JP2524009B2 - Noise reduction device and noise reduction imaging device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention uses a field, frame, or line correlation of a video output of a television, a video camera, a video camera or the like to prevent deterioration of an original image such as an afterimage even in a moving image. The present invention relates to a noise reduction device for reducing noise, and particularly to a sampling frequency of each signal and a signal processing band when an input signal is a component signal.

[0002]

2. Description of the Related Art A conventional noise reduction device is disclosed in, for example, Japanese Patent Application Laid-Open No. 61-158574.

A conventional noise reduction device will be described below. FIG. 8 is a block diagram showing the configuration of a conventional noise reduction device.

In FIG. 8, 1 is an input terminal for a composite video signal, 2 is an A / D converter for converting a composite input video signal from an analog signal to a digital signal, and 3 is two input signals, one of which is an input signal. And a subtraction circuit 4 for subtracting the other input signal from the input video signal is a frame memory for delaying the noise reduced signal from the input video signal by one frame. Since the color signal of the NTSC color video signal is phase-inverted for each frame, 5 is a color signal phase shift circuit for compensating for this, and only the color signal of the video signal delayed by the frame memory 4 is phased. Invert. 6 is a subtraction circuit for subtracting an input video signal and a video signal delayed by one frame to obtain a difference signal (frame difference signal), 7 is a Hadamard transform for extracting a vertical component, a horizontal component, and a diagonal component from the frame difference signal Circuit. Since the output of the Hadamard transform circuit 7 has different distributions of noise components and motion components,
Reference numeral 8 is a non-linear processing circuit that utilizes this to extract a noise component. Reference numeral 9 is a Hadamard inverse transform circuit, and since the noise signal extracted from the non-linear processing circuit 8 is obtained by Hadamard transform, it is returned to the original time axis by Hadamard inverse transform. Reference numeral 10 is a D / A converter for converting a digital signal into an analog signal.

In the conventional noise reduction device configured as described above, when the composite video signal is input from the input terminal 1, it is converted into a digital signal by the A / D converter 2, and this digital signal passes through the subtractor 3. Thus, a non-correlation component, which will be described later, is subtracted, ideally a video signal component that does not include a noise component, is stored in the frame memory 4, and is delayed for one frame. It is each pixel point of the m frame shown in FIG. Since the phase of the color signal of the video signal delayed by this one frame is inverted from that of the original one frame signal, the phase is compensated by the color signal phase shift circuit 5 and only the phase of the color signal is inverted. , Subtractor 6
Thus, a difference signal (frame difference signal) between two video signals having the same chroma phase is obtained. Originally, when the input video signal is a still image, this frame difference signal becomes a noise component itself, and noise can be extracted without the need for the circuit described below. However, when the input video signal is a moving image, the frame difference signal is a signal in which a signal component having no frame correlation and a noise component are combined.

A method for obtaining only the noise component from the frame difference signal will be described below. The frame difference signal is divided into a low frequency component, a vertical direction component, a horizontal direction component, etc. by the Hadamard conversion circuit 7. In this case, one pattern picture element of the input is as shown in FIG. 9, and the input is

[0007]

[Equation 1]

[0008] When the conversion output of the 2 × 4th order Hadamard transform is F ₂₄ , the following expressions (2) and (3) are obtained.

[0009]

[Equation 2]

[0010]

(Equation 3)

From the above equations (Equation 1) to (Equation 3), the output F _{24 of} Hadamard transform is obtained from the 2 × 4th order input picture element X ₂₄ . H ₂ and H ₄ are as in (Equation 4) and (Equation 5).

[0012]

[Equation 4]

[0013]

(Equation 5)

The output from the Hadamard conversion circuit 7 becomes an 8-component conversion output. On the other hand, since noise has no correlation, it is distributed substantially evenly over the frequencies of the eight components of the output of the Hadamard transform circuit 7. Since the noise level at the output of the Hadamard transform circuit 7 corresponds to the noise level of the input signal as is well known, only a small level noise component can be extracted from these components through the nonlinear processing circuit 8. Since each component extracted by the non-linear processing circuit 8 is obtained by Hadamard transform, it is returned to the original time axis by passing through the Hadamard inverse transform circuit 9, where a parallel digital noise signal is obtained. Become. The signal obtained here is obtained by extracting only the noise component from the frame difference signal having no frame correlation, and is supplied to the subtraction circuit 3 to obtain the noise-free digital video signal by subtracting the noise component from the input video signal. Will be done. Finally, the D / A converter 10 converts the digital video signal into the original analog signal and outputs it.

A noise reduction device using such a method is
In principle, there is a possibility that noise reduction can be performed on a moving image as well as a still image at the input of a composite video signal without significantly degrading the input video.

[0016]

In principle, the noise reduction device described in the prior art can reduce noise by inputting a video signal without producing an afterimage not only in a still image but also in a moving image.

However, in the above conventional configuration, when the input signal is a component signal, for example, an optimal configuration has not been proposed for signals having different signal bands such as a luminance signal and a color difference signal.

The present invention solves the above-mentioned conventional problems, provides an optimum circuit configuration when an input signal is a component signal, and provides a noise reduction device which is most advantageous in terms of circuit scale. The purpose is to

[0019]

In order to achieve this object, a noise reduction apparatus of the present invention is a noise reduction apparatus that quantizes a plurality of component video signals at independent frequencies and then decomposes them into different characteristic components independently of each other. In the noise reduction device via the removing means, each of the noise removing means includes first subtracting means for obtaining a difference component between each input video signal and an output signal of the n (n> 0) field delay means, and the first subtracting means. Feature extraction means for decomposing the output of the first subtraction circuit into a plurality of feature components, non-linear processing means for performing non-linear processing on at least one of the feature components, and a difference between the output of the non-linear processing means and the input video signal. The second subtraction means for obtaining a signal and the n-field delay means for delaying the output signal from the second subtraction means.

[0020]

According to the present invention, the quantization frequency of each component input video signal is made independent and the feature extraction components are made different from each other by the above-mentioned configuration, so that it is effective from each signal component of the component input video signal. The noise can be removed.

[0021]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a noise reducing apparatus according to the first embodiment of the present invention. 1, the components 1 to 6 are the same as those shown in FIG.
Do the same thing. Reference numeral 21 is a circuit configuration shown in FIG. 2, 7 is a 2 × 4th order Hadamard transform circuit, and 80 is a non-linear processing circuit group. Reference numeral 9 denotes a 2 × 4 order Hadamard transform circuit, which is 2
Reference numeral 1 is a circuit configuration including a series of processes, and reference numerals 7 and 9 are circuits similar to the Hadamard transform circuit 7 and the Hadamard inverse transform circuit 9 shown in FIG. 10 is D shown in FIG.
It is similar to the / A conversion circuit 10 and has a similar function. Two
2 is an input terminal for the color difference signal BY, 28 is a color difference signal RY
Input terminals 23, 29 are A / D converters for converting BY of the input signals from analog signals to digital signals, 2
4, 30 are frame memories for storing one frame of each of BY and RY signals, 25 is a circuit configuration shown in FIG. 3, 40 is a 2 × 8 order Hadamard conversion circuit, and 41 is a non-linear processing circuit. The group 42 is a 2 × 8-order inverse Hadamard transform circuit, which has a circuit configuration including a series of processes. 26 and 31 are D
An A / A converter, 27 is an output terminal for the color difference signal BY, and 32 is an output terminal for the color difference signal RY.

The operation of the noise reducing apparatus of this embodiment having the above-mentioned structure will be described below. When a luminance signal is input as a component signal from the input terminal 1, it is sampled by the A / D converter 2 at 4f _sc (however, it is not limited to this frequency) and converted from an analog signal to a digital signal. A non-correlation component described later is subtracted from this signal by passing through the subtractor 3 and ideally becomes a luminance signal containing no noise component. This luminance signal is stored in the frame memory 4 and delayed for one frame, and the subtracter 6 obtains a frame difference signal of the two luminance signals. The frame difference signal is a signal in which a signal component (motion component) having no frame correlation and a noise component are combined. This frame difference signal enters the 2 × 4th order Hadamard transform processing circuit group 21 and the 2 × 4th order Hadamard transform circuit 7 converts the frame difference signal into eight 2 such as low frequency components, vertical frequency components and horizontal frequency components. Dimensional frequency component. At this time, the spectrum appearing in the horizontal direction has an energy distribution centered on the spectrum shown in FIG. 4 when the sampling frequency is 4 fsc. This is a spectrum on the band of the luminance signal, and the distribution interval of the spectrum is almost constant. The frame difference signal input to the 2 × 4th order Hadamard conversion circuit 7 is replaced with a signal component on the frequency axis by being 2 × 4th order Hadamard conversion. Since the video signal of the output of the 2 × 4th order Hadamard conversion circuit 7 has correlation on the frequency axis, energy is distributed on a biased spectrum. On the other hand, since noise has no correlation on the frequency axis, it is substantially evenly distributed in the frequency distribution of the eight components of the output of the Hadamard transform circuit 7. As is well known, the noise level at the output of the Hadamard transform circuit 7 corresponds to the noise level of the input signal. By performing the processing, only a low level noise component can be extracted from the eight components. Since each component extracted by the non-linear processing circuit group 80 is obtained by the 2 × 4 order Hadamard transform, 2 × 4
It is returned to the original time axis by passing through the next Hadamard inverse transform circuit 9. The signal obtained here is obtained by extracting only the noise component from the frame difference signal having no frame correlation, and is supplied to the subtraction circuit 3 as described above. By subtracting the noise component from the input luminance signal, the noise-free digital signal is obtained. A luminance signal will be obtained. Then, the D / A converter 10 converts the digital video signal into the original analog signal and outputs it from the output terminal 11.

Next, processing of the color difference signal which is a component signal will be described. BY and RY are input from the input terminals 22 and 28, respectively. Since the band of the chrominance signal is approximately 1/4 of the band of the luminance signal, the sampling frequency of 1/4 of the sampling frequency of the luminance signal is sufficient. Therefore, the input color difference signal is the A / D converter 2
3 and 29, f of the sampling frequency of 1/4 of the luminance signal
_sc (3 when the sampling frequency of the luminance signal is 3 fsc
/ 4f _sc ) sampling frequency,
The analog signal is converted into a digital signal. The two color difference signals input to the BY input signal and the RY input signal are subjected to subtractors 3B and 3R to be subjected to subtraction of a non-correlation component, which will be described later, and ideally, a color difference signal containing no noise component. It becomes an ingredient. The color difference signals of each of these are stored in the frame memory 2
The frame difference signals of the color difference signals are obtained by the subtracters 6B and 6R. This frame difference signal is a signal in which a signal component having no frame correlation and a noise component are combined. This frame difference signal is a 2 × 8th order Hadamard transform processing circuit group 25.
B, 25R are entered and converted into signal components on the frequency axis by the 2 × 8 Hadamard transform.

Here, the 2 × 8-order Hadamard transform will be described in detail. Input

[0026]

(Equation 6)

Then, the output of the 2 × 8 Hadamard transform is

[0028]

(Equation 7)

[0029]

(Equation 8)

It becomes The output of the 2 × 8th order Hadamard transform is obtained by (Equation 8). H ₂ and H ₄ are as in (Equation 9) and (Equation 10).

[0031]

[Equation 9]

[0032]

[Equation 10]

The color difference signal obtained by dividing the frame difference signal by the 2 × 8th order Hadamard conversion circuit 40 into frequency components such as low frequency components, vertical frequency components and horizontal frequency components is
It is sampled at f _sc (3/4 f _sc is also possible), and in this case, the signal processing speed in the circuit is 1 for the luminance signal.
/ 4, the conversion order of the Hadamard conversion of the color signal can be set larger than that of the luminance signal due to the circuit scale, and 2 ×
Eighth-order two-dimensional Hadamard transform is performed. The conversion order increases,
When the number of output spectrums of the Adal conversion increases as a result, the S / N improvement degree increases. If the input pixel method of the 2 × 8th order Hadamard transform is shown in FIG.
The output of the 8th-order Hadamard transform circuit 40 has an energy distribution centered on the spectral components shown in FIG. This spectrum is on the band of the color signal, and the input color difference signal can be decomposed into frequencies at substantially equal intervals. The video signal output from the 2 × 8th order Hadamard conversion circuit 40 becomes a 16-component conversion output having 16 kinds of frequency characteristics, and becomes an output signal having an energy distribution biased to a certain frequency on the frequency axis. On the other hand, since noise has no correlation on the frequency axis, 16 × of the output of the 2 × 8th order Hadamard transform circuit 40 is generated.
It is almost evenly distributed in the frequency distribution of the components. This 2
Since the noise level at the output of the × 8th order Hadamard conversion circuit 40 corresponds to the noise level of the input signal as is well known, the noise level at the output of the nonlinear processing circuit group 41 is 16
Only a small level noise component can be extracted from each component. Since each component extracted by the non-linear processing circuit group 41 is obtained by the 2 × 8th order Hadamard transform, it is returned to the original time axis by passing through the 2 × 8th order Hadamard inverse transform circuit 42. The signal obtained here is obtained by extracting only the noise component from the frame difference signal having no frame correlation.
The noise components are subtracted from the input color difference signals supplied to the B and 3Rs to obtain noise-free RY and BY digital color difference signals. And the A / D converter 2
The digital color difference signals are converted to original analog signals at 6 and 31 and output from the output terminals 27 and 32.

Finally, the component video signals (luminance signal, RY signal, B-) are output from the output terminals 11, 27 and 32.
Y signal) output is obtained.

Although the present embodiment uses the frame memory, the present embodiment can be implemented by using the field memory.

Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 7 is a block diagram of a noise reduction image pickup device using the noise reduction device according to the first embodiment of the present invention. In FIG. 7, 51 is a CCD of the image pickup device, 52 is a camera signal processing circuit, 53 is a luminance signal noise reduction circuit group, 54 is an RY signal noise reduction circuit group, 55 is a BY signal noise reduction circuit group, and 56. Is a luminance signal output terminal, 57 is an RY signal output terminal, and 58 is B
-Y signal output terminal.

The operation of the noise reduction image pickup apparatus of this embodiment having the above-mentioned structure will be described below. The input optical signal is converted from an optical signal into an electric signal by the CCD 51 of the solid-state image pickup device at the clock frequency fS of the image pickup device. The camera signal processing circuit 52 obtains a luminance signal, an RY signal, and a BY signal as an input signal as a component signal. Each component signal is input to each noise reduction circuit group 53, 54, 55 to reduce noise. The three noise reduction circuit groups are similar to the noise reduction circuits described in the first embodiment, and the same processing is performed. However, in this case, the sampling frequency of the luminance signal is the same as the clock frequency fs of the imaging device,
The sampling frequency of the color difference signal is about 1/4 of the sampling frequency of the luminance signal, which is 1 / 4fs. Component signal with reduced noise (luminance signal, RY signal,
The BY signal) is output from the output terminals 56, 57 and 58.

Although the present embodiment uses the frame memory, the present embodiment can be implemented by using the field memory.

[0039]

As described above, according to the present invention, the component video signals are sampled at the independent sampling frequencies, and the independent noise reduction circuits are provided, so that the band of the video signals and the brightness of the component signals having different characteristics can be obtained. Even for signals and color difference signals, noise can be efficiently reduced without degrading the input signal.

[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 internal configuration of a 2 × 4th order Hadamard transform circuit group 21 of FIG.

3 is a 2 × 8 order Hadamard transform circuit group 25B of FIG.
Block diagram showing the internal structure of 25R

FIG. 4 is a spectrum diagram showing the output of the 2 × 4th order Hadamard conversion circuit 7 of FIG.

5 is a 2 × 8 order Hadamard transform processing circuit group 25 of FIG.
Input pattern diagram showing input to B and 25R

FIG. 6 is a spectrum diagram showing the output of the 2 × 8th order Hadamard conversion circuit 40 of FIG.

FIG. 7 is a block diagram of a noise reduction image pickup device using a noise reduction device according to a second embodiment of the present invention.

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

9 is an input pattern diagram showing inputs to the 2 × 4th order Hadamard transform circuit 7 of FIG. 8;

[Explanation of symbols]

 1 Input Terminal 2,23,29 A / D Converter 3 Subtractor 4,24,30 Memory 5 Color Signal Phase Shift Circuit 6,6B, 6R Subtractor 7 Hadamard Transform Circuit 8 Nonlinear Circuit 9 Hadamard Inverse Transform Circuit 10,26 , 31 D / A converter 11 output terminal 21 2 × 4th order Hadamard conversion processing circuit group 22 BY signal input terminal 25B, 25R 2 × 8th order Hadamard conversion processing circuit group 27, 57 BY signal output terminal 28 R -Y signal input terminal 32,58 RY signal output terminal 40 2x8 order Hadamard conversion circuit 41 Non-linear circuit 42 2x8 order Hadamard inverse conversion circuit 51 CCD (solid-state image pickup device) 52 Camera signal processing circuit 53 Luminance signal noise Reduction circuit group 54 RY signal noise reduction circuit group 55 BY luminance signal noise reduction circuit group 56 luminance signal output terminal

Claims (9)

(57) [Claims] 1. A means for dividing a component video signal composed of a plurality of components into at least two sets, a quantizing means for quantizing each set at an independent frequency, and each of the component video signals . A noise reducing device via a noise eliminating means independent for each component , wherein the noise eliminating means receives each input video signal and n (n> 0).
First subtraction means for obtaining a difference component from the output signal of the field delay means, feature extraction means for decomposing the output signal of the first subtraction means into a plurality of feature components, and non-linear to at least one of the feature components Non-linear processing means for performing processing, second subtraction means for obtaining a difference signal between the output of the non-linear processing means and the input video signal, and the n-field delay means for delaying the output signal from the second subtraction means. The output of the n-field delay means or the output of the second subtraction means is used as an output signal, and the component video signal is output.
The signal consists of a luminance signal and two color difference signals.
The number of characteristic components extracted by the output means is determined by the color difference signal from the luminance signal.
A noise reduction device characterized by a larger number of issues . 2. The number of feature components extracted by the feature extraction means
But the noise reducing device according to claim 1, wherein the number of the luminance signal and wherein this <br/> and is 1/2 of the number of color difference signals. 3. The quantization frequency of the two color difference signals is the luminance signal.
The noise reduction device according to claim 1 or 2 , wherein the quantization frequency is 1/4 of the quantization frequency of the signal . 4. A component image composed of a plurality of components.
Means for separating the signal into at least two sets, and each set
Quantizing means for quantizing at an independent frequency for each
An independent miscellaneous component for each component of the component video signal.
A noise reducing device via a sound removing means, wherein the noise removing means is provided for each input video signal and n (n
> 0) Obtain the difference component from the output signal of the field delay means
First subtraction means, and an output signal of the first subtraction means is decomposed into a plurality of characteristic components
Feature extracting means and a non-liner for performing non-linear processing on at least one of the feature components
Shape processing means and a difference between the output of the non-linear processing means and the input video signal.
Second subtracting means for obtaining a signal, and the n-type delay means for delaying the output signal from the second subtracting means.
And a field delay means, the output or the second subtraction of the n-field delay means
The output of the means is used as an output signal, and the component video signal is transmitted.
Signal consists of a luminance signal and two color difference signals
The quantization frequency of the signal is 1/4 of the quantization frequency of the luminance signal
The noise reduction device according to claim 1. 5. The quantization frequency of the luminance signal is 4fsc (fsc
= 3.58 MHz), the quantization frequency of the two color difference signals
Is fsc, The noise reduction apparatus of Claim 4 characterized by the above-mentioned . 6. An input optical signal is transmitted at a clock frequency of fs.
Means for replacing the optical signal, and
Digit consisting of at least two components from the extracted electrical signal
Means for extracting a video signal of the digital component,
Component of video signal into at least two sets
Of the component video signals
Quantize one set with a quantization frequency of fs, and
Is a quantizer that quantizes each set with independent frequency
And for each component of the component video signal,
It is a noise reduction device through independent noise elimination means.
Then, the noise removing means receives the respective input video signals and n (n
> 0) Obtain the difference component from the output signal of the field delay means
First subtraction means, and an output signal of the first subtraction means is decomposed into a plurality of characteristic components
Characteristic extracting means, and a non-liner for performing non-linear processing on at least one of the characteristic components
Shape processing means, and a difference between the output of the non-linear processing means and the input video signal.
Second subtraction means for obtaining a signal, and the n-type delay means for delaying an output signal from the second subtraction means.
And a field delay means, the output or the second subtraction of the n-field delay means
The output of the means is used as an output signal, and the component video signal is transmitted.
No. become more the luminance signal and two color difference signals, before Symbol feature extraction
The number of characteristic components extracted by the output means is determined by the color difference signal from the luminance signal.
The noise reduction image pickup device is characterized in that there are more signals. 7. The number of feature components extracted by the feature extraction means
However, if the number of luminance signals is 1/2 of the number of color difference signals,
The noise reduction imaging device according to claim 6. 8. The quantization frequency of the two color difference signals is the luminance signal.
No. 1/4 of the quantization frequency of the No.
Item 6. The noise reduction image pickup device according to Item 6 or 7 . 9. An input optical signal is transmitted at a clock frequency of fs.
Means for replacing the optical signal, and
Digit consisting of at least two components from the extracted electrical signal
Means for extracting a video signal of the digital component,
Component of video signal into at least two sets
Of the component video signals
Quantize one set with a quantization frequency of fs, and
Is a quantizer that quantizes each set with independent frequency
And for each component of the component video signal,
It is a noise reduction device through independent noise elimination means.
Then, the noise removing means receives the respective input video signals and n (n
> 0) Obtain the difference component from the output signal of the field delay means
First subtraction means, and an output signal of the first subtraction means is decomposed into a plurality of characteristic components
Characteristic extracting means, and a non-liner for performing non-linear processing on at least one of the characteristic components
Shape processing means, and a difference between the output of the non-linear processing means and the input video signal.
Second subtraction means for obtaining a signal, and the n-type delay means for delaying an output signal from the second subtraction means.
And a field delay means, the output or the second subtraction of the n-field delay means
The output of the means is used as an output signal, and the component video signal is transmitted.
Signal consists of a luminance signal and two color difference signals
The quantization frequency of the signal is 1/4 of the quantization frequency of the luminance signal
A noise-reducing image pickup device characterized by: