JPS60167574A - Picture noise eliminating device - Google Patents

Abstract

PURPOSE:To eliminate the picture noise while keeping a picture in high contrast by detecting the edge part of a picture to display the area near the edge in a high contrast with no averaging and performing the averaging at the area excepting the edge part to have a display in the form of smooth signals. CONSTITUTION:A separated luminance signal is supplied to an averaging circuit 4, and the original signal (x) is subtracted from the averaged signal (x') by a subtractor 5. This (x-x') shows a local variance factor of a picture, and the signal (x-x') is supplied to a deciding ROM6. Then the signal (x-x') is multiplied by the contents (k) of the ROM6 by a multiplier 7 and then added with the signal (x') by an adder 8. Thus the output (y) is equal to x'+k(x-x'), and y=x' is satisfied if the (k) is set at 0. Thus an averaged waveform is obtained. Then y=x is satisfied when the (k) is set at 1 to obtain a original sharp signal. Thus it is possible to control the averaging degree according to the local variance factor of a picture by changing the value of (k) in response to the ROM address.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an artist noise removal device that removes noise from an image signal read by, for example, a camera element, etc. so as to make the signal suitable for display.

[Technical background of the invention and its problems]

A camera with a relatively low 8/N ratio such as a CCD.

An image signal obtained by a highly-resolved spatial division color separation filter is greatly affected by noise and is very unsightly when displayed. Furthermore, since the color difference signal is generally small (particularly small in complementary color filters), the noise that gets into this color difference signal cannot be ignored, and furthermore, it appears as noise in the output painter's color, which is a particular problem.

Multi-filtering is generally known as a method for removing image noise, but none of them are very effective despite their complexity.Among them, averaging is the simplest and has a relatively large effect. Averaging suppresses image noise, but the image itself also becomes blurry, which has the disadvantage of making it impossible to display high-resolution information such as characters.

[Purpose of the invention]

This invention eliminates the above-mentioned drawbacks, maintains the clarity of the image, and removes noise. J! An object of the present invention is to provide a noise removal device.

[Summary of the invention]

Therefore, in the present invention, the edge portions on both edges are detected, and the vicinity of the edge is displayed sharply without averaging, and when it is not an edge portion, the signal is averaged and displayed as a smooth signal.

〔Effect of the invention〕

According to the present invention, it is possible to display a good single image with image noise removed.

[Embodiments of the invention]

FIG. 1 shows an embodiment of the present invention. The signals captured by the color CCD sensor 1 are chronologically divided into three colors, rows It, G.
, 1 ((7) A/D converter 2 and converted into a digital signal. This signal is then input to a luminance/color difference signal separation circuit 3 and separated.

The separated luminance signal is input to the averaging circuit 4. A subtracter 5 subtracts the original signal from this averaged signal. Figure 2 shows this situation. Original signal
Letting the averaged signal be X, xx represents the local fluctuation rate of both edges. This x-x signal is the judgment FLO
M6f is input. As shown in FIG. 3, the contents of this ROM include, for example, a 21 bit bit for dither coal cutting in the MSB, and other bits (31) used for parameters. Next, FIG. 4 shows the relationship between the contents of the ROM 6 and addresses. A multiplier 7 multiplies the signal x-x indicating this local fluctuation by k of the contents of the ROM 6, and an adder 8 adds it to the averaged signal X. Then, the output y is y=x
+k(x−x). If it is 90 here, then y x
X, and an averaged waveform is obtained. For example,
If it is set to 1, it becomes y x X, and a sharp signal of C can be obtained. Further, if the value is set to a value larger than k81, a sharper signal with edge emphasis can be obtained. Therefore, as shown in FIG. 4, by changing the value of k in accordance with the ROM address, the degree of averaging can be controlled in accordance with the local fluctuation rate of one image. At this time, the binary dither switching bits are also set to 8 (as shown in FIG. 41) in a wide range to the ROM address. In areas where the rate of variation is small, noise is small, and in areas where characters, etc. change rapidly, a sharp image can be obtained.The same process is performed for color difference signals.

However, the color difference signal may generally be averaged about 2 to 3 times as much as the luminance signal. These luminance/color difference signals are input to the color conversion table RAM 9. In this RAM 9, a signal corresponding to the amount of ink is converted and is later inputted to the 2-digit dither circuit 10.

The 211-digit dither circuit 10 performs binarization only when the local variation is extremely large according to the determination ROM 6, performs dithering otherwise, and sends the signal to the color printer 11 to obtain a color image including halftones.

[Other embodiments of the invention]

If there is a lot of noise in the signal indicating the local variation rate input to the determination ROM 6, it is better to reduce the noise by averaging as shown in FIG. 6 for stability. Further, in practice, the number of threads for averaging may be set to a power of 2, and in this case, the multiplier 7 may simply be a bit shifter.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of a color copying station according to an embodiment, FIG. 2 is a diagram showing signal waveforms in this color copying machine, and FIG. 3 is a diagram showing the contents of the determination ROM 6. Figure, 4th
This figure shows the relationship between the contents of the determination ROM 6 and addresses, FIG. 5 is a waveform diagram of the averaged signal, and FIG. 6 is a diagram showing the configuration of another embodiment ζ. 3... Luminance/color difference separation circuit, 4... Averaging circuit, 6
...Judgment ROM. Representative Patent Attorney Kensuke Chika (and 1 other person) Figure 4 ROM Addressee Figure 5 Figure 6

Claims (1)

[Scope of Claims] (Means for separating a luminance signal and a color difference signal component using an 11-picture image signal as an input signal; means for determining a local variation rate of the luminance signal; and a means for determining the local variation rate of the luminance signal; and and a means for averaging, and controlling the degree of the averaging according to the local variation rate. (21 When the local variation rate is larger than a predetermined value, the first ratio 2. The painter noise removal device according to claim 1, wherein the averaging is performed at a rate greater than the first rate when the local variation rate is smaller than a predetermined value. (31 The image noise removal device according to claim 1, which performs binarization processing on the image signal when the local variation rate is larger than a predetermined value. (41 The painter signal is a monochromatic signal. 2. The image noise removing device according to claim 1, wherein the degree of averaging is controlled in accordance with the local fluctuation rate for only the luminance signal.