Image reading device

Abstract

To provide a technique to appropriately make a correction to a part near a rear end of a read image.SOLUTION: An image reading device 10 comprises: an image reading unit 107 for reading a document on a platen glass 110; one or more sliders 301, 302 for delivering reflected light from the document to the image reading unit; a first shading sheet 101; a second shading sheet 102 that is provided at a position different from the first shading sheet 101 in the direction of movement of the sliders 301, 302; and a control unit 400 that makes a correction to a read image. The control unit calculates a first correction value based on a read image of the first shading sheet 101, and a second correction value based on a read image of the second shading sheet 102, and makes a correction to the read images on the basis of both or one of the first correction value and the second correction value.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to image reading techniques, and more particularly, to shading correction. [Background technology]

[0002] Image reading devices (scanners) that use platen glass are known. Image reading devices generate images by reading an original document placed on the platen glass. In such cases, image unevenness may occur in the read image due to uneven light distribution in the lighting, insufficient light at the edge of the lens, variation in CCD (Charge Coupled Device) pixels, etc.

[0003] In order to reduce image unevenness in a scanned image, an image reading device may perform shading correction using a shading sheet. As an example, a mirror scan type scanner has a shading sheet near the standby position of the slider. The scanner reads the shading sheet with an image sensor and performs shading correction based on a correction value obtained from the read image of the shading sheet.

[0004] Regarding shading correction technology, for example, JP 2020-025206 A (Patent Document 1) discloses an image reading device including: "a first judgment unit (arithmetic processing unit) that judges whether or not there is dirt on the reference member or the reading unit based on first white data obtained by reading a reference member (shading sheet) with a reading unit (reading sensor); a creation unit (arithmetic processing unit) that, when it is determined that there is dirt by the first judgment unit, complements the first white data with second white data obtained by additionally reading the reference member with the reading unit to create ideal initial white reference data; and a completion unit (arithmetic processing unit) that complements third white data obtained by reading the reference member with the reading unit immediately before reading the image of the job, with the ideal initial white reference data created by the creation unit" (see [Abstract]). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-025206 A Summary of the Invention [Problem to be solved by the invention]

[0006] As described above, the shading sheet is provided near the standby position of the slider (near the start position of the scan). Therefore, correction using the shading sheet is suitable for correcting an image located close to the shading sheet (an image located near the start position of the scan).

[0007] However, the end position of the image reading process is on the opposite side of the platen glass from the position of the shading sheet. Therefore, the end position of the image reading process is far away from the position of the shading sheet. Also, near the rear end of the read image (near the end position of the scan), the effects of uneven light distribution of the lighting, insufficient light at the end of the lens, etc. may be significant. As a result, shading correction using a shading sheet near the standby position of the slider may not be able to sufficiently correct the rear end of the read image.

[0008] The technology disclosed in Patent Document 1 does not take the above-mentioned problems into consideration and is unable to properly correct the rear end of an image (an image near the end of scanning). Therefore, there is a need for a technology for properly correcting the rear end of a scanned image.

[0009] The present disclosure has been made in view of the above-described background, and an object of one aspect is to provide a technique for appropriately correcting the vicinity of the trailing edge of a scanned image. [Means for solving the problem]

[0010] According to one embodiment, there is provided an image reading device. The image reading device includes an image reading unit for reading an original on a platen glass, one or more sliders for delivering reflected light from the original to the image reading unit, a first shading sheet, a second shading sheet provided at a position different from the first shading sheet in the moving direction of the slider, and a control unit for correcting the read image. The control unit calculates a first correction value based on the read image of the first shading sheet and a second correction value based on the read image of the second shading sheet, and corrects the read image based on both or one of the first and second correction values.

[0011] In one aspect, correcting the read image based on both or one of the first correction value and the second correction value includes selecting either the first correction value or the second correction value, and correcting the read image based on the selected correction value.

[0012] In one aspect, selecting one of the first correction value and the second correction value includes selecting one of the first correction value and the second correction value depending on a document size.

[0013] In one aspect, the document size is the document size in the movement direction of the slider.

[0014] In one aspect, selecting either the first correction value or the second correction value includes selecting the first correction value based on the document size in the direction of movement of the slider being equal to or less than half of the maximum readable size of the image reading device.

[0015] In one aspect, correcting the read image based on both or one of the first correction value and the second correction value includes generating a third correction value based on the first correction value and the second correction value, and correcting the read image based on the third correction value.

[0016] In one aspect, the third correction value is an average value of the first correction value and the second correction value.

[0017] In one aspect, the third correction value is a correction value in the range between the first correction value and the second correction value.

[0018] In one aspect, the first shading sheet is provided at or near a reading start position of the image reading unit, and the second shading sheet is provided at or near a reading end position of the image reading unit.

[0019] In one aspect, the control unit obtains the read-out image of the first shading sheet and the read-out image of the second shading sheet at different frequencies.

[0020] In one aspect, the control unit obtains read images of the first shading sheet more frequently than read images of the second shading sheet.

[0021] In one aspect, the control unit is configured to be able to receive input of settings of reading frequencies for each of the first shading sheet and the second shading sheet, and the image reading unit obtains read images of the first shading sheet and read images of the second shading sheet at different frequencies based on the settings.

[0022] In one aspect, the control unit obtains a read image of the second shading sheet at least one of the following times: when the power is turned on, when returning from sleep, and immediately before sleep.

[0023] In one aspect, the control unit executes shading correction based on the second correction value based on a change in the current first correction value compared with a past first correction value by a predetermined threshold value or more. Effect of the Invention

[0024] According to an embodiment, the vicinity of the rear end of a scanned image can be appropriately corrected.

[0025] The above and other objects, features, aspects and advantages of the present disclosure will become apparent from the following detailed description of the present disclosure, which is to be understood in conjunction with the accompanying drawings.

Brief Description of the Drawings

[0026] [Figure 1] FIG. 8 is a diagram showing an example of the configuration of the image reading apparatus 10 according to the present embodiment as viewed from above. [Diagram 2] FIG. 11 is a diagram showing an example of a cross section of the image reading apparatus 10 according to the present embodiment as viewed from above. [Diagram 3] FIG. 14 is a diagram showing an example of a cross section of the image reading apparatus 10 according to the present embodiment as viewed from the side. [Figure 4] FIG. 17 is a diagram showing an example of the state of the reading process of the first shading sheet 101 and the second shading sheet 102. [Diagram 5] FIG. 20 is a diagram showing an example of the illuminance distribution in the main scanning direction of the read image. [Figure 6] FIG. 23 is a diagram showing an example of the processing procedure of shading correction by the image reading apparatus according to the present embodiment.

Embodiments for Carrying Out the Invention

[0027] Hereinafter, embodiments of the technical idea according to the present disclosure will be described with reference to the drawings. In the following description, the same components are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed descriptions thereof will not be repeated. Also, each embodiment and each modification example etc. may be selectively combined as appropriate.

[0028] <A. Device Configuration> FIG. 1 is a diagram showing an example of a configuration of an image reading device 10 according to the present embodiment, seen from above. The image reading device 10 reads an original document with an image sensor and generates an image of the original document. The image reading device 10 is also called a scanner. As an example, the image reading device 10 is a mirror scan type scanner. In one aspect, the image reading device 10 may be a stand-alone product. In another aspect, the image reading device 10 may be a part of an image forming device such as an MFP (Multifunction Peripheral). Therefore, the technology disclosed herein is applicable not only to image reading devices (scanners) but also to image forming devices and the like that have a reading function (scanning function).

[0029] The image reading device 10 includes a first shading sheet 101, a second shading sheet 102, a drive board 103, an angle detection sensor 104, an ADF reading slit glass 105, a document size detection sensor 106, an image sensor 107, a lens 108, and a platen glass 110.

[0030] The drive board 103 controls the operation of the image reading device 10. As an example, the drive board 103 operates a scan motor 201 (see FIG. 2), controls an illumination unit 203 (see FIG. 2), supplies power to a board of the image sensor 107, and the like.

[0031] Angle detection sensor 104 detects the opening and closing of an ADF (Automatic Document Feeder). An ADF (Automatic Document Feeder) is a device or part for automatically taking in and reading (scanning) a large amount of documents. The ADF is mounted on an MPF ​​or the like.

[0032] The ADF reading slit glass 105 is a window for reading (scanning) a document when the ADF is used. When the image reading device 10 uses the ADF, the ADF reading slit glass 105 is used instead of the platen glass 110.

[0033] The document size detection sensor 106 detects the length of the document in the sub-scanning direction 130. The document here refers to a document placed on a platen glass 110.

[0034] The image sensor 107 reads the reflected light from the original document and generates an image (image signal). More specifically, light emitted from the illumination unit 203 of the image reading device 10 is reflected by the original document. The reflected light from the original document reaches the image sensor 107 via multiple mirrors and lenses 108. The image sensor 107 receives the reflected light from the original document and generates an image of the original document. It can be said that the image sensor 107 is an image reading unit for reading the original document on the ADF reading slit glass 105 or the platen glass 110.

[0035] The lens 108 is a lens for refracting light. In one aspect, the lens 108 may be a convex lens, a concave lens, or a combination thereof.

[0036] The image sensor 107 and the lens 108 are often configured as an integrated unit. Therefore, the image sensor 107 and the lens 108 can be said to be an image reading unit for reading the document placed on the ADF reading slit glass 105 or the platen glass 110.

[0037] The platen glass 110 is a glass on which a document to be read is placed. In one aspect, both ends of the platen glass 110 in the sub-scanning direction 130 may be the start position and the end position of the image reading range of the image sensor 107.

[0038] The first shading sheet 101 is a reference plate for performing shading correction on the read image of the original. The image reading device 10 can calculate a first correction value based on the read image of the first shading sheet 101. Furthermore, the image reading device 10 can correct the image of the original based on the first correction value.

[0039] The first shading sheet 101 is provided at or near the reading start position of the image reading unit (image sensor 107). The reading start position is a position close to the standby position (home position) of the first slider 301. The reading start position is also a start position of reading the original on the platen glass 110. That is, the first shading sheet 101 is provided near the standby position (home position) of the first slider 301 (see FIG. 3). The reading start position is the start position of the range on the platen glass 110 where the image sensor 107 can acquire an image. As an example, the first shading sheet 101 may be provided at or near the end of the platen glass 110 closer to the standby position of the first slider 301 (left side of the drawing) in the sub-scanning direction 130.

[0040] The second shading sheet 102 is a reference plate for performing shading correction on the read image of the original. The image reading device 10 can calculate a second correction value based on the read image of the second shading sheet 102. Furthermore, the image reading device 10 can correct the image of the original based on the second correction value.

[0041] The second shading sheet 102 is provided at or near the reading end position of the image reading unit (image sensor 107). The reading end position is an end position of the document reading on the platen glass 110 that is far from the home position of the first slider 301. The reading end position is the end position of the document reading on the platen glass 110. The distance from the reading start position to the reading end position is the document size that can be read by the image reading device 10. That is, the second shading sheet 102 is provided near the end of the first slider 301 that is far from the home position. The reading end position is the end position of the range on the platen glass 110 where the image sensor 107 can acquire an image. As an example, the second shading sheet 102 may be provided at or near the end of the platen glass 110 that is far from the standby position of the first slider 301 (right side of the drawing) in the sub-scanning direction 130.

[0042] The above-mentioned positions of the first shading sheet 101 and the second shading sheet 102 are merely an example. The first shading sheet 101 and the second shading sheet 102 may be located apart from each other in the sub-scanning direction 130.

[0043] The image reading device 10 can select either the first correction value or the second correction value, and correct the image of the document based on the selected correction value. The image reading device 10 can also calculate a third correction value based on the first correction value and the second correction value, and correct the image of the document based on the third correction value.

[0044] The main scanning direction 120 is the reading direction (scanning direction) of the image sensor 107, and is perpendicular to the moving direction of the first slider 301. The sub-scanning direction 130 is the moving direction of the first slider 301. The first shading sheet 101 and the second shading sheet 102 are sheets that are long in the main scanning direction 120.

[0045] 2 is a diagram showing an example of a cross section of the image reading device 10 according to the present embodiment as viewed from above. The image reading device 10 includes a scan motor 201, a home sensor 202, and an illumination unit 203 in addition to the components described with reference to FIG.

[0046] The scan motor 201 drives the first slider 301 and the second slider 302 via a belt, a pulley, and / or a wire, etc. The scan motor 201 can be realized by any motor, such as a stepping motor.

[0047] The home sensor 202 is a sensor for detecting whether or not the first slider 301 is at a standby position (home position). As an example, the drive board 103 or the control unit 400 (FIG. 4) acquires a signal from the home sensor 202. The drive board 103 or the control unit 400 (FIG. 4) can determine whether or not the first slider 301 is at the standby position based on the signal.

[0048] The illumination unit 203 is provided on the first slider 301 and irradiates the original with light. The light reflected from the original reaches the image sensor 107 via a plurality of mirrors and a lens .

[0049] 3 is a diagram showing an example of a cross section of image reading device 10 according to the present embodiment as viewed from the side. Image reading device 10 includes a first slider 301, a second slider 302, a first slider rail 311, and a second slider rail 312 in addition to the configuration described with reference to FIGS.

[0050] The first slider 301 includes an illumination unit 203 and a first mirror 401 (see FIG. 4). The first slider 301 is configured to be movable in the sub-scanning direction 130 along a first slider rail 311. The illumination unit 203 illuminates the original on the platen glass 110. The first mirror 401 reflects the reflected light from the original in the direction of a second mirror 402 (see FIG. 4).

[0051] The second slider 302 includes a second mirror 402 and a third mirror 403 (see FIG. 4). The second slider 302 is configured to be movable in the sub-scanning direction 130 along a second slider rail 312. The second mirror 402 reflects the light coming from the first mirror 401 in the direction of the third mirror 403. The third mirror 403 reflects the light coming from the second mirror 402 in the direction of the lens 108 and the image sensor 107.

[0052] The first slider rail 311 is a rail that guides the first slider 301. The second slider rail 312 is a rail that guides the second slider 302.

[0053] The first slider 301 and the second slider 302 move in the sub-scanning direction 130 in conjunction with each other. State A is a state where the first slider 301 is at the left end (standby position). In this case, the second slider 302 is also located at the left end of the second slider rail 312. State B is a state where the first slider 301 is at the right end of the first slider rail 311. In this case, the second slider 302 is also located at the right end of the second slider rail 312.

[0054] The moving distances of the first slider 301 and the second slider 302 during reading (scanning) are different. Therefore, the lengths of the first slider rail 311 and the second slider rail 312 are also different. Generally, the farther the first slider 301 goes to the right side of the first slider rail 311, the greater the distance between the first slider 301 and the second slider 302. Conversely, the closer the first slider 301 goes to the left side of the first slider rail 311, the smaller the distance between the first slider 301 and the second slider 302.

[0055] <B. Procedure for shading correction> Next, with reference to FIGS. 4 and 5, the flow of shading correction by the image reading apparatus 10 will be described. Also, the necessary terms are defined as follows.

[0056] In this specification, a "document" is any medium such as paper that is read by the image reading apparatus 10. The image reading apparatus 10 can scan a document on the platen glass 110. Also, the image reading apparatus 10 can scan a document using the ADF. In this specification, an "image" includes the image data of a scanned document and an image printed on a medium. An image may also be referred to as a read image. Also, a "pixel" is the smallest unit that constitutes an image. An image is a collection of pixels.

[0057] In this specification, "reading" means scanning. The reading apparatus may also be referred to as a scanner. Also, reading a document means scanning the document. The reading position of the document is the scanning position of the document. The read image may be referred to as a scanned image.

[0058] In this specification, the "leading edge of the read image" refers to the portion (pixel) scanned at the read start position in the sub-scanning direction 130. Also, the "near the leading edge of the read image" refers to the portion (pixel) scanned near the left edge of the platen glass 110 in Fig. 4 or near the read start position. The image reading position may also be expressed as the leading edge of the read image or near the leading edge of the read image.

[0059] In this specification, the "rear end of the read image" refers to the portion (pixels) scanned at the reading end position in the sub-scanning direction 130. Also, the "near the rear end of the read image" refers to the portion (pixels) scanned near the right end of the platen glass 110 in Fig. 4 or near the reading end position. The reading position of the image may also be expressed as the rear end of the read image or near the rear end of the read image.

[0060] In this specification, the "reading start position" is the start position of scanning by the image sensor 107. The reading start position is a position close to the standby position (home position) of the first slider 301. The reading start position is also the start position of reading the original on the platen glass 110. In other words, the first shading sheet 101 is provided near the standby position (home position) of the first slider 301 (see FIG. 3).

[0061] In this specification, the "reading end position" is the end position of scanning by the image sensor 107. The reading end position is a position close to the end of the first slider 301 far from the home position. The reading end position is also the end position of reading the original on the platen glass 110. The distance from the reading start position to the reading end position is the original size that can be read by the image reading device 10. Note that the image reading device 10 does not need to scan up to the reading end position depending on the original size. When the original is half the size of the maximum reading size, the image reading device 10 may scan from the reading start position to near the center of the platen glass 110. In other words, the reading end position can be said to be the end position of the maximum readable range.

[0062] In this specification, the "correction value" includes a first correction value calculated from the read image of the first shading sheet 101. The "correction value" also includes a second correction value calculated from the read image of the second shading sheet 102. The "correction value" also includes a third correction value newly generated from the first correction value and the second correction value. In this specification, the "correction of an image" includes the correction of each pixel contained in the image.

[0063] FIG. 4 is a diagram showing an example of a reading process of the first shading sheet 101 and the second shading sheet 102. The process shown in FIG. 4 is controlled by a control unit 400 included in the image reading device 10. In one aspect, the control unit 400 may be the drive board 103. In another aspect, the control unit 400 may be a circuit separate from the drive board 103. In this case, the control unit 400 may output a control command to the drive board 103. The drive board 103 may control the scan motor 201 and the like according to the control command. The control unit 400 may include a processor, a storage, and a memory. The image reading device 10 may correct an image using one or both of the first shading sheet 101 and the second shading sheet 102.

[0064] (a. Relationship between scan position and incident light) The image reading device 10 captures reflected light from the original document into the image sensor 107 via multiple mechanical parts such as the first slider 301 and the second slider 302. Therefore, the incident light may not be incident at an ideal angle due to individual differences in the mechanical parts, assembly errors, etc. Such deviations in the incident light may cause image distortion. In addition, the angle of the reflected light from the original document changes as the position of the first slider 301 changes. In other words, when the scanning position changes, the amount of distortion also changes.

[0065] As an example, assume that the first slider 301 and the second slider 302 are at a position 410. The position 410 is a position on the leading edge side of the image, and is also a reading position of the first shading sheet 101. A curve 438 indicates the amount of light for each angle of incidence on the first mirror 401 at the position 410. The closer the angle of incidence is to the ideal angle, the greater the amount of light that reaches the first mirror 401. The ideal incident light 430 is the ideal incident light at the position 410. The incident light 435 is the actual incident light at the position 410. The deviation between the incident light 435 at the position 410 and the ideal incident light 430 is small. This is because the distance between the first slider 301 and the second slider 302 is small, and the influence of individual differences in parts, assembly errors, and the like is relatively small.

[0066] As another example, assume that the first slider 301 and the second slider 302 are at a position 420. The position 420 is a position on the rear end side of the image, and is also a reading position of the second shading sheet 102. A curve 448 shows the amount of light for each angle of incidence on the first mirror 401 at the position 420. The more ideal the angle of incidence, the greater the amount of light that reaches the first mirror 401. The ideal incident light 440 is the ideal incident light at the position 420. The incident light 445 is the actual incident light at the position 420. The deviation between the incident light 445 at the position 420 and the ideal incident light 440 is large. This is because the distance between the first slider 301 and the second slider 302 is large, and the influence of individual differences in parts, assembly errors, etc. is relatively large.

[0067] Difference 450 is the difference between the amount of light reaching first mirror 401 at position 410 and the amount of light reaching first mirror 401 at position 420. According to difference 450, the amount of light at position 420 drops significantly compared to the amount of light at position 410. This is because actual incident light 445 at position 420 deviates significantly from ideal incident light 440.

[0068] The second correction value may have a larger correction amount for each pixel than the first correction value, because the second shading sheet 102 is located on the rear end side of the image and is more affected by the deviation of the incident light than the first shading sheet 101.

[0069] Pixels near the leading edge of the image are not affected much by the shift in incident light. Therefore, for pixels located close to the leading edge of the image, correction (small correction) using the first shading sheet 101 near the leading edge of the image is suitable. For example, correction using the first shading sheet 101 near the leading edge of the image is suitable for pixels to the left of the center of the platen glass 110 in the figure (the leading edge of the image).

[0070] Conversely, pixels near the rear end of the image are significantly affected by the shift in incident light. Therefore, for pixels located close to the rear end of the image, correction (large correction) using the second shading sheet 102 near the rear end of the image is suitable. For example, for pixels to the right of the center of the platen glass 110 in the figure (the rear end side of the image), correction using the second shading sheet 102 near the rear end of the image is suitable.

[0071] In one aspect, the image reading device 10 may select whether to use the first correction value or the second correction value based on the document size and / or the type of the image, etc. The image reading device 10 may correct the image by the selected correction value.

[0072] In another aspect, the image reading device 10 may calculate a third correction value based on the first correction value and the second correction value, based on the document size and / or the type of image, etc. The third correction value may be an average value of the first correction value and the second correction value, or may be a value between the first correction value and the second correction value. The image reading device 10 may adjust the value of the third correction value, based on the ink occupancy rate of the document, etc. For example, it is assumed that a large amount of ink is used on the rear end side of the image. In this case, the image reading device 10 may bring the value of the third correction value closer to the second correction value. When calculating the third correction value, the image reading device 10 may multiply each of the first correction value and the second correction value by a coefficient, based on the ink occupancy rate of the document, etc. The image reading device 10 may correct the image using the calculated third correction value.

[0073] (b. Method using only the first shading sheet) Assume that the image reading device 10 performs shading correction on an image using the first shading sheet 101. In this case, the image reading device 10 reads the image of the first shading sheet 101 at least once. More specifically, the image sensor 107 receives reflected light from the first shading sheet 101 through the first slider 301 and the second slider 302 at the position 410. Then, the image sensor 107 generates an image of the first shading sheet 101. The control unit 400 receives the image of the first shading sheet 101 from the substrate of the image sensor 107. The control unit 400 calculates a first correction value from the image of the first shading sheet 101. When the control unit 400 obtains a plurality of images of the first shading sheet 101, the control unit 400 may adopt an average value of the correction values ​​of the respective images as the first correction value. Alternatively, the control unit 400 may adopt a correction value of a composite image of the respective images as the first correction value. When a new document is scanned, the control unit 400 performs shading correction on the read image using the first correction value.

[0074] (c. Method using only the second shading sheet) Assume that the image reading device 10 performs shading correction on an image using the second shading sheet 102. In this case, the image reading device 10 reads the image of the second shading sheet 102 at least once. More specifically, the image sensor 107 receives reflected light from the second shading sheet 102 via the first slider 301 and the second slider 302 at the position 420. Then, the image sensor 107 generates an image of the second shading sheet 102. The control unit 400 receives the image of the second shading sheet 102 from the substrate of the image sensor 107. The control unit 400 calculates a second correction value from the image of the second shading sheet 102. When the control unit 400 obtains a plurality of images of the second shading sheet 102, the control unit 400 may adopt an average value of the correction values ​​of the images as the second correction value. Alternatively, the control unit 400 may adopt a correction value of a composite image of the images as the second correction value. When a new document is scanned, the control unit 400 performs shading correction on the read image using the second correction value.

[0075] (c. How to use both shading sheets) Assume that the image reading device 10 performs shading correction on an image using a first shading sheet 101 and a second shading sheet 102. In this case, the image reading device 10 reads the image of the first shading sheet 101 at least once. Also, the image reading device 10 reads the image of the second shading sheet 102 at least once. The number of scans of the second shading sheet 102 may be less than the number of scans of the first shading sheet 101. In other words, the second shading sheet 102 may be read less frequently than the first shading sheet 101. Through the above-mentioned procedure, the control unit 400 obtains the first correction value and the second correction value.

[0076] The image reading device 10 may select whether to use the first correction value or the second correction value based on the document size and / or the type of image, etc. In this case, the image reading device 10 may correct the image using the selected correction value. Furthermore, the image reading device 10 may calculate a third correction value based on the first correction value and the second correction value based on the document size and / or the type of image, etc. In this case, the image reading device 10 may correct the image using the calculated third correction value.

[0077] As described above, the image reading device 10 according to the present embodiment includes an image reading unit (image sensor 107) for reading an original on a platen glass, one or more sliders (first slider 301 and second slider 302) for delivering reflected light from the original to the image reading unit, a first shading sheet 101, a second shading sheet 102 provided at a position different from the first shading sheet 101 in the moving direction of the sliders, and a control unit 400 for correcting the read image. The control unit 400 calculates a first correction value based on the read image of the first shading sheet 101 and a second correction value based on the read image of the second shading sheet 102. The control unit 400 also corrects the read image based on both or either of the first correction value and the second correction value.

[0078] In one aspect, correcting the read image based on both or either of the first and second correction values ​​includes selecting either the first or second correction value and correcting the read image based on the selected correction value. That is, the control unit 400 can select either the first or second correction value and correct the read image with the selected correction value. This allows the image reading device 10 to select an optimal correction value based on the document size, etc.

[0079] In another aspect, selecting one of the first correction value and the second correction value includes selecting one of the first correction value and the second correction value depending on the document size. That is, control unit 400 can select one of the first correction value and the second correction value depending on the document size.

[0080] The document size here is the document size in the movement direction of the sliders (first slider 301 and / or second slider 302). Taking FIG. 1 as an example, the document size is the size of the document in the sub-scanning direction 130.

[0081] As an example, the control unit 400 may select the first correction value based on the fact that the document size in the movement direction of the sliders (first slider 301 and / or second slider 302) is equal to or less than half the maximum readable size of the image reading device 10. When the document size is equal to or less than half the maximum readable size of the image reading device 10, the document fits within the left half of the platen glass 110 from the reading start position. Therefore, image unevenness of the document is relatively small. Therefore, the control unit 400 may correct the document image based on the first correction value (small correction amount).

[0082] As another example, the control unit 400 may select the second correction value based on the fact that the document size in the movement direction of the sliders (first slider 301 and / or second slider 302) is equal to or greater than half of the maximum readable size in the image reading device 10. When the document size is equal to or greater than half of the maximum readable size in the image reading device 10, the document will be too small to fit between the reading start position and the center of the platen glass 110. Therefore, image unevenness is likely to become large in portions of the document far from the reading start position. Therefore, the control unit 400 may correct the document image based on the second correction value (large correction amount).

[0083] In one aspect, correcting the read image based on both or one of the first and second correction values ​​may include generating a third correction value based on the first and second correction values, and correcting the read image based on the third correction value. That is, the control unit 400 may generate the third correction value based on the first and second correction values, and correct the read image based on the third correction value.

[0084] In another aspect, the third correction value may be an average value of the first correction value and the second correction value. In another aspect, the third correction value may be a correction value in a range between the first correction value and the second correction value. The control unit 400 may adjust the value of the third correction value based on the ink occupancy rate of the document, etc. For example, assume that a large amount of ink is used on the rear end side of the image. In this case, the image reading device 10 may bring the value of the third correction value closer to the second correction value. When calculating the third correction value, the image reading device 10 may multiply each of the first correction value and the second correction value by a coefficient based on the ink occupancy rate of the document, etc. The image reading device 10 may correct the image by the calculated third correction value.

[0085] In one aspect, the control unit 400 may acquire the read image of the first shading sheet 101 and the read image of the second shading sheet 102 at different frequencies. As one example, the control unit 400 may acquire the read image of the first shading sheet 101 at a higher frequency than the read image of the second shading sheet 102. For example, the image reading unit (image sensor 107) may read the second shading sheet 102 once every N times (any number of times equal to or greater than two) the first shading sheet 101.

[0086] In another aspect, the control unit 400 may be configured to be able to accept an input of a setting of the reading frequency of each of the first shading sheet 101 and the second shading sheet 102. In this case, the image reading unit (image sensor 107) may obtain a read image of the first shading sheet 101 and a read image of the second shading sheet 102 at different frequencies based on the setting. As an example, the control unit 400 may accept a setting of the reading frequency of each shading sheet from an operation panel or the like. The operation panel may be provided in the image reading device 10 or an image forming device including the image reading device 10.

[0087] In another aspect, the control unit 400 may acquire a read image of the second shading sheet 102 at at least one of the timings of power-on, sleep recovery, and immediately before sleep. More specifically, the control unit 400 may acquire a read image of the second shading sheet 102 at each timing via the image reading unit (image sensor 107). Moreover, these timings may be predetermined by a program or a setting file thereof. Moreover, these timings may be included in the above-mentioned settings that the user can refer to. That is, the above-mentioned settings may be configured so that at least one of power-on, sleep recovery, and immediately before sleep can be set as the read timing of the second shading sheet 102. The user may set at least one of power-on, sleep recovery, and immediately before sleep as the read timing of the second shading sheet 102. The second shading sheet 102 is located at a position very far from the first slider 301. Therefore, if the second shading sheet 102 is scanned before the document is scanned, the document scan process may take a long time. Therefore, the image reading device 10 can scan the second shading sheet 102 at a timing that does not affect the scanning of the document.

[0088] In one aspect, the control unit 400 may execute shading correction based on the second correction value based on the fact that the current first correction value has changed by a predetermined threshold value or more compared to the past first correction value. For example, when the first shading sheet 101 is stained, the current first correction value may change by a predetermined threshold value or more compared to the past first correction value. In such a case, the control unit 400 may execute shading correction based on the second correction value. That is, the control unit 400 may use the second shading sheet 102 as a backup for the first shading sheet 101.

[0089] 5 is a diagram showing an example of illuminance distribution in the main scanning direction of a read image. The horizontal axis of the graph indicates position in the longitudinal direction (main scanning direction 120). The vertical axis indicates illuminance of each pixel. Graph 510 shows the illuminance distribution at position 410 (near the reading start position). Graph 520 shows the illuminance distribution at position 420 (near the reading end position).

[0090] As an example, the illuminance of graph 510 at a longitudinal position of "0 mm" is approximately "100%." ​​This illuminance is the illuminance of a pixel at the center of the platen glass 110 when the first slider 301 is at position 410. As another example, the illuminance of graph 510 at a longitudinal position of "150 mm" is approximately "115%." This illuminance is the illuminance of a pixel at a position 150 mm away from the center of the platen glass 110 when the first slider 301 is at position 410.

[0091] As an example, the illuminance of graph 520 at a longitudinal position of "0 mm" is about "90%." This illuminance is the illuminance of a pixel at the center of the platen glass 110 when the first slider 301 is at position 420. As another example, the illuminance of graph 520 at a longitudinal position of "150 mm" is about "90%." This illuminance is the illuminance of a pixel at a position 150 mm away from the center of the platen glass 110 when the first slider 301 is at position 420.

[0092] Comparing graph 510 and graph 520, graph 510 is relatively gentle. In contrast, it can be seen that the illuminance distribution of graph 520 is distorted. This is because the distance between first slider 301 and second slider 302 increases, which increases the influence of errors in mechanical parts and the like. As can be seen from graphs 510 and 520, pixels near the leading edge of the image (pixels close to the reading start position) often require only small corrections. Conversely, pixels near the trailing edge of the image (pixels close to the reading end position) often require large corrections.

[0093] The image reading device 10 corrects an image based on the first correction value or the second correction value. Alternatively, the image reading device 10 corrects an image based on the third correction value calculated from the first correction value and the second correction value. Thereby, the image reading device 10 adjusts the gradation of each pixel to the target value 550.

[0094] <C. Processing Procedure of Shading Correction> FIG. 6 is a diagram showing an example of a processing procedure of shading correction by the image reading device 10 according to the present embodiment. In a certain aspect, the control unit 400 may read a program for performing the processing of FIG. 6 from the storage to the memory and execute the program by the processor. In another aspect, part or all of the processing may also be realized as a combination of circuit elements configured to execute the processing.

[0095] In step S610, the control unit 400 acquires the first correction value by reading an image of the first shading sheet 101. More specifically, the control unit 400 moves the first slider 301 and the second slider 302 to the position 410. The control unit 400 acquires a read image of the first shading sheet 101 from the image sensor 107. The control unit 400 calculates the first correction value from the read image of the first shading sheet 101.

[0096] In step S620, the control unit 400 acquires the second correction value by reading an image of the second shading sheet 102. More specifically, the control unit 400 moves the first slider 301 and the second slider 302 to the position 420. The control unit 400 acquires a read image of the second shading sheet 102 from the image sensor 107. The control unit 400 calculates the second correction value from the read image of the second shading sheet 102.

[0097] In some aspects, control unit 400 may execute the process of step S620 at a frequency different from that of step S610. For example, control unit 400 may execute the process of step S620 less frequently than that of step S610. Control unit 400 may also execute the process of step S620 at a specific timing, such as when powering on, when waking up from sleep, or immediately before sleep.

[0098] In step S630, control unit 400 calculates a third correction value from the first and second correction values. In one aspect, the third correction value may be an average value of the first and second correction values. In another aspect, the third correction value may be a correction value in a range between the first and second correction values. In this case, control unit 400 may calculate the third correction value by multiplying the first and second correction values ​​by a coefficient based on the location and occupancy rate of ink in the scanned image, etc.

[0099] In step S640, control unit 400 selects a correction value to be applied to the read image from among a plurality of correction values ​​(first to third correction values). Control unit 400 corrects the scanned image of the original document using the selected correction value. In one aspect, control unit 400 may select the correction value to be used based on the size of the original document in sub-scanning direction 130.

[0100] As described above, the image reading device 10 according to the present embodiment includes the first shading sheet 101 and the second shading sheet 102 located at a distance from each other. The image reading device 10 can correct the scanned image based on the first correction value and / or the second correction value obtained from these two shading sheets. The image reading device 10 can also select either the first correction value or the second correction value depending on the image size or the like, and correct the scanned image using the selected correction value. Furthermore, the image reading device 10 can calculate a third correction value based on the first correction value and the second correction value. The image reading device 10 can correct the scanned image based on the third correction value. By including the correction means for these images, the image reading device 10 can also appropriately correct pixels on the rear end side of the scanned image.

[0101] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present disclosure is indicated by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. In addition, the disclosure contents described in the embodiments and each modified example are intended to be implemented, as far as possible, either alone or in combination. [Explanation of symbols]

[0102] 10 image reading device, 101 first shading sheet, 102 second shading sheet, 103 drive board, 104 angle detection sensor, 105 ADF reading slit glass, 106 document size detection sensor, 107 image sensor, 108 lens, 110 platen glass, 120 main scanning direction, 130 sub-scanning direction, 201 scan motor, 202 home sensor, 203 lighting unit, 301 first slider, 302 second slider, 311 first slider rail, 312 second slider rail, 400 control unit, 401 first mirror, 402 second mirror, 403 third mirror, 410, 420 position, 430, 440 ideal incident light, 435, 445 incident light, 438, 448 curve, 450 difference, 510, 520 graph, 550 target value.

Claims

1. an image reading unit for reading an original on a platen glass; one or more sliders for directing reflected light from the document to the image reading unit; A first shading sheet; a second shading sheet provided at a position different from that of the first shading sheet in the moving direction of the slider; a control unit that corrects the read image, The control unit is calculating a first correction value based on the read image of the first shading sheet and a second correction value based on the read image of the second shading sheet; The image reading device corrects the read image based on either or both of the first correction value and the second correction value.

2. 2. The image reading device of claim 1, wherein correcting the read image based on both or one of the first correction value and the second correction value includes selecting either the first correction value or the second correction value and correcting the read image based on the selected correction value.

3. The image reading device according to claim 2 , wherein selecting one of the first correction value and the second correction value includes selecting one of the first correction value and the second correction value depending on a document size.

4. The image reading device according to claim 3 , wherein the document size is a document size in a moving direction of the slider.

5. 3. The image reading device of claim 2, wherein selecting one of the first correction value and the second correction value includes selecting the first correction value based on the document size in the movement direction of the slider being equal to or smaller than half of a maximum readable size of the image reading device.

6. Correcting the read image based on both or one of the first correction value and the second correction value, generating a third correction value based on the first correction value and the second correction value; The image reading apparatus according to claim 1 , further comprising: correcting the read image based on the third correction value.

7. The image reading apparatus according to claim 6 , wherein the third correction value is an average value of the first correction value and the second correction value.

8. The image reading apparatus according to claim 6 , wherein the third correction value is a correction value in a range between the first correction value and the second correction value.

9. the first shading sheet is provided at or near a reading start position of the image reading unit, 9. The image reading device according to claim 1, wherein the second shading sheet is provided at or near a reading end position of the image reading section.

10. 9. The image reading device according to claim 1, wherein the control unit obtains the read image of the first shading sheet and the read image of the second shading sheet at different frequencies.

11. The image reading device according to claim 10 , wherein the control unit obtains the read images of the first shading sheet more frequently than the read images of the second shading sheet.

12. The control unit is configured to be able to receive an input of a setting of a reading frequency of each of the first shading sheet and the second shading sheet, The image reading device according to claim 10 , wherein the image reading section obtains the read image of the first shading sheet and the read image of the second shading sheet at different frequencies based on the setting.

13. The image reading device according to claim 12 , wherein the control unit obtains the read image of the second shading sheet at least one of when the device is powered on, when the device returns from sleep mode, and immediately before the device goes to sleep mode.

14. The image reading device according to any one of claims 1 to 8, wherein the control unit performs shading correction based on the second correction value based on a change in the current first correction value compared to a past first correction value by more than a predetermined threshold value.

Images