JP6256043B2 - Image reading apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to an image reading apparatus and an image forming apparatus.

  As a technique related to the image reading apparatus, for example, the technique disclosed in Patent Document 1 has already been proposed. Patent Document 1 includes a first skew correction unit that mechanically corrects the skew feeding state of the document, and a second skew correction unit that electrically corrects the skew feeding state of the document. A configuration is disclosed in which after the first skew correction by the first skew correction means, the second skew correction processing by the second skew correction means is started.

JP 2011-71763 A

  An object of the present invention is to improve the accuracy of document inclination correction by image processing.

  Another object of the present invention is to make it possible to correct the inclination of an original composed of a long sheet or a sheet having a mixed size, which has been difficult to be corrected by image processing.

The invention described in claim 1 is an image reading unit that reads an image of a conveyed document;
First correcting means for mechanically correcting the inclination of the document with respect to the transport direction;
Second correction means for correcting the inclination of the document by image processing;
An image reading apparatus comprising: a changing unit that changes a correction content of the second correction unit in accordance with the presence or absence of a correction operation by the first correction unit.

According to a second aspect of the present invention, the second correction unit includes a first unit and a second unit having a correction amount larger than the first unit as a correction unit amount when executing the correction operation.
2. The image reading apparatus according to claim 1, wherein the changing unit changes the first unit when the correction operation is performed by the first correcting unit and the second unit when the correcting operation is not performed. .

  According to a third aspect of the present invention, the changing means makes the presence / absence of correction when the second correction means executes the correction operation, when the correction operation by the first correction means is present, The image reading apparatus according to claim 1, wherein the image reading apparatus is changed to none when no.

  According to a fourth aspect of the present invention, when the original is a long original or a mixed-size original, the changing means has the second correcting means when the correcting action by the first correcting means is present. 2. The image reading apparatus according to claim 1, wherein the image reading apparatus is changed so that the correction operation is not executed when the correction operation by the first correction unit is absent.

  The invention described in claim 5 is characterized in that the changing means changes to the second unit when the original is a long original or a mixed-size original. It is a reading device.

  The invention described in claim 6 is characterized in that the changing means changes the correction unit amount when the original is a long original to a value larger than that when the original is mixed in size. 2. The image reading apparatus according to 2.

The invention described in claim 7 comprises a detecting means for detecting the size of the document,
7. The change unit according to claim 1, wherein the change unit changes the correction content of the second correction unit based on the presence / absence of a correction operation by the first correction unit and a detection result by the detection unit. An image reading apparatus according to any one of the above.

The invention described in claim 8 includes stop means for stopping the operation of the change means,
8. The image reading apparatus according to claim 1, wherein the stopping unit stops the operation of the changing unit when the user instructs to stop the changing unit.

The invention described in claim 9 includes an image reading device that reads an image of a document,
Image forming means for forming an image on a recording medium based on an image of a document read by the image reading device;
An image forming apparatus using the image reading apparatus according to claim 1 as the image reading apparatus.

  According to the first aspect of the present invention, document inclination correction by image processing is performed as compared with the case where the correction content of the second correction unit is not changed regardless of the presence or absence of the correction operation by the first correction unit. Accuracy can be improved.

  According to the second aspect of the present invention, document inclination correction by image processing is performed with a smaller correction unit amount compared to the case where the same correction amount is set regardless of the presence or absence of the correction operation by the first correction unit. Can be done with.

  According to the third aspect of the present invention, it is possible to suppress a possibility that the image is missing as compared with the case where the correction is performed regardless of the presence or absence of the correction operation by the first correction unit.

  According to the fourth aspect of the present invention, compared to the case where the present configuration is not provided, the inclination of the original made of the long paper or the mixed paper which has conventionally been difficult to be corrected by the image processing. Correction can be made possible.

  According to the invention described in claims 5, 6, and 7, an appropriate correction amount is set as compared with the case where the same correction amount is set for those which are expected to have different skew amounts. be able to.

  According to the eighth aspect of the present invention, it is possible to meet the needs of the user who does not desire to correct the inclination of the document by the first correction unit, as compared with the case where this configuration is not provided.

  According to the ninth aspect of the present invention, it is possible to suppress the image from being inclined as compared with the case where the present configuration is not provided.

1 is a schematic configuration diagram showing an image forming apparatus to which an image reading apparatus according to Embodiment 1 of the present invention is applied. 1 is a configuration diagram illustrating an image reading apparatus according to a first embodiment of the present invention. 1 is a cross-sectional configuration diagram illustrating a main part of an image reading apparatus according to Embodiment 1 of the present invention. It is a block diagram which shows a control part. It is a block diagram which shows an edge detection process part. It is a figure which shows the filter for edge detection. It is a block diagram which shows an angle calculation process part. FIG. 10 is an explanatory diagram illustrating an angle calculation process of a document image. It is explanatory drawing which shows the effect | action of an edge detection process part. It is explanatory drawing which shows the effect | action of an edge detection process part. It is a block diagram which shows an operation panel. It is a chart showing the upper limit value of the paper size and skew angle of the document.

  Embodiments of the present invention will be described below with reference to the drawings.

[Embodiment 1]
FIG. 1 shows an outline of the entire image forming apparatus to which the image reading apparatus according to the first embodiment is applied.

<Overall Configuration of Image Forming Apparatus>
The image forming apparatus 1 according to the first embodiment is configured as a color copying machine, for example. The image forming apparatus 1 includes an image reading device 3 that reads an image of a document 6 and an image forming unit 2 as an example of an image forming unit that forms an image on a recording medium based on image data. The image reading device 3 is disposed in a state of being supported by the support unit 4 above the device main body 1a that houses the image forming unit 2, and an image is formed between the image reading device 3 and the device main body 1a. A space for discharging the recorded recording medium is formed.

  In addition, the image reading apparatus 3 is provided with a control panel 101 as an operation unit for operating the image forming apparatus 1 and the image reading apparatus 2 on an upper portion of a front wall 311 positioned on the front surface of the casing 31. The control panel 101 also has a touch panel 102 that serves as a display unit that displays an operation menu, a warning, a message, and the like to the user, and receives various settings for the displayed operation menu, and a plurality of operation buttons 103. Note that the touch panel 102 of the control panel 101 has a function as a stopping unit as described later.

  The image forming unit 2 holds a plurality of image forming apparatuses 10 that form toner images developed with toner constituting the developer, and the toner images formed by the respective image forming apparatuses 10, and finally records media An intermediate transfer device 20 that transports to a secondary transfer position for secondary transfer to a recording paper 5 as an example, and a recording paper 5 as an example of a required recording medium to be supplied to the secondary transfer position of the intermediate transfer device 20 A sheet feeding device 50 accommodated and conveyed, and a fixing device 40 for fixing the toner image on the recording paper 5 secondarily transferred by the intermediate transfer device 20 are provided. The apparatus main body 1a is formed of a support structure member, an exterior cover, and the like.

  The image forming device 10 includes four image forming devices 10Y, 10M, 10C, and 10K that respectively form four color toner images exclusively for yellow (Y), magenta (M), cyan (C), and black (K). It is configured. The four image forming apparatuses 10 (Y, M, C, K) are arranged in a line in the internal space of the apparatus main body 1a.

  As shown in FIG. 1, each image forming device 10 (Y, M, C, K) includes a photosensitive drum 11 as an example of a rotating image holding member, and around the photosensitive drum 11. The following devices are mainly arranged. The main devices are a charging device 12 that charges a peripheral surface (image holding surface) on the photosensitive drum 11 on which an image can be formed to a required potential, and image information (on the charged peripheral surface of the photosensitive drum 11). The exposure device 13 as an electrostatic latent image forming unit that irradiates the light LB based on the signal) to form an electrostatic latent image (for each color) having a potential difference, and the corresponding electrostatic image (Y, A developing device 14 (Y, M, C, K) as developing means for developing a toner image by developing with toner of a developer of M, C, K), and a primary for transferring each toner image to the intermediate transfer device 20 These include a transfer device 15 and a drum cleaning device (not shown) that removes and removes adherents such as toner remaining on the image holding surface of the photosensitive drum 11 after the primary transfer.

  As shown in FIG. 1, the intermediate transfer device 20 is disposed so as to exist at a position above each image forming device 10 (Y, M, C, K). The intermediate transfer device 20 includes an intermediate transfer belt 21 that rotates in a direction indicated by an arrow while passing a primary transfer position between the photosensitive drum 11 and the primary transfer device 15 (primary transfer roll), and an intermediate transfer belt 21. A plurality of belt support rolls 22 to 24 that are supported in a desired state from the inner surface and are rotatably supported, and an outer peripheral surface (image holding surface) side of the intermediate transfer belt 21 supported by the belt support roll 23. A secondary transfer device 25 that secondary-transfers the toner image on the intermediate transfer belt 21 to the recording paper 5, and toner and paper that remain on the outer peripheral surface of the intermediate transfer belt 21 after passing through the secondary transfer device 25 and paper It mainly comprises a belt cleaning device 26 that removes and removes deposits such as powder.

  As shown in FIG. 1, the secondary transfer device 25 is configured to move the intermediate transfer belt 21 at the secondary transfer position, which is the outer peripheral surface portion of the intermediate transfer belt 21 supported by the belt support roll 23 in the intermediate transfer device 20. It is a contact type transfer device provided with a secondary transfer roll that rotates in contact with a peripheral surface and is supplied with a secondary transfer voltage. Further, a DC voltage having a polarity opposite or the same as the charging polarity of the toner is supplied as a secondary transfer voltage to the secondary transfer roll 25 or the support roll 23 of the intermediate transfer device 20.

  The fixing device 40 is in contact with a rotating rotator 41 in the form of a roll or belt heated by heating means so that the surface temperature is maintained at a predetermined temperature, and the rotating rotator 41 for heating at a required pressure. And a pressurizing rotator 42 in the form of a roll or a belt that rotates. In the fixing device 40, a contact portion where the heating rotator 41 and the pressing rotator 42 come into contact becomes a fixing processing unit that performs a required fixing process (heating and pressing).

The paper feeding device 50 is disposed so as to exist at a position below the exposure device 13. The paper feeding device 50 includes a plurality (or a single) of paper storage bodies 51 ₁ , 51 ₂ , 51 ₃ for storing recording paper 5 of a desired size, type, etc., and paper storage bodies 51 ₁ , 51. ₂ and 51 ₃ , and is mainly composed of delivery devices 52 and 53 that feed out the recording paper 5 one by one. The paper containers 51 ₁ , 51 ₂ , 51 ₃ are attached, for example, so that they can be pulled out to the front side (side surface on which the user faces during operation) of the apparatus main body 1a.

  Between the paper feeding device 50 and the secondary transfer device 20, the recording paper 5 delivered from the paper feeding device 50 is composed of a plurality of paper transporting rolls 54 and 55 and a transport guide material that transport the recording paper 5 to the secondary transfer position. A paper feed path 56 is provided. A paper transporting roll 55 disposed at a position immediately before the secondary transfer position in the paper feed transporting path 56 is configured as a roll (registration roll) that adjusts the transporting timing of the recording paper 5, for example. Further, on the downstream side of the fixing device 40 in the sheet conveyance direction, a discharge roll 58 that discharges the recording sheet 5 to the discharge container 57 is disposed.

<Basic operation of image forming apparatus>
Hereinafter, a basic image forming operation by the image forming apparatus 1 will be described.

  Image formation when a full-color image formed by combining four color (Y, M, C, K) toner images using the four image forming devices 10 (Y, M, C, K) The operation will be described.

  When the image forming apparatus 1 receives the command information of the request for the image forming operation (printing), the four image forming apparatuses 10 (Y, M, C, K), the intermediate transfer apparatus 20, the secondary transfer apparatus 25, and the fixing apparatus. 40 etc. starts.

  In each imaging device 10 (Y, M, C, K), first, each photosensitive drum 11 rotates in the direction indicated by the arrow, and each charging device 12 causes the surface of each photosensitive drum 11 to have a required polarity. (Embodiment 1 has negative polarity) and a potential. Subsequently, the exposure apparatus 13 converts the image information input to the image forming apparatus 1 into each color component (Y, M, C, K) with respect to the surface of the photosensitive drum 11 after charging. The light LB emitted based on this signal is irradiated, and an electrostatic latent image of each color component composed of a required potential difference is formed on the surface thereof.

  Subsequently, each developing device 14 (Y, M, C, K) has a corresponding color charged with a required polarity (minus polarity) with respect to the electrostatic latent image of each color component formed on the photosensitive drum 11. (Y, M, C, K) toners are respectively supplied and electrostatically adhered to perform development. By this development, the electrostatic latent images of the respective color components formed on the respective photosensitive drums 11 are visualized as toner images of four colors (Y, M, C, K) respectively developed with the corresponding color toners. It becomes.

  Subsequently, when each color toner image formed on the photosensitive drum 11 of each image forming device 10 (Y, M, C, K) is conveyed to the primary transfer position, the primary transfer device 15 causes each color image. The toner image is primarily transferred in a state where the toner image is sequentially superimposed on the intermediate transfer belt 21 rotating in the direction indicated by the arrow of the intermediate transfer device 20.

  Further, in each image forming device 10 after the primary transfer is completed, a drum cleaning device (not shown) removes adhering matter such as toner remaining on the surface of the photosensitive drum 11 so as to scrape off and cleans the surface of the photosensitive drum 11. To do. Thereby, each image forming apparatus 10 is brought into a state in which the next image forming operation can be performed.

  Subsequently, in the intermediate transfer device 20, the toner image primarily transferred by the rotation of the intermediate transfer belt 21 is held and conveyed to the secondary transfer position. On the other hand, the paper feeding device 50 sends out the required recording paper 5 to the paper feeding conveyance path 56 in accordance with the image forming operation. In the paper feed conveyance path 56, a paper conveyance roll 55 as a registration roll feeds and supplies the recording paper 5 to the secondary transfer position in accordance with the transfer timing.

  At the secondary transfer position, the secondary transfer device 25 performs secondary transfer of the toner images on the intermediate transfer belt 21 onto the recording paper 5 collectively. Further, in the intermediate transfer device 20 after the secondary transfer is completed, the belt cleaning device 26 removes the adhering matter such as toner remaining on the surface of the intermediate transfer belt 21 after the secondary transfer, and cleans it.

  Subsequently, the recording sheet 5 on which the toner image is secondarily transferred is peeled off from the intermediate transfer belt 21 and the secondary transfer roll 25 and then conveyed to the fixing device 40. In the fixing device 40, a necessary fixing process (heating and pressing) is performed to fix the unfixed toner image on the paper 5. Finally, the recording paper 5 after the fixing is finished is discharged by a discharge roll 58 to, for example, a discharge storage portion 57 disposed inside the apparatus main body 1a.

  Through the above operation, the recording paper 5 on which a full color image formed by combining four color toner images is output.

<Configuration of image reading apparatus>
FIG. 2 is a schematic configuration diagram showing the configuration of the image reading apparatus according to the first embodiment.

  The image reading apparatus 3 is roughly divided into a casing 31 having a document reading surface formed on the upper end surface, a document pressing cover 32 attached to the casing 31 so as to be freely opened and closed, and one end of the document pressing cover 32. And an automatic document feeder 33 provided.

  The image reading apparatus 3 is placed on a first reading mode for reading the document 6 while automatically conveying the document 6 by the automatic document conveying unit 33 according to a user operation, and on a document table 76 described later. The second reading mode for reading the original 6 can be switched to. FIG. 2 shows the state of each member during document reading in the first reading mode.

  The automatic document feeder 33 is arranged to feed the document 6 one by one, a document storage unit 60 that places the document 6 in a stacked state, a delivery roll 61 that sends out the document 6 from the document storage unit 60, and a document 6 sent out by the delivery roll 61. The document feeding mechanism includes a separating roll 62, conveyance rolls 63 to 67 that convey the document 6 to a document reading position, and a discharge roll 69 that discharges the document 6 to a discharge container 68. The delivery roll 61, the separating roll 62, the transporting rolls 63 to 67, and the discharge roll 69 are driven by a driving unit (not shown) when the document 6 is read. The transport roll 65 functions as a registration roll, and the transport roll 64 located on the upstream side in the transport direction of the transport roll 65 functions as a pre-registration roll. The transport roll 67 is a roll for pressing the upper surface of the document 6.

  The conveyance roll 63 and the conveyance roll 64 arranged along the conveyance direction of the document 6 function as a first correction unit that mechanically corrects the inclination of the document 6 with respect to the conveyance direction. Of the transport rolls 63 positioned on the upstream side in the transport direction of the document 6, the transport roll 63b serving as a drive roll has a drive motor or the like (not shown) as drive means as shown in FIG. It is configured to be rotatable in the reverse rotation direction Rb with Ra. The transport roll 63a which is a driven roll rotates in accordance with the rotation of the transport roll 63b while being in pressure contact with the transport roll 63b. At that time, the rotation direction of the conveyance roll 63b is opposite to the rotation direction of the conveyance roll 63a.

  Similarly, the transport roll 64b serving as a drive roll among the transport rolls 64 positioned on the downstream side in the transport direction of the document 6 is driven in the direction opposite to the normal rotation direction Ra in the drawing using a drive motor (not shown) as a drive means. Rb is configured to be rotatable. The transport roll 64a, which is a driven roll, rotates in accordance with the rotation of the transport roll 64b while being in pressure contact with the transport roll 64b. At that time, the rotation direction of the conveyance roll 64b is opposite to the rotation direction of the conveyance roll 64a.

  The transport roll 63 is bent by abutting the leading end of the document 6 against a stopped transport roll 64 positioned on the downstream side, and the transported document 6 is corrected for inclination with respect to the transport direction (hereinafter referred to as “skew correction”). The first tilt correction means is configured by the machine that performs. Similarly, the transport roll 64 is bent by abutting the leading end of the document 6 against a stopped transport roll 65 located downstream, and performs skew correction on the transported document 6 in the transport direction. The 1st inclination correction means by these is comprised. However, the transport rolls 63 and 64 are controlled by the control unit 200 described later, and execute the tilt correction by the machine only when necessary. Therefore, the transport rolls 63 and 64 are normally driven to rotate in the normal rotation direction Ra. The transport rollers 63 and 64 do not necessarily need to correct the skew of the document 6 in two stages using both the transport rollers 63 and 64, and only one of the transport rollers 63 or the transport roller 64 is used for the document 6. You may comprise so that skew correction may be performed.

  The automatic document feeder 33 is provided on the reading guide 70 above the reading window 70 and the curved reading guide 70 that guides the document 6 to the reading position and guides the document 6 from the reading position in the discharge direction. A plate-shaped regular reflection plate 72 serving as a backing, a first sensor 73 as an example of a detection unit that detects the size of the document 6 in the sub-scanning direction, and an example of a detection unit that detects the size of the document 6 in the main scanning direction. A second sensor 74, and a back side reading unit 75 for reading an image on the back side of the document 6 as necessary.

  The regular reflection plate 72 reflects light emitted from an illumination lamp 78 (described later) with a reflectance such that the upper limit value (white upper limit value) of the light intensity detectable by the image reading element 83 is reached. As the regular reflection plate 72, for example, a mirror-finished metal plate, a silver or aluminum-deposited film plate, or a sheet made of a metal such as aluminum can be used.

  The housing 31 of the image reading device 3 is formed as a rectangular parallelepiped box with a part of the upper end surface opened. The housing 31 includes an upper wall 312 that faces the document pressing cover 32, a bottom wall 313 that faces the upper wall 312, a side wall 314 that faces the sub-scanning direction (left and right direction in FIG. 2) across the bottom wall 313, and It has a side wall 315, the above-described front wall 311 (see FIG. 1), and a front wall 311 and a rear wall 316 facing the main scanning direction (a direction perpendicular to the paper surface of FIG. 2).

  An opening 317 is formed in the upper wall 312 of the housing 31 at a portion corresponding to the document reading position of the document 6 read in the second reading mode. The document table 76 that supports the document 6 is formed in the opening 317. (Platen glass) is arranged. Further, a reading window 71 for reading the document 6 in the first reading mode is provided on the side of the automatic document feeder of the document table 76. A guide member 77 for guiding the document 6 in the first reading mode is provided between the reading window 71 and the document table 76.

  The image reading device 3 has a cylindrical illumination lamp 78 that emits light for illuminating the document 6 inside the housing 31, and a part of the light emitted from the illumination lamp 78 is directed toward the document 6. From the reflector 79, the first mirror 80 that receives the reflected light of the document 6, the second mirror 81 that receives the reflected light from the first mirror 80, and the second mirror 81. A third mirror 82 that receives the reflected light, and an image reading unit having a lens 84 that forms an image on the image reading element 83 made of a CCD or the like from the reflected light from the third mirror 83 are provided. The illumination lamp 78, the reflector 79, and the first to third mirrors 80 to 82 are arranged along the sub-scanning direction (direction perpendicular to the paper surface of FIG. 2). The illumination lamp 78 emits light toward the specular reflection plate 72 and the reflector 79.

  The illumination lamp 78, the reflector 79, and the first mirror 80 are disposed along the main scanning direction, and are fixed to a first moving body 85 including a carriage provided so as to be movable along the sub scanning direction. The first moving body 85 is guided by a first rail 86 arranged along the sub-scanning direction on the rear wall 316 of the casing 31 and illuminates the reading target area of the document 6 while moving in the sub-scanning direction. Then, the reflected light of the original 6 is reflected by the first mirror 80 toward the second mirror 81 of the second moving body 87.

  The second mirror 81 and the third mirror 82 are arranged along the main scanning direction, and are fixed to a second moving body 87 including a carriage provided so as to be movable along the sub scanning direction. . The second moving body 87 is guided by a second rail 88 disposed on the bottom wall 313 of the housing 31 along the sub-scanning direction, and moves the reflected light of the document 6 to the image while moving in the sub-scanning direction. Reflected toward the lens 84 of the reading unit. The first rail 86 and the second rail 88 are arranged one by one so as to face both ends along the main scanning direction.

  The image reading unit has a substrate 90 mounted with a lens 84 and an image reading element 83 fixed to a base plate 89 supported by the bottom wall 313. In the image reading unit, the reflected light from the third mirror 82 passes through the lens 84 and forms an image on the image reading element 83 such as a CCD. The image reading element 83 reads the image of the document 6 and outputs the image data. Is configured to do.

  In the second reading mode, the first moving body 85 and the second moving body 87 are driven by a drive mechanism (not shown), and the image reading portion of the document 6 is moved while the first moving body 85 moves in the sub-scanning direction. The moving amount of the second moving body 87 is half of the moving amount of the first moving body 85 so that the optical path length from to the image reading element 83 described later does not fluctuate. In FIG. 2, the two-dot chain line indicates the positions of the first moving body 85 and the second moving body 87 when the first moving body 85 moves to the vicinity of the end of the document 6 in the sub-scanning direction. .

  FIG. 3 is an enlarged configuration diagram showing the periphery of the document reading position. In this figure, the optical path until the light emitted from the illumination lamp 78 irradiates the document 6 is indicated by a two-dot chain line. In addition, reading guides 70 a, 70 b, and 70 c are arranged on the outer peripheral side of the reading guide 70, and guide the document 6 conveyed by the conveying rolls 65 and 66 together with the reading guide 70.

  The illumination lamp 78 is a light guide (not shown) so that a part of the light emitted from the illumination lamp 78 is directly emitted toward the document reading position and the other part is emitted toward the reflector 79. The angle and position of the diffusion plate are adjusted and provided.

  The reflector 79 is provided with an angle and a position adjusted so that a part of the light emitted from the illumination lamp 78 is reflected in the direction of the document reading position.

  The first mirror 80, the second mirror 81, and the third mirror 82 are configured such that the light reflected by the document 6 reaches the image reading unit when the document 6 exists at the document reading position. Are adjusted and provided.

  Further, the regular reflection plate 72 is angled so that light irradiated directly from the illumination lamp 78 toward the document reading position is reflected in the direction of the first mirror 80 when the document 6 does not exist at the document reading position. And the position and the like are adjusted.

  In this embodiment, an aluminum sheet is used as the specular reflection plate 72, and the specular reflection surface is configured by sticking the aluminum sheet 72 to an attachment position of the specular reflection plate. Also, wax is applied to the surfaces of the specular reflection plate 72 and the reading guide 70 as necessary to prevent foreign matters such as paper dust, dust, and dust from adhering. Foreign matter such as paper dust tends to be generated at the contact portion where the document 6 contacts the corner of the reading guide 70 when the document 6 travels while being guided by the reading guide 70. Therefore, compared with the case where the wax is applied only to the specular reflection plate 72, the case where the wax is also applied to the reading guide 70 is more effective in suppressing the generation of paper dust.

<Configuration of control unit>
FIG. 4 is a block diagram illustrating a control unit of the image reading apparatus 3.

  The control unit 200 includes a CPU, a storage element that stores programs executed by the CPU, parameters, and the like, and is provided inside the housing 31. A control panel 101 as an example of an operation unit having a touch panel 102 and operation buttons 103 is connected to the control unit 200. The control unit 200 also includes a line buffer 201, a skew correction processing unit 202 as an example of a second correction unit, an image processing unit 203, an image forming unit 2, a reduction processing unit 204, an edge detection unit 205, and an angle calculation processing unit. Each part such as 206 is controlled. Instead of the image forming unit 2, a network that outputs image data, an HDD that stores image data, or the like may be employed.

  Further, the control unit 200 implements functions as these units in addition to controlling the respective units such as the skew correction processing unit 202, the image processing unit 203, the reduction processing unit 204, the edge detection unit 205, and the angle calculation processing unit 206. It may be a thing. That is, the control unit 200 operates as a skew correction processing unit 202, an image processing unit 203, a reduction processing unit 204, an edge detection unit 205, and an angle calculation processing unit 206 based on a program stored in advance in a storage unit (not shown). May be configured to execute.

  The line buffer 201 is read by the image reading unit of the image reading device 3, subjected to necessary correction such as shading correction by an image processing unit (not shown), and digital data (for example, 8-bit data) by an A / D conversion circuit (not shown). Image data including the original 6 converted into (data) is temporarily stored for each of a plurality of reading lines. The control unit 200 controls writing and reading of image data to and from the line buffer 201 and the like.

  The reduction processing unit 204 performs reduction processing on the image data of the document 6 read by the image reading unit of the image reading device 3. For example, the reduction processing unit 204 reduces the image data of the original 6 read at a resolution of 600 dpi to 150 dpi of 1/4 along the main scanning direction and to 75 dpi of 1/8 along the sub-scanning direction. . As an algorithm for reducing the image data, a projection method, a simple thinning method, or the like is used.

  If the input image is made up of image data of a plurality of colors such as RGB, monochromatic processing is performed prior to the reduction processing. The monochromatic process is performed by a method using a matrix operation value obtained by multiplying each pixel level of image data by a coefficient value and adding them, or a method for selecting any one color.

  As shown in FIG. 5, the edge detection processing unit 205 performs three detection processes of leading edge detection, left edge detection, and right edge detection on the image data, and each side of the image information of the read document 6 is read. Data indicating an edge portion according to the position (x, y coordinate) of each side of the document 6 by extracting the edge amount for each and binarizing the extracted edge amount with a predetermined threshold. Is output. Data indicating the position (x, y coordinate) for each side of the document 6 is output separately.

  The filter processing of the edge detection processing unit 205 uses three types of filters including a leading edge detection filter, a left edge detection filter, and a right edge detection filter having coefficients as shown in FIG. Extract edges. In the edge extraction data, for example, the background image portion (outside region of the document) is 0, and the document image portion (inside region of the document) is 1. The background image portion (outside area of the original document) or the original image portion (inner area of the original document) is determined based on the amount of light reflected from the regular reflection plate 72 or reflected light from the original 6.

  As shown in FIGS. 7 and 8, the angle calculation processing unit 206 performs processing based on the edge portions (x, y coordinates) of each side of the document image 302 detected by the edge detection processing unit 205. Each process of tip angle detection, left end angle detection, and right end angle detection for calculating the inclination α, β, γ (skew angle) of each side located at the tip, left end, and right end is performed. In the detection processing of each of the tip angle, the left end angle, and the right end angle, a method using a least square method, a Hough transform, or the like is applied.

  As shown in FIG. 2, the position of the document 6 whose image is read by the image reading device 3 is regulated in the direction (width direction) intersecting the conveyance direction by an edge guide (not shown) provided in the document container 60. However, there is a case where the end portion of the document 6 does not necessarily coincide with the transport direction and is transported in an inclined state with an angle with respect to the transport direction. Therefore, as shown in FIG. 8, the original 6 is inclined with respect to the y direction which is the conveyance direction, that is, when the inclination α of the leading edge of the original image 302 when the image of the original 6 is read is 0 °. In addition, there are cases where the inclinations β and γ of the sides located at the left end and the right end of the document image 302 are not 90 °.

  When the least square method is used, as shown in FIG. 9, an approximate expression (y) of a linear function is obtained for each coordinate (x, y) of the edge pixels constituting each side of the document 6 by the least square method. = Ax + b), and the inclination a is set as the angle of the document.

Further, when the Hough transform is used, the following processing is performed.
First, as shown in FIG. 8, the Hough transform is performed on the coordinates (x, y) of the edge pixels constituting each side of the document image 302. At this time, voting (counting up) is performed on a two-dimensional memory that receives R obtained by the calculation of the Hough transform and the parameter θ in the Hough transform formula. After performing the above processing on all the coordinate data of the edge pixels constituting each side of the original image, as shown in FIG. 10, the maximum number of votes (each edge in the Hough space data stored in the two-dimensional memory is displayed. The values θ ₁ and θ ₂ of the θ axis where the line drawn by the pixel overlaps most) are extracted, and the values are determined as the inclination angles of the sides to be obtained. In FIG. 10, each curve corresponds to the coordinates of each edge pixel. In FIG. 10, for convenience, only two angles are shown with θ ₁ and θ ₂ being the values of the θ axis, but the inclination angles of the sides located at the front end, left end, and right end of the document image 302 are shown. α, β, and γ (skew angles) are obtained.

After extracting the inclination angle of each side of the document image 302, the control unit 200 sets the representative value of the inclination angle of each side as the skew angle of the document 6 and sets it in the skew correction processing unit 202. Here, the representative value includes a method of obtaining an average value of the inclination angles of each side, a method of adopting the most reliable angle among the three sides, and the like. The angle with the highest reliability may be the angle having the largest value (voting rate) obtained by the following equation when using the Hough transform.
Voting rate = number of votes for the determined angle ÷ number of pixels after Hough transform

  In addition, when the least square method is used, there is a method of selecting an angle of a side with the smallest error between the approximate expression and each edge coordinate.

  The skew correction processing unit 202 rotates the image data of the document 6 stored in the line buffer 201 by an angle corresponding to the skew angle based on the skew angle obtained by the angle calculation processing unit 206, thereby The skew of the image 302 is corrected.

  By the way, in this embodiment, the control unit 200 is configured to function as a changing unit that changes the correction content of the second correction unit in accordance with the presence or absence of the correction operation by the first correction unit.

  The skew correction processing unit 202 normally takes into account the processing time required for skew correction of the document image 302 and the like, for example, an upper limit value (for example, ± 10) of the skew angle of the document image 302 detected by the edge detection processing unit 205. )) In advance, and when correcting the skew angle of the document image 302, a plurality of steps (for example, 10 steps) in the plus direction and the minus direction, that is, as a correction step size (first unit) that is a correction unit amount. 10 ° ÷ 10 = 1 ° is set.

  Then, the control unit 200 determines whether or not the skew correction of the document 6 is performed by the transport rollers 62 and 64, and after the skew correction of the document 6 is performed by the transport rollers 62 and 64, the skew correction processing unit 202 performs the skew correction. In executing skew correction, the upper limit value of the skew angle of the document image 302 detected by the edge detection processing unit 205 is changed to a second upper limit value (for example, ± 5 °) smaller than the normal value, and correction is performed. The correction step size (second unit), which is a unit amount, is changed to 10 steps in the positive direction and the negative direction when correcting the skew angle of the document image 302, that is, 5 ° ÷ 10 = 0.5 °. ing.

  More specifically, in this embodiment, as shown in FIG. 11, only mechanical skew correction is performed on the control panel 101 operated by the user, and only skew correction by image processing is performed. First to third selection buttons 111 to 113 for selecting one of the operations of executing skew correction by image processing together with skew correction are provided. The control unit 200 is configured to perform a skew correction operation on the document 6 in accordance with the selection buttons 111 to 113 selected by the user.

  The image processing unit 203 performs necessary image processing on the image data of the document 6 on which the skew correction processing has been performed in the skew correction processing unit 202, and then performs exposure of the image forming unit 2 in synchronization with the image formation timing. Image data is output to the device 13.

<Operation of Characteristic Part of Image Reading Apparatus>
In the image reading device 3, when the first reading mode is selected by the user operating the control panel 101, as shown in FIG. 2, the document 6 stored in the document storage unit 61 is sent out as a sending roll 62. The paper is fed one by one by the separating roll 63 and conveyed so as to pass through the reading window 70 by the conveying rolls 64 to 66, and then discharged by the discharge roll 68 to the discharge accommodating portion 67.

  In this embodiment, when the user operates the control panel 101 to select the first reading mode, the selection buttons 111 to 113 are operated to perform only skew correction by image processing. The user can select whether to perform skew correction by image processing together with mechanical skew correction. That is, when the selection button 111 is operated, only mechanical skew correction is performed. When the selection button 112 is operated, only skew correction by image processing is performed, and when the selection button 113 is operated. The skew correction by the image processing is executed together with the mechanical skew correction.

  At that time, the document 6 is illuminated by light irradiated from the illumination lamp 78 and light reflected by the reflector 79 when passing the reading position corresponding to the reading window 70, and the document 6 and its background portion (regular reflection). The reflected light from the plate 72) is reflected by the first to third mirrors 80 to 82, and is imaged and read by the image reading element 83 via the lens 84. The image reading element 83 outputs image data corresponding to the reflected light from the document 6 and its background.

  As shown in FIG. 4, the image data of the document read by the image reading device 3 is sent to the line buffer 201 and temporarily stored, and is sent to the reduction processing unit 204 for reduction processing. The

  The image data reduced by the reduction processing unit 204 is input to the edge detection processing unit 205. As shown in FIGS. 5 and 6, the edge detection processing unit 205 uses the three types of filters to define the boundary (edge part) between the leading edge of the document image 302 and the background image 303 and the left edge of the document image 302. And the boundary (edge portion) between the background image 303 and the right edge of the document image 302 and the background image 302 are detected.

  Data of the leading edge portion, the left edge portion, and the right edge portion of the document image 302 detected by the edge detection processing unit 205 is sent to the angle calculation processing unit 206. In the angle calculation processing unit 206, as shown in FIGS. 8 to 10, the inclination angles of the leading edge, the left edge, and the right edge of the document 6 based on the data of the leading edge portion, the left edge portion, and the right edge portion of the document image 302. α, β, and γ are calculated based on the least square method, the Hough transform method, or the like.

  By the way, the image reading apparatus 3 according to this embodiment performs only mechanical skew correction by the user operating the selection buttons 111 to 113 of the control panel 101 before starting the reading operation of the document 6. Alternatively, it is possible to select whether to perform only skew correction by image processing or to perform skew correction by image processing together with mechanical skew correction.

  When the user selects to perform only mechanical skew correction, the control unit 200 performs only mechanical skew correction processing by the transport rollers 63 and 64 while the document 6 is transported, and performs skew correction processing. Skew correction by the unit 202 is not performed.

  In addition, when the user selects to perform only skew correction by image processing, the control unit 200 does not perform mechanical skew correction processing by the transport rollers 63 and 64 while transporting the document 6. Only skew correction by the skew correction processing unit 202 is executed. At that time, the skew correction processing unit 202 performs normal skew correction processing.

  Further, when the user selects to perform skew correction by image processing together with mechanical skew correction, the control unit 200 performs mechanical skew correction processing by the transport rollers 63 and 64 while the document 6 is transported. After execution, skew correction by the skew correction processing unit 202 is executed.

  When executing the skew correction by the skew correction processing unit 202, the control unit 200 changes the contents of the skew correction processing by the skew correction processing unit 202 as compared with the case where only the skew correction by the skew correction processing unit 202 is executed. .

  Specifically, when executing skew correction by the skew correction processing unit 202, the control unit 200 sets the upper limit value of the skew angle of the document image 302 detected by the edge detection processing unit 205 to be smaller than a normal value. The upper limit of 2 (for example, ± 5 °) is changed, and the correction step size (second unit), which is the correction unit amount, is set to 10 levels in the positive and negative directions when correcting the skew angle of the document image 302. That is, 5 ° ÷ 10 = 0.5 °. Note that the upper limit value of the skew angle of the document image 302 detected by the edge detection processing unit 205 is set to a normal value, for example, ± 10 °, and a correction step size (first unit) that is a correction unit amount. Is 10 ° ÷ 10 = 1.0 °.

  Therefore, when the skew angle α of the front end portion of the document 6 calculated by the angle calculation processing unit 206 is set to 3.5 °, the control unit 200 uses the skew correction processing unit 202 to correct the skew of the document image 302. The skew correction processing unit 202 performs rotation processing on the document image 320 so that the correction step width is 0.5 ° and the skew angle α of the leading edge of the document 6 is 0 °.

  Therefore, according to this embodiment, the correction step amount that is the correction unit amount remains at 10 levels, and the upper limit value of the skew angle of the document image 302 set in the skew correction processing unit 202 is smaller than usual. By changing to an upper limit value (for example, ± 5 °), the correction step width when the skew of the original image 302 is corrected by the skew correction processing unit 202 can be set to 0.5 °. It is possible to improve the accuracy when correcting the skew of the image 302.

  Further, the correction stage when correcting the skew of the document image 302 by the skew correction processing unit 202 may be left at ten stages, so that the time required for the correction process can be avoided.

  On the other hand, in the case of the prior art, when execution of skew correction by image processing is selected regardless of the presence or absence of mechanical skew correction, the document image 302 detected by the edge detection processing unit 205 is selected. Since the upper limit value of the skew angle remains a normal value (for example, ± 10 °), the correction step size (first unit) when correcting the skew of the document image 302 by the skew correction processing unit 202 is 1.0. If the skew angle α at the leading edge of the document 6 is 3.5 °, the skew angle α at the leading edge of the document 6 can be corrected only to 0.5 ° or −0.5 °. This is not possible, and an error of ± 0.5 ° occurs.

  Note that the control unit 200 as an example of a change unit changes the presence / absence of correction for executing a correction operation by image processing to be present when a correction operation based on mechanical skew correction is present, and to be absent when no correction operation is performed. You may comprise. That is, when the document is conveyed without mechanical skew correction, the document 6 may be read with a skew amount that exceeds the correction range of skew correction by image processing. In this case, if skew correction by image processing is executed, the read image of the document 6 may be lost. For example, when an image with an inclination angle of 3 degrees is corrected by 0.5 ° and skew correction by image processing is executed, the image may be lost. For this reason, when there is no correction operation based on mechanical skew correction, it is desirable that the correction operation based on image processing is not changed and executed.

Embodiment 2
FIG. 12 shows a second embodiment of the present invention. The same reference numerals are given to the same parts as those in the first embodiment. In the second embodiment, the size of the original is detected. A detecting unit is provided, and the changing unit is configured to change the correction content of the second correcting unit based on the detection result of the detecting unit.

  That is, in the second embodiment, as shown in FIG. 2, a first detection unit that detects the size in the sub-scanning direction of the document 6 disposed in the document storage unit 60 of the automatic document transport unit 33 is used. And a second sensor 74 as an example of a detecting means for detecting the size of the document 6 in the main scanning direction.

  Based on the output signals from the first and second sensors 73 and 74, the control unit 200 determines whether the size of the document 6 is a standard size such as A4 size, A3 size, or B5 size, or a non-standard size such as a letter size. Or a mixed size in which a plurality of sizes of originals 6 such as A4 size and A3 size are mixed, or a long size such as A3 size novi larger than A3 size. It is assumed that the first and second sensors 73 and 74 cannot determine whether the size is a standard size or a mixed size. In this case, a third detection unit that detects the size of the document 6 being conveyed is provided. It is possible to cope by this means. Note that the user may set whether the size of the document 6 is a standard size, a non-standard size, a mixed size, a long size, or the like on the user setting screen.

  When the control unit 200 determines the size of the document 6 based on the output signals from the first and second sensors 73 and 74, the control unit 200 refers to a table as shown in FIG. Changes the skew correction processing content of the original image 302.

  At this time, if the control unit 200 determines that the size of the document 6 is a regular size or an atypical size and is not a long size or a mixed size, the control unit 200 determines the number of correction steps for determining a correction step size that is a correction unit amount. The upper limit value of the skew angle of the document image 302 detected by the edge detection processing unit 205 is changed to the second upper limit value (for example, ± 5 °) smaller than usual while maintaining the 10 steps.

  On the other hand, when the control unit 200 determines that the size of the document 6 is the long size or the mixed size, the edge detection processing unit maintains the number of correction steps for determining the correction step size as the correction unit amount at 10 steps. The upper limit value of the skew angle of the document image 302 detected at 205 is set to a normal value (for example, ± 10 °).

  As described above, the control unit 200 changes the skew correction processing operation of the document image 302 by the skew correction processing unit 202 based on the size of the document 6, so that the size of the document 6 is a standard size or a non-standard size. In this case, the correction step size, which is the correction unit amount, can be set to 0.5 °, which is a value (second unit) that is substantially smaller than the first unit, which is a normal value. Can be improved.

  As shown in FIG. 12B, the skew correction processing operation of the document image 302 by the skew correction processing unit 202 based on the size of the document 6 is, for example, 15 °, 10 °, and 5 °. A plurality of (three or more) may be changed. In this case, if the correction step size is left at 10 levels, the correction unit amount can be changed to 1.5 °, 0.1 °, and 0.5 °.

  Further, when the control unit 200 determines that the size of the document 6 is a long size or a mixed size, the upper limit value of the skew angle of the document image 302 is set to a normal value (for example, ± 10 °), and the correction unit amount The correction step width can be maintained at 1.0 °, which is a substantially normal value, and skew correction by image processing can be performed on a document 6 having a long size or a mixed size. It becomes.

  In the above-described embodiment, the case where the skew correction of the mechanical document 6 is performed by the transport roll 63 and the transport roll 64 has been described. However, the mechanical document skew is performed only by either the transport roll 63 or the transport roll 64. Of course, it may be configured to perform correction.

  In addition, when the size of the document 6 cannot be determined, the control unit 200 desirably changes the skew correction processing of the document image by image processing so as to have a relatively large step size.

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus 2 ... Image forming part 200 ... Control part 201 ... Line buffer 202 ... Skew correction processing part 203 ... Image processing part 204 ... Reduction processing part 205 ... Edge detection processing part 206 ... Angle calculation processing part

Claims (9)

Image reading means for reading an image of a conveyed document;
First correcting means for mechanically correcting the inclination of the document with respect to the transport direction;
Second correction means for correcting the inclination of the document by image processing;
An image reading apparatus comprising: a changing unit that changes a correction content of the second correction unit in accordance with the presence or absence of a correction operation by the first correction unit. The second correction means includes a first unit and a second unit having a correction amount larger than the first unit as a correction unit amount when executing the correction operation.
2. The image reading apparatus according to claim 1, wherein the changing unit changes the first unit when the correcting operation by the first correcting unit is present and changes to the second unit when the correcting operation is not performed.   The change means changes the presence / absence of correction when the second correction means performs the correction operation to be present when the correction operation by the first correction means is present, and to be changed to none when the second correction means is not. The image reading apparatus according to claim 1, wherein:   When the original is a long original or a mixed-size original, the changing means includes the second correcting means when the correcting operation is performed by the first correcting means, and the first correcting means is provided. 2. The image reading apparatus according to claim 1, wherein the correction operation is changed so that the correction operation is not executed when the correction operation by the correction means is not performed.   3. The image reading apparatus according to claim 2, wherein the changing unit changes the second unit when the original is a long original or a mixed-size original. 4.   The image reading apparatus according to claim 2, wherein the changing unit changes a correction unit amount when the original is a long original to a value larger than that when the original is mixed in size. Detecting means for detecting the size of the document;
7. The change unit according to claim 1, wherein the change unit changes the correction content of the second correction unit based on the presence / absence of a correction operation by the first correction unit and a detection result by the detection unit. The image reading apparatus according to any one of the above. Stop means for stopping the operation of the changing means,
The image reading apparatus according to claim 1, wherein the stopping unit stops the operation of the changing unit when the user instructs to stop the changing unit. An image reading device for reading an image of a document;
Image forming means for forming an image on a recording medium based on an image of a document read by the image reading device;
An image forming apparatus using the image reading apparatus according to claim 1 as the image reading apparatus.

Images