KR100277732B1 - Shading Correction Method of Shuttle Scanner - Google Patents

Abstract

If a scanning job is selected, transfer the original to the scanning area; Scanning an original reaching the scanning area; Detecting the transfer position of the document; Detecting a shading correction coefficient in a predetermined pixel unit corresponding to the detected position of the document; Shading correction is performed by applying the detected shading correction coefficient in units of pixels to the pixels of the scanned data one-to-one.

Thus, more accurate shading correction results can be obtained.

Description

Shading Correction Method of Shuttle Scanner

The present invention relates to a shading correction method of a shuttle type scanner, and more particularly, to set various shading modes according to the state of a document to be conveyed, and to correspond to the current transport position of the document. The present invention relates to a shading correction method of a shuttle scanner that removes a shading correction error by applying a shading mode to perform a shading correction operation.

In a multifunction machine with a shuttle scanner or a built-in shuttle scanner, a scanner is a device that detects data recorded on an original in units of read width (1 band) and converts it into an electrical signal. That is, as shown in Figs. 1 and 2, the shuttle scanner is provided with a scanner head installed at a distance from the effective reading area of the original 1 by a predetermined distance and scanning image information recorded on the original 1 ( 2), a guide rail 3 for guiding the left and right reciprocating motion of the scanning head 2, and a carriage return motor providing a driving force for the reciprocating motion of the scanning head 2 from side to side. Motor 4, the carriage belt 5, which is simultaneously mounted to the carriage return motor 4 and the scanning head 2, and transfers the driving force of the carriage return motor 4 to the scanning head 2, and the cassette 6 Pickup roller 7 for picking up the original 1 loaded on the sheet) and feeding it onto the document feed path, and a driving roller for transferring the original picked up by the pickup roller 7 to the effective reading area of the scanning head 2. (8), the discharge roller 9 for discharging the original 1 after the scanning operation is finished, and the scanning head 2 Is included in the same trace attached to the outside of the valid reading area of the scanning head (2) points and is composed of the scanning head (2) is read based on the seat 10 of a type of a reference pattern is to be recorded.

And, the detailed structure of the scanning head 2, the lamp 11 is provided at its end so that the light emitted from the lamp 11 is irradiated to the document (1). Also, inside the scanning head 2, a photoelectric conversion element (using a "charge coupled device (CCD)") 12 for detecting light reflected from the document 1 and converting it into electrical data is provided. A lens 13 is mounted between the lamp 11 and the photoelectric conversion element 12 to focus the reflected light so that the light reflected from the document 1 reaches a predetermined region of the photoelectric conversion element 12. Here, the lamp 11, the photoelectric conversion element 12 and the lens 13 has an integrated structure.

Meanwhile, as shown in FIG. 3, the shuttle scanner has a scanning width that can be scanned at a time. The mono type can scan horizontally 1 [Pixel] × vertical 128 [Pixel]. The color type is configured to scan horizontal 1 [Pixel] x vertical 160 [Pixel]. That is, by one scanning operation, the scanning head 2 continuously scans from the first pixel to the last pixel by 1 [Pixel] x 128 [Pixel] (in the case of monochromatic type).

A process of scanning a document by a general shuttle scanner having such a configuration will be described below with reference to FIGS. 4 to 5.

The general scanning head 2 scans the reference sheet 10 on which a white pattern is printed due to the nonuniformity of the lamp 11 and the nonuniformity of sensitivity for each pixel of the photoelectric conversion element 12 within the read width section. In either case, the output of the scanning head 2 is a non-uniform waveform ("A" portion), as shown in FIG.

Correcting to set 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 image pickup tube such as a videoconductor or a CRT, 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 providing the adjusting electron lens. However, recently, the concept limited to the 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 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, and divides the screen into several small areas. Determining a density conversion function for each divided region to correct the density so that the entire screen has the same brightness, and obtaining shading data during dummy scanning and performing shading correction through the same There is this.

That is, the shading correction operation first scans the reference sheet 10 attached to the device to calculate a shading correction coefficient for converting a waveform such as "A" of FIG. 4 into a flat white reference value such as "B". Thereafter, by scanning the original 1 and applying the shading correction coefficient to the scanned data, image information almost identical to the image recorded on the original 1 can be obtained.

On the other hand, when the scanning operation command is received, the originals 1 loaded on the cassette 6 are sequentially picked up one by one by the pickup roller 7 and supplied to the drive roller 8 side. The driving roller 8 transfers the document 1 conveyed by the pickup roller 7 to the readable area of the scanning head 2. Accordingly, the transferred original 1 is located in the readable area of the scanning head 2, in which case the scanning head 2 scans the image recorded in the original 1 in band units. ) Is detected. Then, when the scanning operation for one band is finished, the document 1 is discharged to the outside by the drive roller 8 and the discharge roller (9).

Here, when the light emitted from the lamp 11 of the scanning head 2 is focused on the photoelectric conversion element 12 by the lens 13 after being reflected by the surface of the original 1, by the lens 13 The separation distance between the scanning head 2 and the document 1 is preset to a constant value so that the light can be accurately focused.

However, according to the conventional shuttle scanner, the following problems occur.

First, when the actual original 1 is transported, when the leading end of the original 1 is located in the readable area of the scanning head 2, the separation distance between the original 1 and the scanning head 2 is shown. As can be seen, the discharge roller 9 side is far away and the driving roller 8 side is close (see Fig. 5A).

In the case where the intermediate portion of the document 1 is located in the readable area of the scanning head 2, the separation distance between the document 1 and the scanning head 2 can be seen from the discharge roller 9 side and the driving roller. The side (8) is in the same state (see FIG. 5B).

Finally, in the case where the rear end of the document 1 is located in the readable area of the scanning head 2, the separation distance between the document 1 and the scanning head 2 is close to the discharge roller 9 side. The driving roller 8 side is far away (see Fig. 5C).

This indicates that the separation distance between the scanning head 2 and the document 1 sequentially changes during the process of continuously conveying the document 1 to the readable area of the scanning head 2, and thus the lamp 11 ), And the distance from the document 1 to the photoelectric conversion element 12 through the lens 11 is changed. Therefore, the intensity of light reaching the photoelectric conversion element 12 is changed.

However, although the intensity of light reaching the photoelectric conversion element 12 changes according to the change of the separation distance between the scanning head 2 and the original 1 generated during the transfer of the original 1, the original 1 As the same shading correction factor is applied throughout the transfer process of), an error occurs in the shading correction operation. Therefore, the reliability of the scanned result is deteriorated, and a phenomenon in which image quality deteriorates when printing the scanned data occurs.

Second, in order to maintain a separate distance between the scanning head (2) and the document (1) to install a push-bar, a separate additional device on the transport path of the document (1), the cost Rise, and the structure is compounded.

Accordingly, the present invention has been made to solve such problems, and an object of the present invention is to apply different shading correction coefficients depending on the position of the document transferred on the readable area of the scanning head without installing additional equipment. Accordingly, the present invention provides a shading correction method of a shuttle scanner that maximizes the efficiency of shading correction operation and prevents deterioration of image quality by suppressing an error in shading correction coefficient.

1 is a schematic structural diagram of a typical shuttle scanner,

2 is a schematic structural diagram showing a feed path of a document;

3 is a view illustrating a scanning area in which a scanning head of a general shuttle scanner can scan at one time;

4 is a voltage waveform diagram obtained by the photoelectric conversion element of the scanning head,

5A to 5C are views showing a state in which the separation distance between the original and the scanning head is changed according to the transfer position of the original.

5A is a view showing when the leading end of a document is transferred;

5B is a view showing when the intermediate portion of the original is transferred;

5C is a view showing when the rear end of the original is transferred;

6 is a schematic block diagram of a shading correcting apparatus of a shuttle scanner applied to the present invention;

7 is a diagram illustrating a state in which a shading correction coefficient for each transfer position of an original is stored in a table form;

8 is a flowchart illustrating an operation of the shading correction method of the shuttle scanner according to the present invention.

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

61: scanning control unit 62: ROM

63: RAM 64: Lamp

65: lamp driver 66: optical module unit

67: photoelectric conversion element 68: step motor unit

69: analog / digital converter 70: shading memory

71: shading correction control unit 72: shading correction unit

A1 to A128, B1 to B128, C1 to C128,... , M1 to M128: shading correction coefficient

A feature of the present invention for achieving this object is that, if a scanning operation is selected, the document is transferred to the scanning area; Scanning an original reaching the scanning area; Detecting the transfer position of the document; Detecting a shading correction coefficient in a predetermined pixel unit corresponding to the detected position of the document; The shading correction factor of the detected pixel unit is applied to the pixels of the scanned data one-to-one to perform shading correction.

Here, the shading correction coefficient divides the transfer position of the document to be transferred into a plurality of areas; The same gradation value is detected from a plurality of pixels in correspondence to the separation distance between the original and the scanning head for each of the divided plurality of regions.

Also, the plurality of areas includes three areas consisting of the leading end of the original, the middle part, and the rear end of the document based on the document transfer path.

In addition, the shading correction coefficient is stored in the nonvolatile memory so that the preservation state is maintained irrespective of turning on and off the power.

Further, the conveyance position of the original detects the conveying amount of the conveying means for conveying the original, detects the specification of the original and substitutes the conveying amount of the conveying means in the specification of the original.

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.

6 is a schematic block diagram of a shading correcting apparatus of a shuttle scanner applied to the present invention.

Referring to FIG. 6, the scanning controller 61 generates a timing signal for performing a series of scanning operations according to a program stored in a ROM 62 and manages the overall system operation. The ROM 62 stores a program and reference data having a certain flow so that the scanning control unit 61 can control the scanning system in a predetermined order. The RAM 63 stores temporary data generated while the scanning control unit 61 controls the system.

The lamp 64 outputs light of a predetermined intensity to read the image information of the original with the amount of reflected light. The lamp driver 65 receives a control signal from the scanning controller 61 at a suitable time to drive the lamp 64 and turns on and off the lamp 64.

The optical module unit 66 reflects the light output from the lamp 64 to the original, and forms an optical path such that the reflected light is incident on the photoelectric conversion element 67. The step motor unit 68 receives the driving signal from the scanning control unit 61 and moves the optical module unit 66 along the sub-scanning direction of the original with a predetermined resolution.

The photoelectric conversion element 67 photoelectrically converts light incident through the optical module unit 66 into an electrical analog signal proportional to the amount of light. The analog / digital converter 69 converts an analog image signal into digital image data corresponding to a preset number of bits.

The shading memory 70 stores image data digitized by the analog / digital converter 69, and particularly, stores the shading correction coefficient detected for the shading correction operation. Here, the shading memory 70 tables and stores the shading correction coefficients corresponding to the transport positions of the originals.

The shading correction control unit 71 reads the shading correction coefficient for each transfer position of the original stored in the shading memory 70 for each pixel, and applies the shading correction coefficient corresponding to each pixel of the image data stored in the shading memory 70. To control the correction for each pixel unit to compensate for the shading correction coefficient.

The shading correction unit 72 corrects and outputs image data stored in the shading memory 70 by applying a shading correction coefficient to each pixel according to the control operation of the shading correction control unit 71.

That is, the photoelectric conversion element 67 converts the reflected light incident through the optical module unit 66 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 67 is driven at a preset timing in accordance with a sensor driving clock provided from the scanning control unit 61, and the analog image having a constant number of pixels in the photoelectric conversion element 67 according to the preset resolution. Output the signal. The scanning control unit 61 controls the lamp 64 to be turned on and off and simultaneously controls the amount of light reflected in proportion to the original density to be incident on the photoelectric conversion element 67 via the optical module unit 66. Accordingly, the incident reflected light is converted into an analog voltage signal proportional to the intensity of the light and output according to the characteristics of the photoelectric conversion element 67.

Thereafter, the analog-to-digital converter 69 converts the analog image signal converted by the photoelectric conversion element 67 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 70 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 69 at the address of each pixel position. Dummy scanning refers to an operation in which the photoelectric conversion element 67 scans a reference pattern provided on the opposite surface. In this case, a white panel, a white paper, a white roller, or the like may be used as the reference pattern.

Subsequently, the shading correction control unit 71 reads pattern data for each pixel stored in the shading memory 70 for each address and divides the preset maximum brightness value by pixel unit 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 70. In addition, the shading correction controller 71 outputs the shading correction coefficient for each pixel stored in the shading memory 70 in correspondence with the scanning data output from the analog / digital converter 69 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 69 converts an analog image signal input from the photoelectric conversion element 67 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 72 displays the digital scanning data output from the analog / digital conversion unit 69 and the shading correction coefficient for each pixel output by the control of the shading correction control unit 71 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 Figures 7 and 8 with respect to the operation of the present invention configured as described above are as follows.

First, the transfer position LF of the document is divided into a plurality of areas, and the shading correction coefficients A1 to A128, B1 to B128, C1 to C128, ..., M1 to M128 for each area are calculated based on the experimental values. That is, the separation distance between the photoelectric conversion element 67 and the original is detected differently in each pixel unit according to the transfer position of the original, whereby the gray level of the scanning data is different from each other. Therefore, when performing the shading correction operation, different shading correction factors should be applied depending on the feed position of the original. The calculated shading correction coefficient for each transfer position of the original is stored in the ROM 62 in the form of a look-up table as shown in FIG.

Here, the shading correction coefficient for each transfer position of the original is preferably stored in the ROM 62 because the contents thereof should be preserved even when the power of the system is cut off. In addition to the ROM 62, non-volatile storage such as nonvolatile RAM (NVRAM) may be used. It may be replaced by means.

In addition, when the transfer position of the document is divided into a plurality of areas, more shading correction operations can be performed as the number of divided areas increases, but the amount of data (shading correction coefficients) to be stored is enormous and the scanning control unit 61 processes them. Since the amount of data can increase and the processing speed can be reduced, it can also be divided into three areas such as the front end, the middle part, and the rear end of the original.

Subsequently, when a scanning operation command is received by the user (S1), the scanning controller 61 may drive the lamp 64, the optical module unit 66, the photoelectric conversion element 67, and the like to perform a scanning operation. Switch the system to the state. In addition, the scanning controller 61 scans the reference pattern attached to the predetermined position of the scanner (S2) and stores the white reference value in the shading memory 70 with respect to the obtained pattern data.

On the other hand, when the detection operation of the white reference value is completed, the scanning control unit 61 drives the pickup roller, the driving roller and the discharge roller in sequence to transfer the original to be scanned (S3), and simultaneously scan the original and transfer the original. The position LF is detected (S4). At this time, the image information detected by the scanning operation is converted into scanning data digitized by the analog / digital converter 69, and the scanning data is stored in the shading memory 70. Here, briefly explaining a method of detecting the feed position LF of the document, the scanning control unit 61 detects the rotational amount of the driving roller to calculate the feed distance of the original, and the calculated feed distance is used as the standard of the original. The feed position of the original can be detected by substituting on.

If the feed position LF of the original detected by the scanning control unit 61 exists in an arbitrary area divided into a plurality, the scanning control unit 61 determines the transfer position LF of the detected original as shown in FIG. In the same manner, the shading correction coefficient corresponding to the feed position LF of the document is detected by substituting the look-up table stored in the ROM 62. That is, when it is determined that the detected transfer position LF of the document is within the range of "0 <LF ≤ X1" among the areas divided into N (N is a natural number) as shown in FIG. 8 (S5), the scanning controller 61 detects the shading correction coefficients A1 to A128 for each pixel of the "mode A" corresponding to the range of "0 <LF≤X1" from the table stored in the ROM 62, and detects the detected shading for each pixel. Shading correction is performed by applying correction factors A1 to A128 (S6).

Further, if it is determined that the detected feed position LF is within the range of "X1 <LF ≤ X2" (S7), the scanning control section 61 reads "X1 <LF ≤ X2 from the table stored in the ROM 62. Shading correction coefficients B1 to B128 for each pixel of the "mode B" corresponding to the range of "" are detected, and shading correction operations are performed by applying the detected shading correction coefficients B1 to B128 for each pixel (S8). ).

Further, if it is determined that the detected document feed position LF is within the range of " X2 &lt; LF≤X3 " (S9), the scanning control section 61 reads " X2 &lt; LF≤X3 from the table stored in the ROM 62. Shading correction coefficients C1 to C128 for each pixel of "mode C" corresponding to the range of "" are detected, and shading correction operations are performed by applying the detected shading correction coefficients C1 to C128 for each pixel (S10). ). This process is repeated for each divided region.

If it is determined that the detected feed position LF is within the range of "X (N-1) &lt; LF? XN " (S11), the scanning control section 61 reads " from the table stored in the ROM 62 " Shading correction coefficients M1 to M128 of each of the "mode M (M is a natural number)" corresponding to the range of X (N-1) <LF≤XN "are detected, and the detected shading correction coefficients for each pixel ( Shading correction is performed by applying M1 to M128 (S12).

If it is determined that the feed position LF of the original detected in step 11 (S11) is not included in the range of "X (N-1) <LF≤XN", this means that the original is moved out of the scannable area and the eject roller is moved. Since it means that the discharge through, the scanning control unit 61 stops driving each component in the system (S13). Therefore, accurate shading correction operation corresponding to the transfer position of the original can be performed.

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 shading correction method of the shuttle scanner according to the present invention the following advantages occur.

That is, the transfer position of the document is divided into a plurality of areas, and different shading correction coefficients are stored for each of the divided areas, the transfer position of the original is sensed, and the shading correction coefficient corresponding to the detected transfer position is stored. By detecting and performing shading correction, a more accurate shading correction result can be obtained.

Claims (5)

In the shading correction method of a shuttle type scanner in which a scanning head sequentially scans a plurality of pixels by a preset band size in a scanning direction of a document in one scanning operation: If a scanning job is selected, transferring the original to a scanning area; Scanning the original that has reached the scanning area; Detecting a transfer position of the document; Detecting a shading correction coefficient in the pixel unit corresponding to the detected position of the document; And And shading correction operation by applying the detected shading correction coefficient in units of pixels to the pixels of the data scanned in the scanning step one by one. The method of claim 1, wherein the shading correction coefficient is Dividing the conveying position of the document to be conveyed into a plurality of areas; The shading correction method of the shuttle scanner according to claim 1, wherein the same gray level value is detected from the plurality of pixels corresponding to the separation distance between the document and the scanning head. The method of claim 2, wherein the plurality of areas, Shading correction method of the shuttle scanner comprising a three areas consisting of the leading end, the middle and the rear end of the document based on the transport path of the document. The method of claim 2, wherein the shading correction coefficient is Shading correction method of a shuttle type scanner, characterized in that stored in a non-volatile memory so that the preservation state is maintained irrespective of the power on and off. According to claim 1, wherein the feed position of the document, And detecting the conveying amount of the conveying means for conveying the original, and detecting the specification of the original by substituting the conveying amount of the conveying means into the specification of the original.