JP2014030142A - Reading device, correction method in the reading device, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reading device that improves the accuracy of correcting read data corresponding to the position of a foreign matter.SOLUTION: The position of a foreign matter is detected in a reading area for optically reading a document, and it is determined whether read data obtained by reading the document is data of a character area. When it is determined to be data of a character area, data corresponding to the position of the foreign matter detected by detection means within the read data is corrected by replacing it with data representing a document color.

Description

  The present invention relates to a reading device for correcting read data, a correction method in the reading device, and a program.

  2. Description of the Related Art Conventionally, when a scanning device is used to optically read a document, and a dust (foreign matter) such as dust or paper dust is detected in the reading unit, the pixel data at the detected position is used as an adjacent pixel. Correction is performed based on the data (Patent Document 1).

JP 2005-1117090 A JP 2002-077584 A

  When the dust width is greater than or equal to a predetermined pixel, correction by linear interpolation or the like based on the data of adjacent pixels may cause distortion instead of the corrected read image, which may be difficult to see. For example, in the case of an image such as a landscape photograph, even if the position of dust is linearly interpolated with pixel values representing the surrounding landscape, there is no visual discomfort. However, in the case of a character, for example, a black streak caused by dust is generated at the center of the character, and when the occurrence point is linearly interpolated with surrounding pixel values, the character may appear to be extended, rather than visually. Will cause a sense of incongruity. Patent Document 2 describes that interpolation processing is not performed when the width of dust is equal to or larger than a predetermined pixel. However, when correction processing is not performed, black streaks remain as they are, and image quality is reduced. Will be reduced.

  An object of the present invention is to solve such conventional problems. In view of the above, an object of the present invention is to provide a reading apparatus that improves the correction accuracy of read data corresponding to the position of a foreign object, a correction method in the reading apparatus, and a program.

  In order to solve the above-described problem, a reading apparatus according to the present invention is a reading apparatus that optically reads a document, and includes a detection unit that detects the position of a foreign object in the reading region, and the read data read from the document is a character. Corresponding to the position of the foreign matter detected by the detecting means in the read data when the determining means determines whether the data is an area data and the character area data is determined by the determining means Correction means for correcting the data to be corrected by replacing the data representing the document color obtained from the read data.

  According to the present invention, it is possible to improve the correction accuracy of read data corresponding to the position of a foreign object.

1 is a diagram illustrating an internal configuration of an image forming apparatus. 1 is an external perspective view of an image forming apparatus. 1 is a diagram illustrating an internal configuration of an image reading apparatus configured in an image forming apparatus. It is a figure which shows the structure around an image sensor unit. It is a figure which shows the internal structure of an image sensor unit. It is a figure which shows a reflected light path. It is a figure which shows light quantity distribution of a light source. It is a figure which shows the other structural example of an image sensor unit. It is a block diagram which shows the structure of an image signal processing part. It is a figure which shows the procedure of the dust detection correction process in a present Example. It is a figure which shows the procedure of an image area separation process. It is a figure which shows the procedure of a background level detection process. It is a figure for demonstrating a correction process.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the following embodiments do not limit the present invention according to the claims, and all combinations of features described in the present embodiments are not necessarily essential to the solution means of the present invention. . The same constituent elements are denoted by the same reference numerals, and the description thereof is omitted.

[Entire configuration of image forming apparatus]
FIG. 1 is a diagram illustrating an internal configuration of an image forming apparatus according to an embodiment of the present invention. In this embodiment, the image forming apparatus is, for example, a copying machine, a printer, or a facsimile, and has an image reading function. Further, the image forming apparatus may be a complex machine in which functions such as a copying machine, a printer, and a facsimile are compounded.

  The image forming apparatus 100 shown in FIG. 1 is roughly divided into an apparatus main body 101, an image reading apparatus 103 provided on the upper part of the apparatus main body 101, and an automatic document feeder (ADF: auto) provided on the upper part of the image reading apparatus 103. Document feeder) 126. The automatic document feeder 126 includes an ADF separation unit 115, a sheet discharge conveyance unit 116, a document discharge unit 117, a document pressing plate 118 that presses a book document, and a sheet document conveyance unit 121. The automatic document feeder 126 separates the sheet document D placed on the document table 106 one by one by the ADF separation unit 115 and supplies the separated sheet document D to the image reading device 103. The image reading device 103 reads the sheet document D fed onto the flow reading glass 109 by the automatic document feeder 126 by the image sensor unit 108 in a stopped state. The image reading apparatus 103 can also read a sheet document D or a book document placed on the document table glass 107 by the user. At that time, the image sensor unit 108 is a so-called line sensor, and optically reads the sheet document D and the book document while moving in the sub-scanning direction (left and right direction in FIG. 1). The sub-scanning direction is a left-right direction in FIG. 1, and the main scanning direction is a direction intersecting the sub-scanning direction, that is, a direction indicated by an arrow B in FIG. The document pressing plate 118 is formed by being laminated with a white sheet, sponge or the like in order to prevent the document placed on the document table glass 107 from floating. The document pressing plate 118 is extended until the left end 118a of the document pressing plate 118 is positioned on the left side of the book reading range start position 107a and the right end 118b is positioned on the right side of the book reading range end position 107b.

  The image reading apparatus 103 sends image reading information to the printing unit 104 of the apparatus main body 101. The apparatus main body 101 prints an image on the sheet P (recording medium) stacked on the cassette paper feeding unit 112 based on the image reading information read by the image reading apparatus 103. The printing unit 104 is, for example, an electrophotographic printing mechanism that uses an LED array. In that case, the apparatus main body 101 includes an LED head unit 110. In addition, the apparatus main body 101 includes a recording sheet discharge unit 113 and a cartridge cover unit 114 that are configured to be capable of stacking a plurality of sheets P on top of the image forming unit 111, the cassette sheet feeding unit 112, and the printing unit 104. including. Further, the apparatus main body 101 includes a joining unit 119 that joins the image reading apparatus 103 and the printing unit 104, a facsimile control unit 120, a double-sided transport unit cover 122, a transport direction switching unit 123, and a resist transport unit 124. Further, the apparatus main body 101 includes an MP (multi-paper) paper feeding unit 125 and a double-sided conveyance unit 150 in the printing unit 104.

  FIG. 2 is an external perspective view of the image forming apparatus 100. As illustrated in FIG. 2, the image forming apparatus 100 includes an operation unit 105. The operation unit 105 includes a display unit such as a display and input keys such as a numeric keypad. The operation unit 105 can receive various instructions from the user, or the user can check the state of the image forming apparatus 100 on the display. The ADF pressure plate 102 shown in FIG. 2 is rotatably attached to the image reading apparatus 103 by a hinge portion 102a, and the user can open and close the automatic document feeder 126 in the direction of a double arrow A in FIG. One hinge portion 102 a is provided on each of the left and right sides of the back side of the apparatus main body 101, and the user can open the ADF pressure plate 102 rearward by lifting the front side of the ADF pressure plate 102. The hinge portion 102a can hold the ADF pressure plate 102 in a state of being opened at a predetermined angle, for example, 70 degrees, by a combination of a damper, a cam, a spring member, and the like. The user places a document such as a sheet document or a book document on the platen glass 107 with the ADF pressure plate 102 opened.

  FIG. 3 is a diagram showing an internal configuration of the image reading device 103 and the automatic document feeder 126 of the image forming apparatus 100. The image reading apparatus 103 may be integrated with the image forming apparatus 100 as shown in FIG. 1, or may be configured as a separate body. As shown in FIG. 3, a white sheet 109 c is provided on the lower surface of the jump table 109 b that projects from the upper part of the document table glass 107. The image reading device 103 performs shading correction of the image sensor unit 108 when the reading position of the image sensor unit 108 is below the white sheet 109c. In the image reading apparatus 103, the image sensor unit 108 passes under the jump table 109b for each scanning operation for reading a document. That is, shading correction is performed for each scanning operation, and the influence of the change in the light amount of the light source in the movable image sensor unit 108 with time can be reduced.

[Sheet original scanning operation]
Here, with reference to FIGS. 1 to 3, a flow reading operation when the image forming apparatus 100 executes image reading will be described. As shown in FIGS. 1 and 2, the document placing table 106 is provided on the ADF pressure plate 102. A pair of sliders 106 a are provided on the document placing table 106 so as to be slidable in a direction perpendicular to the sheet document conveying direction (that is, the sheet document width direction indicated by arrow B). By this pair of sliders 106 a, both sides of the sheet document stacked on the document placing table 106 can be aligned. That is, the width alignment of the sheet original can be performed by the pair of sliders 106a. An original length sensor 106b is provided on the original placing table 106, and the length of the set sheet original can be detected.

  In FIG. 3, the ADF separation unit 115 is provided with a plurality of document width sensors 115d for detecting the presence and width of a sheet document in the width direction of the sheet document. Only one document width sensor 115d is shown in FIG. The image forming apparatus 100 can detect the document size and the document setting direction based on detection signals from the document width sensor 115d and the document length sensor 106b. In FIG. 3, the sheet document conveying unit 121 is provided with a document feeding sensor 121 h and a document edge sensor 121 i. The document feed sensor 121h can detect whether or not a sheet document has been sent from the ADF separation unit 115 and the passage of the rear end of the sheet document. The document edge sensor 121i can detect the passage of the leading edge and the trailing edge of the sheet document. The detection signal is used for image reading timing control. The ADF separation unit 115 includes a pickup roller 115a that moves up and down by an actuator (not shown), a separation roller 115b, a retard roller 115c that is pressed against the separation roller 115b and rotates in the reverse direction, and the like.

  The sheet original is first stacked on the original placing table 106 by the user with the reading surface (original surface) facing up. Then, the pickup roller 115a descends, presses the sheet document against the document placing table 106, and feeds it between the separation roller 115b and the retard roller 115c. The retard roller 115c and the separation roller 115b separate and convey the sheet document one by one. Next, the registration roller 121a, the lead roller 121b, and the reading and conveying roller 121c convey the sheet document onto the flow reading glass 109 along the U-turn paper path along the document guide 121d.

  A sheet document pressing plate 121e pressed by an unillustrated urging spring presses and conveys the conveyed sheet document to the reading glass 109. During this time, the sheet document is continuously conveyed. At that time, the image sensor unit 108 has already moved to the sheet document reading position 109a and stopped, and reads the image information of the sheet document passing over the sheet document reading position 109a. Next, the jump table 109b scoops up the sheet document continuously conveyed to the ADF pressure plate 102 side. A reading conveyance roller (not shown) pressed against the reading conveyance roller 121c by a not-illustrated pressing spring and the reading conveyance roller 121c convey the sheet document. Further, the sheet discharge roller 117a and the sheet discharge roller 117b pressed by the sheet discharge roller 117b by the pressing spring discharge the sheet document to the document sheet discharge tray 117c.

[Image sensor unit configuration]
FIG. 4 is a diagram showing a configuration around the image sensor unit 108. The image sensor unit 108 irradiates the image surface of the sheet original with light from a light source including an LED, a resin light guide, and the like, and reflects the reflected light reflected on the image surface with a SELFOC lens (trademark) or the like. An image is formed on the one-dimensional sensor element array, and image information of the sheet original is read. The image sensor unit 108 moves in the left-right direction in FIG. 4 along the guide shaft 103c by a timing belt 103a, a drive pulley 103b rotated by a drive motor (not shown), and a driven pulley 103f. The image sensor unit 108 is supported by the guide shaft 103c by the carriage 103d and is urged upward by the spring 103e. The timing belt 103a and the carriage 103d are connected by a connecting member 103g. A spacer 108 a is interposed between the image sensor unit 108 and the document table glass 107. The image sensor unit 108 optically reads an image of a document placed on the platen glass 107 in a range from the book reading range start position 107a to the book reading range end position 107b in FIG. 1 while moving at a constant speed. .

  FIG. 5 is a diagram illustrating an internal configuration of the image sensor unit 108. The image sensor unit 108 irradiates a document with light from a light source including the LED 10 and the resin light guide 11. The reflected light is imaged on the light receiving sensor 13 which is a one-dimensional sensor element array by the Selfoc lens array 12 which is an imaging optical system, so that the image sensor unit 108 optically reads the image information of the document. Can do. The light source may be an axial lamp arranged in the main scanning direction. In the case of color reading, LEDs having different wavelength distributions of three colors of R (red), G (green), and B (blue), which are a plurality of colors, are used as a light source. For monochrome reading, for example, G (green) is used as a monochromatic light source. FIG. 5 shows only one LED for each light guide 11 to be described later for simplification.

  In the image sensor unit 108, a pair of light guide light sources including an LED 10 that is a light emitting element of a light source and a light guide 11 that guides light emitted from the LED 10 to a sheet document serves as an imaging optical system. The SELFOC lens array 12 is disposed on both sides. A light receiving sensor 13 is provided directly below the selfoc lens array 12. The image sensor unit 108 is disposed in the frame body 14. The light receiving sensor 13 has a plurality of light receiving elements 13 a arranged along the main scanning direction of the image sensor unit 108. As shown in FIG. 5, the LEDs 10 are respectively provided at one end of one light guide 11 and the other end of the other light guide 11. In the image sensor unit 108, the above-described constituent members are arranged at point-symmetrical positions with respect to the central axis C.

  Light emitted from each LED 10 travels in the sheet width direction (that is, the main scanning direction of the arrow B) while being repeatedly reflected in each light guide 11, and is emitted from the light emitting surface 11 a of the entire length of the light guide 11. To do. The light emitted from the light guide 11 irradiates the original E on the original table glass 107 as shown in FIG. 6, passes through the SELFOC lens array 12 and is received by the light receiving sensor 13. The light receiving sensor 13 as a photoelectric conversion element receives the reflected light of the document E and converts the reflected light into an electrical signal.

  FIG. 7 is a diagram showing the light amount distribution of the light guide light source of the image sensor unit 108. In FIG. 7, the light amount distribution based on the distance from the LED 10 on the one light guide 11 side is indicated by a solid line, and the light amount distribution based on the distance from the LED 10 on the other light guide 11 side is indicated by a dotted line. It is shown in The light amount distribution of the image sensor unit 108 as a whole is obtained by adding the light amounts of the respective LEDs 10 as indicated by a one-dot chain line. As shown in FIG. 7, the light amount of the light guide light source is averaged with respect to the distance and becomes constant. As shown in FIG. 5, by providing each LED 10 between the two light guides 11 on the opposite side, a light amount distribution in which the light amounts complement each other is obtained. Good read data can be obtained. Note that the LEDs 10 may be provided at both ends of one light guide 11. Further, as shown in FIG. 8, the LED 10 and the light guide 11 may be provided only on one side with the selfoc lens array 12 interposed therebetween.

[Image signal processing]
FIG. 9 is a block diagram illustrating a configuration of an image signal processing unit that processes a read image signal. The CIS 21 performs photoelectric conversion on the detection signal detected by the light receiving sensor 13 of the image sensor unit 108 to generate an analog signal. The CIS 21 includes an LED 10, a light receiving sensor 13, and an AMP • A / D (amplifier / analog / digital) converter 23. The analog signal generated by the CIS 21 is amplified by the amplifier circuit of the AMP / A / D converter 23 and converted into a digital signal by the A / D converter circuit. The sub CPU 30 stores the digital data converted into the digital signal in the memory 27.

  The image processing circuit 41 rearranges the digital data according to the image information for one line of the sheet document, and executes various image processes. Here, the image processing is, for example, shading correction, filter correction, dust detection processing or dust correction processing described later. The digital data subjected to the image processing is output to the image forming unit 111 via an I / F circuit (interface circuit) 42 or transmitted to an external host computer or the like for image reproduction.

  The sub CPU 30 controls, for example, the lighting time of the LED drive circuit 25 by controlling the reading unit 50. Further, the sub CPU 30 controls the AMP / A / D converter 23 based on the set value transmitted from the main CPU 24. The reading unit common power supply 26 can turn on / off a power supply (not shown) of the reading unit 50. The operation unit 105 displays a status display of the image reading apparatus 103 and an operation state of the entire image forming apparatus 100, and accepts a reading instruction from a user. The LED driving circuit 25 is supplied with electric power from the reading unit common power supply 26 and drives each LED of the CIS 21 under the control of the sub CPU 30. The AMP / A / D converter 23 is also supplied with power from the reading unit common power supply 26 and operates under the control of the sub CPU 30.

  The sub CPU 30 can adjust the reading level (luminance level) of the image by setting a conversion level for converting the analog signal in the AMP / A / D converter 23 into a digital signal. The main CPU 24 transmits setting values and the like stored in the memory 27 to the reading unit 50 via the sub CPU 30 and the communication I / F 51. The set values are the conversion levels of the AMP / A / D converter 23 and the set values for controlling the reading unit 50. The sub CPU 30 adjusts the reading level of the AMP / A / D converter 23 based on the set value received from the main CPU 24 and controls the reading unit 50. The main CPU 24 controls power supply to the reading unit 50 by switching the reading unit common power supply 26 to ON / OFF. The main CPU 24 can detect a failure of the LED 10 or an abnormality of the AMP / A / D converter 23 based on digital data representing image information obtained at the time of shading correction or reading level adjustment. When the image reading apparatus 103 is integrated with the image forming apparatus 100, the main CPU 24 controls the entire image forming apparatus 100 according to a program stored in a ROM (not shown) or the like. .

[Dust detection / correction processing]
FIG. 10 is a flowchart illustrating a procedure of processing for detecting and correcting dust (foreign matter) on the image reading position in the present embodiment. This process is performed when the image forming apparatus 100 executes image reading. Each process shown in FIG. 10 is executed by, for example, the main CPU 24 in FIG.

  First, when a user places a sheet document on the document table 106 and presses the copy button of the operation unit 105, the main CPU 24 starts an image reading process. First, as the pre-reading dust detection process, the main CPU 24 detects the presence or absence of dust and the dust position at the reading position on the flow reading glass 109 (S1001). When detecting dust, first, the main CPU 24 moves the image sensor unit 108 to the sheet original reading position 109a, and reads the white color of the opposed reading conveyance roller 121c at that position. The main CPU 24 stores the read white data in the memory 27. Next, the main CPU 24 compares the stored white data for each pixel with a luminance threshold for dust detection, determines a pixel having a luminance equal to or lower than the luminance threshold as dust, and positions of the pixels determined as dust And the number are detected and stored as dust information before reading. After the pre-read dust detection process is completed, the main CPU 24 conveys the sheet document to the reading position, and reads the document image of the sheet document line by line in the main scanning direction by a reading operation (S1002). Here, the flow-reading operation is as described above.

  When the main CPU 24 reads an image for one line in the main scanning direction, the main CPU 24 determines whether dust has been detected in S1001 (S1003). If it is determined that dust has been detected, it is determined whether or not the one line is a character area (S1004). In the determination process of S1004, an image area separation process is used.

  Here, the image area separation processing will be described with reference to FIG. When the image area separation process is started, the main CPU 24 sets a pixel corresponding to the tip on one line as a target pixel. Then, of the data for one line in the main scanning direction read in S1002, the absolute value of the difference in luminance value between the target pixel and the next pixel adjacent to the pixel in the main scanning direction on one line is calculated. And stored in the memory 27 (S1102). When the absolute value of the luminance value difference is calculated, it is determined whether or not the coordinates of the current target pixel are the rear end coordinates Ymax on one line (S1103). In this embodiment, the main scanning direction is the Y coordinate and the sub scanning direction is the X coordinate in the reading area. If it is determined that the rear end coordinate Ymax is not reached, the coordinate of the target pixel is advanced by “1” along the main scanning direction (S1104). Thereafter, the processing from S1102 is repeated. On the other hand, if it is determined in S1103 that the rear end coordinate is Ymax, the sum S of all absolute values calculated in S1102 and stored in the memory 27 is calculated (S1105).

  Next, the main CPU 24 determines whether or not the total sum S is equal to or greater than a threshold value (S1106). Here, when it is determined that the total sum S is equal to or greater than the threshold, it is determined that the current target line is a character area (S1108). In that case, a background level detection process described later is executed (S1109), and the process of FIG. 11 is terminated. On the other hand, if it is determined that the total sum S is less than the threshold value, it is determined that the current target line is an image region (S1107), and the processing in FIG.

  That is, in the process of FIG. 11, the sum of absolute values of the difference between the luminance values of the previous and subsequent pixels on one line in the main scanning direction is calculated. If one line is a character area such as a black character on a white background, it is the sum of absolute values of the difference between the brightness values of white and black, and the value is larger than that of an image area such as a photograph. . This is because in the case of an image region, it is assumed that the difference in luminance value between the front and rear pixels, such as a landscape image, is not so large. In the present embodiment, by using such a tendency, it is possible to distinguish whether or not one target line is a character area (that is, whether it is an image area).

  Here, the background level detection process will be described with reference to FIG. In this embodiment, when it is determined that one line in the main scanning direction that has been read is a character area, a background level detection process for acquiring the sheet original color (recording medium color) of the sheet original is performed. The main CPU 24 acquires the read data for one line in the main scanning direction (S1201). The main CPU 24 determines whether the read value (luminance value) of the target pixel is equal to or higher than the background level threshold value with the leading edge pixel on one line as the target pixel (S1202). If it is determined that the read value of the target pixel is greater than or equal to the background level threshold value, the process proceeds to S1203. If it is determined that the read value is less than the background level threshold value, the process proceeds to S1204. That is, it is determined whether one line is a character or a sheet original color for each line determined as a character area in S1108.

  If it is determined in S1202 that the background level threshold value is exceeded, the read value of the target pixel is added to the cumulative value of the read values for one line (S1203). For example, if the first pixel of one line is the target pixel and it is determined in S1202 that the character is a character, the cumulative value is the read value of the first pixel. If the second pixel from the first pixel is the target pixel and it is determined in S1202 that the character is a character, the read value of the second pixel is added to the first pixel (cumulative value). In S1203, the number of pixels determined to be equal to or higher than the background level threshold value in S1202 is stored in the memory 27 together with the cumulative value. Hereinafter, for the sake of explanation, the cumulative value is Sbg, and the number of pixels determined to be equal to or greater than the background level threshold is m.

  Next, the main CPU 24 determines whether or not the coordinates of the current target pixel are the rear end coordinates Ymax on one line (S1204). If it is determined that the rear end coordinate Ymax is not reached, the coordinate of the target pixel is advanced by “1” along the main scanning direction (S1205). Thereafter, the processing from S1202 is repeated. On the other hand, if it is determined that the rear end coordinates Ymax, h, the main CPU 24 calculates the average value for the number of pixels by dividing the cumulative value Sbg by the number m of pixels, thereby obtaining the sheet original color luminance value. (Background level) Bg is acquired (S1206). The main CPU 24 stores the sheet original color luminance value Bg in the memory 27 and ends the processing of FIG.

  The processing after FIG. 12 will be described again from S1004. If it is determined that one line read in S1004 is a character area, the process proceeds to S1006. If it is determined that the line is not a character area (that is, an image area), the process proceeds to S1005.

  In S1005, the main CPU 24 corrects the pixel value (luminance value) corresponding to the position where dust was detected in S1001 by linear interpolation using surrounding pixel values. The change from the state (1) to the state (2) in FIG. 13 is a diagram illustrating the concept of the correction processing in S1005. The horizontal axis indicates the position in the main scanning direction, and the vertical axis indicates the luminance value. In the state (1), the pixel corresponding to the position where dust is detected is shown as a “black streak pixel”, and the luminance value of the black streak pixel is naturally lower than the surrounding pixel values. If it is determined that the current one line is not a character area, the luminance value of the black streak pixel is a linear interpolation value between the luminance values a and b, as shown in state (2). In this embodiment, the luminance value of the black streak pixel is obtained by linear interpolation, but other methods such as setting the peripheral pixel value as the luminance value of the black streak pixel may be used.

  In S1006, the main CPU 24 replaces the pixel value corresponding to the position where dust was detected in S1001 with the sheet original color luminance value Bg calculated in S1206. The change from the state (1) to the state (3) in FIG. 13 is a diagram illustrating the concept of the correction processing in S1006. When it is determined that the current one line is a character area, as shown in the state (3), the luminance value of the black streak pixel is set to the sheet original color luminance value Bg.

  After correcting the pixel value corresponding to the position where dust is detected in S1005 and S1006, the main CPU 24 determines whether one line currently being processed is the last line read in the reading operation. Determination is made (S1007). If it is determined that the line is not the last line, the process from S1002 is repeated with the next line as the target line. On the other hand, if it is determined that the current line is the final line, the processing in FIG. 10 is terminated.

  As described above, in the present embodiment, the position of dust at the reading position is detected before image reading, and the position corresponding to the position of the dust is set to the surrounding pixel values for the image area in the read data. Interpolate based on. On the other hand, for the character area in the read data, the portion corresponding to the dust position is replaced with the sheet original color luminance value. As a result, it is possible to improve difficulty in reading due to character distortion when linear interpolation is performed based on surrounding pixels in the character region.

  As described with reference to FIG. 10, for the line determined to be a character area in S1004, in S1006, the pixel value corresponding to the position where dust is detected is replaced with the sheet original color luminance value Bg calculated in S1206. . Here, between S1004 and S1006, the number of pixels along the main scanning direction at the position where dust is detected is acquired, and it is determined whether or not the number of pixels is larger than a predetermined value. Also good. If it is determined that the value is larger than the predetermined value, the process of S1006 is performed. In other words, when it is determined that the dust is small, it is assumed that there is no visually uncomfortable feeling even if correction is performed by linear interpolation or the like based on the surrounding pixel values as in the conventional case. On the other hand, if it is determined that the dust is large, the sheet original color luminance value is replaced as described in S1006, assuming that a visually unnatural feeling is caused when correction is performed by linear interpolation or the like as in the prior art.

24 Main CPU
41 Image processing circuit 50 Reading unit 100 Image forming apparatus 103 Image reading apparatus

Claims (7)

A reading device for optically reading a document,
Detecting means for detecting the position of the foreign matter in the reading region;
Determining means for determining whether or not the read data obtained by reading the document is data of a character area;
Data representing the original color obtained from the read data, which corresponds to the position of the foreign matter detected by the detection means in the read data when the determination means determines that the data is the character area data. Correction means for correcting by replacing with,
A reading apparatus comprising:   The correction means corresponds to the position of the foreign matter detected by the detection means in the read data when the number of pixels corresponding to the position of the foreign matter detected by the detection means is larger than a predetermined number of pixels. The reading apparatus according to claim 1, wherein data is corrected by replacing the data with data representing the original color.   Calculating means for calculating, as data representing the original color, an average value of each luminance value equal to or higher than a threshold value among luminance values of each pixel represented by the read data determined to be data of the character area by the determining means; The reading apparatus according to claim 1, further comprising:   The determination unit determines that the read data is data of the character area if the sum of luminance value differences between two adjacent pixels in the reading area is equal to or greater than a threshold value. The reading device according to any one of claims 1 to 3.   When the determination unit determines that the data is not data of the character area, the correction unit adjoins the position corresponding to the position of the foreign object detected by the detection unit in the read data adjacent to the position of the foreign object. The reading apparatus according to claim 1, wherein correction is performed based on a luminance value of a pixel. A correction method executed in a reading device that optically reads a document,
A detecting step in which the detecting means of the reading device detects the position of the foreign matter in the reading region;
A determination step in which the determination unit of the reading apparatus determines whether the read data obtained by reading the document is character area data;
When the correcting unit of the reading apparatus determines that the character area data is in the determining step, the data corresponding to the position of the foreign matter detected by the detecting unit in the read data is converted to the original color. A correction process for correcting by replacing with data to represent,
A correction method characterized by comprising:   The program which makes a computer perform each process of the correction method of Claim 6.

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