JP2008028698A - Image reading apparatus and image reading method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reading apparatus and an image reading method capable of decreasing the occurrence of misjudgment wherein a stripe image to be discriminated as an image of an original is discriminated as a stripe abnormity image. <P>SOLUTION: The image reading apparatus SC wherein an image of an original S carried on one principal side of a contact glass 27 moved in a subscanning direction is read from the other principal side of the contact glass 27 by reflected light of an exposure lamp 26 includes: a reference board 10 arranged opposed to one principal side of the contact glass 27 and extended in a main scanning direction; an abnormity discrimination section that discriminates whether or not abnormity exists in an image resulting from reading the original S on the basis of a highest density in the image of a prescribed region of the original S and a highest density in an image resulting from reading the reference board 10 in a state that the original S does not exists on the one principal side of the contact glass 27; and a read position setting section that revises an original read position P of the original S along the subscanning direction within a range readable of the reference board 10 when the presence of abnormity is discriminated. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a so-called sheet-through type image reading apparatus and image reading device that reads an image of a document from the other main surface side of the transparent plate while conveying the document to be read so as to move on one main surface of the transparent plate. Regarding the method.

  When an image of a document is read using a sheet-through type image reading device and printed by a printer, or when an image is captured on a computer such as a personal computer and displayed on a display, the image is displayed in the sub-scanning direction. A line-like abnormal image may appear. This is usually caused by foreign matters such as dust, dust, or paper dust of the conveyed original paper adhering to the contact glass of the image reading apparatus or scratches on the contact glass. A streak-like abnormal image appears as a black streak on the background portion, which is a white background portion, or appears as a white streak in the image portion, and is visually conspicuous. For an image reading apparatus that desires to obtain image data faithful to a document, it is desired to eliminate such streak abnormal images.

  For example, Patent Literature 1 and Patent Literature 2 disclose techniques for suppressing the occurrence of such streaky abnormal images.

  The technique disclosed in Patent Document 1 reads a reference plate arranged so as to extend in the main scanning direction at a document reading position before reading a document, and does the obtained image of the reference plate include an abnormal image? If an abnormal image is included, the document reading position is moved by a predetermined distance along the sub-scanning direction. If an abnormal image is recognized again at a new document reading position, the document reading position is further changed. The technique disclosed in Patent Document 1 suppresses the appearance of a streaky abnormal image in an image of a document read in this way.

  In the technique disclosed in Patent Document 2, first, a document is read, and it is determined whether or not the final line of the document includes an image within a predetermined width and having a predetermined density or more. Is done. Secondly, when this determination includes such an image, the reference plate is read, and it is determined whether or not the image of the reference plate at the position of the image has a predetermined density or more. Third, if the image has a predetermined density or higher by this determination, it is determined whether or not the average density of the images on both sides of the position is higher than the predetermined density. Then, when it is determined by this determination that the average density is equal to or higher than a predetermined density, it is determined that the image is an abnormal image. If an abnormal image is recognized again at a new document reading position, the document reading position is further changed.

  Furthermore, in the technique disclosed in Patent Document 2, first, the original is read, and whether the difference between the highest density position on the first line of the original and the highest density position on the last line of the original is within a predetermined width. It is determined whether or not. Secondly, if the difference is within a predetermined width by this determination, it is determined whether or not the highest density in the final line is equal to or higher than the predetermined density. Thirdly, if the maximum density is equal to or higher than the predetermined density by this determination, the reference plate is read, and it is determined whether or not the maximum density of the reference plate is equal to or higher than the predetermined density. Fourth, if this determination shows that the maximum density is equal to or higher than a predetermined density, is the difference between the highest density position in the last line read in the first and the highest density position of the reference plate within a predetermined width? It is determined whether or not. Then, when it is determined that it is within the predetermined width, it is determined that there is an abnormal image at the highest density position. If an abnormal image is recognized again at a new document reading position, the document reading position is further changed.

  The technique disclosed in Patent Document 2 sequentially determines in this manner, thereby determining foreign matter attached to a reference plate that does not become an abnormal image in actual image data, scratches on the reference plate, etc., and foreign matter attached to the contact glass. And the accuracy of judgments such as scratches on contact glass are improved.

Each time an abnormal image is recognized in this way, the document reading position is sequentially changed from the preset first document reading position to the last document reading position. This document reading position is changed to the last document reading position. When the position is reached, the order is changed in the reverse order (from the preset last document reading position to the first document reading position), and at that time, the user is warned that it is time for maintenance. 2 discloses it.
JP 2000-196814 A JP 2000-310820 A

  By the way, in each of the technologies disclosed in Patent Document 1 and Patent Document 2 described above, if a document has a streak image along a conveyance direction (sub-scanning method) such as a ruled line, the document is determined to be an image of the document. In some cases, the streak-like image is erroneously determined as a streak-like abnormal image.

  The present invention has been made in view of the above-described circumstances, and can reduce an erroneous determination in which a streak image to be determined to be an image of a document is determined as a streak abnormal image. An object is to provide a reading apparatus and an image reading method.

  As a result of various studies, the present inventor has found that the above object is achieved by the present invention described below. That is, in one aspect according to the present invention, an image of a document conveyed so as to move in the sub-scanning direction on one main surface of the transparent plate is read from the other main surface side of the transparent plate by reflected light of the light source. In the reading device, a reference plate that is disposed to face one main surface of the transparent plate and extends in the main scanning direction, a maximum density in an image of a preset region of the original, and the original is the transparent An abnormality determination unit for determining whether or not the image read from the original is abnormal based on the highest density in the image read from the reference plate in a state of not being on one main surface of the plate; and the abnormality determination And a reading position setting unit that changes the reading position of the document along the sub-scanning direction within a range in which the reference plate can be read when it is determined that there is an abnormality. In another aspect of the present invention, the image of the document conveyed so as to move in the sub-scanning direction on one main surface of the transparent plate is reflected from the other main surface side of the transparent plate by the reflected light of the light source. In the image reading method for reading, the step of obtaining the highest density in the image of the preset region of the original, and the original on the one main surface of the transparent plate in a state where the original is not on the one main surface of the transparent plate. Acquiring a maximum density in an image obtained by reading a reference plate arranged oppositely and extending in the main scanning direction; a maximum density in an image of a preset region of the document; and the document is the transparent plate Determining whether there is an abnormality in the image read from the original based on the highest density in the image read from the reference plate in a state where it is not on one main surface of Case Characterized by comprising a step of changing the read position of the document within the range that can be read the reference plate along the sub-scanning direction.

  According to such a configuration, the abnormality determination unit determines the highest density in the image of the preset region of the document and the highest density in the image read from the reference plate in a state where the document is not on one main surface of the transparent plate. Since it is determined based on the density whether there is an abnormality in the image read from the document, there is an erroneous determination in which a streak image to be determined as an image of the document is determined as a streak abnormal image. Can be reduced.

  In addition, regarding the above-described image reading, the image of the preset region of the document is a region having a preset width in the sub-scanning direction extending in the main scanning direction at the leading end in the document transport direction. And a second image of a region having a width preset in the sub-scanning direction extending in the main scanning direction at the rear end portion in the document transport direction, and the document is the transparent image The image obtained by reading the reference plate without being on one main surface of the plate is a third image obtained by reading the reference plate with the width without the original being on one main surface of the transparent plate. Features.

  According to such a configuration, since the abnormality determination unit determines whether or not there is an abnormality in the image read from the document by using the first to third images, the abnormality image can be determined in a shorter time. it can.

  Further, regarding the above-described image reading, the abnormality determination unit determines whether each of the highest densities in the first and second images is equal to or higher than a first predetermined value, and It is determined whether the absolute value of the difference between the highest density position in one image and the highest density position in the second image is equal to or smaller than a second predetermined value set in advance, and in the third image It is determined whether or not the maximum density is equal to or higher than a third predetermined value, and an absolute value of a difference between the highest density position in the first or second image and the highest density position in the third image is set in advance. Whether the difference between the highest density in the first image or the second image and the highest density in the third image is set in advance. By determining whether or not the value is less than or equal to the value, And judging whether or not there is an abnormality in the read image.

  According to such a configuration, first, it is determined whether or not there is a streak image along the transport direction (sub-scanning method). Then, it is determined whether the streak image is an original image or an abnormal image. For this reason, an image of an original and an abnormal image can be more reliably distinguished.

  In the image reading apparatus and the image reading method configured as described above, it is possible to reduce erroneous determinations that determine a streak image to be determined as an image of a document as a streak abnormal image.

  Embodiments according to the present invention will be described below with reference to the drawings. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted.

  1 and 2 are schematic sectional views mainly showing mechanical and optical configurations of the image reading apparatus according to the embodiment. FIG. 2 corresponds to a partially enlarged view of FIG. FIG. 3 is a block diagram mainly illustrating an electrical configuration of the image reading apparatus according to the embodiment.

  The image reading device SC reflects an image of the document S conveyed so as to move in the sub-scanning direction on one main surface of a contact glass 27 which is an example of a transparent plate, and is reflected by an exposure lamp 26 which is an example of a light source. Is realized as a digital copying machine including not only an image reading function for reading from the other main surface side of the contact glass 27, that is, a scanner function, but also a printer function. The image reading device SC includes a paper feeding unit (document feeder) 1, a scanner unit 2, and a control unit 3.

  The paper feeding unit 1 conveys the document S to a document reading position P that is a position for reading the document. The paper feeding unit 1 is attached to the upper surface of the scanner unit 2 so as to be openable and closable. For example, as shown in FIGS. 1 and 2, a reference plate 10, a document discharge table 11, a document feed table 12, A roller 13, a registration switch 14, a pair of registration rollers 15, a timing switch 16, a separation roller 17, a pair of paper discharge rollers 18 and a document pressing member 19 are provided. The scanner unit 2 reads an image of the document S conveyed to the document reading position P. For example, as shown in FIGS. 1 and 2, the scanner unit 2 includes a first mirror 21, a second mirror 22, a third mirror 23, a lens system 24, a CCD imaging device 25, an exposure lamp 26, and a contact glass 27. . The control unit 3 is provided inside the image reading device SC (inside the digital copying machine), and controls the paper feeding unit 1 and the scanner unit 2 according to the function. The control unit 3 is, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory) or an EEPROM (Electrically Erasable Programmable Read Only Memory) that stores various programs executed by the CPU and data necessary for the execution in advance. The microcomputer includes a RAM (Random Access Memory) serving as a so-called working memory of the CPU and a peripheral circuit thereof.

  Under the control of the control unit 3, a pair of paper feed rollers 13 and a separation roller 17 separate a single document S in order from a plurality of documents S placed on the document feed table 12. The registration roller 15 conveys the document to the document reading position P set between the reference plate 10 of the document pressing member 19 and the contact glass 27. The registration switch 14 and the registration roller 15 serve to regulate the front end of the document by regulating the oblique feeding of the document S before the document S is conveyed to the document reading position P. The reference plate 10 is a belt-like plate attached to the surface of the document pressing member 19 facing the contact glass 27 so as to extend in the main scanning direction (direction orthogonal to the paper surface in FIGS. 1 and 2). Yes, at least the surface facing the contact glass 27 is white, for example. The timing switch 16 determines the leading edge timing of the image during document conveyance, and a signal obtained from the timing switch 16 is notified to the control unit 3.

  While the document S moves at the document reading position P, an image on the side of the document S facing the contact glass 27 is read by the optical system provided in the scanner unit 2. That is, first, the exposure lamp 26 emits light according to the control of the control unit 3, and the light of the exposure lamp 26 passes through the contact glass 27 to irradiate the document reading position P. As a result, the reflected light of the document S at the document reading position P enters the first mirror 21 through the contact glass 27. The incident light passes through the second mirror 22, the third mirror 23, and the lens system 24 and then enters the CCD image sensor 25. The CCD image sensor 25 operates under the control of the control unit 3 and converts incident light into an electrical signal. The CCD image pickup devices 25 are arranged in the main scanning direction, and simultaneously acquire image data for one line in the main scanning direction. The CCD image pickup device 25 may be arranged in a plurality of rows so that image data for a plurality of lines can be acquired simultaneously. The image data acquired by the CCD image sensor 25 is amplified and converted into a digital signal by a processing circuit (not shown), and further subjected to shading correction, gamma correction, chromatic aberration correction, MTF (Modulation Transfer Function) correction, scanner color correction, and the like. Various image processing is performed by the control unit 3. Then, the image data subjected to the image processing is stored in a predetermined memory area in the memory of the control unit 3.

  The document S that has passed the document reading position P is discharged to the document discharge table 11 by the pair of discharge rollers 18 under the control of the control unit 3. While the CCD image pickup device 25 reads the image of the document S at the document reading position P, the document S moves in the sub-scanning direction (horizontal direction in FIGS. 1 and 2), so that one document S is ejected from the document. When stored in the table 11, reading of all images along the main scanning direction and the sub-scanning direction of the single document S is completed.

  Here, the scanner unit 2 opens the paper feeding unit 1 above the scanner unit 2, and the originals S are placed one by one on the upper surface of the contact glass 27 without using the paper feeding unit 1. The image of the document S can also be read. For this purpose, a part of the optical system is attached to the moving frame 28 and configured to be movable along the main surface of the contact glass 27. That is, the exposure lamp 26, the first mirror 21, the second mirror 22, and the third mirror 23 are attached to the moving frame 28, and move as the moving frame 28 moves. On the other hand, the lens system 24 and the CCD image sensor 25 are not attached to the moving frame 28 but are fixed to the portion of the scanner unit 2 excluding the moving frame 28. As the moving frame 28 moves, the second mirror 22 and the third mirror 23 move only half of the moving distance of the exposure lamp 26 and the first mirror 21. Thereby, the length of the optical path of the reflected light of the exposure lamp 26 from the first mirror 21 to the lens system 24 is kept constant without depending on the position of the moving frame 28. As the exposure lamp 26 and the first mirror 21 move, the document reading position moves along the sub-scanning direction. Thereby, the CCD image pickup device 25 can read the image of the document S placed stationary on the upper surface of the contact glass 27 along the main scanning direction and the sub-scanning direction.

  As shown in FIG. 2, even when the document S is conveyed by the paper feeding unit 1 and the image is read through the contact glass 27, the moving frame 28 can be moved, and thus the contact glass 27 can be moved. The document reading position P can be changed along the upper surface of the contact glass 27. Such a configuration can be easily realized by diverting the configuration having the moving frame 28 so that the scanner unit 2 can also read the image of the document S placed on the upper surface of the contact glass 27.

  In order to perform such an image reading operation, for example, as shown in FIG. 3, the scanner unit 2 drives the moving frame 28 by driving a motor (not shown) according to the control of the control unit 3. The control unit 3 functionally includes a reading control unit 31, an abnormality determination unit 32, a reading position setting unit 33, an image data storage unit 34, and a setting data storage unit. 35 and a document reading position movement number storage unit 36.

  The reading control unit 31 controls the paper feeding unit 1 and the scanner unit 2 as described above in order to read the image of the document S. The abnormality determination unit 32 sets the highest density in the image of the preset region of the document S and the highest density in the image read from the reference plate 10 with the document S not on one main surface of the contact glass 27. Based on this, it is determined whether or not there is an abnormality in the image read from the document S. When the abnormality determination unit 32 determines that there is an abnormality, the reading position setting unit 33 controls the moving frame driving unit 29 to set the document reading position P along the sub-scanning direction within a range where the reference plate 10 can be read. The document reading position P is set to a new position. The image data storage unit 34 stores the image data read from the document S by the reading control unit 31. The setting data storage unit 35 stores setting data for moving the document reading position P to each position. In the present embodiment, the setting data is, for example, the movement distance of the document reading position P to each position and the timing at which reading of the document S at each position is started (document reading start timing). The document reading position movement number storage unit 36 stores a value of the document reading position movement number N that represents the number of movements from the initial position at the current document reading position P.

  Next, the abnormality determination operation of the image reading device SC will be described.

  4 and 5 are flowcharts showing an abnormality determination operation in the image reading apparatus according to the embodiment. FIG. 6 is a diagram for explaining a document reading area.

  4 and 5, in the abnormality determination in the image reading device SC, first, the reading control unit 31 of the control unit 3 performs initial setting according to the paper size (S31). As will be described later, as shown in FIG. 6, the abnormality determination is a front end portion in the transport direction of the document S and an area having a predetermined width preset in the sub-scanning direction extending in the main scanning direction (hereinafter, The read image data (hereinafter referred to as “line A image data”) and the trailing edge of the document S in the transport direction and extending in the main scanning direction. Using the read image data (hereinafter referred to as “line B image data”), an area having a predetermined width preset in the sub-scanning direction (hereinafter referred to as “line B”) is used. Is called. For this reason, in this initial setting, more specifically, the positions of the line A and the line B are set according to the paper size. One line usually has a distance corresponding to about 2 mm in the sub-scanning direction, and one or a plurality of lines are appropriately set as the predetermined width of the line A and the line B when performing abnormality determination.

  Next, as described above, the reading control unit 31 reads the image of the document S by operating the paper feeding unit 1 and the scanner unit 2 in cooperation with each other, and stores the image data in a predetermined storage area in the image data storage unit 34. One line is stored (S32). Then, the reading control unit 31 notifies the abnormality determination unit 32 that the reading of the image of the document S has been completed.

  Next, the abnormality determination unit 32 of the control unit 3 determines the highest density that is the highest in the entire main scanning direction in the image of line A from the image data of line A stored in the image data storage unit 34. The highest density and the position of the highest density (maximum density position) are obtained, and the density is highest in the main scanning direction in the image of line B from the image data of line B stored in the image data storage unit 34. The highest density is determined and the highest density and the highest density position are acquired (S33). The position of the highest density is a pixel position in the main scanning direction in the CCD image pickup device 25, and is a memory address in the image data storage unit 34.

  Next, the abnormality determination unit 32 determines whether the highest density of the line A acquired in the process S33 is equal to or higher than the first predetermined density D1, and whether the highest density of the line B acquired in the process S33 is equal to or higher than the first predetermined density D1. No, in other words, it is determined whether or not the highest densities in the lines A and B acquired in step S33 are both equal to or higher than the first predetermined density D1 (S34).

  When the maximum density of line A and the maximum density of line B are low, it is considered that the image is not a streak image such as a ruled line or an abnormal image. For this reason, the first predetermined density D1 is appropriately set according to the density of the streak image such as a ruled line and the streak to be determined as an abnormal image, which are set in advance according to the specification or the like. The first predetermined value D1 is set to a relatively small value, and is set to 32, for example, in the case of 256 gradations where white is 0 and black is 255.

  If the highest density in at least one line (both or any one of the lines) is not equal to or higher than the first predetermined density D1 (No) as a result of the determination in step S34, the abnormality determination unit 32 determines the streaky abnormal image. Is determined not to be detected, and the abnormality determination operation is terminated. On the other hand, as a result of the determination in the process S34, when each maximum density in both lines is equal to or higher than the first predetermined density D1 (Yes), the abnormality determination unit 32 executes the next process S35.

  In the process S35, the abnormality determination unit 32 determines the difference between the position most recently determined as a streak abnormal image and the highest density position of the line A as a result of the previous abnormality determination operation (operations in the processes S31 to S41). It is determined whether the absolute value of is less than or equal to the first predetermined width W1. In other words, the abnormality determination unit 32 first determines that the position that has been determined to be a streak abnormal image and the highest density position of the line A as a result of the previous abnormality determination operation (operations S31 to S41) are first predetermined. It is determined whether or not they match within a range of width W1 or less. The first predetermined width W1 is appropriately set according to the width of a line to be determined as an abnormal image, which is set in advance according to specifications or the like, and is set to 0x10 = 16 pixels, for example. One pixel (one pixel) is usually about 43.3 μm. Here, in the process S35, the position determined as the latest streaky abnormal image is compared with the highest density position of the line A in the above description, but may be compared with the highest density position of the line B.

  If the result of determination in step S35 is that the absolute value of this difference is not less than or equal to the first predetermined width W1 (No), the abnormality determination unit 32 skips step S36 and the reading control unit 31 of the control unit 3 Then, process S37 is executed. On the other hand, if the absolute value of the difference is equal to or smaller than the first predetermined width W1 (Yes) as a result of the determination in the process S35, the abnormality determination unit 32 executes the process S36 and determines the control unit according to the determination result. The reading control unit 31 of No. 3 executes processing S37.

  Here, if the absolute value of the difference is not less than or equal to the first predetermined width W1 as a result of the determination in the process S35, the contact glass 27 is scratched or foreign matter or the like is attached on the contact glass 27. In such a case, the process S36 is skipped.

  In process S36, the abnormality determination unit 32 determines whether or not the absolute value of the difference between the highest density position of line A and the highest density position of line B is equal to or smaller than the second predetermined width W2. The second predetermined width W2 is appropriately set according to the width of a line to be determined as a streak image such as a ruled line, which is set in advance according to specifications, for example, 0x10 = 16 pixels or the like. .

  When the absolute value of this difference is not less than or equal to the second predetermined width W2, it is considered that the image to be determined is not a streak image along the sub-scanning direction but a spot-like image. On the other hand, when the absolute value of the difference is equal to or smaller than the second predetermined width W2, the image to be determined is considered to be a streak image such as a ruled line or an abnormal image such as a black streak.

  For this reason, when the absolute value of this difference is not less than or equal to the second predetermined width W2 (No) as a result of the determination in the process S36, the abnormality determination unit 32 determines that a streak abnormal image has not been detected, and this The abnormality determination operation ends. On the other hand, when the absolute value of the difference is equal to or smaller than the second predetermined width W2 as a result of this determination (Yes), the abnormality determination unit 32 determines whether or not the determination target image is an abnormal image. In order to cause the reading control unit 31 of the control unit 3 to execute the next process S37, the reading control unit 31 is notified of this.

  In the above description, two lines A and B are used from the viewpoint of shortening the determination time. However, three or more lines or all lines in the transport direction may be used.

  In process S37, the reading control unit 31 reads one or a plurality of lines in a state where there is no document S between the contact glass 27 and the reference plate 10, and the obtained image data is stored in a predetermined amount in the image data storage unit 34. Store in the storage area. Then, the reading control unit 31 notifies the abnormality determination unit 32 that the reading of the image without the document S has been completed. Here, the number of lines read in this case is appropriately set to the minimum number of lines necessary for determining an abnormal image. However, when a large number of lines are read, the image data storage unit 34 needs a storage capacity corresponding to the number of lines read. Therefore, the smaller one is more preferable. In this case, the number of lines read is the same as the number of lines A, for example.

  Next, the abnormality determination unit 32 determines the highest density that is the highest in the entire main scanning direction in the image of the line from the image data of the line read without the document S stored in the image data storage unit 34. To obtain the highest density and the position of the highest density (S38).

  Next, the abnormality determination unit 32 determines whether or not the maximum density of the line read in the absence of the document S acquired in step S38 is equal to or higher than the second predetermined density D2 (S39).

  FIG. 7 is a diagram illustrating the output of the CCD image sensor when an abnormality is included when the reference plate is read. The horizontal axis of FIG. 7 indicates the main scanning direction X, and the vertical axis thereof indicates the output Y of the CCD image sensor 25. Since the CCD image pickup device 25 receives the reflected light from the reference plate 10 and performs photoelectric conversion, the larger the output Y of the CCD image pickup device 25, the smaller the pixel value (pixel density). The smaller the output Y of the element 25, the larger the pixel value (pixel density).

  When foreign matter exceeding a certain size adheres on the contact glass 27 and causes a streaky abnormal image along the sub-scanning direction to appear in the image read from the document S, 7, deep grooves G appear in the distribution along the main scanning direction X in the output Y of the CCD image sensor 25. For this reason, the second predetermined density D2 is appropriately set according to the density of a line to be determined as an abnormal image such as a black line, which is set in advance according to specifications or the like. The second predetermined value D2 is set to a relatively large value, and is set to 128, for example, in the case of 256 gradations where white is 0 and black is 255. FIG. 7 shows the output value Yth of the CCD image sensor 25 corresponding to the second predetermined density D2.

  As a result of the determination in step S39, when the maximum density in the line is not equal to or higher than the second predetermined density (No), the abnormality determination unit 32 determines that a streak abnormal image has not been detected, and performs this abnormality determination operation. finish. On the other hand, as a result of this determination, when the maximum density in the line is equal to or higher than the second predetermined density D2 (Yes), the abnormality determining unit 32 executes the next process S40.

  In process S40, the abnormality determination unit 32 determines whether or not the absolute value of the difference between the highest density position of the line A and the highest density position of the line read without the document S is equal to or smaller than the third predetermined width W3. to decide. The third predetermined width W3 is appropriately set according to the width of the streak to be determined as a streak-like abnormal image along the sub-scanning direction set in advance according to specifications or the like, and is set to 160 pixels, for example. .

  In the above description, the absolute value of the difference between the highest density position of the line A and the highest density position of the line read without the document S is used, but the highest density position of the line B and the document S are not present. The absolute value of the difference from the highest density position of the read line may be used.

  As a result of this determination, when the absolute value of this difference is not equal to or smaller than the third predetermined width W3 (No), the abnormality determination unit 32 determines that a streak abnormal image has not been detected, and ends the abnormality determination operation. To do. On the other hand, if the absolute value of the difference is equal to or smaller than the third predetermined width W3 as a result of this determination (Yes), the abnormality determining unit 32 determines whether the streak image is an image of the document S or an abnormal image. In order to determine whether or not, the following process S41 is executed.

  In process S41, the abnormality determination unit 32 determines whether or not the absolute value of the difference between the maximum density of the line A and the maximum density of the line read without the document S is equal to or less than the third predetermined density D3. . The third predetermined density D3 is appropriately set in accordance with the density of the stripe to be determined as a streak image along the sub-scanning direction such as a ruled line, which is set in advance according to the specification or the like. The density caused by the paper dust or the like adhering on the contact glass 27 is a density corresponding to the type of the paper, and is relatively thin, for example, on high-quality paper. For this reason, normally, the density in a streak image such as a ruled line in the document S is higher than the density caused by paper dust or the like adhering to the contact glass 27, so the third predetermined density D3 is relatively high. In the case of 256 gradations where a large value is set, white is set to 0, and black is set to 255, for example, 128 is set.

  As a result of this determination, when the absolute value of this difference is not less than or equal to the third predetermined density D3 (No), it is determined that the streak image is an image of the document S such as a ruled line, and the abnormality determination unit 32 Then, it is determined that a streak-like abnormal image has not been detected, and this abnormality determination operation is terminated. On the other hand, if the absolute value of this difference is equal to or smaller than the third predetermined density D3 as a result of this determination (Yes), the abnormality determination unit 32 determines that a streak abnormal image has been detected, and sets the document reading position P as the original reading position P. The reading position setting unit 33 is notified that the change should be made, and the abnormality determination operation is terminated.

  By operating in this way, in the image reading apparatus SC according to the present embodiment, when there is a streak image along the transport direction such as a ruled line in the document S, the image to be determined as the image of the document S. An erroneous determination that determines a streak image as a streak abnormal image can be reduced, and the image of the original S and the abnormal image can be more reliably discriminated.

  In the present embodiment, the first to fifth predetermined values in the claims are, as examples, the first predetermined density D1, the second predetermined width W2, the second predetermined density D2, the third predetermined width W3, and the first 3 corresponds to a predetermined density D3.

  Next, a document reading position moving operation for changing the document reading position P when abnormality is detected will be described.

  FIG. 8 is a flowchart illustrating an original reading position moving operation in the image reading apparatus according to the embodiment.

  In FIG. 8, when the abnormality determination unit 32 of the control unit 3 detects an abnormal image, the reading position setting unit 33 of the control unit 3 first moves the document reading position P in the image reading device SC. It is determined whether or not the number of movements N is smaller than the number of document reading positions, which is the number of document reading positions P that can be moved (S61). The document reading position movement number N is read from the document reading position movement number storage unit 36 when the image reading device SC is activated.

  For example, as shown in FIG. 2, it is assumed that the document reading position P can be changed between four locations along the sub-scanning direction. In the following description, it is assumed that the corresponding four document reading positions P are simultaneously expressed by reference signs A0 to A3 attached to the incident light in FIG. In FIG. 2, each position of the first mirror 21 corresponding to each position A0 to A3 is indicated by a two-dot chain phantom line. The distance between the positions A0 to A3 is set to about 0.7 mm, assuming that the influence of foreign matters having a size of about 0.6 mm is eliminated. Accordingly, the document reading start timing is shifted by about 37 milliseconds. Although the number of document reading positions P is four in the example shown in FIG. 2, it may be smaller or larger than four, and is an arbitrary number set in advance according to specifications.

  If the result of determination in step S61 is that the current number N of document reading position movements is smaller than the number of document reading positions (Yes), the reading position setting unit 33 increments the number N of document reading position movements by 1 (S62). ). That is, the document reading position movement count N is set to the document reading position movement count N + 1 (document reading position movement count N ← document reading position movement count N + 1). The initial value of the document reading position movement count N is 1 in this embodiment.

  Then, the reading position setting unit 33 moves the document reading position P to the next position (S63), and executes the process S66. More specifically, the reading position setting unit 33 reads the setting data of the document reading position P corresponding to the number N of document reading position movements from the setting data storage unit 35, and sends the read setting data to the moving frame driving unit 29. Output.

  When the setting data of the document reading position P is input, the moving frame driving unit 29 moves the moving frame 28 so that the document reading position P becomes a position corresponding to the setting data. As a result, the document reading position P is moved to the next position.

  For example, when the document reading position movement frequency N = 1, 2, 3, 4 corresponds to the document reading position P = A0, A1, A2, A3, respectively, and the current document reading position movement frequency N is 2. When an abnormal image is detected by the abnormality determination unit 32, the number N of document reading position movements is N = 2 + 1 = 3, and the document reading position P is moved from the position A1 to the position A2 by the movement of the moving frame 28 by the moving frame driving unit 29. Moved to.

  On the other hand, if it is determined in step S61 that the current document reading position movement count N is not smaller than the number of document reading positions (No), the reading position setting unit 33 sets the document reading position movement count N to an initial value. Clear (S64). That is, the document reading position movement count N is set to an initial value 1 (document reading position movement count N ← 1).

  Then, the reading position setting unit 33 moves the document reading position P to the initial position A0 (S65), and executes the process S66. More specifically, the reading position setting unit 33 takes out setting data of the document reading position P corresponding to the number of times N of reading of the document reading position from the setting data storage unit 35, and uses the taken setting data of the document reading position P as a scanner. To the moving frame driving unit 29 of the unit 2.

  When the setting data of the document reading position P is input, the moving frame driving unit 29 moves the moving frame 28 so that the document reading position P becomes a position corresponding to the setting data. As a result, the document reading position P is moved to the next position P.

  That is, when the document reading position movement count N = 1, 2, 3, 4 corresponds to the document reading position P = A0, A1, A2, A3, respectively, and the current document reading position movement count N is 4. When an abnormal image is detected by the abnormality determination unit 32, the document reading position movement count N is set to 1, and the movement of the moving frame 28 by the moving frame driving unit 29 moves the document reading position P from the position A3 to the position A0. Is done.

  In step S <b> 66, the reading position setting unit 33 stores the current document reading position movement number N in the document reading position movement number storage unit 36. As a result, the current document reading position movement count N is backed up. For this reason, when the image reading device SC is turned off and then turned on, the document reading position movement count N before the power is turned off is held.

  By operating in this way, when an abnormal image is detected by the abnormality determination unit 32, the document reading position P is sequentially moved from the initial position A0 to the final position A3. Then, when the document reading position P is at the final position A3 and the abnormality determination unit 32 detects an abnormal image, the document reading position P is returned to the initial position A0. As described above, every time an abnormal image is detected by the abnormality determination unit 32, the document reading position P is sequentially and cyclically moved from the initial position A0 to the final position A3. Even if foreign matter adheres or scratches occur, the occurrence of abnormal images can be effectively suppressed.

  In the above-described embodiment, when the image reading device SC moves the document reading position P in step S65 to the initial position A0, the image reading device SC uses guidance means such as display on a display unit (not shown) and generation of a warning sound. You may be comprised so that the guidance which urges a user to clean the contact glass 27 may be emitted. In the image reading device SC of the present embodiment, erroneous determination that determines a streak image to be determined as an image of the document S as a streak abnormal image can be reduced. The generation of can be suppressed.

  In the above-described embodiment, the setting data corresponding to the positions A0 to A3 of the document reading position P is calculated in advance and stored in the setting data storage unit 35. However, when the document reading position P is moved, a predetermined data is stored. The moving distance and the document reading start timing may be calculated by the following formula. Alternatively, an arbitrary position may be selected at random (randomly).

  In the above-described embodiment, the program executed by the control unit 3 can be supplied through a recording medium such as a ROM or a CD-ROM, or can be supplied through a transmission medium such as a network. The transmission medium is not limited to a wired transmission medium, and may be a wireless transmission medium. The transmission medium includes not only a communication line but also a relay device that relays the communication line, such as a router.

  When the program is supplied through the ROM, the ROM in which the program is recorded is mounted on the control unit 3 so that the program can be executed by the control unit 3. When the program is supplied through a CD-ROM, it can be used for execution by the control unit 3 by connecting a CD-ROM reader and temporarily storing the program in, for example, an HDD. Further, when the program is supplied through the transmission medium, the program received via the network can be stored in, for example, the HDD, and can be used for execution by the control unit 3.

  In order to express the present invention, the present invention has been properly and fully described through the embodiments with reference to the drawings. However, those skilled in the art can easily change and / or improve the above-described embodiments. It should be recognized that this is possible. Accordingly, unless the modifications or improvements implemented by those skilled in the art are at a level that departs from the scope of the claims recited in the claims, the modifications or improvements are not limited to the scope of the claims. To be construed as inclusive.

1 is a schematic cross-sectional view mainly showing a mechanical and optical configuration of an image reading apparatus in an embodiment. FIG. 2 is a partially enlarged view of FIG. 1 is a block diagram mainly illustrating an electrical configuration of an image reading apparatus according to an embodiment. 6 is a flowchart (part 1) illustrating an abnormality determination operation in the image reading apparatus according to the embodiment. 6 is a flowchart (part 2) illustrating an abnormality determination operation in the image reading apparatus according to the embodiment. FIG. 6 is a diagram for explaining a document reading area. It is a figure which shows the output of a CCD image pick-up element when abnormality is contained when a reference | standard board is read. 5 is a flowchart illustrating a document reading position moving operation in the image reading apparatus of the embodiment.

Explanation of symbols

SC image reading device P document reading position 1 paper feed unit 2 scanner unit 3 control unit 10 reference plate 11 document discharge table 12 document feed table 13 paper feed roller 14 registration switch 15 registration roller 16 timing switch 17 separation roller 18 paper discharge Roller 19 Document holding member 21, 22, 23 Mirror 24 Lens system 25 CCD image pickup device 26 Exposure lamp 27 Contact glass 28 Moving frame 29 Moving frame driving unit 31 Reading control unit 32 Abnormality determining unit

Claims (4)

In an image reading apparatus that reads an image of a document conveyed so as to move in the sub-scanning direction on one main surface of a transparent plate from the other main surface side of the transparent plate by reflected light of a light source,
A reference plate disposed opposite to one main surface of the transparent plate and extending in the main scanning direction;
Based on the highest density in the image of the preset area of the original and the highest density in the image read from the reference plate in a state where the original is not on one main surface of the transparent plate, An abnormality determination unit that determines whether or not there is an abnormality in the read image;
And a reading position setting unit that changes a reading position of the document along the sub-scanning direction within a range in which the reference plate can be read when the abnormality determination unit determines that there is an abnormality. apparatus. The image of the preset region of the document includes a first image of a region at a leading end in the document transport direction and having a preset width in the sub-scanning direction extending in the main scanning direction, and the document And a second image of a region having a width preset in the sub-scanning direction and extending in the main scanning direction at the rear end in the conveying direction of
An image obtained by reading the reference plate in a state where the original is not on one main surface of the transparent plate is a third image obtained by reading the reference plate by the width without the original being on one main surface of the transparent plate. The image reading apparatus according to claim 1, wherein the image reading apparatus is an image. The abnormality determination unit determines whether or not each maximum density in the first and second images is equal to or higher than a first predetermined value, and the position of the highest density in the first image and the second image It is determined whether or not the absolute value of the difference from the highest density position is equal to or smaller than a second predetermined value set in advance, and whether or not the highest density in the third image is equal to or larger than a third predetermined value. And determining whether the absolute value of the difference between the highest density position in the first or second image and the highest density position in the third image is equal to or less than a preset fourth predetermined value. Determining whether the absolute value of the difference between the highest density in the first or second image and the highest density in the third image is equal to or less than a preset fifth predetermined value. It is characterized by determining whether or not there is an abnormality in the scanned image. The image reading apparatus according to claim 1 or 2. In an image reading method of reading an image of a document conveyed so as to move in the sub-scanning direction on one main surface of a transparent plate from the other main surface side of the transparent plate by reflected light of a light source,
Obtaining a maximum density in an image of a preset area of the document;
A step of acquiring a maximum density in an image obtained by reading a reference plate that is disposed opposite to one main surface of the transparent plate and extends in the main scanning direction in a state where the original is not on the one main surface of the transparent plate. When,
Based on the highest density in the image of the preset area of the original and the highest density in the image read from the reference plate in a state where the original is not on one main surface of the transparent plate, Determining whether there is an abnormality in the read image;
And a step of changing the reading position of the document along the sub-scanning direction within a range where the reference plate can be read when it is determined that there is an abnormality.

Images