KR100277735B1 - Scanner Shading Correction Factor Detection Method - Google Patents

Abstract

An object of the present invention is to provide a shading correction coefficient detection method of a scanner that can prevent distortion of the obtained image data by obtaining a stable shading correction coefficient even if the white roller is contaminated.

Accordingly, a feature of the present invention is a shading of a scanner that sets a white reference value by scanning a white roller, detecting a shading correction coefficient using the acquired scanning data, and performing a shading correction operation using the detected shading correction coefficient. A correction coefficient detection method comprising: rotating a white roller by a predetermined angle; Scanning the predetermined area of the white roller; Detecting a temporary shading correction coefficient for each pixel corresponding to the image data detected by the scanning operation; It is to repeat the rotation step to the detection step a predetermined number of times, and to detect the final shading correction coefficient for each pixel that meets the preset condition among the temporary shading correction coefficients for each pixel of the detected image data. .

Description

Scanner Shading Correction Factor Detection Method

The present invention relates to a method of detecting a shading correction coefficient of a scanner, and more particularly, to a scanner in which a white roller is scanned, a shading correction coefficient is detected, and a white reference value is detected, even when the white roller is contaminated. The present invention relates to a shading correction coefficient detection method of a scanner capable of detecting a coefficient.

In general, a scanner is a device in which the light emitted from the lamp is reflected by the data recording surface of the original, and the amount of reflected light is measured by the photoelectric conversion element and converted into an electrical signal to obtain information recorded on the original. Say.

In addition, the scanner is attached with a white roller at any position that the scanning head can scan to set a white reference value of the scanned image data. That is, as shown in FIG. 1, the scanner includes a lamp 101, a lens 103 that integrates the reflected light when the light emitted from the lamp 101 is reflected on the document or the white roller 102, and the lens ( The photoelectric conversion element 104 for converting the reflected light integrated by the 103 into an electrical signal, and the image data converted by converting the electrical signal output from the photoelectric conversion element into image data in pixel units It is composed of a converter 106 for providing a to the scanning control unit 105.

Therefore, the scanner emits light to the white roller 102, which is marked with pure white, and measures the amount of light reflected from the white roller 102 to detect the white reference value to adjust the distortion degree corresponding to the light amount to the white reference value. . In other words, the general scanning head scans the white roller 102 in which the white pattern is displayed due to the nonuniformity of the lamp 101 and the nonuniformity of the sensitivity per pixel of the photoelectric conversion element 104 within the read width section. Even in this case, the output of the photoelectric conversion element 104 is a non-uniform waveform ("A" portion), as shown in FIG.

Correcting to reset this to the correct white reference value ("B" part) is called shading correction. In normal image processing, the shading phenomenon is a phenomenon occurring in an imaging tube such as a videoconductor, a cathode ray tube, etc., and refers to a phenomenon in which the brightness varies depending on the screen portion of a television. This is caused by non-uniformity of the target or secondary redistribution from the target to the target, which improves the distorted image quality by mounting the adjusting electron lens. However, recently, the concept limited to such a display device has been applied to an image input device such as an image scanning device in an extended concept having the same meaning.

In other words, shading correction corrects the phenomenon that the edges of the screen are darkened or deformed due to the characteristics of the lens system when digitizing general documents, aerial photographs, etc. to generate digital image data for computers. The density conversion function is determined for each partition and the density is corrected so that the entire screen has a uniform brightness, and the shading data is obtained through shading correction through a dummy scanning process. Method and the like.

That is, the shading correction operation first scans the white roller 102 mounted on the device to calculate a shading correction coefficient for converting a waveform such as "A" of FIG. 2 into a flat white reference value such as "B". Then, by scanning the original and applying the shading correction coefficient to the scanned data to compensate, it is possible to obtain almost the same image information as the image recorded on the original.

By the way, according to such a conventional scanner, the following problems arise.

That is, when the white roller is contaminated, when the white reference value is detected using the contaminated white roller, an error may occur in the shading correction coefficient by an error corresponding to the degree of contamination. Therefore, when the image information of the original is obtained by applying the shading correction coefficient having an error, image quality deterioration or distortion occurs.

Accordingly, an object of the present invention is to solve such a problem, and an object of the present invention is to obtain a shading correction coefficient of a scanner capable of preventing distortion of the obtained image data by obtaining a stable shading correction coefficient even when the white roller is contaminated. In providing a method.

1 is a view showing the structure of a typical scanner,

2 is a voltage waveform diagram obtained by the photoelectric conversion element of the scanning head when the white roller is scanned,

3 is a schematic block diagram of an apparatus for detecting a shading correction coefficient of a scanner applied to the present invention;

4 is a flowchart illustrating a method of detecting a shading correction coefficient of a scanner according to the present invention;

FIG. 5 is a diagram illustrating a state in which shading correction coefficients for each pixel detected by a plurality of pseudo scanning operations are stored in a shading memory.

<Description of the code | symbol about the principal part of drawing>

301: scanning control unit 303: roller control unit

308: photoelectric conversion element 311: shading memory

312: shading correction control unit 313: shading correction unit

In order to achieve the above object, a feature of the present invention is to scan a white roller, detect a shading correction coefficient using the acquired scanning data, and perform a shading correction operation using the detected shading correction coefficient to obtain a white reference value. A shading correction coefficient detection method of a scanner, comprising: rotating a white roller by a predetermined angle; Scanning the predetermined area of the white roller; Detecting a temporary shading correction coefficient for each pixel corresponding to the image data detected by the scanning operation; It is to repeat the rotation step to the detection step a predetermined number of times, and to detect the final shading correction coefficient for each pixel that meets the preset condition among the temporary shading correction coefficients for each pixel of the detected image data. .

Here, the final shading correction coefficient for each pixel may be a peak value among the temporary shading correction coefficients for each pixel, or may be an average value among the temporary shading correction coefficients for each pixel.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. First, in adding reference numerals to the elements of each drawing, it should be noted that the same elements are denoted by the same reference numerals as much as possible even if they are displayed on different drawings. In addition, in the following description there are shown a number of specific details, such as components of the specific circuit, which are provided only to help a more general understanding of the present invention that the present invention may be practiced without these specific details. It is self-evident to those of ordinary knowledge in Esau. In describing the present invention, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

3 is a schematic block diagram of an apparatus for detecting a shading correction coefficient of a scanner applied to the present invention. In general, a scanner can be classified into a shuttle type and an array type, and the exemplary embodiment of the present invention will be limited to the shuttle type. However, it is apparent that the present invention is equally applicable to an array method in addition to the shuttle method.

Referring to FIG. 3, the scanning controller 301 generates a timing signal for performing a series of scanning operations according to a program stored in a ROM 302 and manages the overall system operation. In particular, the scanning control unit 301 rotates the white roller (not shown) by controlling the roller control unit 303 a predetermined number of times, and determines the temporary shading correction coefficients detected by the predetermined number of times through a predetermined calculation process. By calculating, the optimum shading correction coefficient is detected.

The ROM 302 stores a program and reference data having a certain flow so that the scanning controller 301 can control the scanning system in a predetermined order. The RAM 304 stores temporary data generated while the scanning control unit 301 controls the system.

The lamp 305 outputs light of a predetermined intensity to read the image information of the original with the amount of reflected light. The lamp driver 306 turns on and off the lamp 305 by receiving a control signal from the scanning controller 301 at an appropriate time to drive the lamp 305.

The optical module unit 307 reflects the light output from the lamp 305 to the document, and forms an optical path such that the reflected light is incident on the photoelectric conversion element 308. The step motor unit 309 receives the driving signal from the scanning control unit 301 and moves the optical module unit 307 along the sub-scanning direction of the original with a predetermined resolution.

The photoelectric conversion element 308 photoelectrically converts light incident through the optical module unit 307 into an electrical analog signal proportional to the amount of light. The analog / digital converter 310 converts an analog image signal into digital image data corresponding to a preset number of bits.

The shading memory 311 stores image data digitized by the analog / digital converter 310, and particularly, stores the shading correction coefficient detected for the shading correction operation. Here, the shading memory 311 stores the temporary shading correction coefficients detected by a predetermined number of times, and finally stores the optimal shading correction coefficients obtained by the calculation process of the scanning controller 301.

The shading correction controller 312 reads the shading correction coefficient stored in the shading memory 311 for each pixel unit, and applies the shading correction coefficient corresponding to each pixel to the image data stored in the shading memory 311 by the shading correction coefficient. The correction operation of each pixel unit is controlled to compensate.

The shading correction unit 313 corrects image data stored in the shading memory 311 by applying a shading correction coefficient to each pixel according to a control operation of the shading correction control unit 312 and outputs the correction.

That is, the photoelectric conversion element 308 converts the reflected light incident through the optical module unit 307 into an electrical signal proportional to the amount of light to obtain an analog image signal. At this time, each pixel in the photoelectric conversion element 308 is driven at a preset timing according to the sensor driving clock provided from the scanning control unit 301, and the photoelectric conversion element 308 according to the preset resolution has a constant number of analog images. Output the signal. The scanning control unit 301 controls the lamp 305 to be turned on and off and at the same time controls the amount of light reflected in proportion to the original density to be incident on the photoelectric conversion element 308 via the optical module 307. Accordingly, the incident reflected light is converted into an analog voltage signal which is proportional to the intensity of light according to the characteristics of the photoelectric conversion element 308 and output.

Thereafter, the analog-to-digital converter 310 converts the analog image signal converted by the photoelectric conversion element 308 into digital image data having a predetermined number of bits (for example, 8 bits). In this case, it is preferable to use 256 gray scales that represent a single pixel in 8 bits as in a normal case for gray scales of images binned in black and white, but the number of bits allocated to each application field can be added or subtracted. Do. When performing analog / digital conversion, the more bits allocated to a pixel, the more precise and detailed the pixels can be represented. On the other hand, a relatively large amount of resources must be allocated, and the amount of computation increases exponentially during signal processing. It is a well known fact that it is delayed.

The shading memory 311 scans the reference pattern recorded on the reference sheet at the time of dummy scanning and stores the pattern data digitized by the analog / digital converter 310 at the address of each pixel position. Here, dummy scanning refers to an operation in which the photoelectric conversion element 308 scans a white roller provided on the opposite surface.

Subsequently, the shading correction control unit 312 reads the pattern data for each pixel stored in the shading memory 311 for each address and divides the preset maximum brightness value in pixel units during pseudo scanning, thereby shading correction coefficient corresponding to each pixel position. Is calculated and the calculated shading correction coefficient for each pixel is provided to the shading memory 311. In addition, the shading correction controller 312 outputs the shading correction coefficient for each pixel stored in the shading memory 311 in correspondence with the scanning data output from the analog / digital converter 310 for each pixel position in the process of scanning the actual document. Do it. Here, the maximum brightness value M is determined as a value obtained by subtracting 1 from a power of 2 by a predetermined number of bits m, which can be expressed by Equation 1 below.

M = 2 ^m -1

For example, assuming that the analog / digital converter 310 converts an analog image signal input from the photoelectric conversion element 308 into 8 bit (m) of digital scanning data, the maximum brightness value for obtaining the shading correction coefficient ( M) becomes 255 by Equation 1 above.

Finally, the shading correction unit 313 determines the digital scanning data output from the analog / digital conversion unit 310 and the shading correction coefficient for each pixel output by the control of the shading correction control unit 312 at the time of scanning the document. By multiplying each pixel to perform shading correction, and outputting the corrected digital scanning data, the digital scanning data of which the output deviation of each pixel is corrected can be obtained.

Referring to Figure 4 with respect to the operation of the present invention configured as described above is as follows.

When the scanning operation command is received, the scanning control unit 301 first initializes the pseudo scanning frequency N (N = 1) (S101), the lamp 305 and the optical module unit 307, the photoelectric conversion element 308, and the like. Drive to switch the system to a state in which the scanning operation can be performed. The scanning control unit 301 scans the white roller installed at a predetermined position of the scanner (S102), detects a shading correction coefficient for the obtained reference data (S103), and shades the detected shading correction coefficient to the shading memory 311. In S104 (see Fig. 5).

Thereafter, the scanning control unit 301 adds 1 to the pseudo scanning frequency N (S105), and compares whether the counted total pseudo scanning frequency N is equal to a preset predetermined number of times (S106). Here, if it is determined that the total number of pseudo scanning numbers N currently counted is not equal to the preset predetermined number, the scanning controller 301 controls the roller controller 303 to rotate the white roller by a predetermined angle (S107). ), And repeats the steps from step 102 (S102) to step 106 (S106).

If it is determined in step 106 (S106) that the total number of pseudo scanning counts N currently counted is equal to the preset predetermined number of times, the scanning controller 301 pixels each temporary shading correction coefficients detected by the pseudo scanning process to date. After dividing into units, detecting the peak value among the shading correction coefficients of each divided pixel unit (S108), setting the peak value of the detected shading correction coefficient for each pixel as the final shading correction coefficient, and then setting the final shading correction coefficient. Is stored in the shading memory 311 (S109).

That is, by detecting a peak value of each shading correction coefficient detected through a pseudo scanning process a predetermined number of times, the white component closest to the white reference value can be detected through the white roller. However, the final shading correction coefficient detection method may be applied to the average value of the shading correction coefficients for each pixel instead of the method for detecting the peak value among the shading correction coefficients for each pixel.

Therefore, even if the white roller is contaminated, an accurate shading correction coefficient can be detected, thereby preventing distortion of the scanned image data.

As described above, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined by the claims below and equivalents thereof.

As a result, according to the method of detecting the shading correction coefficient of the scanner according to the present invention, the following advantages occur.

That is, the white roller is rotated by a predetermined angle to perform a plurality of pseudo-scanning operations, detects only peak values among the obtained plurality of shading correction coefficients, sets this as the final shading correction coefficient, and uses the set final shading correction coefficient. By performing the shading correction operation, an accurate shading correction coefficient can be detected even if the white roller is contaminated. Accordingly, distortion of the scanned image data can be prevented.

Claims (3)

A method of detecting a shading correction coefficient of a scanner for setting a white reference value by scanning a white roller, detecting a shading correction coefficient using the acquired scanning data, and performing a shading correction operation using the detected shading correction coefficient: Rotating the white roller by a predetermined angle; Performing a scanning operation on a predetermined area of the white roller; Detecting a temporary shading correction coefficient for each pixel corresponding to the image data detected by the scanning operation; And Repeating the rotation step to the detection step a predetermined number of times and detecting a final shading correction coefficient for each pixel that meets a predetermined condition among the temporary shading correction coefficients for each pixel of the detected image data; Shading correction coefficient detection method of a scanner comprising a. The method of claim 1, wherein the final shading correction coefficient for each pixel is The shading correction coefficient detection method of the scanner, characterized in that the peak value of the temporary shading correction coefficients for each pixel. The method of claim 1, wherein the final shading correction coefficient for each pixel is The shading correction coefficient detection method of the scanner, characterized in that the average value of the temporary shading correction coefficients for each pixel.