JP2021164102A - Image reading device - Google Patents

Abstract

To determine the abnormality of a scanned image with high accuracy.SOLUTION: A CPU 114 acquires a first scanned image output from reading units 310a, 310b without passing paper in a state in which an opposing roller 313 is positioned at a first distance La with respect to a contact glass 315. When there is an abnormality in the first scanned image, the CPU 114 determines that there is dust, and acquires a second scanned image output from the reading units 310a, 310b without passing paper in a state in which the opposing roller 313 is positioned at the second distance Lb (La<Lb). Then, the CPU 114 determines whether an image defect factor exists in the contact glass 315 or the opposing roller 313 on the basis of the second scanned image.SELECTED DRAWING: Figure 6

Description

The present invention relates to an image reader that reads an image of a sheet.

When image formation is performed using an electrophotographic process, there is a problem that the characteristics of the charging, developing, and transferring processes change due to changes over time and environmental changes, and the quality of printed matter deteriorates. In order to solve this problem, a device has been proposed that uses a document image (sheet image) read by an image reader to maintain high quality printed matter. The following two devices are typical examples.

The first is a device called an image inspection device that outputs only high-quality printed matter by comparing the read original image with a pre-prepared correct answer image and removing low-quality printed matter. The second is to calculate parameters related to the quality of the printed matter such as the density and printing position of the printed matter from the scanned original image, and adjust the image formation process conditions based on the calculation results to output high-quality printed matter. It is a device called an image adjustment device that enables it.

The image reading device applied to these is equipped with optical sensors such as CIS and CCD, and the original image formed and conveyed is read by the optical sensor. A plate-shaped transmissive member called contact glass is provided between the optical sensor and the original. The contact glass plays a role of keeping the distance between the optical sensor and the document constant. When dust adheres to the contact glass, noise is generated in the read image, and there is a problem that the image cannot be inspected normally. Further, there is a problem that the image forming process conditions are not adjusted normally and the quality of the original image cannot be maintained.

In order to prevent the occurrence of such a problem, Patent Document 1 detects whether or not dust is attached to the image acquisition region of the optical sensor, and if dust is detected, prompts the user to clean it. Further, Patent Document 1 improves usability by specifying whether the dust adhered portion is a contact glass or an opposing member such as a white reference plate, and notifying the cleaning portion in a more limited manner. ..

Japanese Unexamined Patent Publication No. 2013-132042

However, in Patent Document 1, since the image in the margin area of the original is compared with the image between the papers, it is necessary to pass the paper in order to acquire the image. Moreover, it is not easy to control the reading timing. Therefore, there is room for improvement in identifying the location of the image defect factor due to dust, dirt, or scratches and accurately determining the abnormality of the scanned image.

Therefore, an object of the present invention is to determine an abnormality in a scanned image with high accuracy.

In order to achieve the above object, the present invention provides a transmission member arranged in a transport path through which a sheet is transported, and a first position and the first position, which are provided on the side opposite to the transmission path with respect to the transport path. An opposing member that moves from the position 1 to a second position away from the transmissive member, a reading means that reads an image on a sheet conveyed along the transport path through the transmissive member, and the opposing member. The control means has a control means for controlling the position of the above, and the control means has a first read image output from the reading means without passing paper in a state where the facing member is controlled to the first position. The cause of the abnormality occurring in the read image is the transparent member or the transparent member based on the second read image output from the reading means without passing the paper in the state where the facing member is controlled to the second position. It is characterized in that it is determined which of the facing members is present.

According to the present invention, it is possible to determine an abnormality in a scanned image with high accuracy.

It is an overall block diagram of a printing system. It is a schematic cross-sectional view of an image forming apparatus. It is a system block diagram of a reading device. It is a figure which shows the structure of the reading part. It is a schematic diagram for demonstrating the dust detection method. It is a flowchart which shows the defect determination process.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is an overall configuration diagram of a printing system including an image reader according to an embodiment of the present invention. This printing system includes an image forming apparatus 100 and a host computer 101. The image forming apparatus 100 and the host computer 101 are communicably connected to each other via the network 105. The network 105 is, for example, a communication line such as a LAN (Local Area Network) or a WAN (Wide Area Network). A plurality of the image forming apparatus 100 and the host computer 101 may be connected to the network 105, respectively.

The host computer 101 is, for example, a server, and transmits a print job to the image forming apparatus 100 via the network 105. This print job includes various information necessary for printing, such as image data, the type of recording paper used for printing, the number of sheets to be printed, and instructions for double-sided or single-sided printing.

The image forming apparatus 100 includes a controller 110, an operation panel 120, a paper feeding device 140, a printer 150, and a reading device 160 (image reading device). The image forming apparatus 100 forms an image on the recording paper based on the print job acquired from the host computer 101. The controller 110, the operation panel 120, the paper feeding device 140, the printer 150, and the reading device 160 are connected to each other so as to be able to communicate with each other via the system bus 116.

The controller 110 controls each unit of the image forming apparatus 100. The controller 110 includes a ROM (Read Only Memory) 112, a RAM (Random Access Memory) 113, and a CPU (Central Processing Unit) 114. Further, the controller 110 includes an I / O control unit 111 and an HDD (Hard Disk drive) 115.

The I / O control unit 111 is an interface that controls communication with the host computer 101 and other devices via the network 105. The ROM 112 is a storage device that stores various control programs. The RAM 113 functions as a system work memory for reading and storing the control program stored in the ROM 112. The CPU 114 executes a control program read into the RAM 113 to control the image forming apparatus 100 in an integrated manner. HDD 115 is a large-capacity storage device. The HDD 115 stores various data such as a control program and image data used for image forming processing (printing processing). The modules are connected to each other via the system bus 116.

The operation panel 120 is a user interface and includes operation buttons, a numeric keypad, and an LCD (Liquid Crystal Display). The operator can input print jobs, commands, print settings, and the like to the image forming apparatus 100 by using the operation panel 120. The operation panel 120 displays the setting screen and the state of the image forming apparatus 100 on the LCD.

The paper feed device 140 includes a plurality of paper feed stages for accommodating recording paper. The paper feed device 140 feeds paper one by one from the top recording paper of the stack of recording paper loaded on the paper feed stage. The paper feed device 140 conveys the recording paper fed from the paper feed stage to the printer 150.

The printer 150 forms an image on the recording paper supplied from the paper feed device 140 based on the image data. The specific configuration of the printer 150 will be described later with reference to FIG. The reading device 160 reads the printed matter generated by the printer 150 and transfers the reading result to the controller 110.

FIG. 2 is a schematic cross-sectional view of the image forming apparatus 100. The image forming apparatus 100 further includes a finisher 190. The finisher 190 is a post-processing device that performs post-processing on the printed matter output by the printer 150. The finisher 190, for example, performs a stapling process on a plurality of printed matter or a sorting process on the printed matter.

As shown in FIG. 2, the printer 150 includes four image forming units. The four image forming units are image forming units that form yellow, magenta, cyan, and black images. Since the configurations of the image forming units are almost the same, the configuration of one image forming unit will be described.

The image forming unit includes a photosensitive drum 153, a charger 220, an exposure device 223, a developer 152, and a cleaner 222. The photosensitive drum 153 is rotated in the direction of arrow R1 by a motor (not shown). The charger 220 charges the surface of the photosensitive drum 153. The exposure apparatus 223 exposes the photosensitive drum 153. As a result, an electrostatic latent image is formed on the photosensitive drum 153. The developer 152 develops an electrostatic latent image using a developer (toner). As a result, the electrostatic latent image on the photosensitive drum 153 is visualized, and a toner image is formed on the photosensitive drum 153.

The printer 150 includes an intermediate transfer belt 154 on which the image formed by the image forming unit is transferred, and a paper feeding device 140. The paper feed device 140 includes paper feed stages 140a, 140b, 140c, 140d, 140e for accommodating the recording paper. The printer 150 transfers the yellow, magenta, cyan, and black toner images formed by the image forming unit so as to overlap the intermediate transfer belt 154. As a result, a full-color image is formed on the intermediate transfer belt 154. The toner remaining on the photosensitive drum 153 after the transfer of the toner image to the intermediate transfer belt 154 is recovered by the cleaner 222.

The image on the intermediate transfer belt 154 is conveyed in the direction of arrow R2. Then, the image formed on the intermediate transfer belt 154 is transferred to the recording paper conveyed from the paper feed device 140 at the nip portion between the intermediate transfer belt 154 and the transfer roller 221.

The printer 150 has a first fuser 155 and a second fuser 156. The first fixing device 155 and the second fixing device 156 heat and pressurize the image transferred to the recording paper to fix the image on the recording paper. The first fixing device 155 includes a fixing roller having a heater inside, and a pressure belt for pressing the recording paper against the fixing roller. These rollers are driven by a motor (not shown) to convey the recording paper. The second fixing device 156 is arranged downstream of the first fixing device in the transport direction of the recording paper. The second fixing device 156 increases the gloss and ensures the fixing property of the image on the recording paper that has passed through the first fixing device 155. The second fuser 156 includes a fixing roller having a heater inside and a pressurizing roller having a heater inside. Depending on the type of recording paper, it is not necessary to use the second fixing device 156. In this case, the recording paper is conveyed to the transfer path 130 without passing through the second fixing device 156. The flapper 131 switches between guiding the recording paper to the transport path 130 and guiding it to the second fixing device 156.

The flapper 132 switches between guiding the recording paper to the transport path 135 and the discharge path 139. The flapper 132 guides the recording paper on which the image is formed on the first surface to the transport path 135, for example, in the double-sided printing mode. The flapper 132 guides the recording paper on which the image is formed on the first surface to the discharge path 139, for example, in the face-up paper discharge mode. The flapper 132 guides the recording paper on which the image is formed on the first surface to the transport path 135, for example, in the face-down paper ejection mode. Further, the flapper 132 guides the recording paper to the transport path 135 in order to print the image on the second surface of the recording paper after the image is printed on the first surface of the recording paper.

The recording paper conveyed to the transfer path 135 is conveyed to the reversing section 136. The recording paper conveyed to the reversing section 136 is switched back to reverse the conveying direction of the recording paper after the conveying operation is temporarily stopped. Next, the flapper 133 switches whether to guide the recording paper to the transport path 138 or the transport path 135. The flapper 133 guides the switched back recording paper to the transport path 138, for example, in the double-sided printing mode. The flapper 133 guides the switched back recording paper to the transport path 135, for example, in the face-down paper ejection mode. The recording paper conveyed to the transfer path 135 by the flapper 133 is guided to the discharge path 139 by the flapper 134. Further, the flapper 133 guides the switched back recording paper to the transport path 138 in order to print an image on the second surface of the recording paper.

The recording paper conveyed to the transfer path 138 by the flapper 133 is conveyed toward the nip portion between the intermediate transfer belt 154 and the transfer roller 221. As a result, the front and back sides of the recording paper when passing through the nip portion are reversed.

A reading device 160 for reading a printed image on the recording paper is connected downstream of the printer 150 in the transport direction of the recording paper. A sheet of recording paper (the image-formed sheet is referred to as a "manuscript") supplied from the printer 150 to the reading device 160 is conveyed along the conveying path 314. The reading device 160 further includes a document detection sensor 311 and reading units 310a and 310b. The document detection sensor 311 is, for example, an optical sensor having a light emitting element and a light receiving element. In order to determine the image reading timing of the reading units 310a and 310b, the document detection sensor 311 detects the tip of the document transported along the transport path 314 in the transport direction.

The reading units 310a and 310b read the image on the document (on the sheet). The reading units 310a and 310b are provided at upper and lower positions on the transport path 314 in order to read images on both sides of the document. By detecting the density value and the printing position based on the scanned image, the image stability of the printer 150 is improved.

FIG. 3 is a system configuration diagram of the reading device 160. The reading device 160 includes a line sensor 312a, 312b, an image memory 303, a motor control unit 304, an image processing unit 305, and a document detection sensor 311. The image memory 303, the motor control unit 304, the image processing unit 305, the document detection sensor 311, and the line sensors 312a and 312b are connected to the CPU 114 in the controller 110, and each device is controlled by the CPU 114.

The motor control unit 304 controls all the motors mounted in the reader 160. The document detection sensor 311 is used to determine the image reading timing. The line sensors 312a and 312b start the reading operation based on the detection timing of the document detection sensor 311.

The line sensors 312a and 312b are included in the reading units 310a and 310b, respectively. The line sensors 312a and 312b are arranged with a direction orthogonal (perpendicular) to both the document transport direction and the document thickness direction as the longitudinal direction. The longitudinal direction of the line sensors 312a and 312b is the same as the main scanning direction of the document. The document transport direction is the same as the document sub-scanning direction. The line sensors 312a and 312c are, for example, CIS (Contact Image Sensor). The line sensors 312a and 312b read the image in the main scanning direction of the document and output the RGB image data to the image processing unit 305.

The image memory 303 stores image data necessary for image processing in the CPU 114. The image processing unit 305 includes a density detection unit 305a, a position detection unit 305b, an image inspection unit 305c, and a dust detection unit 305d. The image processing unit 305 is composed of an FPGA (Field Programmable Gate Array), an ASIC (Application Specific Integrated Circuit), a CPU, and the like.

The density detection unit 305a detects the density of the printed matter. The density detection unit 305a calculates the RGB density value from the scanned image data of the density pattern printed on the edge of the test document. The calculated density value is output to the CPU 114 in the image forming apparatus 100 and used for adjusting the image process conditions.

The position detection unit 305b detects the print position of the printed matter. The position detection unit 305b calculates the print position of the image from the read image data of the resist pattern called the register mark printed on the edge of the test document. The calculated print position information is output to the CPU 114 and used for adjusting the print image position. The image inspection unit 305c compares the read image with the correct image prepared in advance, and outputs the comparison result. The comparison result is output to the finisher 190 and used to sort the OK (normal) printed matter and the NG (abnormal) printed matter.

The dust detection unit 305d detects and outputs the presence / absence of dust and the information on the attachment location of dust in the reading area in the main scanning direction from the RGB image data. Details of the method for detecting dust from RGB image data will be described later. In the following, the term "dust" is used for convenience as a concept that includes not only "dust" as a foreign substance but also all image defect factors (causes of abnormalities occurring in the read image) such as stains or scratches. Therefore, the dust detection unit 305d detects the cause of the image defect.

4 (a) and 4 (b) are views showing the configuration of the reading unit 310a in the reading device 160. The reading unit 310a and the reading unit 310b have the opposite vertical relationship, but the basic configuration is the same. Therefore, the reading unit 310a will be described as a representative in FIGS. 4A and 4B.

The reading unit 310a includes a line sensor 312a, a contact glass 315 (transmission member), a transport path 314, an opposing roller 313 (opposing member), a swing arm 317, an eccentric cam 318, a motor 319, and an urging spring 320. The contact glass 315 is arranged in the transport path 314. The contact glass 315 is made of transparent glass and is installed flush with the transport path 314 so as not to cause a step. The opposing roller 313 is arranged to face the contact glass 315. That is, the opposing roller 313 is provided on the side opposite to the contact glass 315 with respect to the transport path 314. The line sensor 312a is arranged at a position where a document conveyed along the transfer path 314 between the contact glass 315 and the opposing roller 313 can be read through the contact glass 315. The line sensor 312a reads the document through the contact glass 315.

The surface of the opposing roller 313 is processed to be black. Since the surface is black, the difference in brightness from the white paper document becomes large, and the position of the paper edge portion of the document can be detected with high accuracy. The surface color of the opposing roller 313 may be any color other than black as long as it can sufficiently secure the brightness difference from the white paper.

The opposing roller 313 plays a role of keeping the distance between the document and the line sensor 312a within a predetermined range. By keeping the distance between the document and the line sensor 312a within a predetermined range, stable image reading can be performed. The opposing roller 313 is configured to be able to move up and down according to the thickness of the passing paper. That is, the opposing roller 313 is configured to have a variable distance from the contact glass 315 or the line sensor 312a.

In the case of thick paper, the opposing roller 313 moves away from the contact glass 315 (raises here), and in the case of thin paper, the opposing roller 313 approaches the contact glass 315 (descends here). As a result, the distance between the document and the line sensor 312a can be kept within a predetermined range regardless of the thickness of the paper. In FIGS. 4A and 4B, the approaching state (here, the descending state) and the separated state (here, the ascending state) of the opposing roller 313 with respect to the contact glass 315 are shown, respectively.

The elevating control of the opposing roller 313 is performed by the swing arm 317, the eccentric cam 318, the motor 319, and the urging spring 320. The motor 319 mainly serves as a driving means for driving the opposing roller 313. The opposing roller 313 is fixed to the swing arm 317. When the motor 319 rotates the eccentric cam 318, the distances Δa and Δb (Δa <Δb) between the contact point where the eccentric cam 318 comes into contact with the swing arm 317 and the rotation center of the swing arm 317 change.

In the approaching state (FIG. 4A), a large downward pushing force acts on the swing arm 317, and the acute angle (angle θ) formed by the swing arm 317 with respect to the horizontal direction becomes small (angle θa). Therefore, the distance L between the opposing roller 313 and the contact glass 315 becomes small (first distance La). In the separated state (FIG. 4B), the downward pushing force applied to the swing arm 317 is small, and the urging spring 320 exerts an upward force on the swing arm 317. Therefore, the angle θ becomes large (angle θb), and the distance L becomes large (second distance Lb). The second distance Lb is longer than the first distance La. In this way, the opposing roller 313 can be raised and lowered.

In the reading unit 310b, the direction of attachment / detachment to the contact glass 315 due to the elevating / lowering operation of the opposing roller 313 is opposite to that of the reading unit 310a. That is, in the reading unit 310b, the opposing roller 313 rises to approach the contact glass 315, and the facing roller 313 descends to separate the contact glass 315. In this way, the opposing roller 313 can move between the approaching state (first position) and the separated state (second position) separated from the contact glass 315 from the first position.

5 (a) to 5 (e) are schematic views for explaining a dust detection method. The dust detection method by the reading unit 310a and the reading unit 310b is basically the same except that the directions are different. Therefore, FIG. 5 typically describes a dust detection method by the reading unit 310a. In each figure, the line sensor 312a, the contact glass 315, the opposing roller 313, and the transport path 314 are shown, and next to them, a read image by a defect determination process for detecting dust is shown. In each figure, the transport direction (paper-passing direction) is to the left, and the sub-scanning direction of the scanned image is parallel to the paper-passing direction.

Conventionally, in general, white dust (hereinafter referred to as white dust) generated by paper dust or the like is often generated as a factor of image defects. However, since the white reference plate is used on the facing surface in the above-mentioned Patent Document 1, when white dust adheres, both the image of the margin area of the original and the image between the papers become an image in which the entire area is white. Therefore, there is a problem that the detection accuracy is low when the foreign matter is white dust. On the other hand, in the present embodiment, the surface of the opposing roller 313 is black and the brightness is sufficiently low, so that the detection accuracy of white dust is particularly high.

In the defect determination process according to the present embodiment, the reading unit 310a reads the image without actually passing the paper. Therefore, the images to be read are the surface of the contact glass 315 and the surface of the opposing roller 313. When dust is present between the two, the presence of dust is reflected in the scanned image depending on the distance between the dust and the line sensor 312a.

In FIG. 5A, there is no dust between the contact glass 315 and the opposing roller 313. In FIGS. 5B and 5C, white dust G is present on the contact glass 315. In FIGS. 5D and 5E, white dust G is present on the surface of the opposing roller 313. Regarding the elevating position of the opposing roller 313, FIGS. 5 (a), (b) and (d) show an approaching state, and FIGS. 5 (c) and 5 (e) show a separated state.

When an image is acquired by the line sensor 312a in the state shown in FIG. 5A, the black surface of the opposing roller 313 is substantially read. Therefore, the scanned image is an image in which the entire region is black. The reading time is about the same as the paper passing time, but there is no particular limitation as long as the length in the sub-scanning direction is long enough to show the influence of dust.

In the scanned image acquired in the state shown in FIG. 5B, a white line extending in the sub-scanning direction appears at one place in the main scanning direction due to the white dust G on the contact glass 315. A white line appears in the scanned image acquired in the state shown in FIG. 5 (c) as in FIG. 5 (b). This is because the distance from the line sensor 312a to the white dust G is almost the same between the state shown in FIG. 5 (b) and the state shown in FIG. 5 (c).

In the scanned image acquired in the state shown in FIG. 5 (d), due to the white dust G on the opposing roller 313, the sub-scanning is performed at one place in the main scanning direction as in FIG. 5 (c). A white line that extends in the direction appears. However, in the scanned image acquired in the state shown in FIG. 5 (e), almost no white line is generated, and the entire region becomes a black image. This is because the distance from the line sensor 312a to the white dust G is longer in the state shown in FIG. 5E than in the state shown in FIG. 5D. That is, since the white dust G deviates from the focal position of the line sensor 312a, it is difficult to appear as a luminance value in the read image.

When the white dust G adheres to the main scanning range on the opposing roller 313 in this way, the scanned image differs depending on the elevating position of the opposing roller 313. Therefore, in the present embodiment, the CPU 114 as the control means uses the two scanned image data before and after the ascending / descending of the opposing roller 313 to determine whether the white dust G adheres to the contact glass 315 or the opposing roller 313. Identify if it is above. First, the CPU 114 determines that dust is present if there is a white portion having high brightness in the scanned image acquired in the approaching state. Then, when the CPU 114 determines that dust is present, the opposing roller 313 is placed in a separated state, and if the scanned image acquired in the separated state also has a white portion having a high brightness value, the dust is present on the contact glass 315. Then it is determined. However, if the scanned image acquired in the separated state does not have a white portion having a high luminance value, the CPU 114 determines that the dust is attached to the opposing roller 313.

FIG. 6 is a flowchart showing a defect determination process for detecting dust. This process is realized by the CPU 114 expanding the program stored in the ROM 112 into the RAM 113 and executing the program. This process is started when the execution command of the defect determination process is input. This execution command is input not only when the power is turned on, but also when the density detection and print position detection operations are completed. Alternatively, the execution command may be input according to the user's instruction.

FIG. 6 typically describes a reading operation by the reading unit 310a. The operation by the reading unit 310b may be executed in parallel with the reading unit 310a, or may be executed at a timing independent of the reading unit 310a. Since the reading unit 310a will be described in FIG. 6, the descent control is the approach control and the ascending control is the separation control with respect to the elevating control of the opposing roller 313.

In step S101, the CPU 114 controls the opposing roller 313 to approach (descent) by controlling the motor control unit 304, and brings the distance between the contact glass 315 and the opposing roller 313 into an approaching state (first distance La). In step S102, the CPU 114 acquires the first scanned image. Here, the first scanned image is a scanned image acquired from the line sensor 312a without passing paper when the opposing roller 313 is approaching the contact glass 315.

In step S103, the CPU 114 determines whether or not the first scanned image has an abnormality (image defect), that is, whether or not there is a luminance portion indicating dust (image defect factor). Here, the CPU 114 determines the presence or absence of dust based on whether or not there are pixels having a predetermined brightness value or more in all the pixels in the main scanning direction. Since the opposing roller 313 is black, if there is no white dust, all the pixels in the main scanning direction will have a predetermined brightness value or less. However, if there is white dust, the brightness value at the main scanning position where the white dust is present becomes equal to or higher than the predetermined brightness value, and a white line extending in the sub-scanning direction appears (see FIGS. 5 (b), (c), and (d)). ).

Then, when there is no abnormality in the first scanned image (see FIG. 5A), the CPU 114 determines in step S104 that there is no dust, and ends the process shown in FIG. However, if there is an abnormality in the first scanned image, it is determined that there is dust between the opposing roller 313 and the contact glass 315, and the process proceeds to step S105.

In step S105, the CPU 114 controls the opposing roller 313 to be separated (raised) by controlling the motor control unit 304, and sets the distance between the contact glass 315 and the opposing roller 313 in a separated state (second distance Lb). In step S106, the CPU 114 acquires the second scanned image. Here, the second scanned image is a scanned image acquired from the line sensor 312a without passing paper when the opposing roller 313 is separated from the contact glass 315.

In step S107, the CPU 114 determines whether or not there is an abnormality (image defect) in the second scanned image. Here, the method for determining the presence or absence of dust is the same as in step S103. Then, if there is an abnormality in the second scanned image (see FIG. 5C), the CPU 114 determines in step S109 that the dust is present on the contact glass 315, and ends the process shown in FIG. On the other hand, if there is no abnormality in the second scanned image (see FIG. 5E), the CPU 114 determines in step S108 that the dust is present on the opposing roller 313, and ends the process shown in FIG.

In steps S108 and S109, the CPU 114 notifies the determination result. That is, the CPU 114 executes a notification process for notifying the presence of dust and the location where it is determined that there is dust (whether it is the contact glass 315 or the opposing roller 313). This notification process includes urging the cleaning of the place where the dust is present. Further, in step S104, it is notified that there is no dust. The notification process is displayed on the operation panel 120, but may be voiced.

According to the present embodiment, the CPU 114 is the first reading output from the reading units 310a and 310b without passing paper in a state where the opposing roller 313 is positioned at the first distance La with respect to the contact glass 315. Get an image. If there is an abnormality in the first scanned image, the CPU 114 determines that there is dust, and outputs the images from the reading units 310a and 310b without passing the paper in a state where the opposing roller 313 is positioned at the second distance Lb. Acquire the second scanned image. Then, the CPU 114 determines the location of dust based on the second scanned image. Thereby, it is possible to determine whether the image defect factor due to dirt or scratches is present in the contact glass 315 or the opposing roller 313. That is, the abnormality of the scanned image can be determined with high accuracy.

Further, when there is no image abnormality in the first scanned image, it is determined that there is no image defect factor without acquiring the second scanned image, so that the operation of acquiring the second scanned image is not wastefully executed. ..

The target for determining the existence location is not limited to white dust, but the brightness of the opposing roller 313 is made lower than the brightness of the white paper, so that the white dust can be easily determined. This is also convenient when the opposing roller 313 is made black in order to accurately detect the position of the paper edge portion of the document.

By the way, the opposing roller 313 is a cylindrical member, but is a member that does not rotate. However, the opposing roller 313 may be a rotating member. In the configuration in which the opposing roller 313 rotates, white streaks (hereinafter, white streaks) may occur in the circumferential direction of the opposing roller 313. In this case, the same problem as in the case where the opposing roller 313 does not rotate occurs. In the scanned image when white streaks are generated on the opposing roller 313, a white portion having high brightness is generated in a part in the main scanning direction. On the other hand, when white dust adheres to the contact glass 315, a white portion having high brightness is also formed in a part in the main scanning direction. Therefore, it may not be possible to distinguish between the white streaks of the opposing roller 313 and the white dust of the contact glass 315 as the cause of the image defect.

However, if the defect determination process of the present embodiment is applied, the cause of this image defect can be identified. For example, if there is no high-brightness white part in the scanned image of the opposing roller 313 in a separated state, the image defect factor exists in the opposing roller 313, and if the scanned image has a high-brightness white part, the image defect factor is It can be identified as present in the contact glass 315.

Although two reading units 310a and 310b are provided as the reading means, the present invention can be applied to a configuration in which the reading means is one. Although contact glass 315 has been mentioned as an example of the transmissive member, the transmissive member is not limited to the glass material.

Although the image reading device of the present invention corresponds to the reading device 160, the CPU that executes the defect determination process may be provided in the reading device 160. Further, the image reading device of the present invention may have an image forming function. Therefore, the device in which the reader 160 and the printer 150 are integrated may be the image reader of the present invention. Alternatively, the image forming apparatus 100 may be regarded as the image reading apparatus of the present invention.

Although the present invention has been described in detail based on the preferred embodiments thereof, the present invention is not limited to these specific embodiments, and various embodiments within the scope of the gist of the present invention are also included in the present invention. included.

114 CPU
310a, 310b Reader 312a, 312b Line sensor 313 Opposing roller 315 Contact glass 319 Motor

Claims (5)

A transparent member placed in the transport path where the sheet is transported, and
An opposing member provided on the opposite side of the transport path from the transmission member and moving from the first position to a second position separated from the transmission member.
A reading means for reading an image on a sheet conveyed along the transfer path through the transmission member, and
It has a control means for controlling the position of the facing member.
The control means controlled the first read image output from the reading means and the facing member to the second position in a state where the facing member was controlled to the first position. In this state, it is determined whether the cause of the abnormality occurring in the scanned image exists in the transparent member or the opposing member based on the second scanned image output from the scanning means without passing the paper. An image reader characterized by. The first aspect of claim 1, wherein the control means determines that the cause of the abnormality exists in the transparent member when there is an image abnormality in both the first scanned image and the second scanned image. Image reader. 1. The control means is characterized in that, when the first scanned image has an image abnormality and the second scanned image has no image abnormality, it is determined that the cause of the abnormality exists in the facing member. Or the image reading device according to 2. Any of claims 1 to 3, wherein the control means notifies that cleaning is promoted based on a determination result of whether the cause of the abnormality occurring in the read image exists in the transparent member or the opposing member. The image reading device according to item 1. The image reading device according to any one of claims 1 to 4, wherein the reading means is a line sensor arranged in a main scanning direction orthogonal to the sheet conveying direction.

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