JP2005117090A - Image reading apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reading apparatus capable of detecting streaks generated on a read image due to dust adhered on an original reading position on document platen glass, and correcting image data having the generated streaks. <P>SOLUTION: A digital scanner 100 is provided with a scanner controller 301, a streak detecting circuit 305, and a streak correcting circuit 306. Upon receiving an instruction of reading operation in an ADF original reading mode, the scanner controller 301 starts to read an original 102, and the streak detecting circuit 305 determines whether or not streaks are generated due to dust on the read image. If the streaks are generated, the streak correcting circuit 306 performs streak correction for replacing image data having the generated streaks by the other image data. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image reading apparatus, and more particularly to an image reading apparatus having a function of reading image data from a document conveyed by a document conveying device.

  2. Description of the Related Art Conventionally, an image reading apparatus such as a digital copying machine, a scanner, or a facsimile is configured to scan a document conveyed by a document conveyance device (hereinafter referred to as “ADF (auto document feeder)”) that conveys a document by a roller or the like. There is something.

  In this image reading apparatus, an optical table mounted with a lamp and a mirror provided below the ADF is moved to a reading position set in advance by a motor, and a document conveyed at a predetermined speed by a roller between the document table glass and the ADF. The document is scanned with this lamp, and a copy image can be obtained by performing processing in the printer unit based on the scanned data.

  When this optical system fixed / original moving type image reading apparatus is used, if dust adheres to the platen glass at the original reading position, the dust is also read when the original is scanned. A streak in the sub-scanning direction is generated at a position corresponding to dust. When black dust adheres to the platen glass, black streaks appear in the bright portion of the read image as shown in FIG. 22, and when white dust adheres to the platen glass, the read image becomes dark as shown in FIG. White streaks appear in the area.

  If dust adheres to the platen glass, streaks may always occur in the read image until the platen glass is cleaned. In addition, dust is carried to the document reading position on the platen glass together with the conveyed document, and streaks are generated in the middle of the document reading, or dust attached to the document reading position on the platen glass is attached together with the document. In some cases, the streak disappears in the middle of reading the original while being carried from the original reading position.

  As a method for reducing the influence of dust, a technique is known in which a document is read at a position other than the narrowest portion formed by a document pressing means and a document table, on which dust is likely to adhere and stay. Reference 1). However, when this technique is used, the probability of reading dust can be reduced, but once the dust is read, a read image in which streaks are generated is output as it is.

There is also known a method for detecting dust adhering to a document reading position on a platen glass prior to reading a document and changing the document reading position (for example, Patent Document 2). However, when this method is used, dust adhering to the original reading position on the original platen glass can be detected before the original is read, but it adheres to the original reading position on the original platen glass during the original reading. It is impossible to prevent streaks from being generated.
JP 09-093392 A JP 2000-196814 A

  An object of the present invention is to provide an image reading apparatus capable of detecting streaks generated in a read image due to dust adhering to a document reading position on a platen glass and correcting image data in which streaks are generated. .

  In order to achieve the above object, an image reading apparatus according to claim 1 is provided with an original conveying means for conveying an original to an image reading position, and an reading means for reading image data from the conveyed original. In the reading device, correlation determining means for determining whether or not the read image data is correlated with surrounding image data, and when there is no correlation, the non-correlated image data is sub-scanned. Continuity determining means for determining whether or not there is continuity in a direction; and replacement means for replacing the continuous image data with image data different from the continuous image data when there is the continuity. It is characterized by providing.

  The image reading apparatus according to claim 2, wherein the correlation determination unit is configured such that the image data level of the read image data is equal to an image data level of the surrounding image data and a predetermined value. It is characterized in that it is determined that there is no correlation when different from the above.

  The image reading apparatus according to claim 3, wherein the correlation determination unit includes a plurality of the read image data, and the plurality of the read image data are in a sub-scanning direction. It is determined that there is no correlation when the image data level of the attention area adjacent to the image area differs from the image data level of the surrounding area including a plurality of surrounding image data by a predetermined value or more.

  The image reading apparatus according to claim 4 is the image reading apparatus according to claim 3, wherein the correlation determination unit is configured such that an average value of image data levels of the attention area is equal to an average value of image data levels of the surrounding area. It is characterized in that it is determined that there is no correlation when different by more than a value.

  The image reading apparatus according to claim 5 is the image reading apparatus according to claim 3, wherein the correlation determination unit is configured such that a variance value of the image data level of the attention area is equal to a variance value of the image data level of the surrounding area. It is characterized in that it is determined that there is no correlation when different by more than a value.

  6. The image reading apparatus according to claim 1, further comprising main scanning width detecting means for detecting a width of the continuous image data in a main scanning direction, according to any one of claims 1 to 5. The replacement unit is characterized in that the image data having a width in the main scanning direction equal to or smaller than a predetermined value is replaced with image data different from the image data having a width in the main scanning direction equal to or smaller than a predetermined value.

  The image reading device according to claim 7 is the image reading device according to any one of claims 1 to 6, wherein the replacement unit is configured to base the continuous image data on the surrounding image data. It is characterized by replacing with.

  According to the image reading apparatus of claim 1, when image data having no correlation with surrounding image data is continuous in the sub-scanning direction, the continuous image data is converted into the continuous image data. Since the image data is replaced with different image data, it is possible to detect a streak generated in the read image due to dust adhering to the document reading position on the platen glass and correct the image data in which the streak is generated.

  According to the image reading apparatus of the second aspect, since it is determined that there is no correlation when the image data level of the read image data is different from the image data level of the surrounding image data by a predetermined value or more, The streaks generated in the read image due to dust adhering to the original reading position can be detected.

  The image reading apparatus according to claim 3, wherein the plurality of read image data includes a plurality of read image data, and the image data level of a region of interest adjacent in the sub-scanning direction is the surrounding image. Since it is determined that there is no correlation when it differs from the image data level of the surrounding area including a plurality of data by a predetermined value or more, streaks can be detected even in a noisy image or a halftone image.

  According to the image reading apparatus of the fourth aspect, since it is determined that there is no correlation when the average value of the image data level of the attention area differs from the average value of the image data level of the surrounding area by a predetermined value or more, A streak can be detected even in a certain image.

  According to the image reading device of claim 5, since it is determined that there is no correlation when the variance value of the image data level of the attention area differs from the variance value of the image data level of the surrounding area by a predetermined value or more, A streak can be detected also in an image.

  According to the sixth aspect of the present invention, the image data having the width in the main scanning direction of the continuous image data is replaced with the image data different from the image data having the width in the main scanning direction of the predetermined value or less. The streaks generated in the read image due to the dust adhering to the document reading position on the platen glass can be detected, and the image data in which the streaks are generated can be corrected.

  According to the image reading apparatus of the seventh aspect, since the continuous image data is replaced based on the surrounding image data, the image data in which streaks are generated can be corrected.

  Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus according to an embodiment of the present invention.

  In FIG. 1, a digital scanner 100 (image reading apparatus) includes an ADF 101 (original conveying means) and a main body 105 (original reading means) on which the ADF 101 is placed.

  The ADF 101 includes a transport roller 103 that transports the document 102 and a platen roller 104 that presses the transported document 102 onto a document table glass 106 to be described later.

  The main body 105 mounts a platen glass 106 through which the document 102 passes, a lamp 107 that irradiates light on the document surface of the document 102, and a mirror 108 that reflects light reflected from the document 102 and moves to an image reading position. An optical bench 109, an optical bench 112 on which mirrors 110 and 111 for guiding reflected light from the mirror 108 to a lens 116 described later, a motor 114 connected to the optical bench 109 and 112 by a wire 113, and an optical bench 109, a position sensor 115 that indicates the home position of 109, a lens 116 that condenses the reflected light guided by the optical benches 109 and 112, and a CCD 117 that photoelectrically converts the reflected light collected by the lens 116.

  The motor 114 scans the document 102 on the document table glass 106 by moving the optical tables 109 and 112 with the position sensor 115 as a reference by rotating forward or backward. Further, the motor 114 includes an encoder 302 shown in FIG. 2 to be described later, and the encoder 302 outputs an encoder pulse corresponding to the rotational speed of the motor 114. That is, the positions of the optical benches 109 and 112 are grasped by encoder pulses output from the position sensor 115 and the encoder 302, and the optical benches 109 and 112 are moved by the motor 114.

  With the above configuration, the digital scanner 100 places the original 102 conveyed by the ADF 101 on the original table glass 106 and the ADF original reading mode for reading the original 102 by moving the optical tables 109 and 112 to the original reading position of the ADF 101. The original 102 can be read in two modes: an original table glass original reading mode in which the original 102 is read by moving the optical tables 109 and 112 in the sub-scanning direction and scanning.

  As shown in FIG. 2, the digital scanner 100 provided with the ADF 101 easily retains dust 200 in the gap between the platen roller 104 that is the document reading position and the document table glass 106. Since the original 102 is read simultaneously with the reading in the reading mode, streaks occur in the read image.

  FIG. 3 is a block diagram showing an internal configuration of the digital scanner 100 of FIG.

  In FIG. 3, the digital scanner 100 includes a scanner controller 301 that controls the digital scanner 100 and performs a document reading operation.

  The digital scanner 100 also includes a transport roller 103, a platen roller 104, a lamp 107, a motor 114, an encoder 302, and a position sensor 115, which are connected to the scanner controller 301.

  Further, the digital scanner 100 performs A / D conversion with a CCD 117 that photoelectrically converts reflected light from the document surface and outputs a signal, and an A / D conversion circuit 303 that performs A / D conversion on the signal output from the CCD 117. A shading correction circuit 304 that performs shading correction of optical system characteristics such as the CCD 117 and the lens 116 with respect to the output signal, and a streak detection circuit 305 of FIG. 4 to be described later that detects streaks caused by dust from the shading corrected signal. And a streak correction circuit 306 that replaces the detected streak image data with other image data. These are connected in series, and the streak correction circuit 306 is connected to the scanner controller 301.

  A scanner controller 301 controls each component of the digital scanner 100.

  FIG. 4 is a block diagram showing an internal configuration of the streak detection circuit 305 in FIG.

  In FIG. 4, a streak detection circuit 305 includes a correlation comparison unit 401 that compares image data levels of surrounding pixels and a target pixel, a main scanning detection memory 402 that stores a comparison result of the correlation comparison unit 401, and main scanning detection. A continuity detecting unit 403 that detects the continuity of the non-correlated pixels in the sub-scanning direction from the comparison result stored in the memory 402;

  The continuity detection unit 403 detects the presence / absence of a streak from the continuity of the non-correlated pixels in the sub-scanning direction, and the streak detection result “1” indicating the presence of a streak or the streak detection result indicating the absence of a streak A binary flag signal of “0” is transmitted to the line correction circuit 306.

  FIG. 5 is a flowchart of document reading operation processing executed by the digital scanner 100 of FIG.

  In FIG. 5, when a reading operation in the ADF original reading mode is instructed (YES in step S501), the scanner controller 301 moves the optical benches 109 and 112 to the original reading position (step S502), and the lamp 107 is turned on. At the same time, the original 102 is conveyed by the conveying roller 103 to start reading the original 102 (step S503), and the CCD 117 photoelectrically converts the reflected light from the original surface to output a signal, and outputs A / D. The conversion circuit 303 performs A / D conversion on the signal output from the CCD 117.

  Next, the shading correction circuit 304 performs shading correction of the optical system characteristics such as the CCD 117 and the lens 116 on the A / D converted output signal (step S504), and the streak detection circuit 305 determines from the signal subjected to the shading correction. Then, it is determined whether or not a streak due to dust has occurred in the read image (step S505). When a streak occurs, the streak correction circuit 306 performs streak correction to replace the image data in which the streak is generated with other image data. (Step S506) (replacement means) On the other hand, when the streak is not generated, the process is terminated without performing the line correction in step S506.

  According to the processing of FIG. 5, when a streak due to dust occurs in the read image (YES in step S505), the streak correction circuit 306 performs streak correction to replace the streak image data with other image data (step S506). Therefore, streaks generated in the read image due to dust adhering to the original reading position on the platen glass can be detected, and the image data in which the streaks are generated can be corrected.

  FIG. 6 shows white stripe detection processing executed by the stripe detection circuit 305 of FIG.

  In FIG. 6, the streak detection circuit 305 sequentially sets input image data as a target pixel, and determines whether or not the target pixel has a correlation with surrounding pixels (step S601) (correlation detection unit). In step S601, the correlation comparison unit 401 compares the image data levels of the target pixel and the surrounding pixels. If the image data level of the target pixel is brighter than the image data level of the surrounding pixels by a predetermined threshold value, This is done by assuming that the pixel is not correlated with surrounding pixels.

  If the result of determination in step S601 is that the pixel of interest has no correlation with surrounding pixels, the value of the main scanning detection memory 402 corresponding to the main scanning coordinate of the pixel of interest is incremented (step S602), When there is a correlation with the surrounding pixels, the value of the main scanning detection memory 402 corresponding to the main scanning coordinate of the target pixel is cleared (step S603).

  In subsequent step S604, the continuity detecting unit 403 determines whether or not the value of the main scanning detection memory 402 is equal to or greater than a predetermined value α in order to detect continuity in the sub-scanning direction of the non-correlated pixels. (Step S604) (Continuity detecting means) When the value of the main scanning detection memory 402 is equal to or larger than the predetermined value α, it is determined that there is a white streak due to dust or the like in the main scanning coordinate, and the streak detection result “1”. Is transmitted to the streak correction circuit 306 (step S605), and this process ends.

  If the result of determination in step S604 is that the value in the main scanning detection memory 402 is not equal to or greater than the predetermined value α, it is determined that there are no white streaks in this main scanning coordinate, and the streak detection result “0” is transmitted to the correction circuit 306. (Step S606), the process is terminated.

  According to the processing of FIG. 6, when the value of the main scanning detection memory 402 incremented when the target pixel has no correlation with the surrounding pixels is equal to or greater than the predetermined value α (YES in step S604), the streak detection result Since “1” is transmitted to the streak correction circuit 306 (step S605), it is possible to detect streaks generated in the read image due to dust adhering to the document reading position on the platen glass.

  In the processing of FIG. 6, the white stripe detection process has been described. In step S <b> 601, the black stripe detection process compares the image data levels of the target pixel and the surrounding pixels, and the image data level of the target pixel is the image data of the surrounding pixels. When darker than the level by a predetermined threshold or more, the point of interest is different from the white line detection process in that the pixel of interest has no correlation with surrounding pixels.

  FIG. 7 is a flowchart of the correlation comparison process executed by the correlation comparison unit 401 in FIG.

  In FIG. 7, the correlation comparison unit 401 compares the target pixel with the neighboring pixel on the left side of the target pixel, and determines whether the target pixel has a correlation with the neighboring pixel on the left side. (Step S701). At this time, for example, if the pixel b is the target pixel in FIG.

  As a result of the determination in step S701, when the target pixel has no correlation with the surrounding pixel on the left side, the pixel on the right side of the current target pixel is newly set as the target pixel (step S702), and the process returns to step S701. The new pixel of interest is compared with the surrounding pixels adjacent to the left of the first pixel of interest to determine whether there is a correlation. For example, in FIG. 8, the pixel c that is the new target pixel is compared with the pixel a that is the surrounding pixel on the left side of the first target pixel.

  When the new pixel of interest is compared with the surrounding pixel adjacent to the left of the first pixel of interest instead of the surrounding pixel adjacent to the left of the first pixel of interest, it is not possible to detect a stripe whose width in the main scanning direction extends over a plurality of pixels. . For example, in FIG. 8, when the pixel c, which is the new pixel of interest, is compared with the pixel b, which is the neighboring pixel to the left of the new pixel of interest, there is a correlation between them, so that they cannot be detected as streaks.

  The processes in steps S701 to S702 are repeated until it is determined in step S701 that there is a correlation.

  As a result of the determination in step S701, when the target pixel has a correlation with the surrounding pixel on the left side of the first target pixel, the pixel on the left side of the target pixel determined to have a correlation has a correlation. (Step S703), and if the pixel adjacent to the left of the pixel of interest has a correlation, the value of the main scanning detection memory 402 of the pixel of interest is cleared (Step S704), and this process ends. .

  As a result of the determination in step S703, when the pixel on the left side of the target pixel has no correlation, the pixels determined to have no correlation in step S701 are compared with the surrounding pixels on the left and right of those pixels, and the correlation It is determined whether or not the pixel determined to be absent has a correlation with the left and right surrounding pixels (step S705). For example, in FIG. 8, from pixel b and pixel c, which are determined to have no correlation to pixel a, from pixel a to the left of pixels b and c, and from pixel d, which are the surrounding pixels on the left and right of pixels b and c. Each pixel is compared with the right pixel. Here, the range of the left and right surrounding pixels to be compared is set in advance.

  If the pixel determined to have no correlation as a result of the determination in step S705 is correlated with any one of the left and right surrounding pixels, the main scanning detection memory 402 of the pixel determined to have no correlation. Is cleared (step S704), and when the pixel determined to be uncorrelated has no correlation with all the left and right surrounding pixels, the value of the pixel determined to be uncorrelated is stored in the main scanning detection memory 402. Is incremented (step S706), and this process ends.

  According to the processing of FIG. 7, when the pixel determined to have no correlation in step S701 is not correlated with all the left and right surrounding pixels (NO in step S705), the pixel determined to have no correlation is determined. Since the value in the main scanning detection memory 402 is incremented (step S706), it is possible to detect streaks generated in the read image due to dust adhering to the original reading position on the original table glass.

  An example of the operation of the main scanning detection memory 402 is shown in FIG. In the operation example of FIG. 11, for example, white streak detection is performed on the image shown in FIG. 9, and the range of surrounding pixels as a comparison reference is 2 pixels left and right in the main scanning direction and 5 pixels in the sub-scanning direction as shown in FIG. 10. It is a thing when set to.

  FIG. 11 shows values in the main scanning detection memory 402 at each main scanning position of each sub-scanning line corresponding to the image in FIG. The white stripe on the right side of FIG. 9 has no correlated pixel in the range shown in FIG. 10, so the value of the main scanning detection memory 402 is incremented as shown in FIG. On the other hand, the letter C shown in white on the left side of FIG. 9 is determined to have no correlation because there is a correlated pixel in the range shown in FIG. 10, and as shown in FIG. The value of is not incremented.

  FIG. 12 is a flowchart of the line correction process executed by the line correction circuit 306 in FIG.

  In FIG. 12, the streak correction circuit 306 receives a streak detection result “1” (YES in step S121), and when the streak width is equal to or smaller than a predetermined value (YES in step S122) (main scanning width detecting means), Image data is replaced from the sub-scanning line traced back α (predetermined value in step S604 in FIG. 6) at the main scanning position where the streak is detected (step S123), and this process is terminated.

  The replacement of the image data in step S123 is to replace the image data at the main scanning position where the streak is detected with the linear interpolation value of each image data at each main scanning position adjacent to the left and right of the main scanning position where the streak is detected. To do.

  For example, the image data at the main scanning position f where the streak is detected in FIG. 13A is the main scanning position e adjacent to the left and right of the main scanning position where the streak is detected as shown in FIG. It is replaced by the linear interpolation value of each image data of g.

  According to the processing of FIG. 12, the streak correction circuit 306 receives the streak detection result “1” (YES in step S121), and when the streak width is equal to or smaller than the predetermined value (YES in step S122), the image data Since the replacement is performed (step S123), it is possible to detect the streak generated in the read image due to the dust adhering to the document reading position on the platen glass, and to correct the image data in which the streak is generated.

  FIG. 14 shows another white line detection process executed by the line detection circuit 305 of FIG.

  In FIG. 14, the same steps as those in FIG. 6 are denoted by the same reference numerals, and the description thereof is omitted.

  In FIG. 14, the streak detection circuit 305 sequentially sets input image data as a target pixel, and as illustrated in FIG. 15, the target pixel and a plurality of pixels adjacent to the target pixel in the sub-scanning direction are used as a target region. The average value of the image data level of each pixel is calculated (step S141).

  Next, as shown in FIG. 16, the average value of the image data level of each pixel in the surrounding area is calculated using a plurality of neighboring pixels adjacent to each other as the surrounding area. It is determined whether or not there is a correlation (step S142). In step S142, the correlation comparison unit 401 compares the average value of the surrounding area and the average value of the attention area. If the average value of the attention area is brighter than the average value of the surrounding area by a predetermined threshold or more, the correlation is obtained. It is done by assuming that there is no.

  As a result of the determination in step S142, when the average value of the attention area has no correlation with the average value of the surrounding area, the value of the main scanning detection memory 402 corresponding to the main scanning coordinate of the attention area is incremented (step S142). S602) When the average value of the attention area is correlated with the average value of the surrounding area, the value of the main scanning detection memory 402 corresponding to the main scanning coordinate of the attention area is cleared (step S603), The processing after S604 is executed, and this processing is terminated.

  According to the processing of FIG. 14, when the average value of the attention area is not correlated with the average value of the surrounding area (NO in step S142), the main scanning detection memory 402 corresponding to the main scanning coordinate of the attention area. Is incremented (step S602), and therefore streaks can be detected even in a noisy image as shown in FIG.

  FIG. 18 shows an operation example of the main scanning detection memory 402 when white streak detection is performed on the noisy image shown in FIG. In FIG. 17, pixels having correlation with surrounding pixels exist on the white stripe, but the average value of the image data of the white stripe target area is brighter than the average value of the image data of the surrounding area. As shown in FIG. 18, the value of the main scanning detection memory 402 corresponding to the white stripe is incremented.

  FIG. 19 shows still another white stripe detection process executed by the stripe detection circuit 305 of FIG.

  In FIG. 19, steps that are the same as the steps in FIG. 6 are given the same reference numerals, and descriptions thereof will be omitted.

  In FIG. 19, the streak detection circuit 305 sequentially sets input image data as a pixel of interest, and sets a plurality of pixels adjacent to the pixel of interest in the sub-scanning direction as shown in FIG. A variance value at the image data level is calculated (step S191).

  Next, as shown in FIG. 16, a plurality of surrounding pixels adjacent to each other are used as the surrounding area, and a variance value of the image data level of each pixel in the surrounding area is calculated. It is determined whether or not there is a correlation (step S192). In step S192, the correlation comparison unit 401 compares the variance value of the surrounding area with the variance value of the attention area, and if the variance value of the attention area is smaller than the variance value of the surrounding area by a predetermined threshold or more, the correlation It is done by assuming that there is no.

  As a result of the determination in step S192, when the variance value of the attention area has no correlation with the dispersion area of the surrounding area, the value of the main scanning detection memory 402 corresponding to the main scanning coordinate of the attention area is incremented (step S192). S602) When there is a correlation between the variance values of the region of interest, the value of the main scanning detection memory 402 corresponding to the main scanning coordinate of the region of interest is cleared (step S603), and the processing after step S604 is executed. This process is terminated.

  According to the processing of FIG. 19, when the variance value of the attention area has no correlation with the dispersion value of the surrounding area (NO in step S192), the main scanning detection memory 402 corresponding to the main scanning coordinate of the attention area. Is incremented (step S602), so streaks can be detected even in a halftone image as shown in FIG.

  FIG. 21 shows an operation example of the main scanning detection memory 402 when white stripe detection is performed on the halftone image shown in FIG. In FIG. 20, the halftone dot image has pixels that are correlated with white streak pixels, but the variance value of the image data of the white stripe target region is compared with the variance value of the image data of the surrounding region. Therefore, as shown in FIG. 21, the value of the main scanning detection memory 402 corresponding to the white stripe is incremented.

1 is a diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. It is a figure which shows a part of digital scanner 100 of FIG. FIG. 2 is a block diagram showing an internal configuration of the digital scanner 100 of FIG. 1. FIG. 4 is a block diagram showing an internal configuration of a streak detection circuit 305 in FIG. 3. 3 is a flowchart of document reading operation processing executed by the digital scanner 100 of FIG. 1. This is white line detection processing executed by the line detection circuit 305 of FIG. It is a flowchart of the correlation comparison process performed by the correlation comparison part 401 in FIG. It is a figure which shows an example of the image read by the digital scanner 100 of FIG. It is a figure which shows an example of the image read by the digital scanner 100 of FIG. It is a figure which shows an example of the range of the surrounding pixel used for correlation detection by step S705 of FIG. FIG. 5 is a diagram illustrating an operation example of a main scanning detection memory 402 in FIG. 4. 4 is a flowchart of a line correction process executed by the line correction circuit 306 in FIG. 3. FIG. 5 is a diagram illustrating an operation example of the main scanning detection memory 402 in FIG. 4, where (a) is before replacement of image data, and (b) is after replacement of image data. This is another white streak detection process executed by the streak detection circuit 305 of FIG. It is a figure which shows an example of the attention area | region used by step S141 of FIG. It is a figure which shows an example of the surrounding area | region used by step S142 of FIG. It is a figure which shows an example of the image read by the digital scanner 100 of FIG. FIG. 5 is a diagram illustrating an operation example of a main scanning detection memory 402 in FIG. 4. This is still another white line detection process executed by the line detection circuit 305 of FIG. It is a figure which shows an example of the image read by the digital scanner 100 of FIG. FIG. 5 is a diagram illustrating an operation example of a main scanning detection memory 402 in FIG. 4. It is a figure which shows an example of the black stripe which generate | occur | produces with the conventional image reading apparatus. It is a figure which shows an example of the white stripe which generate | occur | produces with the conventional image reading apparatus.

Explanation of symbols

100 digital scanner 101 ADF
102 Document 301 Scanner Controller 305 Line Detection Circuit 306 Line Correction Circuit

Claims (7)

In an image reading apparatus comprising a document conveying means for conveying a document to an image reading position and a reading means for reading image data from the conveyed document,
Correlation determining means for determining whether or not the read image data is correlated with surrounding image data; and when there is no correlation, the non-correlated image data is continuous in the sub-scanning direction. Continuity determining means for determining whether or not there is, and, when there is continuity, replacement means for replacing the continuous image data with image data different from the continuous image data. A characteristic image reading apparatus.   The correlation determining unit determines that there is no correlation when an image data level of the read image data is different from an image data level of the surrounding image data by a predetermined value or more. The image reading apparatus described.   The correlation determination unit includes a plurality of the read image data, and the plurality of read image data includes an image data level of a region of interest adjacent in the sub-scanning direction. 2. The image reading apparatus according to claim 1, wherein it is determined that the correlation does not exist when the image data level differs from a surrounding area by a predetermined value or more.   The correlation determining means determines that there is no correlation when an average value of image data levels of the region of interest differs from an average value of image data levels of the surrounding region by a predetermined value or more. Item 4. The image reading apparatus according to Item 3.   The correlation determining means determines that there is no correlation when a variance value of the image data level of the region of interest differs from a variance value of the image data level of the surrounding region by a predetermined value or more. Item 4. The image reading device according to Item 3.   Main scanning width detecting means for detecting the width of the continuous image data in the main scanning direction; and the replacing means detects image data whose width in the main scanning direction is a predetermined value or less. 6. The image reading apparatus according to claim 1, wherein the image data is replaced with image data different from image data equal to or less than a predetermined value.   The image reading apparatus according to claim 1, wherein the replacement unit replaces the continuous image data based on the surrounding image data.

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