KR100268340B1 - Method for shading correction in a shuttle type scanner - Google Patents

Abstract

If a scanning job is selected, after driving the scanner, the document is transferred to the scanning area; Detecting a conveying position of the original reaching the scanning area; Detecting a reference sheet having an inclination corresponding to a conveyed position of the detected original among a plurality of reference sheets attached to have different inclinations; Move the scanning head to the detected reference sheet, and scan the reference sheet to detect a white reference value; Shading correction is performed by applying a preset shading correction coefficient to the detected white reference value.

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 a shuttle scanner capable of simultaneously scanning a plurality of pixels in band units by one scanning process. By attaching a plurality of reference sheets with different inclinations and scanning one of the plurality of reference sheets according to the transport position of the original, uniform scanning data can be obtained regardless of the change of the separation distance between the original and the scanning head. A shading correction method of a shuttle scanner that can be obtained.

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 scanning head configured to be spaced apart from the effective reading area of the document 101 by a predetermined distance to scan image information recorded on the document 101 ( 102, a guide rail 103 for guiding the left and right reciprocating motion of the scanning head 102, and a carriage return motor providing a driving force for the scanning head 102 to reciprocate from side to side. Motor 104, a carriage belt 105 and a cassette 106, which are simultaneously mounted to the carriage return motor 104 and the scanning head 102, and which transfer the driving force of the carriage return motor 104 to the scanning head 102, Pickup roller 107 for picking up the original 101 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 107 to the effective reading area of the scanning head 102. (108) and a batch for ejecting the document 101 from which the scanning operation is finished A reference which is included in the roller 109 and the flow trajectory of the scanning head 102 and attached to a point outside the effective reading area of the scanning head 102 and in which a reference pattern of a predetermined type is recorded so that the scanning head 102 can be read It consists of the sheet 110.

Then, the detailed structure of the scanning head 102, the lamp 111 is provided at its end so that the light emitted from the lamp 111 is irradiated to the document 101. In addition, a photoelectric conversion element (using a "charge coupled device (CCD)" 112) for detecting the light reflected from the document 101 and converting the light reflected from the document 101 into electrical data is provided inside the scanning head 102. And a lens 113 for focusing the reflected light between the lamp 111 and the photoelectric conversion element 112 so that the light reflected from the document 101 reaches a predetermined region of the photoelectric conversion element 112. Here, the lamp 111, the photoelectric conversion element 112 and the lens 113 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 102 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 102 scans the reference sheet 110 on which a white pattern is printed due to the nonuniformity of the lamp 111 and the nonuniformity of sensitivity per pixel of the photoelectric conversion element 112 within the read width section. In either case, the output of the scanning head 102 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 110 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 document 101 and applying a shading correction coefficient to the scanned data, image information almost identical to the image recorded on the document 101 can be obtained.

On the other hand, when the scanning operation command is received, the originals 101 loaded on the cassette 106 are sequentially picked up one by one by the pickup roller 107 and supplied to the driving roller 108 side. The driving roller 108 transfers the document 101 transferred to the pickup roller 107 to the readable area of the scanning head 102. Accordingly, the transferred document 101 is located in the readable area of the scanning head 102, and at this time, the scanning head 102 scans the image recorded in the document 101 in band units for the document 101. ) Is detected. Then, when the scanning operation for one band is finished, the document 101 is discharged to the outside by the drive roller 108 and the discharge roller 109.

Here, when the light emitted from the lamp 111 of the scanning head 102 is focused by the lens 113 and then focused on the photoelectric conversion element 112 by the lens 113, the lens 113 The separation distance between the scanning head 102 and the document 101 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 document 101 is conveyed, when the leading end of the document 101 is located in the readable area of the scanning head 102, the separation distance between the document 101 and the scanning head 102 is shown. In this case, the discharge roller 109 side is far and the driving roller 108 side is close (see FIG. 5A).

And, when the intermediate portion of the document 101 is located in the readable area of the scanning head 102, the separation distance between the document 101 and the scanning head 102, the discharge roller 109 side and the drive roller The 108 side is in the same state (see FIG. 5B).

Finally, when the rear end of the document 101 is located in the readable area of the scanning head 102, the distance between the document 101 and the scanning head 102 is close to the discharge roller 109 side. The driving roller 108 is far away (see FIG. 5C).

This indicates that the separation distance between the scanning head 102 and the document 101 sequentially changes during the process of continuously feeding the document 101 to the readable area of the scanning head 102, and thus the lamp 111. ), And the distance from the document 101 to the photoelectric conversion element 112 through the lens 113 is changed. Therefore, the intensity of light reaching the photoelectric conversion element 112 is changed.

However, although the intensity of the light reaching the photoelectric conversion element 112 changes according to the change of the separation distance between the scanning head 102 and the original 101 generated during the transfer of the original 101, the original 101 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 102 and the document 101 in the case of installing a push-bar, a separate additional device on the transport path of the document 101, 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 view illustrating a state in which a plurality of reference sheets are mounted in a shuttle scanner applied to the present invention;

8A to 8C are voltage waveform diagrams obtained by a photoelectric conversion element according to a transfer position of an original;

8D to 8F are output waveform diagrams when a shading correction operation is performed by applying the same shading correction coefficient to each waveform shown in FIGS. 8A to 8C;

9 is a view showing a state in which the reference sheet scanning position of the scanning head for each transfer position of an original is set;

10 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>

601: Scanning control unit 602: ROM

603: RAM 604: lamp

605: lamp driver 606: optical module unit

607: photoelectric conversion element 608: step motor unit

609: analog / digital converter 610: shading memory

611: shading correction unit 612: shading correction unit

613, 64, 615: reference sheet 616: scanning head

617: Manuscript 618: Eject roller

619: driving roller

A feature of the present invention for achieving this object is that if a scanning job is selected, the scanner is driven and then the document is transferred to the scanning area; Detecting a conveying position of the original reaching the scanning area; Detecting a reference sheet having an inclination corresponding to a conveyed position of the detected original among a plurality of reference sheets attached to have different inclinations; Move the scanning head to the detected reference sheet, and scan the reference sheet to detect a white reference value; The shading correction operation is performed by applying a preset shading correction coefficient to the detected white reference value.

Here, the shading correction coefficient is obtained by performing a pseudo scanning operation on the reference sheet whose slope is "0" before the document is transferred.

Further, the plurality of reference sheets divides the transfer position of the document to be transferred into a plurality of areas; Each divided area has the same inclination as the inclination according to the separation distance between the original and the scanning head, and each of them is attached to have a different inclination.

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 information about the reference sheet having a slope corresponding to the detected transfer position of the original is stored in the nonvolatile memory so that the preservation state is maintained regardless of the turning on and off of the power source.

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 601 generates a timing signal for performing a series of scanning operations according to a program stored in a ROM 602 and manages the overall system operation. In particular, the scanning control unit 601 stores the position information with a plurality of reference sheets attached, and controls the transfer position of the scanning head 601 according to the position information.

The ROM 602 stores programs and reference data having a certain flow so that the scanning control unit 601 can control the scanning system in a predetermined order. The RAM 603 stores temporary data generated while the scanning control unit 601 controls the system.

The lamp 604 outputs light of a predetermined intensity to read the image information of the original with the amount of reflected light. The lamp driver 605 turns on and off the lamp 604 by receiving a control signal from the scanning controller 601 at an appropriate time to drive the lamp 604.

The optical module unit 606 reflects the light output from the lamp 604 to the document, and forms an optical path so that the reflected light is incident on the photoelectric conversion element 607. The step motor unit 608 receives the driving signal from the scanning control unit 601 and moves the optical module unit 606 along the sub-scanning direction of the original with a predetermined resolution.

The photoelectric conversion element 607 photoelectrically converts light incident through the optical module unit 606 into an electrical analog signal proportional to the amount of light. The analog / digital converter 609 converts an analog image signal into digital image data corresponding to a preset number of bits.

The shading memory 610 stores image data digitized by the analog / digital converter 609, and in particular, stores the shading correction coefficients detected for the shading correction operation.

The shading correction control unit 611 reads the shading correction coefficient stored in the shading memory 610 for each pixel unit, and applies the shading correction coefficient corresponding to each pixel to the image data stored in the shading memory 610 by the shading correction coefficient. The correction operation of each pixel unit is controlled to compensate.

The shading correction unit 612 corrects and outputs image data stored in the shading memory 610 by applying a shading correction coefficient to each pixel according to the control operation of the shading correction controller 611.

That is, the photoelectric conversion element 607 converts the reflected light incident through the optical module unit 606 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 607 is driven at a preset timing according to the sensor driving clock provided from the scanning control unit 601, and the photoelectric conversion element 607 according to the preset resolution has a constant number of analog images. Output the signal. The scanning control unit 601 controls the lighting and turning off state of the lamp 604 and simultaneously controls the amount of light reflected in proportion to the original density to be incident on the photoelectric conversion element 607 through the optical module unit 606. 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 607 and output.

Thereafter, the analog / digital converter 609 converts the analog image signal converted by the photoelectric conversion element 607 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 for representing a single pixel in 8 bits as in a normal case, for the gray scales of images binarized in black & white form, 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 610 is detected by scanning a reference pattern recorded on any one of a plurality of reference sheets 613, 614, 615 as shown in FIG. The pattern data digitized by the / digital converter 609 is stored at the address of each pixel position. Dummy scanning refers to an operation in which the photoelectric conversion element 607 scans a reference pattern of a reference sheet 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 controller 611 reads the pattern data for each pixel stored in the shading memory 610 for each address during the pseudo scanning, and divides the preset maximum brightness value by pixel unit, 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 610. In addition, the shading correction control unit 611 outputs the shading correction coefficient for each pixel stored in the shading memory 610 in correspondence with the scanning data output from the analog / digital converter 609 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 609 converts an analog image signal input from the photoelectric conversion element 607 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 612 displays the digital scanning data output from the analog / digital conversion unit 609 and the shading correction coefficient for each pixel output by the control of the shading correction control unit 611 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.

Meanwhile, as shown in FIG. 7, the shuttle scanner applied to the present invention includes a plurality of reference sheets 613, which are included in the flow trajectory of the scanning head 616 and are outside the effective reading area of the scanning head 616. 614 and 615 are attached. At this time, a plurality of reference sheets (613, 614, 615) are attached in an inclined state with an inclination corresponding to the transfer position of the original, respectively.

That is, as mentioned above, when the tip portion of the document 617 is located in the readable area of the scanning head 616, looking at the separation distance between the document 617 and the scanning head 616, the discharge roller ( 618) the side is far away and the driving roller 619 side is inclined.

In the case where the intermediate portion of the document 617 is located in the readable area of the scanning head 616, the separation distance between the document 617 and the scanning head 616 is determined by the discharge roller 618 and the driving roller. The side of 619 has the same slope.

Finally, when the rear end of the document 617 is located in the readable area of the scanning head 616, looking at the separation distance between the document 617 and the scanning head 616, the discharge roller 618 side is close The driving roller 619 has a distant slope.

At this time, since the document 617 is continuously conveyed on the conveyance path, the separation distance between the document 617 and the scanning head 616 also changes continuously. In order to cope with this, it is effective to attach as many reference sheets 613, 614 and 615 as possible, but there are a large number of scanning heads 616 and space constraints for attaching the reference sheets 613, 614 and 615. Due to the necessity of precise control for precisely performing the scanning operation at the position where any reference sheet is attached among the reference sheets 613, 614, and 615, three areas of the front end, the middle part, and the rear end of the document are largely moved. It is preferable to divide by.

Meanwhile, since the configuration and functions other than the reference sheets 613, 614, and 615 described above are identical to those of FIG. 1, the overlapping description will be omitted.

The operation of the present invention configured as described above will be described with reference to FIGS. 8 to 10.

First, the white reference value should be detected before performing the shading correction operation. That is, the waveform detected by the scanning head 616 by scanning the reference sheets 613, 614, and 615 shows a white reference value in the form of a wave wave as shown in part “A” of FIG. 4. However, since the separation distance between the document 617 and the scanning head 616 varies as the feed position of the document 617 changes, the scanning head 616 scans the document 617 in which no data is recorded. As shown in Figs. 8A to 8C, the shape of the waveform varies. This means that the output levels of the white reference values appear different from each other when the document 617 is scanned. If the same shading correction coefficient is applied to this, distortion occurs depending on the feed position of the document 617 (Fig. 8d to 8f). Accordingly, the scanning head 616 detects the transfer position of the document 617 and the reference sheets 613, 614, 615 attached to the main body of the shuttle scanner by the inclination corresponding to the detected transfer position of the document. After the scanning waveform is set to the white reference value, the shading correction operation is performed by applying the shading correction coefficient.

To this end, as shown in FIG. 9, the transfer position of the document 617 is divided into a plurality of regions, and the divided region-specific information and the reference sheet scanning position of the scanning head 616 are stored in the ROM 602. In addition, a plurality of reference sheets 613, 614, and 615 having different inclinations for respective regions corresponding to the region-specific information stored in the ROM 602 are located on the readable region outside the effective reading region of the scanning head 616. Is attached to.

On the other hand, as shown in Figure 10, when the scanning operation command is received (S101), the scanning control unit 601 drives the lamp 604, the optical module unit 606, the photoelectric conversion element 607 and the like scanning operation Switch the system to a state capable of performing, and transfer the document 617 to be scanned (S102).

In addition, the scanning control unit 601 detects the transfer position LF of the original 617 to be transferred (S103), and transfers the position of the original 617 stored in the ROM 602 to the detected transfer position LF information. Reference sheet scanning position information of each scanning head 616 is inserted into the reference sheet 613 to detect one of the reference sheets 613, 614, and 615 corresponding to the transfer position LF. That is, if 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. 9 (S104), the scanning control unit 601 controls to scan the first reference sheet (eg, 613) corresponding to the range "0 <LF≤X1" from the table stored in the ROM 602. At this time, the image information detected by the scanning operation is converted into scanning data digitized by the analog / digital converter 609, and the scanning data is stored in the shading memory 610.

Herein, a brief description will be made of a method for detecting the feed position LF of the document. The scanning control unit 601 detects the rotation amount of the driving roller 619 to calculate the feed distance of the document 617, and calculates the Substituting the feed distance to the standard of the original 617 can detect the transfer position of the original 617. Thereafter, the scanning controller 601 applies shading correction coefficients to the pattern data stored in the ROM 602 to perform shading correction (S105).

Further, if it is determined that the detected document feed position LF is within the range of "X1 <LF ≤ X2" (S106), the scanning control unit 601 reads "X1 <LF ≤ X2 from the table stored in the ROM 602. The second reference sheet (eg, 614) corresponding to the range of "" is controlled to be scanned, and the shading correction operation is performed by applying the shading correction coefficient to the scanned pattern data (S107).

If it is determined that the detected feed position LF is within the range of "X (N-1) &lt; LF? XN '(S108), the scanning control unit 601 reads " from the table stored in the ROM 602 &quot;. The control is performed to scan the N-th reference sheet (eg, 615) corresponding to the range of X (N-1) <LF≤XN ", and a shading correction operation is performed by applying a shading correction coefficient to the scanned pattern data (S109). ).

If it is determined that the conveyance position LF of the original detected in step 108 (S108) is not within the range of "X (N-1) <LF≤XN", this means that the original moves out of the scannable area and moves the eject roller. Since it means that the discharge through, the scanning control unit 601 stops driving each component in the system (S110). 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 the reference patterns having different inclinations corresponding to each of the divided areas are attached to the readable area outside the effective reading area of the scanning head, The shading correction operation may be performed by scanning the reference pattern corresponding to the detected transfer position by detecting the, thereby obtaining a more accurate shading correction result.

Claims (6)

A plurality of reference sheets having different inclinations are attached on the readable area beyond the effective reading area of the scanning head, and in one scanning operation, the scanning head sequentially processes the plurality of pixels by the preset band size in the document feeding direction. In the shading correction method of a shuttle type scanner to scan by: If a scanning job is selected, driving the scanner and transferring the document to the scanning area; Detecting a transfer position of the document reaching the scanning area; Detecting a reference sheet having an inclination corresponding to the conveyed position of the original among the plurality of reference sheets attached to have different inclinations; Moving the scanning head to the detected reference sheet, and scanning the reference sheet to detect a white reference value; And Shading correction method comprising the step of performing a shading correction operation by applying a preset shading correction coefficient to the detected white reference value. The method of claim 1, wherein the shading correction coefficient is Shading correction method of a shuttle type scanner, characterized in that obtained by performing a pseudo scanning operation on the reference sheet of the slope "0" before the document is transferred. The method of claim 1, wherein the plurality of reference sheets, Dividing the conveying position of the document to be conveyed into a plurality of areas; The shading correction method of the shuttle scanner, characterized in that each of the plurality of divided areas having the same inclination according to the difference in the distance between the document and the scanning head, each attached to have a different inclination. The method of claim 3, 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. According to claim 1, wherein the information about the reference sheet having a slope corresponding to the conveying position of the detected document, 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.