JPS5849073B2 - Time axis fluctuation correction device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention enables
The present invention relates to a device for removing a certain amount of the fluctuation.

When a television signal is recorded and played back using a video tape recorder (VTR), etc., the playback signal is accompanied by time axis fluctuations, which appear as sideways and curvature in the playback image, and in the case of a color TV signal, the correct color It will not be possible to reproduce it.

Therefore, in equipment that requires high-performance playback signals, such as broadcast VTRs, it is necessary to mechanically suppress this time axis fluctuation as much as possible, and ultimately, electrically , and the residual time axis fluctuation is extremely small.

However, such equipment (J) is very expensive;
It cannot be used with a simple VTR.

Therefore, in simple VTRs, a method (heterlogin method) is generally adopted in which only the jitter of the carrier wave of the color signal is corrected without correcting the time axis fluctuation of the luminance signal.

Therefore, the color television signal output from a simple VTR is
Only the jitter in the chrominance subcarrier is corrected; the jitter in the luminance signal and the jitter in the chroma signals (I, Q) remain unremoved.

The present invention provides a composite color signal in which the jitter of the luminance signal and chromaticity signal (■, Q) is removed, rather than the signal in which only the jitter of the color subcarrier is corrected by the heterodyne method, such as this simple VTR output signal. It provides a simple means of obtaining television signals.

Before entering into the description of the present invention, let us briefly explain the recording and reproducing method of color television signals in a simple VTR.

As a method for recording color television signals using a simple VTR, there is a carrier color signal low frequency conversion method (see FIG. 1) adopted as an EIAJ standard.

In FIG. 1, a composite color video signal input to input terminal 1 is guided to LPF 2 and BPF 5, only the luminance signal is extracted by LPF 2, and FM signal is transmitted to FM modulator 3.
Let it be a modulated wave.

On the other hand, the output of BPF5, 3.5 8 MHz (N
In the case of TSC) component is heterologged with the output of the local crystal oscillator 7 in the heterologin circuit 6, and the carrier color signal converted to a low frequency is extracted at the LPFB.

The FM modulated luminance signal from which part of the lower sideband has been removed by the HPF 4 and the carrier color signal that has passed through the LPF 8 are added together by an adder 9, guided to a recording amplifier 10, and then passed through a recording/reproduction switch 11 to a magnetic signal. The head 12 records on the magnetic tape.

During reproduction, the signal that has passed through the preamplifier 13 is guided to the HPF 14 and LPF 17, and an FM luminance signal is obtained at the output of the HPF 14.

The amplitude of the output FM signal of the HPF 14 is limited by an emitter 15, and a reproduced luminance signal is obtained by an FM demodulator 16.

On the other hand, a low frequency converted carrier color signal is obtained as the output of the LPF 17, and this carrier color signal and the output of the variable frequency oscillator 23 are frequency-converted by the heterodyne circuit 18, and the carrier color is converted to a high frequency by the BPF 19. Take out the signal.

The carrier wave frequency of the output of this BPF 19 is approximately close to the color subcarrier frequency of a standard color television signal, and from this signal, a color burst signal is extracted in a burst gate circuit 20.3. 5 8 MHz reference oscillator 22
and the color burst phase are compared in a phase comparator 21, and the variable frequency oscillator 23 is controlled using this error signal.

Therefore, the color burst signal in the output signal of the BPF 19 is synchronized with the oscillation phase of the reference oscillator 22.
This means that the di-soter in the carrier wave has been removed.

The carrier color signal from which jitter has been removed in this manner and the demodulated luminance signal are added together by an adder 24, and a reproduced composite color television signal is obtained at a terminal 25.

In the reproduced color television signal of such a simple VTR, the frequency of the carrier wave of the carrier color signal is a standard frequency of 3.58 MHz without jitter, but The jitter is not corrected and remains as it is.

Here, it will be explained that in the reproduction side color circuit, only the jitter in the carrier wave is removed, but the jitter in the chromaticity signals (2) and (Q) is not removed.

The carrier color signal of the NTSC signal is ``≦jI, because it is quadrature two-phase modulated with the Q signal (f(t) represents the modulation signal)
In other words, as can be seen from equation (2), in the reproduced color television signal at terminal 25, the carrier wave jitter in the carrier color signal is removed, but the jitter in the chromaticity signals (■ and Q) is not removed at all. I understand that.

When a reproduced color television signal is received by a color television receiver, the demodulated chromaticity signals I, Q
l-! This indicates that it has jitters.

However, since the reproduced luminance signal also has the same jitter, the colors do not appear as faded on the reproduced screen, and normal color reproduction is performed.

Now, when the simple VTR reproduced color television signal obtained in this way is passed through a time base correction device (time base collector: TBC) as shown in Figure 2, jitter in the luminance signal is corrected. Along with this, the chromaticity signal■,
Jitter in Q is removed, but conversely jitter will occur in the chrominance signal carrier.

Therefore, jitter will occur in the carrier wave and burst signal.

■When a signal like the formula is input to a color television receiver, the subcarrier oscillator (
There is a problem in that the APC circuit) cannot be synchronized and normal color reproduction cannot be achieved.

Such problems occur when the brightness signal,
This problem does not occur when the chromaticity signal and the chrominance subcarrier have the same time axis fluctuation, but this problem occurs because in simple VTRs, generally only the jitter of the chrominance subcarrier is removed.

When a reproduced color television signal from such a simple VTR is passed through a TBC, the luminance signal and the carrier color signal are separated and processed by passing them through two separate TBCs.
Although it is possible to obtain a reproduced signal with jitter removed from all of the luminance signal, chromaticity signal, and chrominance subcarrier, T
There is a disadvantage that two lines of BC circuits are required, which makes them complicated and expensive.The present invention passes the reproduced color television signal of a simple VTR, from which only the jitter of such color subcarriers has been removed, through one line of TBC. This provides a novel configuration that eliminates all of the jitter.

The present invention will be explained in detail according to the specific example shown in FIG.

A reproduced composite color television signal from which only the jitter of the color subcarrier of the simple VTR has been removed is input to the terminal 25' and applied to the TBC 31 and the horizontal synchronizing signal separation circuit 33.

For example, as will be described later, this TBC 31 can write data into the memory using a clock pulse synchronized with the output signal of the variable frequency oscillator 36, and keep the signal written in the memory constant using a clock signal synchronized with the output signal of the reference oscillator 43. A method can be adopted that removes jitter by reading at a speed of .

44 is a clock control circuit.

To explain the TBC 31 in more detail, for example, as shown in FIG. , the memory 47 holds the signal written one horizontal scanning period ago, and the memory 48 is configured to read the signal written two horizontal scanning periods ago.

The clock signal for writing to the memory is a signal that is phase-locked to the reproducing horizontal synchronizing signal of the variable frequency oscillator (Fig. 3, 36), and reading from the memory is performed using, for example, a constant clock from the reference clock oscillator 43. It will be constructed.

Writing to the memory circuit and reading from the memory circuit are cyclically switched by changeover switches SW1 and SW2.

50 is a control signal generating circuit for switching the clock and switching SW1 and SW2, and 49 is a clock pulse control circuit.

As the memory circuit, a digital memory can be used by converting the video signal into digital data, or a charge transfer device such as a BBD or CCD can be used.

On the other hand, a horizontal synchronization signal is separated from the input signal of the terminal 25' by a synchronization separation circuit 33, and its phase is compared by a phase comparator 34 with a signal obtained by dividing the signal frequency of the variable frequency oscillator 136 into one by a divider 35, The variable frequency oscillator 36 is controlled by the error signal.

The signal n(fH+JfH) of the variable frequency oscillator 36 that is phase-synchronized with the reproduced horizontal synchronization signal thus generated is applied to the clock control circuit 44, and the TBC
A write clock signal of 31 is generated and further divided by a frequency divider 37 to make its center oscillation frequency equal to the standard color subcarrier frequency (fo+Jf).

However, the fH is the horizontal synchronizing signal frequency, and JfH is the jitter.

A constant frequency signal from the reference clock oscillator 43 is applied to the clock control circuit 44, and the TB
A read clock signal of C31 is generated.

Therefore, the output of the TBC 31 has some jitter removed from the luminance signal, but the chrominance signal carrier wave has the same jitter added to it as immediately after reproduction.

Further, a part of the output of the reference clock oscillator 43 is frequency-divided upward by a divide-by-one circuit 51 to obtain the standard color subcarrier frequency f.

(3.58MHz) signal.

1 The output of this frequency dividing circuit 51 is roughly converted into a signal of /2fC by the /2 frequency dividing circuit 1 circuit 40, and then the output f of the frequency dividing circuit 51 is obtained.

and the heterodyne circuit 41 generates a sum frequency signal 3/2 f
o signal is generated.

l1 Furthermore, the output of the /2 frequency divider circuit 40 is 1 minute m The sum is 3 by the output of the frequency generator 37 and the heterodyne circuit 42. Frequency signal (-Hf.

+Jf). BP from the output of TBC31
The signal (fo2+, Jf) separated by F27 is sent to the output 3 (-zf) of the heterodyne circuit 42 by the heterodyne circuit 28.

+11) and the difference frequency 1'(10'
・)''' conversion gt'L6・1 This heterodyne circuit 42
The output (/2fo) is roughly heterogeneous circuit 29
Therefore, the output of the terodyne circuit 41 (-zf.

), and the difference frequency signal (fo-fo
3(t)), and becomes a standard frequency color signal carrier wave without jitter.

The output of the heterodyne circuit 29 is added to the luminance signal output from the LPF 26 by an adder circuit 30, and outputted to an output terminal 32 as a standard frequency jitter-free composite color television signal.

According to the method of the present invention, even for color television signals reproduced by a simple VTR, there is no need to provide two TBC lines, and all jitter in the luminance signal, chromaticity signal, and carrier wave can be removed by a simple structure. You can get a color television signal.

In addition, in the present invention, P consisting of 33, 34, 35.36
Even if there is a response error in the LL circuit, this response error is canceled out by the heterodyne circuit 28, so it has no effect on the final color subcarrier.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a color television signal recording and reproducing method in a simple VTR, Fig. 2 is a block diagram of a case in which a simple VTR playback signal is connected to a time base collector, and Fig. 3 is a block diagram of a simple VTR according to the present invention. FIG. 4 is a block diagram illustrating an embodiment of a time base variation correction device for removing all jitter in a reproduced color television signal. FIG. 4 is a block diagram illustrating a time base corrector. 26...LPF, 27...BPF, 2
B, 29, 41.42... Heterogen circuit,
30... Addition circuit, 31... Time base correction device, 33... Synchronization separation circuit, 34...
...Phase comparator, 35, 37.40... Frequency divider, 36... Town variable oscillator, 44... Clock control circuit.

Claims (1)

[Claims] 1. A variable delay means to which a reproduced composite color television signal reproduced through a recording and reproducing apparatus and from which only the time axis variation of the color subcarrier has been removed is applied, and a horizontal delay in the reproduced composite color television signal. a phase synchronization signal generating means for creating a first continuous signal phase-synchronized with the synchronization signal; and a time axis fluctuation component of the luminance signal in the reproduced composite color television signal according to the frequency of the first continuous signal. first means for controlling the delay time of said variable delay means to eliminate the delay time; and second means for frequency-dividing said first continuous signal to produce a second continuous signal having a frequency substantially equal to the color subcarrier frequency. 2
a third means for heterologining the second continuous signal and the first stable local oscillation signal to obtain a third continuous signal; and a fifth means for heterodyning the separated carrier color signal and the third continuous signal to remove some time axis fluctuations in the carrier color signal. , a sixth means for heterodyning the carrier color signal from which a certain amount of the time axis variation has been removed by a second stable local oscillation signal to obtain a carrier color signal at a standard subcarrier frequency; and an output of the sixth means. and a seventh means for adding the luminance signal separated by the fourth means to obtain a composite color television signal from which a certain amount of time-axis variation has been removed.