JP2768550B2 - Noise removal device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise removing apparatus for a television receiver or the like, which automatically removes white noise contained in a luminance signal or a chroma signal.

2. Description of the Related Art In recent years, noise eliminators have been used in IDTV (Inproved Television) in which high-quality television images are required.
It has come to be commercialized as one of its essential functions. The noise removal in the IDTV is performed using a delay element provided in the IDTV, and further, the correlation between the luminance signal and the chroma signal is detected using the delay element, and the correlation between the luminance signal and the luminance signal is detected in accordance with the correlation between the respective signals. The chroma signal is independently and automatically denoised. As a conventional example of such a noise eliminator, a digital circuit for television signals Eto, Achiha
Television Academic Reference Book Series 6 Corona (198
9) ".

Hereinafter, a conventionally used noise elimination device will be described with reference to the drawings.

FIG. 4 is a block diagram showing a configuration of a conventional noise elimination device. In FIG. 4, 1 is a luminance signal input terminal, 2 is a subtractor for taking the difference between the output of the delay element 5 described later and the inputted luminance signal, 3 is a K-times circuit for multiplying the output of the subtracter 2 by K, 4 is an adder for taking the sum of the output of the K multiplying circuit 3 and the inputted luminance signal, 5 is a delay element for delaying the output of the adder 4 for a certain period of time, and 6 is a luminance signal from the output of the subtractor 2. Is a luminance signal parameter K control circuit for controlling the value of the parameter K of the K multiplication circuit 3 in accordance with the output of the correlation detection circuit 6, and 9 is an output connected to the adder 4. A luminance signal from which noise has been removed from the output terminal 9.

Reference numeral 10 denotes a chroma signal input terminal, 11 denotes a subtractor that takes a difference between an output from a delay element 14 to be described later and an input chroma signal, 12 denotes a K-times circuit that multiplies the output of the subtractor 11 by K, and 13 denotes a K-multiplier circuit. K
An adder for taking the sum of the output of the doubler circuit 12 and the input chroma signal, a delay element 14 for delaying the output of the adder 13 for a fixed period of time, and an output element 18 between the delay element 14 and the subtractor 11 An inverter mounted, 15 is a correlation detection circuit for detecting the correlation of the chroma signal by the output of the subtractor 11, and 16 is a chroma signal for controlling the value of the parameter K of the K-times circuit 12 according to the output of the correlation detection circuit 15. A parameter K control circuit 8 is an S / N ratio detection circuit for detecting an S / N ratio based on the input luminance signal, and its output terminal is connected to a luminance signal parameter K control circuit 7 and a chroma signal parameter K control circuit 16 and connected to the SN signal. Outputs a ratio detection signal. Reference numeral 17 denotes an output terminal connected to the adder 13. The output terminal 17 outputs a chroma signal from which noise has been removed.

The operation of the noise removal device configured as described above will be described below.

The noise eliminator uses the fact that the image information has a very strong autocorrelation at the frame period or the line period, and that the random noise has only a low energy of the noise component when averaged in those periods. The SN ratio has been improved. In FIG. 4, the output becomes a noise component by taking the difference between the luminance signal input by the subtractor 2 and the signal from which the noise was removed one cycle before, and the K-multiplier circuit 3 and the adder 4 output the noise component. The noise is removed by taking the average of the components, and is output from the luminance signal output terminal 9. Further, the value of the parameter K of the K multiplication circuit 3 is adaptively controlled by the luminance signal parameter K control circuit 7 in accordance with the correlation of the luminance signal, so that effective noise removal can be performed.

FIG. 5 shows a block diagram of the correlation detection circuit 6 in FIG. In FIG. 5, 19 is an input terminal of the correlation detection signal, 20 is a low-pass filter connected to the input terminal 19, 21
Is the absolute value circuit after the low-pass filter 20, 28, 29, 3
Reference numerals 0 and 31 denote comparators connected in parallel to the absolute value circuit 21; 22, 23 and 24 denote input terminals of preset thresholds input to the comparators 28, 29 and 30; 32 denotes a comparator 28 , 29, 30 are connected to the output terminals of the comparator 27. The adder 27 switches between a preset constant inputted to the threshold input terminal 25 and a constant 0 inputted to the input terminal 26 to the comparator 31. A switch for outputting, 33 is a one-pixel period delay element to which the output terminal of the comparator 31 is connected, 34 is an output terminal of a correlation detection signal to which the output terminal of the adder 32 is connected, and 35 is an output terminal of the delay element 33 Is an output terminal of the hysteresis signal to be connected.

Hereinafter, the operation of the correlation detection circuit 6 configured as described above will be described. First, the difference signal between one line of the luminance signal from the subtractor 2 input to the input terminal 19 passes through the low-pass filter 20 so that only the reduced component is extracted. The signals are input to the three comparators 28, 29 and 30, where they are respectively compared with preset threshold values. When the input signal is smaller than each threshold value, "1" is output from each comparator. Further, the sum of the outputs of the three comparators 28, 29 and 30 is calculated and output from the output terminal 34 as a correlation detection signal of the luminance signal. Accordingly, a larger value indicates a larger correlation, and a smaller value indicates a smaller correlation.

The signal output from the output terminal 35 has a function of stabilizing the operation of the correlation detection circuit 6 by providing a hysteresis to the correlation detection.

Next, the luminance signal parameter K control circuit 7 takes the sum of the two outputs calculated by the above method and the output of the SN ratio detection circuit 8, and outputs this value as a parameter K to the K multiplying circuit 3.

FIG. 6 shows a block diagram of the SN ratio detection circuit 8 in FIG. In FIG. 6, reference numeral 36 denotes an S / N ratio detection input terminal; 37, a band-pass filter connected to the input terminal 36; 38, a sampling circuit subsequent to the band-pass filter 37;
9, 40, 41 and 42 are one-line delay elements connected in series to the output terminal of the sampling circuit 38, and 43 is an adder, which adds the outputs of the one-line delay elements 39, 40, 41 and 42. . 44 is a 1/4 multiplier circuit, which multiplies the output of the adder 43 by 1/4. Reference numeral 45 denotes an SN ratio detection signal output terminal connected to the output terminal of the quarter circuit 44, and outputs an output signal of the SN ratio detection circuit 8.

 The operation of the above configuration will be described below.

First, the input signal is subjected to a band-pass filter 37 to remove the DC component of the luminance signal, and then a sampling circuit samples a portion of the composite video signal on which no video signal is superimposed. Element 39, 40,
The averaging on the four lines 41 and 42 is performed by the adders 43 and 1 /
It is calculated by the quadruple circuit 44 and output from the output terminal 45. By calculating the S / N ratio in a portion where no video signal is present, the S / N ratio can be calculated without being affected by the video signal.

Further, since the phase of the chroma signal is inverted at a constant period, noise can be removed by using the inverter 18 in the same manner as in the case of the luminance signal. However, since the chroma signal has a smaller amount of information than the luminance signal, no hysteresis is provided and the hysteresis output is always "1".

As described above, the noise between the luminance signal and the chroma signal can be adaptively and automatically removed by detecting the correlation between the luminance signal and the chroma signal and further detecting the SN ratio.

Problems to be Solved by the Invention However, in the above-described conventional configuration, since the correlation between the luminance signal and the chroma signal is not used, there is a problem that image quality deterioration such as color blur occurs in a video signal.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problem, and an object of the present invention is to provide a noise elimination device capable of suppressing image quality deterioration such as color fringing in a video signal.

Means for Solving the Problems In order to solve the above problems, the noise elimination device of the present invention,
First delay means for delaying the output luminance signal for a certain period of time, outputting the delayed signal, first subtraction means for obtaining a difference between the output from the first delay means and the input luminance signal, and an output of the first subtraction means A first K multiplying means for multiplying the output luminance signal by K, a first adding means for summing an output of the first K multiplying means and an input luminance signal to obtain the output luminance signal, and an output of the first subtracting means. A first correlation detecting means for detecting a correlation of the luminance signal, a second delay means for delaying the output chroma signal for a predetermined period and outputting the same,
A second subtraction means for obtaining a difference between an output from the second delay means and the input chroma signal, and an output of the second subtraction means being K
A second K multiplying means for multiplying the output, a second adding means for summing an output of the second K multiplying means and an input chroma signal to obtain the output chroma signal, and a chroma by the output of the second subtracting means. Second correlation detecting means for detecting a signal correlation; SN ratio detecting means for detecting an SN ratio of the input luminance signal;
Luminance for weighting the correlation output of the correlation detecting means and controlling the value of the parameter K of the first K multiplying means by the hysteresis output and the weighted correlation output of the first correlation detecting means and the output of the SN ratio detecting means. A signal parameter K control unit, a correlation output of the first correlation detection unit, a correlation output of the second correlation detection unit, and an output of the SN ratio detection unit are input, and the luminance signal correlation of the first correlation detection unit is input. A chroma signal parameter K control means for controlling a value of the parameter K of the second K multiplying means by switching a chroma signal parameter K in accordance with the output.

The luminance signal parameter K control means of the noise elimination device of the present invention includes a doubling means for weighting and doubling the correlation output of the first correlating means, a weighted correlation output from the doubling means, The output from the SN ratio detecting means, the first
And a third adding means for adding the hysteresis output of the correlation detecting means, wherein the output of the third adding means is used as the output of the luminance signal parameter K control means.

Further, the luminance signal parameter K control means of the noise elimination device of the present invention includes a fourth addition means for adding the correlation output of the second correlation means and the output of the SN ratio detection means, and a correlation of the first correlation means. Comparing means for comparing the output with the first predetermined value; and switch means for switching and outputting the output of the fourth adding means and the second predetermined value according to the output of the comparing means. The output is the chroma signal parameter K control means.

With the above-described configuration, a video signal with suppressed color fringing is obtained by detecting the correlation between the luminance signal and the chroma signal and adaptively controlling the parameter K of the K-times circuit in consideration of the correlation between them. It becomes possible.

Further, paying attention to the fact that the information amount of the luminance signal is larger and more detailed than the information amount of the chroma signal, the luminance signal correlation detection signal is weighted and doubled by the doubling means. , The noise removal effect is improved in reception in a strong electric field.

Further, the parameter K for the chroma signal is switched by the switch means in accordance with the correlation of the luminance signal to control the value of the parameter K of the second K multiplying means. Regardless of the detection result, the correlation between the chroma signals is reduced to suppress color fringing.

Embodiment Hereinafter, a noise removing apparatus according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a circuit configuration diagram of a noise elimination device in one embodiment of the present invention. In FIG. 1, 1
Is a luminance signal input means, 2 is a subtractor for taking a difference between an output of a delay element 5 described later and the inputted luminance signal, and 3 is a subtractor 2
A multiplier for summing the output of the K multiplier 3 and the input luminance signal, and 5 a delay element for delaying the output of the adder 4 by one fixed period and outputting the result. , 6 are correlation detection circuits for detecting the correlation of the luminance signal from the output of the subtracter 2;
Reference numeral 7a denotes a luminance signal parameter K for weighting the correlation output from the transport detection circuit 6 and controlling the parameter K of the K-times circuit 3 in accordance with the outputs of the correlation detection circuit 6 and the SN ratio detection circuit 8.
A control circuit 9 is an output terminal for a luminance signal from which noise has been removed.

Reference numeral 10 denotes a chroma signal input terminal, 11 denotes a subtractor that takes the difference between the output of the delay element 14 and the input chroma signal, 12 denotes a K-times circuit that multiplies the output of the subtractor 11 by K, and 13 denotes a K-times circuit. An adder for taking the sum of the output of 12 and the input chroma signal; 14 a delay element for delaying the output of the adder 13 for a certain period of time;
Is a correlation detection circuit for detecting the correlation of the chroma signal from the output of the subtractor 11, 16a is the circuit detection circuits 6, 15 and the SN ratio detection circuit 8
And a chroma signal parameter K control circuit for controlling the parameter K of the K multiplication circuit 12 by switching the chroma signal parameter K in accordance with the correlation output of the correlation detection circuit 6,
Reference numeral 18 denotes an inverter, 17 denotes an output terminal of a chroma signal from which noise has been removed, and 8 denotes an SN ratio detection circuit for detecting an SN ratio from a luminance signal input signal.

The operation of the noise removal device configured as described above will be described below. Although the principle of the noise elimination device has been described in the related art, in the present invention, the correlation between the luminance signal and the chroma signal is detected from each signal, and the image is obtained by utilizing the correlation between the luminance signal and the chroma signal. The color blur of the signal has been improved.

FIG. 2 is a block diagram of the luminance signal parameter K control circuit 7a in FIG. 1, and FIG. 3 is a block diagram of the chroma signal parameter K control circuit 16a in FIG. 2, reference numeral 46 denotes an input terminal of a luminance signal correlation detection signal from an output terminal 34 of the correlation detection circuit 6, and 47 denotes an output terminal of the correlation detection circuit 6.
Input terminal of the hysteresis signal from 35, input terminal 48 of the SN ratio detection signal from the output terminal 45 of the SN ratio detection circuit 8, 49 is a double circuit for doubling the luminance signal correlation detection signal, 50 is a double circuit. An adder 49 adds the input signals of 49 and input terminals 47 and 48, and 51 is a parameter K output terminal. In FIG. 3, reference numeral 52 denotes an input terminal of a luminance signal correlation detection signal from an output terminal 34 of the correlation detection circuit 6, 53 denotes an input terminal of a chroma signal correlation detection signal from the correlation detection circuit 15, and 54 denotes an SN ratio detection. This is an input terminal of the SN ratio detection signal from the circuit 8. 55 is comparator 60
The comparator 60 compares the luminance signal correlation detection signal with the threshold value. 56 is an adder for adding the input signals of the input terminals 53 and 54, 57 is an input terminal of a preset threshold, and 58 is an output of the adder 56 and a threshold input terminal 57 according to the output of the comparator 60. This is a switch for switching between the input threshold value. 59 is a switch
This is a parameter K output terminal of a chroma signal connected to 58.

Hereinafter, the operation of the parameter K control circuit for the luminance signal and the chroma signal will be described. First, although the basic configuration of the parameter K control circuit is conventionally a simple addition of the correlation detection signal, the SN ratio detection signal, and the hysteresis output signal, in the present invention, the information amount of the luminance signal in the video signal is smaller than the information amount of the chroma signal. Paying attention to the fact that the correlation signal is thin and large, the correlation detection signal is weighted as shown in FIG.
A doubling circuit 49 for doubling is used. This improves the noise removal effect even in reception in a strong electric field. Also,
In the control of the parameter K in the chroma signal, a luminance signal having a large amount of information is used, and a switch 58 for switching the parameter K for the chroma signal in accordance with the correlation of the luminance signal is used. Specifically, the property that the chroma signal generally changes at the change point of the luminance signal is used. When the correlation of the luminance signal is small, the correlation of the chroma signal is reduced regardless of the result of the correlation detection of the chroma signal. . With the above-described method, it is possible to configure a noise elimination device that suppresses color blur and the like as compared with the conventional noise elimination device.

Effects of the Invention As described above, according to the present invention, it is possible to configure an adaptive noise elimination device capable of suppressing color fringing and the like as compared with a conventional noise elimination device.

[Brief description of the drawings]

FIG. 1 is a block diagram of a noise eliminator showing an embodiment of the present invention, and FIG. 2 is a block diagram of a luminance signal parameter K shown in FIG.
FIG. 3 is a block diagram of a chroma signal parameter K control circuit in FIG. 1, FIG. 4 is a block diagram of a conventional noise elimination device, and FIG. 5 is a block diagram of a correlation detection circuit in FIG. FIG. 6 is a block diagram, and FIG.
FIG. 3 is a block diagram of an SN ratio detection circuit. 2, 11,... Subtracter, 3, 12,... K-times circuit, 4, 13, 50,
56 ... Adder, 5, 14 ... Delay element, 6, 15 ... Correlation detection circuit, 7a ... Luminance signal parameter K control circuit, 8 ...
... SN ratio detection circuit, 16a ... Chroma signal parameter K control, 49 ... double circuit, 58 ... switch, 60 ... comparator.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-64-71287 (JP, A) JP-A-62-285583 (JP, A) JP-A-62-290270 (JP, A) JP-A 63-28270 111772 (JP, A) Fully open 1988-140774 (JP, U) Fully open 1986-140684 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) H04N 5/14-5 / 217 H04N 9/77

Claims (3)

(57) [Claims] A first delay means for delaying an output luminance signal for a predetermined period and outputting the first luminance signal; a first subtraction means for calculating a difference between an output from the first delay means and an input luminance signal; A first K multiplying means for multiplying the output of the subtracting means by K, a first adding means for summing an output of the first K multiplying means and an input luminance signal to obtain the output luminance signal, A first correlation detecting means for detecting a correlation of a luminance signal by an output of the subtracting means, a second delaying means for delaying and outputting an output chroma signal for a predetermined period, and an output and an input from the second delaying means. Second subtraction means for taking the difference between the chroma signals, second K-times means for multiplying the output of the second subtraction means by K, and taking the sum of the output of the second K-times means and the input chroma signal. A second adding means for obtaining the output chroma signal, and a chroma signal based on an output of the second subtracting means. Second correlation detecting means for detecting the correlation of the input luminance signal, SN ratio detecting means for detecting the SN ratio of the input luminance signal, and weighting the correlation output of the first correlation detecting means. The hysteresis output, the weighted correlation output, and the output of the SN ratio
A luminance signal parameter K control unit for controlling the value of the parameter K of the K times unit, a correlation output of the first correlation detection unit, a correlation output of the second correlation detection unit, and an output of the SN ratio detection unit. And a chroma signal parameter K control means for switching the chroma signal parameter K in accordance with the luminance signal correlation output of the first correlation detecting means to control the value of the parameter K of the second K multiplying means. Noise removal equipment provided. 2. A luminance signal parameter K control means, comprising:
Doubling means for weighting and doubling the correlation output of the correlating means, and the weighted correlation output from the doubling means and
A third adding means for adding an output from the SN ratio detecting means and a hysteresis output of the first correlation detecting means, wherein the third adding means output is the luminance signal parameter K control means output. Item 3. The noise removing device according to Item 1. 3. The chroma signal parameter K control means includes: fourth addition means for adding the correlation output of the second correlation means and the output of the SN ratio detection means; and the correlation output of the first correlation means and the first output. And a switch for switching the output of the fourth adder and the second predetermined value by the output of the comparator, and outputting the output of the switch for the chroma signal. 2. The noise eliminator according to claim 1, wherein the output is a parameter K control means.