KR960005488B1 - TV's luminance / chromatic signal separation circuit - Google Patents

Abstract

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Description

TV's luminance / chromatic signal separation circuit

1 is a conventional luminance / chromatic signal separation circuit diagram.

2 is a signal selection characteristic diagram of a switching unit of a conventional circuit.

3 is a control flowchart of FIG.

4 is an explanatory diagram according to the configuration of a comb filter.

5 is a waveform diagram illustrating the correlation between (Va, Vb) and (Vb, Vc).

6 and 7D are explanatory diagrams for explaining the problems of FIG.

8 is a luminance / chromatic signal separation circuit diagram of a television of the present invention.

9 is a control flowchart according to the present invention.

10 is a difference signal frequency characteristic diagram of a correlation determination function.

* Explanation of symbols for main parts of the drawings

20, 21: 1H delay section 22: matrix section

23: band pass filter 24: switching unit

25,26: low pass filter 27,28: comparator

The present invention relates to a circuit that separates a luminance signal and a chroma signal from a TV signal, and in particular, a luminance / chromatic signal of a TV that prevents an error at the boundary of the chroma signal in the vertical direction so that the chroma signal can be accurately separated. It relates to a separation circuit.

FIG. 1 is a conventional luminance / chromatic separation circuit, in which a TV video signal passes through a band pass filter 1 and then passes through 1H delay units 2 and 3, as shown in FIG. And output signals Va, Vb, and Vc of the 1H delayers 2 and 3 are input to the matrix unit 4, respectively.

The correlation code Vb + Vc for the output signals Vb and Vc of the 1H delayers 2 and 3 is applied to one input terminal A of the comparator 8 via the envelope detector 5 and the band The correlation signal Va + Vb with respect to the output signals Va and Vb of the pass filter 1 and the 1H retarder 3 is connected to one input terminal A of the comparator 7 via the envelope detector 6. Is approved.

The comparators 7 and 8 are respectively supplied with reference signals Vref ₁ and Vref ₂ to the other input terminals B and B, and the output signals S1 and S0 are input to the switching unit 9, The output section Vb of the 1H retarder 2 and the output signal of the matrix 4 are respectively applied to the switching section 9.

The operation and problems of the conventional luminance / chromatic separation circuit configured as described above will be described in detail as follows.

When the signal constituting the TV screen is shown in FIG. 4, an output signal Va of the band pass filter 1 and an output signal Vb of the 1H delayers 2 and 3 are used by using a comb filter. Three methods for separating the luminance signal and the chroma signal from (Vc) are as follows.

The first method separates the color signal using Va and Vb. The red signal is separated by the formula (Vb-Va) / 2.

In the second method, the color signals are separated by using the Vb and Vc signals. When the color signals are separated using the formula of (Vb-Vc) / 2 as described above, the color signals having the size of 50% are larger than those of the first method. Is output.

This means a color signal loss of 50%, and 50% of the lost color signal is introduced into the luminance signal, causing a defect in image quality. The third method is to separate color signals by using Va, Vb, and Vc signals. When color signals are separated by the time of (Vb- (Va + Vc)) / 2) / 2, 75% of the color signal is generated. Among the above three methods, the first method is the luminance / color signal separation method using Va, Vb, which is the most appropriate method. It was announced.

As an example, FIG. 1 is a method published by Rossi, and includes (Vb-Va) / 2, (Vb-Vc) / 2, (Vb- (Va + Vc) / 2) / 2 signals and a band pass. The signal Vb passing through the filter 1 and delayed through the 1H retarder 2 is input to the switching unit 9, and is controlled by the control signals S1 and S0 output from the comparators 7 and 8. One of the four signals is selected to generate a color signal output, and the control signals S1 and S0 are generated by comparing the color difference with the upper and lower signals Vc and Va in the center line signal Vb of FIG. There is no difference in color when the Vb (red) signal is compared with the upper line (red) signal. That is, the correlation of color is large.

On the other hand, when the Vb (red) signal and the lower line Vc (black) signal are compared, there are many color differences. In other words, there is little correlation between colors. In this way, the concept of generating a control signal of S1 and S0 is applied so that one of four signals can be selected by examining the correlation between colors with upper and lower lines.

As a method of investigating the correlation between Va and Vb signals, the color signal phase of the 1H line interval is inverted by 180 °, so that the color signal correlation of (Va, Vb) is generated through (Va, Vb) and then through the envelope detector 6 Then, the color signal correlation function of | Vb + Va | is calculated.

Similarly, the color signal correlation function | Vb + Vc | of Vb and Vc is calculated.

5 is a correlation waveform of (Va, Vb) and (Vb, Vc). The color signal correlation functions | Vb + Va | and | Vb + Vc | are reference signals Vref ₁ and Vref predetermined in the comparators 7,8. ₂ ) and control signals S1 and S0 are generated according to the result.

In the operation of the comparators 7, 8, (S1, S0) = (0, 0) means that the upper and lower correlations of the color are large (Vb- (Va + Vc) / 2) / 2. Determined by output If (S1, S0) = (0,1), the correlation of (Va, Vb) is greater than that of (Va, Vc), so that (Vb-Va) / 2 is determined as the output and is 100% as shown in FIG. Has a degree of separation.

2 shows the signal selection characteristics of the switching 9 with respect to the color tube diagram | Va, Vb | and (Vb, Vc) of the color tube diagram | Vb + Vc |.

That is, when | Vb + Va | and | Vb + Vc | are both smaller than the predetermined reference signals Vref ₁ and Vref ₂ , the output of (Vb- (Va + Vc) / 2) / 2 signal is selected, and | Vb (Vb-Va) / 2 is selected when + Va | is smaller than the predetermined reference signal Vref ₂ .

If Vb + Vc is smaller than the predetermined reference signal Vref ₁ , (Vb−Vc) / 2 is selected. If all are larger than the reference signals Vref ₁ and Vref ₂ , the intermediate filtered Vb line is selected. .

3 is a flowchart of the prior art, in which a color signal correlation function of | Vb + Va | and | Vb + Vc | is calculated after the composite video signal passes through the band pass filter 1, and the reference signals Vref ₁ and Vref ₂ are calculated. ) To generate control signals S1 and S0.

And four signals of (Vb-Vc) / 2, (Vb-Va) / 2, (Vb- (Va + Vc) / 2) / 2 and mid-band filtered Vb according to four combinations of S1 and S0. Either is selected.

However, as shown in FIGS. 6 and 7, when the Va, Vb, and Vc lines are configured, the rise time is very large at the boundary between black and red when the color signal correlation function of Va + Vb is obtained.

The reason why the rise time is so large is that the rise time is eight times larger because the bandwidth of the color signal corresponds to 1/8 of that of the luminance signal.

As shown in FIG. 7, the ideal control signal S1 should be generated at the boundary between black and red, but the control signal S1 having an error range is generated because the bandwidth of the color signal is small.

In addition, as shown in FIG. 7, when the luminance signal of 3.58MH _Z is input, the value of the upper and lower color signal correlation functions of Va + Vb and Vb + Vc is very large, whereby (1,1) = (S1) Since, S0) occurs, the mid-band filtered Vb signal is output as a color signal, thereby causing a cross color phenomenon.

Accordingly, the present invention uses the comb filter and the bandpass filter by the luminance difference signal instead of the color difference signal to solve the defects caused by the conventional chromaticity / luminance signal separation circuit. ) Is a chromaticity / luminance signal separation circuit which prevents the reduction of the luminance / color separation due to the error range occurring in the phenomenon and the transition period, which will be described in detail with reference to the accompanying drawings.

FIG. 8 is a chromaticity / luminance signal separation circuit diagram of the present invention. As shown therein, the TV video signal Va inputted through the 1H delayers 20 and 21 is connected to the TV image signal Va and the 1H delayer. The outputs Vb and Vc of (20, 21) are input to the matrix unit 22, and the matrix unit 22 calculates the vertical transition signals Vb-Vc and Vb-Va which are luminance difference signals. The resulting (Vb-Va) / 2, (Vb-Vc) / 2, and (Vb- (Va + Vc) / 2) / 2 signals are output.

The vertical transition signals Vb-Vc and Vb-Va become luminance difference signals | Vb-Vc | and | Vb-Va | through the low pass filters 25 and 26, respectively.

The luminance difference signal | Vb-Vc | is compared with the reference signal Vref ₂ in the comparator 28 to generate the control signal S0, and the luminance difference signal | Vb-Va | is compared with the reference signal Vref ₁ and the comparator ( 27 to generate a control signal S1.

The output signal Vb of the 1H retarder 20 is input to the switching unit 24 through the band pass filter 23, and the output signal of the matrix unit 22 is also input to the switching unit 24.

Referring to the operation and effects of the circuit of the present invention configured as described above in detail as follows.

First, in FIG. 8, the vertical transition signal Vb is obtained by using the video image signal Va and the signal Vb having passed through the 1H delayer 20 and the signal Vc having passed through the 1H delayer 21 again. -Vc) and (Vb-Va) are detected.

This signal is passed through the low pass filters 25 and 26 to output luminance difference signals | Vb-Vc | and | Vb-Va |.

The luminance difference signals | Vb-Vc | and | Vb-Va | outputted as described above are compared with the reference signals Vref ₁ and Vref ₂ in the comparators 28 and 27, respectively, and control signals S1 and Generate S0).

In FIG. 9, if S0 = 0 and S1 = 1, there is no correlation between the luminance of the Va signal and the Vc signal around Vb. Therefore, the signal through the band pass filter 23 is selected as an output, and if S0 = 1 and S1 = 0, Since the luminance correlation between the Vb signal and the Va signal is large, a comb-filtered (Vb-Va) / 2 using the Va signal and the Vb signal is selected as an output. The comb-filtered signal (Vb-Vc) / 2 using the signal and the Vc signal is determined as an output.If S0 = 0 and S = 0, there is a correlation between the luminance of Va, Vb, and Vc signals. The line comb filtered signal (Vb− (Va + Vc) / 2) / 2 used is determined as an output.

The frequency components of the signals Vb-Vc and Vb-Va output from the matrix unit 22 are shown in FIG. 10, and the vertical shift signal of the luminance between the lines around the color signal and the low range around 3.58MH _Z (Δ Y) is located. The ΔY is extracted through the low pass filters 25 and 26 to obtain a correlation function of the luminance signal.

Therefore, in determining whether to use a 2-line or 3-line comb filter or an in-line band pass filter in the color TV signal, the luminance difference signal is used as a criterion instead of the color difference signal. Due to the error range, it is possible to prevent the reduction of the luminance / chromaticity (Y / C) separation.

As described above, the present invention provides an effect of separating an improved chromaticity signal by preventing an error at the chromaticity signal boundary in the vertical direction in separating the luminance signal and the chromaticity signal.

Claims (1)

1H delay units 20 and 21 for sequentially delaying the composite video signal in units of one line, and combining the delayed signals to generate a vertically shifted signal of luminance generated by subtracting a plurality of com-filtered color signals and delayed signals. A matrix unit 22, low-pass filters 25 and 26 for low-pass filtering the luminance shift signal generated by the matrix unit 22, and reference signals Vref ₁ and Vref having predetermined magnitudes of the low-pass filtered signals. ₂ ) select one of the comparator 27 and 28 for comparison with the output signal of the comparator 27 and 28, and a plurality of comb filtered color signals generated and a color signal obtained by intermediate filtering the delayed signal. The luminance / chromatic signal separation circuit of the TV, characterized in that consisting of a switching unit 24 for outputting.