JPS59151592A - Separating circuit of luminance signal and chrominance signal - Google Patents

Abstract

PURPOSE:To prevent the deterioration in resolution by converting low frequency component of a video signal into a luminance signal and high frequency component into a chrominance carrier signal when there exists no correlativity in the video signals of adjacent horizontal scanning lines. CONSTITUTION:An input signal H0, a 1H delay signal H1, and a 2H delay signal H2 are formed by 1H delay lines 10 and 11, (2H1+H0+H2)/4 signal H, (H1+ H2)/2 signal I and (H1+H2)/2 signal J are obtained by adders 12, 14, 22 and amplifiers 16, 17, 23 having a gain of 1/2, (2H1-H0-H2)/4, (H1-H2)/2 and (H1-H0)/2 signals are obtained by subtractors 13, 15, an adder 24 and amplifiers 19, 20, 25 respectively. When the low frequency component of the (H1-H2)/2 or (H1-H0)/2 is not detected, it is judged no correlativity is held between the video signals, and the low frequency component of the H1 signal is outputted as a luminance signal, and the high frequency component is outputted as the chrominance carrier component.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a luminance signal and chrominance signal separation circuit, particularly for color TV (television) receivers! The present invention relates to a separation circuit that separates a BIi degree signal and a carrier color signal.

The frequency spectrum of the color video signal of the NTSC system is shown in Fig. 1 (A), where Y is the luminance signal band and C is the carrier chrominance signal band, and the high range of the luminance component is a part of the carrier chrominance signal band. overlaps with

In order to separate these two signal components from each other, it has been common practice to use filters with appropriate pass characteristics, as shown in FIGS. 3(B) and 3(C), respectively. By making the characteristics of the low-pass filter shown in Figure (B) narrower than the original luminance signal band J, we are trying to reduce so-called dot interference caused by the mixture of carrier color signals. The lack of this results in a decrease in resolution. Also, in the band-pass filter shown in Figure (C), by making the band narrower than the original band of the carrier color signal,! ! This is intended to reduce cross-color interference due to the mixing of high-frequency components of the i-degree signal. However, the color resolution is reduced due to the deletion of high frequency components of the color difference signals.

In order to eliminate this drawback, a so-called comb filter is used, and FIG. 2 is a block diagram thereof. The input video signal (B) is input to a 1H delay device 1 (1 represents one horizontal scanning period), an adder 2, and a subtracter 3, and the output (A) of this delay device 1 is input to the adder 2. and subtractor 3
Each person has become a force. The respective outputs of these adders/subtractors 2 and 3 become a luminance signal (C) and a carrier color signal through amplifiers 4 and 5, respectively, each having a gain of 1/2.

Explanation of operationIn other words, in the color video signal of the NTSC system, the luminance signals between successive scanning lines are set to be in phase, and the carrier color signals are set to be in opposite phase.
When a signal applied to the input IN of the comb filter shown in FIG. 2 is applied, the current signal (B
) and an immediately preceding signal (A) delayed by 1 to 1.

The adder 2 adds the current signal (B) and the previous signal (A) to cancel out the opposite phase carrier color signal, and outputs only the luminance signal (C) via the amplifier 4. In the subtracter 3, the in-phase luminance signal is canceled and only the carrier color signal is outputted via the amplifier 5. .

Figures 3 (A) to (C) are the respective signals (A) to (C) in Figure 2.
) are shown in correspondence with each other (X).

That is, currently, the 1H waveform as shown in Figure (B) is the second waveform.
Consider the case where the 11-1 waveform, which is applied to the incoming terminal IN in the figure and immediately precedes the current 1H waveform, has a waveform as shown in figure (A). At this time, the 1+1 waveform of the separated luminance signal becomes as shown in Figure (C). The applied waveform in the current diagram (B) (in contrast to the separated luminance signal (
In the waveform C), it can be seen that the second and fourth quarter portions of the 11-1 period are not correctly reproduced.

In this way, in the conventional comb filter shown in FIG. 2, the sum signal is always used as the luminance signal for the reference 11" video signal waveform and the immediately preceding 1H video signal waveform, regardless of the correlation between the two. Since the difference signal is an 11th chrominance signal, the uncorrelated part (in this case, it becomes 0, where correct separation of luminance signals etc. cannot be performed).As a result, the vertical angular image angle decreases, It has the disadvantage of appearing in dot interference and cross color interference.

The present invention has been made to eliminate the drawbacks of the conventional ones as described above, and its purpose is to always perform a correct filtering action regardless of the presence or absence of correlation between video signals of adjacent horizontal scanning lines. An object of the present invention is to provide a luminance and chrominance signal separation circuit that can perform the following steps.

The separation circuit according to the present invention detects whether or not there is a correlation between video signals between a reference horizontal scanning line and predetermined horizontal scanning lines before and after the reference horizontal scanning line, and determines whether or not there is a correlation between at least some of these horizontal scanning lines. When the image signal is misused, addition and reduction processing is performed on the correlated portions, and when there is no correlation, the low-frequency and high-frequency components of the video signal of the reference horizontal scanning line are derived, respectively. , the signal subjected to addition processing and the low frequency component are outputted as a luminance signal of the reference horizontal scanning line, and the signal subjected to subtraction processing and the high frequency component are used as a carrier color signal of the reference horizontal scanning line. .

Embodiments of the present invention will be explained below with reference to FIG. In this example, scanning lines 1-10 and 1''2 are used as the adjacent front and rear scanning lines on the reference horizontal scanning line, but generally two or more are used. It's also good.

In the figure, two 1H delay devices 10 and 11 are provided in series, the input signal is <Δ), the 11" delay signal (B) and the 2H delay signal (C). input signal(
A) and the IHN extended signal (B) are sent to an adder 12 and a subtracter 13.
The 11-1 delay signal (B) and the 2H delay signal (C) are both input to another adder 14 and subtracter 15. The outputs of adders 12 and 14 are input to amplifiers 16 and 17 with a gain of 1/2, respectively, and
1” delay signal (B) is LPF (low pass filter) 1
8 is input.

The outputs of the subtracters 13 and 15 are j' amplifier 1 with a gain of 1/2.
9 and 20, respectively, and the 1H delay signal (B) is input to a BPF (band pass filter) 21. The outputs of the amplifiers 16 and 17 are added together in an adder 22 and then input to an amplifier 23 with a gain of 1/2. The outputs of the amplifiers 19 and 2o are added together in the adder 24 and have a gain of 1/
The signal is input to the amplifier 25 of No. 2.

The output (H) of the amplifier 23, the output (■) of the amplifier 17, the output LJ of the amplifier 16), and the output of the LPF 18 are respectively input to the switch 26, and these input signals are selectively derived by this switch to adjust the luminance. The signal becomes (K). In addition, amplifiers 19°20 and 25 and B P ]-12
1 are input to a switch 27, and these input signals are selectively derived by this switch to become a carrier color signal.

A switch driver 28 is provided for switching control of both switches 26 and 27, and the output (G) of the LPF 29
and the output l:) of the LPF 30 to generate a switch control signal.

The input of LPF29 is the output (G) of amplifier 19, and L
The input of PF30 is the output (D) of amplifier 2o.

In such a configuration, four of the brightness signal selection switches 26
Two input terminals have signals (T1) and (21-1++
Ho−+−t12>/4, as signal (1) (tr+
'+112)/2, (11-1-1o)/2 as the signal Ll), and the signal H1 passed through the LPF 18 are supplied. In addition, the four input terminals of the carrier color signal selection switch 27 are (2H'-HO-82>/4, ()I+ -t-12) in order from the top.
)/2, (H+-Ho)/2 and BPF2 of signal 11
This means that what has passed through 1 is being supplied.

In addition, two-man power (E) and (G) of the switch driver 28
As, <1-I+ -H2)/2 and (1-1
+-l-1o)/2 low-frequency components are respectively used. These (t1l-H2)/2 and (1-
The difference signal 1'+ -Ho)/2 is used to detect the presence or absence of correlation between scanning lines, and the low frequency component (hereinafter referred to as L12) of (H+ -H2) is not detected. If L12 is detected, it is determined that there is a correlation between the signals 111 and 112 of the defining scan line, and that there is no correlation if L12 is detected.

Similarly, the low frequency component 1 of (1-1+-f-to). , 1G is not detected (circular scanning line signal 1) If 1G is not detected, there is a correlation between 1 and Ho, and if L10 is detected, it is determined that there is no correlation.

In order to separate the luminance signal and the carrier color signal, it is necessary to perform addition/subtraction processing on only the correlated signals, so the switch driver 28 uses switch 26 and 2
7 is controlled as follows.

In other words, when both L12.1-10 are not detected, HHI has a correlation with both H2 and G1o, so y-
Switch so that outT becomes (2H1→river"o+Hz)/4 and C-0UT becomes (2H+t"o H2)/4. When only L+o is detected, 1-11 and H2
Correlation with 1fi a;j) If Y-OUT is (1
'1+Hz)/2, C-0(JT is (
)-1t-H2)/2. Also,
If only 112 is detected, there is a correlation between 111 and Ha, so Y-OUT
)'/2, C-0UT is controlled to be (H+ -Ho)/2, and when L12°110 is detected together, 11 has no correlation with Ho and 112, so Y-OL
J T ;/fi L P F 18 output Hl
The brightness signal of C-0UT is the output of BPF21.
It is controlled so that it becomes a + carrier color signal component.

FIGS. 5(A) to (K) respectively show examples of waveforms of the block signals (A) to (K) of the block 1 in FIG. 4, and the reference scanning line signal H1 is (B )'C'', and the signals I'o and H2 of the adjacent front and rear scanning lines are (A) and (
This is an example of a waveform as shown in C). 1st on scan line
In the quarter part, neither 112°L +a is detected, so Y-OUT is (2+-(11kawa-1o+l)2)/2
And since L 10 is detected in the second quarter,
Y-OUT is (1-I + 12)/2, and the third
Since L 12 is detected in the quarter part, (f-1t +
Ho > / 2, and in the fourth quarter L + 2
．． Since both 1+o are detected, Y-OUT is L of G11.
The signal is passed through PF18. Therefore, the luminance component shown in Figure (K) is extracted and a waveform equal to the reference horizontal scanning line signal H1 is obtained.

In the above embodiment, two delay devices are used to set one scanning line before and after the reference scanning line, but in general, a large number of delay devices are used to increase the number of scanning lines before and after the reference scanning line. Two or more may be used.

As described above, according to the present invention, it is possible to always separate the correct luminance signal and carrier color signal regardless of whether or not there is a correlation between signals between adjacent horizontal scanning lines, so that high-quality color images can be reproduced. becomes.

[Brief explanation of the drawing]

Fig. 1 is a characteristic diagram illustrating an example of a conventional luminance signal and chrominance signal separation circuit, Fig. 2 is a block diagram of an example of a conventional comb filter, and Fig. 3 is an example of the operating waveform of the filter shown in Fig. 2. 4 is a circuit diagram of an embodiment of the present invention, and FIG. 5 is a diagram showing an example of operation waveforms of each part of the circuit of FIG. 4. Explanation of symbols of main parts 10.11...1-day delay unit 12.14, 22.24...Adder 13.15
......Subtractor 18, 29.30...LPF21...
・BPF 26...Brightness signal selection switch 27...
...Transportation color signal selection switch 28...Switch driver Applicant Pioneer Co., Ltd. Agent Patent attorney Motohiko Fujimura Jo 7 Diagram 2I ¥] Figure L3

Claims (1)

[Claims] means for detecting the presence or absence of a correlation in video signals between a reference horizontal scanning line and horizontal scanning lines of predetermined water before and after the reference horizontal scanning line; means for deriving a signal subjected to addition and subtraction processing for the correlated portion of the video signal of the horizontal scanning line that is correlated with at least a part of the video signal of the horizontal scanning line; means for deriving low-frequency and high-frequency components of the video signal of the reference horizontal scanning line when the brightness is not detected; A metering signal and color signal valve IT circuit configured to use the subtraction processed signal and the high frequency component as a carrier color signal for the reference horizontal scanning line.