JPH04103287A - Luminance signal and chrominance signal noise reduction circuit - Google Patents

Abstract

PURPOSE:To reduce noise in a luminance signal without causing unsharpened contour in the vertical direction and after-image even for a moving picture by controlling optimizingly the attenuation of three attenuators in response to the degree of correlation for one frame and for one horizontal scanning period of an input luminance signal. CONSTITUTION:When the correlation for one frame is small like a moving picture, the attenuation in an attenuator 15 of a frame type noise reduction circuit (a) is increased to prevent after-image caused by the circuit (a) and the reduction in the noise reduction effect is compensated by decreasing the attenuation of an attenuator 19 of a line type noise reduction circuit (b) so as to increase the noise reduction effect. In this case, when the correlation for one horizontal scanning period of the signal is small, the attenuation of the attenuator 19 is increased to prevent unsharpened contour in the vertical direction caused by the circuit (b) and to compensate the reduction in the noise reduction effect by decreasing the attenuation of an attenuator 23 of coring type (c) and increasing the noise reduction effect. Thus, noise is reduced to a moving picture without causing after-image and unsharpened contour in the vertical direction.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a luminance signal and color signal noise reduction circuit for a color television receiver or a video signal recording/reproducing device having a digital video processing device.

2. Description of the Related Art In recent years, digital technology has been introduced into television receivers at a remarkable rate, and in particular, brightness signal and chrominance signal noise reduction circuits using digital memories are often used.

Hereinafter, an example of the conventional luminance signal noise reduction circuit and color signal noise reduction circuit described above will be explained with reference to the drawings.

FIG. 3 shows a block diagram of a conventional luminance signal noise reduction circuit. In FIG. 3, 1 is a one-frame delay circuit that delays the input luminance signal by one frame period, 2 is a subtracter that subtracts the input luminance signal from the output of the one-frame delay circuit 1, and 3 is attenuated the output signal of subtracter 2. Attenuator, 4 is attenuator 3
5 is a frame correlation detector that detects the correlation between one frame of the input luminance signal using the output of the subtracter 4, and 6 is attenuated by the output of the frame correlation detector 5. This is a gain control circuit that adjusts the amount of attenuation of the device 3.

Regarding the luminance signal noise reduction circuit configured in this way,
The operation will be explained below.

First, the input luminance signal passes through the adder 4 and is delayed by one frame period by the one frame delay circuit 1.

Next, a subtracter 2 takes the difference between the input luminance signal and the input luminance signal delayed by one frame, and extracts the uncorrelated part between one frame of the input luminance signal, that is, the noise component.

Since the polarity of this noise component is inverted with respect to the input luminance signal, the adder 4 adds this to the input luminance signal to reduce the noise component.

However, as it is, in the case of a luminance signal that has a correlation between frames such as a still image, the output of subtracter 2 will be only a noise component, but in the case of a moving image, since there is no correlation between frames, the output of subtracter 2 will be At the same time as the noise component, uncorrelated components of the luminance signal itself appear in the output, and when these are subtracted from the input luminance signal, an afterimage phenomenon occurs, which looks like a trail when a picture moves on the screen. Therefore, a frame correlation detector 5 detects the correlation between one frame of the input luminance signal from the output of the subtracter 2, and a gain control circuit 6 adjusts the attenuation amount of the attenuator 3. In other words, if the output of the subtracter 2 is below a certain amplitude, it is assumed that there is a correlation between one frame, and the attenuation amount of the attenuator 3 is reduced to increase the noise reduction effect.
If the output of the subtracter 2 exceeds a certain amplitude, it is determined that there is no correlation between one frame, and the amount of attenuation of the attenuator 3 is increased according to the magnitude of the amplitude, thereby reducing the noise reduction effect. This minimizes the afterimage phenomenon that occurs when recording videos.

FIG. 4 shows a block diagram of a conventional color signal noise reduction circuit. In FIG. 4, 7 is a one-frame delay circuit that delays the input color signal by one frame period, and 8 is the output of the one-frame delay circuit 7 and the input color. Adder that takes the sum of signals, 9 is adder 8
10 is a subtracter that subtracts the output signal of attenuator 9 from the input color signal; 11 is a frame correlation detector that detects the correlation between one frame of input color signals using the output of adder 8; , 12 is a gain control circuit that adjusts the amount of attenuation of the attenuator based on the output of the frame correlation detector 11.

In the above configuration, the operation is as follows. First, the input color signal passes through the subtracter 10 and is delayed by one frame period by the delay circuit FI@7. Next, an adder 8 sums the input color signal and the input color signal delayed by one frame. Here, since the polarity of the color carrier wave of the input color signal is reversed every frame, the uncorrelated part between one frame of the input color signal, that is, the noise component, can be extracted by adding the two in an adder. I can do it. Since this noise component has the same polarity as the input color signal, the subtracter 10 subtracts it from the input color signal to reduce the noise component. However, as with the luminance signal noise reduction circuit, if the color signal has a correlation between frames, such as a still image, the output of the adder 8 will be only the noise component, but in the case of a moving image, the output of the adder 8 will be only the noise component. Since there is no correlation between the two, the uncorrelated component of the color signal itself appears in the output of the adder 8 at the same time as the noise component, and if this is subtracted from the input color signal, it will cause a tail when the picture moves on the screen. An afterimage phenomenon appears that looks like it has been subtracted. Therefore, a frame correlation detector 11 detects the correlation between one frame of the input color signal from the output of the adder 8, and a gain control circuit 12 adjusts the attenuation amount of the attenuator 9. In other words, if the output of the adder 8 is below a certain amplitude, it is assumed that there is a correlation between one frame, and the attenuation amount of the attenuator 9 is reduced to increase the noise reduction effect, and the output of the adder 8 is If the amplitude exceeds a certain level, it is determined that there is no correlation between frames, and the attenuation amount of the attenuator 9 is increased according to the magnitude of the amplitude to reduce the noise reduction effect. The afterimage phenomenon is kept to a minimum.

Problems to be Solved by the Invention However, with the above configuration, the noise reduction effect for moving images becomes small, but when moving from a still image to a moving image, the noise suddenly becomes noticeable, and the noise reduction effect for moving images becomes less effective. Since the effect cannot be reduced to zero, there is a problem in that an afterimage phenomenon inevitably remains.

In view of the above problems, the present invention provides a luminance signal noise reduction circuit and a chrominance signal noise reduction circuit that can provide a noise reduction effect equivalent to that of still images for moving images and at the same time provide a stable screen with almost no afterimage phenomenon. The purpose is to

Means for Solving the Problems In order to solve the above problems, the luminance signal noise reduction circuit of the present invention first includes a one-frame delay circuit that delays an input luminance signal by one frame period, and an output signal from the output of the one-frame delay circuit. a first subtracter that subtracts the input luminance signal;
a frame-type noise reduction circuit comprising: a first attenuator that attenuates the output signal of the subtracter; a first adder that sums the output signal of the first attenuator and the input luminance signal; an l-line delay circuit that delays the output luminance signal of the adder by one horizontal scanning period; a second subtracter that subtracts the output luminance signal of the first adder from the output of the l-line delay circuit; a second attenuator that attenuates the output signal of the subtracter; and a second adder that sums the output signal of the second attenuator and the output luminance signal of the first adder. a noise reduction circuit, a high-pass circuit that passes only the high-frequency component of the output luminance signal of the second adder, and an i-width restriction that passes only a small amplitude of the output signal of the high-pass circuit. a third attenuator for attenuating the output signal of the amplitude limiting circuit; and a third subtracter that subtracts the output signal of the third attenuator from the output luminance signal of the second adder. a ring type noise reduction circuit, a frame correlation detector that detects correlation between one frame of an input luminance signal, a line correlation detector that detects correlation between one horizontal scanning period, and the frame correlation detector and the line correlation detector. The attenuator includes a gain control circuit that adjusts the amount of attenuation of each of the first attenuator, the second attenuator, and the third attenuator based on the output signal of the attenuator.

Further, the color signal noise reduction circuit of the present invention includes: a one-frame delay circuit that delays an input color signal by one frame period; a first adder that sums the output of the one-frame delay circuit and the input color signal; 1 to attenuate the output signal of the adder 1.
an attenuator, a first subtracter that subtracts the output signal of the first attenuator from the input color signal, and a frame type noise reduction circuit that delays the output color signal of the first subtracter by one horizontal scanning period. a second adder that sums the output of the l-line delay circuit and the output color signal of the first subtracter; and a second adder that attenuates the output signal of the second adder. a line-type noise reduction circuit comprising an attenuator, a second subtracter that subtracts the output signal of the second attenuator from the output color signal of the first subtracter, and an output color of the second subtracter. a band cutoff circuit that cuts off only components near the color carrier of the signal; a third attenuator that attenuates the output signal of the band cutoff circuit; and a third attenuation from the output color signal of the second subtracter. A band switching type noise reduction circuit consisting of a third subtracter that subtracts the output signal of the input color signal, and a subtracter that subtracts the output signal of the input color signal.
a frame correlation detector for detecting correlation between frames;
a line correlation detector that detects the correlation in the horizontal scanning period; It is equipped with a gain control circuit that adjusts each attenuation amount.

The present invention uses the above-described configuration to detect the correlation between one frame of the luminance signal and the color signal and the correlation between one horizontal scanning period, and when the correlation between one frame is large as in a still image, frame-type noise is detected. The attenuation amount of the first attenuator of the reduction circuit is reduced to increase the noise reduction effect, and at the same time, the second attenuator of the line type noise reduction circuit and the third attenuator of the coring type or band switching type noise reduction circuit are The amount of attenuation of is set to zero.

On the other hand, when the correlation between frames is small, such as in a video, it is recommended to increase the amount of attenuation of the first attenuator of the frame-type noise reduction circuit to prevent the afterimage phenomenon caused by the frame-type noise reduction circuit. At the same time, the resulting decrease in the noise reduction effect is compensated for by reducing the amount of attenuation of the second attenuator of the line-type noise reduction circuit to increase the noise reduction effect. However, at this time, if the correlation in one horizontal scanning period of the signal is small, the attenuation amount of the second attenuator of the line type noise reduction circuit is increased to reduce the rounding of the vertical contour caused by the line type noise reduction circuit. At the same time, it compensates for the decrease in the noise reduction effect by reducing the attenuation amount of the attenuator of the coring type or band switching type noise reduction circuit and increasing the noise reduction effect.In this way, the afterimage phenomenon and vertical The same noise reduction effect as for still images can be obtained even for moving images without causing rounding of the directional contours.

In addition, in the case of a configuration with only a frame-type noise reduction circuit and a line-type noise reduction circuit, the correlation between one frame of the luminance signal and the color signal and the correlation between one horizontal scanning period are detected, and the correlation between one frame and one horizontal scanning period is detected like a still image. If the correlation is large, the attenuation amount of the first attenuator of the frame-type noise reduction circuit is reduced to increase the noise reduction effect, and at the same time, the attenuation amount of the second attenuator of the line-type noise reduction circuit is made zero. On the other hand, when the correlation between frames is small, such as in a video, it is recommended to increase the amount of attenuation of the first attenuator of the frame-type noise reduction circuit to prevent the afterimage phenomenon caused by the frame-type noise reduction circuit. At the same time, the decrease in the noise reduction effect caused by this is compensated for by reducing the attenuation amount of the second attenuator of the line type noise reduction circuit and increasing the noise reduction effect. This results in a noise reduction effect equivalent to that of still images.

Furthermore, in the case of a configuration consisting of only a frame-type noise reduction circuit and a coring-type or band-switching type noise reduction circuit, the correlation between one frame of luminance signals and color signals and the correlation between one horizontal scanning period are detected, and the correlation between still images is detected. When the correlation between one frame is large as in the case of
Set the attenuation amount of the attenuator to zero. On the other hand, when the correlation between frames is small, such as in a video, it is recommended to increase the amount of attenuation of the first attenuator of the frame-type noise reduction circuit to prevent the afterimage phenomenon caused by the frame-type noise reduction circuit. At the same time, the resulting decrease in the noise reduction effect is compensated for by reducing the amount of attenuation of the second attenuator of the coring type or band switching type noise reduction circuit to increase the noise reduction effect. In this way, it is possible to obtain the same noise reduction effect for moving images as for still images without causing an afterimage phenomenon or vertical contour dulling.

Furthermore, in the case of a configuration consisting of only a line type noise reduction circuit and a coring type or band switching type noise reduction circuit, the correlation of the luminance signal and color signal in one horizontal scanning period is detected, and if the correlation in one horizontal scanning period is large, In this method, the attenuation amount of the first attenuator of the line type noise reduction circuit is reduced to increase the noise reduction effect, and at the same time, the attenuation amount of the second attenuator of the coring type or band switching type noise reduction circuit is reduced to zero. . On the other hand, if the correlation for one horizontal scanning period is small, the amount of attenuation of the first attenuator of the line-type noise reduction circuit is increased to prevent the rounding of the vertical contour caused by the line-type noise reduction circuit. At the same time, the resulting decrease in the noise reduction effect is compensated for by reducing the amount of attenuation of the second attenuator of the coring type or band switching type noise reduction circuit to increase the noise reduction effect.

In this way, it is possible to obtain the same noise reduction effect for the vertical contour portion as for other portions without causing any rounding of the vertical contour.

EXAMPLE An example of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a luminance signal noise reduction circuit according to an embodiment of the present invention. In FIG. 1, 13 is a one-frame delay circuit that delays the luminance signal by one frame period;
15 is an attenuator that attenuates the output signal of the subtracter 14, and 16 is an adder that adds the output signal of the attenuator 15 and the input luminance signal. , these 13 to 16 constitute a frame type noise reduction circuit a. 17 is a one-line delay circuit that delays the output luminance signal of the adder 16 by one horizontal scanning period, and 18 is a one-line delay circuit that delays the output luminance signal of the adder 16 by one horizontal scanning period.
19 is an attenuator that attenuates the output signal of the subtracter 18; 20 is an adder that adds the output signal of the attenuator 19 and the output luminance signal of the adder 16;
These 17 to 20 constitute a line type noise reduction circuit 6. 21 is a high-pass circuit that passes only the high-frequency component of the output luminance signal of the adder 20; 22 is a high-pass circuit 21;
23 is an attenuator that attenuates the output signal of the amplitude limiting circuit 22; 24 is a subtractor that subtracts the output signal of the attenuator 23 from the output luminance signal of the adder 20; These 21 to 24 constitute a coring type noise reduction circuit C. 25 is a frame correlation detector that detects the correlation between one frame of the input luminance signal based on the output of the subtracter 14, and 26 is a line correlation detector that detects the correlation of one horizontal scanning period of the input luminance signal based on the output of the subtracter 18. , 27 is a gain control circuit that adjusts the amount of attenuation of each attenuator 15.19.degree. 23 based on the output signals of the frame correlation detector 25 and line correlation detector 26.

FIG. 2 is a block diagram showing a color signal noise reduction circuit according to an embodiment of the present invention. In FIG. 2, 28 is a one-frame delay circuit that delays the color signal by one frame period, 29 is an adder that sums the output of the one-frame delay circuit 28 and the input color signal, and 30 is attenuated the output signal of adder 29. The attenuator 31 is a subtracter that subtracts the output signal of the attenuator 30 from the input color signal, and these 28 to 31 constitute a frame type noise reduction circuit d. 32 is a one-line delay circuit that delays the output color signal of the subtracter 31 by one horizontal scanning period; 33
34 is an attenuator that attenuates the output signal of the adder 33; 35 is an attenuator that adds the output signal of the attenuator 34 to the output color signal of the subtracter 31; These 32 subtracters are subtracted from the output color signal.
.about.35 constitute a line type noise reduction circuit e. 3
Reference numeral 6 denotes a band cutoff circuit that cuts off only the components near the color carrier in the output color signal of the subtracter 35, and 37 refers to a band cutoff circuit 3.
6 is an attenuator that attenuates the output signal; 38 is a subtracter 35;
These subtracters 36 to 38 constitute a band switching type noise reduction circuit f. 39 is a frame correlation detector that detects the correlation between one frame of the input color signal based on the output of the adder 29, and 40 is a line correlation detector that detects the correlation of the input color signal for one horizontal scanning period based on the output of the adder 33. , 41 is a gain control circuit that adjusts the amount of attenuation of each of the attenuators 30, 34 and 37 based on the output signals of the frame correlation detector 39 and line correlation detector 40.

The operations of the luminance signal noise reduction circuit and chrominance signal noise reduction circuit configured in this manner will be described below.

First, in the luminance signal noise reduction circuit shown in FIG. At the same time, the attenuation amount of the attenuator 15 of the line type noise reduction circuit A and the attenuation amount of the attenuator 23 of the coring type noise reduction circuit C are made zero.

On the other hand, when the correlation between frames is small as in a moving image, the gain control circuit 27 increases the amount of attenuation of the attenuator 15 of the frame type noise reduction circuit a to reduce the noise generated by the frame type noise reduction circuit a. At the same time as preventing the afterimage phenomenon, the resulting decrease in the noise reduction effect is compensated for by reducing the amount of attenuation of the attenuator 19 of the line type noise reduction circuit and increasing the noise reduction effect. The correlation in the scanning period is detected by the line correlation detector 26, and if the correlation in one horizontal scanning period is small, the gain control circuit 27 increases the amount of attenuation of one attenuator in the line type noise reduction circuit to reduce the line type noise. At the same time as preventing the rounding of the contour in the vertical direction that occurs due to the reduction circuit, the reduction in the noise reduction effect caused by this can be suppressed by reducing the amount of attenuation of the attenuator 23 of the coring type noise reduction circuit C to increase the noise reduction effect. compensate.

As described above, according to the present agA, the one-frame delay circuit 13 delays the input luminance signal by one frame period, the subtracter 14 subtracts the input luminance signal from the output of the one-frame delay circuit 13, and the output of the subtracter 14. an attenuator 15 that attenuates a signal; an adder 16 that sums the output signal of the attenuator 15 and the input luminance signal; a one-line delay circuit 17 that delays the output luminance signal of the adder 16 by one horizontal scanning period; a subtracter 18 that subtracts the output luminance signal of the adder 16 from the output of the line delay circuit 17; an attenuator 19 that attenuates the output signal of the subtracter 18; and an output signal of the attenuator 19 and the adder 1.
an adder 20 that takes the sum of the output luminance signals of 6;
A high-pass circuit 21 that passes only the high-frequency component of the output luminance signal of the high-pass circuit 21; an amplitude limiting circuit 22 that passes only a small amplitude of the output signal of the high-pass circuit 21; Attenuator 23 to attenuate and adder 2
a subtracter 24 that subtracts the output signal of the attenuator 23 from the output luminance signal of 0; a frame correlation detector 25 that detects the correlation between one frame of the luminance signal based on the output of the subtracter 14;
A line correlation detector 26 that detects correlation for one horizontal scanning period based on the output of the subtracter 18, and a frame correlation detector 25.
and the output signal of the line correlation detector 26, the attenuator 15.
By providing the gain control circuit 27 that adjusts the attenuation amount of each of 19.23, it is possible to obtain the same noise reduction effect for moving images as for still images without causing afterimage phenomenon or vertical contour dulling. be able to.

Also, in the color signal noise reduction circuit shown in FIG. 2, the correlation between one frame of the input color signal is detected by the frame correlation detector 39, as in the luminance signal noise reduction circuit, and when the correlation between one frame is large, The gain control circuit 41 reduces the amount of attenuation of the attenuator 30 of the frame type noise reduction circuit d to increase the noise reduction effect, and at the same time reduces the attenuation of the attenuator 34 of the line type noise reduction circuit e and the attenuator of the band switching type noise reduction circuit f. Set the attenuation amount of 37 to zero. On the other hand, when the correlation between frames is small as in a moving image, the gain control circuit 41 increases the amount of attenuation of the attenuator 30 of the frame type noise reduction circuit d to reduce the noise generated by the frame type noise reduction circuit d. At the same time as preventing the afterimage phenomenon, the resulting decrease in the noise reduction effect is compensated for by reducing the amount of attenuation of the attenuator 34 of the line type noise reduction circuit e and increasing the noise reduction effect. The line correlation detector 40 detects the correlation for one horizontal scanning period, and if the correlation for one horizontal scanning period is small, the gain control circuit 41 increases the attenuation amount of the attenuation 1i34 of the line type noise reduction circuit e, and To prevent the rounding of the contour in the vertical direction caused by the noise reduction circuit Re, and at the same time to reduce the resulting reduction in the noise reduction effect by reducing the amount of attenuation of the attenuator 37 of the band switching type noise reduction circuit f to increase the noise reduction effect. Make up for it.

As described above, according to this embodiment, the one-frame delay circuit 28 delays the input color signal by one frame period, and the adder 2 adds the output of the one-frame delay circuit 28 and the input color signal.
9, an attenuator 30 that attenuates the output signal of the adder 29, a subtracter 31 that subtracts the output signal of the attenuator 30 from the input color signal, and one line that delays the output color signal of the subtracter 31 by one horizontal scanning period. Delay circuit 32 and 1-line delay circuit 3
an adder 33 that takes the sum of the output of 2 and the output color signal of the subtracter 31; and an attenuator 34 that attenuates the output signal of the adder 33.
, a subtracter 35 that subtracts the output signal of the attenuator 34 from the output color signal of the subtracter 31, and a band cutoff circuit 3 that cuts off only the components near the color carrier of the output color signal of the subtracter 35.
6, an attenuator 37 that attenuates the output signal of the band cutoff circuit 36, a subtracter 38 that subtracts the output signal of the attenuator 37 from the output color signal of the subtracter 35, and an adder. A frame correlation detector 39 detects the correlation between frames, a line correlation detector 40 detects the correlation for one horizontal scanning period based on the output of the adder 33, and output signals of the frame correlation detector 39 and line correlation detector 40 By working together with the gain control circuit B41 that adjusts the amount of attenuation of each of the attenuators 30, 34, and 37, it can be used for moving images as well as still images without causing afterimage phenomenon or vertical contour dulling. It is possible to obtain the noise reduction effect of

Effects of the Invention As described above, according to the present invention, there is provided a one-frame delay circuit that delays an input luminance signal by one frame period, a first subtracter that subtracts the input luminance signal from the output of the one-frame delay circuit, and a frame-type noise reduction circuit comprising: a first attenuator that attenuates the output signal of the first subtracter; and a first adder that sums the output signal of the first attenuator and the input luminance signal; a 1-line delay circuit that delays the output luminance signal of the first adder by one horizontal scanning period; a second subtracter that subtracts the output luminance signal of the first adder from the output of the 1-line delay circuit; A line consisting of a second attenuator that attenuates the output signal of the second subtracter, and a second adder that sums the output signal of the second attenuator and the output luminance signal of the first adder. a high-pass circuit that passes only a high-frequency component of the output luminance signal of the second adder, and an amplitude limiting circuit that passes only a small amplitude of the output signal of the high-pass circuit. and a third attenuator that attenuates the output signal of the amplitude limiting circuit, and a third subtracter that subtracts the output signal of the third attenuator from the output luminance signal of the second adder. a frame correlation detector that detects a correlation between one frame of an input luminance signal, a line correlation detector that detects a correlation between one horizontal scanning period, and the frame correlation detector and the line correlation detector. Since the gain control circuit is provided with a gain control circuit that adjusts the amount of attenuation of each of the first attenuator, the second attenuator, and the third attenuator based on the output signal of the input luminance signal, the correlation between one frame of the input luminance signal and By optimally controlling the amount of attenuation of the three attenuators according to the degree of correlation in one horizontal scanning period, it is possible to reduce noise in the luminance signal without causing an afterimage phenomenon or vertical contour dulling. can.

It also includes a one-frame delay circuit that delays the input color signal by one frame period, a first adder that sums the output of the one-frame delay circuit and the input color signal, and attenuates the output signal of the first adder. a frame type noise reduction circuit comprising a first attenuator that subtracts the output signal of the first attenuator from the input color signal; and a frame type noise reduction circuit that subtracts the output signal of the first attenuator from the input color signal; a 1-line delay circuit that delays a scanning period; a second adder that sums the output of the 1-line delay circuit and the output color signal of the first subtracter; and attenuates the output signal of the second adder. a second attenuator to
a line type noise reduction circuit comprising a second subtracter that subtracts the output signal of the attenuator from the output color signal of the first subtracter; and a component near the color carrier of the output color signal of the second subtracter. and a band cutoff circuit that cuts off only the band 3I.
! A band switching type noise reduction circuit comprising a third attenuator that attenuates the output signal of the disconnection circuit, and a third subtracter that subtracts the output signal of the third attenuator from the output color signal of the second subtracter. , a frame correlation detector that detects the correlation between one frame of the input color signal, a line correlation detector that detects the correlation between one horizontal scanning period, and output signals of the frame correlation detector and the line correlation detector. Since it is provided with a gain control circuit that adjusts the amount of attenuation of each of the first attenuator, the second attenuator, and the third attenuator, the correlation between one frame of the input color signal and the one horizontal scanning period can be controlled. By appropriately controlling the attenuation amounts of the three attenuators in accordance with the degree of correlation, it is possible to reduce the noise in the color signal without causing an afterimage phenomenon or a dulling of the contour in the vertical direction.

Furthermore, by combining these, a noise reduction circuit suitable for color television receivers can be obtained.
Its practical effects are extremely large.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a luminance signal noise reduction circuit in an embodiment of the present invention, Fig. 2 is a block diagram of a chrominance signal noise reduction circuit in an embodiment of the invention, and Fig. 3 is a conventional luminance signal noise reduction circuit. Circuit Block Diagram FIG. 4 is a block diagram of a conventional color signal noise reduction circuit. 13, 28...1 frame delay circuit, 17.32...
・1 line delay circuit, 15.19.23.30.34.
37...Attenuator, 14, 18.24.31.35.3
8... Subtractor, 16.20.29°33... Adder, 25.39... Frame correlation detector, 2640.
... Line correlation detector, 27.41 ... Gain control circuit, 21 ... High-pass circuit, 22 ... Amplitude limiting circuit, 36 ... Band cutoff circuit, a, d ... Frame type Noise reduction circuit, be... line type noise reduction circuit, C...
- Coring type noise reduction circuit, f...Band switching type noise reduction circuit. @to

Claims (1)

[Claims] 1. A one-frame delay circuit that delays an input luminance signal by one frame period, a first subtracter that subtracts the input luminance signal from an output of the one-frame delay circuit, and a first subtracter that subtracts the input luminance signal from the output of the one-frame delay circuit. a frame-type noise reduction circuit comprising a first attenuator that attenuates an output signal; a first adder that sums the output signal of the first attenuator and the input luminance signal; a 1-line delay circuit that delays the output luminance signal by one horizontal scanning period; a second subtracter that subtracts the output luminance signal of the first adder from the output of the 1-line delay circuit; a second attenuator that attenuates the output signal;
a line type noise reduction circuit comprising a second adder that sums the output signal of the second attenuator and the output luminance signal of the first adder; a high-pass circuit that passes only a frequency component; an amplitude limiting circuit that passes only a small amplitude of the output signal of the high-pass circuit; and a third circuit that attenuates the output signal of the amplitude limiting circuit.
and a third subtracter that subtracts the output signal of the third attenuator from the output luminance signal of the second adder; a frame correlation detector for detecting correlation; a line correlation detector for detecting correlation for one horizontal scanning period; and a gain control circuit that adjusts the amount of attenuation of each of the attenuators and the third attenuator; A luminance signal noise reduction circuit configured to reduce noise by controlling the amount of attenuation of the luminance signal without causing an afterimage phenomenon or vertical contour dulling. 2. a one-frame delay circuit that delays the input luminance signal by one frame period; a first subtracter that subtracts the input luminance signal from the output of the one-frame delay circuit; and a first subtracter that attenuates the output signal of the first subtracter. a frame-type noise reduction circuit consisting of a first attenuator, a first adder that sums the output signal of the first attenuator and the input luminance signal; a one-line delay circuit that delays a scanning period; a second subtracter that subtracts the output luminance signal of the first adder from the output of the one-line delay circuit; and a second subtracter that attenuates the output signal of the second subtracter. 2 attenuators;
A line type noise reduction circuit comprising a second adder that sums the output signal of the second attenuator and the output luminance signal of the first adder, and detects the correlation between one frame of the input luminance signal. a frame correlation detector, a line correlation detector that detects the correlation of one horizontal scanning period, and an output signal of the frame correlation detector and the line correlation detector that controls the first attenuator and the second attenuator. It is equipped with a gain control circuit that adjusts the amount of attenuation of each, and controls the amount of attenuation of the two attenuators according to the degree of correlation between one frame of the input luminance signal and the degree of correlation between one horizontal scanning period, thereby eliminating the afterimage phenomenon. A luminance signal noise reduction circuit configured to reduce noise without causing noise. 3. a one-frame delay circuit that delays the input luminance signal by one frame period; a first subtracter that subtracts the input luminance signal from the output of the one-frame delay circuit; and a first subtracter that attenuates the output signal of the first subtracter. a frame-type noise reduction circuit comprising a first attenuator, a first adder that takes the sum of the output signal of the first attenuator and the input luminance signal; a high-pass circuit that allows only a component to pass; an amplitude limiting circuit that allows only a small amplitude of the output signal of the high-pass circuit to pass; a second attenuator that attenuates the output signal of the amplitude limiting circuit; a coring type noise reduction circuit comprising a second subtracter that subtracts the output signal of the second attenuator from the output luminance signal of the first adder;
a frame correlation detector that detects a correlation between one frame of an input luminance signal; and a gain control that adjusts the attenuation amount of each of the first attenuator and the second attenuator based on the output signal of the frame correlation detector. By controlling the amount of attenuation of the two attenuators according to the degree of correlation between one frame of the input luminance signal, the noise is reduced without causing an afterimage phenomenon or vertical contour dulling. A luminance signal noise reduction circuit configured as follows. 4. A one-line delay circuit that delays the input luminance signal by one horizontal scanning period, a first subtracter that subtracts the input luminance signal from the output of the one-line delay circuit, and attenuates the output signal of the first subtracter. A line type noise reduction circuit comprising a first attenuator, a first adder that takes the sum of the output signal of the first attenuator and the input luminance signal, and a line noise reduction circuit that increases the output luminance signal of the first adder. a high-pass circuit that passes only the frequency component; an amplitude limiting circuit that passes only a small amplitude of the output signal of the high-pass circuit; and a second attenuator that attenuates the output signal of the amplitude limiting circuit; A coring type noise reduction circuit including a second subtracter that subtracts the output signal of the second attenuator from the output luminance signal of the first adder and detects the correlation between one horizontal scanning period of the input luminance signal. a line correlation detector; and a gain control circuit that adjusts the attenuation amount of each of the first attenuator and the second attenuator based on the output signal of the line correlation detector; A luminance signal noise reduction circuit configured to reduce noise without causing rounding of vertical contours by controlling attenuation amounts of the two attenuators according to the degree of correlation between periods. 5. A one-frame delay circuit that delays the input color signal by one frame period, a first adder that sums the output of the one-frame delay circuit and the input color signal, and attenuates the output signal of the first adder. a frame type noise reduction circuit comprising a first attenuator that subtracts the output signal of the first attenuator from the input color signal; and a frame type noise reduction circuit that subtracts the output signal of the first attenuator from the input color signal; a 1-line delay circuit that delays a scanning period; a second adder that sums the output of the 1-line delay circuit and the output color signal of the first subtracter; and attenuates the output signal of the second adder. a second subtracter that subtracts the output signal of the second attenuator from the output color signal of the first subtracter; and the second subtracter. a band cutoff circuit that blocks only components near the color carrier of the output color signal of the band cutoff circuit; a third attenuator that attenuates the output signal of the band cutoff circuit; and a third attenuator that attenuates the output signal of the band cutoff circuit; A band switching noise reduction circuit consisting of a third subtracter that subtracts the output signal of the third attenuator, a frame correlation detector that detects the correlation between one frame of the input color signal, and a frame correlation detector that detects the correlation between one horizontal scanning period. and a line correlation detector for adjusting the attenuation amount of each of the first attenuator, the second attenuator, and the third attenuator using the output signals of the frame correlation detector and the line correlation detector. Equipped with a gain control circuit, the amount of attenuation of the three attenuators is controlled according to the degree of correlation between one frame of input color signals and the degree of correlation between one horizontal scanning period, thereby preventing afterimage phenomena and rounding of vertical contours. A color signal noise reduction circuit configured to reduce noise without causing any noise. 6. A one-frame delay circuit that delays the input color signal by one frame period, a first adder that sums the output of the one-frame delay circuit and the input color signal, and attenuates the output signal of the first adder. a frame type noise reduction circuit comprising a first attenuator that subtracts the output signal of the first attenuator from the input color signal; and a frame type noise reduction circuit that subtracts the output signal of the first attenuator from the input color signal; a 1-line delay circuit that delays a scanning period; a second adder that sums the output of the line delay circuit and the output color signal of the first subtracter; and attenuates the output signal of the second adder. a line type noise reduction circuit comprising a second attenuator and a second subtracter that subtracts the output signal of the second attenuator from the output color signal of the first subtracter;
a frame correlation detector that detects the correlation between one frame of input color signals; a line correlation detector that detects the correlation between one horizontal scanning period; a gain control circuit that adjusts the amount of attenuation of each of the first attenuator and the second attenuator; A color signal noise reduction circuit configured to reduce noise without causing an afterimage phenomenon by controlling the amount of attenuation of an attenuator. 7. A one-frame delay circuit that delays the input color signal by one frame period, a first adder that sums the output of the one-frame delay circuit and the input color signal, and attenuates the output signal of the first adder. a frame-type noise reduction circuit comprising a first attenuator that subtracts the output signal of the first attenuator from the input color signal; a band cutoff circuit that blocks only components near the carrier wave; a second attenuator that attenuates the output signal of the band cutoff circuit; and an output signal of the second attenuator from the output color signal of the first subtracter. a band-switching noise reduction circuit comprising a second subtracter; a frame correlation detector for detecting correlation between one frame of the input color signal; and an output signal of the frame correlation detector to detect the first attenuator and a gain control circuit that adjusts the amount of attenuation of each of the second attenuators, and controls the amount of attenuation of the two attenuators according to the degree of correlation between one frame of the input color signal, thereby eliminating afterimages. A color signal noise reduction circuit configured to reduce noise without causing distortion or vertical contour distortion. 8. A one-line delay circuit that delays an input color signal by one horizontal scanning period, a first adder that sums the output of the one-line delay circuit and the input color signal, and an output signal of the first adder. A line-type noise reduction circuit comprising a first attenuator to attenuate, a first subtracter to subtract the output signal of the first attenuator from the input color signal, and an output color signal of the first subtracter. a band cutoff circuit that cuts off only components near the color carrier; a second attenuator that attenuates the output signal of the band cutoff circuit;
a band switching type noise reduction circuit consisting of a second subtracter that subtracts the output signal of the attenuator; a line correlation detector that detects the correlation of one horizontal scanning period of the input chrominance signal; and an output signal of the line correlation detector. a gain control circuit that adjusts the amount of attenuation of each of the first attenuator and the second attenuator, and adjusts the amount of attenuation of the two attenuators according to the degree of correlation in one horizontal scanning period of the input color signal. A color signal noise reduction circuit configured to reduce noise without causing vertical contour distortion by controlling the amount of attenuation. 9. A color television receiver comprising the luminance signal noise reduction circuit according to any one of claims 1 to 4 and the color signal noise reduction circuit according to any one of claims 5 to 8. Machine noise reduction circuit.