JPH06197244A - Image noise correcting method - Google Patents

Abstract

PURPOSE:To suppress the noises approximate to the human sensibility to the video signal. CONSTITUTION:In regard of at least one of luminance, chroma saturation and hue of an image signal, the difference between the level of a relevant picture element and the level of each peripheral picture element is calculated by a luminance conversion circuit 1, a chroma saturation conversion circuit 2, a hue conversion circuit 3, the frame memories 4-6, and the difference detecting circuits 7-9. When the deciding circuits 10-12 decide that each calculated value is larger than the 1st reference value or smaller than the 2nd reference value, the level of the relevant picture element is corrected by a luminance correcting circuit 19, a chroma saturation correcting circuit 20, and a hue correcting circuit 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a correction method for correcting image noise suitable for human vision.

[0002]

2. Description of the Related Art As a conventional image noise correction method, for example, when an image signal reproduced from a medium in which image information is FM recorded is displayed on a television (TV) screen, a part of an image having a nonstandard frequency is displayed. It is determined to be noise, and that portion is the same X of the scanning line before or even before that.
Noise is corrected by replacing the signal at the (horizontal) coordinate portion or the signal at the same coordinate portion one screen (one frame) before.

[0003]

However, the above conventional image noise correction method includes a signal which is visually abnormal when displayed on the TV screen even though it is within the standard. That is, the conventional method is not adapted to human vision.

Therefore, an object of the present invention is to provide an image noise correction method that solves the above problems.

[0005]

In order to achieve the above object, the present invention relates to the level of a target pixel and the level of each pixel around the target pixel with respect to at least one of luminance, saturation and hue component in an image signal. And calculating each difference between the calculated value and the first reference value, or correcting the level of the target pixel when the calculated values are all smaller than the second reference value. To do.

[0006]

According to the present invention, noise is not discriminated from the frequency of the image signal, but the difference between the level of the target pixel and the level of each pixel around the target pixel is calculated to detect human sensitivity. Suppressing the level of the target pixel when close noises are detected and the calculated values are all larger than the first reference value, or when the calculated values are all smaller than the second reference value, Amplifying the level makes noise less noticeable on the display screen.

[0007]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a block diagram of a first embodiment of the present invention, and FIG. 2 is a diagram for explaining a target range of difference detection.
As shown in FIG. 1, a video signal containing a noise component is converted into a brightness signal by the brightness conversion circuit 1, converted into a saturation signal by the saturation conversion circuit 2, and converted into a hue signal by the hue conversion circuit 3. And stored in the frame memories 4, 5, and 6, respectively.

Reference numerals 7, 8 and 9 are difference detection circuits for respective signals of luminance, saturation and hue, and reference numerals 10, 11 and 12 are determination circuits. The difference detection circuit 7 performs the following difference detection for each pixel forming one frame image stored in the frame memory 4. That is, FIG.
As shown in, the level of the target pixel at a predetermined coordinate (i, j) of the frame image and the periphery of that pixel, that is,
The difference detection circuit 7 detects each difference from each level of a pixel group within a predetermined range of upper and lower two lines. Judgment circuit 10
Compares each difference value from the difference detection circuit 7 with the first and second reference values (first reference value> second reference value),
When each difference value is larger than the first reference value or the second reference value
When all are smaller than the reference value of, the target pixel is determined to be noise, and a determination signal for controlling a switch and a correction circuit described later is output. The above operation is the same in each of the circuits 8, 9, 11, and 12 regarding saturation and hue.

Reference numerals 13, 14 and 15 are luminance component, saturation component and hue component extraction circuits for extracting and outputting a luminance component, a saturation component and a hue component respectively from a video signal containing a noise component. Each output signal passes through each of the switches 16, 17 and 18 and the luminance, saturation and hue correction circuits 19, 20 and 21 or the delay circuits 22, 2 are output.
3 and 24 are selectively input. Each of these circuits 1
The output signals from 9 to 24 are input to the mixing circuit 25, where they are mixed and output as a video signal with noise corrected.

The switch 16 inputs the signal of the luminance component from the luminance component extraction circuit 13 to the luminance correction circuit 19 according to the determination signal from the determination circuit 10. The brightness correction circuit 19 suppresses the level of the input signal based on the judgment signal from the judgment circuit 10 at a predetermined ratio when each difference value is larger than the first reference value, and from the second reference value. When all are small, it is amplified and output at a predetermined ratio. by this,
With respect to the luminance component, the level of the video signal is corrected, and the pixel portion becomes visually inconspicuous on the display screen. The switch 16 inputs the signal of the luminance component without noise from the luminance component extraction circuit 13 to the delay circuit 22 when the determination signal is not input from the determination circuit 10. The delay circuit 22 is for delaying the input signal in accordance with the signal processing time delay in the brightness correction circuit 19. The above operation is based on the respective constitutions 14, 15, 20 in saturation and hue.
The same applies to 24, and the video signal in which noise is corrected is output from the mixing circuit 25.

FIG. 3 shows a second embodiment. The first embodiment is an example in which the respective noises of the luminance, saturation and hue components are corrected in parallel, but this embodiment corrects them in series. In terms of circuit configuration, the luminance, saturation and hue component extraction circuits 13, 14 and 15 from the first embodiment.
A combination of a switch for each of luminance, saturation, and hue, a correction circuit, and a delay circuit is connected in series to eliminate luminance and saturation from a video signal containing noise. , The noise in each component of the hue is corrected in series, and other configurations (1 to 12) for noise determination are the same as in the first embodiment.

With such a configuration as well, it is possible to detect the noises of the luminance, saturation and hue components in the video signal and correct the noises.

[0014]

As described above, according to the present invention, noise close to human sensitivity can be detected from an image signal and corrected to make it inconspicuous.

[Brief description of drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a target range of difference detection.

FIG. 3 is a block diagram of a second embodiment of the present invention.

[Explanation of symbols]

 1 Luminance conversion circuit 2 Saturation conversion circuit 3 Hue conversion circuit 4-6 Frame memory 7-9 Difference detection circuit 10-12 Judgment circuit 13 Luminance component extraction circuit 14 Saturation component extraction circuit 15 Hue component extraction circuit 19 Luminance correction circuit 20 Saturation correction circuit 21 Hue correction circuit 22-24 Delay circuit 25 Mixing circuit

Claims (1)

[Claims] 1. A difference between a level of a target pixel and a level of each pixel around the target pixel is calculated with respect to at least one of a luminance, a saturation and a hue component in an image signal,
An image noise correction method, wherein the level of the target pixel is corrected when the calculated values are all larger than a first reference value or when the calculated values are all smaller than a second reference value.