrominance signal is either the leading edge or the trailing edge of the reference signal, and the rising and falling edges. Having well-sharp characteristics is a method for reducing measurement time errors. This is the waveform obtained when the time reference signal is added to the upper side of the I signal as shown at 50 in FIG. It is well known that in order to improve the signal-to-noise ratio, the level of the signal is increased to a maximum value of 50% of the upper signal level, and if emphasis is applied before modulation, a waveform like 51 is obtained. In this state, the emphasized edge component becomes too large,
It causes various problems when passing through the head tape system. Therefore, it is necessary to keep the clip within a range that does not cause problems. For example, convert the signal component to 100
If we assume that the clip is multiplied by 200%, the leading edge will only have a 50% margin after emphasis and will be clipped. However, since the trailing edge is 100%, it is not clipped.
During playback, sharp edges can be reproduced when de-emphasized after demodulation. Therefore, time axis errors resulting from the rise and fall characteristics of the waveform are reduced. The above can also be demonstrated for luminance signals. Therefore, the trailing edge of the reference signal is used for the comparison circuit. Next, comparator 36
When the waveform 52 in FIG. 9 is obtained by differentiating the reference signal of the luminance signal and only the trailing edge is obtained, and the waveform 53 of only the trailing edge of the reference signal of the chrominance signal is obtained, and there is a time axis fluctuation by ΔT, Flip-flops are operated at both edges to create a waveform like 54. This is extremely narrow, making flip-flop operations difficult, but recently, high-frequency IC technology has advanced.
If you use an ECL IC or the like, you can create a pulse with a width of 10 ns.

On the other hand, another method is to operate a flip-flop on the first edge and the next edge of the luminance signal to create a waveform 55, and create a chrominance signal waveform 56 in the same way and pass it through an AND circuit. , a waveform like 57 of the difference is obtained. The comparator 36 also determines whether the color signal is ahead or behind the luminance signal and transmits the information to the decoder circuit 39. This is the reference signal of the luminance signal, the waveform of which is shown in Figure 9, 52, and the monostable multi first
60 is operated, and the operating time width is set slightly wider than the correction range. Then, a reference signal 53 of the color signal is inputted from a terminal 59 and passed through a gate circuit 61, and a discrimination circuit 62 detects whether or not there is a color reference signal.
It leads to the output terminal 81. This signal is the decoder circuit 3
Enter 9.

Next, the reference frequency oscillator 38 will be described. In a normal VTR, the time difference between the luminance signal and the chrominance signal is
It is about 30ns. This time difference is not very noticeable because it is fixed, but with a VTR like this method,
When time-correcting the luminance signal and color signal for each field, if the detection limit level is made rough, such as at 100ns intervals, color flicker will become noticeable, so it is not suitable for broadcasting.
We decided to absorb up to a width of 10 ns, which is about the same as a VTR. In this way, color flicker cannot be tracked due to the integral effect of the eye, and good image quality can be obtained. Therefore, in order to detect up to a width of 10 ns, the reference frequency must be
I chose 100MHz. The signal oscillated by the oscillator 38 is guided to the counter circuit 37.

Next, the counter 37 receives the time difference signal from the comparator 36 and turns it on and off. The reference frequency is counted only during times when there is a difference signal. For example, two counters are used here: one that counts between 0 and 90 ns at 10 ns intervals, and one that counts between 0 and 900 ns.
It has a counter that counts at 100ns intervals. This allows time axis correction from +1000ns to -1000ns. Figure 11 82 shows the counter
ON and OFF signals are input, and a reference frequency of 100 MHz is input from the terminal 83, and the decade counter 84 operates. Here, it counts at 10ns intervals and leads the count output to the output terminal 86 with a BCD code.
On the other hand, one output per 10 counts is obtained from the terminal terminal 88, and the next stage decade counter 85
, counts every 100 ns, and is led to an output terminal 87.

Since the output from the counter circuit 37 is a BCD code, the decoder circuit 39 converts it into a decimal code. After that, it enters the tap-type delay line drive circuit and performs switching using the +/- discrimination signal so that the tap-type delay line as shown in FIG. 12 can be driven. For example, when the chrominance signal is reproduced in a phase that is ahead of the luminance signal as shown in FIG. 13, the luminance signal circuit includes a fixed delay line 34, and the chrominance signal system also includes a fixed delay line 101. . Then, the color signal enters the color signal input terminal 98, and after delaying the 10ns delay line to the value measured by the counter,
It is switched to the counter value measured for 100 ns by the 100 ns delay line, passes through the fixed delay line, and when output, it has the same time value as the luminance signal.

On the other hand, if the chrominance signal lags behind the luminance signal, as shown in the lower part of Figure 13, the chrominance signal is input from the input terminal 102, and the measured value and the actual delay amount are inversely related to each other through the 10ns delay line. It won't happen. After switching, it enters a 100ns delay line and performs the same operation, but does not include a fixed delay line at its output. In this case, if the total delay amount of the fixed delay line 101 and the 100 ns tap type delay line on one side is the same, then
The circuit configuration when the 10ns delay line 108 is shared by switching the switching connections when the chrominance signal is in both leading and lagging phases, and the 100ns delay lines 109 and 110 are considered as one unit, is shown in FIG. It becomes like this. The switching signals created in the above manner are shown in Figure 12, 92 and 97, respectively.
10ns tap delay line switching signal, 100ns
A tap-type delay line switching signal is input, a color signal is input through an input terminal 89, the signal passes through the 10ns tap-type delay line, and a delayed color signal is output to each tap every 10ns and input to the switching circuit 91. On the other hand, the color signal is switched by the switching signal from 92,
Its output goes into a 100ns delay line. The output delayed by each tap enters a switching circuit 95, is switched by a switching signal, and is led to an output terminal 96.

When performing time axis correction between such two signals, it is easily possible to compare them at horizontal synchronization intervals and use an element such as a CCD for correction.

According to the present invention, a high quality image can be obtained because the luminance signal and color signal are recorded in separate heads, and furthermore,
Delay time errors caused by installation errors of the luminance signal head and color signal head can be automatically and accurately removed, thereby improving image quality. In particular, such a function is very effective in applications where dubbing is essential, such as in broadcasting stations.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention; FIG. 1 is a plan view showing the arrangement of heads on a head cylinder, FIG. 2 is a front view of the main parts, and FIG. 4 is a diagram showing the recording spectrum, FIG. 5 is a diagram showing an example of the reference signal, FIG. 6 is a block diagram of the main part of the present invention, and FIG. 7 is a diagram showing the reference signal from the luminance signal. FIG. 8 is a waveform diagram of the reference signal, FIG. 9 is a waveform diagram for creating a time difference signal, and FIG.
- An explanatory diagram of the discrimination circuit, Fig. 11 is an explanatory diagram of the counter circuit, Fig. 12 is a configuration diagram of the tap type delay line,
Fig. 13 is an explanatory diagram of the operation of the tap type delay line, Fig. 14
The figure is an explanatory diagram of signal passage through a tap-type delay line. 31, 32, 33...Input terminal, 34...Fixed delay line, 35...Time reference signal extractor, 36...Comparator,
37... Counter, 38... Oscillator, 39... Decoder, 40, 41... Tap type delay line.

Claims (1)

[Scope of Claims] 1. means for recording a luminance signal including a first reference signal with a constant period on a recording medium by a first head;
means for recording a color signal including a second reference signal phase-synchronized with the first reference signal on the recording medium by a second head; , second
a counter for counting the phase difference between the two signals based on the output signal of a fixed reference oscillator; 1. A video signal recording and reproducing apparatus, comprising a delay means for correcting a time difference between both reproduced signals by delaying at least one of the reproduced signals. 2. The counter and the delay means each have a coarse one and a fine one, and the output of the coarse counter controls the coarse delay means, and the output of the fine counter controls the fine delay means. The video signal recording and reproducing device according to item 1. 3. The video signal according to claim 1, wherein the first head and the second head are arranged on the same rotation but at different heights in the direction of the rotation axis. recording and reproducing equipment.