JPS6359594B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a carrier color signal separation circuit.

A comb filter is generally used to separate the carrier color signal from the color video signal, but the separation circuit using this comb filter is a separation method that takes advantage of the vertical correlation of the signals, so it can be used to separate the carrier color signal from the color video signal. In the correlation section, the luminance signals cannot be canceled out completely, and cross color occurs. In separation circuits that utilize vertical correlation, not just comb filters, cross color always occurs in the vertical non-correlation portion.

Therefore, in the present invention, this cross color generated in the vertical non-correlation portion can be removed or significantly suppressed with a simple configuration.

An example of the present invention will be described in detail below with reference to the drawings. Figure 1 shows a case where the application is applied to a so-called Y/C separation circuit that separates a color video signal into a luminance signal and a carrier color signal.The color video signal Si supplied to terminal 1 is supplied to a high-pass filter 2, and the luminance The high-frequency component Y _H of the signal Y _W and the signal Sa containing the carrier color signal Sc are separated, and the separated high-frequency color video signal Sa is supplied to the synthesizer 4 together with the original color video signal Si to generate a low frequency signal. The area luminance signal Y _L is separated.

The high frequency color video signal Sa is further supplied to the separation circuit 10 according to the present invention to separate the carrier color signal Sc, which is supplied together with the high frequency color video signal Sa to the synthesizer 5 to generate the high frequency luminance signal _YH . separated,
This is further supplied to the synthesizer 6 to generate a low-range luminance signal.
Synthesized into Y _L. Therefore, the synthesizer 6 obtains a broadband luminance signal Y _W that does not include the carrier color signal Sc.

Now, the separation circuit 10 is provided with an amplitude correlator 20 that performs special signal processing, and a pair of signals is supplied to this. Both high-frequency color video signals are used as the pair of signals. In this case the carrier color signal
In order to separate Sc, one of the pair of signals input to the amplitude correlator 20 is delayed by one horizontal period (1H) with respect to the other, and one of the signals is made into a phase-inverted signal. In the example shown in the figure, a 1H delay circuit 11 is connected to one input side of the amplitude correlator 20.
and an inverter 12 are provided to supply the high-frequency color video signal Sa itself and the high-frequency color video signal delayed by 1H and reversed in phase.

The amplitude correlator 20 determines the correlation between the pair of input signals Sa, and when there is no correlation,
In other words, when the amplitude (polarity) of one signal Sa (or) is positive and the amplitude of the other signal is negative, the output is zero, and when there is a correlation, the amplitude of both signals Sa, is positive. Alternatively, the signal is output only when it is negative, and in this case, it is configured such that a signal with a particularly small amplitude is output.

For example, if the signal Sa is defined as shown in Figure 2A, the section where the signal Sa has the same polarity is
Among Ta and Tb, the signal with the smaller amplitude in the sections Ta and Tb is a signal in the sections Ta ₁ and Tb ₁ , and is the signal Sa in the sections Ta ₂ and Tb ₂ , so the signal in the shaded area and the signal in the The signal Sc shown in FIG. 2B is then output.

Next, the carrier color signal using this separation circuit 10 is
Let us explain the separation operation of Sc with reference to Figure 3 and subsequent figures.

As shown in Figure 3, there is a low-saturation image in which a portion of the entire red image has a vertical print (a vertical print that is dark in the first half and bright in the second half in the horizontal scanning direction), and therefore the color components of the vertical print are Consider an image that has fewer color components than other parts. Then, consider the signals at each point p to r when the relationship between the horizontal line on the image sending side and the image is determined as shown in the figure.

The signal at point q on the (n-2) line is a composite output (FIG. 4C) of the conveyance color signal shown in FIG. 4A, which represents red on the entire surface, and the luminance signal shown in FIG. Therefore, the high frequency color video signal Sa on each horizontal line including point q is as shown in Figure 5A, and the high frequency color video signal Sb delayed by 1H is as shown in Figure 5B.
Therefore, in the conventional separation method using a comb filter, signal processing such as Sb-Sa≡Sd is performed, so the carrier color signal Sd output from the comb filter is as shown in C in the same figure. In particular, the signal formed from the (n-1) line and the n line should originally be only a carrier color signal component, but since there is no vertical correlation between these lines, cross color (as shown in C in the same figure) is generated. (Diagonal line shown)
occurs.

On the other hand, when the amplitude correlator 20 is used, the carrier color signal Sc becomes as shown in FIG. That is,
Since the polarity does not match that of the signal Sa in the vertical correlation section where the luminance component exists, none of the signals Sa, is output, and since the polarities match (are the same) outside the section W, the signals Sa, The one with the smaller amplitude is output. In the figure, since the amplitudes are the same, one of the signals is output.

On line n, the polarity in section W is the same, so
The one with the smaller amplitude, ie, the signal Sa, is output.
Since the signal Sa is the output of n lines and contains only the carrier color signal component, the carrier color signal Sc does not include the high-frequency luminance signal _YH at all. Therefore, the cross color in the vertical non-correlation part is completely removed.

The waveform diagram in FIG. 6 is an example of the image in FIG. 3 in which the first half of the vertical document is bright and the second half is dark.

By the way, in an actual video signal, the carrier color signal shown in FIG. 4A and the luminance signal shown in FIG. 4B have various values. Therefore, the effects of the more generalized present invention will be explained.

The amplitude e of a pixel at any horizontal scanning position equal to the vertical direction can be expressed as follows.

e _o-2 ＝Y _Ho-2 ＋C _o-2・P ₁ e _o-1 ＝Y _Ho-1 ＋C _o-1・P ₂ e _o ＝Y _Ho ＋C _o・P ₁ ...(1) e here : Signal amplitude Y _H : Luminance component C: Carrier color signal component P: Color subcarrier phase term, when P ₁ = 1, P ₂ = -
1 Y _H in equation (1) can be expressed as follows using a coefficient K representing the amount of luminance component and a coefficient M representing the amount of vertical correlation.

e _o-2 =K _o-2・M _o-2・Y ₀ +C _o-2・P ₁ e _o-1 =K _o-1・M _o-1・Y ₀ +C _o-1・P ₂ e _o =K _o・M _o・Y ₀ +C _o・P ₁ ...(2) where K: Coefficient representing the amount of luminance component M: Coefficient representing vertical correlation (when there is correlation, M=
1) Y ₀ :Unit luminance component In equation (2), for convenience of explanation, it is assumed that the values of the carrier color signal component C and the coefficient K are equal between scanning lines.

C _o-2 = C _o-1 = C _o = C ₀ K _o-2 = K _o-1 = K _o = K In addition, the (n-2) and (n-1) lines are connected to the correlation section,
If we set n lines as uncorrelated parts and set M _o-2 =1 M _o-1 =1 M _o =0, equation (2) becomes as follows.

e _o-2 =K・1・Y ₀ +C ₀・P ₁ e _o-1 =K・1・Y ₀ +C ₀・P ₂ e _o =K・0・Y ₀ +C ₀・P ₁ ……(3 ) Here, in order to see what value the output (amplitude) e _c of the separation circuit 10 becomes when the coefficient K is used as a variable, that is, when the amount of the luminance component is changed, first K
FIG. 7 shows the input signal e to the amplitude correlator 20 when the abscissa represents the input signal e to the amplitude correlator 20. Therefore, in the correlation section where the luminance component exists, an output e _c shown by the broken line in FIG. 8A is obtained. Further, in the non-correlation section, an output e _c shown in FIG. 8B is obtained.

Incidentally, the ideal output from this decorrelation section is the n-line output e _o itself. The conventional separation output using a comb filter is e _c ′, and especially in the region of K < K ₁ , the phase is reversed with respect to the ideal output e _o , so it is not related to the original color. Complementary colors that are not available will be played. On the other hand, according to the present invention, the output e _c takes a value between zero and C ₀ , so
This is a significant improvement compared to the conventional method. Note that in a correlation section without a luminance component, the result is as shown in FIG. 8C.

Also, as an important feature of the present invention, the carrier color signal e _c which is the separated output in the vertical decorrelation section is shown in FIG.
As shown in FIG. B, as the coefficient K increases and therefore the luminance component increases, it changes continuously to zero.

FIG. 9 shows a concrete example of the amplitude correlator 20, which is composed of four differential amplifiers. A _{predetermined} DC bias E _B (for example _, 1/2
A signal Sa superimposed on Vcc) is supplied, and the bases of transistors Q ₂ and Q ₄ are also supplied with a DC bias E _B
A signal superimposed on the is supplied. Since the first differential amplifier 21 operates as a logical sum, when the pair of signals _Sa , is inputted in the state shown in _FIG . The output) x is as shown in FIG. 10B. Further, since the second differential amplifier 22 operates as a logical product, the common emitter output (first logical product output) y of the transistors Q ₃ and Q ₄ becomes as shown in FIG.

The third differential amplifier 23 to which the first OR output x is supplied is configured to operate as an AND, and therefore the second AND output obtained therefrom.
Sc ₁ becomes Figure 10D. Further, the fourth differential amplifier 24 to which the first logical product output y is supplied is configured to operate as a logical sum, and therefore the second logical sum output Sc ₂ shown in FIG. 10E is obtained. . The composite output Sc of these outputs Sc ₁ and Sc ₂ is output to the output terminal 26.
obtained from. This composite output Sc is the same as the output shown in FIG. 2B, and it is therefore understood that if the high frequency color video signal Sa, is supplied to the amplitude correlator 20, the carrier color signal Sc can be separated.

FIG. 11 shows a case where a separation circuit 10 is configured by combining a conventional comb filter and an amplitude correlator 20.
As is well known, the comb filter 30 is composed of a 1H delay circuit 31 and a synthesizer 32, and the high frequency color video signal Sa is supplied to the comb filter 30, and its output Sd is supplied to the amplitude correlator 20. Therefore, a part of the output Sd is sent to the delay circuit 11 and the inverter 12.
An inverted output delayed by 1H with respect to the output Sd is formed, and these outputs Sd are supplied to the amplitude correlator 20.

The separation operation when the separation circuit 10 is configured in this way will be explained using the pattern shown in FIG.
The result will be as shown in FIGS. 5 and 6. That is, the first
If the output of each circuit is determined as shown in FIG. 1, the finally obtained carrier color signal Sf will be as shown in FIGS. 5F and 6F. In the case of FIG. 1 which does not use the comb filter 30, the carrier color signal Sc in the vertical correlation section where the luminance component is present is partially omitted as shown in FIG. 5D or FIG. 6D. In the case shown in FIG. 11, which also uses the shaped filter 30, the carrier color signal Sc is faithfully reproduced even in the vertical correlation section where the luminance component is present.

Figure 12 is a modification of Figure 1, in this example 1H
Instead of inverting the phase of the delayed high-frequency color video signal Sb, the phase of the undelayed high-frequency color video signal Sa itself is inverted by the inverter 12 and then supplied to the amplitude correlator 20. This is a case where the color signal Sc is separated.

FIG. 13 shows a modification of FIG. 11, in which two comb filters 40 and 50 are used, and the first comb filter 40 is composed of a 1H delay circuit 41 and a synthesizer 42. The second comb filter 50 is composed of a 1H delay circuit 51 and a synthesizer 52. Even if the separation circuit 10 is configured in this way, the carrier color signal Sc can be separated as in the case of FIG. That is _, when the transfer function of the signal _Sd , which is input to the amplitude correlator 20 in FIG.
(t), then e _d (t)=e(t)/2(ε ^-j 〓 ^TH -1)...(4) e _e (t)=e(t)/2(ε ^-j 〓 ^TH −ε ^-j2 〓 ^TH )……(
5) However, T _H is the horizontal period and ω = 2πf. On the other hand, in the configuration of FIG. 13, the amplitude correlator 20
Similarly _, the transfer function of the signal _Sd ′,′ input to
Then, e _d ′(t)=e(t)/2(ε ^-j 〓 ^TH −1) ...(6) e _e ′(t)=e(t)/2(ε ^-j 〓 ^TH − ε ^-j2 〓 ^TH )…
…(7) becomes. That is, it can be seen that the same signal separation as in FIG. 11 can be achieved even if Sd'=Sd,'= and the configuration is as shown in FIG. 13.

As described above, according to the present invention, it is possible to remove cross color occurring in the vertical non-correlation portion. Therefore, image quality can be improved compared to a conventional separation circuit using a comb filter. When the separation circuit 10 is constructed using comb filters 30 to 50 as shown in FIG. 11 or 13, the carrier color signal component is missing even in the vertical correlation section where the luminance component is present. The image quality can be further improved.

[Brief explanation of the drawing]

FIGS. 1 and 11 are system diagrams showing an example of the separation circuit according to the present invention, FIG. 2 is a diagram explaining the operation of the amplitude correlator, and FIGS. 3 to 8 explain the separation operation of the carrier color signal. 9 is a connection diagram showing a specific example of the amplitude correlator, FIG. 10 is an explanatory diagram of its operation, and FIGS. 12 and 13 are system diagrams showing other embodiments of the present invention. be. 10 is a separation circuit, 20 is an amplitude correlator, 30 to 5
0 is a comb filter, and 11, 31, 41, and 51 are delay circuits.

Claims (1)

[Claims] 1. An amplitude correlator configured to output a signal with a smaller amplitude only when a pair of signals of equal polarity is input, and a color video signal and a color video signal, A color video signal obtained by inverting the phase of a color video signal one horizontal period before this color video signal is supplied, and a carrier color signal without cross color is separated by this amplitude correlator. separation circuit. 2. It has an amplitude correlator that outputs a signal with a smaller amplitude only when a pair of signals of equal polarity is input, and a comb filter, and a luminance signal output from the comb filter. The carrier color signal including the carrier color signal and the carrier color signal obtained by delaying the carrier color signal by one horizontal period and inverting the phase are supplied to the amplitude correlator, and the carrier color signal without cross color is separated by the amplitude correlator. A separation circuit for carrying color signals.