JPS62145992A - Comb-line filter circuit - Google Patents

Abstract

PURPOSE:To reduce the leakage of a chrominance signal into a luminance signal by judging a separated color signal whether it is a leakage of the higher components of the luminance signal or is an original chrominance signal, and adjusting the amplitude of an output chrominance signal. CONSTITUTION:The current scanning line and a one-field delayed by one are summed up by a field memory 8 and an adder 9, and chrominance signal components are eliminated by a trap circuit 10, and the absolute value of the high-frequency band is obtained by a high-pass filter 11 and an absolute value circuit 12. The amplitude of the said absolute value and a reference value R are compared with each other by an amplitude comparing circuit 14. By using the output of the circuit 14, an amplitude adjusting circuit 15 adjusts the amplitude the chrominance signal output of a comb-line filter consisting of line memories 3a and 3b, multipliers 4-6, an adder 5, and a band pass filter 8. In case where the luminance signal has a high frequency components close to the chrominance signal, because the output of the circuit 12 exceeds the reference value R, the circuit 15 limits the amplitude of the chrominance signal to decrease the leakage of the luminance signal into the chrominance signal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a color television receiver, and more particularly to a comb filter that improves the degree of separation of luminance signals and color signals from a composite color television signal. [Background of the Invention] Conventionally, low-pass filters (L, P, F) and band-pass filters (B, P,
F') method and a method using a comb filter using scanning line memory (Television 1) Academic Journal VOL, 5
5, No. 4 (1979) Synthesis and Separation of Color Television Signals). In the case of m-users, it is necessary to widen the passband widths of B, P, and F in order to obtain a Y signal that has sufficiently removed the C signal, which has the disadvantage that the high frequency components of the Y signal are lost and the resolution deteriorates. there were.

FIG. 8 is a diagram showing the latter method. In this figure, 1 is a composite color TV signal input terminal 2 and 3ViIH
Memory, 4 to 6 are multipliers, 7 is an adder, 8 is a band pass filter, and 9 is a subtracter.

10 is a C signal output leaker, and 11 is a Y signal output terminal.

This comb filter basically takes advantage of the fact that there is a correlation in the vertical direction of the image, and that the phase of the carrier color signal is reversed line by line.

It performs YC separation. In FIG. 8, A indicates a composite color television signal of three adjacent scanning lines (l-1), C6) and (l+1), and the respective signals are multiplied by multipliers 4 to 6 to -j l −1 weighting t431° The outputs of these multipliers are added by an adder 7 (Ic), and low frequency components are removed by a bandpass filter 8.

The C signal on the IJI line can be extracted.

On the other hand, Iil, calculator 9 calculates (1) the composite force of line 2-
The C signal extracted above is removed from the television signal (Dl.

As a result, only the Y signal can be obtained at its output.

Now, what about conventional comb filters like this one?

Like the diagonal stripes, the Y signal has high frequency components (B in Figure 8).
, P, F), this is exactly the same pattern as the carrier color signal and is therefore considered to be a C signal, resulting in cross color in which the Y signal leaks into the C signal. was.

[Object of the Invention] The object of the present invention is to eliminate the drawbacks of the prior art described above and to provide a high-quality screen that does not cause interference such as cross color even when the luminance signal has high frequency components such as diagonal stripes. It is an object of the present invention to provide a comb filter that improves the performance of YC separation.

[Summary of the invention]

In order to achieve the above object, the present invention provides means for determining whether a color signal separated by one is an original color signal or a leakage of high-frequency components of a luminance signal. If it is determined that it is a single color signal, the color signal is output as is,
When it is determined that the brightness signal leaks, the amplitude is adjusted to reduce the brightness signal leak.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to FIG. 1st
The figure shows an embodiment of the comb filter circuit according to the present invention. In the figure, 1 is a composite color TV signal input terminal, 2 is an A/D converter, 6 is false, sb is a 1H memory, and 44 to 4C are A multiplier, 5 an adder, and 6 a bandpass filter.

8 is field memory, 9 is adder, 10 is 3.58M
Hz) wrap circuit, 11 is a high-pass filter.

12 is an absolute value conversion circuit, 15 is a reference value input terminal, 14 is an amplitude comparison circuit, 15 is an amplitude adjustment circuit, 16 is a C signal output terminal, 17 is a subtracter, and 18 is a Y signal output terminal.

The configuration of this circuit will be explained below. This embodiment shows a case where a 2H-type comb filter as shown in FIG. 8 is used as a comb filter that utilizes signals between scanning lines.

The operating principle of this 2H-type comb filter is as explained in FIG. Here, the field memory 8 and adder 9 add the current scanning line and the scanning line delayed by one field, and the color signal component of the sum signal is 3.58MH.
The high frequency component is removed by a trap circuit 10 with a steep z, and the high frequency component is extracted by a high pass filter 11.
The absolute value of the output of the high-pass filter is taken by the absolute value conversion circuit 12, and the amplitude of the absolute value R is compared with a certain reference value R by the amplitude comparison circuit 14, and the color signal of the comb filter is determined by the output of the comparison circuit. A new amplitude adjustment circuit has been added to adjust the output amplitude.

The operating principle of this newly added circuit will now be explained. In this circuit, the color signal output of the comb filter circuit is
It is determined whether the color signal is the original color signal or the leakage from the luminance signal, and the color signal output is adjusted based on the determination result.

This operation will be explained using FIGS. 2 and 6. FIG. 2 shows the 4 degree signal in the current scanning line, and FIG. 6 shows the absolute value of the output of the high-pass filter 11. In the case of Figure 2 (1), there is no high frequency component, so
Basically, YC separation can be performed using a comb filter, and the Y signal does not leak into the C signal. Therefore, the output of the high-pass filter 11 that outputs the high-frequency component of the Y signal and the absolute value converting circuit 12 are as shown in FIG. 5 i11. /) It became like this.

The value becomes less than or equal to the reference value R, and the separated C signal (but not in this case) is output as is from the amplitude adjustment circuit 15. When the luminance signal is as shown in FIG. 2 (It), Y has a high-frequency component in the etched part, and the Y signal leaks into the C signal in this part. In this case, the high-pass filter 11 and The output of the absolute value conversion circuit 12 is shown in FIG.
i, and only in the etched part, the reference lit
Go beyond R. Therefore, the amplitude adjustment circuit 15 limits the output amplitude of the bandpass filter 6 only in the etched portion, and outputs the output of the bandpass filter 6 as is in the other portions. However, since the C signal does not originally exist, there is no problem. When the luminance signal has a high frequency component close to the color signal as shown in FIG. 2(iii), the bandpass filter 11
Then, the output of the absolute value converting circuit 12 becomes as shown in +1ii1 in FIG.

The standard value R is exceeded. In this case, since the Y signal will leak into the C signal, the amplitude adjustment circuit limits the amplitude of the bandpass filter 6 to reduce the leakage of the Y signal into the C signal. Therefore, cross color is significantly reduced.

Even if the luminance signal has high-frequency components in this way,
Leakage of luminance signals can be determined and reduced.

Next, as a second example, consider a case where a color signal is added to the luminance signal in FIG. 2. An embodiment of the comb filter according to the present invention in this case will be explained using FIG. 5 and a waveform diagram in FIG. 4. FIG. 4(1) is a luminance signal that changes stepwise.

(1) is the color signal, +1) is the luminance signal of (1) and (
This is a composite color television signal to which the color signal of 11) is added.

FIG. 5 shows a comb filter according to the invention.

In the figure, 19 is a composite color TV signal input terminal;
20 is an A/D converter, 214.21b is a line memory, 224-22C is a multiplier, 25.27 is an adder, 2
4 is a band pass filter, 25 is a subtracter, 28 is i58M
Hz trap circuit, 29 is a high-pass filter, 60 is an absolute value conversion circuit, 31 is a reference signal input terminal, 32 is an amplitude comparison circuit, 36 is a color demodulation circuit, 34 and 56 are 1 sample data delay elements.

65 is a changeover switch, and 42 is an amplitude adjustment circuit.

The configuration of FIG. 5 is basically the same as that of the comb filter shown in FIG.
An f-nipple data delay element is added. When a signal like the one shown in FIG. , the color signal is separated and output from the bandpass filter 24. However, in the etched portion, high-frequency components of the luminance signal leak into the color signal. Here, using the field memory 26, the composite color television signal of the current scanning line and the composite color television signal of the corresponding scanning line delayed by one field are stored.
When the sum of g is calculated by the adder 27, if it is a still image, the color signal components of the current scanning line and the corresponding scanning line one field before are inverted in phase, so the color signal component is removed.

Therefore, the high-frequency component of the luminance signal is extracted from the high-pass filter 29, and when its absolute value is taken by the absolute value conversion circuit 60, it becomes as shown in FIG. 4 (1v). The amplitude comparison circuit 66 compares the amplitude of this absolute value and the reference signal R, and if the absolute value exceeds the reference signal R, the amplitude adjustment circuit 66
2 limits the amplitude of the color signal. In this case, as in FIG. 3 111, since the amplitude of the color is limited in the etched portion, there is a problem that the color becomes fainter in the edge (→) portion. Therefore, in this case, the bandpass filter 2
The color signal extracted from 4 is passed through the color demodulation circuit 34,
If the absolute value exceeds the reference value R by the bump data delay elements 34, 36 and the changeover switch 65 (if the 4-inverse signal is considered to have leaked into the color signal and the color is dimmed), Without outputting the current sample data of the color signal,
Switch 35 to change the color signal that is delayed by 1 length
Take it out. If the absolute value is less than the reference value R (there is no leakage of the luminance signal into the color signal), the current sample data of the color signal is taken out by the changeover switch 65.

As described above, even if the luminance signal is a composite color television signal with high-frequency components, the leakage of the luminance signal can be determined,
If it is determined that there is leakage, the negative effect can be removed by interpolating the color signal, which is limited to the amplitude of the color signal but delayed by 1f sample data.

Next, consider the case of videos. Now, as shown in Figure 6, if the color changes from the previous field (:) to the current field ill (G indicates green, B indicates blue).
In this case, the relationship in which the phase of the color signal of the current scanning line and the corresponding color signal of one field before are reversed disappears. Therefore, even if the input and output signals of the field memory 26 are summed, an output due to the color signal component occurs in the shaded area, and as a result, a problem arises in that the color becomes faint. However, since the color signal component is removed by the steep 5.58 MHz wrap circuit 28 in the next stage, no adverse effects occur and the same operation as in the case of still images can be obtained. Note that this trap reduces the effect of cross color suppression in the case of 11 in FIG. 2, but if the trap band is made sufficiently narrow, the reduction in effect is slight.

Finally, we will discuss the circuit configuration for reducing field memory. FIG. 7 shows a circuit configuration for memory reduction, in which 57 is a composite color television signal input terminal, 58 is an analog band pass filter, and 39 is an A/D converter.

40 is a digital band pass filter, and 41 is a field memory. (1) is an A/D converter (20 in Figure 5).
An analog band pass filter is provided in front of the field memory 41 (corresponding to fil).
A digital band-pass filter is provided in front of the filter (corresponding to 26 in Figure 5). In either case, the memory is reduced by removing the low-frequency component of the luminance signal, and by adding these circuits, the memory can be reduced and the same effect can be obtained.

Although field memory is used in this embodiment, it goes without saying that similar effects can be obtained using frame memory.

〔Effect of the invention〕

As described above, according to the present invention, even when the luminance signal has high-frequency components, such as diagonal stripes, which is difficult to achieve with conventional comb filters, the luminance signal can be prevented from leaking into the color signal. By providing a circuit that determines whether the color signal is the original color signal, the leakage of the luminance signal into the color signal is reduced, and YC
It becomes possible to perform separation correctly and suppress cross color to a large extent.

[Brief explanation of drawings]

, @1, and 5 are block diagrams showing the basic blocks of the comb filter according to the present invention, and Figures 2, 3, and 4 are waveform diagrams for explaining the operation of the comb filter according to the present invention.
Fig. 6 is an explanatory diagram of the operation in the case of a moving image, Fig. 7 tal,
tM is a block diagram of a circuit for memory reduction, wc
Figure B shows a conventional comb filter, and Figure 8 (α)
8 is a block diagram (the phrase is a waveform diagram of each part. 1... Composite color TV signal input terminal 2... A/D
Converter 3α, 54... line memory 4l-4
G... Multiplier 5, 9... Adder 6... Bandpass filter 8... Field memory 10=-3.
58MHz) Wrap 11...High-pass filter 12...Absolute value circuit 16...Reference value input terminal 14...Width comparison circuit 15...Width adjustment circuit f'-1 [' Substitute Katsuo Ogawa, FP Physician. Section 1, Section 2, Section 2, Section 3 (iiB) Section 4, Section 5, Section 7 (α) (b)

Claims (1)

[Claims] In a comb filter circuit that separates a luminance signal (Y) and a chrominance signal (C) from a composite color television signal in which a luminance signal and a chrominance signal are frequency multiplexed, the input/output signals of one or more line memories are used to The means for configuring the comb filter and the current scan line and one frame (or one
field) adding means for calculating the sum with the previous corresponding scanning line; first removing means for removing the color signal component of the output of the adding means; a second removing means connected in cascade with the first removing means; an absolute value converting means for taking the absolute value of the output of the cascaded subsequent removing means; and a certain standard based on the output of the absolute value converting means. 1. A comb filter circuit comprising: a comparison means for comparing a color signal with a color signal; and an amplitude adjustment means for adjusting the amplitude of the color signal separated by the comb filter based on the output of the comparison means.