JP2010028442A - Image reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique for detecting various foreign matters in an image reader. <P>SOLUTION: A foreign matter is detected by the difference of the color from a background color. Also, by changing the background color at a read position, also about white foreign matter XB which can not be recognized in a white background can be detected. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image reading apparatus that reads an image on a document and acquires image data.

2. Description of the Related Art Conventionally, in an image reading apparatus, a technique for shading correction of image data using reference data obtained by reading a color reference plate has been adopted in order to correct variations in reading elements of an image sensor (for example, Patent Document 1).
JP-A-10-42111 (paragraph [0021] etc.)

  In the conventional technique, if there is foreign matter such as dust, dust, and dirt at the reading position, an accurate white reference value cannot be obtained, which causes image defects. In addition, the presence of foreign matter also becomes an obstacle to the acquisition of accurate image data from a document itself.

  SUMMARY An advantage of some aspects of the invention is that it provides a technique capable of accurately detecting the presence of a foreign substance in an image reading apparatus.

  In order to solve the above-described problem, an image reading apparatus according to claim 1 is an image reading apparatus that acquires image data from a document at a reading position, and reads the image for each main scanning line at the reading position. An image sensor that acquires the reading position, a light source that illuminates the reading position, a cylindrical member that is arranged to face the image sensor at the reading position, and the cylindrical member that moves in the diametrical direction, thereby reading the reading position. When the signal intensity fluctuates by more than a predetermined threshold in any one of the moving part that can be arranged at two or more different positions with respect to the position and the image data obtained for the cylindrical member at each position A foreign matter detection unit that determines that foreign matter is present at the reading position.

  According to this image reading apparatus, the amount of reflected light from the cylindrical member to the image sensor increases or decreases when the position of the cylindrical member is changed by the moving unit. Therefore, for example, when the amount of light reflected from the cylindrical member is large at the reading position, it is difficult to detect the foreign matter. Even when a bright colored foreign matter exists, the cylindrical member moves and reflects from the cylindrical member. By reducing the amount of light, the difference in the signal intensity of the image data between the foreign object and its surroundings is increased, and the presence of the foreign object can be accurately detected.

  According to a second aspect of the present invention, the image reading apparatus according to the first aspect stores the image data obtained for the cylindrical member at each position as a reference value for detecting the foreign matter in a state where there is no foreign matter. And further comprising a memory, wherein the foreign object detection unit obtains a difference in signal intensity between the reference value at each position and the latest image data obtained at the same position, and the difference is a predetermined threshold value at any position. In the above case, it may be determined that there is a foreign object at the reading position.

  According to a third aspect of the present invention, the image reading apparatus according to the first aspect stores image data obtained for the cylindrical member at a certain position in the absence of foreign matter as a first reference value, and the image A memory for preliminarily storing a signal intensity ratio between the data and the image data obtained for the cylindrical member at another position, and the latest image data obtained for the cylindrical member at the certain position are multiplied by the ratio. Thus, a predicted value acquisition unit that acquires a predicted value of the latest image data for the cylindrical member at the other position may be further included. The foreign object detection unit is the same as the difference between the first reference value and the signal intensity of the latest image data of the cylindrical member at a certain position, and the predicted value for the cylindrical member at the other position. A difference between the signal intensity of the latest image data for the cylindrical member at the position is acquired, and if the difference is equal to or greater than a predetermined threshold at any position, it is determined that there is a foreign object at the reading position. You may come to do.

  According to a fourth aspect of the present invention, the image reading apparatus according to the first aspect obtains an average value of signal intensity per pixel for the latest image data obtained for the cylindrical member at each position. An acquisition unit may be further provided. The foreign object detection unit obtains a difference between the average value obtained for the cylindrical member at each position and the signal intensity per pixel in the image data obtained for the cylindrical member at the same position. If the difference is greater than or equal to a predetermined threshold at that position, it may be determined that a foreign object is present at the reading position.

  According to the image reading apparatus of the present invention, the cylindrical member moves at the reading position even when there is a bright foreign matter that is difficult to detect when the amount of reflected light from the cylindrical member is large. Since the amount of reflected light from the cylindrical member is reduced, the difference in the signal intensity of the image data between the foreign matter and its surroundings is increased, so that the presence of the foreign matter can be accurately detected.

[1] First Embodiment An embodiment of the present invention will be described with reference to the image reading apparatus 10.

(1-1) Overview of Image Reading Apparatus 10 FIG. 1 is a front view showing a main configuration of the image reading apparatus 10 according to the present embodiment. As shown in FIG. 1, the image reading apparatus 10 includes a paper feed tray 11, a paper feed roller 12, a separation roller 13, a registration roller 14, a platen roller 15, a CIS (Contact Image Sensor) unit 16, a document conveying roller 17, a discharge roller. A paper roller 18, a paper discharge tray 19, and an actuator 20 are provided.

  The paper feed tray 11 is a tray for placing a document P to be read. The paper feed roller 12 feeds the document P placed on the paper feed tray 11 to the separation roller 13 in order from the uppermost side. The separation roller 13 is a roller for preventing double feeding, and conveys the original P fed from the paper feed roller 12 to the registration roller 14 one by one. The registration roller 14 adjusts the conveyance posture of the document P conveyed from the separation roller 13 and conveys it to the platen roller 15. The platen roller 15 conveys the document P conveyed from the registration roller 14 to the image reading position SA.

  At the image reading position SA, the CIS unit 16 and the document conveying roller 17 are installed so as to face each other.

  The CIS unit 16 includes an LED light source 16a, an image sensor 16b, and a contact glass 16c. The CIS unit 16 has one surface of the document P transported between the contact glass 16c and the document transport roller 17 at the image reading position SA (the surface on which the image to be scanned is printed: hereinafter this surface). Is referred to as a reading target surface). The position of the CIS unit 16 with respect to the reading position SA is fixed, and the positions of the light source 16a, the image sensor 16b, and the contact glass 16c in the CIS unit 16 are fixed.

  The light source 16a is disposed so as to irradiate the object (the original P or the original conveying roller 17) at the image reading position SA. As the light source 16a, an LED can be suitably used.

  The image sensor 16b converts the amount of received light into an electrical signal. This electrical signal is converted from an analog signal to a digital signal by an A / D conversion unit (not shown) and output to an image processing unit 210 described later. The image sensor 16b is disposed at a position where the light reflected by the original P or the original conveying roller 17 can be received at the reading position SA. The image sensor 16b includes a plurality of reading elements arranged in the main scanning direction (a direction perpendicular to the document conveyance direction). That is, the image sensor 16b can acquire image data from the object (original P or original conveyance roller 17) present at the reading position SA for each main scanning line. Specifically, a CCD, CMOS, or the like can be used as the image sensor 16b.

  The contact glass 16 c is disposed between the LED light source 16 a and the image sensor 16 b and the document conveying roller 17. Specifically, the contact glass 16c is arranged on the optical path of the emitted light from the light source 16a to the reading position SA and on the optical path where the reflected light from the document P on the reading position SA goes to the image sensor 16b. Is done.

  That is, the illumination light emitted from the light source 16a reaches the reading position SA through the contact glass 16c, is reflected by the original P or the original conveying roller 17 at the reading position SA, and passes through the contact glass 16c again to be the CIS unit 16 again. It enters and is detected by the image sensor 16c.

  The document transport roller 17 is a white and cylindrical roller, and serves both as a white reference body for shading correction and as a transport roller for the document P. The document transport roller 17 is provided on the opposite side of the document P with respect to the CIS unit 16 (so as to face the surface (back surface) opposite to the surface to be read with respect to the document P). The document transport roller 17 is installed in parallel to the main scanning direction of the image sensor 16b and movable with respect to the document P transport direction.

  The paper discharge roller 18 discharges the document P conveyed from the document conveyance roller 17 to a paper discharge tray 19. The paper discharge tray 19 receives the document P after image reading discharged from the paper discharge tray 19.

  The actuator 20 is an actuator for adjusting the position of the document transport roller 17 in the transport direction of the document P, that is, in the sub-scanning direction (direction perpendicular to the main scanning direction) of the CIS unit 16 under the control of the main control unit 25. . The actuator 20 is composed of mechanical elements such as a stepping motor, a clutch, and / or a solenoid, for example. The moving direction of the document conveying roller 17 by the actuator 20 is indicated by a white arrow in FIG.

As shown in FIG. 2, the image reading apparatus 10 includes an image processing apparatus 210, a display panel 24, a main control unit 25, and the like in addition to the above-described members. The image processing apparatus 210 includes a memory 21, a foreign matter detection unit 22, a shading correction unit 23, and the like. The memory 21 stores information such as a foreign matter detection reference value and a shading reference value. The reference value for foreign object detection will be described later. The shading reference value includes a white reference value and a black reference value. The white reference value is image data obtained in a state where the light source 16a is turned on with respect to the document conveying roller 17 at the normal position described later, and the black reference value is turned off with respect to the document conveying roller 17 at the same position. It is the image data obtained in the state.

  The foreign matter detection unit 22 can detect foreign matter on the contact glass 16 c based on the image data obtained by the image sensor 16 b for the document conveying roller 17 and the reference value for foreign matter detection in the memory 21. The foreign matter includes dust, dust such as paper fragments, and dirt such as ink.

  The shading correction unit 23 can perform shading correction of the document image data based on the document image data (image data obtained by the image sensor 16 c for the document P) and the shading reference value in the memory 21.

  As the display panel 24, a display device such as a liquid crystal display panel can be used. The display panel 24 can display various images to the user.

  The main control unit 25 can control the operation of each unit described above in the image reading apparatus 10. The operation of the image reading apparatus 10 realized by the control of the main control unit 25 will be described later.

  The image processing unit 210 and the main control unit 25 may be realized by hardware or may be realized by software. For example, these functional units may be configured by a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and other storage media. In this case, these functional units The various functions are realized by the CPU reading and executing a program stored in the ROM or the like. The RAM functions as a work area for the CPU.

(1-2) Operation of the image reading apparatus 10 (i) Foreign object detection [Principle]
The principle of the foreign object detection operation will be described with reference to FIGS. 3A to FIG. 3C and FIG. 4A to FIG. 4C show the arrangement of members around the reading position SA and the light traveling direction when determining the presence or absence of foreign matter. It is. In FIGS. 3A to 3C and FIGS. 4A to 4C, the direction of the dotted arrow indicates the light traveling direction, and the thickness of the dotted arrow indicates the amount of light. 5 and 6 show an example of image data obtained by the arrangement shown in FIG. 3A and an example of image data obtained by the arrangement shown in FIG. 5 and 6, the horizontal axis of the lower chart indicates the pixel position in the main scanning direction, and the vertical axis indicates the output signal intensity of the reading element at each pixel position.

  Normally, during document conveyance or standby, the document conveyance roller 17 causes the reflected light generated by the light emitted from the light source 16a to be reflected by the document conveyance roller 17 to the CCD 16b as shown in FIG. Are arranged at positions where the incidence rate of the light source becomes relatively high. This position is referred to as a “normal position”. The data acquired at this position shows a white image because the amount of light incident on the CCD 16b is large (FIG. 5). In the present embodiment, the normal position is the same as the position of the document transport roller 17 when an image is acquired from the document P.

  However, as shown in FIG. 3B, when black foreign matter (dark foreign matter) XB exists on the contact glass 16c at the reading position SA, reading is performed at a pixel position where the black foreign matter XB from the light source 16a exists. The amount of light incident on the element is smaller than the amount of light incident on the reading element at the pixel position where the black foreign object XB does not exist. That is, a color difference is generated between the background color and the foreign matter at the reading position SA. As a result, the image data at the pixel position where the black foreign object XB exists represents a darker (darker) image than the surrounding area (“XB” in FIG. 5).

  However, as shown in FIG. 3C, the foreign matter present on the contact glass 16 c is a white foreign matter (light foreign matter) XW having the same whiteness as that of the original conveying roller 17. When the reflectance of light and the reflectance of light of the white foreign object XW are substantially the same, there is no difference in image data between the pixel position where the white foreign object XW exists and the pixel position where it does not exist (FIG. 5). "XW").

  As shown in FIG. 4A, the actuator 20 can move the document transport roller 17 from the normal position in the sub-scanning direction under the control of the main control unit 25. The position after the movement is referred to as a “shift position”. At the shift position, the angle formed by the optical path of the light emitted from the light source 16a and the surface of the document conveying roller 17 changes from the normal position. As a result, the path of the reflected light from the document conveying roller 17 changes, and the incidence rate of the reflected light from the document conveying roller 17 on the image sensor 16b is lower than when the document conveying roller 17 is in the normal position. To do. Therefore, the obtained image data is dark overall (close to black) (FIG. 6).

  Even when the document transport roller 17 moves to the shift position, the positional relationship among the light source 16a, the imagen sensor 16b, and the foreign matter XB on the contact glass 16c is fixed, so as shown in FIG. The amount of reflected light reaching the image sensor 16b from the foreign object XB does not change. However, as described above, the amount of reflected light reaching the image sensor 16b from the document conveying roller 17 is reduced at the shift position, so the background color is darker than the normal position. Therefore, as shown as “XB” in FIG. 6, the difference between the image data of the pixel position where the black foreign object XB exists and the surrounding (background) image data becomes small.

  As shown in FIG. 4C, the amount of reflected light reaching the image sensor 16b from the white foreign object XW does not change between the shift position and the normal position. However, as described above, at the shift position, the amount of light reflected from the document conveying roller 17 is reduced and the background color is dark. Therefore, the image data at the pixel position where the white foreign object XB exists is brighter than the surrounding (background) (“XW” in FIG. 6).

  As described above, the image reading apparatus 10 can change the background color of the foreign matter at the reading position SA by the actuator 20. Due to the change in the background color, the image reading apparatus 10 can increase the contrast between the foreign matter and the background. That is, the difference in the size of the image data obtained between the foreign matter on the optical path from the light source 16a and the surrounding area can be increased. Since the foreign object detection unit 22 can determine that there is a foreign object at the pixel position where this large difference is obtained, the image reading apparatus 10 can detect foreign objects of various colors. Can do.

[Specific operation]
FIG. 7 is a flowchart showing the operation of the image reading apparatus 10 when foreign matter is detected.

  As shown in FIG. 7, during the foreign object detection operation, the main control unit 25 acquires image data at the normal position by the CCD 16b (step S101), and then controls the actuator 20 to acquire image data at the shift position. (Steps S102 and S103).

  Then, the foreign object detection unit 22 acquires a difference between the image data (latest image data) thus obtained under the current conditions and the reference value for foreign object detection stored in the memory 21 (step S104). If it is equal to or greater than the threshold value α (α1, α2) (Yes in step S105), it is determined that there is a foreign object (step S106). In any image data, if the difference from the foreign object detection reference value is less than the threshold value α (No in step S105), it is determined that there is no foreign object (step S108).

  Specifically, as the reference value for foreign matter detection, image data about the document transport roller 17 on the main scanning line at the normal position and the shift position in the absence of foreign matter can be used. The foreign matter detection reference value obtained at the normal position is defined as a first reference value, and the foreign matter detection reference value obtained at the shift position is defined as a second reference value. The acquisition timing of the foreign object detection reference value is not particularly limited, and may be acquired before shipment from the factory, or the foreign object detection reference value is acquired at the first activation of the image reading apparatus 10 after shipment. The main control unit 25 may have such a program. Of the past image data determined as having no foreign matter, the latest image data may be used as the foreign matter detection reference value.

  The foreign object detection unit 22 compares the image data at each pixel position at the normal position with the first reference value at the pixel position, and acquires the above-described difference for each pixel position. Similarly, for the image data at the shift position, the foreign object detection unit 22 acquires a difference from the second reference value. Then, the image data at the normal position includes data whose absolute value of the difference is greater than or equal to the threshold value α1, or the image data at the shift position includes data whose absolute value of the difference is equal to or greater than the threshold value α2. If it is, it can be determined that there is a foreign object. The foreign matter detection unit 22 can determine that there is no foreign matter if the obtained difference is less than the threshold value α1 and less than α2 at any position.

  The threshold value α1 for the first reference value and the threshold value α2 for the second reference value may be the same or different. Moreover, the magnitude | size of each threshold value is set suitably, Comprising: It is not limited to a specific numerical value.

  When it is determined by the above operation that there is a foreign object, the main control unit 25 displays a message such as “Please clean the contact glass” on the display panel 24 (step S107). On the other hand, if it is determined that there is no foreign object, the main control unit 25 may store the above-described image data obtained at the normal position in the memory 21 as a white reference value for shading correction (step S109). ).

  When the above operation is completed regardless of the presence or absence of foreign matter, the document conveying roller 17 is returned to the normal position by the actuator 20 (step S110).

  The timing for performing the above foreign object detection operation is not particularly limited, for example, when the power is turned on, before document reading, or whenever the number of read sheets reaches a predetermined number.

  As described above, the image reading apparatus 10 changes the amount of reflected light reaching the image sensor 16b from the document conveying roller 17 at the reading position SA, that is, the background color (specifically, brightness) by the operation of the actuator 20. Can do. When the background color (brightness) is changed in this way, the color difference between the dark color and the light color is different from the background color. Therefore, it is possible to detect various foreign objects using this difference. it can.

  Further, since the image reading apparatus 10 can change the background color by moving the document conveying roller 17, it is not necessary to provide a reference plate or the like of a different color.

(Ii) Image Reading When reading an image, the image reading apparatus 10 conveys the document P by the document conveying roller 17 or the like under the control of the main control unit 25. The illumination light from the light source 16a is reflected by the document P passing through the reading position SA, and this reflected light is detected by the image sensor 16b. The electrical signal from the image sensor 16b is digitally converted to an A / D converter (not shown) and transmitted to the shading correction unit 23 as document data (image data about the document).

  The shading correction unit 23 uses the shading reference value in the memory 21 to perform shading correction with the white reference value set to 100% and the black reference value set to 0% for the document data thus obtained.

  The image reading apparatus 10 may perform further image processing on the document data after the shading correction, may transmit it to an external apparatus (facsimile apparatus, image forming apparatus, etc.), or stores it in a storage device. Also good.

  Note that once it is determined that there is a foreign object, the main control unit 25 may prohibit document reading until it is determined that there is no foreign object in the operation of FIG. Further, the main control unit 25 may permit document reading even if a foreign object is detected, if there is an instruction from the user.

[2] Second Embodiment An image reading apparatus according to the present embodiment will be described with reference to the block diagram of FIG.

  The image reading apparatus according to the present embodiment has substantially the same configuration as the image reading apparatus 10 according to the first embodiment, except that the image processing apparatus 211 is provided instead of the image processing apparatus 210.

  As illustrated in FIG. 8, the image processing apparatus 211 further includes a second reference value calculation unit (predicted value acquisition unit) 26 in addition to the configuration of the image processing unit 210.

  Further, as shown in FIG. 8, in the memory 21, the document roller 17 is in the shift position with respect to the amount of reflected light reaching the image sensor 16b from the document transport roller 17 when the document roller 17 is in the normal position in the absence of foreign matter. The ratio of the amount of reflected light with a certain time is stored in advance. More specifically, the ratio of the image signal intensity from the image sensor 16b can be used as the reflected light amount ratio. The acquisition timing of the reflected light amount ratio can be the same as the acquisition timing of the foreign object detection reference value of the first embodiment.

  The second reference value calculation unit 26 calculates the predicted value of the image data for one scanning line at the shift position by multiplying the image data (FIG. 5) obtained at the normal position by this reflected light amount ratio.

  The foreign object detection unit 22 obtains a difference between the second reference value and the image data actually obtained at the shift position (FIG. 6) using the predicted value as the second reference value. If this difference is equal to or greater than a predetermined threshold, it can be determined that there is a foreign object.

  Thus, by calculating the predicted value from the actual measurement value and detecting the foreign matter based on the predicted value, the foreign matter detection that flexibly copes with the deterioration of the image sensor can be performed.

  For the image data (FIG. 5) obtained at the normal position, the foreign matter detector 22 can determine the presence or absence of foreign matter by the same processing as in the first embodiment.

[3] Third Embodiment An image reading apparatus according to the present embodiment will be described with reference to the block diagram of FIG.

  As shown in FIG. 9, the image reading apparatus of the present embodiment has substantially the same configuration as the image reading apparatus 10 of the first embodiment, except that an image processing apparatus 212 is provided instead of the image processing apparatus 210.

  The image processing apparatus 212 further includes an average value calculation unit (average value acquisition unit) 27 in addition to the configuration of the image processing unit 210.

  The average value calculating unit 27 calculates the average value per pixel of the image data for one scanning line obtained at the normal position (FIG. 5) and the image data for one scanning line obtained at the shift position (FIG. 6). The average value per pixel is calculated.

  The foreign object detector 22 uses the average value at the normal position as the first reference value and the reference value at the shift position as the second reference value, and the difference between the first reference value and the image data (FIG. 5) obtained at the normal position, And the difference between the second reference value and the image data (FIG. 6) obtained at the shift position is acquired. And the foreign material detection part 22 will determine with a foreign material, if each difference is more than a predetermined threshold value.

  According to the present embodiment, the memory 21 does not need to store a reference value for foreign object detection.

[4] Other Embodiments (4-1) In the first embodiment, the image reading apparatus 10 having the automatic document feeder is described. However, the present invention is directed to image data from a document placed on a document placement table. The present invention can also be applied to a flat bed type image reading apparatus that acquires the above.

  (4-2) The background color of the reading position is not limited to two types, and may be switched to three or more types. For example, in the image reading apparatus 10, the actuator 20 may be configured so that the document conveying roller 17 can be disposed at three or more positions on the light emission path from the light source 16 a.

  (4-3) In the first embodiment, the position of the document conveying roller 17 when obtaining one of the image data used for foreign object detection is the same as the position of the document conveying roller 17 when the white reference value is acquired. is there. However, the present invention is not limited to this, and the position and angle of the document conveying roller 17 when obtaining image data used for foreign object detection may be different from the position and angle of the document conveying roller 17 for obtaining the white reference value. Good.

  (4-4) In the first embodiment, it is assumed that the position of the document conveying roller 17 when obtaining one of the image data used for foreign object detection is the same as the position of the document conveying roller 17 during document conveyance. However, the present invention is not limited to this, and the two positions may be different.

  For example, the position of the document transport roller 17 during document transport may be the same as the shift position. In this case, it is possible to prevent the image on the back surface (the surface facing the document conveying roller 17) from being seen through to the reading target surface side at the reading position SA.

  (4-5) The white reference value does not need to be acquired during the foreign object detection operation as in the first embodiment, and may be acquired at another timing.

  Even when the white reference value is acquired during the foreign object detection operation, it is not necessary to rewrite the white reference value in each abnormality detection operation, even if the white reference value is rewritten once every several abnormality detection operations. Good.

  (4-6) In the first embodiment, it is acquired in advance as an example of a foreign matter detection unit that determines that a foreign matter is present when there is a fluctuation of a predetermined threshold value or more within one scanning line. A foreign matter detection unit 22 that detects a foreign matter by comparing a reference value with image data actually obtained from a white reference body is employed. However, the foreign matter detection unit is not limited to the configuration of the first embodiment, and it is only necessary to determine that there is a foreign matter if the color difference from the surroundings is a certain amount or more.

  For example, the foreign object detection unit obtains a difference between image data of adjacent pixels within one scanning line, and determines that there is a foreign object when the difference exceeds a predetermined threshold value. Good.

  (4-7) In the image reading device of each of the above-described embodiments, in the image data for one scanning line obtained by reading the document conveying roller 17, the pixel position data determined by the foreign matter detection unit as having foreign matters is A white reference value acquisition unit that corrects image data of surrounding pixels (for example, adjacent pixels) and an average value per pixel to obtain a white reference value for one scanning line; You may have.

  (4-8) Instead of the document conveying roller 17, it is possible to use a cylindrical member whose length at the reading position SA is equal to or longer than the length of the main scanning line and whose height direction is parallel to the main scanning line. it can. As long as the side surface of the cylindrical member is cylindrical, the shape of the internal structure, the bottom surface, and the like is not particularly limited.

  Since the surface color of the cylindrical member is uniform (for example, white), it can be used as a white reference body for obtaining a white reference value. Detection is possible.

  (4-9) The moving direction of the document conveying roller 17 by the actuator 20 is not necessarily parallel to the sub-scanning direction, and may be moved in a direction non-parallel to the main scanning direction. As a result, the amount of reflected light from the document conveying roller 17 to the image sensor 16b remains unchanged.

  (4-10) The image reading apparatus of each of the above-described embodiments can be used for a scanner, a copying machine, a facsimile machine, a multifunction machine, and the like.

  (4-11) Techniques obtained by appropriately combining the techniques of the above-described embodiments are also included in the technical scope of the present invention.

[5] Reference Form (5-1) As a white reference body, a plate-like white reference plate 170 can be used as shown in FIG. Except for the provision of the white reference plate 170, the image reading apparatus in FIG. 10 has the same configuration as that of the image reading apparatus 10 of the first embodiment. The description is omitted.

  As shown in FIGS. 10 (a) and 10 (b), the white reference plate 170 is disposed on the optical path from the light source 16a. The actuator 20 can change the traveling direction of the reflected light by tilting the white reference plate 170 and change the amount of light incident on the image sensor 16b.

  (5-2) The configuration for changing the background color at the reading position is not limited to the configuration using one white reference body as in the first to third embodiments, but also two or more reference bodies having different colors. And a moving unit that alternately arranges the reference bodies at the reading position may be used. That is, it can be said that the “background” is the amount of reflected light reaching from the white reference body to the image sensor.

  More specifically, the background color can be changed using a mechanism in which a black reference body is provided in addition to the white reference body and the white reference body and the black reference body are alternately arranged at the reading position. Further, the image reading apparatus may be provided with a reference body of three or more kinds of colors having different colors and a mechanism for alternately arranging these reference bodies at the reading position.

  (5-3) “Color” is a concept including “saturation”, “lightness”, “luminance”, and the like.

  That is, in the first to third embodiments described above, the amount of reflected light from the reading position when there is no document, that is, the amount of reflected light from the white reference body is cited as an example of “background color”. As an example, a configuration for changing the “brightness” has been described. For example, a reference body having different saturation may be used instead of a white reference body. In this case, an RGB color sensor is used as an image sensor. The foreign matter may be detected from the image data of each color.

1 is a schematic configuration diagram of an image reading apparatus 10 according to an embodiment of the present invention. 2 is a block diagram illustrating a configuration of a main part of the image reading apparatus 10. FIG. (A) is drawing which shows arrangement | positioning of the member of reading position SA periphery when the original conveyance roller 17 of the image reading apparatus 10 exists in a normal position, and the advancing direction of light, (b) and (c) are the said. FIG. 4 is an enlarged view of a part of (a) and shows the amount of reflected light when black foreign matter XB and white foreign matter XW exist on the contact glass 16c. (A) is drawing which shows arrangement | positioning of the member around reading position SA when the original conveyance roller 17 of the image reading apparatus 10 exists in a shift position, and the advancing direction of light, (b) and (c) are the above-mentioned. FIG. 4 is an enlarged view of a part of (a) and shows the amount of reflected light when black foreign matter XB and white foreign matter XW exist on the contact glass 16c. FIG. 4 is a diagram showing image data obtained for the document conveying roller 17 at the normal position shown in FIG. 3. FIG. 5 is a diagram showing image data obtained for the document conveying roller 17 at the shift position shown in FIG. 4. 3 is a flowchart illustrating an operation when a foreign object is detected in the image reading apparatus 10. 7 is a diagram illustrating an arrangement of members around the image reading apparatus SA when the posture of 70 is changed. It is a block diagram which shows the outline | summary of the image process part of the image reading apparatus of 2nd Embodiment. It is a block diagram which shows the outline | summary of the image process part of the image reading apparatus of 3rd Embodiment. (A) and (b) are reference forms using a white reference plate in place of the document conveying roller 17.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image reader 16 CIS unit 16a LED light source 16b Image sensor 16c Contact glass 17 Original conveyance roller (white reference body)
20 Actuator (moving part)
210 to 212 Image processing unit 21 Memory 22 Foreign matter detection unit 23 Shading correction unit 24 Display panel 25 Main control unit

Claims (4)

An image reading apparatus that acquires image data from a document at a reading position,
An image sensor that reads an image for each main scanning line to acquire image data at the reading position;
A light source that illuminates the reading position;
A cylindrical member arranged to face the image sensor at the reading position;
A moving unit that can be arranged at two or more different positions with respect to the reading position by moving the cylindrical member in the diameter direction;
In any one of the image data obtained with respect to the cylindrical member at each position, a foreign matter detection unit that determines that a foreign matter is present at the reading position when the signal intensity varies more than a predetermined threshold;
An image reading apparatus comprising: A memory for storing image data obtained for the cylindrical member at each position as a reference value for foreign object detection in a state where there is no foreign object,
The foreign matter detection unit obtains a difference in signal intensity between the reference value at each position and the latest image data obtained at the same position, and when the difference is equal to or greater than a predetermined threshold at any position. , It is determined that there is a foreign object at the reading position.
The image reading apparatus according to claim 1. The image data obtained for the cylindrical member at a certain position in the absence of foreign matter is stored as a first reference value, and the signal strength of the image data and the image data obtained for the cylindrical member at other positions is stored. A memory for storing the ratio in advance;
A predicted value acquisition unit for acquiring a predicted value of the latest image data for the cylindrical member at the other position by multiplying the latest image data obtained for the cylindrical member at the certain position by the ratio; Prepared,
The foreign object detection unit has the same position as the difference between the first reference value and the signal strength of the latest image data of the cylindrical member at the certain position and the predicted value for the cylindrical member at the other position. The difference between the signal intensity of the latest image data for the cylindrical member is acquired, and if the difference is equal to or greater than a predetermined threshold at any position, it is determined that there is a foreign object at the reading position. It has become,
The image reading apparatus according to claim 1. For the latest image data obtained for the cylindrical member at each position, further comprising an average value acquisition unit for acquiring an average value of signal intensity per pixel,
The foreign object detection unit obtains a difference between the average value obtained for the cylindrical member at each position and the signal intensity per pixel in the image data obtained for the cylindrical member at the same position, If the difference is greater than or equal to a predetermined threshold at the position, it is determined that there is a foreign object at the reading position.
The image reading apparatus according to claim 1.

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