JPH08168021A - Noise reducing device - Google Patents

Abstract

PURPOSE: To improve the S/N feeling of the whole screen without causing deterioration in the resolution of a fine pattern on the screen. CONSTITUTION: This device is equipped with a noise removing circuit 1 which improves the S/N of a video signal, a timing adjusting circuit 2 which adjusts the timing between the output of the noise removing circuit 1 and the video signal, a uniform image detecting circuit 3 which decides a uniform image area of the video signal, and a video signal switching circuit 4 which switches the output of the noise removing circuit 1 and the output of the timing adjusting circuit 2 on the basis of the uniform image detecting circuit 2 and outputs the video signal. The whole screen is divided into the uniform image area and a fine pattern area by the uniform image detecting circuit 3 and only for the uniform image area, a noise removing processing is performed by switching to the noise removing circuit 1 through the video signal switching circuit 4 to improve the apparent S/N feeling of the whole screen without deteriorating the resolution of the fine pattern.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise reducing device used in a video equipment such as a television, a VTR or a video camera.

[0002]

2. Description of the Related Art In recent years, noise reduction devices for reducing noise have been installed in home VTRs, video cameras and the like. The noise reduction device is a device for reducing noise included in an image signal to improve image quality.

Since an image generally has a strong correlation, noise is random and non-correlated. Therefore, if the two can be efficiently separated, the image quality can be greatly improved. FIG. 8 shows the first
2 shows a noise reduction device of the related art. In FIG. 8, 101 is a low pass filter, 102 is a high pass filter, 103 is a coring circuit, and 104 is an adder.

The operation of the noise reduction device of the first conventional example constructed as described above will be described below. First, the high-pass component of the video signal is extracted by the high-pass filter 102. Further, among the extracted high frequency components, only those having a small amplitude are removed by the coring circuit 103 and combined with the output of the low pass filter 101 by the adder 104. FIG. 9 shows an example of the input / output characteristics of the coring circuit. When the threshold value is Δ / 2, the input signal Ein is −Δ / 2 ≦ Ein ≦
In the case of Δ / 2, the output signal Eout = 0 and Ein>
When Δ / 2 or Ein <−Δ / 2, Eout = Ein. This coring circuit can be configured by a logic circuit, but can be easily realized by ROM conversion. As a result, sharp edges are preserved as they are, and fine noise is removed.

FIG. 10 shows a noise reducing device of a second conventional example. In FIG. 10, 105 is a 1H line memory that delays a video signal for a 1H period, 106 is a subtractor that finds the difference between a video signal that is delayed by one line and a video signal that is not delayed, and 107 is a high frequency component for extracting high-frequency components in the horizontal direction. A band-pass filter, 108 is a non-linear processing circuit for extracting only high-frequency components with small amplitude, and 109 is a subtracter for subtracting high-frequency components with small amplitude extracted by the non-linear circuit 108 from the original signal.

The operation of the second conventional noise reducing device configured as described above will be described below. First, the difference between the video signal delayed by the 1H line memory 105 for 1H period and the video original signal is calculated by the first subtractor 106, and the high-pass filter 107 extracts the horizontal high-frequency component. The obtained signal has a high-frequency component in both the horizontal and vertical directions and can be regarded as almost noise, but also includes a signal component having a correlation in the diagonal direction. Of these signals, only the signal having a small amplitude is extracted as a noise signal by the non-linear processing circuit 108, and noise is removed by subtracting it from the original signal by the second subtractor 109, thereby improving the image quality.

The non-linear processing circuit 108 is a circuit having an input / output characteristic as shown in FIG.
Is −Δ / 2 ≦ Ein ≦ Δ / 2, the output signal Eout
= Ein, and Ein> Δ / 2 or Ein <−Δ /
At 2, Eout = 0. This non-linear processing circuit can be realized by, for example, a ROM conversion circuit or the like.

[0008]

However, the above-mentioned conventional noise reduction device has the following problems. That is, in the first conventional example, a high-frequency signal component having a small amplitude in the horizontal direction is regarded as noise and is removed, so that a fine pattern in the screen is a flat image with degraded resolution. There was a problem that became.

Further, in the second conventional example, of the high-frequency signal components in both the horizontal and vertical directions, those having a small amplitude are regarded as noise and are removed, so that a fine pattern in the diagonal direction on the screen is flat. There was a problem that an image with degraded resolution was obtained. Therefore,
An object of the present invention is to solve the above-mentioned conventional problems, and to provide a noise reduction device that improves the SN feeling of the entire screen without causing deterioration of resolution in a fine pattern in the screen.

[0010]

A noise reduction device according to claim 1 is a noise reduction circuit for improving the SN of a video signal, and a timing adjustment circuit for adjusting the timing between the output of the noise removal circuit and the video signal. A uniform image detection circuit that determines a uniform image area of a video signal, and a video that outputs a video signal by switching the output of the noise removal circuit and the output of the timing adjustment circuit based on the output of this uniform image detection circuit And a signal switching circuit.

According to a second aspect of the present invention, there is provided a noise reducing device for improving the SN of a video signal, a timing adjusting circuit for adjusting the timing between the output of the noise removing circuit and the video signal, and a uniform image of the video signal. A uniform image detection circuit that discriminates an area and outputs a value indicating the uniform image degree, and outputs of the uniform image detection circuit when combining the output of the timing adjustment circuit and the output of the noise removal circuit. A synthesis coefficient generation circuit for calculating an output ratio, and image synthesis for outputting a synthesized video signal after weighting the output of the noise removal circuit and the output of the timing adjustment circuit based on the output of the synthesis coefficient generation circuit And a circuit.

[0012]

According to the structure of claim 1, the entire screen is divided into the uniform image area and the fine picture area by the uniform image detecting circuit, and the noise is removed by the video signal switching circuit only in the uniform image area. By switching to the circuit and performing the noise removal processing, it is possible to improve the SN appearance of the entire screen without degrading the resolution of the fine pattern.

According to the structure of claim 2, the entire screen is divided into a uniform image area and a fine pattern area which is not so by the uniform image detecting circuit, and a value indicating the uniform image degree is given to each area. Then, based on this value, the synthesis coefficient generation circuit calculates the output ratio of the timing adjustment circuit and the noise removal circuit. Based on this ratio, the image synthesis circuit outputs the output of the timing adjustment circuit and the output of the noise removal circuit. Since they are weighted and then combined, the noise removal rate can be controlled in accordance with the value indicating the uniform image degree. As a result, the uniform image area with improved SN and the fine pattern area with a sense of resolution are more naturally harmonized without deteriorating the resolution of the fine pattern, and the overall sense of SN of the screen is improved. can do.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A noise reducing device according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram showing the configuration of the noise reduction device according to the first embodiment. As shown in the figure, this noise reduction device includes a noise removal circuit 1, a timing adjustment circuit 2, a uniform image detection circuit 3, and a video signal switching circuit 4.

The noise removing circuit 1 improves the SN of a video signal and is a conventional circuit for removing noise by using a video signal in a field as shown in FIG. 8, for example.
Therefore, in the output of the noise removing circuit 1, the SN is improved but the resolution of the fine pattern area is deteriorated. The timing adjusting circuit 2 adjusts the timing between the output of the noise removing circuit 1 and the video signal.
Noise reduction circuit 1
The input video signal is output at the same timing as the output of. Since the output of the timing adjustment circuit 2 is the input video signal itself, the SN is not improved but the resolution is not deteriorated.

The uniform image detection circuit 3 discriminates a uniform image area from the video signal and outputs an ON / OFF key signal. The video signal switching circuit 4 switches the output of the noise removal circuit 1 and the output of the timing adjustment circuit 2 based on the output of the uniform image detection circuit 3 and outputs a video signal. Also,
In the above description, no reference was made to the configuration of the uniform image detection circuit 3, but any uniform image detection circuit may be used as long as it is a circuit that determines a uniform image area in a video. It is clear that can be configured.

For example, a configuration as shown in FIG. 2 can be considered. FIG. 2 shows a block division circuit 10 and an image discrimination circuit 1.
It is composed of a 1-binarization circuit 12. The block division circuit 10 divides the screen into blocks, and calculates the average value of the video signal and the histogram of the video signal for each block. Further, it is determined whether or not the image is a uniform image based on the histogram state which is the characteristic of the detected image.
For example, as shown in FIG. 3A, when the histogram shows a distribution concentrated around the average value in the block area, it is determined as a uniform image, and as shown in FIG. If they are scattered, it is determined that the image is not a uniform image, and the binarization circuit 12 performs binarization to generate an ON / OFF signal indicating whether the image is a uniform image or not.

A configuration as shown in FIG. 4 is also conceivable. FIG. 4 shows an edge detection circuit 13, an image discrimination circuit 11,
It is composed of a binarization circuit 12. 3 independent of each other
Edge detection is performed on each of the signals (for example, Y, Pr, and Pb) by the edge detection circuit 13 using methods such as first derivative (gradient), second derivative (Laplacian), and template matching (Prwitt), and the contour is detected. The output value corresponding to the strength of the signal is output, and the image determination circuit 11 determines the image area of the flat portion for all three signals by the threshold value. Further, the binarization circuit 12 turns ON /
Generates an OFF signal.

A configuration as shown in FIG. 5 is also conceivable. FIG. 5 is composed of a uniform image setting circuit 14, an image data discrimination circuit 15, and a binarization circuit 12. The uniform image setting circuit 14 preliminarily captures image data of a uniform image on the screen by an operator. Further, the image data discriminating circuit 15 discriminates whether or not the image is a uniform image by comparing with the captured image data, and the binarizing circuit 12 turns ON.
/ OFF signal is generated.

In addition to this, various constitutions such as uniform image discrimination by a neuron are conceivable, but any uniform image detecting circuit can be used as long as it is a circuit for discriminating a uniform image region in a video. It is clear that the invention can be constructed. Regarding the noise reduction device configured as described above,
The operation will be described below.

First, the input video signal is input to the noise removal circuit 1, the timing adjustment circuit 2, and the uniform image detection circuit 3. The uniform image detection circuit 3 determines whether the input image signal is a uniform image or a fine pattern image other than the input video signal, and determines whether the image is a uniform image ON / O.
The FF key signal is output to the video switching circuit 4. The video switching circuit 4 selects either the noise removal circuit 1 output or the timing adjustment circuit 2 output depending on an ON / OFF key signal from the uniform image detection circuit 3 indicating whether the image is a uniform image. And output.

That is, the output of the noise removal circuit 1 with improved SN is selected for the area determined to be a uniform image, and the output of the timing adjustment circuit 2 with no resolution deterioration is selected for the other small picture area. . In the uniform image area, there is no signal of a pattern that is determined to be noise, so even if the conventional noise removal circuit processing is performed, deterioration of resolution does not occur and only the noise component is removed and SN is improved. Further, when the noise removal circuit 1 processes the area determined not to be a uniform image, even the signal component due to the fine pattern is removed at the same time, and therefore, the output of the timing adjustment circuit 2 without resolution deterioration is selected.

As described above, in this embodiment, the entire screen is divided into the uniform image area and the fine picture area by the uniform image detecting circuit 3, and the video signal switching circuit is applied only to the uniform image area. By switching to the noise removal circuit 1 and performing noise removal processing in 4, it is possible to improve the SN appearance of the entire screen without degrading the resolution of the fine pattern.

A noise reducing apparatus according to the second embodiment of the present invention will be described with reference to FIGS. 6 and 7. FIG. 6 is a block diagram showing the configuration of the noise reduction device according to the second embodiment. As shown in the figure, this noise reduction device includes a noise removal circuit 1, a timing adjustment circuit 2, a uniform image detection circuit 3, a synthesis coefficient generation circuit 5, and an image synthesis circuit 6.

Noise removal circuit 1 and timing adjustment circuit 2
Is the same as in the first embodiment. Uniform image detection circuit 3 '
Determines a uniform image area from the video signal and outputs a value indicating the uniform image degree. That is, the uniform image detection circuit 3'is the same as the uniform image detection circuit 3 of the first embodiment except that the binarization circuit is omitted, and the uniform key detection circuit 3'is not ON / OFF but can be switched by a soft key. A signal indicating the image intensity can be obtained. The synthesizing coefficient generating circuit 5 calculates a synthesizing coefficient which is a ratio of respective outputs when synthesizing the output of the timing adjusting circuit 2 and the output of the noise removing circuit 1 with the output of the uniform image detecting circuit 3 '. The image synthesizing circuit 6 weights the output of the noise removing circuit 1 and the output of the timing adjusting circuit 2 based on the output of the synthesizing coefficient generating circuit 5, and then outputs a synthesized video signal.
First multiplier 7, second multiplier 8 and first adder 9
It is composed by.

The operation of the noise reducing device configured as described above will be described below. First, the input video signal is input to the noise removal circuit 1, the timing adjustment circuit 2, and the uniform image detection circuit 3 '. The uniform image detection circuit 3'determines whether the input image signal is a uniform image or a fine pattern image, and outputs a value indicating the uniform image degree to the synthesis coefficient generation circuit 5. To do.

In the synthesizing coefficient generating circuit 5, the output of the noise removing circuit 1 and the output of the timing adjusting circuit 2 which are mixed in the image synthesizing circuit 6 according to the value indicating the uniform image degree which is the output of the uniform image detecting circuit 3 '. Calculate the ratio k and the coefficient of 1-k. The combination coefficient generation circuit 5 may have any input / output relationship as long as it can determine the combination coefficients k and 1-k from the uniform image degree.

FIG. 7 shows an example of input / output characteristics of the synthesis coefficient generating circuit 5. In the synthesis coefficient generation circuit 5 of this example, a value x indicating a uniform image degree (when x = 1.0, a perfect uniform image, x = 0.
When 5, the probability of being a uniform image is 50%, and when x = 0.0,
Suppose that the image is not completely uniform. ) Multiplied by the output dependency y of the noise removal circuit (maximum dependency when y = 1.0, zero dependency when y = 0) is used as the synthesis coefficient k of the output of the noise removal circuit 1 for the image synthesis circuit 6. It is output to the multiplier 7. The output dependency y of the noise removing circuit 1 indicates the ratio of the output of the noise removing circuit 1 in the image area where the uniform image detecting circuit 3'determines that the image is a completely uniform image. It can also be understood as a value that controls the effectiveness of the noise reduction device. At the same time, 1-k is output to the multiplier 8 of the image composition circuit 6 as a composition coefficient of the timing adjustment circuit 2.

In the image synthesizing circuit 6, the multiplier 7 multiplies the synthesizing coefficient k of the output of the noise removing circuit 1 by the output of the noise eliminating circuit 1, and the multiplier 8 of the synthesizing coefficient 1-of the output of the timing adjusting circuit 2. k is multiplied by the output of the timing adjustment circuit 2, and the adder 9 adds and synthesizes them to output as a video signal. As described above, in this embodiment, the entire screen is divided by the uniform image detection circuit 3'into a uniform image region and a fine pattern region which is not so, and a value indicating the uniform image degree is assigned to each region. The output of the timing adjustment circuit 2 and the noise removal circuit 1 are calculated by the synthesis coefficient generation circuit 5 based on this value, and the output of the timing adjustment circuit 2 and the noise are calculated by the image synthesis circuit 6 based on this ratio. Since the output of the removal circuit 1 is weighted and then combined, the noise removal rate can be controlled in accordance with the value indicating the uniform image degree. As a result, the uniform image area with improved SN and the fine pattern area with a sense of resolution are more naturally harmonized without deteriorating the resolution of the fine pattern, and the overall sense of SN of the screen is improved. can do.

In the above description, no reference was made to the configuration of the noise removing circuit 1, but any noise removing circuit may be used as long as it is a circuit that removes noise using the video signal in the field. .

[0031]

According to the noise reducing apparatus of the first aspect, the entire screen is divided into the uniform image area and the fine picture area by the uniform image detecting circuit, and the video signal is switched only to the uniform image area. By switching to the noise removal circuit in the circuit and performing the noise removal processing, it is possible to improve the SN appearance of the entire screen without degrading the resolution of the fine pattern.

According to the noise reducing apparatus of the second aspect, the entire screen is divided by the uniform image detecting circuit into a uniform image region and a fine pattern region which is not so.
A value indicating the uniform image degree is output, the ratio of the timing adjustment circuit and the noise removal circuit output by the synthesis coefficient generation circuit is calculated based on this value, and the image synthesis circuit calculates the ratio of the timing adjustment circuit and the noise removal circuit based on this ratio. Since the output and the output of the noise removal circuit are weighted and then combined, the noise removal rate can be controlled in accordance with the value indicating the uniform image degree. As a result, the uniform image area with improved SN and the fine pattern area with a sense of resolution are more naturally harmonized without deteriorating the resolution of the fine pattern, and the overall sense of SN of the screen is improved. can do.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a noise reduction device according to a first exemplary embodiment of the present invention.

FIG. 2 is a block diagram showing an example of a uniform image detection circuit.

FIG. 3 is an explanatory diagram showing the judgment criteria.

FIG. 4 is a block diagram showing another example of a uniform image detection circuit.

FIG. 5 is a block diagram showing still another example of a uniform image detection circuit.

FIG. 6 is a block diagram showing a configuration of a noise reduction device according to a second exemplary embodiment of the present invention.

FIG. 7 is an input / output characteristic diagram of a synthesis coefficient generation circuit.

FIG. 8 is a block diagram showing a configuration of a noise reduction device of a first conventional example.

FIG. 9 is an input / output characteristic diagram of the coring circuit.

FIG. 10 is a block diagram showing a configuration of a noise reduction device of a second conventional example.

FIG. 11 is an input / output characteristic diagram of a nonlinear processing circuit for noise component extraction.

[Explanation of symbols]

 1 noise removal circuit 2 timing adjustment circuit 3, 3'uniform image detection circuit 4 video signal switching circuit 5 synthesis coefficient generation circuit 6 image synthesis circuit

Claims (2)

[Claims] 1. A noise removing circuit for improving the SN of a video signal, a timing adjusting circuit for adjusting the timing of the output of the noise removing circuit and the video signal, and a uniform for discriminating a uniform image region of the video signal. A noise reduction device comprising: an image detection circuit; and a video signal switching circuit that switches the output of the noise removal circuit and the output of the timing adjustment circuit based on the output of the uniform image detection circuit to output a video signal. 2. A noise removing circuit for improving the SN of a video signal, a timing adjusting circuit for adjusting the timing between the output of the noise removing circuit and the video signal, and a uniform image region of the video signal is discriminated and the uniformity thereof is determined. A uniform image detection circuit that outputs a value indicating the image intensity, and a ratio of each output when combining the output of the timing adjustment circuit and the output of the noise removal circuit by the output of the uniform image detection circuit And a picture synthesizing circuit for outputting a synthesized video signal after weighting the output of the noise removing circuit and the output of the timing adjusting circuit based on the output of the synthesizing coefficient generating circuit. A noise reduction device equipped.