JPH04150492A - Video noise reduction circuit - Google Patents

Abstract

PURPOSE:To eliminate the need of a notch filter control circuit so as to reduce the cost of the video noise reduction circuit by providing a notch filter for removing the component of chrominance signals mixed with luminance signals in the high-frequency component signal processing circuit of a coring circuit. CONSTITUTION:A low-pass filter 4 separates the low-frequency component of input signals and inputs the separated component to an adder circuit 6 and a high-pass filter 2 separates the high-frequency component of the input signals and inputs the separated component to a coring circuit 3. The circuit 3 outputs the high-frequency component to a notch filter 5 after reducing the noise level superimposed upon the high-frequency component by coring and the filter 5 outputs the high-frequency component to the adder circuit 6 after reducing 5.58-MHz chrominance signal component. A switch 7 selectively outputs the output of the circuit 6 or input signals from an input terminal 1 by switching.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a signal reproducing circuit for video equipment, and in particular to a method for obtaining a high-quality reproduction screen by reducing noise contained in high frequency components of a luminance signal. The present invention relates to a video noise reduction circuit that makes it possible to reduce noise.

[Conventional technology]

A conventional video noise reduction circuit uses a circuit having the configuration shown in the block diagram of FIG. The low-pass filter 4 separates the low-frequency components of the input signal and inputs them to the adding circuit 6, and the high-pass filter 2 separates the high-frequency components of the input signal to the coring circuit 3.
The coring circuit 3 performs coring to reduce the noise superimposed on the high frequency portion, and outputs the resulting signal to the adder circuit 6. The switch 7 switches between the luminance signal input and the input from the adder circuit, outputs the signal, and inputs it to the notch filter 10. 10 is provided with a control circuit 11 between the notch filter 10 and the ground, and by making the connection between the notch filter 10 and the ground conductive, the notch filter 10 reduces the color signal component contained in the luminance signal. When the control circuit 11 cuts off the connection between the notch filter 10 and the ground, the brightness signal from the switch 7 is output to the output terminal 8. I was trying to get it to be output.

[Problem to be solved by the invention]

The present invention improves the notch filter control circuit by inserting a notch filter that removes color signal components mixed into the luminance signal into a video noise reduction circuit that reduces noise superimposed on the high frequency portion of the luminance signal. The purpose is to reduce costs by deleting them.

[Means to solve the problem]

As shown in FIG. 1, there is a circuit that branches a luminance signal input and inputs it to a low-pass filter 4, a high-pass filter 2, and one end of a switch 7, and a circuit that separates low frequency components of the input signal by the low-pass filter 4. The high-frequency component of the input signal is separated by the circuit input to the adder circuit 6 and the high-pass filter 2 and input to the coring circuit 3, and the coring circuit 3 performs coring to superimpose it on the high-frequency component. a circuit that reduces and outputs the noise contained in the luminance signal and inputs it to the notch filter 5, which reduces and outputs the color signal component mixed in the luminance signal with the notch filter 5, and inputs it to the addition circuit 6; The adding circuit 6 adds the signal from the low-pass filter 4 and the signal from the notch filter 5 and outputs the result to the other end of the switching device 7, and switches between the luminance signal input and the input from the adding circuit 6. It is configured to remove noise superimposed on the high frequency portion of the luminance signal and color signal components mixed in the luminance signal.

[Effect]

With the above-described configuration, the present invention reduces the 3°58 MHz component of the color signal mixed into the luminance signal and the noise component superimposed on the high frequency portion of the luminance signal,
If the dot interference caused by the mixing of the color signal into the luminance signal is noticeable in the reproduced image, or if the noise is noticeable in the reproduced image, switch 7 shown in FIG. By setting the signal to be output, the dot interference or noise can be reduced and the screen can be made easier to view.If the dot interference or noise is not noticeable, switch 7 can be switched to input terminal 1. By allowing the added luminance signal input to be output as is from the switch 7, a reproduced image with normal resolution can be obtained. This eliminates the conventional notch filter control circuit and reduces costs. It becomes possible to aim at reduction.

〔Example〕

FIG. 1 is an electric circuit block diagram of a video noise reduction circuit showing an embodiment of the present invention. For example, a luminance signal separated by a Y/C separation circuit is applied to the circuit via an input terminal 1. , the input signal from the input terminal 1 is branched and input to one end of a low pass filter 4, a high pass filter 2, and a switching device 7.

The low-pass filter 4 separates the low-frequency components of the input signal and inputs them to the adder circuit 6. The high-pass filter 2 separates the high-frequency components of the input signal and inputs them to the coring circuit 3. By performing coring, the noise level superimposed on the high frequency part is reduced and output and input to the notch filter 5. The notch filter 5 reduces the 3.58 MHz color signal component and outputs it. It is input to the adder circuit 6.

The adder circuit 6 adds the low frequency component output from the low-pass filter 4 and the high frequency component signal output from the notch filter 5, outputs the sum, and inputs the sum to the other end of the switch 7. In this case, the output from the adder circuit 6 and the input signal from the input terminal 1 can be switched and output.

FIGS. 2(a) to 2(f) are explanatory diagrams showing the frequency characteristics of each part same as above, where the vertical axis shows the signal level and the horizontal axis shows the frequency.

FIG. 2(a) shows the frequency characteristics of the luminance signal applied to the switching device 7, and the luminance signal is directly inputted to the switching device 7 from the input terminal 1 to obtain a flat characteristic.

FIG. 2(c) shows a frequency characteristic showing the output of the high-pass filter 2, which reduces the signal level of low frequency components.

Fig. 2 (C) shows the frequency characteristics showing the output of the coring circuit 3. Coring was performed to reduce the noise superimposed on the high frequency components and also to reduce the signal level of the high frequency components. It has become a characteristic.

FIG. 2(d) is a frequency characteristic showing the output of the notch filter 5, which is a characteristic in which the 3.58 MHz color signal component mixed in the luminance signal is reduced.

FIG. 2(e) shows a frequency characteristic showing the output of the low-pass filter 4, which reduces the signal level of high frequency components.

FIG. 2(f) shows a frequency characteristic showing the output of the adder circuit 6, which is a total frequency characteristic obtained by adding the output of the notch filter 5 and the output of the low-pass filter 4.

In the above-mentioned embodiment, the notch filter 5 is provided between the coring circuit 3 and the adding circuit 6;
It may be provided between the high-pass filter 2 and the high-pass filter 2, or it may be provided between the high-pass filter 2 and the branch point of the input signal from the input terminal 1.

〔Effect of the invention〕

As explained above, according to the present invention, a notch filter for removing color signal components mixed in the luminance signal is provided in the signal processing circuit for high frequency components of the coring circuit,
If dot interference caused by the mixing of color signals into the luminance signal is noticeable in the reproduced image, or if noise components superimposed on the high frequency portion of the luminance signal are noticeable in the reproduced image, the luminance is reduced through a video noise reduction circuit. If the dot interference or noise is not noticeable, you can switch the switch so that the luminance signal is output without going through the video noise reduction circuit. Cost reduction can be achieved by eliminating the filter control circuit.

[Brief explanation of drawings]

FIG. 1 is an electric circuit block diagram of a video noise reduction circuit showing an embodiment of the present invention, and FIGS. 2(a) to (f)
3 is an explanatory diagram showing the frequency characteristics of each part of the same as above, and FIG. 3 is an electric circuit block diagram of a conventional video noise reduction circuit. 1-----Manual fitter, 2...-high pass filter, 3 coring circuit, 4--low pass filter, 5
．． 10...notch filter, 6- adder circuit, 7
- Switcher, 8- Output terminal, 11 - Control circuit. Patent applicant: Fujitsu General Ltd.

Claims (1)

[Claims] (1) a circuit that branches a luminance signal input and inputs it to a low-pass filter, a high-pass filter, and one end of a switch; a circuit that separates a low frequency component of the input signal using the low-pass filter and inputs it to the adder circuit; The high-frequency components of the input signal are separated using a high-pass filter and input to the coring circuit, which performs coring to reduce the noise superimposed on the high-frequency components and output the resulting notch filter. a circuit that reduces the color signal component mixed in the luminance signal with the same notch filter and outputs it and inputs it to the addition circuit, and adds the signal from the low-pass filter and the signal from the notch filter. A video noise reduction circuit comprising: an adder circuit that outputs the brightness signal to the other end of the switch; and a switch that switches between the luminance signal input and the input from the adder circuit and outputs the signal.