JPH03123190A - Comb line luminance signal/chrominance signal separating circuit - Google Patents

Abstract

PURPOSE:To eliminate a residual chrominance signal component from a luminance signal by allowing the luminance signal containing the residual chrominance signal component to pass through a comb line filter. CONSTITUTION:A signal delaying means 12 delays a luminance signal by a prescribed horizontal synchronizing period, and a first subtracting means 13 subtracts the luminance signal delayed by the signal delaying means 12 from the luminance signal and extracts a residual chrominance signal component. A second subtracting means 15 subtracts and eliminates the residual chrominance signal component extracted by a first subtracting means 13 from the luminance signal. In such a way, the residual chrominance signal component can be eliminated from the luminance signal separated from a composite video signal, and a beat of a residual chrominance signal generated on a screen and a chrominance signal C is reduced, therefore, the picture quality can be improved.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention is implemented in a television monitor or a VTR,
Related to a comb-shaped luminance signal/chrominance signal separation circuit that separates a luminance signal and a chrominance signal from a composite video signal (prior art) A comb-shaped luminance/chrominance signal (YC) separation circuit has conventionally had a configuration as shown in Fig. 3. ing. That is, the input Fig. 5 (
3 composite video signal 100 as shown in A> is composed of a direct signal 101 and a delayed signal by delay element 1 (here, NTSC
(IH delay in case of PAL method, 2H delay in case of PAL method)
By calculating the sum and difference with 1o2 using an adder 2 and a subtracter 3, the luminance signal Y and the color signal C are separated. The principle is that while the delayed luminance signal phase is the same as the direct signal phase, the chrominance signal phase is inverted, so adding the delayed signal to the direct signal extracts only the luminance signal, and subtracting it extracts only the chrominance signal component. is about to be taken out. However, IH refers to one horizontal opening period. Recently, a 3-line comb filter system as shown in Figure 4 has also been used in place of the 2-line comb filter system shown in Figure 3, and in principle, it can handle vertical correlation in the same way as the 2-line comb filter system. We are using.

Here, in the circuit of FIG. 4, the direct signal 101 of the input composite video signal 100 and the IH
2H delay signal 10 by delay signal 102 and delay element 5
3 is calculated by the arithmetic circuit 6 to separate the color signal C, and this color signal C is subtracted from the IH delay signal 102 by the subtracter 7, thereby separating the luminance signal Y.

With such a conventional comb-shaped YC separation circuit, it is theoretically possible to completely separate the luminance signal and chrominance signal when there is a vertical correlation, but in reality, the delay elements used in the circuit are glass delay lines. Otherwise, variations in the gain characteristics or phase characteristics of the filter occur within the band, resulting in a difference in level or phase between the direct signal and the delayed signal. This difference in level and phase occurs particularly in the portion where the phase of the color change portion changes. Therefore, when the above phenomenon occurs, a color signal component remains in the luminance signal after separation, as shown in FIG. 5(B), and this residual color signal component and the color signal after separation become beat. This had the disadvantage that the colors appeared on the screen and the border areas of the colors became whitish.

(Problems to be Solved by the Invention) As described above, in the conventional comb-shaped YC separation circuit that separates a luminance signal and a color signal using the correlation of a composite video signal, there is a path through which the signal is directly transmitted, and a path where the signal is transmitted through a time delay path. It is difficult to match the gain characteristics and phase characteristics between the two color signals on these two paths, and therefore the color signal component remains in the separated luminance signal. As a result, the separated color signal and the residual color signal component appear as beats on the screen, deteriorating the image quality.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a comb-shaped luminance signal/chrominance signal separation circuit equipped with a circuit capable of removing residual chrominance signal components from a luminance signal separated from a composite video signal. It is said that

[Structure of the invention]

(Means for Solving the Problems) The present invention provides a comb-shaped luminance signal/chrominance signal separation circuit that separates a luminance signal and a chrominance signal from a composite video signal by utilizing their vertical correlation, in which the luminance signal is delayed by a predetermined horizontal synchronization period. a signal delaying means for subtracting the luminance signal delayed by the signal delaying means from the luminance signal to extract a residual color signal component; and extraction by the first subtraction means from the luminance signal. and second subtraction means for subtracting the residual color signal component.

(Operation) In the comb-shaped luminance signal/chrominance signal separation circuit of the present invention, the signal delay means delays the luminance signal by a predetermined horizontal synchronization period. 1st
The subtracting means subtracts the luminance signal delayed by the signal delaying means from the luminance signal to extract a residual color signal component. The second subtraction means subtracts and removes the residual color signal component extracted by the first subtraction means from the luminance signal.

(Embodiment) Hereinafter, an embodiment of the great invention will be described with reference to the drawings. Fig. 1 is a block diagram showing an embodiment of the comb-shaped luminance signal/chrominance signal separation circuit of the present invention.

) 11') A comb-shaped YC separation circuit that separates a luminance signal Y and a chrominance signal C from the composite video signal by utilizing the correlation of the composite video signal, 12'., Luminance signal ? A delay element that delays LH (or 2H), 13 a subtracter that subtracts the luminance signal delayed by the delay element 12 from the luminance signal Y, 14 an amplifier that amplifies the output of the subtracter 13, and 15 a subtracter that subtracts the luminance signal delayed from the luminance signal Y by the amplifier 14. This is a subtracter that subtracts the output signal of . Note that the part indicated by the broken line in the figure is the comb-shaped filter, which is the main part of the present invention.

Here, the delay element 12 constitutes a signal delay means, the subtracter 13 constitutes a first subtraction means, and the subtracter 15 constitutes a second subtraction means.

Next, the operation of this embodiment will be explained. When a composite video signal 100, such as that shown in FIG. 2A, is input to the comb-shaped YC separation circuit f\fill, the luminance signal Y and color signal C are separated according to the principle described in the conventional example.

Here, since the comb-shaped YC separation circuit 11 is configured to utilize vertical correlation, there is always a path through which the input signal is directly transmitted and a path passing through an IH or 2H delay element. Since it is practically difficult to completely match the gain characteristics and phase characteristics of these two paths,
The gain characteristics and phase characteristics are matched only near the center frequency of the color. Therefore, in the discontinuous part of the color phase, both the gain and phase characteristics are inconsistent in both paths, and the color signal component leaks into the luminance signal Y at the color change part as shown in FIG. 2(B). It gets complicated.

The luminance signal Y containing such residual color signal components is delayed by IH or 2H by the delay element 12 and output to the subtracter 13. Therefore, the subtracter 13 receives the directly input luminance signal Y
Since the luminance signal Y delayed by IH or 2H is subtracted from the signal, the residual color signal component described above is extracted here. This residual color signal component is output to a subtracter 15 via an amplifier 14. This subtracter 15 converts the residual color signal as shown in FIG. 2(C) inputted via the amplifier 14 from the luminance signal Y shown in FIG. 2(B) outputted from the comb-shaped YC separation circuit 11. Since the components are subtracted, the result of the subtraction becomes a luminance signal containing no residual color signal as shown in FIG. 2 (D>), and is output to the next stage.

According to this embodiment, the residual color signal component is removed by passing the luminance signal containing the residual color signal component separated by the comb-shaped YC separation circuit 11 through a comb-shaped filter as shown by the broken line in FIG. Since no color signal components leak into the final luminance signal, the beat between the residual color signal and color signal C that occurs on the screen is reduced, improving image quality. I can do it.

〔Effect of the invention〕

As described above, according to the comb-shaped luminance signal/chrominance signal separation circuit of the present invention, residual chrominance signal components can be removed from the luminance signal separated from the composite video signal.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the comb-shaped luminance signal/chrominance signal separation circuit of the present invention, FIG. 2 is a diagram showing an example of operating waveforms of the circuit shown in FIG. 1, and FIGS. FIG. 4 is a block diagram showing an example of a conventional comb-shaped YC separation circuit, and FIG. 5 is a diagram showing an example of operating waveforms of the circuit shown in FIG. 3 or FIG. 4. 11... Comb-shaped YC separation circuit 12... Delay element 13.15... Subtractor

Claims (1)

[Claims] In a comb-shaped luminance signal/chrominance signal separation circuit that separates a luminance signal and a chrominance signal from a composite video signal by utilizing their vertical correlation, a signal delaying means for delaying the luminance signal by a predetermined horizontal synchronization period; a first subtraction means for subtracting the luminance signal delayed by the delay means to extract a residual color signal component; and a first subtraction means for subtracting the residual color signal component extracted by the first subtraction means from the luminance signal. 2. A comb-shaped luminance signal/chrominance signal separation circuit comprising: 2 subtraction means.