JP5992360B2 - Image reading apparatus and image forming apparatus having the same - Google Patents

Description

  The present invention relates to an image reading apparatus that reads a document. The present invention also relates to an image forming apparatus provided with the image reading apparatus.

  The image reading device obtains image data by guiding light reflected by the document to an image sensor. The image reading apparatus may be provided in an image forming apparatus such as a multifunction machine, a copier, or a FAX apparatus. Some image reading apparatuses perform document size detection in order to output image data at an appropriate size and to recognize a range to be read in a document. An example of an apparatus for performing such document size detection is described in Patent Document 1.

  Specifically, Patent Document 1 discloses a line sensor that receives optical information from a document and converts it into an electrical signal, an A / D converter that converts the output of the line sensor into digital data, and at least control of image reading processing. A control unit that performs the operation and a detection unit that detects opening and closing of the platen cover are provided. When the detection unit detects that the platen cover is about to be closed, the first scanning is performed, and then the platen cover is closed. In this state, there is described an image reading apparatus that performs a second scan in the main scanning direction of a document, and the control unit determines a document size based on a line sensor output obtained by these two scans. With this configuration, an attempt is made to reliably determine the size of the document (see Patent Document 1: Claim 1, Claim 3, paragraph [0026], etc.).

Japanese Patent Laid-Open No. 11-075025

  For example, the image reading apparatus is provided with a contact glass on the upper surface of the main body on which a document is placed with a reading surface facing downward. A lamp is provided below the contact glass, and light is irradiated from below the document. Further, a document holding plate that is opened and closed in the vertical direction is attached as a cover for pressing the document. Alternatively, instead of the document holding plate, a document transport device that transports the document to the reading position can be opened and closed in the vertical direction, and the document transport device is sometimes used as a cover.

  In such an image reading apparatus, reading may be performed to detect the size of the document in the main scanning direction. Here, the color of the lower surface of the portion that holds the document (the color of the mat on the lower surface of the cover) corresponds to white, which is the most commonly used paper color, and is usually white. When the cover is completely closed, if the background color of the original is white, even if the original is scanned, the boundary between the part of the original and the part of the original in the image data cannot be read accurately. For this reason, it is difficult to accurately detect the size of the document when reading after the cover is closed.

  In view of this, some image reading apparatuses perform reading when a cover or the like is closed to some extent in order to detect the size of the original before reading a full-fledged original (sometimes referred to as “pre-scan”). If the light is directed toward the contact glass and scanned before the cover is completely closed, the light leaks in a portion where there is no document. Leaked light that is not reflected is not incident on the image sensor. As a result, the pixel value of the pixel that has read the portion with the original is bright (white), and the pixel value of the pixel that has read the portion without the original is dark (black). In the line image data, the boundary position between the bright part (the part with the original) and the dark part (the part without the original) varies depending on the size of the original. Therefore, the length of the document on the contact glass in the main scanning direction can be detected by prescanning.

  In general, in order to detect the size of the document in the main scanning direction, the boundary position is determined by comparing the pixel value of each pixel of the image data of the line obtained by reading with a predetermined threshold value. Specifically, for each pixel of the image data, it is determined whether the pixel value is brighter than a threshold value. Then, a boundary between a pixel having a bright pixel value equal to or greater than the threshold and a pixel having a pixel value darker than the threshold is determined as a boundary between a portion where the document is present and a portion where the document is not present.

  In such an image reading apparatus that performs document size detection, a sensor for detecting that the cover is closed to some extent is provided in order to perform document size detection before the cover is completely closed. In other words, a sensor is provided that detects that the cover has been closed to some extent and outputs a trigger signal to start reading for document size detection.

  Such a sensor is provided with an abutting portion (for example, a protrusion) that contacts the lower surface of the cover (the surface that holds the document). The position of the contact portion changes according to the amount that the cover is closed to some extent. When the position of the contact portion moves to a predetermined position, the output of the sensor is switched. Due to the change in the output of the sensor, it is detected that the cover has been tilted to some extent (closed), and reading (pre-scanning) for document size detection is executed.

  Here, the contact portion is worn by repeated opening and closing of the cover. In addition, the contact portion is often made of a resin such as plastic, and wear depends on how the cover is closed. When the wear of the contact portion proceeds, the document size is detected after the cover is closed more than when there is no wear. In other words, the more the contact portion wears, the closer the distance between the contact glass and the cover when the document size is detected, and the smaller the angle of the cover with respect to the contact glass. For this reason, when the wear of the contact portion progresses, light is easily reflected on the lower surface of the cover at a portion where there is no document when reading for document size detection.

  Then, in the image data obtained by reading for document size detection, the pixel value of the pixel that has read a portion without a document is a bright (white) pixel value compared to when there is no wear.

  However, in the conventional image reading apparatus, the threshold value for determining the boundary between a certain part of the document and a part without the document in the image data is a fixed value. More specifically, the threshold value is a fixed value that is set in advance at the time of shipment of the image reading apparatus or the like and is set so that the size of the document is accurately detected when there is no wear on the contact portion. Accordingly, there is a problem that the size of the original in the main scanning direction cannot be detected more accurately as the contact portion of the sensor is worn.

  Here, Patent Document 1 describes that when the platen cover is about to be closed by an open / close detection unit having a protrusion in contact with the lower surface of the cover (how much it is closed is unknown). (See Patent Document 1: Paragraph [0036], FIG. 1 and the like). However, there is no description regarding the wear of the protrusions of the open / close detection unit. Therefore, when a normal document (for example, the background is white) is read, the problem of the accuracy of the detected size due to wear of the contact portion of the sensor cannot be solved.

  In the present invention, in view of the above-described problems of the prior art, document size detection is performed after the cover is closer to the contact glass than when there is no wear due to wear of the sensor parts due to repeated opening and closing of the cover. Even if this happens, the document size is accurately detected.

In order to achieve the above object, an image reading apparatus according to a first aspect of the present invention includes a contact glass on which a document is placed, and a cover portion that is opened and closed in a vertical direction and presses the document placed on the contact glass. An open / close detection unit that includes a contact part that is in contact with the cover part in the middle of being closed and that is pushed into the cover part as the cover part is closed, and whose output changes according to the amount of pressing of the contact part; And a lamp that irradiates light toward the document and an image sensor that reads in line units based on the reflected light reflected from the document. For detecting the size of the original document, a reading mechanism for reading and detecting the contact glass, and generating image data based on the output of the image sensor The pixel value of each pixel of the image reading unit and the detected read image data, which is the image data obtained by the size detection reading, is compared with the threshold value for detecting the boundary position between the portion where the document is present and the portion where the document is absent and to detects the boundary position of the part and the document is no portion of the document, detection processing unit for performing document size detection process of detecting the size of the document placed on the contact glass on the basis of the boundary position data In the first case where the cover part is opened and closed a predetermined number of times from the start of use or from the previous correction of the threshold value, the detection reading at a position where no document is placed The reference image data obtained by comparing the pixel value of the image data with the pixel value at the corresponding position in the reference image data as the reference of the detected read image data stored in the memory. In the second case where the amount of deviation between the detected data and the detected read image data exceeds a predetermined allowable range, or the predetermined number of times of the cover portion from the start of use or from the correction of the threshold value. The reference image data obtained by performing a comparison based on the pixel value of the detected read image data at the position where the document is not placed after opening / closing and the pixel value at the corresponding position in the reference image data, and the reference image data In the third case where the amount of deviation between the detected read image data exceeds a predetermined allowable range, the detection processing unit changes the threshold value in a bright direction to correct the threshold value, and the corrected threshold value An image reading apparatus that performs the document size detection process based on the above.

  According to the present invention, it is possible to correct a threshold value for detecting a boundary position between a portion where a document is present and a portion where a document is absent. As a result, the sensor part (contact part) is worn due to repeated opening and closing of the cover part, and even when the cover part comes closer to the contact glass than when there is no wear, the document size detection is executed. The size of the detected document can be accurately detected. It is possible to provide an image reading apparatus that accurately detects a document size even when sensor parts are worn.

1 is a diagram illustrating a schematic configuration of a multifunction machine. It is a figure which shows an image reading apparatus. FIG. 6 is a diagram illustrating a state where a document conveying unit is opened. FIG. 6 is a diagram illustrating a state where a document conveying unit is opened. FIG. 6 is a diagram illustrating a state in the middle of closing a document conveying unit. 1 is a block diagram illustrating a configuration of a multifunction machine. It is a block diagram which shows the structure of an image reading apparatus. It is a figure which shows the state which looked at the image reading part from upper direction. It is a figure for demonstrating abrasion of a contact part. It is a flowchart which shows the flow of the correction | amendment of the threshold value by a 1st method. It is a flowchart which shows the flow of correction | amendment of the threshold value by a 2nd method. It is a flowchart which shows the flow of correction | amendment of the threshold value by a 3rd method.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. However, each element such as configuration and arrangement described in this embodiment does not limit the scope of the invention and is merely an illustrative example.

(Outline of image forming apparatus)
First, an outline of an electrophotographic multifunction peripheral 200 (corresponding to an image forming apparatus) including the image reading apparatus 100 according to the embodiment will be described with reference to FIG. FIG. 1 is a diagram illustrating a schematic configuration of the multifunction device 200.

  An image reading apparatus 100 including an image reading unit 1 and a document conveying unit 2 is disposed above the multifunction device 200 of the present embodiment. Details of the image reading apparatus 100 will be described later. The document transport unit 2 will be described as an example of a cover unit for suppressing the document d. However, instead of the document transport unit 2, a plate-shaped document pressing plate having no document transport function may be used as the cover unit. Good.

  Further, as indicated by a broken line in FIG. 1, an operation panel 3 is provided on the front side of the image reading unit 1. The operation panel 3 includes a touch panel type display unit 30 (for example, a liquid crystal display panel) that displays setting keys of the multifunction device 200 and the state of the multifunction device 200 and receives user inputs. The operation panel 3 also includes hard keys such as a numeric keypad 31 for inputting numbers and a start key 32 for receiving a job execution start instruction.

  The multifunction device 200 according to the present embodiment includes a sheet feeding unit 4a, a transport unit 4b, an image forming unit 5a, an intermediate transfer unit 5b, a fixing unit 5c, and the like inside the main body. The main body of the multifunction device 200 is provided with a plurality of paper feed units 4a. Each paper feed unit 4a accommodates a plurality of sheets used for printing of each size such as A4 or letter size. Each paper feed unit 4a includes a paper feed roller 41 that is driven to rotate. At the time of printing, one of the paper feed rollers 41 rotates to feed the paper to the transport unit 4b one by one.

  The transport unit 4b is a path for transporting paper within the apparatus. The transport unit 4b includes a guide plate for guiding the paper, a pair of transport rollers 42 that rotate and transport the paper (a total of three from 42a, 42b, and 42c from the top in FIG. 1) And a registration roller pair 43 that feeds the sheet to the secondary transfer roller 56 in accordance with the transfer timing of the toner image. In addition, a pair of discharge rollers 45 for discharging the sheet after completion of fixing to the discharge tray 44 is also provided.

  The image forming unit 5a includes a plurality of image forming units 50 (50Bk for black, 50Y for yellow, 50C for cyan, 50M for magenta) and an exposure device 51. Each image forming unit 50 includes a photosensitive drum that is rotatably supported, and a charging device, a developing device, and a cleaning device disposed around the photosensitive drum. The exposure device 51 outputs laser light while turning it on and off based on the image data read by the image reading unit 1, and scans and exposes each photosensitive drum. A toner image is formed on the peripheral surface of the photosensitive drum by each image forming unit 50 and the exposure device 51.

  The intermediate transfer portion 5b receives the primary transfer of the toner image from each image forming unit 50 and performs the secondary transfer on the paper. The intermediate transfer unit 5b includes primary transfer rollers 52Bk, 52Y, 52C, and 52M, an endless intermediate transfer belt 53, a drive roller 54, a plurality of driven rollers 55, a secondary transfer roller 56, and a belt cleaning device 57. Each primary transfer roller 52 </ b> Bk to 52 </ b> M sandwiches the corresponding photosensitive drum and the intermediate transfer belt 53. A transfer voltage is applied to each of the primary transfer rollers 52Bk to 52M.

  The intermediate transfer belt 53 is stretched around the drive roller 54 and the like, and rotates around the drive roller 54. The driving roller 54 sandwiches the intermediate transfer belt 53 with the secondary transfer roller 56. The toner images (black, yellow, cyan, and magenta colors) formed by each image forming unit 50 are sequentially transferred to the intermediate transfer belt 53 in a superimposed manner without deviation, and then applied with a predetermined voltage. The image is transferred onto the paper by the secondary transfer roller 56.

  The fixing unit 5c fixes the toner image transferred to the paper. The fixing unit 5c includes a heating roller 58 containing a heating element, and a pressure roller 59 that is in pressure contact with the heating roller 58. After passing through the nip between the heating roller 58 and the pressure roller 59, the toner image transferred to the paper is melted and heated. As a result, the toner image is fixed on the paper. The sheet that has passed through the fixing unit 5 c is discharged to the discharge tray 44.

(Configuration of Image Reading Apparatus 100)
Next, an example of the image reading apparatus 100 according to the embodiment will be described with reference to FIG. FIG. 2 is a diagram illustrating the image reading apparatus 100.

  The image reading apparatus 100 includes an image reading unit 1 that generates image data. In addition, the image reading apparatus 100 includes a document conveying unit 2 (corresponding to a cover unit) provided above the image reading unit 1. The document conveying unit 2 can be opened and closed in the vertical direction so as to swing the front side with respect to the placement reading contact glass 12 of the image reading unit 1 by the rotation shaft 2a (see FIG. 3).

  The document conveying unit 2 automatically and continuously conveys the document d to be read one by one to a reading position (a conveyance reading contact glass 11 described later). Specifically, the document d to be read is placed on the document tray 21. During reading, the document supply roller 22 feeds the document d from the document tray 21 one by one. The fed document d is guided to a plurality of transport rollers and guides, and passes through the upper surface of the transport reading contact glass 11 provided on the upper surface of the image reading unit 1. During this passage, the image reading unit 1 performs reading (a document conveyance path is indicated by a two-dot chain line).

  Next, the image reading unit 1 in the present embodiment will be described. The image reading unit 1 emits light toward the upper surface, reads the document d by the image sensor 68 based on the reflected light, and generates image data.

  On the left side of the upper surface of the image reading unit 1, a transparent plate-shaped transport reading contact glass 11 is arranged extending in a direction perpendicular to the paper surface of FIG. Further, a placement reading contact glass 12 having a transparent plate shape is disposed on the right side of the upper surface of the image reading unit 1 in a direction perpendicular to the paper surface. The placement reading contact glass 12 is provided on the upper surface of the image reading unit 1. When reading a document d such as a book one by one, the document transport unit 2 is lifted and the document d is placed with the reading surface facing downward.

  Further, as shown in FIG. 2, a reading mechanism 6 for reading each contact glass and document d in the housing of the image reading unit 1 includes a first moving frame 61, a second moving frame 62, a wire 63, a winding. A drum 64, a take-up motor 65 (see FIG. 7), a lens 66, a lamp 67 (for example, an LED or a cold cathode tube) that irradiates light on the original d in the main scanning direction, and light applied to the original d. An image sensor 68 is provided for reading the original d for each line and generating image data. The image sensor 68 reads the document d line by line based on the reflected light of the document d. In other words, the image reading unit 1 includes a reading mechanism.

  The first moving frame 61 supports a lamp 67 and a first mirror 611 that emit light upward. The second moving frame 62 supports the second mirror 622 and the third mirror 623. Further, the first moving frame 61 is disposed above the second moving frame 62. The lamp 67 and each mirror have a shape extending in the direction perpendicular to the paper surface of FIG.

  A plurality of wires 63 are attached to the first moving frame 61 and the second moving frame 62 (only one is shown in FIG. 2 for convenience). The other end of the wire 63 is connected to a take-up drum 64, and the take-up drum 64 rotates forward and backward using a take-up motor 65 (see FIG. 8) as a drive source. Thereby, the 1st moving frame 61 and the 2nd moving frame 62 move freely in a horizontal direction.

  Light is emitted from the lamp 67 toward the upper side of the conveyance reading contact glass 11 and the placement reading contact glass 12. The reflected light from the document d and the lower surface 2 e of the document transport unit 2 is reflected by the first mirror 611, the second mirror 622, and the third mirror 623 and guided to the lens 66. The lens 66 collects the reflected light and enters the image sensor 68.

  The image sensor 68 is, for example, a CCD (Charge Coupled Device) type line sensor in which a plurality of light receiving elements (photoelectric conversion elements) are arranged in three R, G, and B lines. The image sensor 68 converts the reflected light into an analog electrical signal corresponding to the image density (the intensity of the reflected light).

  Here, an example of a specific document reading operation will be described. First, in the case of reading the document d transported by the document transport unit 2, the first moving frame 61 is fixed to a lower position (reading position) of the transport reading contact glass 11 after the winding motor 65 is driven. . The lamp 67 irradiates the passing document d. On the other hand, when reading the document d placed on the placement reading contact glass 12, the first moving frame 61 and the second moving frame 62 are moved from the home position to the right of FIG. Move horizontally in the direction.

  Then, reading is performed in line units with respect to the main scanning direction (direction perpendicular to the document conveyance direction) of the document d, and reading in line units is continuously performed in the sub-scanning direction (document conveyance direction). The original image is converted into an electric signal, and one original d is read. When reading the document d placed on the placement reading contact glass 12, a line-by-line reading operation (movement of the irradiation position of the lamp 67) is performed from the left end of the placement reading contact glass 12 to the end of the document d. The entire original is read by sequentially performing up to the copy.

(Opening / closing and opening / closing detection of the document conveying unit 2)
Next, the opening and closing of the document conveying unit 2 as the cover unit and the opening and closing detection will be described with reference to FIGS. FIG. 3 is a diagram illustrating a state in which the document conveying unit 2 is opened. In FIG. 3, illustrations other than the image reading apparatus 100 are omitted. FIG. 4 is a diagram showing a state in which the document conveying unit 2 is opened. FIG. 5 is a diagram illustrating a state in the middle of closing the document conveying unit 2.

  The document conveying unit 2 is rotatably attached to the support member 2b around two rotation shafts 2a provided along the side of the image reading unit 1 on the back side of the main body. Thereby, the document conveying unit 2 rotates (rotates) with the front side of the image reading apparatus 100 as a free end and swings up and down on the front side, and opens and closes with respect to the upper surface of the image reading unit 1. Can take the attitude.

  A white guide plate 2 c is provided on the lower surface 2 e of the document conveying unit 2 that faces the conveyance reading contact glass 11 when the document conveying unit 2 is closed. The white guide plate 2 c has a position and a size that cover the conveyance reading contact glass 11. When the document conveying section 2 is closed, a gap is formed between the white guide plate 2c and the conveyance reading contact glass 11, which becomes a path through which the conveyed document d passes.

  A white mat 2d is provided at the position of the lower surface 2e of the document conveying unit 2 when the document conveying unit 2 is closed and facing the placement reading contact glass 12. The white mat 2d has a position and size covering the placement reading contact glass 12. In other words, when the document conveying unit 2 is completely closed, the white mat 2d covers the placement reading contact glass 12 from above. When the document conveying unit 2 is closed, the white mat 2d holds the document d so as not to move by suppressing the document d and the placement reading contact glass 12.

  Further, as shown in FIGS. 3 to 5, the image reading unit 1 is provided with an open / close detection unit 7 between the two rotating shafts 2 a of the document conveying unit 2. The open / close detection unit 7 includes a contact portion 71, a transmissive optical sensor 72, a spring 73 that biases the contact portion 71 upward.

  The contact portion 71 of this embodiment is made of resin (plastic). As shown in FIGS. 4 and 5, the contact portion 71 is a rod-like member extending in the vertical direction. The abutting portion 71 slides (moves) in the vertical direction according to the degree to which the document conveying portion 2 is opened. Specifically, as the document conveyance unit 2 is opened, the contact portion 71 is moved upward and protrudes from the upper surface of the image reading unit 1 by being biased by the spring 73. On the other hand, the upper end portion 71 u of the contact portion 71 contacts the lower surface 2 e of the document conveying portion 2 while the document conveying portion 2 is being closed. The abutting portion 71 is pushed downward as the document conveying portion 2 is tilted.

  A sensor interference part 71 b is provided at the lower end of the contact part 71. The transmissive optical sensor 72 is used to detect that the contact portion 71 (the sensor interference portion 71b at the lower end thereof) has reached a predetermined position and below a predetermined position. . In other words, the transmissive optical sensor 72 of the open / close detection unit 7 detects that the document conveying unit 2 is closed more than a predetermined angle. The transmissive optical sensor 72 is provided in the vicinity of the contact portion 71 (sensor interference portion 71b) when lowered. The transmissive optical sensor 72 includes a light emitting part and a light receiving part (not shown) provided so as to sandwich the contact part 71 (sensor interference part 71b).

  The spring 73 is provided below the contact portion 71 (lower end portion). The spring 73 is, for example, a coil spring. Further, the spring 73 is in the open state of the document conveying section 2, the contact section 71 does not completely protrude from the upper surface of the image reading section 1, and the sensor interference section 71 b comes above the optical path of the transmissive optical sensor 72 ( The contact portion 71 is urged upward so as not to block the optical path.

  While the document conveying unit 2 is being closed, the lower surface 2e of the document conveying unit 2 comes into contact with the contact portion 71, the contact portion 71 is pushed in, and the contact portion 71 (sensor interference unit 71b) starts to descend. The interference unit 71b starts to block the optical path between the light emitting unit and the light receiving unit of the transmissive optical sensor 72. The predetermined position of the sensor interference part 71b (contact part 71) is a position where the output value of the light receiving part is equal to or less than the reference value when light from the light emitting part is blocked by the sensor interference part 71b. The While the document conveying section 2 is tilted (closed) to a position where the position of the contact portion 71 (sensor interference portion 71b) is a predetermined position or a position below the predetermined position, sensor interference The unit 71b continues to block the optical path between the light emitting unit and the light receiving unit of the transmissive optical sensor 72.

  Further, when the document conveying unit 2 is opened, as the document conveying unit 2 is opened, the contact portion 71 is biased by the spring 73 and protrudes upward, so that the contact portion 71 (sensor interference portion). It can be detected that the document conveying section 2 is lifted as the position 71b) moves upward from a predetermined position.

  In the MFP 200 of the present embodiment, the document conveying unit 2 is closed to a position where the position of the abutting unit 71 (sensor interference unit 71b) is determined in advance (the output value of the light receiving unit is equal to or less than the reference value). The output signal from the open / close detection unit 7 to the effect serves as a trigger to perform pre-scan for document size detection. In other words, when the abutting portion 71 is pushed in until the position of the lower end portion of the abutting portion 71 reaches a predetermined position in the middle of closing the opened document conveying portion 2 (of the abutting portion 71). When the pressing amount exceeds a predetermined amount), reading of the placement reading contact glass 12 for document size detection is executed.

(Hardware configuration of MFP 200)
Next, an example of a hardware configuration of the multifunction machine 200 according to the embodiment will be described with reference to FIG. FIG. 6 is a block diagram illustrating a configuration of the multifunction device 200.

  A main control unit 8 that performs overall control of the multifunction device 200 is provided. The main control unit 8 is provided with a CPU 81 as a central processing unit. In addition, a storage unit 82 composed of nonvolatile and volatile memories such as a random access memory (RAM), a read only memory (ROM), a hard disk drive (HDD), and a flash ROM is provided in the main control unit 8 (main control unit). 8 may be provided).

  The storage unit 82 stores programs, data, and the like for controlling the multifunction device 200. The main control unit 8 uses the program and data stored in the storage unit 82 to control each unit and perform printing. The main control unit 8 includes a main control unit that performs overall control, communication control, and image processing, an engine control unit that controls printing by performing ON / OFF of a motor that rotates an image forming and various rotating bodies, and the like. A plurality of types may be provided for each function. The main control unit 8 also includes a second image processing for performing image processing for printing and transmission based on image data processed by a first image processing unit 9 (details will be described later) provided in the image reading apparatus 100. A portion 83 is provided.

  The main control unit 8 is connected to the sheet feeding unit 4a, the conveyance unit 4b, the image forming unit 5a, the intermediate transfer unit 5b, the fixing unit 5c, the operation panel 3, and the like. The main control unit 8 controls the operation of each unit such as paper conveyance and toner image formation. In addition, user setting input contents and job execution instructions on the operation panel 3 are transmitted to the main control unit 8. The main control unit 8 is also connected to the image reading apparatus 100 and gives an operation instruction to the image reading apparatus 100. Then, the main control unit 8 receives the image data of the document d, and performs printing based on the image data (copy function). Further, the main control unit 8 can transmit the image data of the document d from the communication unit 84 to the external computer 300, and can perform printing based on the data received from the computer 300 (transmission function, printer function). .

(Hardware configuration of image reading apparatus 100)
Next, an example of a hardware configuration of the image reading apparatus 100 according to the embodiment will be described with reference to FIG. FIG. 7 is a block diagram illustrating a configuration of the image reading apparatus 100.

  The image reading apparatus 100 according to the present embodiment includes a document conveying unit 2 and an image reading unit 1. The document transport unit 2 is provided with a document transport control unit 20 that controls the operation of the document transport unit 2. The image reading unit 1 is provided with a reading control unit 10 (corresponding to a detection processing unit) that controls the operation of the image reading unit 1.

  First, the document conveyance control unit 20 will be described. The document conveyance control unit 20 is communicably connected to the main control unit 8 and the reading control unit 10. The document conveyance control unit 20 controls the operation of the document conveyance unit 2 in response to instructions and signals from the main control unit 8 and the reading control unit 10. The document conveyance control unit 20 is a substrate including an arithmetic processing circuit such as a CPU and a ROM or RAM as a storage device for storing control programs and data.

  The document conveyance control unit 20 communicates with the main control unit 8 and the reading control unit 10, receives instructions from the main control unit 8 and the reading control unit 10, and controls the operation of the document conveyance unit 2. When there is an instruction to read the document d from the main control unit 8, when the document d is placed on the document tray 21, the document transport motor 23 is driven to rotate the document d (for example, a document supply roller). 22) is rotated. A document tray sensor 24 is provided on the document tray 21 in order to detect whether or not the document d is placed on the document tray 21.

  The document tray sensor 24 is a sensor (for example, an optical sensor) that outputs differently when the document d is placed on the document tray 21 and when it is not placed. Based on the output of the document tray sensor 24, the document conveyance control unit 20 and the reading control unit 10 read whether the document d is placed on the document tray 21, read the conveyed document d, or place reading contact glass. 12 is read.

  Next, the image reading unit 1 and the reading control unit 10 will be described. The reading control unit 10 is communicably connected to the main control unit 8 and the document conveyance control unit 20. The reading control unit 10 receives instructions and signals from the main control unit 8 and controls the operation of the image reading unit 1. The reading control unit 10 is also provided with a control circuit 101 including an arithmetic processing circuit such as a CPU, a ROM 102 as a storage device for storing programs and data necessary for controlling the image reading apparatus 100, and a memory 102 including a RAM. It is a substrate.

  When the start key 32 of the operation panel 3 is pressed after setting a job for reading a document such as a copy, the reading control unit 10 receives an instruction to read the document from the main control unit 8 and receives the image reading device. Operation control of 100 original reading and transmission control of image data obtained by reading to the main control unit 8 are performed.

  Specifically, a winding motor 65 is connected to the reading control unit 10. The reading control unit 10 controls the rotation of the winding motor 65. And the reading control part 10 rotates the winding drum 64, and controls the movement of each moving frame. When reading the document d passing through the conveyance reading contact glass 11, the reading control unit 10 rotates the take-up motor 65 to move each moving frame below the conveyance reading contact glass 11. Further, when reading a document on the placement reading contact glass 12, the reading control unit 10 rotates the winding motor 65 to move each of the reference scanning point P in the sub-scanning direction (right direction of the image reading apparatus 100). Move the frame.

  The reading control unit 10 is connected to the open / close detection unit 7. An output value (output voltage or output current) of the open / close detection unit 7 (the light receiving unit) is input to the reading control unit 10. Based on the output of the open / close detection unit 7, the reading control unit 10 pushes the contact unit 71 as the position of the contact unit 71 (sensor interference unit 71b) reaches a predetermined position (document conveying unit 2). It is recognized that the document conveying section 2 has been lifted as the abutting portion 71 (sensor interference portion 71b) moves above a predetermined position.

  The reading control unit 10 is connected to each document detection sensor 14 (see FIG. 8). The reading control unit 10 detects the length in the sub-scanning direction of the document d placed on the placement reading contact glass 12 based on the output of each document detection sensor 14.

  The reading control unit 10 is connected to the lamp 67, the image sensor 68, the first image processing unit 9, and the like, and gives an instruction to read the document d, in other words, an instruction to drive.

  First, the lamp 67 is an LED lamp including red, green, and blue LEDs. The reading control unit 10 turns on the lamp 67 when performing reading (when causing the line sensor to perform reading). Further, the reading control unit 10 turns off the lamp 67 when the reading is completed.

  The image sensor 68 receives light applied to the document d, and outputs three types of analog electrical signals of R, G, and B for each pixel. The magnitude of the electrical signal varies depending on the amount of received light. The reading control unit 10 controls driving of the image sensor 68.

  The first image processing unit 9 is a part that processes image signals output from the pixels of the image sensor 68 to generate image data. The reading control unit 10 operates the first image processing unit 9 when performing reading.

  The first image processing unit 9 includes circuits such as a work memory 91, an A / D conversion unit 92, and a correction processing unit 93. The work memory 91 is a work area for processing image data. The A / D converter 92 quantizes the analog electrical signal of each pixel obtained by the image sensor 68 and converts it into a digital signal. For example, the A / D conversion unit 92 quantizes R, G, and B to 8 to 10 bits (24 to 30 bits in total). The correction processing unit 93 corrects distortion derived from characteristics of the lamp 67, the image sensor 68, and the like, such as gamma correction and shading correction, for the image data.

  The image data processed by the first image processing unit 9 is stored in the image memory 94 and then transferred to the main control unit 8. Further, after the second image processing unit 83 performs image processing, for example, image data is given to the exposure device 51.

  In this embodiment, an example in which the first image processing unit 9 is provided in the image reading unit 1 and the second image processing unit 83 is provided in the main control unit 8 will be described. For example, only one image processing unit is provided, Only one image processing unit may be configured to perform the processing of the first image processing unit 9 and the processing of the second image processing unit 83 in this description. In other words, only one image processing unit may be provided.

(Outline of document size detection)
Next, an outline of document size detection in the image reading apparatus 100 according to the embodiment will be described with reference to FIGS. FIG. 8 is a diagram illustrating a state in which the image reading unit 1 is viewed from above.

  The user places the document d on the placement reading contact glass 12 with the reading surface facing downward. In the multifunction device 200 of the present embodiment, the upper left corner of the placement reading contact glass 12 is the reference point P when the multifunction device 200 is viewed from above. The user places the original d by aligning the upper left corner of the original d with the reference point P.

  In the MFP 200 of the present embodiment, the length in the main scanning direction of the document d placed on the placement reading contact glass 12 is detected by reading a part of the left end of the document d.

  Specifically, as the position of the contact portion 71 (sensor interference portion 71b) reaches a predetermined position, the document conveying portion 2 is closed (the output value of the light receiving portion is equal to or less than the reference value). When an output signal from the open / close detection unit 7 is input to the reading control unit 10, the reading control unit 10 causes the reading mechanism 6 to perform reading for document size detection using the signal as a trigger. In other words, the reading control unit 10 causes the placement reading contact glass 12 to be read before the document conveying unit 2 is completely closed.

  Here, a boundary detection unit 103 is provided in the reading control unit 10 to detect the size of the document d in the main scanning direction. The boundary detection unit 103 is a circuit for performing document size detection processing in the main scanning direction. The boundary detection unit 103 may be realized by software by the control circuit 101 of the reading control unit 10 or a program, or may be provided in the first image processing unit 9.

  The boundary detection unit 103 is a pixel of each pixel included in image data (hereinafter referred to as “detected read image data”) obtained by reading the left end portion of the placement reading contact glass 12 for document size detection. The threshold value t1 is compared with a predetermined threshold value t1 to detect the boundary position between the pixel portion that reads the portion with the document d and the pixel portion that reads the portion without the document d in one line of the detected read image data To do. Note that the current threshold value t1 is stored in a nonvolatile manner as data in a storage device such as the memory 102.

  Specifically, the boundary detecting unit 103 performs image data for one line obtained by black and white synthesis from R, G, and B image data obtained as detected read image data (luminance information created from R, G, and B image data). Boundary detection processing is performed on the data. Note that the boundary detection unit 103 may perform boundary detection processing on image data for one line of any color of R, G, and B. Further, the boundary detection unit 103 may perform boundary detection on image data for one line that has been subjected to black and white synthesis and further subjected to edge processing. For this reason, the reading control unit 10 or the first image processing unit 9 includes a synthesis processing unit 104 that generates black and white image data from R, G, and B color image data, An edge processing unit 105 that performs filter processing may be provided.

  Then, the boundary detection unit 103 reads a pixel area of the detected read data that has a pixel value brighter than the threshold value t1 by reading a portion where the document d is present (a range in which the placed document d is read). The boundary position with the pixel region having a pixel value darker than the threshold value t1 (the range in which the placement reading contact glass 12 in the portion without the document d is read) is recognized by reading the portion without the document d. This is because, in the reading in a state where the document conveying unit 2 is not fully closed, the light of the portion where the document d does not exist is not reflected and leaks to the outside. As a result, the pixels in the portion where the document d does not exist have darker pixel values than the pixels in the portion where the document d exists.

  The reading control unit 10 (control circuit 101) obtains the size (width) in the main scanning direction of the document d placed on the placement reading contact glass 12 based on the detected boundary position. Specifically, in the present embodiment, the reading control unit 10 counts the number of pixels from the pixel corresponding to the position of the reference point P to the boundary position. The reading width in the main scanning direction per pixel is determined in terms of reading resolution (if the resolution is 600 dpi, 25.4 [mm] ÷ 600≈42.3 [μm] per pixel).

  Accordingly, the reading control unit 10 multiplies the number of pixels from the pixel corresponding to the position of the reference point P to the boundary position by the reading width in the main scanning direction per pixel, thereby obtaining the size of the document d in the main scanning direction. Ask for. Alternatively, data defining the size of the document d is stored in the memory 102 with respect to the number of pixels from the pixel corresponding to the position of the reference point P to the boundary position, and the reading control unit 10 refers to the data. The size of the document d in the main scanning direction may be obtained.

  In the present embodiment, an example in which the reading control unit 10 detects the size of the document d placed on the placement reading contact glass 12 in the main scanning direction will be described, but the boundary detection unit 103 and the threshold value t1 are shown. By providing the first image processing unit 9 with data, the first image processing unit 9 may detect the size of the document d in the main scanning direction.

  The length of the document d placed on the placement reading contact glass 12 in the sub-scanning direction (direction perpendicular to the main scanning direction) is provided along the back side of the placement reading contact glass 12. Detection is performed using the plurality of document detection sensors 14 (see FIG. 8). The document detection sensor 14 is a reflection type optical sensor. The output of each document detection sensor 14 is input to a reading control unit 10 described later. Then, the reading control unit 10 determines the length of the original d in the sub-scanning direction from the reference point P to the original detection sensor 14 that detects the presence of the original d, and the original that does not detect the presence of the original d from the reference point P. It is determined that the length is within the range up to the detection sensor 14.

(Change in reading timing over time for document size detection)
Next, with reference to FIG. 9, the change with time of the reading timing for detecting the document size will be described. FIG. 9 is a view for explaining the wear of the contact portion 71.

  In FIG. 9, the image reading apparatus 100 is illustrated in a simplified manner. Specifically, in FIG. 9, the document conveying unit 2 is illustrated in a plate shape. Further, regarding the image reading unit 1, only the outer frame of the housing, the contact part 71, and the placement reading contact glass 12 are shown.

  The abutting portion 71 is in contact with a part of the lower surface 2 e of the document conveying portion 2. For this reason, when the opening and closing of the document conveying unit 2 is repeated, the upper end portion 71u of the contact portion 71 is worn. In FIG. 9, a state in which the contact portion 71 is not worn is illustrated in the upper view, and a state in which the contact portion 71 is worn is illustrated in the lower view.

  When the contact part 71 is worn, the contact part 71 becomes shorter. As the wear of the contact portion 71 progresses, in order to push the contact portion 71 until the lower end portion of the contact portion 71 reaches a predetermined position, it is necessary to lower the document conveying portion 2 than before the wear. Therefore, when the wear of the contact portion 71 proceeds, the angle of the document conveying portion 2 with respect to the placement reading contact glass 12 when reading for document size detection is performed is more than that when the contact portion 71 is not worn. Becomes smaller. In other words, the distance L1 between the placement reading contact glass 12 and the lower surface 2e of the document conveying unit 2 when reading for document size detection is performed becomes short.

  As wear of the contact portion 71 progresses, the distance L1 between the contact portion 71 and the placement reading contact glass 12 becomes closer when reading the placement reading contact glass 12 for document size detection. For this reason, when the wear of the contact portion 71 progresses more than when there is no wear of the contact portion 71, the light that has passed through the placement reading contact glass 12 and has passed through the upper side is lower surface of the document conveying portion 2. The amount of light incident on the pixel that is reflected by the white mat 2d of 2e and reads the portion of the image sensor 68 where the document d is not present increases. Therefore, in the sensed read image data, the pixel value of the pixel that has read the portion without the document d is brighter when the wear is advanced than when the contact portion 71 is not worn (approaching white, low density Become).

  Here, conventionally, the threshold value t1 for determining the boundary position is fixed. Therefore, when the wear of the abutting portion 71 progresses, in the detected read image data, a region where the document d is present (a range where the placed document d is read) and a region where the document d is not present (the portion where the document d is not present) The boundary position of the reading range contact glass 12) may not be accurately detected. As a result, the size of the document d placed on the placement reading contact glass 12 may not be detected accurately.

  Therefore, the image reading apparatus 100 according to the present embodiment corrects the threshold value t1 for determining the boundary position in the document size detection.

(Flow of correction of threshold value t1)
Next, the flow of correction of the threshold value t1 according to the embodiment will be described with reference to FIGS. FIG. 10 is a flowchart showing a flow of correcting the threshold value t1 in the first method. FIG. 11 is a flowchart showing a flow of correcting the threshold value t1 in the second method. FIG. 12 is a flowchart showing a flow of correcting the threshold value t1 in the third method.

  In the image reading apparatus 100 of the present embodiment, a plurality of methods for correcting the threshold value t1 are prepared. Which method is used can be selected on the operation panel 3. In other words, the operation panel 3 functions as an input unit that receives selection of a correction method and timing of the threshold value t1. Then, the reading control unit 10 performs the correction of the threshold value t1 by the set method.

<First method>
First, in the image reading apparatus 100 of the present embodiment, when the document conveying unit 2 is opened and closed a predetermined number of times from the start of use, and when the document conveying unit 2 is opened and closed a predetermined number of times from the previous threshold t1 correction. Then, the threshold value t1 can be corrected. The correction of the threshold value t1 for each predetermined number of times of the document conveying unit 2 will be described below as a first method.

  Here, the “predetermined number of times” can be arbitrarily determined. It may be set to several tens of times or may be set to several thousand times. The image reading apparatus 100 according to the present embodiment assumes 1000 times for accurate detection of the size of the original d in the main scanning direction while avoiding frequent threshold t1 correction. Note that a predetermined number of times may be set on the operation panel 3. The reading control unit 10 corrects the threshold value t1 every time the reading control unit 10 is opened and closed a set number of times.

  First, the start of FIG. 10 is when the main power supply of the image reading apparatus 100 or the multifunction peripheral 200 is turned on. Then, the reading control unit 10 confirms whether or not the document conveying unit 2 is opened / closed based on the output of the opening / closing detection unit 7 (step # 11). Then, the reading control unit 10 continues to confirm opening / closing (No in step # 11 → step # 11).

  When the document conveying unit 2 is opened / closed (Yes in Step # 11), the reading control unit 10 adds the number of times of opening / closing to the count value of the number of times of opening / closing the document conveying unit 2 (Step # 12). The count value is the number of times the document conveying unit 2 is opened and closed since the use of the image reading apparatus 100 is started, and the total number of times (the integrated value) of the number of times the document conveying unit 2 is opened and closed after the threshold value t1 is corrected first. is there. The open / close count data D1 indicating the count value is stored in the memory 102 (see FIG. 7). The reading control unit 10 causes the memory 102 to update the open / close count data D1 so as to add 1 each time the document conveying unit 2 is opened / closed (step # 12).

  Subsequently, the reading control unit 10 checks whether or not the count value has reached a predetermined number of times (step # 13). In other words, the reading control unit 10 confirms the opening / closing frequency data D1 and opens / closes the document conveying unit 2 for the first time, or corrects the threshold value t1 first, and then conveys the document a predetermined number of times. It is confirmed whether or not the unit 2 has been opened and closed, and it is confirmed whether or not it is time to correct the threshold t1.

  If so (Yes in step # 13), the reading control unit 10 refers to the threshold value correction data D2 stored in the memory 102, corrects the threshold value t1, and stores the corrected threshold value t1 in the memory 102. (Step # 14). Further, the reading control unit 10 causes the memory 102 to reset the value (count value) of the open / close count data D1 to zero (step # 15).

  Specifically, the threshold correction data D2 may be data in which a plurality of threshold values t1 corresponding to the number of times of opening and closing the document conveying unit 2 are defined (for example, a lookup table). When the count value reaches a predetermined number of times, the reading control unit 10 reads the threshold value t1 corresponding to the number of times of opening and closing the document conveying unit 2 from the threshold value correction data D2, and wears the threshold value t1 on the wear of the contact portion 71. Correct the value according to. In other words, the reading control unit 10 selects a predetermined threshold value t1 for the number of times of opening and closing the document conveying unit 2 from the threshold value correction data D2, and selects the threshold value t1 used so far. By changing to t1, the threshold value t1 is corrected to a value in accordance with the wear of the contact portion 71. Alternatively, the threshold correction data D <b> 2 may be a function for obtaining the threshold t <b> 1 based on the number of times the document conveying unit 2 is opened and closed. In this case, the reading control unit 10 obtains the corrected threshold value t1 based on a function defined in the threshold value correction data D2 with the number of times of opening / closing the document conveying unit 2 as a variable.

  The reading control unit 10 confirms the threshold correction data D2, confirms how many times the threshold t1 before correction (before update) is the threshold t1 when the document conveying unit 2 is opened and closed, and adds the count value. Thus, it is possible to recognize the current number of opening and closing of the document conveying unit 2. Further, the reading control unit 10 may store the cumulative number of opening / closing of the document conveying unit 2 from the beginning to the present in the memory 102 without resetting the opening / closing number data D1.

  As the number of times of opening and closing the document conveying unit 2 increases and the wear of the contact portion 71 progresses, the pixel value of the pixel obtained by reading the portion without the document d is a white (brighter) pixel value than when there is no wear. Become. Therefore, the reading control unit 10 corrects the threshold value t1 to a white (bright) direction value as the number of times of opening and closing increases. After the correction, the reading control unit 10 determines that there is a boundary position at a pixel position having a brighter pixel value than before.

  Then, when the count value has not reached the predetermined number of times (No in Step # 13), and after Step # 15, every time the document conveying unit 2 is closed, the reading control unit 10 The reading mechanism 6 performs reading for detecting the size of the document d placed on the reading contact glass 12 in the main scanning direction, and performs document size detection processing based on the detected read image data (step # 16). When the threshold value t1 is corrected, the reading control unit 10 detects the boundary position based on the corrected threshold value t1, and detects the size of the document d in the main scanning direction. Then, the flow returns to step # 11.

<Second method>
Next, in the image reading apparatus 100 of the present embodiment, the pixel value of the pixel at the position where the document d is not placed is compared with the reference data, and the threshold value t1 is automatically corrected. Can do. Further, since the threshold value t1 is corrected as compared with the reference, the threshold value t1 can be corrected in accordance with the actual degree of wear of the contact portion 71 and the degree of change in the detected read data due to wear. This automatic threshold t1 correction will be described below as a second method with reference to FIG.

  First, the start of FIG. 11 is when the main power supply of the image reading apparatus 100 or the multifunction peripheral 200 is turned on. Then, the reading control unit 10 confirms whether or not the document conveying unit 2 is opened / closed based on the output of the opening / closing detection unit 7 (step # 21). The reading control unit 10 continues to confirm opening / closing (No in step # 21 → step # 21).

  When the document conveying unit 2 is opened and closed (Yes in step # 21), the reading control unit 10 reads the main document d placed on the placement reading contact glass 12 every time the document conveying unit 2 is closed. The reading mechanism 6 performs reading for detecting the size in the scanning direction, and performs document size detection processing based on image data (detected read image data) obtained by the reading (step # 22).

  Then, the reading control unit 10 confirms that there is no document d on the placement reading contact glass 12 (step # 23). Specifically, the reading control unit 10 in the detected read image data obtained by reading the document size detection, the pixel values of all the pixels in one line in the main scanning direction are black (darker) than the threshold value t1. If so, it is determined that there is no document d. When the document d is not present, the light is reflected by the white mat 2d, and the distance between the white mat 2d and the placement reading contact glass 12 differs depending on the position in the main scanning direction. For this reason, in the detected read image data when there is no document d, shading occurs. The threshold value t1 is set to a value brighter than the pixel value of the brightest pixel when there is no document d.

  If there is no document d (Yes in step # 23), the reading control unit 10 detects the read image data when there is no document d (the image of the line obtained by reading the document size detection when there is no document d). Data) and the reference image data D3 which is the image data of the line as the reference of the detected read image data (step # 24). Then, the reading control unit 10 obtains a deviation amount between the reference image data D3 and the detected read image data (step # 25).

  First, the reference image data D3 is stored in the memory 102. The reference image data D3 is detected read image data obtained by size detection reading when the contact portion 71 is not worn and the document d is not placed. For example, the reference image data D3 is a detected read image obtained by reading the placement reading contact glass 12 when the document conveying unit 2 is opened and closed in a state where there is no document d in a pre-shipment inspection after manufacture. It can be data. The reference image data D3 may be detected read image data of a line obtained by reading for document size detection when the document transport unit 2 is opened and closed for the first time when the document d is not placed. Alternatively, the reference image data D3 may be image data of a line having a predetermined value based on an experimental result. In other words, the detected read image data when the contact portion 71 is not substantially worn (opening and closing is less than a predetermined number of times) and the document d is not placed on the placement reading contact glass 12 is the reference image data. It is stored in the memory 102 as D3.

  The method for obtaining the amount of deviation can be determined as appropriate. For example, the reading control unit 10 corresponds to the pixel value of one pixel at a specific position (for example, both ends or the center in the main scanning direction) included in the detected read image data and the specific position in the reference image data D3. The absolute value of the difference from the pixel value of the pixel at the position is obtained as the shift amount.

  Alternatively, the reading control unit 10 calculates the average value of the pixel values of a plurality of pixels (for example, all pixels or one pixel skip) in the detected read image data and the pixel values of the plurality of pixels at the corresponding positions in the reference image data D3. The absolute value of the difference from the average value is obtained as the deviation amount.

  Note that the method of obtaining the deviation amount is not limited to the above example, and may be obtained by other methods.

  Then, the reading control unit 10 checks whether or not the obtained deviation amount exceeds a predetermined allowable range (step # 26). In other words, the reading control unit 10 confirms whether or not the reading timing of the document size detection is delayed due to wear of the contact portion 71 and the threshold t1 needs to be corrected.

  If the deviation amount exceeds the allowable range (Yes in step # 26), the reading control unit 10 corrects the threshold value t1, and stores the corrected threshold value t1 in the memory 102 (step # 27). Thus, thereafter, the boundary position is detected based on the corrected threshold value t1, and the size of the document d in the main scanning direction is detected.

  Specifically, the reading control unit 10 corrects the threshold value t1 so as to be the threshold value t1 corresponding to the deviation amount. For example, the reading control unit 10 changes the threshold value t1 as the pixel value by the shift amount in the bright direction. As a result, in the detected read image data, the reading control unit 10 determines that there is a boundary position at a pixel value having a brighter pixel value than before, and eliminates the influence due to wear of the contact portion 71. Therefore, it is possible to accurately detect the document size in the boundary position and the main scanning direction.

  It should be noted that instead of the correction for changing the threshold value t1 by the same value as the deviation amount, the obtained deviation amount and the correction amount for the threshold value t1 may be different.

  Then, after step # 27, when the document d is present when the document conveying section 2 is opened and closed (No in step # 23), when the deviation amount is within the allowable range (No in step # 26), the flow is step. Return to # 21.

<Third method>
Next, in the third method, the image reading apparatus 100 of the present embodiment automatically corrects the threshold value t1 as in the second method. However, in the third method, the threshold t1 is corrected after the document conveying unit 2 is opened and closed a predetermined number of times. In other words, the first and second methods are combined. Thereby, the frequency with which the threshold value t1 is corrected is reduced, and correction is performed only when necessary.

  Therefore, the flow of correction of the threshold value t1 in the third method will be described below with reference to FIG. First, the start of FIG. 12 is when the main power of the image reading apparatus 100 or the multifunction device 200 is turned on. Then, the reading control unit 10 confirms whether or not the document conveying unit 2 is opened / closed based on the output of the opening / closing detection unit 7 (step # 31). The reading control unit 10 continues to confirm opening / closing (No in step # 31 → step # 31).

  When the document conveying unit 2 is opened and closed (Yes in Step # 31), the reading control unit 10 adds the number of times of opening and closing to the count value of the number of times of opening and closing the document conveying unit 2 (Step # 32). The open / close count data D1 indicating the count value is the same as in the first method in that it is stored in the memory 102 (see FIG. 7). In other words, the reading control unit 10 adds 1 each time the document conveying unit 2 is opened / closed, and causes the memory 102 to update the opening / closing frequency data D1 (step # 32).

  Subsequently, the reading control unit 10 checks whether or not the count value has reached a predetermined number of times (step # 33). If the count value has not reached the predetermined number of times (No in step # 33), reading for size detection is performed by the reading mechanism 6, and image data (detected read image data) obtained by reading is read. Based on the document size detection process, step # 34 is performed. Then, the flow returns to step # 31.

  On the other hand, if the count value has reached the predetermined number of times (Yes in step # 33), the reading control unit 10 confirms whether or not the document conveying unit 2 has been opened / closed based on the output of the open / close detection unit 7. (Step # 35). The reading control unit 10 continues to confirm opening / closing (No in step # 35 → step # 35).

  When the document conveying unit 2 is opened and closed (Yes in step # 35), the reading control unit 10 reads the main document d placed on the placement reading contact glass 12 every time the document conveying unit 2 is closed. Reading for size detection in the scanning direction is performed by the reading mechanism 6, and document size detection processing based on image data (detected read image data) obtained by reading is performed (step # 36).

  Based on the result of the document size detection process, the reading control unit 10 confirms that there is no document d on the placement reading contact glass 12 (step # 37). If there is no document d (Yes in step # 37), the reading control unit 10 compares the detected read image data when there is no document d with the reference image data D3 (step # 38). Then, the reading control unit 10 obtains a deviation amount between the reference image data D3 and the detected read image data (step # 39). Then, the reading control unit 10 checks whether or not the obtained deviation amount exceeds a predetermined allowable range (step # 310). If the deviation amount exceeds the allowable range (Yes in step # 310), the reading control unit 10 corrects the threshold value t1, and stores the corrected threshold value t1 in the memory 102 (step # 311). Steps # 37 to # 311 are the same as in the second method described above, and the description can be applied mutatis mutandis.

  If there is a document d when the document transport unit 2 is opened and closed (No in step # 37), the flow returns to step # 35.

  After step # 311, and when the deviation t is within the allowable range and the threshold value t1 is not corrected (No in step # 310), the reading control unit 10 sets the value of the open / close count data D1 (count value) to zero in the memory 102. (Step # 312). Then, the flow returns to step # 31.

  Note that the threshold t1 is not completely corrected automatically by the second method after the document conveying unit 2 is opened and closed a predetermined number of times, but the threshold t1 is not corrected automatically. The threshold value t1 may be corrected semi-automatically using a reference document of a size. In this case, when the count value reaches a predetermined number of times, the reading control unit 10 opens the document conveying unit 2 and places the reference document on the display unit of the operation panel 3 on the reference reading glass 12. Display the power.

  When the document transport unit 2 is closed, the reading control unit 10 causes the reading mechanism 6 to perform size detection reading of the reference document placed on the placement reading contact glass 12. Then, the reading control unit 10 compares each pixel of the detected read image data when the reference document is placed with the reference image data D3.

  In this case, the reference image data D3 was obtained by size detection reading when the reference document having a predetermined reference size was placed on the placement reading contact glass 12 without wear of the contact portion 71. This is detected read image data. The reference image data D3 is stored in the placement reading contact glass 12 when the document conveying section 2 is opened and closed with the reference document placed on the placement reading contact glass 12 in the pre-shipment inspection after the manufacture. Can be detected read image data obtained by reading. Further, the reference image data D3 is detected when the reference document is placed when the document transport unit 2 is opened and closed for the first time when the document d is not placed, and the line obtained by reading for document size detection is detected. It may be read image data. Alternatively, the reference image data D3 may be image data of a line having a predetermined value based on an experimental result. In other words, the detected read image data in a state in which the contact portion 71 is hardly worn (opening and closing is less than a predetermined number of times) and the reference document is placed on the placement reading contact glass 12 is the reference image data D3. Is stored in the memory 102.

  Then, the reading control unit 10 obtains a deviation amount between the reference image data D3 and the detected read image data. The method for obtaining the amount of deviation can be determined as appropriate. For example, the reading control unit 10 corresponds to the pixel value of one pixel at a specific position (for example, both ends or the center in the main scanning direction) included in the detected read image data and the specific position in the reference image data D3. The absolute value of the difference from the pixel value of the pixel at the position is obtained as the shift amount. Alternatively, the reading control unit 10 may determine an average value of pixel values that should not have a document among a plurality of pixels (for example, all pixels or one pixel skip) in the detected read image data, and a corresponding position in the reference image data D3. The absolute value of the difference from the average value of the pixel values of the plurality of pixels is obtained as a deviation amount.

  The reading control unit 10 confirms whether or not the obtained deviation amount exceeds a predetermined allowable range. If the deviation amount exceeds the allowable range, the reading control unit 10 sets the threshold value by the deviation amount. The threshold value t1 is corrected by changing t1 in the bright direction, and the corrected threshold value t1 is stored in the memory 102).

  As described above, the image reading apparatus 100 according to the present embodiment includes the contact glass (the placement reading contact glass 12) on which the document d is placed, and the document d that is opened and closed in the vertical direction and placed on the contact glass. A contact portion 71 that is in contact with the cover portion (document feeding portion 2) for pressing the cover portion and is pushed into the cover portion as the cover portion is closed, depending on the pushing amount of the contact portion 71 An open / close detection unit 7 whose output changes, a lamp 67 for reading the document d and irradiating light toward the document d, and an image sensor 68 for reading line by line based on the reflected light reflected by the document d. When the contact portion 71 is pushed down to a predetermined position, a reading mechanism 6 (first transfer) that performs size detection reading for reading the contact glass in order to detect the document size in the main scanning direction. A frame 61, a second moving frame 62, a wire, a winding drum 64, a winding motor 65, a lens 66, and a lamp 67 (image sensor 68), and an image reading unit that generates image data based on the output of the image sensor, and a size The pixel value of each pixel of the detected read image data, which is image data obtained by the detection reading, is compared with the threshold value t1 for detecting the boundary position between the portion where the document d is present and the portion where the document d is not present. A detection processing unit (reading control unit 10) that detects a boundary position between the portion and a portion where the document d is not present, and performs a document size detection process for detecting the size of the document d placed on the contact glass based on the boundary position; In addition, the detection processing unit corrects the threshold value t1 at a predetermined time, and performs document size detection processing based on the corrected threshold value t1.

  As a result, the threshold t1 for determining the boundary position and detecting the document size is not a fixed value. Since the threshold value t1 is corrected at a fixed time, the threshold value t1 can be set according to the wear of the contact portion 71 due to the repeated opening and closing of the cover portion (document conveying portion 2). Therefore, even when the cover size (document conveying section 2) comes closer to the contact glass (the placement reading contact glass 12) than when there is no wear, the document size detection is performed (as compared with when there is no wear). Even if the execution start of the document size detection is delayed), the boundary between the pixels in the range where the document d is present and the pixels in the range where the document d is not present is accurately determined in the detected read image data by the corrected threshold value t1. Can do. Even if the wear of the contact portion 71 advances, the size of the document d in the main scanning direction can be accurately detected.

  In addition, the image reading apparatus 100 according to the present embodiment stores the number of times the cover unit (document conveying unit 2) is opened and closed and threshold correction data D2 for determining the threshold value t1 according to the number of times the cover unit is opened and closed. 102, the detection processing unit (reading control unit 10) corrects the threshold value t1 based on the threshold value correction data D2 when the cover unit is opened and closed a predetermined number of times. As a result, when the cover unit is opened and closed a predetermined number of times for the first time or enough to correct the threshold value t1 again, the threshold value t1 is corrected only by data calculation. Accordingly, the threshold value t1 can be set to a value corresponding to the wear of the contact portion 71 (a value corresponding to the number of times the cover portion is opened and closed) so that the size of the document d in the main scanning direction can be accurately detected.

  The “predetermined number of times” can be appropriately determined in consideration of the material of the contact portion 71 and the ease of wear in the actual image reading apparatus 100. The predetermined number of times can be determined in the range of several hundred to several thousand times, and may be determined for each type and specification of the image reading apparatus 100.

  The image reading apparatus 100 according to the present embodiment includes a memory 102 that stores reference image data D3 as a reference of detected read image data when a document is not placed, and includes a detection processing unit (reading control unit 10). Compares the pixel value of the pixel in the detected read image data at the position where the document d is not placed with the pixel value of the pixel at the corresponding position in the reference image data D3, and compares the reference image data D3 with the detected read image. A deviation amount between data is obtained, and the threshold value t1 is corrected so as to be a threshold value t1 corresponding to the deviation amount.

  Although the wear of the abutting portion 71 is advanced by opening and closing the cover portion (document conveying portion 2), the degree of wear varies depending on the actual usage of the image reading apparatus 100. It can be considered that the wear of the abutting portion 71 progresses as the number of times that the cover portion (document conveying portion 2) is opened and closed vigorously increases. On the other hand, when the cover part (document conveying part 2) is opened and closed relatively quietly, it is considered that the wear of the contact part 71 progresses slowly. Therefore, according to this configuration, the detection processing unit (reading control unit 10) sets the pixel value of the pixel in the detected read image data at the position where the document d is not placed and the corresponding position in the reference image data D3. The pixel values of the pixels are compared to obtain a deviation amount between the reference image data D3 and the detected read image data, the threshold value t1 is corrected so as to be a threshold value t1 corresponding to the deviation amount, and based on the corrected threshold value t1, Document size detection processing is performed. As a result, the threshold value t1 can be corrected according to the actual degree of wear of the contact portion 71 (in accordance with the difference in pixel values in the detected read image data between the initial and present time when the contact is not worn). Accordingly, the threshold value t1 can be corrected so that accurate document size detection is performed in accordance with the actual degree of wear of the contact portion 71.

  When the cover unit (document conveying unit 2) is opened and closed a predetermined number of times, the detection processing unit (reading control unit 10) detects the position in the detected read image data where the document d is not placed. The pixel value of the pixel and the pixel value of the pixel at the corresponding position in the reference image data D3 are compared to obtain a deviation amount between the reference image data D3 and the detected read image data, and the threshold value t1 corresponding to the deviation amount is obtained. The threshold value t1 is corrected. As a result, the threshold value t1 is automatically corrected when it is considered that the threshold value t1 needs to be corrected in order to accurately detect the size of the document d due to wear of the contact portion 71. it can. Further, the processing load of the detection processing unit can be reduced by always correcting the threshold value t1 only at a fixed timing without correcting the threshold value t1.

  The detection processing unit (reading control unit 10) also detects the difference between the pixel value of the pixel included in the detected read image data and the pixel value of the pixel at the corresponding position in the reference image data D3, or the detected read image data. The average of the differences between the pixel values of the plurality of pixels in the pixel and the pixel values of the plurality of pixels at the corresponding positions in the reference image data D3 is obtained as a shift amount, and the threshold value t1 is changed by the shift amount. As a result, the threshold value t1 can be corrected based on a difference from a pixel value reference of a certain pixel or a difference from an average pixel value in data that is an average of pixel values of a plurality of pixels. Therefore, the threshold t1 can be corrected in consideration of the difference from the reference that actually appears in each pixel value of the detected read image data due to wear of the contact portion 71.

  The image forming apparatus (multifunction machine 200) includes the image reading apparatus 100 of the present embodiment. The image forming apparatus of the present embodiment includes an image reading apparatus 100 in which the size of the detected document d is accurate even when the cover unit (document transport unit 2) is repeatedly opened and closed. Accordingly, it is possible to provide an image forming apparatus capable of obtaining a job result as desired by a user without using an inappropriate job based on a detection result of an erroneous document size even after being used for many years. it can.

  Next, another embodiment will be described. The document transport unit 2 is exemplified as the cover unit for pressing the document d placed on the placement and reading contact glass 12. However, the cover unit may be a rectangular plate-shaped document cover having no document transport function.

  In the above-described embodiment, the MFP 200 is taken as an example of the image forming apparatus. However, the present invention can be applied to other image forming apparatuses including the image reading apparatus 100. For example, the present invention can be applied to a copying machine, a printer with a scanner, a facsimile machine, and the like.

  The embodiment of the present invention has been described above, but the scope of the present invention is not limited to this, and various modifications can be made without departing from the spirit of the invention.

  The present invention is applicable to an image reading apparatus that detects the size of a document in the main scanning direction by reading, and an image forming apparatus including the image reading apparatus.

DESCRIPTION OF SYMBOLS 100 Image reading apparatus 1 Image reading part 10 Reading control part (detection process part) 102 Memory 12 Placement reading contact glass (contact glass)
2 Document transport unit (cover unit) 6 Reading mechanism 61 First moving frame (reading mechanism 6) 62 Second moving frame (reading mechanism 6)
63 Wire (reading mechanism 6) 64 Winding drum (reading mechanism 6)
65 Winding motor (reading mechanism 6) 66 Lens (reading mechanism 6)
67 Lamp (reading mechanism 6) 68 Image sensor (reading mechanism 6)
7 Open / Close Detection Unit 71 Contact Unit 200 Multifunction Device (Image Forming Apparatus) D1 Open / Close Count Data D2 Threshold Correction Data D3 Reference Image Data d Original Document t1 Threshold Value

Claims (4)

A contact glass on which the document is placed;
A cover part that is opened and closed in a vertical direction and holds down a document placed on the contact glass;
An opening / closing detection unit that includes a contact part that is in contact with the cover part in the middle of being closed and is pushed into the cover part as the cover part is closed; and an output that varies depending on a pressing amount of the contact part;
When the original is read, it includes a lamp that irradiates light toward the original and an image sensor that reads line by line based on the reflected light reflected by the original, and the main scanning is performed when the contact portion is pushed to a predetermined position. An image reading unit that includes a reading mechanism that performs size detection reading for reading the contact glass for detecting a document size in a direction, and generates image data based on an output of an image sensor;
By comparing the pixel value of each pixel of the detected read image data, which is the image data obtained by the size detection reading, with the threshold value for detecting the boundary position between the portion where the document is present and the portion where the document is not present, A detection processing unit for detecting a boundary position between a certain part and a part without a document, and performing a document size detection process for detecting a size of the document placed on the contact glass based on the boundary position;
Including memory to store data,
In the first case where the cover part is opened and closed a predetermined number of times from the start of use or from the previous correction of the threshold value,
A comparison is made based on the pixel value of the detected read image data at a position where no document is placed and the pixel value of the corresponding position in the reference image data as a reference of the detected read image data stored in the memory. In a second case where the amount of deviation between the determined reference image data and the detected read image data exceeds a predetermined allowable range,
Alternatively, the pixel value of the detected read image data and the reference at a position where the document is not placed after the cover portion is opened and closed a predetermined number of times from the start of use or from the correction of the threshold value. In a third case where the amount of deviation between the reference image data and the detected read image data obtained by performing the comparison based on the pixel values at corresponding positions in the image data exceeds a predetermined allowable range,
The image reading apparatus, wherein the detection processing unit corrects the threshold value by changing the threshold value in a bright direction, and performs the document size detection process based on the corrected threshold value. The memory stores threshold correction data for determining the threshold according to the number of times the cover is opened and closed and the number of times the cover is opened and closed .
The image reading apparatus according to claim 1, wherein the detection processing unit corrects the threshold value by changing the threshold value in a bright direction based on the threshold value correction data in the first case . The detection processing unit, in the second case and the third case, a difference between a pixel value of a pixel included in the detected read image data and a pixel value of a pixel at a corresponding position in the reference image data, Alternatively, an average of the difference between the pixel values of a plurality of pixels at corresponding positions of the pixel values in the reference image data of a plurality of pixels of the detection read in the image data as the shift amount, the shift amount by the threshold brightly the image reading apparatus according to claim 1, characterized in that changing the threshold value in a direction in which. An image reading apparatus according to any one of claims 1 to 3, an image forming apparatus which comprises an image forming unit for forming an image.

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