JPS62290268A - Noise eliminator - Google Patents

Abstract

PURPOSE:To eliminate a noise component with high accuracy on a frequency axis, by generating an individual signal by every frequency band area, and correcting an input television signal. CONSTITUTION:A frame differential signal E is band-limited at a band-pass filter 81, and is sent to a multiplier 51. A part of it is sent to a noise detector 91, and an appropriate factor K1 is decided by a noise detected in the vertical retrace period of a band-limited signal E1, then it is outputted to the multiplier 51. An input television signal X suppresses the noise not only uniformly at the frequency band area, but suppresses the noise non-linearly, and dynamically corresponding to the frequency characteristics of the noise component mixed in the input television signal.

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 present invention relates to a noise removal device for controlling the weight ratio between the two signals using the frame difference between the two signals and suppressing noise by utilizing the autocorrelation between each frame.

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 deviation signal") A conventional device will be explained based on a relatively simple configuration example shown in FIG.

The current television signal X that has entered the input terminal l of the device is subtracted by the subtracter 4 from the output signal W from the delay circuit 7 consisting of a frame memory and a chroma inverter, that is, the signal from one frame before, and a frame difference signal is obtained. It becomes E. A part of the frame difference signal E is sent to a motion detector 6 to obtain an appropriate coefficient K depending on the absolute value of the frame difference signal E. Multiplication R
In step 5, the aforementioned frame difference signal E is multiplied by the coefficient,
Here, a correction signal KE for the current input television signal X is constructed. Further, this correction signal KE is added to the current input television signal X in an adder 3 to become an output signal Y of the noise canceling device. Further, a part of the output signal Y is sent to the aforementioned delay circuit 7.

Eventually, the output signal Y is expressed as Y=X+KE=(1-K)X+KW. Here, K is a variable coefficient, and when the absolute value of the frame difference signal E is large, the current input television signal so that 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 signal W and output.

Problems to be Solved by the Invention These conventional methods are extremely effective and widely used in dealing with white noise found in transmission systems. However, in such a method,
When considering the noise contained in the input television signal in the frequency domain, the coefficient K is uniformly controlled for all frequency components to remove the noise.
This is effective if the noise is white, but if it has noise components that are not uniform in the frequency domain, it may cause an afterimage.

Means for Solving the Problems The present invention was invented to solve the above problems, and its basic means is to divide the frame difference signal E into at least two or more frequency regions, and then divide the frame difference signal E into at least two frequency regions. Noise components are detected in each frequency domain, appropriate coefficients are associated with each frequency domain, and the noise contained in the input television signal is suppressed. 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 generate a correction signal individually for each frequency band and correct the input television signal, so that noise components are accurately removed from the input television signal on the frequency axis. It will be removed.

Embodiment FIG. 1 shows the configuration of an embodiment of a noise removal device according to the present invention. In the figure, 3, 4.6 and 7 represent the same circuits as 30, 40, 60 and 70 in FIG. 5, respectively.

Also 8f 82. -------, 8N is a band pass filter, which has mutually contradictory frequency characteristics and is configured such that the sum of their pass band widths includes the frequency components of the television signal. It is something that Further 9L 92. -.--1-, 9N is a noise detector, and 51.52, -m---, 5N is a multiplier.

The biggest difference from FIG. 5 is that the frame difference signal E is divided into a plurality of frequency bands using a bandpass filter and processed in each frequency band.

First, the frame difference signal E is band-limited by the bandpass filter 81 to become a signal E1, which is sent to the multiplier 51, but a part of it is sent to the noise detector 91.

The noise detector 91 determines an appropriate coefficient of 1 based on the noise detected during the vertical retrace period of the band-limited signal E1, and outputs it to the multiplier 51. In the multiplier 51, the signal E1 and the coefficient are multiplied by 1 signal. Similar processing is 8 i +9
i, 5i (1≦i≦N), and is executed for mutually different frequency bands. in the end,
From the adder 100, Ki (1≦i≦N) and Ei ('1≦
i≦N), that is, Z = 1・E1+ and 2・E2+−・・−+ KN −
EN −・−−−−−・・−(1) (However, 0≦Ki
<1 (1≦i≦N) El +22 +−−−−−−·+EN=E) is extracted and multiplied by the coefficient related to the motion determined by the motion detector 6 in the multiplier 200. .

Therefore, the output signal Y of the noise canceling device according to the present invention is Y=X+KZ ~, and the input television signal The noise is suppressed nonlinearly and dynamically according to the frequency characteristics of the noise components mixed in the signal.

Here, the noise detectors 91.92.・・・－・・・－・、
9N is a coefficient Ki(
1≦i≦N). FIG. 2 shows an example of the configuration of the noise detector 91. In the figure, 911 is a gate that extracts a signal in the vertical retrace period of the signal E1 obtained by bandpass filtering the frame difference signal E, and 912 is a gate that extracts a signal in the vertical retrace period of the signal E1 obtained by bandpass filtering the frame difference signal E. The coefficient controller is configured to output a value of 1 for the smaller value if it is smaller than the set darkness value, and output a value of 1 for the larger value if it is larger than the darkness value. 92°-..., 9N also has the same configuration as 91.

In the above embodiment, the magnitude of noise in the vertical retrace period of the input television signal is classified using one darkness value, and a binary signal is output using the coefficient control value.
To obtain better image quality, use multiple darkness values,
The configuration may be such that a multivalued control signal is created and a selection circuit selects the output of a read-only memory or coefficient multiplier provided corresponding to each value of the control signal.

Effects of the Invention As is clear from the principle of operation, the present invention is not effective when the noise of the television signal is white, as seen in the transmission system. However, it is effective when the frequency characteristics of the noise are not uniform, such as in a television signal recorded on a VTR or the like, and the noise can be suppressed according to the frequency characteristics of the noise.

The coefficient Ki (1≦
The situation in which i≦N) is determined is shown in FIG. Further, FIG. 4 shows the situation when a television signal mixed with noise whose frequency characteristics are not uniform is similarly input. However, in order to simplify the explanation, both Fig. 3 and Fig. 4 show the frequency band divisions limited to three cases; The result is obvious.

[Brief explanation of the drawing]

FIGS. 1 and 2 are block diagrams showing the configuration of a noise removal device in an embodiment of the present invention, and FIGS. 3 and 4 are
FIG. 5, a frequency characteristic diagram showing the operating characteristics of the above embodiment, is a block diagram showing the configuration of a conventional noise removal device. 1.10...Input terminal, 2,20...
Output terminal, 3゜30, 200...Adder, 4,
40...Subtractor, 5,505L 52. ---
-----, 5N... Multiplier, 6, 60...
...Motion detector, 7,70...Delay circuit, 8I
, 82. ---, 8N... Bandpass filter, 91, 92. ......-9N...Noise detector, 911...Gate, 912...
...Coefficient controller. Fig. 1 W: Preliminary signal frequency HX] Frequency [MH1'J Fig. 5 W: Preliminary I signal

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 control coefficients to convert the current input television signal and past television signals. A noise removal device that suppresses noise by adding weights, in which a frame difference signal between a current input television signal and a past television signal is input in parallel to at least two or more bandpass filters with different frequency bands. a device that individually controls the coefficients in a plurality of frequency bands; a device that detects noise components in the vertical blanking period of the frame difference signal; A device for individually determining a correction signal for a noise component for each frequency band, and a device for correcting an input television signal with the correction signal determined for each frequency band. noise canceling device.