JPS60145786A - Noise suppression circuit of color video signal - Google Patents

Abstract

PURPOSE:To decrease waveform distortion due to high-band suppression by forming a horizontal outline signal which corresponds to the drastically changed part of a luminance signal, and by suppressing the noise except the noise of the horizontal outline part. CONSTITUTION:The signal which is supplied to an input terminal 21 is differentiated by the first high pass filter 22, and the signal becomes the pulse in the regular direction by the first clip circuit 23. The differential waveform is phase-inverted by a signal inversion circuit 24, and the pulse in the regular direction is obtained by the second clip circuit 26. For these pulses, the horizontal outline signal where the pulse in the regular direction corresponds to the horizontal scanning position which corresponds to the drastically changed part of the waveform of the luminance signal is formed by a waveform synthesizer 25. Gains of respective gain control circuits 34 and 44 decrease only for the regular-direction pulse period.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a noise suppression circuit for color video signals, and more particularly, to an improvement of the noise suppression circuit that reduces noise by suppressing high-frequency components of color signals. .

[Technical background of the invention]

In recent years, color imaging devices that can frequency-separate and extract luminance signals and color signals from incident light are known. As a specific means for performing such frequency separation, for example, strike 2-wave filters having different inclinations with respect to the scanning direction are bonded to the photoconductive target, and a predetermined color complement code corresponding to the spatial frequency by the strike 1 filter is lowered. It is formed as a color video signal included in a luminance signal which is a range signal.

The color video signal thus obtained is such that predetermined color signals, for example, a red signal and a blue signal, are modulated with their respective high frequencies, and the phase changes by 1000 for each horizontal scanning line. These colorimetric signals are then separated from the color video signal.

In this separation process, first, a colorimetric signal occupying a predetermined band is extracted using a bandpass filter, and then this signal is delayed by a delay line for one horizontal scanning period. Thus, by adding and detecting the delayed signal and the non-delayed signal, a green signal is obtained, and by subtracting and detecting the delayed signal and the non-delayed signal, a red signal is obtained. Furthermore, the luminance signal is separated by a low-pass filter. Furthermore, when displayed on television or recorded, it is encoded into a predetermined signal format.

In the above-mentioned color imaging device, the color signal has more noise than the low-band luminance signal, and in order to suppress this noise, a noise suppression circuit shown in FIG. 1 has conventionally been used.

FIG. 1 is a block diagram showing one channel of separated color signals. For example, a red signal is input to input terminal 1, and terminal 1 is connected to a low-pass filter 2 and a bypass filter 3. ing. Then, the red that passed through the No. 1 bus filter 3 (the high frequency component of the
The signal is inputted to the adder circuit 5 through the low level suppression circuit 4.

This additional circuit 5 is supplied with the low-frequency components of the red signal that have passed through the low-pass filter 2, and the high-frequency components of the red signal are applied with a low-level suppression circuit 4 to provide a noise-free red signal. It is designed to be derived from the adder circuit 5 as a signal.

[Problems with background technology]

However, according to the above-mentioned conventional circuit, when the high-frequency component of the red signal passes through the low-level suppression circuit 4, the entire high-frequency component is not suppressed, but is added to the low-frequency component in the adder circuit 5 at the next stage. Compared to the original red signal, the signal had a better signal-to-noise ratio, but had the problem of increased waveform distortion.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances, and provides a noise suppression circuit for color video signals that is capable of suppressing only the noise from the high-frequency components of color No. 48 that are frequency-separated from the luminance signal. The purpose is to provide.

[Summary of the invention]

The present invention forms a horizontal contour signal corresponding to a sharply changing portion of brightness IM' (M), and uses this horizontal contour signal to suppress noise other than the horizontal contour portion that contains many high-frequency components of color I. This is a circuit that reduces waveform distortion due to high frequency suppression.

[Embodiments of the invention]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to illustrated embodiments. Here, FIG. 2 is a block diagram showing a noise suppression circuit according to an embodiment of the present invention, and FIG. 3 is a waveform diagram for explaining the operation of FIG. 2.

This embodiment is a circuit that suppresses noise in a color video signal in which each color signal (for example, a red signal and a blue signal) and a luminance signal are separated in frequency, and is used in a color imaging device using a vidicon or a solid-state imaging device. 6 is suitable.

That is, the noise suppression circuit according to this embodiment includes a signal forming means 11 for forming a horizontal contour signal from a luminance signal, and first and second color signal circuits 12 and 13 whose gain is controlled by the horizontal contour signal. It is structured.

In the signal forming means 11, a luminance signal is input to an input terminal 21, and this input terminal 21 is connected to a first clip circuit 23 and a signal inversion circuit 24 through a first bypass filter 22, respectively. . The output of the first clip circuit 23 is supplied to one input terminal of the waveform synthesizer 25, and the output of the signal inversion circuit 24 is supplied to the other input terminal of the waveform synthesizer 25 via the second clip circuit 26. It is designed to be supplied to the input terminal. This is a corrugated table. The luminance signal input terminal 21 is led to the next stage through a delay circuit 28 for matching the phase (delay time) of each color signal, which is the luminance signal.

Further, in the first color signal circuit 12, a red signal, for example, is input to an input terminal 31, and the same terminal 31 is connected to a second bypass filter 32 and a first low-pass filter 33.
It is connected to the. And the second bypass filter 3
The output of No. 2 is supplied to a first gain control circuit 34 having a gain control terminal 34a. This gain control terminal 34
The output of the waveform synthesizer 25 is applied to a, and the gain control circuit 34 whose gain is controlled by the same output
The output of is supplied to one input terminal of the first adder 35. On the other hand, the output of the first low-pass filter 33 is supplied to the other input terminal of the first adder 35 and added to the gain-controlled signal. This first adder 35 provides a red signal with suppressed noise according to the present invention.

Next, the second color signal circuit 13 has an input terminal 41K to which, for example, the ^ signal is input, and the terminal 41 is connected to a third bypass filter 42 and a second low-pass filter 43. The output of the third I-pass filter 42 is transmitted to a gain control circuit 44 having a gain control terminal 44a.
is supplied to.

The output of the waveform synthesizer 25 is applied to this gain control terminal 44a, and the first and second gain control circuits 34.44 receive equal gain control using the same control signal. become. Further, the output of this second gain control circuit 44 is supplied to one input terminal of a second adder 45. On the other hand, the output of the second low-pass filter 43 is supplied to the other input terminal of the second adder 45,
It is added to the signal controlled by the second gain control circuit 44. The second adder 35 extracts the green signal from which noise has been removed according to the present invention.

The operation of the circuit of the present invention configured as described above will be explained below. In FIG. 3, (a) shows the luminance signal waveform,
In FIG. 2, it is supplied to input terminal 21. This signal is converted into a differential waveform as shown in waveform (b) by the first pass filter 22, and this differential waveform is converted into a differential waveform as shown in FIG. ) is the positive direction pulse Pl shown in FIG. Also,
The phase of the differential waveform is inverted by the signal inverting circuit 24, resulting in a signal whose polarity is inverted as shown in FIG. 3(d). When this inverted signal passes through the second clipping circuit 26, it becomes a waveform of only the positive direction pulse P2 with the negative direction pulse clipped, as shown in FIG. 3(e). These third waveforms 1(c) and 1(e) are synthesized by the waveform synthesizer 25, and a positive direction cross P 1 r P z is generated at the horizontal scanning position corresponding to the rapid waveform change portion of the luminance signal. A corresponding horizontal contour No. 18 (see FIG. 3(f)) is formed.

The horizontal contour signal thus formed is applied to each gain control circuit 34, 44 of the first and second color signal circuits 12, 13, and the first gain of each gain control circuit 34, 44 is applied to the positive direction pulse. Decrease only the period. On the other hand, in Prtl and the second color signal circuit 12.13, as shown in FIG. 3(g),
Each color signal power including noise N as shown in (J,)! is input. The high frequency components of each color signal are passed through the second and third no-bus filters 32, 42, and 21'!
The high-frequency component waveforms for each color signal are as shown in Figure 3 (++) and H. Each of these high-frequency component waveforms has a portion p3 that contains many high-frequency components. P4 (color change part)
corresponds in position to the waveform changing portion of the luminance signal during one horizontal scanning period, that is, to the positive direction crosses PI, Pa, and the forward direction noxles Pl, Pg change the waveform of each gain control circuit 34, 44. By lowering the gain, it is possible to suppress the noise N included during the horizontal scanning period except for the high-frequency color portions Ps and Pa.

The output waveforms of each gain control circuit 34 and 44 obtained by this are shown in FIGS. 3(i) and 3(n).

Furthermore, the low frequency components of each color signal are expressed as the 31st fi (j),
A waveform as shown in (o) is derived from the first and second low-nos filters 33 and 43. These low frequency components (j) and (o) and each of the gain control circuits 34.4
4 output waveform (i), - is sent to the first and second adder 35
．． 45, each color signal becomes a signal that is faithful to the original signal waveform and has no waveform distortion due to high-frequency degradation (Fig. 3 (k)
.

(see Φ).

In this manner, the present invention can reduce only noise without degrading the necessary high frequencies in a noise suppression method that suppresses high frequencies to reduce external sounds.

〔Effect of the invention〕

As explained above, according to the present invention, only the noise can be suppressed without deteriorating the high-frequency components of the color signal separated for the chest wave number of luminance A3, so that the signal waveform can be faithfully reproduced. It is possible to obtain a color video signal with reduced noise without causing distortion.

4 drawings',) 1++l il'i, 7. C+j)'
1) Block 1 shows a noise suppression circuit for a color video signal from tL, and FIG. 2 shows an embodiment of the present invention.a) Block 1 shows a noise suppression circuit for a color video signal.
Figures 1 and 2 are dynamic waveforms 1 for explaining the operation of Figure 2.

11... Signal forming means, 12.13... Color signal circuit, 22.32.42... Bypass filter, 23.26
... Clip circuit, 24 ... Signal inversion circuit, 25
... Waveform synthesizer, 33.43 ... Low pass filter, 34.44 ... Gain control circuit, 35.45 ... Adder.

Claims (1)

[Claims] fil A noise suppression circuit for a color video signal that suppresses noise from a color signal that is frequency-separated from a luminance signal, which inputs the luminance signal and performs noise suppression based on its high frequency component. a signal forming means for forming a horizontal contour signal corresponding to a luminance changing portion; a filter means for inputting the color signal and extracting a low frequency component and a high frequency component thereof; a high frequency component for the filter means; , comprising gain control means to which the horizontal contour signal of the signal forming means is applied as a gain control signal, and addition means for inputting and adding the output of the gain control means and the low frequency component of the filter means, respectively, 1. A noise suppression circuit for a color video signal, characterized in that a color video signal is extracted from which a color signal high-frequency component is gain-controlled by a horizontal contour signal.