JP2010028682A - Image reading apparatus and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect contamination at a document reading position prior to reading of a document and detection of the contamination by distinguishing the contamination generated by a document glass from the contamination generated by a platen member. <P>SOLUTION: An image reading apparatus includes: a document reading section having an illuminating mechanism for illumination of a document and also having an image sensors, the illuminating mechanism having two columns of a plurality of groups of light emitting devices arranged in a main scan direction in parallel, the two rows being arranged in a sub scan or feed direction in parallel, the image sensors reading reflected light of an image illuminated via an document glass at a document reading position by the groups of light emitting devices directed to a predetermined position of the document glass extended in the main scan direction; a document feeding section for feeding the document in a sub scan or feed direction with respect to the document reading position, an on/off control section for controlling the groups of light emitting devices; and a contamination image detecting section for detecting an image of the contamination deposited on the document glass on the basis of an image read out by the document reading section based on the illumination of the light emitting devices turned on/off in one group and an image read out thereby based on the illumination of the light emitting devices turned on/off in the other group when the document is shifted from the document reading position (steps S301 to S313). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a so-called sheet-through type image reading apparatus that reads an image of an original from the other main surface side of the original glass while conveying the original to be read so as to move on one main surface of the transparent original glass. The present invention relates to an image forming apparatus including the image reading apparatus.

In an image forming apparatus such as a copying machine, when a document image is read and printed by a sheet-through type image reading apparatus, a streak image along the sub-scanning direction may appear in the image. This is usually caused by foreign matter (dirt) or the like that is attached to the glass (original glass) of the image reading apparatus by foreign matters such as dust, dust, or paper dust of the conveyed original paper. Since the streak-like image appears as a black streak in the background portion, which is a white background portion in the printed recording paper, or appears as a white streak in the image portion, as shown in Patent Document 1 below, When the streak-like image is detected, the original reading position of the scanner provided in the image reading apparatus is moved in the sub-scanning direction, the original is read at a position free from the dust, and the user is changed when changing the scanner position. A document reading apparatus that warns against the above has been proposed.
JP 2000-196814 A

  However, in the case of the document reading apparatus disclosed in Patent Document 1, dust cannot be detected unless the document reading operation is actually started. Therefore, it is possible to avoid black streaks due to dust for at least the first document. Can not. The document reading device is based on the premise that dust on the document glass is detected, and foreign matter that does not exist on the document glass, for example, foreign matter on a platen member that guides a document to be transported to the document glass. It is not something to detect.

  The present invention has been made in order to solve the above-described problem. It enables detection of a foreign object at a document reading position before reading a document, and determines whether the foreign object is a document glass or a platen member. The purpose is to detect.

According to a first aspect of the present invention, there is provided a document irradiating mechanism in which a plurality of light emitting element groups arranged in parallel in the main scanning direction are arranged in two rows in the sub scanning direction, and a predetermined document reading position. The image light irradiated by each light emitting element group directed to a predetermined position of the original glass, which is a position between the light emitting element groups in the sub-scanning direction, through the original glass extending in the main scanning direction. A document reading unit having an image sensor for optically reading reflected light;
A document transport unit that transports a document in the sub-scanning direction of the document reading unit with respect to the document reading position;
A lighting control unit that controls lighting by each of the light emitting element groups;
When the document transported by the document transport unit is out of the document reading position, an image read by the illumination by lighting of the one light emitting element group by the document reading unit, and the other light emitting element group The image reading apparatus includes a foreign matter image detection unit that detects a foreign matter image adhering to the original glass based on an image read by illumination by lighting.

  According to the present invention, when the foreign object image detection unit is out of the document reading position, the image read by the illumination by turning on the one light emitting element group when the document is out of the document reading position, and the other light emitting element. Since the image of the foreign matter adhering to the original glass is detected using the image read by the irradiation by the lighting of the group, before the original is conveyed to the original reading position, that is, before the original is read, Foreign matter can be detected. Further, as described above, the document reading unit uses the image read by the illumination by lighting the one light emitting element group and the image read by the illumination by lighting the other light emitting element group, thereby reading the document. It is possible to detect whether or not the foreign matter generated at the time of reading by the section is a foreign matter on the original glass.

According to a second aspect of the present invention, there is provided the image reading apparatus according to the first aspect, wherein the original is transported to a position spaced apart from the original glass on the side opposite to the original reading unit. A platen member for guiding
The foreign object image detection unit has a foreign object image read when the one light emitting element group is turned on and a foreign object image read when the other light emitting element group is turned on in a predetermined width or more in the sub-scanning direction. In the case of the distribution, the foreign object image is determined as an image of the foreign substance existing on the original glass.

  In the present invention, when the foreign matter on the original glass is irradiated by the respective light emitting element groups, the respective light emitting element groups arranged in parallel in the sub-scanning direction are positioned at the original glass position positioned between the respective light emitting element groups. In order to irradiate the image, the shadow of the foreign object is projected onto a platen member provided behind the original glass as viewed from the original reading unit, and the image of both the foreign object and the shadow is read by the imaging device. . The image of the shadow of the foreign matter is projected onto the platen member at different positions in the sub-scanning direction when irradiated with one light emitting element group and when irradiated with the other light emitting element group. When the image of the shadow of the foreign matter is read by the image sensor, the distribution width in the sub-scanning direction becomes wider than when the foreign matter existing on the platen member is read by irradiation with the light emitting element group, for example. Based on this, the foreign matter image detection unit determines whether the distribution width in the sub-scanning direction of both foreign matter images read at the time of each irradiation by the two light emitting element groups is equal to or larger than a predetermined threshold value. This makes it possible to accurately determine whether or not the read foreign object image is an image of a foreign object existing on the original glass.

  The invention according to claim 3 is the image reading apparatus according to claim 2, wherein the foreign object image detection unit is configured to detect the foreign object image read by lighting of the one light emitting element group and the other image element. The foreign object image read by lighting the light emitting element group is distributed over a predetermined width or more in the sub-scanning direction, and the output value of the imaging element is predetermined between the two foreign object images. When the width indicating the range of the output value corresponding to white is equal to or greater than a predetermined value, the foreign object image is determined as an image of a white foreign object existing on the original glass.

  According to the present invention, the output value of the image sensor is an output value corresponding to the color of the foreign matter on the image of the foreign matter on the original glass, and the shadow image of the foreign matter is close to an output value indicating black, for example. Based on the above, the foreign object image detection unit has a width indicating that the output value of the imaging element is within a predetermined output value range corresponding to a predetermined white color between the foreign object images read by irradiation of both the light emitting element groups. When the foreign object image is a predetermined value or more, it is determined that the foreign object image is an image of a white foreign object existing on the original glass, so that the foreign object image exists on the original glass and is a white foreign object. It can be detected accurately.

According to a fourth aspect of the present invention, there is provided the image reading apparatus according to the first aspect, wherein the original is transported to a position spaced apart from the original glass on the side opposite to the original reading unit. A platen member for guiding
The foreign matter image detection unit has a foreign matter image read when the one light emitting element group is turned on and a foreign matter image read when the other light emitting element group is turned on less than a predetermined width in the sub-scanning direction. In the case of distribution, the foreign object image is determined as an image of the foreign object existing on the platen member.

  In the present invention, even when a foreign object existing on the platen member is read by the document reading unit during irradiation by each of the light emitting element groups, a shadow of the foreign object is not projected on the platen member, and the distribution width in the sub-scanning direction. Is based on the fact that the foreign matter on the original glass is relatively smaller than the case where the foreign matter is read, the foreign matter image detection unit distributes both foreign matter images read during each irradiation by the two light emitting element groups in the sub-scanning direction. By determining whether or not the width is less than a predetermined threshold, it is possible to accurately determine whether or not the read foreign object image is an image of a foreign object existing on the platen member. Become.

  The invention according to claim 5 is the image reading apparatus according to any one of claims 1 to 4, wherein the foreign object image detection unit is read by lighting of the one light emitting element group. Either the value of the image sensor or the value of the image sensor read by turning on the other light emitting element group is inverted to calculate an added value of the two values, and the sub-scan indicated by the added value The midpoint of the width in the direction is detected as the center of the foreign matter.

  According to the present invention, it is possible to accurately detect the center of the foreign matter based on the fact that each foreign matter image read by lighting both the light emitting element groups read by the imaging device is distributed at a symmetrical position in the sub-scanning direction. Can do.

  The invention according to claim 6 is the image reading apparatus according to any one of claims 1 to 5, wherein the foreign object image detection unit is configured such that the leading edge of the document conveyed by the document conveying unit is When approaching the document reading position of the document reading unit, the value of the imaging element read when the one light emitting element group is turned on indicates a foreign object image, and is read when the other light emitting element group is turned on. When the value of the image sensor does not indicate the foreign object image, the foreign object image is determined as an image indicating the shadow of the document.

  According to this invention, when the shadow of the leading edge of the conveyed document is read by irradiation of each of the light emitting element groups, only the value of the image pickup element read by lighting one of the light emitting element groups is detected as a foreign object image. Based on the fact that the value of the image sensor read by turning on the other light emitting element group does not indicate the foreign object image, it can be accurately determined that the foreign object image is an image showing the shadow of the document.

  The invention according to claim 7 is the image reading apparatus according to any one of claims 1 to 6, wherein the document reading unit includes a white LED as the light emitting element.

  According to the present invention, since the light emitting element is a white LED, the lighting start-up control of the illumination mechanism synchronized with the reading timing by the image sensor can be performed.

According to an eighth aspect of the present invention, there is provided an image reading apparatus according to any one of the first to seventh aspects,
An image forming apparatus including an image forming unit that forms an image on a recording medium based on a document image read by the document reading unit.

  According to this invention, there exists an effect | action obtained by the invention in any one of Claim 1 thru | or 7.

  According to the present invention, it is possible to detect a foreign object at a document reading position before reading a document, and it is possible to determine and detect whether the foreign object is a document glass or a platen member.

  Embodiments of an image reading apparatus and an image forming apparatus according to the present invention will be described below with reference to the drawings. In the following embodiment, an example in which the image reading apparatus and the image forming apparatus according to the embodiment of the present invention are integrated into a multifunction machine having functions such as a color copy, a scanner, a facsimile, and a printer will be described. FIG. 1 is a vertical cross-sectional view schematically showing an internal configuration of a multifunction machine 1 as an embodiment of an image reading apparatus and an image forming apparatus according to the present invention.

  The multifunction machine 1 is roughly composed of a document reading mechanism 200 and an apparatus body 3. The document reading mechanism 200 includes a document transport unit 21, a scanner unit 22, an operation unit 5, and a reversing mechanism and control unit 61 (see FIG. 2) described later. The document transport unit 21 includes an ADF (Automatic Document Feeder), and includes a document tray 211, a pickup roller 212, a transport path 213, a paper discharge roller 214, and a paper discharge tray 215. A document to be read is placed on the document tray 211. The originals placed on the original tray 211 are taken one by one by the pickup roller 212 and sequentially conveyed to the conveyance path 213 through the gap. Documents that have passed through the conveyance path 213 are sequentially discharged to a discharge tray 215 by a discharge roller 214.

  The scanner unit (original reading unit) 22 optically reads an image of an original and generates image data. The scanner unit 22 includes a platen glass 221, a light source (illumination mechanism) 222, a first mirror 223, a second mirror 224, a third mirror 225, a first carriage 226, a second carriage 227, an imaging lens 228, a CCD (Charge Coupled). Device) 229. In the scanner unit 22, a plurality of LEDs (Light Emitting Diodes) arranged in the main scanning direction are used as the light source 222, and the first mirror 223, the second mirror 224, the third mirror 225, the first carriage 226, and the second carriage. The light from the original is guided to the CCD 229 by the 227 and the imaging lens 228. The configuration of the light source 222 will be described later. In the present embodiment, a white LED is used for the light source 222.

  A document is manually placed on the platen glass 221 by a user's manual operation when the document is not read by the document transport unit 21. The light source 222 and the first mirror 223 are supported by the first carriage 226, and the second mirror 224 and the third mirror 225 are supported by the second carriage 227.

  As the document reading method of the document reading mechanism 200, the scanner unit 22 reads a document placed on the platen glass 221, and the document is captured by the document transport unit 21 (ADF). There is an ADF reading mode.

  In the flat bed reading mode, the light source 222 irradiates a document placed on the platen glass 221, and reflected light for one line in the main scanning direction is reflected in the order of the first mirror 223, the second mirror 224, and the third mirror 225. Then, the light enters the imaging lens 228. The light incident on the imaging lens 228 is imaged on the light receiving surface of the CCD 229. The CCD 229 is a one-dimensional image sensor and simultaneously processes image data of a document for one line. The first carriage 226 and the second carriage 227 are configured to be movable by a moving mechanism (not shown) in a direction orthogonal to the main scanning direction (sub-scanning direction, arrow Y direction), and when reading for one line is completed. Then, the first carriage 226 and the second carriage 227 move in the sub-scanning direction, and the next line is read.

  In the ADF reading mode, the document conveying unit 21 takes in the documents placed on the document tray 211 one by one by the pickup roller 212. At this time, the first carriage 226 and the second carriage 227 are arranged at a predetermined reading position P located below the original glass (original reading window) 230 made of a transparent material such as a glass member. When the document is transported by the document transport unit 21, when the document passes over the document glass (document reading window) 230 provided in the transport path from the transport path 213 to the paper discharge tray 215, the light source 222 irradiates the document. The reflected light for one scanning line is reflected in the order of the first mirror 233, the second mirror 224, and the third mirror 225, and enters the imaging lens 228. The light incident on the imaging lens 228 is imaged on the light receiving surface of the CCD 229. Subsequently, the document is transported by the document transport unit 21 and the next line is read.

  Further, the document conveying unit 21 includes a document reversing mechanism (reversing unit) including a switching guide 216, a reversing roller 217, and a reversing conveying path 218. This document reversing mechanism reverses the front and back of the document whose front side (one side of the document) has been read by the first ADF reading and transports it again to the original glass 230 position. Surface) is read. This document reversing mechanism operates only when reading both sides, and does not operate when reading one side. After reading the back side during single-sided reading and double-sided reading, the switching guide 216 is switched to the upper side, and the document that has passed through the conveyance path 213 is discharged onto the discharge tray 215 by the discharge roller 214. After the front side reading at the time of double-sided reading, the switching guide 216 is switched to the lower side, and the document that has passed through the conveyance path 213 is conveyed to the reverse conveyance path 218 by the reverse roller 217. Thereafter, the switching guide 216 is switched upward, and the reverse roller 217 rotates in the reverse direction to re-feed the original to the conveyance path 213.

  The multifunction device 1 includes an apparatus main body 3 and a stack tray 6 disposed on the left side of the apparatus main body 3. The apparatus main body 3 includes a plurality of paper feed cassettes 461, a paper feed roller 462 that feeds recording paper from the paper feed cassette 461 one by one and transports it to the image forming unit 40, and a recording paper transported from the paper feed cassette 461. And an image forming unit 40 for forming an image. The apparatus body 3 also includes a paper feed tray 471 and a feed roller 472 that feeds the originals placed on the paper feed tray 471 one by one toward the image forming unit 40.

  The image forming unit 40 includes a charge eliminating device 421 that removes residual charges from the surface of the photosensitive drum 43, a charging device 422 that charges the surface of the photosensitive drum 43 after charge removal, and image data acquired by the scanner unit 22. An exposure device 423 that outputs a laser beam to expose the surface of the photosensitive drum 43 to form an electrostatic latent image on the surface of the photosensitive drum 43, and on the photosensitive drum 43 based on the electrostatic latent image. Furthermore, developing devices 44K, 44Y, 44M, and 44C that form toner images of each color of cyan (C), magenta (M), yellow (Y), and black (K), and each color formed on the photosensitive drum 43, respectively. A transfer drum 49 on which the toner image is transferred and overlaid, a transfer device 41 for transferring the toner image on the transfer drum 49 to a sheet, and a sheet on which the toner image is transferred are heated to form a toner image. And a fixing device 45 for fixing to the paper. Note that toner is supplied to each color of cyan, magenta, yellow, and black from a toner supply container (toner cartridge) (not shown). Further, conveyance rollers 463 and 464 that convey the recording paper that has passed through the image forming unit 40 to the stack tray 6 or the discharge tray 48 are provided.

  When forming images on both sides of the recording paper, the image forming unit 40 forms an image on one side of the recording paper, and then the recording paper is nipped by the conveyance roller 463 on the discharge tray 48 side. In this state, the conveyance roller 463 is reversed to switch back the recording paper, and the recording paper is sent to the paper conveyance path L and conveyed again to the upstream area of the image forming unit 40, and an image is formed on the other surface by the image forming unit 40. After the formation, the recording paper is discharged to the stack tray 6 or the discharge tray 48.

  Further, in front of the apparatus main body 3, a display unit 51 that allows a user to visually recognize an operation screen and various messages, and an operation unit 5 having operation buttons for inputting various operation commands are provided. . The display unit 51 is configured by an LCD (Liquid Crystal Display), an ELD (Electronic Luminescent Display), or the like, and displays an operation guidance screen for the user such as paper size selection, magnification selection, density selection, and the like. The display unit 51 has a touch panel function. The touch panel detects the touch position when a touch operation is performed by the user, and outputs a detection signal indicating the touch position to the control unit 61 described later.

  FIG. 2 is a block diagram illustrating an electrical configuration of the multifunction machine 1. In addition, the same code | symbol is attached | subjected to the same part as each part shown in FIG. 1, and the description is abbreviate | omitted. The multifunction machine 1 includes a document transport unit 21, a scanner unit 22, an operation unit 5, an image forming unit 40, a storage unit 67, and a control unit 61.

  When the original is copied or scanned in the ADF reading mode, the original conveying unit 21 automatically takes in the original placed on the original tray 211 and conveys the original so that the CCD 229 can read the original. .

  The operation unit 5 is used for a user to perform operations related to a copy function, a printer function, a facsimile function, a scanner function, and the like, and gives an operation command (command) by the user to the control unit 61. The operation unit 5 includes a display unit 51 having a touch panel, the start button 55 for inputting various instructions such as a copy execution start command or a facsimile transmission start command by the user, a numeric key group 53, and the like.

  The image forming unit 40 forms an image on recording paper based on the image data obtained by the CCD 229 or the image data transferred from the personal computer or the facsimile machine.

  The storage unit 67 is a storage unit that stores image data obtained by the reading operation of the scanner unit 22, image data processed by the control unit 61, which will be described later, and a destination for short button registration when performing facsimile communication. The name, facsimile number, or IP address of the transmission destination when used as a network scanner is stored in advance.

  The control unit 61 controls the overall operation of the multifunction machine 1 and includes a CPU, a RAM, a ROM, and the like. The document conveyance unit 21, the scanner unit 22, the operation unit 5, the image processing unit 615, and the image forming unit 40 operate under the control of the control unit 61. The control unit 61 executes processing based on an operation control program stored in a ROM (not shown) or the storage unit 67 in accordance with various instruction signals or the like input from the user to the operation unit 5. The multifunction device 1 is centrally controlled by outputting an instruction signal to the unit, transferring data, and the like.

  In the multi-function device 1 having the above-described configuration, when a document is read by the document reading mechanism 200 in the ADF mode, the document glass (document reading window) 230 has a foreign object. Is attached, the same pixel in the scanner unit 22 images the foreign matter at each imaging timing, and thereby, in the main scanning direction position corresponding to the pixel position of the same pixel in the obtained image. A streak-like image extending in the sub-scanning direction may be formed.

  If such a situation is left until the reading operation for all the originals in the original bundle is completed, the foreign object image is generated in all the images obtained by the reading operation, and a copy that is not desired by the user is generated. Is done. The multifunction device 1 of the present embodiment employs the technology described below for this problem.

  That is, the multifunction device 1 performs a reading operation at the reading position P before starting the document conveyance in the normal image reading operation, in addition to the normal image reading operation (image reading operation on the document). The multi-function device 1 determines whether or not the image data obtained by the reading operation includes image data generated by the foreign matter (hereinafter referred to as foreign matter image data), and the foreign matter image data is included. If it is, the position of the foreign matter (especially the position in the sub-scanning direction) is also detected based on the foreign matter image data.

  In order to realize the above functions, as shown in FIG. 2, the control unit 61 includes a foreign object image detection unit 611, a drive control unit 613, a reading control unit 614, an image processing unit 615, and a display control unit 617. It has the function of

  The foreign object image detection unit 611 includes a plurality of scanner units 22 when the document transported by the document transport unit 21 is out of the document glass (document reading position) 230 (before the document reading operation is started and before the document transport). A predetermined foreign object image is detected from the image data read at the position in the sub-scanning direction, and further, the position of the foreign object image in the sub-scanning direction is detected.

  That is, the foreign object image detection unit 611 detects the presence / absence of a foreign object image generated due to the foreign object based on the image data obtained by the reading operation by the scanner unit 22 and indirectly determines the presence / absence of the foreign object on the original glass. Detect. As described above, since the surface of the platen member 2131 provided at a position facing the document glass 230 in the transport path 213 is white, in the reading operation performed at the timing before the document reading operation starts, Light is emitted from the light source 222 of the scanner unit 22 to the surface of the platen member 2131 that is white.

  Therefore, if there is no foreign matter (other than white) on the original glass 230 and the platen member 2131 at the timing before starting the original reading operation, the image data for one line in the main scanning direction obtained at this timing is It has a relatively large pixel value corresponding to white uniformly in the main scanning direction.

  On the other hand, when foreign matter (other than white) exists on the original glass 230 and the platen member 2131, the image data for one line in the main scanning direction obtained at the timing before the start of the original reading operation has a relatively large pixel value. The pixel data includes pixel data whose pixel value is reduced due to the foreign matter.

  Based on this, the foreign object image detection unit 611 performs processing for detecting an image caused by the foreign object (hereinafter referred to as a foreign object image). That is, the foreign object image detection unit 611 includes pixel data having a relatively large pixel value among pixel data having a pixel value smaller than a predetermined threshold for image data obtained by the reading operation at the timing before the document reading operation is started. Is included, and when pixel data having a relatively large pixel value includes pixel data smaller than the threshold, pixel data smaller than the threshold is detected as the foreign object image data.

  Further, the foreign object image detection unit 611 is based on the image data read by the scanner unit 22 at a plurality of positions in the sub-scanning direction which are different when the first carriage 226 and the second carriage 227 are moved in the sub-scanning direction by the moving mechanism. Then, a position in the sub-scanning direction where no foreign object image exists in the image data for one line in the main scanning direction is detected.

  The drive control unit 613 drives and controls the moving mechanism including a motor (not shown) that moves the first carriage 226 and the second carriage 227 in the sub-scanning direction of the scanner unit 22. The moving mechanism is provided in the document reading mechanism 200. The drive control unit 613 controls the movement mechanism to move the reading position of the scanner unit 22 to a position in the sub-scanning direction where the foreign object image detected by the foreign object image detection unit 611 does not exist. FIG. 3 is a diagram illustrating a situation in which the reading position by the scanner unit 22 is changed from the reading position P to the reading position P ′ when the foreign matter D exists at the reading position P.

  A reading control unit (lighting control unit) 614 controls a document reading operation of the scanner unit 22. The reading control unit 614 controls the reading operation of each unit of the document reading mechanism 200 including the document conveying unit 21 and the scanner unit 22. In particular, in this embodiment, the reading control unit 614 causes the scanner unit 22 to perform a normal image reading operation for each document, and also causes the scanner unit 22 to perform a reading operation at a timing before the document reading operation starts. Further, the reading control unit 614 controls lighting of the light source 222 of the scanner unit 22.

  The image processing unit 615 performs various image processing on the image data. For example, the image processing unit 615 performs shading correction, level correction, image data acquired by the CCD 229, image data transferred from a personal computer connected via a network, a facsimile machine connected via a public line, or the like. Image processing such as correction processing such as gamma correction, chromatic aberration correction, MTF (Modulation Transfer Function) correction and scanner color correction, image data compression or expansion processing, and enlargement or reduction processing is performed.

  The display control unit 617 controls driving of the display unit 51. For example, the display control unit 617 displays a warning message or the like for the user on the display unit 51.

  Next, the configuration of the light source 222 of the scanner unit 22 will be described. 4 is a top view of the light source 222, and FIG. 5 is a side sectional view showing the light source 222 and the original glass extracted.

  As shown in FIG. 4, the light source 222 includes a light emitting element group in which a plurality of light emitting elements (white LEDs in this embodiment) are arranged in parallel in the main scanning direction. Two rows are arranged in the scanning direction. Let each light emitting element group be the light emitting element groups 200A and 200B, respectively. As described above, the light source 222 irradiates the original or the like conveyed to the position of the original glass 230, and is conveyed to the original reading position by both the two light emitting element groups 200A and 200B when reading the original. The original is irradiated (see FIG. 9C).

  As shown in FIG. 5, the light emitting element group 200A on the upstream side (forward side) in the document conveying direction is set to the direction of each light emitting element LA1 ... LAn so as to emit light toward the downstream side in the document conveying direction. ing. Further, the light emitting element group 200B on the downstream side (return side) in the document transport direction is set so that the light emitting elements LB1... LBn emit light toward the upstream side in the document transport direction. The direction of each light emitting element LA1... LAn, light emitting element LB1... LBn and the light emitting elements LA1... LAn and light emitting elements LB1. The height position of the light source 222 is set.

  Further, during the reading operation by the scanner unit 22 at the timing before the start of the original reading operation, one of the upstream light emitting element group 200A in the original conveying direction and the downstream light emitting element group 200B in the original conveying direction one by one. Irradiated alternately, the scanner unit 22 reads and acquires an image on the original glass 230 at each reading position P by each of the light emitting element groups.

  4 and 5, a slit 2261 is provided at a position on the first carriage 226 between the light emitting element groups 200A and 200B in the sub-scanning direction. A first mirror 223 is disposed below the slit 2261, and an image irradiated by the light emitting element groups 200 </ b> A and 200 </ b> B through the slit 2261 is displayed on the first mirror 223, the second mirror 224, the third mirror 225, The image is read by the CCD 229 through the imaging lens 228.

  Next, a series of processes when the multifunction device 1 detects foreign matter on the original glass will be described. FIG. 6 is a flowchart showing a series of processes when the multifunction device 1 detects foreign matter on the original glass. FIG. 7 is a flowchart showing image reading processing, and FIG. 8 is a flowchart showing abnormal image detection processing.

  First, a description will be given with reference to FIG. For example, when a copy operation start instruction is input from the user by pressing the start button 55 (YES in S1), the reading control unit 614 scans the scanner unit 22 before the document transport unit 21 transports the document on the document tray 211. Then, the image on the original glass is read (S2). Subsequently, the foreign object image detection unit 611 performs processing for detecting a foreign object image from the image read by the scanner unit 22 (S3). In S3, the foreign object image detection unit 611 also detects the position of the foreign object image in the sub-scanning direction when detecting the foreign object image.

  With reference to FIG. 7, the image reading operation before document conveyance in S2 will be described. First, the drive control unit 613 causes the moving mechanism to move the light source 222 and the like of the scanner unit 22 to the foreign matter image detection reading start position in the sub-scanning direction (S201). The foreign matter image detection reading start position is a position upstream of the reading position P at the time of reading the document by a predetermined distance in the document transport direction (sub-scanning direction).

  After the drive control unit 613 moves the light source 222 and the like of the scanner unit 22 to the reading start position for foreign object image detection by the moving mechanism, the reading control unit 614 causes the scanner unit 22 to perform a reading operation at the position (S202, S202). S203). Specifically, at this position, the reading control unit 614 first causes the scanner unit 22 to emit only the forward-side light emitting element group 200A and irradiate the original glass 230 (see FIG. 9A). In this state, the image on the original glass 230 is read (S202). Subsequently, at the same position, the reading control unit 614 causes the scanner unit 22 to emit only the light emitting element group 200B on the return side and irradiate the original glass 230 (see FIG. 9B). The image on the glass 230 is read (S203).

  After the reading operations in S202 and S203, the drive control unit 613 determines whether the reading operation position has reached the reading end position from the reading start position for detecting a foreign image such as the light source 222 of the scanner unit 22 by the moving mechanism. Determination is made based on the moving distance (S204), and if the reading operation position has not reached the reading end position (NO in S204), the drive control unit 613 uses the light source 222 of the scanner unit 22 and the like as a document to the moving mechanism. A predetermined distance is moved downstream in the transport direction (sub-scanning direction) (S205). Then, at the position after the movement, the reading control unit 614 causes the scanner unit 22 to perform the reading operations of S202 and S203. The predetermined distance is determined in accordance with the number of image data to be sampled between the foreign matter image detection reading start position and the reading end position. For example, if 10 pieces of image data are required between the foreign matter image detection reading start position and the reading end position, scanning is performed from the foreign matter image detection reading start position. This is a distance obtained by dividing the distance to the reading end position into nine equal parts.

  In this manner, the scanner unit 22 performs image data (hereinafter referred to as forward-side data) on the original glass 230 when only the forward-side light emitting element group 200A is irradiated at a certain distance from the foreign matter image detection reading start position. And data of the image on the original glass 230 (hereinafter referred to as return side data) obtained by irradiation only of the light emitting element group 200B on the return side is acquired and stored. FIG. 10A is a graph showing an example of the acquired forward-side data and return-side data, with the pixel value (output value of the CCD 229) as the vertical axis and the sub-scanning direction position as the horizontal axis.

  Next, the abnormal image detection process in S3 will be described with reference to FIGS. The abnormal image detection unit 611 compares the forward-side data and the return-side data obtained as described above with a predetermined threshold value (S301). The threshold value is appropriately set to a pixel value that is assumed to indicate a foreign object (for example, black) on the document glass.

  In the comparison with the threshold value, if there is no pixel value equal to or less than the threshold value in either the forward side data or the return side data (YES in S302), the abnormal image detecting unit 611 is on the original glass 230 at the reading position P. Then, it is determined that there is no foreign matter (dirt) on the platen member 2131 (S313), and the abnormal image detection process is terminated.

  In the comparison with the threshold value, if a pixel value equal to or less than the threshold value exists in the forward side data and the return side data (NO in S302), the abnormal image detection unit 611 is formed by the forward side data and the return side data. A distribution width A of data indicating a foreign matter image in the sub-scanning direction is calculated (S303). That is, as shown in FIG. 10B, the abnormal image detection unit 611 performs a binarization process on each of the forward side data and the return side data based on whether or not the pixel value is equal to or greater than a threshold value. Further, a logical sum (indicating the distribution width A) of the values of the forward side data and the return side data after the binarization processing is calculated.

  Based on the data indicated by the calculated logical sum, the abnormal image detection unit 611 determines a sub-scanning direction position where no pixel value equal to or less than the threshold value exists, that is, a sub-scanning direction position where no foreign matter exists near the reading position P. Calculate (S304). However, the abnormal image detection unit 611 sets the position in the sub-scanning direction where the pixel value indicates white based on the forward-side data and return-side data before binarization as a position where no foreign matter exists in the original glass 230. It may be calculated.

  Subsequently, the abnormal image detection unit 611 determines whether or not the distribution width A of the data indicating the foreign object image is equal to or larger than a predetermined threshold A ′ (S305), and based on the determination result, the reading position It is determined whether the foreign matter on P is a foreign matter on the original glass 230 or a foreign matter on the platen member 2131 (S310, S316).

  That is, when the original glass 230 is irradiated with the light emitting element group 200A or the light emitting element group 200B in S302 and S303, the light emitting element group 200A and the light emitting element group 200B are respectively in the sub-scanning direction. Since irradiation is performed toward the position of the original glass 230 positioned between the groups 200B, when there is a foreign object on the original glass 230, the platen member 2131 provided behind the original glass 230 as viewed from the scanner unit 22 is displayed on the platen member 2131. The shadow of the foreign matter is projected, and the CCD 229 reads both the foreign matter and the shadow of the foreign matter. In this case, as shown in FIGS. 9 (a) and 9 (b), the image D by irradiation with each light emitting element group 200 </ b> A and light emitting element group 200 </ b> B read by the CCD 229 has a position in the sub-scanning direction on the platen member 2131. Projected differently. For this reason, when the image D of both the foreign matter and the shadow of the foreign matter is read by the CCD 229, the distribution width in the sub-scanning direction of the pixel values indicating both the foreign matter and the shadow of the foreign matter is shown in FIG. As shown by logical sum, it shows a relatively large width.

  On the other hand, when foreign matter is present on the platen member 2131 during irradiation by the light emitting element group 200A and the light emitting element group 200B, as shown in FIGS. 11A and 11B, the projection is made on the platen member 2131. The shadow of the foreign object is slight. For this reason, as shown in FIG. 12 (a), the foreign object images read by the light emitting element group 200A and the light emitting element group 200B read by the CCD 229 have different positions in the sub-scanning direction on the platen member 2131. The distribution width of the pixel values indicating the foreign object image is relatively small as shown by the logical sum in FIG. 12B (the original glass 230 shown by the logical sum in FIG. 10B). The width is smaller than when there is a foreign object on top).

  Based on this, the threshold value A ′ is set to a value of a distribution width that is assumed to have a foreign object on the original glass 230, so that the scanner unit 22 can compare the distribution width A with the threshold value A ′. It is possible to determine whether the foreign matter that is the basis of the captured foreign matter image is a foreign matter on the original glass 230 or a foreign matter on the platen member 2131.

  In other words, if the distribution width A is equal to or greater than the threshold A ′ (YES in S305), the abnormal image detection unit 611 determines that the foreign object exists on the original glass 230 (S306). On the other hand, if the distribution width A is not equal to or greater than the threshold A ′ (NO in S305), the abnormal image detection unit 611 determines that the foreign substance exists on the platen member 2131 (S312). If the abnormal image detection unit 611 determines that the foreign matter exists on the platen member 2131, the foreign matter is behind the original when viewed from the scanner unit 22 when reading the original, and does not adversely affect the reading of the original. The abnormal image detection process ends.

  If the abnormal image detection unit 611 determines that the foreign object exists on the original glass 230, the abnormal image detection unit 611 generates white foreign object detection data (S307). For example, the abnormal image detection unit 611 inverts one of the values on the forward side data and the return side data, and calculates the sum with the other value. In the present embodiment, as shown in FIG. 10C, the abnormal image detection unit 611 inverts the value of the return side data and calculates the sum with the value of the forward side data, thereby obtaining white foreign object detection data. Is generated.

  Subsequently, the abnormal image detection unit 611 has a distribution width B in which the pixel value (output value of the CCD 229) is within a predetermined range in the distribution width region of the foreign object image indicated by the white foreign object detection data. Is calculated (S308). For example, as illustrated in FIG. 10D, the abnormal image detection unit 611 distributes pixel values that are equal to or less than the threshold value by using a threshold value indicating that the forward side data is a foreign object. a is calculated, and for the inverted value of the return-side data, a distribution b of pixel values that is equal to or greater than the threshold is calculated by binarization using a value obtained by inverting the threshold indicating the foreign matter. To do. Then, the abnormal image detection unit 611 has a width of a region sandwiched between the distribution a and the distribution b, that is, a distribution region having a pixel value that is larger than the threshold value indicating the foreign substance and smaller than the inverted threshold value. Is calculated as a distribution width B.

  For example, the forward side data and the return side data are as shown in FIG. 10A because when the foreign object is black, both the foreign object and the foreign object shadow appear as pixel values indicating a black image. On the other hand, when the foreign matter is white, as shown in FIG. 13A, the forward side data and the return side data, the value indicating the foreign matter itself appears as a value indicating white, and the shadow of the white foreign matter is black. It appears as a value indicating the image of. For this reason, when the foreign object is white, the abnormal image detection unit 611 inverts the value of the return side data and calculates the sum with the value of the forward side data, thereby showing the distribution shown in FIG. When the distribution width B is calculated in the same manner as in FIG. 13, it is as shown in FIG.

  That is, it is assumed that the distribution width B of the black foreign image is often smaller than the distribution width B of the white foreign image. Based on this, a value assumed to be the distribution width B of the white foreign object image is determined in advance as a threshold B ′, and the threshold B ′ is compared with the distribution width B calculated in S308, It is possible to determine whether the foreign matter on the original glass 230 is black or white.

  The abnormal image detection unit 611 determines whether or not the distribution width B calculated in S308 is greater than or equal to the threshold B ′ (S309), and if the distribution width B is greater than or equal to the threshold B ′ (YES in S309). Then, it is determined that the foreign matter on the original glass 230 is white (S310). On the other hand, if the distribution width B is not equal to or greater than the threshold B ′ (NO in S309), the abnormal image detection unit 611 determines that the foreign matter on the original glass 230 is black (S311).

  Returning again to FIG. If it is determined that there is no foreign object image in the abnormal image detection process in S3 (NO in S4), the reading control unit 614 immediately causes the document conveying unit 21 and the scanner unit 22 to start a document reading operation (S8). The control unit 61 causes the image forming unit 40 to form an image based on the read document image (S9).

  If it is determined in the abnormal image detection process of S3 that there is a foreign object image (YES in S4), the display control unit 617 displays on the display unit 51 when the foreign object image exists on the platen member 2131. Then, a message that foreign matter is present on the platen member 2131 is displayed (S10). Thereafter, the process proceeds to S8.

  When the foreign object image exists on the original glass 230, the drive control unit 613 moves the position of the scanner unit 22 in the sub-scanning direction to the calculated position where the foreign object does not exist. (S6). This is because, if the foreign matter on the original glass 230 is left unattended, it is read by the scanner unit 22 during the original reading operation and an image is formed as black or white stripes. The display control unit 617 causes the display unit 51 to display a message indicating that there is a foreign object on the platen member 2131 (S7). Thereafter, the process proceeds to S8.

  The present invention is not limited to the configuration of the above embodiment, and various modifications can be made. For example, when the foreign object image detection process before the start of the document reading operation is performed, for example, when the operation is interrupted by a jam or the like while the leading edge of the document is approaching the reading position P in the conveyance by the document conveying unit 21, The forward side data includes images of both the document leading edge and the shadow of the document leading edge projected on the platen member 2131, while the return side data includes the image of the document leading edge but the document leading edge. Since the shadow is not projected onto the platen member 2131, the shadow image of the leading edge of the document is not included. Based on this, the abnormal image detection unit 611 detects a foreign object image from one of the forward side data and the return side data (forward side data in the present embodiment), and the foreign object image is detected from the other data. If not detected, the foreign object image can be determined as an image showing a shadow of the document.

  In the above embodiment, the configurations and processes shown in FIGS. 1 to 13 are merely examples, and the present invention is not limited to the embodiment. For example, in the above embodiment, the image pickup device of the scanner unit 22 has been described as the CCD 229, but other image pickup devices such as CIS may be used.

1 is a longitudinal sectional view schematically showing an internal configuration of a multifunction machine 1 that is an embodiment of an image reading apparatus and an image forming apparatus according to the present invention. FIG. 3 is a block diagram illustrating an electrical configuration of the multifunction machine. FIG. 6 is a diagram illustrating a situation in which a reading position by a scanner unit is changed from a reading position P to a reading position P ′ when a foreign substance D exists at the reading position P. It is a top view of a light source. It is a sectional side view which extracts and shows a light source and original glass. 5 is a flowchart showing a series of processing when foreign matter is detected on an original glass by a multifunction machine. It is a flowchart which shows an image reading process. It is a flowchart which shows an abnormal image detection process. (A) is a figure which shows a mode that the foreign material on an original glass is irradiated by the light emitting element group of a forward side, (b) is a figure which shows a mode that a foreign substance on an original glass is irradiated by the light emitting element group of a return side, (c) ) Is a diagram showing a state in which foreign matter on the original glass is irradiated by the light emitting element groups on the forward side and the return side. (A) is a graph showing forward side data and return side data in a graph with the pixel value on the vertical axis and the sub-scanning direction position on the horizontal axis. b) shows the data after the binarization processing of the forward side data shown in (a), the data after the binarization processing of the return side data, and the logical sum of these, and (c) shows the forward side data and A graph showing the inverted return-side data with the pixel value on the vertical axis and the position in the sub-scanning direction on the horizontal axis, and (d) is a graph after binarization processing of the forward-side data shown in (c) It is a figure which shows the data after the binarization process of data, return side data, and these logical sums. (A) is a figure which shows a mode that the foreign material on a platen member is irradiated by the light emitting element group of a forward side, (b) is a figure which shows a mode that a foreign substance on a platen member is irradiated by the light emitting element group of a return side, (c) ) Is a diagram showing a state in which the foreign matter on the platen member is irradiated by the light emitting element groups on the forward side and the return side. The image data of the black foreign matter and shadow on the platen member are shown, and (a) is a graph showing the foreside data and the return side data with the pixel value on the vertical axis and the sub-scanning direction position on the horizontal axis. b) shows the data after the binarization processing of the forward side data shown in (a), the data after the binarization processing of the return side data, and the logical sum of these, and (c) shows the forward side data and A graph showing the inverted return-side data with the pixel value on the vertical axis and the position in the sub-scanning direction on the horizontal axis, and (d) is a graph after binarization processing of the forward-side data shown in (c) It is a figure which shows the data after the binarization process of data, return side data, and these logical sums. (A) is a graph showing forward side data and return side data in a graph with the pixel value on the vertical axis and the sub-scanning direction position on the horizontal axis. b) shows the data after the binarization processing of the forward side data shown in (a), the data after the binarization processing of the return side data, and the logical sum of these, and (c) shows the forward side data and A graph showing the inverted return-side data with the pixel value on the vertical axis and the position in the sub-scanning direction on the horizontal axis, and (d) is a graph after binarization processing of the forward-side data shown in (c) It is a figure which shows the data after the binarization process of data, return side data, and these logical sums.

Explanation of symbols

1 MFP 200 Original Reading Mechanism 200A, 200B Light Emitting Element Group 21 Original Conveying Unit 2131 Platen Member 22 Scanner Unit 222 Light Source 229 CCD
230 Document Glass 40 Image Forming Unit 61 Control Unit 611 Foreign Object Image Detection Unit 613 Drive Control Unit 614 Reading Control Unit 615 Image Processing Unit 617 Display Control Unit

Claims (8)

A plurality of light emitting element groups arranged in parallel in the main scanning direction are arranged in two rows in the sub-scanning direction, and an irradiation mechanism for irradiating the document and a document glass extending in the main scanning direction at a predetermined document reading position, An image sensor that optically reads reflected light of an image irradiated by each light emitting element group directed to a predetermined position of the original glass serving as a position between the light emitting element groups in a scanning direction. An original reading unit;
A document transport unit that transports a document in the sub-scanning direction of the document reading unit with respect to the document reading position;
A lighting control unit that controls lighting by each of the light emitting element groups;
When the document transported by the document transport unit is out of the document reading position, an image read by the illumination by lighting of the one light emitting element group by the document reading unit, and the other light emitting element group An image reading apparatus comprising: a foreign object image detection unit configured to detect an image of a foreign object adhering to the original glass based on an image read by irradiation by lighting. A platen member for guiding the conveyance of the document at a position spaced apart from the document glass on the side opposite to the document reading unit;
The foreign object image detection unit has a foreign object image read when the one light emitting element group is turned on and a foreign object image read when the other light emitting element group is turned on in a predetermined width or more in the sub-scanning direction. 2. The image reading apparatus according to claim 1, wherein the foreign substance image is determined to be an image of a foreign substance existing on the original glass when being distributed over the original glass.   The foreign object image detection unit has a foreign object image read when the one light emitting element group is turned on and a foreign object image read when the other light emitting element group is turned on in a sub-scanning direction or more. If the width indicating the output value range of the image sensor corresponding to a predetermined white color is greater than or equal to a predetermined value between the two foreign object images, The image reading apparatus according to claim 2, wherein the foreign matter image is determined as an image of a white foreign matter existing on the original glass. A platen member for guiding the conveyance of the document at a position spaced apart from the document glass on the side opposite to the document reading unit;
The foreign matter image detection unit has a foreign matter image read when the one light emitting element group is turned on and a foreign matter image read when the other light emitting element group is turned on less than a predetermined width in the sub-scanning direction. The image reading apparatus according to claim 1, wherein, when distributed, the foreign matter image is determined to be an image of foreign matter existing on the platen member.   The foreign object image detection unit inverts one of the value of the image sensor read by lighting of the one light emitting element group and the value of the image sensor read by lighting of the other light emitting element group. 5. The image reading apparatus according to claim 1, wherein an added value of the two values is calculated, and a midpoint of the width in the sub-scanning direction indicated by the added value is detected as the center of the foreign matter. .   The foreign object image detection unit is configured to read the value of the imaging element read by lighting one of the light emitting element groups when a leading end of the document conveyed by the document conveying unit is approaching a document reading position of the document reading unit. Indicates a foreign object image, and when the value of the image sensor read by turning on the other light emitting element group does not indicate the foreign object image, the foreign object image is determined as an image showing a shadow of the document. The image reading apparatus according to claim 1.   The image reading apparatus according to claim 1, wherein the document reading unit includes a white LED array as the light emitting element. An image reading apparatus according to any one of claims 1 to 7,
An image forming apparatus comprising: an image forming unit that forms an image on a recording medium based on a document image read by the document reading unit.

Images