Image reading device, and image forming system

Abstract

To provide an image reading device that can predict the occurrence of an error in advance with high accuracy.SOLUTION: An image reading device comprises: a surface optical scanner unit (202) that reads a document; a nonvolatile memory 907 that stores the maximum value of a shading correction coefficient of the surface optical scanner unit (202) as time-series data; and a CPU 901 that separates the time-series data to a periodicity component and a durability component of the surface optical scanner unit (202), generates a prediction curve of the maximum value of the shading correction coefficient with the periodicity component and the durability component, and predicts the occurrence of an error on the basis of the prediction curve.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an image reading device that reads an image from a document. [Background technology]

[0002] An image reading device illuminates a document from a light source and receives the reflected light with a reading sensor to read images and characters (hereinafter simply referred to as "images") formed on the document. In an image reading device, a document is placed on a glass platen with the reading surface facing downwards. The document is pressed against the glass platen by a cover. The image reading device reads the image on the document while the cover is pressing the document. When an automatic document feeder (hereinafter referred to as "ADF") is used, the image reading device reads the image from the document transported by the ADF.

[0003] When scanning an original, shading correction is performed to correct variations in the optical transmission characteristics of the optical system and the sensitivity of each pixel of the scanning sensor. Shading correction is performed based on the scanning results (scanned data) of a white reference member. A white reference member is a member whose at least one surface has uniform scanning luminance in the main scanning direction when scanning an image. An example of shading correction is shown in the following equation (1). K / Dwb(n) in equation (1) is called the "shading correction coefficient." Dout(n)=K×Din(n) / Dwb(n) …(1) Din(n): Document reading data (reading luminance data) Dwb(n): Reading luminance data of white reference material K: Shading target reading luminance data Dout(n): Read luminance data after shading correction

[0004] There is a technology for image reading devices that monitors the read data (brightness value) of a white reference member and stops the reading operation when the read data does not reach a predetermined value (Patent Document 1). In Patent Document 1, the peak data (peak value) of the read data of the white reference member is constantly monitored, and the reading operation is stopped if the peak data does not reach a reference value even after a predetermined time has passed since the light source was turned on. This technology constantly checks for light emission errors of the light source and stops the reading operation if an error occurs. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-101253 Summary of the Invention [Problem to be solved by the invention]

[0006] When a reading operation is stopped due to an error, it is important to accurately predict the occurrence of the error in advance in order to continue the reading operation without interruption. By predicting the occurrence of an error, an alarm for cleaning or other procedures can be issued before the error occurs, preventing the reading operation from being stopped. However, predicting the occurrence of an error using a forecast line obtained only from recent trends without considering seasonal fluctuations reduces the accuracy of the prediction. For example, there is a risk that the alarm will be issued earlier, such as the error occurring the following year after the alarm is issued. For this reason, it is necessary to predict the occurrence of an error by taking into account seasonal cyclical fluctuations and durability fluctuations, and to issue an alarm when the read data reaches a predetermined threshold.

[0007] SUMMARY OF THE INVENTION In view of the above problems, it is a primary object of the present invention to provide an image reading device that can predict the occurrence of an error with high accuracy in advance. [Means for solving the problem]

[0008] The image reading device of the present invention is characterized by comprising: a reading means for reading an original; a storage means for storing correction data for correcting the reading characteristics of the reading means as time-series data; and a control means for separating the time-series data into a periodic component and a durability component of the reading means, generating a prediction curve for the correction data using the periodic component and the durability component, and predicting the occurrence of an error based on the prediction curve. [Effects of the Invention]

[0009] According to the present invention, it is possible to predict the occurrence of an error in advance with high accuracy. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram illustrating the configuration of an image forming system. [Figure 2] FIG. 1 is a diagram illustrating the configuration of an image reading device. [Figure 3] FIG. [Figure 4] FIG. [Figure 5] Flowchart showing scanning. [Figure 6] FIG. [Figure 7] FIG. 10 is a diagram illustrating an example of a shading correction coefficient. [Figure 8] FIG. [Figure 9] FIG. 10 is a diagram illustrating an example of a shading correction coefficient. [Figure 10] 10 is a flowchart showing a process for reading images on both sides of a document. [Figure 11] 10 is a flowchart showing a process of saving the maximum value of the shading correction coefficient and temperature data. [Figure 12] 10 is a flowchart showing a process for creating a prediction curve of a shading correction coefficient. [Figure 13] FIG. 10 is a diagram illustrating the maximum value of the shading correction coefficient. [Figure 14] FIG. 10 is a diagram illustrating a straight line fitted to the maximum value of the shading correction coefficient. [Figure 15] FIG. 10 is an example diagram of periodicity data. [Figure 16] 10 is an example of fitting results. [Figure 17] A graph plotting the prediction curve. [Figure 18] FIG. 10 is a diagram illustrating an example in which a cleaning timing determination threshold value is corrected. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

[0012] (Image forming system) 1 is a diagram showing the configuration of an image forming system according to this embodiment. The image forming system 101 includes a printer 101A and an image reading device 105. The image reading device 105 is provided on top of the printer 101A. The image reading device 105 includes an image reading unit 200 and an ADF 1000 that transports documents D one by one to the reading position of the image reading unit 200.

[0013] The image reading device 105 optically scans the document D to read the image and generates image data representing the read image. The image data is sent to a control unit 132 provided in the printer 101A. The control unit 132 controls the operation of the printer 101A to form an image on a sheet S according to the acquired image data. The printer 101A is an image forming device that includes an image forming unit 133 that forms an image according to the image data and a sheet feeding unit 104 that feeds the sheet S to the image forming unit 133.

[0014] The sheet feeding unit 104 is equipped with a plurality of sheet storage units 137a, 137b, 137c, and 137d, each capable of storing a sheet. The sheets stored in each of the sheet storage units 137a, 137b, 137c, and 137d are fed by a pickup roller 102, separated one by one by a feed roller 103a and a retard roller 103b, and conveyed to the corresponding conveyance roller pair 131. The sheet S is sequentially delivered to the plurality of conveyance roller pairs 131 provided along the sheet conveyance path, and conveyed to a registration roller pair 136. Note that the sheet feeding unit 104 can also feed a sheet S placed on a manual feed tray 137e by a user into the printer 101A by a feed roller 138, and convey the sheet S to the registration roller pair 136.

[0015] The registration roller pair 136 stops the leading edge of the sheet S to correct skew, and resumes conveyance of the sheet S in accordance with the progress of the image creation operation, which is the image formation process, by the image forming unit 133. In this embodiment, the registration roller pair 136 varies the timing at which conveyance of the sheet S is resumed, thereby adjusting the position of the toner image transferred onto the sheet S. The timing at which conveyance of the sheet S is resumed is determined based on an image position adjustment amount held by the control unit 132. The image position adjustment amount can be set independently for the front and back sides of the sheet S.

[0016] The image forming unit 133 is an electrophotographic unit equipped with a photosensitive drum 121, which is a photosensitive member having a photosensitive layer on its surface. The photosensitive drum 121 is rotatable along the conveyance direction of the sheet S. Around the photosensitive drum 121, a charger 118, an exposure unit 123, a developing unit 124, a transfer charger 125, a separation charger 126, and a cleaner 127 are arranged.

[0017] The charger 118 uniformly charges the surface of the photosensitive drum 121. The exposure unit 123 exposes the photosensitive drum 121 to laser light modulated based on image data, thereby forming an electrostatic latent image on the photosensitive drum 121. The developing unit 124 contains a two-component developer containing toner and carrier, and develops the electrostatic latent image into a toner image by supplying charged toner to the photosensitive drum 121.

[0018] The toner image carried on the photosensitive drum 121 is transferred onto the sheet S conveyed from the registration roller pair 136 by a bias electric field formed by the transfer charger 125. The sheet S onto which the toner image has been transferred is separated from the photosensitive drum 121 by a bias electric field formed by the separation charger 126, and is conveyed to the fixing section 129 by the pre-fixing conveying section 128. Note that any deposits such as residual toner that remain on the photosensitive drum 121 without being transferred to the sheet S are removed by a cleaner 127. By removing the deposits, the photosensitive drum 121 is prepared for the next image forming operation.

[0019] The sheet S conveyed to the fixing unit 129 is sandwiched between a pair of rollers constituting the fixing unit 129 and pressurized and heated, thereby melting and fixing the toner, and the image is fixed. The sheet S with the fixed image is discharged to a discharge tray 130 protruding outward from the printer 101A via a pair of discharge rollers 110. When an image is formed on the back side of the sheet S in double-sided printing, the sheet S that has passed through the fixing unit 129 has its front and back sides swapped by a reversing unit 139, and is conveyed to a pair of registration rollers 136 by a double-sided conveying unit 140.

[0020] The registration roller pair 136 adjusts the timing for restarting the conveyance of the sheet S, as with the front surface, to adjust the position of the toner image transferred to the back surface of the sheet S. By matching the transfer timing of the front and back surfaces, the image positions on both surfaces can be aligned. The sheet S, on whose back surface an image has been formed by the image forming unit 133, is discharged to the discharge tray 130.

[0021] The above has been a description of the case where image formation is performed by the electrophotographic method in the image forming unit 133. The image forming unit 133 may be a printing mechanism that uses, for example, an inkjet method or an offset printing method in addition to the electrophotographic method.

[0022] (Image reader) 2 is a configuration diagram of the image reading device 105. As described above, the image reading device 105 of this embodiment includes the image reading unit 200 and the ADF 1000. An image processing controller, which will be described later with reference to FIG. 3, is connected to the image reading device 105. The image processing controller 400 is included in the control unit 132 of the printer 101A shown in FIG. 1, for example.

[0023] The configuration of the image reading device 105 will be described. The ADF 1000 is attached to the image reading unit 200 so as to be openable and closable relative to the image reading unit 200. On the surface of the image reading unit 200 facing the ADF 1000, a document table glass 209, a front white reference member 210, and a front surface flow reading glass 201 are provided.

[0024] The image reading section 200 has a front surface optical scanner unit 202. The front surface optical scanner unit 202 includes front surface LEDs (Light Emitting Diodes) 203a and 203b as light sources, an optical system (reflecting mirrors 204a, 204b, and 204c), a front surface imaging lens 207, and a front surface image reading sensor 205. The front surface optical scanner unit 202 is equipped with a surface temperature detection sensor 206. The front surface LEDs 203a and 203b irradiate light onto the reading surface of the original D. The optical system guides light reflected by the reading surface of the original D to the front surface imaging lens 207. The front surface imaging lens 207 forms an image of the reflected light on the light receiving surface of the front surface image reading sensor 205.

[0025] The surface image reading sensor 205 is a line sensor in which multiple light receiving elements are arranged in one direction. Reflected light is imaged on the light receiving surface of each light receiving element. Each light receiving element of the surface image reading sensor 205 photoelectrically converts the received reflected light to generate read data, which is an electrical signal. The surface LEDs 203a and 203b irradiate the original D with light in a line in the same direction as the direction in which the light receiving elements are arranged. The direction in which the light receiving elements are arranged is the main scanning direction. In Figure 2, the depth direction is the main scanning direction. The temperature around the surface image reading sensor 205 is detected by a surface temperature detection sensor 206.

[0026] Such a front surface optical scanner unit 202 can read an original D placed on the platen glass 209 and an original D transported by the ADF 1000. When reading an original D placed on the platen glass 209, the front surface optical scanner unit 202 reads the image line by line while moving at a constant speed in a sub-scanning direction (the direction of the arrow in the figure) that intersects the main scanning direction. This type of reading process is called "fixed reading." When reading an original D transported by the ADF 1000, the front surface optical scanner unit 202 is fixed directly below the front surface flow reading glass 201, and reads the image line by line from the original D transported on the front surface flow reading glass 201. This type of reading process is called "flow reading."

[0027] The front white reference member 210 is used to generate shading correction coefficients. The front white reference member 210 is formed of a uniform white color within its surface, and its size in the main scanning direction is configured to encompass all pixels in the main scanning direction of the front image reading sensor 205. Shading correction coefficients are generated based on the results of reading the front white reference member 210 by the front optical scanner unit 202.

[0028] The ADF 1000 has an original tray 30 on which a stack of one or more originals D (original stack) is loaded, and an output tray 32 onto which the scanned originals D are discharged. The original tray 30 is provided with original length sensors 17 and 18 for detecting the length of the stacked originals in the transport direction (original length). The ADF 1000 transports the originals D one by one to the reading position of the front optical scanner unit 202 and discharges them onto the output tray 32. To this end, the ADF 1000 has multiple rollers and sensors on the transport path.

[0029] The ADF 1000 includes a paper feed roller 1, an upper separation roller 2, and a lower separation roller 3. The upper separation roller 2 and the lower separation roller 3 prevent the stack of documents from protruding from the document tray 30 and advancing downstream in the transport direction before the transport of the documents D begins. The document tray 30 is provided with a document presence / absence detection sensor 11. The document presence / absence detection sensor 11 is used to detect the presence or absence of documents D on the document tray 30.

[0030] When transporting the documents D, in order to reliably transport the documents D stacked on the document tray 30, it is necessary to bring the document feed roller 1 into contact with the document stack and create a state in which an appropriate pressure is applied to the contact area. To achieve this, the document tray 30 is raised to a certain height, and the document feed roller 1 is pressed against the topmost document stack. As the document feed roller 1 rotates in this state, the topmost document in the document stack is fed first.

[0031] In order to detect that the document tray 30 has been raised to a certain height, a paper feed roller upper limit position detection sensor 20 and an upper limit position flag 21 are provided. The upper limit position flag 21 is provided on a member that holds the paper feed roller 1. When the document tray 30 is raised to a certain height, the paper feed roller upper limit position detection sensor 20 detects the upper limit position flag 21.

[0032] The paper feed roller 1 drops onto the top of the stack of documents loaded on the document tray 30 and rotates. This causes the topmost document D of the document stack to be fed. Of the documents D fed by the paper feed roller 1, the topmost sheet is separated and conveyed by the action of the upper separation roller 2 and the lower separation roller 3. This separation process is achieved by known separation technology.

[0033] The document D separated into one sheet by the upper separation roller 2 and the lower separation roller 3 is transported by pull-out rollers 4 and 5. A paper feed path for transporting the document D toward the front surface flow reading glass 201 is arranged downstream of the pull-out roller 5 in the transport direction of the document D.

[0034] The original D sent to the paper feed path is transported to the reading position of the front surface optical scanner unit 202 by the upstream lead roller 6 and the guide plate upstream roller 7. At the reading position of the front surface optical scanner unit 202, a front surface glass facing member 211 is provided opposite the front surface flow reading glass 201, and the original D is transported between the front surface flow reading glass 201 and the front surface glass facing member 211. This prevents the original D from fluttering when passing through the reading position. As the original D passes between the front surface flow reading glass 201 and the front surface glass facing member 211, the image of the original D is read line by line by the front surface optical scanner unit 202.

[0035] The document D that has passed the reading position of the front surface optical scanner unit 202 is transported by the guide plate downstream roller 8. When only the front surface of the document D is to be read, the document D is discharged from the guide plate downstream roller 8 to the paper discharge tray 32 via the back surface reading transport roller 9 and the paper discharge roller 10.

[0036] When the back side of the document D is also to be read, the document D is read by a back side optical scanner unit 302 provided between the back side reading transport roller 9 and the paper discharge roller 10. A back side glass facing member 301 having a back side white reference member 310 is provided facing the back side optical scanner unit 302. The back side glass facing member 301 is disposed at the reading position of the back side optical scanner unit 302. By using the back side optical scanner unit 302, the back side of the document D can be read without having to turn it over in the transport path.

[0037] After the image on the front side of the document D is read, the document D is read by the back side optical scanner unit 302 as it passes over the back side glass facing member 301. The document D whose back side has been read is discharged to the discharge tray 32 by the discharge rollers 10.

[0038] Similar to the front optical scanner unit 202, the back optical scanner unit 302 includes back LEDs 303a and 303b as light sources, an optical system (reflecting mirrors 304a, 304b, and 304c), a back imaging lens 307, and a back image reading sensor 305. The back optical scanner unit 302 is equipped with a back temperature detection sensor 306. The back optical scanner unit 302 reads the back side of the document D by the same reading operation as the front optical scanner unit 202. The back temperature detection sensor 306 detects the temperature around the back image reading sensor 305. The back optical scanner unit 302 can read a back white reference member 310 attached on the back glass facing member 301.

[0039] When removing the document D discharged onto the paper output tray 32, the document tray 30 is lifted by the user. This makes it easier to remove the document D discharged onto the paper output tray 32. If a jam occurs, the cover 22 can be opened around the jam clearing rotation part 33 to separate the upper separation roller 2 attached to the cover 22 from the lower separation roller 3 in order to remove the document D. A cover open / close detection sensor 19 is provided to detect whether the cover 22 is open or closed. After reading or jam clearing is completed, the document tray 30 is lowered from a state in which it has been raised to a certain height in preparation for placing a document for the next reading. A lifter home position detection sensor 23 is provided to detect the descent of the document tray 30.

[0040] A separation sensor 12, a pull-out sensor 13, a lead sensor 15, and a paper discharge sensor 16 are provided on the transport path of the original D to control the transport operation and reading operation of the original D. The separation sensor 12 and the pull-out sensor 13 detect the original D being transported and are used to determine whether the transport is proceeding normally. When the lead sensor 15 detects the original D, the front optical scanner unit 202 and the back optical scanner unit 302 start their reading operations.

[0041] (controller) 3 is an explanatory diagram of a controller that controls the operation of the image reading device 105 configured as described above. The controller includes the image processing controller 400 and an image reading controller 410. The image reading controller 410 is provided in the control unit 132 or the image reading device 105.

[0042] The image reading controller 410 is an information processing device that includes a CPU (Central Processing Unit) 801, a ROM (Read Only Memory) 802, and a RAM (Random Access Memory) 803. The CPU 801 controls the operation of the image reading device 105 by executing a computer program stored in the ROM 802. The RAM 803 provides a working area for the CPU 801 when executing processing. The image reading controller 410 also includes a nonvolatile memory 812, in which working data is stored. The CPU 801 uses the working data stored in the nonvolatile memory 812 when controlling the image reading device 105.

[0043] The CPU 801 is connected to the drive sources (motors) for driving various rollers provided in the ADF 1000 to transport the document D, and the various sensors described above. Such motors include a separation motor 805, a pull-out motor 806, a lead motor 807, a pickup motor 808, and a lifter motor 809.

[0044] The separation motor 805 is a drive source for rotating the paper feed roller 1 and the upper separation roller 2. The pull-out motor 806 is a drive source for rotating the pull-out rollers 4 and 5. The lead motor 807 is a drive source for rotating the upstream lead roller 6, the guide plate upstream roller 7, the guide plate downstream roller 8, the back side reading transport roller 9, and the paper discharge roller 10. The pickup motor 808 is a drive source for raising and lowering the paper feed roller 1. The pickup motor 808 is connected to the paper feed roller 1 via an oval cam (not shown), and lowers (contacts) or raises (separates from) the paper feed roller 1 between fed sheets. The lifter motor 809 is a drive source for raising and lowering the document tray 30.

[0045] When feeding the document D, the CPU 801 causes the lifter motor 809 to raise the document tray 30, on which the document stack is loaded, to a predetermined height, and the pickup motor 808 presses the feed roller 1 against the top surface of the document stack loaded on the document tray 30. The CPU 801 then causes the lifter motor 809 to raise the document tray 30, and the document D at the top of the document stack pushes up the feed roller 1. This causes the feed roller upper limit position detection sensor 20 to detect the upper limit position flag 21. The detection result is transmitted to the CPU 801. The CPU 801 then stops the lifter motor 809 within a predetermined time after receiving this detection result, thereby raising the document tray 30 to a predetermined height. Although details are omitted, the document tray 30 may be raised not when the document stack is loaded but when the reading operation begins. The lifter home position detection sensor 23 may also be configured to detect that the document tray 30 has reached the lowered position when it is lowered.

[0046] The CPU 801 can determine the standard size of the document D placed on the document tray 30 based on the detection results of the document length sensors 17, 18 and the detection result of the tray top width detection sensor 810. The document length sensors 17, 18 detect the document stack placed on the document tray 30. The detection results of the document length sensors 17, 18 change depending on the document length of the document D. For example, if the document length is longer than the position of the document length sensor 17 and shorter than the position of the document length sensor 18, the document length sensor 17 detects the document stack, and the document length sensor 18 does not detect the document stack. The document length sensors 17, 18 each output a detection result according to the document length.

[0047] The tray top width detection sensor 810 is composed of a variable resistor and an A / D converter. The tray top width detection sensor 810 is connected to, for example, two regulating plates that regulate the movement in the main scanning direction of a stack of documents loaded on the document tray 30. The two regulating plates are connected to variable resistors, and the resistance value of the variable resistor changes depending on the length between the regulating plates. The tray top width detection sensor 810 converts the analog voltage value that changes due to the variable resistor into 10-bit data using the A / D converter, and can output a detection result that indicates the length of the document D in the main scanning direction (document width).

[0048] The CPU 801 can detect the length of the stack of documents loaded on the document tray 30 based on the detection results of the document length sensors 17 and 18, and can detect the width of the stack of documents loaded on the document tray 30 based on the detection results of the tray width detection sensor 810. The CPU 801 determines the standard size of the documents based on the detected document length and document width.

[0049] The CPU 801 can also detect the length of the original document using a sensor provided on the conveyance path. For example, the CPU 801 can detect the length of the original document from the time during which the lead sensor 15 detects the original document D being conveyed and the conveyance speed of the original document D. The CPU 801 can also determine the standard size of the original document based on the detected original document length and the detection result of the tray width detection sensor 810.

[0050] When feeding the originals D, the CPU 801 detects that a stack of originals has been placed on the original tray 30 by the original presence / absence detection sensor 11. Thereafter, the CPU 801 feeds the originals D as described above. When transporting the fed originals D, the CPU 801 controls the drive of the separation motor 805, the extraction motor 806, and the lead motor 807 based on the detection results of the separation sensor 12, the extraction sensor 13, the lead sensor 15, and the discharge sensor 16 to rotate the rollers. The separation motor 805, the extraction motor 806, and the lead motor 807 are pulse motors, and the CPU 801 can count the number of drive pulses to control the rotation speed of each motor.

[0051] The CPU 801 counts the number of drive pulses of the pull-out motor 806 from when the pull-out sensor 13 detects the document during document transport until it no longer detects it. The transport distance of the document D is detected from the number of drive pulses used to drive the pull-out motor 806 and the advance per pulse (gear ratio) of the gear that transmits the drive force of the pull-out motor 806 to the pull-out roller 4. In other words, by counting the number of drive pulses of the pull-out motor 806, it is possible to detect the document length of the document D being transported. Furthermore, the CPU 801 can also detect the length between documents being transported (paper gap) by counting the number of drive pulses of the pull-out motor 806 from when the pull-out sensor 13 detects the document during document transport until it detects it.

[0052] To read the image of the original D, the front optical scanner unit 202 (front LED 203, front image reading sensor 205) and the back optical scanner unit 302 (back LED 303, back image reading sensor 305) are connected to the CPU 801. The front LEDs 203a and 203b are collectively referred to as the front LED 203, and the back LEDs 303a and 303b are collectively referred to as the back LED 303. The optical motor 804 is a drive source for moving the front optical scanner unit 202 in the sub-scanning direction when performing skimming. The optical motor 804 is a pulse motor, and the CPU 801 counts the number of drive pulses to control the rotation speed of the optical motor 804. This allows the CPU 801 to control the position of the front optical scanner unit 202 in the sub-scanning direction.

[0053] The CPU 801 reads the original D using the front image reading sensor 205 and the back image reading sensor 305, and generates image data as the reading result. When the front image reading sensor 205 and the back image reading sensor 305 receive light reflected from the original D, they generate read data based on the received reflected light. The CPU 801 generates image data by appropriately processing the read data using an image processing unit 811. The image data is transmitted to the image processing controller 400. The image processing unit 811 generates image data by performing shading processing and various filter processing on the read data. The image processing unit 811 transmits the generated image data to the image processing controller 400 via the image communication line 402.

[0054] The image processing unit 811 includes a shading correction unit 253, a shading RAM 254, an averaging unit 260, an addition unit 261, and a division unit 262. The shading RAM 254 includes an arithmetic memory 255 and a coefficient memory 256. The image processing unit 811 performs shading correction with this configuration.

[0055] The image processing controller 400 includes a CPU 901, a ROM 902, a RAM 903, a nonvolatile memory 907, an image processing unit 905, and an image memory 906. An operation display unit 904 is connected to the image processing controller 400.

[0056] The CPU 901 executes a computer program stored in the ROM 902, thereby controlling the operation of the image reading device 105 in cooperation with the CPU 801 of the image reading controller 410. The RAM 903 provides a working area for the CPU 901 when executing processing. The non-volatile memory 907 stores working data. The CPU 901 can use the working data stored in the non-volatile memory 907 when controlling the image reading device 105.

[0057] The CPU 901 is connected to the CPU 801 of the image reading controller 410 via the command communication line 401, and transmits and receives data related to image reading control to and from the CPU 801. The image processing unit 905 acquires image data from the image processing unit 811 of the image reading controller 410 via the image communication line 402. The image processing unit 905 performs predetermined image processing, such as color determination, on the acquired image data, and then stores the image data in the image memory 906.

[0058] The operation and display unit 904 is a user interface that includes an input interface and an output interface. The input interface is, for example, various key buttons, a touch panel, etc. The output interface is, for example, a display, a speaker, etc. The CPU 901 acquires information such as instructions and settings input by the user to the operation and display unit 904, and performs processing based on the input information such as the start of a reading job. The CPU 901 displays various screens, such as messages and setting screens, on the operation and display unit 904. The CPU 901 stores, in a non-volatile memory 907, information input from the operation and display unit 904 and various data that should be maintained even when the power is off.

[0059] (Shading correction) FIG. 4 is an explanatory diagram of shading correction. In FIG. 4, the horizontal axis indicates each pixel position in the main scanning direction of the front-side optical scanner unit 202, and the vertical axis indicates the reading result of the front-side white reference member 210 read by the front-side optical scanner unit 202. Here, the reading result is a luminance value. Note that the luminance value shown in the figure is one of three colors: red, green, and blue. A luminance value is measured for each color. In this embodiment, the luminance value is expressed in 8 bits (0 to 255). The pixel position in the main scanning direction is expressed as 1 to 7016.

[0060] The luminance value waveform a is a waveform before shading correction of the read data (luminance value) obtained by reading the white-surface reference member 210 with the front-surface optical scanner unit 202, and has non-uniform characteristics for each pixel in the main scanning direction. The luminance value waveform b is a waveform after shading correction of the luminance value waveform a. By performing shading correction, the waveform a is corrected to have approximately uniform characteristics (values) for each pixel in the main scanning direction.

[0061] The following four points are generally cited as reasons why waveform a becomes uneven: 1. Variation in sensitivity of each pixel of the surface optical scanner unit 202 (surface image reading sensor 205) 2. Variation and fluctuation in light distribution in the main scanning direction of the front-surface LEDs 203a and 203b 3. Deterioration of light intensity at the edge of the front-surface imaging lens 207 4. Cloudiness due to calcium carbonate and other substances adhering to the optical system (reflecting mirrors 204a, 204b, 204c)

[0062] The image reading operation and shading correction operation in the image reading device 105 will now be described. The CPU 801 moves the front-side optical scanner unit 202 to directly below the front-side white reference member 210 using the optical motor 804. The CPU 801 positions the front-side optical scanner unit 202 directly below the front-side white reference member 210 and performs black shading correction with the front-side LED 203 turned off. Following the black shading correction, the CPU 801 performs white shading correction with the front-side LED 203 turned on.

[0063] Black shading correction is a process for correcting pixel unevenness by adjusting the read data obtained by reading the surface white reference member 210 with the surface LED 203 turned off so that the read data reaches a predetermined target value for each pixel. White shading correction is performed by performing shading correction on the read data obtained by reading the surface white reference member 210 with the surface LED 203 turned on. Black shading correction and white shading correction are performed by the shading correction unit 253 under the control of the CPU 801.

[0064] After the white shading correction is completed, the CPU 801, while keeping the front LEDs 203a and 203b lit, moves the front optical scanner unit 202 in the sub-scanning direction using the optical motor 804, causing the front optical scanner unit 202 to read the original D. In the case of flow reading, the front optical scanner unit 202 reads the original D placed on the original glass 209 while moving in the sub-scanning direction below the original glass 209. In the case of fixed reading, the front optical scanner unit 202 moves to and is fixed directly below the front flow reading glass 201, and reads the original D transported by the ADF 1000.

[0065] Shading correction is also performed on the rear optical scanner unit 302 in the same manner as on the front optical scanner unit 202. In this case, black shading correction and white shading correction are performed using a rear white reference member 310.

[0066] (shading correction coefficient) The front surface optical scanner unit 202 of this embodiment reads 7,500 pixels per line in the main scanning direction of the front surface white reference member 210 during white shading correction. The addition processing unit 261 adds up the read data of each pixel of the front surface optical scanner unit 202 for 64 lines, and stores the summed data in the calculation memory 255. The averaging processing unit 260 calculates the average value of the read data from the summed data for each pixel, and stores the average value in the calculation memory 255. The calculation memory 255 stores data M(n) (n: pixel position in the main scanning direction) that is the average value for the number of pixels in the main scanning direction.

[0067] The division processing unit 262 performs the following division operation between the shading target value (Kdat) stored in advance in the nonvolatile memory 812 and the data M(n) stored in the calculation memory 255. The result of the division is stored as a shading correction coefficient CD(n) in the coefficient memory 256. In this way, the shading correction coefficient CD(n) is calculated for each pixel position in the main scanning direction. CD(n)=Kdat / M(n) …(2)

[0068] (Image reading processing) 5 is a flowchart showing skimming, in which original D placed on platen glass 209 is read. This process is started when the user places original D on platen glass 209 with the reading surface facing platen glass 209, and then issues an instruction to start a skimming reading job via operation display unit 904. Upon receiving the instruction to start the reading job, CPU 901 instructs CPU 801 to start skimming. CPU 801 starts this process by receiving an instruction to start skimming from CPU 901.

[0069] The CPU 801 moves the front-surface optical scanner unit 202 directly below the front-surface white reference member 210 using the optical motor 804 (S101). The CPU 801 performs the above-described black shading correction with the front-surface LED 203 turned off and acquires a black shading correction offset value. Next, the CPU 801 reads the front-surface white reference member 210 with the front-surface LED 203 turned on, and acquires a shading correction coefficient CD(n) using the shading correction unit 253 (S102).

[0070] FIG. 6 is an example diagram of read data stored in the calculation memory 255 during white shading correction. The horizontal axis represents the pixel position in the main scanning direction, and the vertical axis represents the luminance value (read data). In color reading, red, green, and blue are read, and read data indicated by R, G, and B, respectively, is obtained. As described above, the shading correction coefficient CD(n) is calculated by performing division processing for each RGB color using the data M(n) and the shading target value Kdat according to equation (2).

[0071] FIG. 7 is a diagram illustrating the shading correction coefficient CD(n) obtained in this manner. Here, the shading correction coefficient CD(n) for each of the colors R, G, and B is shown. Pixels with low luminance values ​​in FIG. 6 have high shading correction coefficients CD(n) in FIG. 7. Conversely, pixels with high shading correction coefficients CD(n) are pixels with low luminance values. Reading when the luminance value is low results in low gradation, which is undesirable for the image reading device 105.

[0072] FIG. 8 is an example diagram of read data stored in the calculation memory 255 during white shading correction. The read data (brightness value) in FIG. 8 has a lower brightness value compared to FIG. 6. One of the causes of the lower brightness value is clouding caused by calcium carbonate or the like adhering to the optical system (reflecting mirrors 204a, 204b, 204c). The brightness value can be increased again by properly cleaning the clouded optical system.

[0073] Fig. 9 is an example diagram of the shading correction coefficient CD(n) obtained from the read data exemplified in Fig. 8. As in Fig. 7, the shading correction coefficient CD(n) for each color of R, G, and B is shown. Since the luminance values ​​in Fig. 8 are lower than the luminance values ​​in Fig. 6, the values ​​of the shading correction coefficient CD(n) in Fig. 9 are higher than those in Fig. 7.

[0074] After acquiring the shading correction coefficient CD(n), the CPU 801 acquires the detected temperature (temperature data) from the surface temperature detection sensor 206 and stores it in the RAM 803 (S103). The CPU 801 stores the temperature at the time of calculating the shading correction coefficient in order to correct the prediction curve of the shading correction coefficient and change the threshold value, which will be described later, using the acquired temperature data.

[0075] Thereafter, the CPU 801 reads the original D using the front surface optical scanner unit 202 (S104). Specifically, the CPU 801 reads the original D on the platen glass 209 line by line while moving the front surface optical scanner unit 202 in the sub-scanning direction using the optical motor 804. The read data obtained by reading the original D is subjected to image processing such as shading correction in the image processing unit 811 and converted into image data. When the reading of the original D is completed, the CPU 801 moves the front surface optical scanner unit 202 using the optical motor 804 to return it to the standby position.

[0076] The CPU 801 acquires the maximum value of the shading correction coefficient (S105). The maximum value of the shading correction coefficient acquired here is the maximum value among the values ​​of the shading correction coefficients CD(n) of each color. In the example of Fig. 7, the maximum value of the shading correction coefficient is 1024 for red (R), and in the example of Fig. 9, the maximum value of the shading correction coefficient is 3584 for red (R).

[0077] The CPU 801 transmits the acquired maximum value of the shading correction coefficient to the CPU 901 of the image processing controller 400 (S106). Note that the maximum value of the shading correction coefficient may be calculated on the CPU 901 side. In this case, the CPU 801 transmits the shading correction coefficients CD(n) of multiple locations for each color, including the maximum value of the shading correction coefficient, to the CPU 901. The CPU 901 calculates the maximum value of the shading correction coefficient based on the shading correction coefficients CD(n) acquired from the CPU 801. In this embodiment, by transmitting the maximum value of the shading correction coefficient from the CPU 801 to the CPU 901, it is possible to shorten the transmission time and reduce the amount of data stored on the image processing controller 400 side.

[0078] The CPU 801 transmits the temperature data stored in the RAM 803 in the process of S103 to the CPU 901 (S107). The CPU 801 also transmits the image data generated by reading the document D to the image processing controller 400 via the image communication line 402. This completes the process during skimming.

[0079] 10 is a flowchart showing the process of reading images on both sides of an original D conveyed by the ADF 1000. This process is started when the user places an original on the original tray 30 and then instructs the start of a fixed-reading reading job via the operation display unit 904. Upon receiving the instruction to start the reading job, the CPU 901 instructs the CPU 801 to start fixed-reading. The CPU 801 starts this process by receiving the instruction to start fixed-reading from the CPU 901.

[0080] The CPU 801 moves the front optical scanner unit 202 and the back white reference member 310 provided on the back glass facing member 301 to positions for performing shading correction (S201). Specifically, the CPU 801 moves the front optical scanner unit 202 to directly below the front white reference member 210 using the optical motor 804. At the same time, the CPU 801 rotates the lead motor 807 by a predetermined angle in the direction opposite to the direction when the original D is being transported, thereby moving the back white reference member 310 provided on the back glass facing member 301 to the reading position of the back optical scanner unit 302.

[0081] The CPU 801 acquires the shading correction coefficients CD(n) for the front and back surfaces from the shading correction unit 253 (S202). To obtain the front shading correction coefficient CD(n), the CPU 801 first performs the black shading correction described above with the front LED 203 turned off to obtain a black shading correction offset value. Next, the CPU 801 reads the front white reference member 210 with the front LED 203 turned on, and calculates the front shading correction coefficient CD(n) using the shading correction unit 253 based on the reading result. To obtain the back surface shading correction coefficient CD(n), the CPU 801 first performs the black shading correction described above with the back surface LED 303 turned off to obtain a black shading correction offset value. Next, the CPU 801 reads the back surface white reference member 310 with the back surface LED 303 turned on, and calculates the back surface shading correction coefficient CD(n) using the shading correction unit 253 based on the reading result.

[0082] The shading correction unit 253 and the shading RAM 254 have separate configurations for the front and back sides. By providing independent configurations for the front and back sides, it becomes possible to perform image processing in parallel in terms of time. The CPU 801 rotates the lead motor 807 by a predetermined angle in the direction opposite to the direction in which the original D is transported, thereby moving the back side white reference member 310 to a position away from the reading position of the back side optical scanner unit 302.

[0083] After acquiring the shading correction coefficient CD(n), the CPU 801 acquires the detected temperatures (temperature data) from the front surface temperature detection sensor 206 and the back surface temperature detection sensor 306, and stores the detected temperatures in the RAM 803 (S203). The CPU 801 stores the temperatures at the time of calculating the shading correction coefficient in order to use the acquired temperatures to correct the prediction curve of the shading correction coefficient and change the threshold value, which will be described later.

[0084] Thereafter, the CPU 801 starts conveying the original D (S204). The CPU 801 drives the pickup motor 808, the separation motor 805, the extraction motor 806, and the read motor 807 to convey the original D to the respective reading positions of the front optical scanner unit 202 and the back optical scanner unit 302. The CPU 801 reads both sides of the original D using the front optical scanner unit 202 and the back optical scanner unit 302 (S205). Specifically, the CPU 801 counts the movement amount (number of pulses) of the read motor 807 based on the timing when the read sensor 15 detects the original D. After counting a predetermined number of pulses, the CPU 801 reads the original D using the front optical scanner unit 202 and the back optical scanner unit 302. The read data obtained by reading the original D is subjected to image processing such as shading correction in the image processing unit 811 and converted into image data. Image data for the front side and the back side are generated separately.

[0085] The CPU 801 acquires the maximum value of the shading correction coefficient (S206). The acquired maximum value of the shading correction coefficient is the maximum value among the values ​​of the shading correction coefficients CD(n) of each color. The CPU 801 acquires the maximum values ​​of the shading correction coefficients for the front and back sides. The CPU 801 transmits the acquired maximum values ​​of the shading correction coefficients for the front and back sides to the CPU 901 of the image processing controller 400 (S207). The CPU 801 assigns an identifier to each of the maximum values ​​for the front side and the maximum value for the back side so that the CPU 901 can distinguish whether the maximum value is for the front side or the back side.

[0086] The CPU 801 transmits the temperature data stored in the RAM 803 in the processing of S203 to the CPU 901 (S208). The CPU 801 assigns an identifier to each of the temperature data for the front and back sides so that the CPU 901 can determine whether the temperature data is for the front or back side. The CPU 801 also transmits the image data for the front and back sides generated by reading the original D to the image processing controller 400 via the image communication line 402. This completes the process of reading the images on both sides of the original D.

[0087] FIG. 11 is a flowchart showing processing by the CPU 901 to save the maximum value of the shading correction coefficient and the temperature data. This processing saves the maximum value of the shading correction coefficient for the day and the minimum and maximum values ​​of the temperature data for the day in order to create a prediction curve of the shading correction coefficient, which will be described later. Here, a case will be described in which the maximum value of the shading correction coefficient and the temperature data are data obtained when reading the front side of the original D. In other words, FIG. 11 shows processing to save the maximum value of the shading correction coefficient and the temperature data transmitted in the processing of S106 and the processing of S107 in FIG. 5. Note that data obtained when reading the back side of the original D is processed in the same way. The data obtained when reading the back side of the original D can be identified by an identifier.

[0088] 5 from the CPU 801 and stores it in the RAM 903 (S301). The CPU 901 determines whether or not the maximum value of the shading correction coefficient has been received within the day (S302). Whether or not the maximum value of the shading correction coefficient has been received within the day is determined, for example, based on the date / time when the maximum value was received and the date of the maximum value stored in the nonvolatile memory 907.

[0089] If the maximum value of the shading correction coefficient has not been received within the day (S302: N), the CPU 901 stores a pair of the received maximum value and the date / time in the nonvolatile memory 907 (S303). That is, the CPU 901 stores in the nonvolatile memory 907 a pair of the maximum value of the shading correction coefficient received for the first time within the day and the date / time of reception.

[0090] If the maximum value of the shading correction coefficient has been received on that day (S302: Y), the CPU 901 reads the maximum value Smax stored in the nonvolatile memory 907 on that day (S304). The CPU 901 compares the maximum value Smax read from the nonvolatile memory 907 with the maximum value of the shading correction coefficient received from the CPU 801 (S305).

[0091] If the comparison shows that the maximum value Smax is smaller than the received maximum value (S305: Y), the CPU 901 saves the pair of the received maximum value of the shading correction coefficient and the received date / time in the non-volatile memory 907 and updates the maximum value Smax (S306). If the maximum value Smax is equal to or greater than the received maximum value (S305: N), the CPU 901 does not update the maximum value Smax in the non-volatile memory 907. The processing after receiving the maximum value of the shading correction coefficient is carried out as described above.

[0092] When the processing after receiving the maximum value of the shading correction coefficient is completed, the CPU 901 receives the temperature data transmitted from the CPU 801 in the processing of S107 in Fig. 5 (S307). The CPU 901 determines whether the received temperature data is the first data of the day, or whether the minimum value of the temperature data of the day is greater than the received temperature data (S308).

[0093] If the received temperature data is the first data of the day, or the minimum temperature data of the day is greater than the received temperature data (S308: Y), the CPU 901 saves the pair of received temperature data and date / time in the non-volatile memory 907 (S309). This updates the minimum temperature value of the day. If the received temperature data is not the first data of the day, or the minimum temperature data of the day is equal to or less than the received temperature data (S308: N), the CPU 901 does not update the minimum temperature value of the day.

[0094] Next, the CPU 901 determines whether the received temperature data is the first data of the day, or whether the maximum temperature data of the day is smaller than the received temperature data (S310). If the received temperature data is the first data of the day, or if the maximum temperature data of the day is smaller than the received temperature data (S310: Y), the CPU 901 saves the pair of the received temperature data and date / time in the non-volatile memory 907 (S311). This updates the maximum temperature value of the day. If the received temperature data is not the first data of the day, or if the maximum temperature data of the day is equal to or greater than the received temperature data (S310: N), the CPU 901 does not update the maximum temperature value of the day.

[0095] This completes the process of saving the maximum value of the shading correction coefficient and the temperature data. Through this process, the nonvolatile memory 907 of the image processing controller 400 stores pairs of the maximum value of the shading correction coefficient and the date / time for that day, and pairs of the maximum and minimum values ​​of the temperature data and the date / time for that day, for multiple days. While FIG. 11 shows the maximum value of the shading correction coefficient and the maximum and minimum values ​​of the temperature data acquired daily, the storage period is not limited to one day and may be any predetermined period. For example, when saving correction data for reading characteristics that are more stable than the shading correction coefficient, a longer period such as two days or one week may be used. When saving correction data for reading characteristics that are less stable than the shading correction coefficient, a shorter period such as half a day may be used. The nonvolatile memory 907 stores the maximum value of the shading correction coefficient and the maximum and minimum values ​​of the temperature data for a first predetermined period for a second predetermined period longer than the first predetermined period.

[0096] (Shading correction coefficient prediction curve) 12 is a flowchart showing the process of creating a prediction curve of a shading correction coefficient. The maximum value of the shading correction coefficient and temperature data stored in the nonvolatile memory 907 are time-series data recorded on a daily basis. Based on this time-series data, a prediction curve of a shading correction coefficient is created to appropriately predict the timing of cleaning of the front optical scanner unit 202. Note that a prediction curve of a shading correction coefficient can also be created for the back optical scanner unit 302 to appropriately predict the timing of cleaning.

[0097] The CPU 901 reads the maximum value of the shading correction coefficient and the temperature data stored in the nonvolatile memory 907 into the RAM 903 (S401). FIG. 13 is a diagram illustrating the maximum value of the shading correction coefficient read into the RAM 903. FIG. 13 is a graph in which the horizontal axis indicates the number of days elapsed and the vertical axis indicates the maximum value D of the shading correction coefficient. Here, the maximum values ​​of the shading correction coefficient for 1,750 days or more are read out. The maximum value D of the shading correction coefficient tends to increase as the number of days passes and changes periodically approximately once a year. The tendency for the maximum value D of the shading correction coefficient to increase as the number of days passes represents fluctuations due to the durability of parts. The periodic change in the maximum value D of the shading correction coefficient approximately once a year represents seasonal fluctuations.

[0098] The CPU 901 extracts a linear component based on the maximum value of the shading correction coefficients read into the RAM 903 (S402). Specifically, the CPU 901 fits the maximum value D of the shading correction coefficients to the following linear function, Equation (3), by the least squares method. y=ax+b …(3)

[0099] FIG. 14 is an example diagram of a straight line L obtained by fitting the maximum value D of the shading correction coefficient in FIG. 13 to the linear function formula (3). The straight line L is an example obtained when data a=1.6 and b=1033.93 are calculated. The linear component is considered to represent the tendency of the luminance value to decrease with the durability of the parts. In other words, the linear component represents the durability component of the front surface optical scanner unit 202.

[0100] The CPU 901 extracts a periodic component based on the maximum value D of the shading correction coefficients read into the RAM 903 (S403). To extract the periodic component, the CPU 901 first calculates periodic data D', as shown in Fig. 15, by subtracting the line L from the maximum value D of the shading correction coefficients. Next, the CPU 901 fits the periodic data D' using the nonlinear least squares method for a sine wave according to the following equation (4). y=c×sin(dx+e)+f …(4)

[0101] FIG. 16 illustrates the fitting results using equation (4). Curve C illustrates the fitting results when c=193.9, d=0.01728, e=-0.04592, and f=-0.007540. Curve C represents the seasonal periodic component. The CPU 901 creates a prediction curve (S404). The prediction curve is calculated by adding equation (5) (linear component) and equation (4) (periodic component). y=ax+b+c×sin(dx+e)+f …(5)

[0102] 17 shows a graph in which a prediction curve E is plotted against the maximum value D of the shading correction coefficient for each number of days elapsed. The error threshold T2 is a threshold for determining that an image reading has an error, and the determination threshold T1 is a threshold for determining the timing of cleaning, which will be described later.

[0103] The CPU 901 determines the timing of cleaning (S405). Here, the timing of cleaning is set to the intersection X of the judgment threshold T1 and the predicted curve E in FIG. 17. In this example, the intersection X is on the 1800th day. The judgment threshold T1 is determined from the width of variation in the maximum value D of the shading correction coefficient. For example, the judgment threshold T1 is calculated by subtracting a margin (for example, 10%) from the absolute value F of the difference between the periodic data D' and the sine wave C shown in FIG. 16 from the error threshold T2.

[0104] If x is the number of days that have passed, the absolute value F is expressed by the following formula (6), and the judgment threshold T1 is expressed by the following formula (7). In the example of Figure 16, if F = 250 and the error threshold T2 = 4000, then T1 = 4000 - 250 × 1.1 = 3725. F = |D'(x) - C(x)| …(6) T1=T2-F×1.1 …(7)

[0105] By setting the cleaning timing at the intersection X of the judgment threshold T1 in FIG. 17 and the prediction curve E (1800 days in the example of FIG. 17), the cleaning timing can be determined with high accuracy. In the example of FIG. 17, although the error threshold T2 is approached around the 1500th day, the maximum value D of the shading correction coefficient is predicted to decrease in the future. This prediction can be used to reflect in the planning of cleaning service provision in the market, such as scheduling cleaning next year instead of this year.

[0106] When the cleaning timing comes within a predetermined period (for example, within one month), the CPU 901 issues an alarm via the operation display unit 904 to notify the user to perform cleaning. In other words, the CPU 901 predicts the occurrence of an error and notifies the user. The user can confirm the cleaning timing by this alarm and take appropriate measures.

[0107] 11, the maximum and minimum values ​​of the temperature data are stored in the nonvolatile memory 907. Using such temperature data, it is possible to correct the prediction curve or the judgment threshold for determining the timing of cleaning.

[0108] The maximum value of the shading correction coefficient varies depending on the fluctuation in the ambient temperature of the front optical scanner unit 202 and the back optical scanner unit 302. This is because temperature fluctuations cause a combination of factors, such as changes in the light intensity of the front LED 203 and the back LED 303, expansion of the front imaging lens 207 and the back imaging lens 307, and changes in the sensitivity of the front image reading sensor 205 and the back image reading sensor 305.

[0109] Here, we will explain a case where the determination threshold T1 for determining the timing of cleaning is corrected based on the maximum and minimum temperature values. Figure 18 is an example diagram when the determination threshold T1 for the timing of cleaning in Figure 17 is corrected. The method for correcting the determination threshold T1 is described below.

[0110] 11, the maximum and minimum values ​​of the temperature data are saved for each day in the nonvolatile memory 907. When the maximum value of the temperature data on the xth day is Gmax(x) and the maximum value of the temperature data on the xth day is Gmin(x), the absolute value of the temperature difference H is expressed by the following equation (8). H = |Gmax(x) - Gmin(x)| … (8)

[0111] The temperature difference absolute value H is multiplied by a variation coefficient α of the shading correction coefficient associated with temperature variation, and the determination threshold T1 can be corrected as shown in the following equation (9). T1 = T2 - F × 1.1 - H × α … (9)

[0112] For example, suppose the daily temperature fluctuation is 20°C, and the coefficient of variation α of the shading correction coefficient due to the temperature fluctuation is 5. In other words, if the absolute difference value H=20 and the coefficient of variation α of the shading correction coefficient=5, then the determination threshold value T1=4000−250×1.1−20×5=3625 is obtained from equation (9), the above error threshold value T2, and the above absolute value F.

[0113] In this way, when there is a risk that the maximum value of the shading correction coefficient will exceed the error threshold T2 due to temperature fluctuations, it is possible to optimize the cleaning timing. In this embodiment, an example in which the judgment threshold T1 is corrected has been described, but the effect of optimizing the cleaning timing can also be obtained by adding correction data H×α, which is obtained by multiplying the absolute difference H by the variation coefficient α, to the prediction curve.

[0114] The above has described a case where the CPU 901 of the image processing controller 400 performs the process of creating a prediction curve of the shading correction coefficient. The process of creating a prediction curve of the shading correction coefficient may also be performed by the CPU 801 of the image reading controller 410. In this case, the maximum value of the shading correction coefficient and the temperature data are stored in the non-volatile memory 812. The CPU 801 also performs the processes of S304 to S306 and S308 to S311 in Fig. 11. In this case, all processes can be performed within the image reading device 105, which is effective in an environment where the image reading device 105 is used alone.

[0115] The image reading device 105 of this embodiment as described above separates the time-series data of the shading correction coefficients into periodic fluctuations and linear fluctuations, and generates a prediction curve for the shading correction coefficients. When the shading correction coefficients predicted by the prediction curve reach a predetermined threshold (determination threshold T1), the image reading device 105 predicts the occurrence of an error and issues an alarm instructing the user to take action before the error occurs. This makes it possible to provide an image reading device 105 that can appropriately perform service before an error occurs, and can continue operating the image forming system 101.

[0116] In the above explanation, the time-series data is a shading correction coefficient, but the time-series data is not limited to this. The time-series data may be correction data for correcting the reading characteristics of the image reading device 105 (front optical scanner unit 202, back optical scanner unit 302). In other words, the image reading device 105 of this embodiment generates a prediction curve by separating seasonal periodic fluctuations and fluctuations in component durability from the time-series data of the correction data, and predicts the occurrence of an error based on the generated prediction curve. As a result, the image reading device 105 suppresses early issuance of an alarm due to seasonal fluctuations in the correction data and continues operation by appropriately taking service action before an error occurs.

Claims

1. reading means for reading an original; a storage means for storing correction data for correcting the reading characteristics of the reading means as time-series data; a control means for separating the time series data into a periodic component and a durability component of the reading means, generating a prediction curve of the correction data using the periodic component and the durability component, and predicting the occurrence of an error based on the prediction curve, Image reading device.

2. the storage means stores, as the time-series data, a maximum value of the correction data for a first predetermined period for a second predetermined period longer than the first predetermined period.

2. The image reading device according to claim 1.

3. The storage means stores maximum values ​​of the correction data for each day for multiple days as the time series data.

3. The image reading device according to claim 2.

4. The control means extracts the durability component by fitting the time series data to a straight line.

2. The image reading device according to claim 1.

5. the control means extracts the durability component by fitting the time series data to a straight line by a least squares method.

5. The image reading device according to claim 4.

6. the control means extracts the periodic component from the time series data by fitting a result obtained by subtracting the durability fluctuation from the time series data to a sine wave.

2. The image reading device according to claim 1.

7. the control means generates the prediction curve by the sum of the periodic component and the durability component.

2. The image reading device according to claim 1.

8. The control means predicts the occurrence of the error when the prediction curve reaches a predetermined threshold.

2. The image reading device according to claim 1.

9. The control means determines the threshold value from a variation range of a maximum value of the correction data.

9. The image reading device according to claim 8.

10. The device further includes a temperature detection means for detecting the temperature of the reading means, the storage means stores the maximum and minimum values ​​of the temperature when the correction data is generated, The control means corrects the threshold value based on an absolute value of a difference between the maximum value and the minimum value of the temperature.

10. The image reading device according to claim 8 or 9.

11. The reading means further includes a reference member used for shading correction, the control means acquires a shading correction coefficient based on the reading result of the reference member by the reading means, and stores the shading correction coefficient in the storage means as the correction data.

2. The image reading device according to claim 1.

12. The device further comprises a notification unit that notifies the user that an error has been predicted when the control unit predicts the occurrence of the error.

2. The image reading device according to claim 1.

13. The image reading device according to claim 1; an image forming device that forms an image on a sheet based on image data, The image reading device generates the image data based on the result of reading the document. Imaging system.

Images