JPS62290270A - Noise eliminator - Google Patents

Abstract

PURPOSE:To show the same effect on a still image as that of a conventional device, and to eliminate the noise of an image having motion most appropriately, by generating a correction signal by performing the detection of an individual moving part, and the noise, at every frequency band area. CONSTITUTION:A frame differential signal E is band-limited at a band-pass filter 101, then being sent to a multiplier 501. A part of it is sent to a noise detector 201, and a motion detector 301. At the noise detector 201, the noise is detected in a vertical retrace period, and a factor KN1 is outputted. At the motion detector 301, a factor KM1 is outputted corresponding to the size of an absolute value. At the multipliers 501 and 601, a signal Z1 is outputted by multiplying a signal E1 by the factors KN1 and KM1. All of the correction signals generated at every frequency band area are added at adders 32, 33,-3N, then a correction signal Z for an input television signal is generated.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention Industrial Application Field The present invention provides a signal obtained by scanning an image such as a television signal, in which a current input signal and an output signal of one frame in the past are used. The weight addition ratio between the two signals is controlled by the frame difference between the two signals, and the autocorrelation between each frame is utilized.
The present invention relates to a noise removal device for removing noise.

Conventional technology When generating, transmitting, demodulating, and recording television signals,
Removing noise from image signals is extremely important and many efforts have been made to improve it.

(For example, Japanese Unexamined Patent Publication No. 56-35580 "Noise Suppression Device for Television Signal") A conventional device will be explained based on a relatively simple configuration example shown in FIG. The current television signal X input from the input terminal 10 of the device is subtracted by the subtracter 40 from the output signal W that has passed through the frame memory 50 and the chrominer inverter 60, resulting in a frame difference signal E. Here, the frame memory 50 is for delaying the television signal by one frame, and the chroma inverter 60 is for matching the phase of the color signal of the current NTSC video signal, which differs in phase by 180 degrees from frame to frame, between frames. It is for the purpose of

Therefore, the output signal W from the chroma inverter 60 has the same phase as the current input television signal, and is the television signal of one frame in the past. A portion of the frame difference signal E is then sent to a motion detector 80 to obtain an appropriate coefficient K depending on the absolute value of the frame difference signal E. Multiplier 9
0, the frame difference signal E is multiplied by a coefficient, and a correction signal KE for the current input television signal X is created. Further, this correction signal KE is added to the current input television signal X in an adder 30,
It is output from the output terminal 20 as the output signal Y of the noise removal device. Further, a part of the output signal Y is sent to the frame memory 50 mentioned above.

In the end, the output signal Y is Y=X+KE= (1-K)X+KW −−−−−−
−・(1) (However, 0<K<1). Here, K is a variable coefficient, and when the absolute value of the frame difference signal E is large, the current input television signal X is considered to correspond to a moving part, and K=O
, so that the input television signal X is output as is. Conversely, when the absolute value of the frame difference signal E is small, it is assumed that it corresponds to a stationary part, and K is set to take an appropriate value of 0<K<1 according to the absolute value of the frame difference signal E. Then, the input television signal X is weighted and added to the past output signal W by one frame, and then output.

Problems to be Solved by the Invention These conventional methods are extremely effective and generally widely used for television signals mixed with white noise found in transmission systems. However, such a method has problems, such as when noise with biased frequency characteristics is mixed in, or when a portion of a moving image has a low correlation between frames, an afterimage occurs.

Means for Solving the Problems The present invention was devised to solve the above problems, and its basic means is to divide the frame difference signal E into at least two or more frequency bands, and then divide the frame difference signal E into at least two frequency bands. For each frequency band, the parts with low correlation between frames, i.e.
A signal that detects a moving image and a noise component included in a frame, uses these detection information to determine coefficients related to the components of the moving image and coefficients related to the noise component, and corrects the input television signal. is controlled individually for each frequency band. A signal detected during the vertical retrace period of the frame difference signal is used to detect the noise component.

Effect The present invention uses the method described above to individually detect moving parts and noise for each frequency band to create a correction signal and remove noise from an input television signal. , if parts with low correlation between frames or noise with biased frequency characteristics are mixed in, this will cause afterimages, but with the method of the present invention,
Depending on the frequency characteristics of noise detected during the vertical retrace period and the frequency characteristics of the frame difference signal, noise can be optimally removed and afterimages can be reduced. In addition, the present invention has the same effect as the conventional method for parts with high correlation between frames, that is, still images and white noise.

Embodiment FIG. 1 shows the configuration of an embodiment of a noise removal device according to the present invention. In the figure, 3 is an adder, 4 is a subtracter, 5 is a frame memory, and 6 is a chroma inverter. Also, 1
01, 102. , ---------, 1ON are band pass filters, each having a different pass band, and
It is configured such that the sum of these bandwidths includes the frequency components of the television signal. Furthermore, 20
1.202.・---1111., 2ON is a noise detector and 301.302. --------, 3ON is a motion detector. Also, 501.502.・－・－・、
5ON, 601,602.・---, 6ON is a multiplier, 32.33. -.--, 3N is an adder.

The biggest difference from the case in FIG. 7 is that the frame difference signal E is
A band-pass filter is used to divide the signal into multiple frequency bands and each frequency band is processed individually, and the noise component is detected and the correction signal is controlled according to the frequency characteristics of the noise. It is a point.

First, the frame difference signal E is band-limited by the bandpass filter 101 to become the signal El. This signal E1 is sent to the multiplier 501, but a part of it is sent to the noise detector 20.
1 and is sent to the motion detector 301. The noise detector 201 detects noise in the vertical retrace period of the band-limited frame difference signal El, and calculates a coefficient KN according to the magnitude of its absolute value.
Outputs I. The motion detector 301 outputs a coefficient KMI depending on the magnitude of the absolute value of the band-limited frame difference signal. Multipliers 501 and 601 multiply the signal El by the coefficients KNI and KMI to obtain a signal Z1.
Output. Here, the signal z1 is passed through the bandpass filter 1
01 is a correction signal for the input television signal within the passband. Therefore, the signal z1 is Zl=KMI・KNI・El −・−
・−・・−・−・−・(2). 10 similar processes
i, 20i, 30i, 50i and 60i (1≦
1faN), correction signals for input television signals are created in mutually different frequency bands. The correction signals created for each frequency band are sent to adders 32, 33 .・－・－・.

3N are added together to form a correction signal Z for the input television signal. Therefore, the correction signal Z is as follows: Z=KM1・KNI・E1+ and gate 2・KN2・E2+・
・・10 points N・KNN −EN・−・−−～(3) Further, this correction signal Z is added to the input television signal X in an adder 3, and the output signal Y
becomes. As a result, the output signal Y of the noise canceling device according to the present invention
is, y=x+z −−−−−−・−−−−−・(4).

However, Xi and Wi are frequency components limited by the bandpass filter 10i (1; 5i : 5N) for the input television signal X and the television signal W one frame past, respectively. , where the coefficients KMi (1≦15N) and KN of equation (4)
Both i (1:5i≦N) are variable coefficients, and KMi (1≦
i≦N) relates to the motion component in the input television signal, and KNi (1≦i≦N)
It concerns the noise component in the input television signal. coefficient KMi (1≦15N), when the band-limited frame difference signal is large, that is, in a frequency band where the change in the input television signal is large, it is assumed that it corresponds to a moving part of the image; =O, so that the input television signal in this band is output as is. Conversely, when the band-limited frame difference signal is small, that is, in a frequency band where the change in the input television signal is small, it is assumed that it corresponds to a stationary part of the image, and the value of 0<KMi<1 is set. The input television signal is appropriately corrected within this band by taking the following values. Further, KNi is determined with reference to a signal observed during the vertical retrace period of the frame difference signal which is band-limited. When no signal is recognized during the vertical retrace period of the band-limited frame difference signal, it is assumed that there is no noise, KNi=O, and the input television signal in this band is output as is. Figure 2 shows a noise detector 201.
An example of the configuration is shown below. In the figure, 901 is a gate for extracting a signal in the vertical blanking period of the frame difference signal which has been band-limited, and 902 is a gate that is set in advance according to the magnitude of the absolute value of the output signal from 901. The coefficient limiter is configured to output a small KNI value if it is smaller than the dark value, and output a larger KNI value if it is larger than the dark value. Further, 903 is an input terminal of the noise detector, 904 is a terminal for inputting a control signal for extracting only the vertical blanking period of the frame difference signal, and 905 is an output terminal of the noise detector. 202, 203. ---
-, 2ON also has the same configuration as 201.

When a television signal mixed with noise having biased frequency characteristics is input to the noise removal device according to the present invention,
The situation in which the coefficient KNi (1≦i≦N) is determined is expressed in the third
As shown in the figure. Further, FIG. 4 shows a situation in which the coefficient KMi (1:5i≦N) is determined when a television signal whose frame difference signal has typical frequency characteristics is input to the noise removal device according to the present invention. . Note that both FIGS. 3 and 4 show only three frequency band divisions to simplify the explanation; however, it is possible to obtain better image quality by increasing the number of frequency band divisions. It's self-evident.

For comparison, FIGS. 5 and 6 respectively show how the coefficients are determined when a similar signal is input to a noise removal device using a conventional method. The comparison target for FIG. 3 is FIG. 5, and the comparison target for FIG. 4 is FIG. 6.

In the above embodiment, the magnitude of the band-limited frame difference signal and the signal magnitude of the band-limited frame difference signal in the vertical blanking period are classified by one dark value, and KMi (1
≦15N) and i(1≦i≦N) both output binary signals, but in order to obtain better image quality, multi-value control is performed using multiple dark values. create a signal,
There is a configuration in which a selection circuit selects the output of a read-only memory or a coefficient multiplier provided corresponding to each value of a control signal.

Effects of the Invention As is clear from the operating principle, the present invention has the same effect as the conventional method for television signals mixed with white noise and parts with high correlation between frames, that is, still images. If the noise mixed into the input television signal has biased frequency characteristics, the noise can be optimally removed according to the characteristics, even for moving images.
This method optimally removes noise.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of the noise removal device according to the present invention, FIG. 2 is a block diagram showing the configuration of the noise detector in FIG. 1, and FIGS. 3 and 4 are The operational characteristic diagrams of the noise removing device based on the above embodiment, FIGS. 5 and 6, are the operational characteristic diagrams of the conventional noise removing device, and FIG.
The figure is a block diagram showing the configuration of a conventional noise removal device. 1.10... Input terminal, 2.20...
Output terminal, 3°30, 32.33. --1-・-13N
...Adder, 4, 40...Subtractor, 5
, 50... Frame memory, 6.60...
...Chroma inverter, 101, 102. --------
-, ION...Band pass filter, 201, 2
02. --------, 2ON... Noise detector, 70, 301, 302.・------, 3ON・・
...Motion detector, 90,501°502, ...-
,5ON,601,602.・------, 6ON・
... Multiplier, 901 ... Gate, 902
...Coefficient controller. Name of agent Patent attorney Toshio Nakao (1 person) Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] Components related to image motion are detected from the current input television signal and past television signals, and this detected information is used to appropriately control the coefficients. A noise removal device that removes noise by adding weights to signals, which applies a frame difference signal between a current input television signal and a past television signal to at least two or more band-pass filters having different frequency bands in parallel. a device that detects the component of the signal to be recognized as a moving image in each frequency band individually and determines the coefficient K for each frequency band; What is claimed is: 1. A noise removal device comprising a device that performs detection using a signal detected during a vertical retrace period of a frame difference signal and generates a correction signal for an input television signal.