JP2974384B2 - Luminance signal and chrominance signal noise reduction circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a luminance signal and a chrominance signal noise reduction circuit of 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, the introduction of digital technology to television receivers has been remarkable, and in particular, a luminance signal and chrominance signal noise reduction circuit using a digital memory is often used.

Hereinafter, an example of the above-described conventional luminance signal noise reduction circuit and chrominance signal noise reduction circuit will be described 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 for delaying the input luminance signal for one frame period, 2 is a subtractor for subtracting the input luminance signal from the output of the 1-frame delay circuit 1, and 3 is an attenuator for the output signal of the subtractor 2. An attenuator, 4 is an adder for taking the sum of the output signal of the attenuator 3 and the input luminance signal, 5 is a frame correlation detector for detecting the correlation between one frame of the input luminance signal by the output of the subtractor 4, and 6 is a frame correlation detector. This is a gain control circuit that adjusts the amount of attenuation of the attenuator 3 based on the output of the correlation detector 5.

The operation of the thus configured luminance signal noise reduction circuit will be described 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, the subtracter 2 takes the difference between the input luminance signal and the input luminance signal delayed by one frame, and extracts a non-correlation part between one frame of the input luminance signal, that is, a noise component. Since the polarity of the noise component is inverted with respect to the input luminance signal, the adder 4 adds the polarity to the input luminance signal to reduce the noise component. However, in this case, in the case of a luminance signal having a correlation between one frame such as a still image, the output of the subtracter 2 includes only a noise component. However, in the case of a moving image, there is no correlation between the one frame. An uncorrelated component of the luminance signal itself appears in the output at the same time as the noise component, and when this is subtracted from the input luminance signal, an afterimage phenomenon appears as if the picture was moved on the screen and then trailed. Therefore, the correlation between one frame of the input luminance signal is detected by the frame correlation detector 5 from the output of the subtracter 2, and the attenuation of the attenuator 3 is adjusted by the gain control circuit 6. That is, when the output of the subtracter 2 is below a certain amplitude, it is regarded that there is a correlation between one frame, and the amount of attenuation of the attenuator 3 is reduced to increase the noise reduction effect. If the amplitude is equal to or more than 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 in accordance with the magnitude of the amplitude to reduce the noise reduction effect. The afterimage phenomenon is kept small.

FIG. 4 is a block diagram of a conventional color signal noise reduction circuit. In FIG. 4, reference numeral 7 denotes a one-frame delay circuit for delaying an input color signal by one frame period, 8 denotes an adder for summing the output of the one-frame delay circuit 7 and the input color signal, and 9 denotes an output signal of the adder 8. An attenuator for attenuating the signal, a subtracter for subtracting the output signal of the attenuator 9 from the input color signal, a frame correlation detector 11 for detecting a correlation between one frame of the input color signal by the output of the adder 8, and a frame correlation detector 12. This is a gain control circuit that adjusts the amount of attenuation of the attenuator by the output of the correlation detector 11.

In the above configuration, the operation is as follows. First, the input color signal passes through the subtracter 10 and is output by the delay circuit 7 to 1
Delayed by the frame period. Next, the adder 8 calculates the sum of the input color signal and the input color signal delayed by one frame. Here, since the polarity of the chrominance carrier of the input chrominance signal is inverted for each frame, an uncorrelated portion between one frame of the input chrominance signal, that is, a noise component is extracted by taking the sum of the two with an adder. Can be. Since the noise component has the same polarity as the input color signal, the noise component is reduced by subtracting the noise component from the input color signal by the subtractor 10. However, as in the case of the luminance signal noise reduction circuit, the output of the adder 8 is only a noise component in the case of a color signal having a correlation between one frame like a still image. Since there is no correlation between the input color signal and the noise component, an uncorrelated component of the color signal itself appears at the output of the adder 8. An afterimage phenomenon appears as if it were pulled. Therefore, the correlation between one frame of the input color signal is detected by the frame correlation detector 11 from the output of the adder 8, and the attenuation of the attenuator 9 is adjusted by the gain control circuit 12. That is, when the output of the adder 8 is below a certain amplitude, it is considered that there is a correlation between one frame and the attenuator 9
Is reduced to increase the noise reduction effect. If the output of the adder 8 is equal to or greater than a certain amplitude, it is determined that there is no correlation between one frame, and the attenuator 9 is determined according to the magnitude of the amplitude. By reducing the noise reduction effect by increasing the amount of attenuation of the image, the afterimage phenomenon that occurs in a moving image is suppressed to a small extent.

SUMMARY OF THE INVENTION However, in the above-described configuration, the noise reduction effect is reduced for a moving image, so that noise is suddenly noticeable when moving from a still image to a moving image, or the noise is reduced for a moving image. Since the effect cannot be reduced to zero, there is a problem that an afterimage phenomenon always 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 provide a noise reduction effect equivalent to that of a still image even for a moving image, and at the same time provide a stable screen with little afterimage. The purpose is to do so.

Means for Solving the Problems In order to solve the above problems, first, a luminance signal noise reduction circuit of the present invention comprises a one-frame delay circuit for delaying an input luminance signal for one frame period, and an output of the one-frame delay circuit. A first subtractor for subtracting an input luminance signal, a first attenuator for attenuating an output signal of the first subtractor,
A frame-type noise reduction circuit comprising a first adder for summing an output signal of the first attenuator and an input luminance signal, and one line for delaying the output luminance signal of the first adder by one horizontal scanning period A delay circuit, a second subtracter for subtracting an output luminance signal of the first adder from an output of the one-line delay circuit, and a second attenuator for attenuating an output signal of the second subtractor.
An attenuator, a line-type noise reduction circuit comprising a second adder for summing an output signal of the second attenuator and an output luminance signal of the first adder, A high-pass circuit that passes only the high-frequency component of the output luminance signal, an amplitude limiting circuit that allows only a small amplitude of the output signal of the high-pass circuit to pass, and an attenuator that attenuates the output signal of the amplitude limiting circuit. 3, a coring-type noise reduction circuit comprising a third subtractor for subtracting the output signal of the third attenuator from the output luminance signal of the second adder, and between one frame of the input luminance signal. , A line correlation detector for detecting a correlation in one horizontal scanning period, the first attenuator and the second signal based on output signals of the frame correlation detector and the line correlation detector. Attenuator and said third damper Of those with the respective attenuation comprising a gain control circuit for adjusting.

Further, the color signal noise reduction circuit of the present invention is capable of reducing the input color signal to one.
A one-frame delay circuit for delaying a frame period;
A first adder for taking the sum of the output of the frame delay circuit and the input color signal, a first attenuator for attenuating the output signal of the first adder, and an output signal of the first attenuator A frame-type noise reduction circuit comprising a first subtractor for subtracting from a color signal; a one-line delay circuit for delaying an output color signal of the first subtractor for one horizontal scanning period; an output of the one-line delay circuit; A second adder that takes the sum of the output color signals of the first subtractor, a second attenuator that attenuates the output signal of the second adder, and an output signal of the second attenuator. A line-type noise reduction circuit comprising a second subtractor for subtracting from an output color signal of the first subtractor; a band-stop circuit for cutting off only a component near a color carrier in the output color signal of the second subtractor; A third attenuation for attenuating an output signal of the band rejection circuit. A band-switching noise reduction circuit comprising a third subtractor for subtracting an output signal of the third attenuator from an output color signal of the second subtractor, and detecting a correlation between one frame of the input color signal. A frame correlation detector,
A line correlation detector for detecting a correlation during one horizontal scanning period;
A gain control circuit that adjusts respective attenuation amounts of the first attenuator, the second attenuator, and the third attenuator based on output signals of the frame correlation detector and the line correlation detector. It is.

The present invention detects the correlation between one frame of the luminance signal and the color signal and the correlation during one horizontal scanning period by the above-described configuration, and when the correlation between one frame is large as in a still image, the frame type noise is detected. The attenuation 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 is replaced with a third attenuator of the coring type or band switching type noise reduction circuit. To zero. On the other hand, when the correlation between one frame is small like a moving image, the amount of attenuation of the first attenuator of the frame type noise reduction circuit is increased to prevent the afterimage phenomenon generated by the frame type noise reduction circuit. At the same time, the reduction of the noise reduction effect is compensated for by reducing the attenuation of the second attenuator of the line type noise reduction circuit to increase the noise reduction effect. However, at this time, when the correlation of one horizontal scanning period of the signal is small, the amount of attenuation of the second attenuator of the line type noise reduction circuit is increased to reduce the roundness of the vertical contour generated by the line type noise reduction circuit. At the same time, the reduction of the noise reduction effect is compensated for by reducing the attenuation of the attenuator of the coring type or band switching type noise reduction circuit to increase the noise reduction effect. In this manner, a noise reduction effect equivalent to that of a still image can be obtained even for a moving image without causing an afterimage phenomenon or a rounding of a vertical contour.

Further, in the case of a configuration including only the frame type noise reduction circuit and the line type noise reduction circuit, the correlation between one frame of the luminance signal and the chrominance signal and the correlation during one horizontal scanning period are detected, and the correlation between one frame as in a still image is detected. Is large, the attenuation 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 of the second attenuator of the line type noise reduction circuit is set to zero. On the other hand, when the correlation between one frame is small like a moving image, the amount of attenuation of the first attenuator of the frame type noise reduction circuit is increased to prevent the afterimage phenomenon generated by the frame type noise reduction circuit. At the same time, the reduction of the noise reduction effect is compensated for by reducing the attenuation of the second attenuator of the line type noise reduction circuit to increase the noise reduction effect. In this manner, a noise reduction effect equivalent to that of a still image can be obtained for a moving image without causing an afterimage phenomenon.

Further, in the case of a configuration including only the frame type noise reduction circuit and the coring type or band switching type noise reduction circuit, the correlation between one frame of the luminance signal and the chrominance signal and the correlation during one horizontal scanning period are detected, and the still image is detected. As described above, when the correlation between one frame is large, the amount of attenuation 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 second amount of the coring type or band switching type noise reduction circuit is reduced. The amount of attenuation of the attenuator is zero. On the other hand, when the correlation between one frame is small like a moving image, the amount of attenuation of the first attenuator of the frame type noise reduction circuit is increased to prevent the afterimage phenomenon generated by the frame type noise reduction circuit. At the same time, the reduction of 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 manner, a noise reduction effect equivalent to that of a still image can be obtained even for a moving image without causing an afterimage phenomenon or a rounding of a vertical contour.

Further, in the case of a configuration including only the line type noise reduction circuit and the coring type or band switching type noise reduction circuit, the correlation between the luminance signal and the chrominance signal in one horizontal scanning period is detected. Reduce the attenuation of the first attenuator of the line type noise reduction circuit to increase the noise reduction effect, and at the same time, reduce the attenuation of the second attenuator of the coring type or band switching type noise reduction circuit to zero. . On the other hand, when the correlation in one horizontal scanning period is small, the amount of attenuation of the first attenuator of the line noise reduction circuit is increased to prevent the rounding of the vertical contour generated by the line noise reduction circuit. At the same time, the reduction of the noise reduction effect is compensated for by reducing the attenuation of the second attenuator of the coring type or band switching type noise reduction circuit to increase the noise reduction effect. In this manner, a noise reduction effect equivalent to that of the other portions can be obtained for the vertical contour portion without causing the vertical contour to be rounded.

An embodiment 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 one embodiment of the present invention. In FIG. 1, 13 is a one-frame delay circuit for delaying a luminance signal for one frame period, 14 is a subtracter for subtracting an input luminance signal from the output of the one-frame delay circuit 13, and 15 is an attenuator for attenuating the output signal of the subtractor 14. And 16, an adder for taking the sum of the output signal of the attenuator 15 and the input luminance signal, and these 13 to 16 constitute a frame type noise reduction circuit a. 17 is a one-line delay circuit for delaying the output luminance signal of the adder 16 for one horizontal scanning period, 18 is a subtractor for subtracting the output luminance signal of the adder 16 from the output of the one-line delay circuit 17, and 19 is the output of the subtracter 18. An attenuator that attenuates the signal,
An adder 20 calculates the sum of the output signal of the attenuator 19 and the output luminance signal of the adder 16, and these 17 to 20 constitute the line 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 an amplitude limiting circuit that allows only a small amplitude of the output signal of the high-pass circuit 21, and 23 is an amplitude limiting circuit. An attenuator 22 attenuates the output signal, and 24 is a subtracter for subtracting the output signal of the attenuator 23 from the output luminance signal of the adder 20, and these 21 to 24 constitute a coring noise reduction circuit c. Reference numeral 25 denotes a frame correlation detector for detecting the correlation between one frame of the input luminance signal based on the output of the subtractor 14, and reference numeral 26 denotes a line correlation detector for detecting the correlation of the input luminance signal during one horizontal scanning period based on the output of the subtracter 18. Reference numerals 27 denote gain control circuits that adjust the respective attenuation amounts of the attenuators 15, 19, and 23 based on the output signals of the frame correlation detector 25 and the line correlation detector.

FIG. 2 is a block diagram showing a color signal noise reduction circuit according to one embodiment of the present invention. In FIG. 2, reference numeral 28 denotes a one-frame delay circuit for delaying a color signal by one frame period;
An adder that takes the sum of the output of the frame delay circuit 28 and the input color signal, 30 is an attenuator that attenuates the output signal of the adder 29, 31 is a subtractor that subtracts the output signal of the attenuator 30 from the input color signal,
These 28 to 31 constitute a frame type noise reduction circuit d. 32 is a one-line delay circuit for delaying the output color signal of the subtractor 31 for one horizontal scanning period, 33 is an adder for taking the sum of the output of the one-line delay circuit 32 and the output color signal of the subtractor 31, and 34 is an adder 33 Attenuator that attenuates the output signal of
Is subtracted from the output color signal of the subtractor 31. A line-type noise reduction circuit e is constituted by these 32-35. 36 is a band cutoff circuit that cuts off only the components near the color carrier in the output color signal of the subtracter 35, 37 is an attenuator that attenuates the output signal of the band cutoff circuit 36, and 38 is an attenuator from the output color signal of the subtractor 35 Subtractor that subtracts the output signal of the
These 36 to 38 constitute a band switching type noise reduction circuit f. 39 is a frame correlation detector for detecting the correlation between one frame of the input color signal by the output of the adder 29, and 40 is a line correlation detector for detecting the correlation of the input color signal during one horizontal scanning period by the output of the adder 33. , 41 is a frame correlation detector 39
And attenuators 30, 34, and 37 according to the output signal of line correlation detector 40.
Is a gain control circuit for adjusting the respective attenuation amounts.

The operation of the thus configured luminance signal noise reduction circuit and chrominance signal noise reduction circuit will be described below.

First, in the luminance signal noise reduction circuit of FIG. 1, the correlation between one frame of the input luminance signal is detected by a frame correlation detector 25. If the correlation between the frames is large, the gain control circuit 27 controls the frame type noise reduction circuit. a attenuator 15
Is reduced to increase the noise reduction effect, and at the same time, the attenuation of the attenuator 19 of the line type noise reduction circuit b and the attenuator 23 of the coring type noise reduction circuit c is made zero.

On the other hand, when the correlation between one frame is small as in the case of a moving image, the noise is generated by the frame type noise reduction circuit a by increasing the attenuation of the attenuator 15 of the frame type noise reduction circuit a by the gain control circuit 27. A line type noise reduction circuit b that prevents the afterimage phenomenon and reduces the noise reduction effect due to it.
This is compensated for by making the amount of attenuation of the attenuator 19 smaller to increase the noise reduction effect. However, at this time, the correlation of the luminance signal in one horizontal scanning period is detected by the line correlation detector 26, and when the correlation in one horizontal scanning period is small, the gain control circuit 27 controls the attenuator 19 of the line noise reduction circuit b. The amount of attenuation is increased to prevent the rounding of the vertical contour generated by the line type noise reduction circuit b and to reduce the noise reduction effect by reducing the amount of attenuation of the attenuator 23 of the coring type noise reduction circuit c. To increase the noise reduction effect.

As described above, according to the present embodiment, the one-frame delay circuit 13 that delays the input luminance signal by one frame period, and the subtractor that subtracts the input luminance signal from the output of the one-frame delay circuit 13
14, an attenuator 15 for attenuating the output signal of the subtractor 14,
An adder 16 for summing the output signal of the attenuator 15 and the input luminance signal
A one-line delay circuit 17 for delaying the output luminance signal of the adder 16 by one horizontal scanning period, a subtracter 18 for subtracting the output luminance signal of the adder 16 from the output of the one-line delay circuit 17, Attenuator 19 for attenuating the output signal, and attenuator 19
Adder that takes the sum of the output signal of the adder 16 and the output luminance signal of the adder 16
20; a high-pass circuit 21 for passing only the high-frequency component of the output luminance signal of the adder 20; an amplitude limiting circuit 22 for passing only a small amplitude of the output signal of the high-pass circuit 21; An attenuator 23 for attenuating the output signal of the circuit 22, a subtracter 24 for subtracting the output signal of the attenuator 23 from the output luminance signal of the adder 20, and a correlation between one frame of the luminance signal is detected by an output of the subtracter 14. A frame correlation detector 25, a line correlation detector 26 for detecting a correlation in one horizontal scanning period based on an output of the subtractor 18, and attenuators 15, 19 based on output signals of the frame correlation detector 25 and the line correlation detector 26. The gain control circuit 27 that adjusts the amount of attenuation of each of the, 23 can obtain a noise reduction effect equivalent to that of a still image even for a moving image without causing an afterimage phenomenon or blurring of a vertical contour. Can be.

Also in the chrominance signal noise reduction circuit of FIG. 2, similarly to the luminance signal noise reduction circuit, the correlation between one frame of the input chrominance signal is detected by the frame correlation detector 39, and when the correlation between one frame is large, The gain control circuit 40 reduces the attenuation of the attenuator 30 of the frame type noise reduction circuit d to increase the noise reduction effect, and at the same time, attenuates the attenuator 34 of the line type noise reduction circuit e and the band switching type noise reduction circuit f. Container 37
To zero. On the other hand, when the correlation between one frame is small as in a moving image, the gain control circuit 41 increases the attenuation of the attenuator 30 of the frame-type noise reduction circuit d, and the frame-type noise reduction circuit d generates the signal. At the same time, the afterimage phenomenon is prevented, and the reduction in the noise reduction effect is compensated for by reducing the attenuation of the attenuator 34 of the line-type noise reduction circuit e to increase the noise reduction effect. However, at this time,
The correlation of the luminance signal during one horizontal scanning period is determined by a line correlation detector 40.
If the correlation in one horizontal scanning period is small,
The gain control circuit 41 increases the attenuation of the attenuator 34 of the line type noise reduction circuit e to prevent the rounding of the vertical contour generated by the line type noise reduction circuit e and to reduce the noise reduction effect. This is compensated for by reducing the amount of attenuation of the attenuator 37 of the switching type noise reduction circuit f to increase the noise reduction effect.

As described above, according to the present embodiment, the one-frame delay circuit 28 for delaying the input color signal for one frame period, and the adder 29 for taking the sum of the output of the one-frame delay circuit 28 and the input color signal
An attenuator 30 for attenuating the output signal of the adder 29; a subtracter 31 for subtracting the output signal of the attenuator 30 from the input color signal; and a one-line delay for delaying the output color signal of the subtracter 31 for one horizontal scanning period. A circuit 32, an adder 33 for summing the output of the one-line delay circuit 32 and the output color signal of the subtractor 31, an attenuator 34 for attenuating the output signal of the adder 33, and subtracting the output signal of the attenuator 34 Subtracter 35 for subtracting from the output color signal of the adder 31, a band rejection circuit 36 for rejecting only components near the color carrier in the output color signal of the subtracter 35, and an attenuator 37 for attenuating the output signal of the band rejection circuit 36. A subtracter 38 for subtracting the output signal of the attenuator 37 from the output color signal of the subtractor 35; a frame correlation detector 39 for detecting the correlation between one frame of the color signal by the output of the adder 29; A line correlation detector 40 for detecting a correlation in one horizontal scanning period by the output of , The attenuator 3 by the output signal of the frame correlation detector 39 and the line correlation detector 40
Gain control circuit 4 for adjusting the attenuation of each of 0, 34, and 37
By providing 1, it is possible to obtain a noise reduction effect equivalent to that of a still image even for a moving image without causing an afterimage phenomenon or blurring of a vertical contour.

As described above, according to the present invention, according to the present invention, a one-frame delay circuit for delaying an input luminance signal by one frame period, a first subtractor for subtracting an input luminance signal from an output of the one-frame delay circuit, A frame-type noise reduction circuit including a first attenuator for attenuating an output signal of the first subtractor, a first adder for summing an output signal of the first attenuator and an input luminance signal, A one-line delay circuit for delaying the output luminance signal of the first adder for one horizontal scanning period, a second subtractor for subtracting the output luminance signal of the first adder from the output of the one-line delay circuit, A second attenuator for attenuating an output signal of the second subtractor; and a second attenuator for summing an output signal of the second attenuator and an output luminance signal of the first adder.
A line-type noise reduction circuit comprising an adder, a high-pass circuit for passing only the high-frequency component of the output luminance signal of the second adder, and only a small amplitude of the output signal of the high-pass circuit. An amplitude limiting circuit that allows the signal to pass therethrough; a third attenuator that attenuates an output signal of the amplitude limiting circuit;
And a correlating noise reduction circuit comprising a third subtractor for subtracting the output signal of the third attenuator from the output luminance signal of the adder, and a frame correlation detector for detecting a correlation between one frame of the input luminance signal. A line correlation detector for detecting a correlation in one horizontal scanning period, the first attenuator, the second attenuator, and the third attenuator based on output signals of the frame correlation detector and the line correlation detector. Since a gain control circuit is provided for adjusting the attenuation of each of the attenuators, the attenuation of the three attenuators is optimized in accordance with the degree of correlation between one frame of the input luminance signal and the degree of correlation during one horizontal scanning period. By performing the control, it is possible to reduce the noise of the luminance signal without causing the afterimage phenomenon or the rounding of the contour in the vertical direction.

A one-frame delay circuit for delaying the input color signal by one frame period; a first adder for summing an output of the one-frame delay circuit and the input color signal; and attenuating an output signal of the first adder. A first attenuator, a frame-type noise reduction circuit including a first subtractor for subtracting an output signal of the first attenuator from an input color signal, A one-line delay circuit for delaying a scanning period, a second adder for summing an output of the one-line delay circuit and an output color signal of the first subtractor, and attenuating an output signal of the second adder A second attenuator for subtracting an output signal of the second attenuator from an output color signal of the first subtracter, and a line-type noise reduction circuit including a second attenuator; and a second subtractor. Of the output color signal of the And a third attenuator for attenuating the output signal of the band rejection circuit, and a third subtractor for subtracting the output signal of the third attenuator from the output color signal of the second subtractor. A band-switching noise reduction circuit comprising: a frame correlation detector for detecting a correlation between one frame of the input color signal; a line correlation detector for detecting a correlation during one horizontal scanning period; Since there is provided a gain control circuit for adjusting the respective attenuation amounts of the first attenuator, the second attenuator, and the third attenuator according to the output signal of the line correlation detector, one frame of the input color signal is provided. Optimum control of the attenuation of the three attenuators according to the degree of correlation between one horizontal scanning period and the other, thereby reducing color signal noise without causing afterimages or blurring of vertical contours. Can do That.

Further, by combining these, a noise reduction circuit suitable for a color television receiver can be obtained, and its practical effect is extremely large.

[Brief description of the drawings]

FIG. 1 is a block diagram of a luminance signal noise reduction circuit according to one embodiment of the present invention, FIG. 2 is a block diagram of a color signal noise reduction circuit according to one embodiment of the present invention, and FIG. 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,
38 Subtractor, 16, 20, 29, 33 Adder, 25, 39 Frame correlation detector, 26, 40 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, b, e ... Line type noise reduction circuit, c: Coring type noise reduction circuit, f: Band switching type noise reduction circuit.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H04N 9/64 H04N 9/78

Claims (9)

(57) [Claims] 1. A one-frame delay circuit for delaying an input luminance signal by one frame period, a first subtractor for subtracting an input luminance signal from an output of the one-frame delay circuit, and an output signal of the first subtractor A first attenuator for attenuating, and a first attenuator for summing an output signal and an input luminance signal of the first attenuator
A frame-type noise reduction circuit comprising:
1 that delays the output luminance signal of the adder 1 by one horizontal scanning period.
A line delay circuit, a second subtractor for subtracting the output luminance signal of the first adder from the output of the one-line delay circuit, and a second attenuator for attenuating the output signal of the second subtractor A line-type noise reduction circuit comprising a second adder for summing an output signal of the second attenuator and an output luminance signal of the first adder; A high-pass circuit for passing only high-frequency components, an amplitude limiting circuit for passing only a small amplitude of the output signal of the high-pass circuit, and a third attenuator for attenuating an output signal of the amplitude limiting circuit. Detecting a correlation between one frame of an input luminance signal and a coring type noise reduction circuit including a third subtractor for subtracting an output signal of the third attenuator from an output luminance signal of the second adder. Frame correlation detector and one horizontal scan period A line correlation detector for detecting a relationship between the first attenuator, the second attenuator, and the third attenuator based on output signals of the frame correlation detector and the line correlation detector. And a gain control circuit for adjusting the amount of correlation between one frame of the input luminance signal and the degree of correlation during one horizontal scanning period. A luminance signal noise reduction circuit configured to reduce noise without causing rounding of contours. 2. A one-frame delay circuit for delaying an input luminance signal by one frame period, a first subtractor for subtracting an input luminance signal from an output of the one-frame delay circuit, and an output signal of the first subtractor. A first attenuator for attenuating, and a first attenuator for summing an output signal and an input luminance signal of the first attenuator
A frame-type noise reduction circuit comprising:
1 that delays the output luminance signal of the adder 1 by one horizontal scanning period.
A line delay circuit, a second subtractor for subtracting the output luminance signal of the first adder from the output of the one-line delay circuit, and a second attenuator for attenuating the output signal of the second subtractor A line-type noise reduction circuit comprising a second adder for summing an output signal of the second attenuator and an output luminance signal of the first adder, and detecting a correlation between one frame of the input luminance signal. Frame correlation detector, a line correlation detector for detecting a correlation in one horizontal scanning period, the first attenuator and the second attenuator based on output signals of the frame correlation detector and the line correlation detector. And a gain control circuit that adjusts the amount of attenuation of each of the two attenuators according to the degree of correlation between one frame of the input luminance signal and the degree of correlation during one horizontal scanning period. Miscellaneous without causing phenomena Luminance signal noise reduction circuit which is configured to reduce. 3. A one-frame delay circuit for delaying an input luminance signal for one frame period, a first subtractor for subtracting the input luminance signal from an output of the one-frame delay circuit, and an output signal of the first subtractor. A first attenuator for attenuating, and a first attenuator for summing an output signal and an input luminance signal of the first attenuator
A frame-type noise reduction circuit comprising:
A high-pass circuit that passes only the high-frequency component of the output luminance signal of the adder, an amplitude limiting circuit that allows only a small amplitude of the output signal of the high-pass circuit, and an output signal of the amplitude limiting circuit. A second attenuator for attenuating the first attenuator;
And a correlating noise reduction circuit comprising a second subtractor for subtracting the output signal of the second attenuator from the output luminance signal of the adder, and a frame correlation detector for detecting a correlation between one frame of the input luminance signal. And a gain control circuit that adjusts the amount of attenuation of each of the first attenuator and the second attenuator based on an output signal of the frame correlation detector, and a degree of correlation between one frame of the input luminance signal. A luminance signal noise reduction circuit configured to control the amount of attenuation of the two attenuators in accordance with the above to reduce noise without causing an afterimage phenomenon or a rounding of a vertical contour. 4. A one-line delay circuit for delaying an input luminance signal by one horizontal scanning period, a first subtractor for subtracting the input luminance signal from an output of the one-line delay circuit, and an output signal of the first subtractor A first attenuator for attenuating the first
A line-type noise reduction circuit comprising a first adder for summing an output signal of the attenuator and an input luminance signal; and a high-pass circuit for passing only a high-frequency component of the output luminance signal of the first adder. An amplitude limiting circuit for passing only a small amplitude of the output signal of the high-pass circuit, a second attenuator for attenuating an output signal of the amplitude limiting circuit, and an output luminance signal of the first adder , A coring type noise reduction circuit comprising a second subtractor for subtracting the output signal of the second attenuator from the input signal, a line correlation detector for detecting the correlation of the input luminance signal during one horizontal scanning period, and the line correlation detection A gain control circuit that adjusts the amount of attenuation of each of the first attenuator and the second attenuator in accordance with the output signal of the input attenuator. Controls the attenuation of two attenuators Luminance signal noise reduction circuit which is configured to reduce noise without causing distortion of the vertical contour by Rukoto. 5. An apparatus for delaying an input color signal by one frame period.
A frame delay circuit, a first adder for summing an output of the one-frame delay circuit and an input color signal, a first attenuator for attenuating an output signal of the first adder, A frame-type noise reduction circuit comprising a first subtractor for subtracting the output signal of the attenuator from the input color signal; a one-line delay circuit for delaying the output color signal of the first subtractor for one horizontal scanning period; A second adder that takes a sum of an output of the line delay circuit and an output color signal of the first subtractor, a second attenuator that attenuates an output signal of the second adder, A line-type noise reduction circuit comprising a second subtractor for subtracting the output signal of the attenuator from the output color signal of the first subtractor, and only the components near the color carrier in the output color signal of the second subtractor Band cutoff circuit for cutting off, and an output of the band cutoff circuit A band attenuating circuit comprising a third attenuator for attenuating a signal, a third subtractor for subtracting an output signal of the third attenuator from an output color signal of the second subtractor, and an input color. A frame correlation detector for detecting a correlation between one frame of the signal, a line correlation detector for detecting a correlation during one horizontal scanning period, and the first signal based on output signals of the frame correlation detector and the line correlation detector. An attenuator, a gain control circuit for adjusting the amount of attenuation of each of the second attenuator and the third attenuator, and a degree of correlation between one frame of the input color signal and one horizontal scanning period. A color signal noise reduction circuit configured to reduce noise without causing an afterimage phenomenon or a rounding of a vertical contour by controlling attenuation amounts of the three attenuators in response thereto. 6. An apparatus for delaying an input color signal by one frame period.
A frame delay circuit, a first adder for summing an output of the one-frame delay circuit and an input color signal, a first attenuator for attenuating an output signal of the first adder, A frame-type noise reduction circuit comprising a first subtractor for subtracting the output signal of the attenuator from the input color signal; a one-line delay circuit for delaying the output color signal of the first subtractor for one horizontal scanning period; A second adder for summing an output of the delay circuit and an output color signal of the first subtractor;
Attenuator for attenuating the output signal of the adder, and a second subtractor for subtracting the output signal of the second attenuator from the output color signal of the first subtractor A frame correlation detector for detecting a correlation between one frame of the input color signal, a line correlation detector for detecting a correlation during one horizontal scanning period, and an output signal of the frame correlation detector and the line correlation detector. A gain control circuit for adjusting the amount of attenuation of each of the first attenuator and the second attenuator;
A color signal noise reduction circuit configured to control the amount of attenuation of the two attenuators according to the degree of correlation between horizontal scanning periods to reduce noise without causing an afterimage. 7. A method for delaying an input color signal by one frame period.
A frame delay circuit, a first adder for summing an output of the one-frame delay circuit and an input color signal, a first attenuator for attenuating an output signal of the first adder, A frame type noise reduction circuit comprising a first subtractor for subtracting an output signal of the attenuator from an input color signal; a band cutoff circuit for cutting off only a component near a color carrier in an output color signal of the first subtractor; A band attenuator for attenuating an output signal of the band cutoff circuit, and a second subtractor for subtracting an output signal of the second attenuator from an output color signal of the first subtractor. A noise reduction circuit, a frame correlation detector for detecting a correlation between one frame of the input color signal,
A gain control circuit that adjusts the amount of attenuation of each of the first attenuator and the second attenuator based on an output signal of the frame correlation detector, according to a degree of correlation between one frame of the input color signal. A color signal noise reduction circuit configured to control the amount of attenuation of the two attenuators to reduce noise without causing an afterimage phenomenon or a rounding of a vertical contour. 8. A method for delaying an input color signal by one horizontal scanning period.
A line delay circuit, a first adder for summing an output of the one-line delay circuit and an input color signal, a first attenuator for attenuating an output signal of the first adder, A line-type noise reduction circuit comprising a first subtractor for subtracting the output signal of the attenuator from the input chrominance signal; and a band rejection circuit for blocking only a component near the color carrier in the output color signal of the first subtractor. A band attenuator for attenuating an output signal of the band cutoff circuit, and a second subtractor for subtracting an output signal of the second attenuator from an output color signal of the first subtractor. A noise reduction circuit, a line correlation detector for detecting a correlation of the input color signal during one horizontal scanning period, and respective attenuations of the first attenuator and the second attenuator based on an output signal of the line correlation detector A gain control circuit for adjusting the amount, A color signal noise configured to reduce noise without causing a rounding in the vertical direction by controlling the amount of attenuation of the two attenuators according to the degree of correlation of one color scanning signal during one horizontal scanning period. Reduction circuit. 9. A color 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. Noise reduction circuit for television receivers.