Image reading device

Abstract

To make it difficult to be affected by floating dust which may infiltrate into a gap between an image sensor and a shading roller when shading data is acquired as compared with a case where no groove is provided on an arc surface which is an outer peripheral surface of the shading roller.SOLUTION: An image reading device 10 has an image sensor array 16 that consists of a plurality of image sensors arrayed in a main scanning direction, and a shading roller 20 that is provided to face the image sensor array 16 via a document transport path P, has a cylindrical shape extending in a longitudinal direction, and is rotatable about a rotation axis extending in the longitudinal direction. The shading roller 20 has, on its outer peripheral surface, a first white reference arc surface 30 that is white, has an arc-shaped section in a short-side direction, and extends in the longitudinal direction, and a groove portion 32 that is located at a preceding position to the first white reference arc surface 30 in a rotation direction of the shading roller 20 and extends in the longitudinal direction.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an image reading device. [Background technology]

[0002] Conventionally, there has been proposed an image reading device that reads the surface of a document using a CIS (Contact Image Sensor) while conveying the document. The CIS includes an image sensor array made up of multiple image sensors arranged in the main scanning direction. In addition, the image reading device may have a shading correction function that corrects unevenness in the amount of light from the light source in the main scanning direction or unevenness in the sensitivity of each image sensor in the image data obtained by scanning.

[0003] In image reading devices with a shading correction function, a shading roller is generally provided to face the CIS across the document transport path. The shading roller is a member with a reference surface on its outer circumferential surface for obtaining shading data, which is correction data for shading correction. The image sensor array of the CIS receives reflected light from the outer circumferential surface of the shading roller, thereby obtaining shading data indicating the pixel values ​​output by each image sensor.

[0004] Here, the amount of light received by the image sensor varies depending on the distance between the image sensor and the outer peripheral surface of the shading roller or the original. Specifically, the amount of light received by the image sensor decreases in proportion to the square of the distance. Therefore, in order to obtain appropriate shading data, it is ideal to obtain the shading data by making the distance from the image sensor to the original and the distance from the image sensor to the outer peripheral surface of the shading roller the same.

[0005] Therefore, a technology has been proposed in the past that makes the distance from the image sensor to the original the same as the distance from the image sensor to the outer surface of the shading roller, thereby obtaining shading data, while preventing the shading roller from coming into contact with the original when the original is being transported.

[0006] For example, Patent Documents 1 and 2 disclose a shading roller having a first portion whose distance from the center of rotation to its outer circumferential surface is approximately equal, and a second portion whose distance from the center of rotation to its outer circumferential surface is shorter than that of the first portion. In Patent Document 1, when acquiring shading data, the outer circumferential surface of the first portion faces the CIS so that the distance from the image sensor to the outer circumferential surface of the shading roller is the same, and when transporting an original, the outer circumferential surface of the second portion faces the CIS so that the shading roller is retracted from the original transport path. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2011-030174 A [Patent Document 2] JP 2014-003385 A Summary of the Invention [Problem to be solved by the invention]

[0008] Incidentally, when acquiring shading data, it is possible that stray dust may get between the image sensor and the shading roller. By stray dust, we mean dust that is not fixed to a member such as the outer circumferential surface of the shading roller. If stray dust gets between the image sensor and the shading roller when acquiring shading data, the influence of the stray dust makes it impossible to acquire appropriate shading data.

[0009] The object of the present invention is to make shading data acquisition less susceptible to the influence of floating debris that may get between the image sensor and the shading roller, compared to when no grooves are provided on the arcuate surface, which is the outer peripheral surface of the shading roller. [Means for solving the problem]

[0010] The invention according to claim 1 relates to a shading roller that is columnar extending in a longitudinal direction and rotatable around a rotation axis extending in the longitudinal direction, the shading roller having an outer peripheral surface that is white, has an arc-shaped short-side cross section, and has a first white reference arc surface extending in the longitudinal direction, and a groove portion that is located preceding the first white reference arc surface in the rotation direction of the shading roller and extends in the longitudinal direction; and a light receiving unit that receives reflected light of light irradiated from a light source toward the original or the shading roller, the light receiving unit being disposed above the shading roller and facing the shading roller across a document transport path, the light receiving unit being disposed above the shading roller in a main scanning direction, the light receiving unit being configured to receive reflected light of light irradiated from a light source toward the original or the shading roller ... The image reading device comprises an image sensor array consisting of a plurality of image sensors arranged in a row, and a processor, wherein the processor obtains shading data based on first arc surface reading data indicating pixel values ​​output by each of the image sensors, obtained by the image sensor array receiving the reflected light from the first white reference arc surface, modifies original reading data obtained by the image sensor array receiving the reflected light from the original based on the shading data to obtain modified original reading data, and forms image data corresponding to the original based on the modified original reading data. The invention according to claim 2 further comprises a second white reference arc surface, which is located on its outer peripheral surface at a position preceding the groove portion in the rotation direction of the shading roller, is white, has an arc-shaped short-side cross section, and extends in the longitudinal direction, and the processor analyzes one-side arc surface read data indicating pixel values ​​output by each of the image sensors, which is obtained by the image sensor array receiving the reflected light from one of the first white reference arc surface and the second white reference arc surface, when acquiring the one-side arc surface read data, The image reading device of claim 1, characterized in that an abnormal pixel value, which is the pixel value affected by a foreign object present between one of the arc surface and the second white reference arc surface and the image sensor array, is identified, and the shading data is obtained by replacing the identified abnormal pixel value with the pixel value of the image sensor corresponding to the abnormal pixel value included in the other-side arc surface reading data indicating the pixel values ​​output by each of the image sensors, obtained by the image sensor array receiving the reflected light from the other of the first white reference arc surface and the second white reference arc surface. The invention of claim 3 is the image reading device described in claim 2, characterized in that the processor analyzes second arc surface read data indicating the pixel values ​​output by each of the image sensors obtained by the image sensor array receiving the reflected light from the second white reference arc surface, and when acquiring the second arc surface read data, identifies abnormal pixel values ​​which are pixel values ​​affected by foreign matter present between the second white reference arc surface and the image sensor array, and acquires the shading data by replacing the identified abnormal pixel values ​​with pixel values ​​of the image sensor corresponding to the abnormal pixel values ​​included in the first arc surface read data. The invention of claim 4 is an image reading device described in any one of claims 1 to 3, further comprising a subsequent shading roller that is columnar and extends longitudinally and is arranged downstream of the conveying path from the shading roller, and a subsequent image sensor array that is arranged downstream of the conveying path from the image sensor array, faces the subsequent shading roller across the conveying path, and is arranged below the subsequent shading roller, and consists of a plurality of image sensors arranged in the main scanning direction to receive reflected light of light irradiated from a light source toward the original or the subsequent shading roller, wherein the opposing surface of the CIS including the subsequent image sensor array that faces the conveying path is inclined with respect to a horizontal plane so as to face upstream and upward of the conveying path. Effect of the Invention

[0011] According to the invention of claim 1, the acquisition of shading data can be less affected by floating debris that may get between the image sensor and the shading roller, compared to a case in which no grooves are provided on the arcuate surface, which is the outer peripheral surface of the shading roller. According to the invention of claim 2, even if the one-side arcuate surface read data is affected by a foreign object, shading data in which the influence of the foreign object is reduced can be obtained based on the one-side arcuate surface read data. According to the invention of claim 3, it is possible to obtain shading data based on the second arcuate surface reading data, which reduces the influence of foreign matter on the second arcuate surface reading data, and to determine whether or not maintenance of the second white reference arcuate surface is required. According to the invention as set forth in claim 4, foreign matter adhering to the facing surface of the CIS including the subsequent image sensor array, facing the transport path, can be scraped off by the document. [Brief description of the drawings]

[0012] [Figure 1] 1 is a schematic diagram illustrating a configuration of an image reading apparatus according to an embodiment of the present invention. [Diagram 2]FIG. 2 is a cross-sectional view in the short side direction of a first shading roller according to the present embodiment. [Diagram 3] FIG. 2 is a perspective view of a first shading roller according to the present embodiment. [Figure 4] FIG. 4 is a cross-sectional view in the short side direction of a second shading roller according to the present embodiment. [Diagram 5] FIG. 2 is a schematic diagram of a processor configuration. [Figure 6] 11A and 11B are diagrams illustrating the movement of floating dust with the rotation of a shading roller. [Figure 7] FIG. 11 is a diagram showing an example of shading data. [Figure 8] FIG. 13 is a diagram showing an example of one-side arc surface read data. [Figure 9] FIG. 13 is a diagram showing an example of other side arc surface read data. [Figure 10] FIG. 13 is a schematic diagram illustrating the configuration of an image reading device according to a modified embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] FIG. 1 is a schematic diagram of the configuration of an image reading device 10 according to this embodiment. In each drawing in this specification, the X-axis direction indicates the main scanning direction, the Y-axis direction indicates the sub-scanning direction, and the Z-axis direction indicates the height direction. The image reading device 10 is a device that optically reads an original, which is a medium such as paper (in other words, performs a scanning process) and forms image data representing the original. The image reading device 10 is, for example, a scanner or a multifunction device having a scanning function. As shown in FIG. 1, the image reading device 10 is configured to include an original feed roller 12, a CIS 18 including a light source 14 and an image sensor array 16, a shading roller 20, a memory 22, and a processor 24.

[0014] The document feed rollers 12 transport the medium along the medium transport path P. In the example of Fig. 1, a plurality of pairs of document feed rollers 12 are provided, and each pair of document feed rollers 12 transports the medium from the left side to the right side by rotating with the medium sandwiched in the nip portion.

[0015] For scanning processing, the light source 14 emits light toward the original or the shading roller 20. A plurality of light sources 14 may be provided along the X-axis.

[0016] The image sensor array 16 is composed of a plurality of (e.g., a dozen or so) image sensors arranged in the X-axis direction. Each image sensor receives reflected light of light irradiated from the light source 14 toward the original or the shading roller 20, and outputs a pixel value based on the received reflected light. The image sensor array 16 is disposed opposite the shading roller 20 across the transport path P.

[0017] The shading roller 20 is a columnar part that extends in the longitudinal direction generally along the image sensor array 16. The shading roller 20 is provided opposite the image sensor array 16 with the transport path P interposed therebetween.

[0018] A white reference surface is provided on the outer peripheral surface of the shading roller 20 to obtain shading data for shading correction. The shading correction is a correction for suppressing fluctuations in pixel values ​​output by the image sensor array 16 caused by differences in the light quantities of the light sources 14 (including differences between light sources 14 and differences due to changes over time in the same light source 14) or differences in sensitivity of each image sensor (including differences between image sensors and differences due to changes over time in the same image sensor). The shading data is formed by pixel values ​​output by the image sensor array 16 after receiving light reflected from the white reference surface of the shading roller 20 by the light from the light source 14.

[0019] 1, the image reading device 10 according to the present embodiment has two combinations of a CIS 18 and a shading roller 20. That is, the image reading device 10 has a CIS 18a including an image sensor array 16a that receives reflected light from a first surface (e.g., a back surface) of a document or a shading roller 20a, a shading roller 20a for generating shading data for the CIS 18a, a CIS 18b including an image sensor array 16b as a subsequent image sensor array that receives reflected light from a second surface (e.g., a front surface) of a document or a shading roller 20b, and a shading roller 20b as a subsequent shading roller for generating shading data for the CIS 18b.

[0020] The combination of CIS 18b and shading roller 20b is provided downstream of the combination of CIS 18a and shading roller 20a on the transport path P. In other words, image sensor array 16b is provided downstream of image sensor array 16a on the transport path P, and shading roller 20b is provided downstream of shading roller 20a on the transport path P.

[0021] In this embodiment, the CIS 18a and the CIS 18b have the same structure, and the shading roller 20a and the shading roller 20b also have approximately the same structure, as described below.

[0022] When a document passes between the CIS 18 and the shading roller 20, foreign matter (such as paper powder) may come out of the document. It can be said that foreign matter from the document is more likely to come out the further upstream the transport path P. If such foreign matter adheres to the opposing surface of the CIS 18 facing the transport path P (for example, the transparent glass plate covering the image sensor array 16a), the effect of the foreign matter appears in the pixel value output by the image sensor array 16. Therefore, in this embodiment, the CIS 18a (i.e., the image sensor array 16a) on the upstream side of the transport path P is provided above the transport path P. In other words, the shading roller 20a on the upstream side of the transport path P is provided below the CIS 18a (i.e., the image sensor array 16a) and the transport path P. As a result, foreign matter from the document falls downward due to the action of gravity, and the adhesion of foreign matter to the opposing surface of the CIS 18a is suppressed. In addition, since the shading roller 20a is located below the transport path P, there is a high possibility that foreign matter from the document falls on the shading roller 20a, and the influence of the foreign matter appears in the shading data. However, in this embodiment, as described later, it is possible to reduce the influence of the foreign matter appearing in the shading data acquired using the shading roller 20a.

[0023] In this embodiment, the original document is not inverted while being transported along the transport path P, so CIS 18a is above the shading roller 20a (in other words, the shading roller 20a is below the CIS 18a), and therefore CIS 18b, which reads a different side of the original document from CIS 18a, is inevitably located below the shading roller 20b (in other words, the shading roller 20b is located above the CIS 18a).

[0024] The image reading device 10 may have only one combination of the CIS 18 and the shading roller 20. In this case, the shading roller 20 may be located below the CIS 18.

[0025] In this specification, when there is no particular distinction between light source 14a and light source 14b, they will simply be referred to as light source 14, when there is no particular distinction between image sensor array 16a and image sensor array 16b, they will simply be referred to as image sensor array 16, when there is no particular distinction between CIS 18a and CIS 18b, they will simply be referred to as CIS 18, and when there is no particular distinction between shading roller 20a and shading roller 20b, they will simply be referred to as shading roller 20.

[0026] Fig. 2 is a conceptual diagram showing a schematic shape of a lateral cross section of the shading roller 20a. Fig. 3 is a perspective view of the shading roller 20a according to this embodiment. Fig. 4 is a conceptual diagram showing a schematic shape of a lateral cross section of the shading roller 20b. The shading roller 20 is rotatable about a rotation axis R extending in the longitudinal direction. The outer peripheral surface of the shading roller 20 has various faces as described below, and since the shading roller 20 is rotatable about the rotation axis R, the face facing the image sensor array 16 (or the light source 14) can be changed.

[0027] 2 or 4, the shading roller 20 has a first white reference arcuate surface 30 on its outer circumferential surface, which is white, has an arc-shaped cross section in the short side direction, and extends in the longitudinal direction. In this embodiment, the cross-sectional shape of the first white reference arcuate surface 30 is an arcuate shape centered on the rotation axis R.

[0028] The shading roller 20 has a groove 32 extending in the longitudinal direction on its outer circumferential surface, which is located preceding the first white reference arcuate surface 30 in the rotation direction of the shading roller 20. The groove 32 is a portion of the outer circumferential surface (in other words, the bottom surface of the groove 32) that is closer to the rotation axis R than the first white reference arcuate surface 30. In other words, the diameter from the rotation axis R to the bottom surface of the groove 32 is shorter than the diameter from the rotation axis R to the first white reference arcuate surface 30.

[0029] In this embodiment, the shading roller 20 has a second white reference arcuate surface 34 on its outer circumferential surface, which is located ahead of the groove portion 32 in the rotation direction of the shading roller 20, is white, has an arc-shaped short-side cross section, and extends in the longitudinal direction. The cross-sectional shape of the second white reference arcuate surface 34 may also be an arc shape centered on the rotation axis R. In other words, the diameter from the rotation axis R to the first white reference arcuate surface 30 and the diameter from the rotation axis R to the second white reference arcuate surface 34 are the same, and both diameters are longer than the diameter from the rotation axis R to the bottom surface of the groove portion 32.

[0030] Furthermore, the shading roller 20 may have a plurality of planes on the outer peripheral surface in addition to the first white reference arc surface 30 and the second white reference arc surface 34. For example, as shown in FIG. 2 or FIG. 4, in this embodiment, the shading roller 20 has three planes on the outer peripheral surface in addition to the first white reference arc surface 30 and the second white reference arc surface 34. The first plane 36 and the second plane 38 are used as dirt surfaces. When a medium passes between the image sensor array 16 and the shading roller 20, foreign matter may come out of the medium and adhere to the shading roller 20. In order to prevent such foreign matter from adhering to the first white reference arc surface 30 and the second white reference arc surface 34, the first plane 36 or the second plane 38 is made to face the image sensor array 16 when the medium passes between the image sensor array 16 and the shading roller 20. The black plane 40 is black, and is used to improve the accuracy of detecting the position of the document transported along the transport path P by facing the black plane 40 to the image sensor array 16, for example.

[0031] 2 or 4, in this embodiment, on the outer peripheral surface of the shading roller 20, the second white reference arcuate surface 34, the groove portion 32, the first white reference arcuate surface 30, the first plane 36, the second plane 38, and the black plane 40 are arranged in this order in the opposite direction to the rotation direction of the shading roller 20. In other words, as the shading roller 20 rotates, the surface facing the image sensor array 16 is switched in the above order.

[0032] When viewed from the negative side in the X-axis direction, the shading roller 20a rotates clockwise, as shown by the arrow in Fig. 2. On the other hand, when viewed from the negative side in the X-axis direction, the shading roller 20b rotates counterclockwise, as shown by the arrow in Fig. 4. Therefore, when viewed from the negative side in the X-axis direction, the arrangement order of the second white reference arcuate surface 34, the groove portion 32, the first white reference arcuate surface 30, the first plane 36, the second plane 38, and the black plane 40 along the circumferential direction is reversed between the shading roller 20a and the shading roller 20b.

[0033] In this embodiment, the distance from the rotation axis R to the first white reference arc surface 30 and the distance from the rotation axis R to the second white reference arc surface 34 are the same as the distance from the rotation axis R to the transport path P (see FIG. 1). As described above, the amount of light received by each image sensor included in the image sensor array 16 varies depending on the distance between the image sensor and the outer circumferential surface of the shading roller 20 or the original, and thus, shading data can be obtained by making the distance from each image sensor to the original and the distance from each image sensor to the outer circumferential surface of the shading roller 20 the same.

[0034] On the other hand, the distance from the rotation axis R to each of the first plane 36, the second plane 38, and the black plane 40 is smaller than the distance from the rotation axis R to the transport path P. As a result, by arranging any one of the first plane 36, the second plane 38, and the black plane 40 to face the image sensor array 16, interference between the medium transported along the transport path P and the shading roller 20 can be suppressed.

[0035] 1, the memory 22 includes, for example, a hard disk drive (HDD), a solid state drive (SSD), an embedded multi media card (eMMC), a read only memory (ROM), a random access memory (RAM), etc. The memory 22 stores an image reading program for operating each unit of the image reading device 10.

[0036] 5 is a schematic diagram of the configuration of the processor 24. The processor 24 performs the functions of a read data acquisition section 50, a shading data acquisition section 52, and an image data formation section 54 according to an image reading program stored in the memory 22.

[0037] The read data acquisition unit 50 rotates the shading roller 20 so that the first white reference arcuate surface 30 of the shading roller 20 faces the image sensor array 16. In this state, the read data acquisition unit 50 causes the light source 14 to irradiate the first white reference arcuate surface 30, and acquires data indicating pixel values ​​output by each image sensor included in the image sensor array 16, the data being obtained by the image sensor array 16 receiving the light reflected from the first white reference arcuate surface 30. In this specification, this data is referred to as first arcuate surface read data.

[0038] In this embodiment, a groove 32 is provided on the outer peripheral surface of the shading roller 20a, which is provided below the transport path P, at a position preceding the first white reference arcuate surface 30 in the rotation direction of the shading roller 20a, reducing the possibility that the first arcuate surface read data will be affected by floating dust. This will be described with reference to FIG. 6.

[0039] For example, consider a case where the initial state of the shading roller 20a (here, the state means the rotation angle) is a state in which the second white reference arc surface 34 faces the image sensor array 16a, as shown in FIG. 6(a). Here, assume that stray dust F is placed on the second white reference arc surface 34. If the image sensor array 16a receives reflected light from the second white reference arc surface 34 in this state, the pixel value output by any of the image sensors included in the image sensor array 16a will be affected by the stray dust F. That is, if the image sensor array 16a obtains shading data by receiving reflected light from the second white reference arc surface 34 in this state, the shading data will be affected by the stray dust F.

[0040] As shown in Fig. 6(b), the read data acquisition unit 50 rotates the shading roller 20a around the rotation axis R. Since the stray dust F is not a foreign object attached to the second white reference arcuate surface 34, even when the shading roller 20a rotates, the stray dust F slides on the second white reference arcuate surface 34 and remains in place (in the example of Fig. 6(b), in a position facing the image sensor array 16a). In the state of Fig. 6(b), the stray dust F is located at the rear end of the second white reference arcuate surface 34 in the rotation direction.

[0041] When the shading roller 20a rotates further from the state shown in Fig. 6(b), the stray dust F falls from the second white reference arc surface 34 into the groove portion 32 due to the action of gravity, as shown in Fig. 6(c). However, even after falling into the groove portion 32, the stray dust F may slide along the bottom surface of the groove portion 32 as the shading roller 20a rotates, and remain there (at a position facing the image sensor array 16a in the example of Fig. 6(c)).

[0042] As the shading roller 20a rotates further from the state shown in Fig. 6(c), eventually, as shown in Fig. 6(d), the stray dust F comes into contact with the side wall on the rear side in the rotation direction of the groove portion 32. After the stray dust F comes into contact with the side wall of the groove portion 32, as the shading roller 20a rotates, the stray dust F is pushed by the side wall and moves in the rotation direction.

[0043] As the side walls of the grooves 32 push the stray dust, when the shading roller 20a rotates to a position where the first white reference arcuate surface 30 faces the image sensor array 16a as shown in Fig. 6(e), the stray dust F is no longer in a position facing the image sensor array 16a. Therefore, the influence of the stray dust F on the first arcuate surface read data acquired by the read data acquisition unit 50 can be reduced. If the shading roller 20a rotates further from the state shown in Fig. 6(e), the stray dust F will detach from the surface of the shading roller 20a due to the action of gravity and fall below the shading roller 20a.

[0044] The read data acquisition unit 50 may repeatedly output pixels related to the reflected light from the first white reference arcuate surface 30 for each image sensor while rotating the shading roller 20, and acquire a plurality of pixel values ​​in time series for each image sensor. The read data acquisition unit 50 may calculate a representative pixel value (e.g., average pixel value) of each image sensor based on the plurality of pixel values ​​in time series acquired by each image sensor, and may use the representative pixel value of each image sensor as the first arcuate surface read data. This makes it possible to reduce the influence of foreign matter on some pixel values ​​among the plurality of pixel values ​​in time series for a certain image sensor, and noise suddenly output by the image sensor, in the first arcuate surface read data.

[0045] In this embodiment, the cross-sectional shape of the first white reference arc surface 30 is a semicircle centered on the rotation axis R, so that the distance between the image sensor and the first white reference arc surface 30 does not change even when the shading roller 20 is rotated.

[0046] The shading data acquisition unit 52 acquires shading data based on the first arcuate surface read data acquired by the read data acquisition unit 50. In the basic embodiment, the shading data acquisition unit 52 can use the first arcuate surface read data itself as the shading data.

[0047] An example of shading data is shown in FIG. 7. In FIG. 7 (as well as in FIG. 8 and FIG. 9 described later), the horizontal axis represents the X-axis direction, i.e., the main scanning direction (of the image sensors arranged in the X-axis direction), and the vertical axis represents the pixel value output by each image sensor. The pixel value is, for example, a luminance value. High-frequency noise caused by the image sensor may be superimposed on the shading data. In FIG. 7, the state in which such high-frequency noise is superimposed is represented by a thick line. The high-frequency noise caused by the image sensor is also superimposed on the image data obtained by the image sensor array 16 actually reading the document. Therefore, the superimposition of high-frequency noise on the shading data may enable more suitable shading correction.

[0048] The image data forming unit 54 irradiates light from the light source 14 onto the original transported along the transport path P, and obtains original reading data obtained by the image sensor array 16 receiving the light reflected from the original.

[0049] Further, the image data forming unit 54 corrects the acquired original scan data based on the shading data (see FIG. 7) acquired by the shading data acquiring unit 52, and acquires corrected original scan data. A conventional method can be adopted for correcting the original scan data based on the shading data, and detailed explanations are omitted here. For example, in the shading data of FIG. 7, the pixel values ​​at both ends are lower than the center in the main scanning direction, so the image data forming unit 54 corrects the original scan data based on the shading data so as to raise the pixel values ​​at both ends compared to the center in the main scanning direction.

[0050] Furthermore, the image data forming unit 54 forms image data corresponding to the document based on the corrected document read data. The formed image data is stored in the memory 22, or is transmitted to a device (such as a personal computer or a server) outside the image reading device 10 by a communication unit (not shown) included in the image reading device 10.

[0051] As described above, according to this embodiment, the influence of floating dust in the shading data based on the first arcuate surface read data can be reduced. However, there are cases where the influence of foreign matter cannot be completely removed from the first arcuate surface read data. For example, there are cases where floating dust happens to get between the first white reference arcuate surface 30 and the image sensor array 16 at the timing when the image sensor array 16 receives the reflected light from the first white reference arcuate surface 30, or there is dust (fixed dust) or dirt adhered to the first white reference arcuate surface 30. In such cases, if the shading data is obtained based only on the first arcuate surface read data, the influence of the foreign matter will also appear in the shading data.

[0052] Therefore, in order to reduce the influence of foreign matter on the shading data, the shading data acquisition unit 52 may acquire shading data based on both the first arc surface reading data and the second arc surface reading data indicating the pixel values ​​output by each image sensor obtained by the image sensor array 16 receiving reflected light from the second white reference arc surface 34.

[0053] Specifically, first, the read data acquisition unit 50 rotates the shading roller 20 so that the second white reference arc surface 34 of the shading roller 20 faces the image sensor array 16. In this state, the read data acquisition unit 50 causes the light source 14 to irradiate the second white reference arc surface 34, and acquires data indicating pixel values ​​output by each image sensor included in the image sensor array 16, the data being obtained by the image sensor array 16 receiving the light reflected from the second white reference arc surface 34. In this specification, this data is referred to as second arc surface read data.

[0054] As in the case of acquiring the first arcuate surface read data, the read data acquiring unit 50 may repeatedly output pixels relating to the reflected light from the second white reference arcuate surface 34 for each image sensor while rotating the shading roller 20, and acquire a plurality of pixel values ​​in time series for each image sensor. Then, based on the plurality of pixel values ​​in time series acquired by each image sensor, a representative pixel value (e.g., average pixel value) of the image sensor may be calculated, and the representative pixel value of each image sensor may be set as the second arcuate surface read data.

[0055] Next, the read data acquisition unit 50 acquires the first arcuate surface read data as described above.

[0056] In this specification, one of the first arcuate surface read data and the second arcuate surface read data is referred to as one-side arcuate surface read data, and the other of the first arcuate surface read data and the second arcuate surface read data is referred to as other-side arcuate surface read data.

[0057] Fig. 8 shows an example of the second arcuate surface read data as the one-side arcuate surface read data, and Fig. 9 shows an example of the first arcuate surface read data as the other-side arcuate surface read data. In Fig. 8 or 9, the protruding parts protruding in the vertical direction are the influence of foreign matter. In particular, for the shading roller 20a, as described above, the influence of floating dust may be reduced in the first arcuate surface read data due to the action of the groove portion 32, and the second arcuate surface read data may be more susceptible to the influence of foreign matter than the first arcuate surface read data.

[0058] The shading data acquisition unit 52 analyzes the one-side arc surface read data to identify an abnormal pixel value that is a pixel value affected by a foreign object that exists between the first white reference arc surface 30 (when the one-side arc surface read data is the first arc surface read data) or the second white reference arc surface 34 (when the one-side arc surface read data is the second arc surface read data) and the image sensor array when acquiring the one-side arc surface read data. The abnormal pixel value can be identified by a known method. For example, the shading data acquisition unit 52 can identify the abnormal pixel value by subtracting filtered read data obtained by applying a low-pass filter to the one-side arc surface read data from the one-side arc surface read data. In the example of FIG. 8, the pixel value of the image sensor Sa, the pixel value of the image sensor Sb, and the pixel value of the image sensor Sc are identified as the abnormal pixel value.

[0059] Then, the shading data acquisition unit 52 acquires shading data by replacing the identified abnormal pixel value in the one-side arc surface read data with the pixel value of the image sensor that corresponds to the abnormal pixel value and is included in the other-side arc surface read data. In the example of Fig. 8 and Fig. 9, the shading data acquisition unit 52 replaces the pixel values ​​of the image sensor Sa, the pixel values ​​of the image sensor Sb, and the pixel values ​​of the image sensor Sc in the one-side arc surface read data shown in Fig. 8 with the pixel values ​​of the image sensor Sa, the pixel values ​​of the image sensor Sb, and the pixel values ​​of the image sensor Sc in the other-side arc surface read data, respectively. This allows shading data (see Fig. 7) in which the influence of foreign matter is reduced to be acquired.

[0060] The one-side arc surface read data may be the first arc surface read data. In this case, the shading data acquisition unit 52 identifies an abnormal pixel value in the first arc surface read data (see FIG. 9) as the one-side arc surface read data. In the example of FIG. 9, the pixel values ​​of the image sensor Sd and the pixel values ​​of the image sensor Se are identified as the abnormal pixel values. Then, the shading data acquisition unit 52 replaces the pixel values ​​of the image sensor Sd and the pixel values ​​of the image sensor Se in the first arc surface read data as the one-side arc surface read data shown in FIG. 9 with the pixel values ​​of the image sensor Sd and the pixel values ​​of the image sensor Se in the second arc surface read data as the other-side arc surface read data. This also similarly acquires shading data (see FIG. 7) in which the influence of foreign matter is reduced.

[0061] In this embodiment, the shading data acquisition unit 52 uses the second arcuate surface read data, which is more susceptible to the influence of foreign matter, as the one-side arcuate surface read data. That is, the shading data acquisition unit 52 analyzes the second arcuate surface read data to identify abnormal pixel values, and acquires shading data by replacing the identified abnormal pixel values ​​with pixel values ​​of the image sensor that are included in the first arcuate surface read data and correspond to the abnormal pixel values.

[0062] As described above, the shading data acquisition unit 52 identifies abnormal pixel values ​​in the one-side arc surface read data. Abnormal pixel values ​​can also be caused by foreign matter or dirt adhering to the surface corresponding to the one-side arc surface read data (in this case, the second white reference arc surface 34). Therefore, by using the second arc surface read data as the one-side arc surface read data, identifying abnormal pixel values ​​from the one-side arc surface read data also detects foreign matter or dirt adhering to the second white reference arc surface 34.

[0063] Here, when foreign matter or dirt has adhered to a certain extent to the outer peripheral surface of the shading roller 20, it is desirable to perform maintenance of the shading roller 20. Therefore, in this embodiment, the second arcuate surface read data, which is more susceptible to foreign matter, is used as one-side arcuate surface read data, and foreign matter or dirt adhered to the second white reference arcuate surface 34, which is more susceptible to foreign matter and dirt, is detected, thereby making it possible to notify the user (including the administrator) of the image reading device 10 at an earlier stage that maintenance of the shading roller 20 is necessary.

[0064] As described above, when acquiring shading data, the first white reference arc surface 30 or the second white reference arc surface 34 of the shading roller 20 faces the image sensor array 16, but when the image sensor array 16 reads the original, the other surface of the shading roller 20 faces the image sensor array 16. Below, the surface of the shading roller 20 that faces the image sensor array 16 (in other words, the original passing through the transport path P) when the image sensor array 16 reads the original will be described.

[0065] The image reading device 10 according to the present embodiment is capable of single-sided scanning, which reads only one side of a document, and double-sided scanning, which reads both sides of a document. In the present embodiment, in the case of single-sided scanning, image data is formed by the CIS 18b.

[0066] In the case of single-sided scanning, when reading an original, the read data acquisition unit 50 faces the first plane 36 of the shading roller 20a to the original, and also faces the first plane 36 of the shading roller 20b to the original. In the case of double-sided scanning, when reading an original, the read data acquisition unit 50 faces the first plane 36 or the second plane 38 of the shading roller 20a to the original, and also faces the second plane 38 of the shading roller 20b to the original.

[0067] The shading data may be acquired immediately before the scanning process of the document. When the acquisition of the shading data is completed, the shading roller 20 is in a state where the first white reference arc surface 30 faces the image sensor array 16. From that state, the read data acquisition unit 50 rotates the shading roller 20 so that a predetermined surface faces the image sensor array 16, and then the scanning process of the document starts. Here, on the outer peripheral surface of the shading roller 20, the first plane 36 is located adjacent to the first white reference arc surface 30. Therefore, by making the surface facing the document (in other words, the image sensor array 16) the first plane 36 when reading the document, the amount of rotation of the shading roller 20 can be reduced. In other words, the time from the acquisition of the shading data to the start of the scanning process of the document can be shortened.

[0068] Fig. 10 is a schematic diagram of an image reading device 10' according to a modified embodiment. The components of the image reading device 10' are similar to those of the image reading device 10 shown in Fig. 1. In the image reading device 10' as well, the document is transported along the transport path P generally from left to right.

[0069] In the image reading device 10', the transport path P is inclined with respect to the horizontal plane (XY plane), and accordingly, the facing surface of the CIS 18 facing the transport path P is also inclined with respect to the horizontal plane. In particular, in the image reading device 10', the facing surface of the CIS 18b including the image sensor array 16b, which is the subsequent image sensor array, facing the transport path P is inclined with respect to the horizontal plane so as to face the upstream side and upward of the transport path P.

[0070] The facing surface of CIS 18b is inclined so as to face the upstream side and upward of the transport path P, so that the leading edge in the transport direction of the document transported along the transport path P can abut against the facing surface of CIS 18b. As a result, even if foreign matter such as paper powder adheres to the facing surface of CIS 18b, the foreign matter can be scraped off by the document.

[0071] Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the spirit of the present invention.

[0072] In the above embodiment, the processor refers to a processing device in a broad sense, and includes at least one of a general-purpose processing device (e.g., a CPU (Central Processing Unit)) and a dedicated processing device (e.g., a GPU (Graphics Processing Unit), an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a programmable logic device). The processor may not be a single processing device, but may be a device formed by the cooperation of multiple processing devices located at physically separate locations.

[0073] (Additional Note) (((1))) a shading roller having a columnar shape extending in a longitudinal direction and rotatable around a rotation axis extending in the longitudinal direction, the shading roller having, on an outer peripheral surface thereof, a first white reference arc surface which is white and has an arc-shaped short-side cross section and extends in the longitudinal direction, and a groove portion which is located preceding the first white reference arc surface in the rotation direction of the shading roller and extends in the longitudinal direction; an image sensor array, which is provided above the shading roller and faces the shading roller across a document transport path, and which receives reflected light of light irradiated from a light source toward the document or the shading roller, and which is composed of a plurality of image sensors arranged in a main scanning direction; A processor; Equipped with The processor, acquiring shading data based on first arcuate surface reading data indicating pixel values ​​output by each of the image sensors, the pixel values ​​being obtained by the image sensor array receiving the reflected light from the first white reference arcuate surface; based on the shading data, correcting document read data obtained by the image sensor array receiving the reflected light from the document to obtain corrected document read data; forming image data corresponding to the document based on the corrected document read data; 1. An image reading apparatus comprising: (((2))) the shading roller further includes, on its outer peripheral surface, a second white reference arc surface that is located ahead of the groove portion in a rotation direction of the shading roller, is white, has an arc-shaped cross section in a short side direction, and extends in the longitudinal direction; The processor, by analyzing one-side arc surface read data indicating pixel values ​​output by each of the image sensors, the one-side arc surface read data being obtained by the image sensor array receiving the reflected light from one of the first white reference arc surface and the second white reference arc surface, an abnormal pixel value being the pixel value affected by a foreign object that existed between the image sensor array and one of the first white reference arc surface and the second white reference arc surface when the one-side arc surface read data was obtained; the shading data is acquired by replacing the identified abnormal pixel value with a pixel value of the image sensor corresponding to the abnormal pixel value, the pixel value being included in other-side arc surface read data indicating pixel values ​​output by each of the image sensors, the pixel value being obtained by the image sensor array receiving the reflected light from the other of the first white reference arc surface and the second white reference arc surface; The image reading device according to (((1))) is characterized in that (((3))) The processor, by analyzing second arcuate surface read data indicating pixel values ​​output by each of the image sensors, which is obtained by the image sensor array receiving the reflected light from the second white reference arcuate surface, identifying abnormal pixel values ​​which are pixel values ​​affected by foreign matter present between the second white reference arcuate surface and the image sensor array when the second arcuate surface read data is obtained; acquiring the shading data by replacing the identified abnormal pixel value with a pixel value of the image sensor that is included in the first arcuate surface read data and corresponds to the abnormal pixel value; The image reading device according to (((2))) is characterized in that (((4))) a trailing shading roller that is provided downstream of the shading roller in the conveying path and has a columnar shape extending in the longitudinal direction; a subsequent image sensor array that is provided downstream of the image sensor array in the transport path, faces the subsequent shading roller across the transport path, and is provided below the subsequent shading roller, and is made up of a plurality of image sensors that are arranged in a main scanning direction and receive reflected light of light irradiated from a light source toward the original or the subsequent shading roller; Further equipped with a surface of the CIS including the subsequent image sensor array facing the transport path is inclined with respect to a horizontal plane so as to face the upstream side and upward of the transport path; 2. The image reading device according to claim 1, wherein the image reading device is a digital camera.

[0074] According to the invention related to (((1))), the acquisition of shading data can be less affected by floating debris that may get between the image sensor and the shading roller, compared to a case in which no grooves are provided on the arcuate surface, which is the outer peripheral surface of the shading roller. According to the invention relating to (((2))), even if the one-side arc surface read data is affected by a foreign matter, shading data in which the influence of the foreign matter is reduced can be obtained based on the one-side arc surface read data. According to the invention relating to (((3))), it is possible to obtain shading data based on the second arcuate surface reading data, which reduces the influence of foreign matter on the second arcuate surface reading data, and to determine whether or not maintenance of the second white reference arcuate surface is required. According to the invention related to (((4))), foreign matter adhering to the facing surface of the CIS including the subsequent image sensor array, which faces the transport path, can be scraped off by the document. [Explanation of symbols]

[0075] 10,10' image reading device, 12 document feed roller, 14 light source, 16 image sensor array, 18 CIS, 20 shading roller, 22 memory, 24 processor, 30 first white reference arc surface, 32 groove portion, 34 second white reference arc surface, 36 first plane, 38 second plane, 40 black plane, 50 read data acquisition section, 52 shading data acquisition section, 54 image data formation section.

Claims

1. a shading roller having a columnar shape extending in a longitudinal direction and rotatable around a rotation axis extending in the longitudinal direction, the shading roller having, on an outer peripheral surface thereof, a first white reference arc surface which is white and has an arc-shaped short-side cross section and extends in the longitudinal direction, and a groove portion which is located preceding the first white reference arc surface in the rotation direction of the shading roller and extends in the longitudinal direction; an image sensor array, which is provided above the shading roller and faces the shading roller across a document transport path, and which receives reflected light of light irradiated from a light source toward the document or the shading roller, and which is composed of a plurality of image sensors arranged in a main scanning direction; A processor; Equipped with The processor, acquiring shading data based on first arcuate surface reading data indicating pixel values ​​output by each of the image sensors, the pixel values ​​being obtained by the image sensor array receiving the reflected light from the first white reference arcuate surface; based on the shading data, correcting document read data obtained by the image sensor array receiving the reflected light from the document to obtain corrected document read data; forming image data corresponding to the document based on the corrected document read data; 1. An image reading apparatus comprising:

2. the shading roller further includes, on its outer peripheral surface, a second white reference arc surface that is located ahead of the groove portion in a rotation direction of the shading roller, is white, has an arc-shaped cross section in a short side direction, and extends in the longitudinal direction; The processor, by analyzing one-side arc surface read data indicating pixel values ​​output by each of the image sensors, the one-side arc surface read data being obtained by the image sensor array receiving the reflected light from one of the first white reference arc surface and the second white reference arc surface, an abnormal pixel value being the pixel value affected by a foreign object that existed between the image sensor array and one of the first white reference arc surface and the second white reference arc surface when the one-side arc surface read data was obtained; the shading data is acquired by replacing the identified abnormal pixel value with a pixel value of the image sensor corresponding to the abnormal pixel value, the pixel value being included in other-side arc surface read data indicating pixel values ​​output by each of the image sensors, the pixel value being obtained by the image sensor array receiving the reflected light from the other of the first white reference arc surface and the second white reference arc surface; 2. The image reading apparatus according to claim 1, wherein the image reading apparatus comprises:

3. The processor, by analyzing second arcuate surface read data indicating pixel values ​​output by each of the image sensors, the second arcuate surface read data being obtained by the image sensor array receiving the reflected light from the second white reference arcuate surface, an abnormal pixel value being the pixel value affected by a foreign object present between the second white reference arcuate surface and the image sensor array when the second arcuate surface read data was obtained; and acquiring the shading data by replacing the identified abnormal pixel value with a pixel value of the image sensor that is included in the first arcuate surface read data and corresponds to the abnormal pixel value.

3. The image reading apparatus according to claim 2, wherein the image reading apparatus comprises:

4. a trailing shading roller that is provided downstream of the shading roller in the conveying path and has a columnar shape extending in the longitudinal direction; a subsequent image sensor array that is provided downstream of the image sensor array in the transport path, faces the subsequent shading roller across the transport path, and is provided below the subsequent shading roller, and is made up of a plurality of image sensors that are arranged in a main scanning direction and receive reflected light of light irradiated from a light source toward the original or the subsequent shading roller; Further equipped with a surface of the CIS including the subsequent image sensor array facing the transport path is inclined with respect to a horizontal plane so as to face the upstream side and upward of the transport path; 4. The image reading apparatus according to claim 1, wherein the image reading apparatus is a scanning apparatus.

Images