KR960012535B1 - Image signal compensation method - Google Patents

Abstract

storing mean compensation coefficients of pixels for compensating irregularity of a light source when a scan roller(12) is ideally white; calculating the difference between the mean compensation coefficients of a contaminated scan roller and the mean compensation coefficients of a white scan roller; and compensating the coefficients of the contaminated scan roller by adding or subtracting the difference of the compensation coefficients to provide the good quality of image.

Description

How to calibrate fax signal

1 is a block diagram of a conventional fax signal correction device.

2 is a diagram illustrating the configuration of a light change method in processing a signal.

3 is a characteristic diagram of light intensity over time.

4 is a flowchart of a method of correcting a signal of a facsimile of the present invention.

* Explanation of symbols for main parts of the drawings

1: Sample / Hold Part 2: Calibration Digital / Analog Converter

3: automatic jog adjustment unit 4: switching unit

5: digital / analog converter for dish

6: comparator

The present invention relates to a facsimile signal correction method, and more particularly, to a facsimile image signal correction method for eliminating image quality problems caused when the scan roller used in image processing is contaminated.

The conventional facsimile signal compensator configuration is shown in Figure 1 is a sampling of the video signal output from the CCD (CCD) that emits light to the document and then converts the reflected light into an electrical signal And a sample / holding unit 1 for holding, and a digital / analog converter 2 for correcting the light intensity by converting the sample / holding unit 1 into an analog value according to the digital holding value input from the sample / holding unit 1; An automatic lightening adjuster 3 for automatically maintaining the original color density component according to the output of the correction digital / analog converter 2, and the automatic lightening adjuster 3 according to a control signal of a microcomputer (not shown). And a switching unit 4 for selecting one of the picture transmissions from the outside, and a digital / ah for dish which performs a disher process and outputs a picture when the picture is transmitted through the switching unit 4. Consists of a log converter 5, and the correction digital / analog converter (2) and di syeoyong digital / analog converter 5, a comparator 6 which outputs a black-and-white judgment is performed by the two values are compared with each other to be output from.

Looking at the conventional technical operation configured as described above are as follows.

As shown in FIG. 2, when the light source 11 scans the light from the light source 11 to the scan roller 12, the light reflected through the scan roller 12 is input to the CD 13 to process the signal. It is converted into an electrical signal used at the time.

If the electrical signal converted through the CD 13 is a video signal, the video signal is sampled by the sample / hold unit 1 and then held again and stored for a while. The stored signal is corrected as an analog signal according to a sampling value in the correction digital / analog converter 2 because the light source 11 of the CD 13 does not have constant light intensity. For example, if the output of the CD is used as a video signal without correcting the light intensity, staining occurs in the vertical direction of the reproduced original, and faithful reproduction of the original is impossible. This is called a shading phenomenon.

That is, when the intensity A ₁ -A ₁₇₂₈ of the light source as shown in FIG. 3 is constant, the light reflected from the scan roller 12 and input to the CD 13 is uniform as white (WHITE) level. something to do.

However, as mentioned above, since the intensity of the light source is non-uniform, the light reflected from the scan roller 12 and input to the CD 13 takes the form of a shading signal that does not reach a certain white level.

Therefore, in order to correct the shaded signal (Shad) to the white level, the correction coefficient for each 1728 pixels is obtained by the following equation.

White level = video signal x correction factor ... (1)

In other words,

Correction coefficient for each pixel = white level / picture signal ..... (2)

The correction coefficient for each pixel obtained here is corrected for each pixel during actual signal processing to make a uniform level.

In this way, when the corrected analog signal is input to the comparator 6 and fed back to the automatic light adjustment unit 3, the automatic light adjustment unit 3 compensates for the color blur caused by the difference in quality of the original document. It automatically maintains the color density of the paper. In general, if the paper is white, the color of the paper is maintained based on the light blue color.

When the automatic concentration adjustment unit 3 automatically adjusts the density of the transmission document and outputs it to the switching unit 4, the switching unit 4 selects and outputs any one of the picture transmissions input from the outside.

When the switching unit 4 selects the output of the automatic light adjusting unit 3, it is input to the comparator 6 through the digital / analog converter 5 for the disher, and transmits the picture transmission through the switching unit 4. In this case, the disher is subjected to a disher processing in the disher digital / analog converter 5 and then input to the comparator 6.

The comparator 6 compares two values input through the digital / analog converter 2 for correction and the digital / analog converter 5 for the disher, and performs black and white determination and performs a coding operation, which is the next procedure.

However, in the prior art, in order to solve the problem caused by the nonuniformity of the CD light source, the nonuniformity of the light source is corrected based on the white roller. When the white roller is contaminated black, the intensity of the reflected light is significantly reduced, which causes problems in the image. That is, the correction coefficient for compensating for the unevenness of the light source acts as a wrong factor, causing the image to be blurred overall.

Therefore, in order to solve the conventional problem, the present invention stores the average value of the ideal correction coefficient when using a white roller in a ROM, and then reduces the image quality by adding or subtracting the difference of the average value of the variable correction coefficient when the roller is contaminated. The present invention has been made with reference to the accompanying drawings, in which the facsimile signal correction method for preventing and providing a better image quality to the user is as follows.

The configuration of the present invention is the same as that of the prior art, and the correction digital / analog converter 2 stores 1728 pixel-specific correction coefficients of the shading signal due to the nonuniformity of the light source, so that the correction is performed when the scan roller is contaminated. If the average value of the coefficients is an ideal white roller, the difference should be compensated for the contamination of the roller by adding or subtracting this difference.

As mentioned above, when the scan roller is abnormally low white, obtaining the average value of the correction coefficient for each pixel to compensate for the nonuniformity of the light source, and storing the average in the ROM, and when the scan roller is contaminated, the average value of the correction coefficient and the white roller are Based on FIG. 4, the process of calculating the difference between the mean values of the correction coefficients and the step of obtaining the correct correction coefficients by subtracting the difference between the correction coefficients and the correction coefficients when the scan roller is contaminated in this step Looking at the operation and effects of the invention as follows.

When the average value of 3 is also scanned roller 12 is ideal for the white correction coefficient i.e. when the non-uniformity of the light source (11), A ₁ -A ₁₇₂₈ shown in K d

to be.

Here, the correction coefficients A ₁ -A ₁₇₂₈ are values obtained by dividing the white level by the sum signal as described in the related art.

The average value K of the correction coefficients obtained above is programmed into the ROM.

At this time, when the scan roller 12 is contaminated, the correction factor for the light source 11 has a larger value than that based on the white scan roller. If (Kx-K) = Ky is larger than the ideal K value, subtracting the Ky value from all the correction coefficients of the coefficients (A ₁ -A ₁₇₂₈ ) that compensates for the unevenness of the light source allows correct It is corrected.

Therefore, when the image processing always compensates for the difference between the ideal correction coefficient average value K stored in the ROM and the correction coefficient average value Ky depending on the contamination level of the roller, a good image can be obtained.

As described in detail above, the present invention solves the trouble of clearing a roller directly by an after-service agent by compensating the image when it is contaminated by compensating for the difference by the value of the difference. It has the effect of providing better image quality to users and reducing the load on service personnel.

Claims (1)

The first step of obtaining the average of the correction coefficient for each pixel to compensate for the non-uniformity of the light source when the scan roller 12 is the ideal white, and when the scan roller 12 is contaminated, when the scan roller 12 is contaminated And a third step of calculating a difference between the mean values of the correction coefficients and a third step of correcting the difference between the correction coefficients obtained in the second step by adding or subtracting the correction coefficient when the scan roller is contaminated. Call signal correction method.