JPS62290269A - Noise eliminator - Google Patents

Abstract

PURPOSE:To eliminate noise even at the part of a moving image, by detecting the part of the moving image between frames, after dividing into two or more frequency band areas, and generating an individual correction signal by every frequency band area, using a bit of detected information. CONSTITUTION:A frame differential signal E is band-limited at a band-pass filter 71, then being changed to a signal E1. The signal E1 is sent to a multiplier 91, and a motion detector 81. At the motion detector 81, an appropriate factor K1 is decided corresponding to the size of the band limited frame differential signal E1, and it is sent to the multiplier 91. In this way, the correction signals to an input television signal are generated at frequency band areas different with each other. Not only the noise is eliminated from a high correlative part between the frames, in other words, a still image in an input television signal X, but the noise is eliminated from a frequency component having a low rate of change out of signals changed between the frames, similarly as a case in the still image.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention Industrial Field of Application The present invention is directed to a signal obtained by scanning an image such as a television signal, in which the current input television signal and one frame in the past are separated from each other by one frame. The weight addition ratio with the television signal is
The present invention relates to a noise removal device that performs control based on the frame difference between the two signals and uses autocorrelation between each frame to remove 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, JP-A-56-35580 ``Television Signal Noise Suppression Apparatus'') A conventional apparatus will be explained based on a relatively simple configuration example shown in FIG. The current television signal X that has entered the input terminal IO 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 adjusting the phase of the color signal of the current NTSC video signal, which differs by 180 degrees from frame to frame, between frames. It's meant to make you lose.

Therefore, the output signal W from the chroma inverter 60 has the same phase as the current input television signal and is a television signal from the past by one frame.

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. The multiplier 90 multiplies the frame difference signal E by a coefficient, thereby creating a correction signal KE for the current input television signal X. Furthermore, this correction signal KE is added to the current input television signal X in an adder 30.
and is outputted 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 as follows: Y=X0KE= (1-K)X+KW −・・−・−
(11 (however, 0<K<1) where K is a variable coefficient, and when the absolute value of the frame difference signal E is large, the current input television signal X corresponds to a moving part. 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 O<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 television signal W by one frame and output.

Problems to be Solved by the Invention These conventional methods are very effective and generally widely used in areas where the correlation between frames is high in the input television signal, that is, in still image parts. be. However, in such a method, in areas where the correlation between frames is low, that is, in moving image areas, the input television signal is output as is, and noise is not removed at all.

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, different parts of the input television signal between frames, that is, parts of the moving image, are detected, and using this detection information, appropriate coefficients are associated with each of them, and the The correction signal is controlled individually for each frequency band.

Effect The present invention uses the method described above to generate a correction signal individually for each frequency band to remove noise from an input television signal. In particular, in the conventional method, noise is completely removed in parts of low correlation between frames. On the other hand, in the method according to the present invention, even in parts with low correlation between frames, by frequency-dividing the frame difference signal, the frames are divided into a frequency band with high correlation and a frequency band with low correlation between frames. Similar to still images, noise can be removed from frequency bands with high correlation. Further, for a portion where all frequency components between frames have a high correlation, that is, a still image, the frequency-divided frame difference signal becomes close to zero, and the effect is equivalent to that of the conventional method.

FIG. 2 shows the situation in which the coefficient Ki (1≦i≦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. show. In addition, in the same figure, for the sake of simplification of explanation,
Although the number of frequency band divisions is limited to three in the illustration, it is obvious that a better television signal can be obtained by increasing the number of divisions.

Here, the coefficient Ki (1≦i≦N) is similar to the above coefficient,
When the frame difference signal, which is a variable coefficient and is band-limited, is large, that is, in a frequency band where the change in the input TV deviation signal is large, it is regarded as a frequency component corresponding to a moving part of the image, and with Ki = 0, this band Now output the input television signal as is. On the other hand, when the band-limited frame difference signal is small, it is regarded as a frequency component corresponding to a stationary part, and it is set to an appropriate value of 0<Ki<1. Correct to.

Embodiment FIG. 1 shows the configuration of an embodiment of a noise removal device according to the present invention. In the figure, 4 represents the aforementioned subtracter, 5 represents the aforementioned frame memory, and 6 represents the aforementioned chroma inverter.

Also,? 1.72. ---, 7N is a band-pass filter that has different passbands and is configured such that the sum of these passband widths includes the frequency components of the television signal. be. Furthermore, 81
．． 82. -------, 8N is a motion detector,
91.92. --------・-, 9N is a multiplier, 31, 3
2. −・−・・・・3N is an adder. The biggest difference from Figure 3 is that the frame difference signal E is divided into multiple frequency bands using a bandpass filter, and a correction signal for the input television signal is created in each frequency band. .

First, the frame difference signal E is band-limited by the bandpass filter 71 to become the signal El. This signal E1 is sent to multiplier 91 and motion detector 81.

In the motion detector 81, the band-limited frame difference signal E
A multiplier 91 determines an appropriate coefficient of 1 depending on the magnitude of 1.
send to The multiplier 91 multiplies the signal E1 and the coefficient by 1. Similar processing is performed on 7i, 8i and 91 (1:
5i≦N), correction signals for input television signals are created in mutually different frequency bands. , adder 302.303°・−・−−−
-, 3ON are for adding the correction signal, and from the adder 302, Z= 1・E1+ 2・E2+−−−−−−・−+KN
−EN ・−・・・・−(2) (However, 0≦Ki<1
(1≦i!N)El + E2 +−−−−−−
・The signal 10N=E) is taken out and added to the input television signal in the adder 3. In the end, the output signal Y of the noise removal device becomes y=x+z, and the input television signal , parts with low correlation between frames,
That is, even for moving images, noise is removed from frequency components with a low rate of change among signals that change between frames, as in the case of still images.

Effects of the Invention As is clear from the operating principle, the present invention is effective not only for parts with high correlation between frames, that is, still images, but also for parts with low correlation between frames, that is, moving images. , noise can be removed from portions of the frame difference signal where the frequency components are small in the same way as for still images. When considered in the frequency domain, a frame difference signal in a television signal should originally have some frequency characteristics. The present invention can appropriately remove noise according to the frequency characteristics of this frame difference signal.

In the above embodiment, motion detection of the input television signal is classified using one darkness value, and the motion detector outputs a binary signal. However, in order to obtain better image quality, A multivalued control signal is created using a plurality of dark values, and a selection circuit is configured to select the output of a read-only memory or coefficient multiplier provided corresponding to each value of the control signal. There is a way.

[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 frequency characteristic diagram showing the operating characteristics of the above embodiment, and Fig. 3 shows the configuration of a conventional noise removal device. FIG. 1.10... Input terminal, 2.20...
Output terminal, 3°30, 302.303. ------1・
, 3ON...adder, 4,40...'
Il calculator, 5.50...Frame memory, 6,
60...Chromine inverter? 1.72. ---
-1-.-, 7N...Band pass filter, 80
．． 81.82. ...-, 8N...Motion detector, 90.91.92. -----..., 9N...
...multiplier. Name of agent: Patent attorney Toshio Nakao (1 person) Figure 1 Figure 2 Figure 3

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 for inputting a television signal to the input television signal, performing the integration of components regarding the motion of the image separately in a plurality of frequency bands, and generating a correction signal for the input television signal in each frequency band. A noise removal device characterized by: