JP2011188021A - Image forming apparatus - Google Patents

Abstract

An image forming apparatus capable of appropriately correcting a variation in reduction ratio in a sub-scanning direction caused by a change in a document conveyance speed at a reading position without interrupting image formation based on the document.
An image of a conveyance speed reference pattern provided on a first reading roller or a second reading roller is read together with an original image by a first reading unit or a second reading unit, and a sub-speed is determined based on the image of the conveyance speed reference pattern. The scaling factor in the scanning zoom is calculated. Then, image formation is performed after the image data of the document is enlarged or reduced in the sub-scanning direction by the sub-scanning variable magnification device at the calculated magnification.
[Selection] Figure 10

Description

  The present invention relates to an image forming apparatus including an image reading apparatus in which a reading position for reading a front surface of a document and a reading position for reading a back surface of the document are provided at different positions on a document transport path.

  Conventionally, an image reading unit that reads the front side of the document on the upstream side of the document transport path and an image reading unit that reads the back side of the document on the downstream side are provided so that both sides of the document can be read simultaneously by one transport. A so-called sheet-through type image reading apparatus is known (see, for example, Patent Document 1, Patent Document 2, and the like). In addition, in the image reading apparatus, there is also known a technique for preventing looseness during document conveyance by increasing the document conveyance speed from the upstream to the downstream of the conveyance path and intentionally conveying the document while applying tension to the document. It has been.

  However, in the above-described sheet-through type image reading apparatus, if it is attempted to prevent the looseness of the document by increasing the document conveyance speed from the upstream to the downstream of the conveyance path, the reading on the back side is better than the reading on the front side. Since the document transport speed is increased, when an image is formed based on the read image data, the image on the back surface is contracted with respect to the image on the front surface at a reduction ratio in the sub-scanning direction corresponding to the document transport direction. There was a problem.

  In view of such a problem, in the technique described in Patent Document 1 described above, when reading a double-sided document, the difference in the reduction ratio in the sub-scanning direction due to the difference in the passing speed between the upstream and downstream reading positions is determined. It is made to respond | correspond by setting the ratio of the reading period from the ratio. Further, in Patent Document 1 described above, a change in reading magnification due to a change in the diameter of a roller that occurs due to deterioration such as wear over time is further calculated based on the difference in the sub-scanning direction of the reference image in each reading line. It is disclosed that the cycle is handled by switching. A technique disclosed in Patent Document 3 is known as a technique for correcting a positional deviation of image data due to a positional difference between a plurality of line sensors in the sub-scanning direction.

  However, in the technique described in Patent Document 1, a reference document on which a reference image composed of a striped pattern image or a trapezoid image is formed is conveyed along the document conveyance path, and the reference image is read from the reference document. Since it is necessary to measure the amount of change in the reading magnification by scanning the image, it is required to interrupt the formation of an image based on a normal document and read the reference image, resulting in a decrease in productivity. .

  The present invention has been made in view of the above, and appropriately corrects the variation in the reduction ratio in the sub-scanning direction caused by the change in the document conveyance speed at the reading position without interrupting the image formation based on the document. An object of the present invention is to provide an image forming apparatus capable of performing the above.

  In order to solve the above-described problems and achieve the object, an image forming apparatus according to the present invention includes a first reading position for reading the front surface of a document at a different position in the document transport path and a second reading position for reading the back surface of the document. In each of the image forming apparatuses, a rotating body that is disposed at each of the first reading position and the second reading position and that conveys a document while rotating, and a rotating body that is provided on each of the rotating bodies, the rotation direction of the rotating body. And a pattern formed in such a manner that a plurality of segments are arranged along the first and second reading positions, and an image for reading a pattern image provided on the rotating body together with an image of a document. A reading unit and an image of a document read by the image reading unit are enlarged in a sub-scanning direction corresponding to a document transport direction at a scaling factor calculated based on the pattern image. Or a sub-scanning direction scaling unit that reduces the size, and an image forming unit that forms an image based on image data of a document that has been enlarged or reduced in the sub-scanning direction by the sub-scanning direction scaling unit. And

  According to the image forming apparatus of the present invention, the image of the pattern provided on the rotating body that conveys the document is read together with the image of the document by the image reading unit, and the image of the document is converted at the scaling factor calculated based on the pattern image. Since image formation is performed by enlarging or reducing in the sub-scanning direction, variations in the reduction ratio in the sub-scanning direction due to changes in the document conveyance speed at the reading position can be achieved without interrupting image formation based on the document. The effect that it can correct | amend appropriately is produced.

FIG. 1 is a configuration diagram showing a schematic configuration of a copying machine. FIG. 2 is a configuration diagram showing details of the ADF provided in the copying machine. FIG. 3 is a block diagram showing an outline of a control mechanism for processing image data of the multifunction machine. FIG. 4 is an enlarged perspective view showing the vicinity of the end of the first reading roller. FIG. 5 is an enlarged perspective view showing the vicinity of the end of the second reading roller. FIG. 6 is a functional block diagram showing a functional configuration of the pattern analysis unit. FIG. 7 is a diagram illustrating a sub-scanning variable magnification device that is realized as one function of the image processing editing unit. FIG. 8 is a diagram illustrating a specific example when an image of a document is read by the first reading unit together with a conveyance speed reference pattern provided on the first reading roller. FIG. 9 is a diagram illustrating a specific example when an image of a document is read by the second reading unit together with a conveyance speed reference pattern provided on the second reading roller. FIG. 10 is a diagram showing an image shrunk in the sub-scanning direction due to the high conveyance speed, in contrast with the image of the conveyance speed reference pattern in the case of the target conveyance speed. FIG. 11 is a diagram illustrating a specific example when an image of a document automatically conveyed by the ADF is read by the second reading unit together with a conveyance speed reference pattern provided on the second reading roller. FIG. 12 is a diagram schematically illustrating how the reference data of the conveyance speed reference pattern provided on the first reading roller is registered as initial data. FIG. 13 is a diagram schematically illustrating how the reference data stored in the sub-scanning scaling data storage unit is updated when the first reading roller is replaced with a new first reading roller. FIG. 14 is a diagram schematically showing a state in which the image data of the second and subsequent documents is subjected to scaling processing in the sub-scanning direction using the scaling factor (correction value) calculated at the time of reading the first document of the document bundle. . FIG. 15 is a diagram illustrating an example of a screen displayed on the operation panel.

  Exemplary embodiments of an image forming apparatus according to the present invention will be explained below in detail with reference to the accompanying drawings. The following embodiments are examples in which the present invention is applied to a copying machine. However, the present invention is not limited to the embodiments exemplified below, and various embodiments can be implemented without departing from the spirit of the present invention. Is possible.

  FIG. 1 is a configuration diagram showing a schematic configuration of a copying machine 1 according to the present embodiment. As shown in FIG. 1, the copying machine 1 includes an automatic document feeder (hereinafter simply referred to as ADF) 2, a paper feeding unit 3, an image reading unit 4, and an image forming unit 5. Has been.

  The ADF 2 includes a document tray 11 and a transport unit 13 including various rollers. The ADF 2 transports the document placed on the document tray 11 by the transport unit 13 onto the slit glass 7, and passes the document that has been read by the image reading unit 4 through the slit glass 7 through the slit glass 7. After that, the paper is discharged onto the paper discharge tray 12. The ADF 2 is a method (sheet through method) that reads the front and back surfaces of a double-sided document with a single conveyance, and has a second reading unit 101 that reads the back surface of the document. When the original is a double-sided original, the second reading unit 101 reads the back side of the original in the process of discharging the original whose surface has been read by the image reading unit 4 to the discharge tray 12. ing. The ADF 2 is attached to the image reading unit 4 so as to be freely opened and closed via an opening / closing mechanism (not shown).

  The paper feeding unit 3 includes paper feeding cassettes 21 and 22 that store recording papers having different paper sizes, and various rollers that transport the recording papers stored in the paper feeding cassettes 21 and 22 to the image forming position of the image forming unit 5. The sheet feeding means 23 is provided.

  The image reading unit 4 is a first reading unit 100 to be described later, and includes a first carriage 25 on which a light source and a mirror member are mounted, a second carriage 26 on which a mirror member is mounted, an imaging lens 27, and imaging. Part 28. The image reading unit 4 irradiates light on a document passing through the slit glass 7 by a light source mounted on the first carriage 25, and from the document by each mirror member mounted on the first carriage 25 and the second carriage 26. The reflected light is folded, and the reflected light is imaged by the imaging lens 27 and read by the imaging unit 28.

  The image forming unit 5 includes an exposure device 31, a photosensitive drum 32, a developing device 33, a transfer belt 34, and a fixing device 35. The image forming unit 5 exposes the photosensitive drum 32 by the exposure device 31 based on the read image read by the imaging unit 28 to form a latent image on the photosensitive drum 32, and the photosensitive drum 32 by the developing device 33. In addition, different color toners are supplied and developed. The image forming unit 5 transfers the image developed on the photosensitive drum 32 by the transfer belt 34 to the recording paper supplied from the paper feeding unit 3, and then transfers the toner image transferred to the recording paper by the fixing device 35. The toner is melted to fix the color image on the recording paper.

  FIG. 2 is a configuration diagram showing details of the ADF 2 provided in the copying machine 1 according to the present embodiment. As shown in FIG. 2, the document tray 11 of the ADF 2 has a movable document table 41 and a pair of side guide plates 42. The movable document table 41 constitutes a front portion of the document tray 11 in the sheet feeding direction, and its front end portion rotates in the vertical direction with the base end portion as a fulcrum. As described above, the document tray 11 can adjust the front end of the document placed on the document tray 11 to an appropriate height by rotating the movable document table 41. Yes.

  A table raising sensor 87 is provided above the front end of the movable document table 41. The table raising sensor 87 detects whether the front end in the feeding direction of the document placed on the document placement surface is held at an appropriate paper feed position having an appropriate height. Note that the appropriate paper feed position according to the embodiment of the present invention refers to a position where the uppermost document in the document bundle and a pickup roller 61 described later come into contact. A home position sensor 88 is provided below the front end of the movable document table 41. Home position sensor 88 detects that movable document table 41 is at the home position.

  On the rear side of the document tray 11 in the paper feeding direction, document length detection sensors 89 and 90 for detecting whether the document is oriented vertically or horizontally are provided at positions separated in the feeding direction. Yes. Note that the document length detection sensors 89 and 90 may be reflective sensors that detect the position of the document edge in a non-contact manner using optical means, or may be contact-type actuator-type sensors. .

  The pair of side guide plates 42 are erected so as to position in the left-right direction with respect to the feeding direction of the document placed on the document tray 11. One of the pair of side guide plates 42 is slidable in the left-right direction with respect to the paper feeding direction, and is configured so that documents of different sizes can be appropriately placed on the document tray 11. A pair of rotating ribs 45 (as movable members described later) are provided on the opposing surfaces of the pair of side guide plates 42.

  Further, a set filler 46 that is rotated by placing a document is provided on the other (fixed side) of the pair of side guide plates 42. In addition, a document set sensor 82 that detects that a document is placed on the document tray 11 is provided at the lowermost part on the movement locus of the tip of the set filler 46. In other words, the document set sensor 82 detects the placement of the document when the document is placed on the document tray 11, the set filler 46 is rotated, and the leading end of the set filler 46 is detached from the document set sensor 82. It is like that.

  The transport unit 13 of the ADF 2 includes a separation feeding unit 51, a pull-out unit 52, a turn unit 53, a first reading transport unit 54, a second reading transport unit 55, and a paper discharge unit 56. .

  The separation feeding unit 51 includes a pickup roller 61 disposed in the vicinity of the sheet feeding port, and a sheet feeding belt 62 and a reverse roller 63 disposed so as to face each other across the conveyance path. The pickup roller 61 is supported by a support arm member 64 attached to the paper feed belt 62, and moves up and down between a contact position that contacts the original bundle via a cam mechanism (not shown) and a separation position that is separated from the original bundle. It comes to move.

  The sheet feeding belt 62 rotates in the feeding direction, and the reverse roller 63 rotates in the direction opposite to the feeding direction. The reverse roller 63 rotates in the reverse direction with respect to the paper feed belt 62 when the originals are double-fed. However, when the reverse roller 63 is in contact with the paper feed belt 62, or only one original is supplied. When the sheet is being conveyed, it is rotated along the sheet feeding belt 62 by the action of a torque limiter (not shown).

  The separation feeding unit 51 feeds the document into the sheet feed port by the pick-up roller 61 being in contact with the uppermost document of the document bundle placed on the document tray 11, and when the document is double fed. The document is separated and sent out by the sheet feeding belt 62 and the reverse roller 63.

  The pull-out unit 52 has a pull-out roller 65 composed of a pair of rollers arranged so as to sandwich the conveyance path. The pull-out unit 52 performs primary abutting alignment of the sent document according to the drive timing of the pull-out roller 65 and the pickup roller 61, and pulls out and transports the aligned document. The pull-out roller 65 is provided with a paper thickness measurement sensor 91 for measuring the paper thickness.

  The turn portion 53 includes an intermediate roller 66 and a reading entrance roller 67 that are a pair of rollers disposed so as to sandwich a curved portion that curves from the top to the bottom of the conveyance path. The turn part 53 turns the original drawn and conveyed by the intermediate roller 66 by conveying the curved part, and conveys the original surface downward by the reading entrance roller 67 to the vicinity of the slit glass 7. ing.

  The first reading and conveying unit 54 includes a first reading roller 68 disposed at a position facing the slit glass 7 across the conveying path, and a conveying path after completion of reading by the image reading unit 4 (first reading unit 100). And a first reading exit roller 69 including a pair of rollers arranged so as to be sandwiched therebetween. The first reading conveyance unit 54 conveys the surface of the document conveyed to the vicinity of the slit glass 7 while being brought into contact with the slit glass 7 by the first reading roller 68, and the document after the reading is completed by the first reading exit roller 69. Further, it is designed to be transported. Here, the first reading roller 68 is provided with a conveyance speed reference pattern for detecting the conveyance speed when the document is read by the image reading unit 4 (first reading unit 100). This transport speed reference pattern is also read. Details of the transport speed reference pattern will be described later.

  The second reading conveyance unit 55 sandwiches the second reading roller 70 disposed at a position facing the second reading unit 101 that reads the back side of the document with the conveyance path interposed therebetween, and the conveyance path after completion of reading the back side of the document. And a pair of second reading exit rollers 71 arranged in this manner. The second reading and conveying unit 55 passes the document whose surface has been read by the second reading roller 70 in front of the reading surface of the second reading unit 101 and conveys the document toward the paper discharge port by the second reading exit roller 71. It is like that. In the case where double-sided scanning is not performed, the document passes through the second reading unit 101. Here, the second reading roller 70 is provided with a conveyance speed reference pattern for detecting the conveyance speed when the original is read by the second reading unit 101. It can be read. Details of the transport speed reference pattern will be described later.

  The paper discharge unit 56 has a pair of paper discharge rollers 72 provided in the vicinity of the paper discharge port, and discharges the original conveyed by the second reading exit roller 71 to the paper discharge tray 12. .

  In addition, the ADF 2 is provided with an abutment sensor 84, a reading entrance sensor 86, a registration sensor 81, and a paper discharge sensor 83 along the conveyance path, and is used for conveyance control such as a conveyance distance and a conveyance speed of the document. It is like that. Further, a document width sensor 85 is provided between the pull-out roller 65 and the intermediate roller 66. The document width sensor 85 is composed of a plurality of light receiving elements arranged in the width direction of the document, and detects the document width based on the light reception result from the irradiation light provided at the opposite position across the conveyance path.

  FIG. 3 is a block diagram illustrating an outline of a control mechanism that processes image data of the multifunction machine 1 according to the present embodiment. The multifunction device 1 has a first reading unit 100, a second reading unit 101, an image data receiving unit 102, a memory control unit 103, a memory 104, and an image processing editing unit 105 as control mechanisms for processing image data. A write image processing unit 106, a VDC 107, a VDB 108, a CPU 109, a ROM 110, a RAM 111, a first pattern analysis unit 112, a second pattern analysis unit 113, an image memory control unit 114, and an ADF control. Unit 115, sub-scanned scaling data storage unit 116, and operation panel 117.

  The image data read by the first reading unit 100 is input to the image data receiving unit 102. The image data receiving unit 102 performs shading correction on the image data read by the first reading unit 100, the level difference due to the region of the image data due to the light amount distribution of the light source, and the photoelectric conversion used by the first reading unit 100. The level difference between each pixel generated when reading with the device is corrected.

  The image data corrected by the image data receiving unit 102 is sent to the memory control unit 103 at the next stage. At this time, the first pattern analysis unit 112 analyzes the image of the conveyance speed reference pattern read together with the document image when reading the document, and the image of the conveyance speed reference pattern that changes according to the conveyance speed at the time of document reading. The pattern switching period, that is, the length (number of lines) in the sub-scanning direction of the image of each segment constituting the transport speed reference pattern is detected.

  The memory control unit 103 accumulates the image data transmitted from the image data receiving unit 102 in the memory 104 in units of frames, takes out the accumulated image data for each frame in accordance with an instruction from the CPU 109, and performs the next-stage image processing editing unit. To 105.

  The image processing editing unit 105 performs various image processing on the image data. In particular, the image processing / editing unit 105 has a function as a sub-scanning variable magnification unit, which will be described in detail later. Process to reduce.

  The image data processed by the image processing editing unit 105 is sent to the image memory control unit 114. The image memory control unit 114 adjusts the processing speed between the reading process and the writing process and performs various processes in units of pages. For this reason, although not shown here, an image memory and storage for storing a large amount of image data are provided so as to be compatible with various processes.

  When image data processing is performed by the image memory control unit 114, processing for copying and outputting the image data is performed thereafter. Specifically, the image data is sent again to the image processing editing unit 105, and the image data received by the image processing editing unit 105 is sent to the writing image processing unit 106. The written image processing unit 106 performs image processing for copy output.

  The image data that has been subjected to the image processing by the writing image processing unit 106 is sent to the VDC 107, where the processing for adjusting the shape of the image data for transferring the image data is performed in the VDC 107 and then in the exposure device 31. Sent to the VDB 108.

  The VDB 108 emits a laser diode to perform exposure processing on the photosensitive drum 32, and forms a latent image corresponding to the image data on the photosensitive drum 32.

  On the other hand, the image data read by the second reading unit 101 has the same flow. That is, the image data read by the second reading unit 101 is input to the image data receiving unit 102 and subjected to processing such as shading correction, and then sent to the memory control unit 103. At this time, the second pattern analysis unit 113 analyzes the image of the conveyance speed reference pattern that is read together with the document image when reading the document, and the image of the conveyance speed reference pattern that changes according to the conveyance speed at the time of document reading. The pattern switching period, that is, the length (number of lines) in the sub-scanning direction of the image of each segment constituting the transport speed reference pattern is detected.

  The image data read by the first reading unit 100 and the image data read by the second reading unit 102 are processed in parallel up to the memory 104. After the image data is stored in the memory 104, the image data is extracted from the memory 104 and processed in units of frames.

  The CPU 109 performs overall control of image processing in the multifunction machine 1, and a program for that purpose is stored in the ROM 110. A RAM 111 is used as a work area necessary for the CPU 109 to operate.

  The ADF control unit 115 that controls the operation of the ADF 2 performs information communication with the CPU 109 to adjust the document conveyance timing.

  The sub-scanning scaling data storage unit 116 stores data required when the image processing editing unit 105 performs sub-scanning scaling processing of an image, and a non-volatile memory is used. Details of the data stored in the sub-scanned scaling data storage unit 116 will be described later.

  The operation panel 117 displays various types of information to the user under the control of the CPU 109, accepts an operation input from the user, and delivers the operation input information to the CPU 109.

  FIG. 4 is an enlarged perspective view showing the vicinity of the end portion of the first reading roller 68 at the position facing the slit glass 7 for reading the original of the first reading conveyance section 54 of the ADF 2. As shown in FIG. 4, a conveyance speed reference pattern P <b> 1 that is a pattern for representing the conveyance speed at the time of document reading on an image is provided at the end of the first reading roller 68. The position of the conveyance speed reference pattern P1 on the first reading roller 68 is a position where the document does not pass during document conveyance, and the image is read by the imaging unit 28 of the image reading unit 4 (first reading unit 100). It is a position that can be. In the present embodiment, the transport speed reference pattern P1 is a stripe pattern in which black and white segments are alternately arranged in the transport direction, and the lengths (segment lengths) of the white and black segments are the same in the transport direction. What is used.

  FIG. 5 is an enlarged perspective view showing the vicinity of the end of the second reading roller 70 at a position facing the second reading unit 101 of the second reading conveyance unit 55. As shown in FIG. 5, similarly to the first reading roller 68, a conveyance speed reference pattern P2 that is a pattern for representing the conveyance speed at the time of document reading on the image is also provided at the end of the second reading roller 70. Is provided. The position of the conveyance speed reference pattern P <b> 2 on the second reading roller 70 is also a position where the original does not pass through the original conveyance, and is a position where the image can be read by the second reading unit 101. The conveyance speed reference pattern P2 is the same as the conveyance speed reference pattern P1, and in the present embodiment, a black and white segment is a stripe pattern alternately arranged in the conveyance direction, and a white segment and a black segment with respect to the conveyance direction. The same length (segment length) is used.

  6A and 6B show a first pattern analysis unit 112 that analyzes an image of a conveyance speed reference pattern P1 read together with a document image by the first reading unit 100 and a conveyance speed reference pattern P2 that is read together with the document image by the second reading unit 101. It is a figure which shows the function structure of the 2nd pattern analysis part 113 which analyzes this image. Since the first pattern analysis unit 112 and the second pattern analysis unit 113 have a common configuration, hereinafter, they are collectively referred to as a pattern analysis unit 120 unless they are particularly distinguished.

  As illustrated in FIG. 6, the pattern analysis unit 120 includes a pattern switching detection unit 130, a line detection unit 131, and a conveyance information detection data storage unit 132. The input image data read by the first reading unit 100 or the second reading unit 101 is data including image data of the conveyance speed reference pattern in addition to the image data of the document. The input image data is input to the pattern change detection unit 130.

  The pattern change detection unit 130 detects the change of the pattern image of the conveyance speed reference pattern provided in each of the reading rollers 68 and 70 (in this embodiment, the boundary between the white segment and the black segment), and A switching detection signal is sent to the line detection unit 131. The line detection unit 131 counts the number of lines from the detection of the switching of the pattern image to the detection of the next switching, and sends the counted number to the conveyance information detection data storage unit 132 of the next stage process. The conveyance information detection data storage 132 stores the line information of the pattern image sent from the line detection unit 131 and outputs it as conveyance information.

  As described above, the pattern analysis unit 120 analyzes the pattern image of the conveyance speed reference pattern, thereby changing the pattern image switching cycle that changes according to the conveyance speed at the time of document reading, that is, the image of the conveyance speed reference pattern. The segment lengths of the individual segments constituting the segment are detected by converting them into the number of lines and output as conveyance information. The conveyance information output from the pattern analysis unit 120 is sent to the memory control unit 103, and is sent from the memory control unit 103 to the image processing editing unit 105 together with the image data of the input image.

  FIG. 7 is a diagram showing the sub-scanning variable magnification unit 140 installed as one function of the image processing editing unit 105. The sub-scanning magnification changer 140 performs enlargement / reduction processing of image data in the sub-scanning direction corresponding to the document transport direction, and expands / contracts the image in the sub-scanning direction caused by variations in the transport speed in document transport. to correct. The image processing / editing unit 105 inputs the image data to the sub-scanning zooming device 140, gives a set scaling factor to the image data, and outputs the image data scaled in the sub-scanning according to the scaling factor. . The start line setting is for setting a start line position for executing the scaling process.

  Here, in particular, in the present embodiment, the set scaling factor that the image processing editing unit 105 gives to the sub-scanning zooming unit 140 is set based on the conveyance information output from the pattern analysis unit 120. Specifically, based on the conveyance information output from the pattern analysis unit 120, the image processing editing unit 105 responds to the segment length of the image of the conveyance speed reference pattern read together with the original image, that is, according to the actual conveyance speed. The segment length (the number of lines) of the image of the conveyance speed reference pattern that will be changed in this way is recognized. Then, the segment length of the image of the conveyance speed reference pattern actually read together with the image of the original is compared with the segment length of the image of the conveyance speed reference pattern at the target conveyance speed, and the magnification according to the difference is set. The set magnification is input to the sub-scanning magnification changer 140. Note that the segment length (number of lines) data of the image of the conveyance speed reference pattern at the target conveyance speed is stored in advance in the sub-scanning scaling data storage unit 116 as reference data.

  FIG. 8 is a diagram showing a specific example when an image of a document automatically conveyed by the ADF 2 is read by the first reading unit 100 (image reading unit 4) together with a conveyance speed reference pattern P1 provided on the first reading roller 68. (A) shows an example of an image of a document, and (b) shows an example of an input image input to the image data receiving unit 102 when the image of (a) is read by the first reading unit 100, respectively. Yes.

  As shown in FIG. 8B, the input image read by the first reading unit 100 is not only the original reading area which is the original image area, but also the conveyance speed reference which is the image area of the conveyance speed reference pattern P1. Includes area. That is, this input image has an area corresponding to the reading width (reading sensor reading area) by the reading sensor of the first reading unit 100 in the main scanning direction, and the conveyance speed reference area at a position outside of the original reading area. In this transport speed reference area, the transport speed reference pattern P1 provided on the first reading roller 68 is reproduced as an image.

  In the example shown in FIG. 8, the speed of document conveyance by the first reading conveyance unit 54 of the ADF 2 is a target speed. For this reason, the input image read by the first reading unit 100 has the read length in the sub-scanning direction coincident with the original length, and the original image is accurately reproduced without expanding or contracting in the sub-scanning direction. Therefore, in this case, the scaling factor of the sub-scanning zooming device 140 is set to 1, and the correction of image data by the sub-scanning scaling device 140 is not performed.

  FIG. 9 is a diagram illustrating a specific example when an image of a document automatically conveyed by the ADF 2 is read by the second reading unit 101 together with a conveyance speed reference pattern P2 provided on the second reading roller 70. (B) shows an example of an input image input to the image data receiving unit 102 when the second reading unit 101 reads the image (a).

  As shown in FIG. 9B, the input image read by the second reading unit 101 is the reading sensor of the second reading unit 101 in the main scanning direction, like the input image read by the first reading unit 100. Has a reading sensor reading area corresponding to the reading width of the sheet, and there is a conveyance speed reference area at a position outside the original reading area, and a conveyance speed reference pattern provided on the second reading roller 70 in this conveyance speed reference area. P2 is reproduced as an image.

  In the example shown in FIG. 9, the document conveyance speed by the second reading conveyance unit 55 of the ADF 2 is higher than the target speed. Therefore, the input image read by the second reading unit 101 is reproduced in such a manner that the reading length in the sub-scanning direction is shorter than the original length, and the original image is contracted in the sub-scanning direction. On the other hand, when the speed of document conveyance by the second reading conveyance unit 55 is slower than the target speed, the input image read by the second reading unit 101 has a reading length in the sub-scanning direction of the document length. The original image is reproduced in the form of being enlarged in the sub-scanning direction. Note that the variation in the reduction ratio of the input image in the sub-scanning direction due to the variation in the document conveying speed can occur in the same way for the input image read by the first reading unit 100.

  FIG. 10 shows the input image shown in FIG. 9B (an image contracted in the sub-scanning direction due to the high transport speed) in contrast to the image of the transport speed reference pattern for the target transport speed. FIG. As shown in FIG. 10, when the transport speed is faster than the target transport speed, the image of the transport speed reference pattern is shorter than the case where the segment length of each segment is the target transport speed. Become. On the other hand, when the transport speed is slower than the target transport speed, the image of the transport speed reference pattern is longer than the case where the segment length of each segment is the target transport speed. Therefore, an appropriate scaling factor in the sub-scanning direction of the image data of the document can be derived from the ratio of the segment lengths of the image of the conveyance speed reference pattern.

  Specifically, as described above, each segment length of the image of the conveyance speed reference pattern that changes according to the conveyance speed at the time of reading by the image reading units 100 and 101 is converted into the number of lines in the pattern analysis unit 120. To detect. Then, the image processing editing unit 105 stores each segment length of the image of the conveyance speed reference pattern detected by the pattern analysis unit 120 as a segment length stored in advance as reference data in the sub-scanning scaling data storage unit 116, That is, in comparison with the segment length of the image of the transport speed reference pattern at the target transport speed, a scaling factor in the sub-scanning direction is set according to the ratio and input to the sub-scanning variable transformer 140, A document image shrunk in the scanning direction is corrected.

  By the way, in the example of the input image shown in FIG. 9B, the document conveyance speed by the second reading conveyance unit 55 of the ADF 2 is higher than the target speed over the entire area in the sub-scanning direction of the document image. For example, when the second reading roller 70 of the second reading conveyance unit 55 is decentered due to wear over time, local speed fluctuations occur during reading of the document image, and the document image It is also assumed that the reduction ratio in the sub-scanning direction partially varies. Similarly, even when the first reading roller 68 of the first reading conveyance unit 54 is decentered due to wear over time, local speed fluctuations occur during reading of the document image, and the document image in the sub-scanning direction. A case where the reduction ratio partially fluctuates is also assumed.

  FIG. 11 is a diagram illustrating a specific example when the image of the document automatically conveyed by the ADF 2 is read by the second reading unit 101 together with the conveyance speed reference pattern P2 provided on the second reading roller 70. Is an example of an input image that is read by the second reading unit 101 and input to the image data receiving unit 102 in a state in which the document conveying speed by the second reading and conveying unit 55 of the ADF 2 is a target speed, (b) Is read by the second reading unit 101 in a state where the second reading roller 70 is decentered due to wear over time, and the document conveying speed by the second reading conveying unit 55 is locally higher than the target speed. In this example, input images input to the image data receiving unit 102 are shown.

  As shown in FIG. 11B, when the document conveyance speed is locally varied from the target speed during reading by the second reading unit 101, the reduction ratio of the input image in the sub-scanning direction partially changes. become. In the example of FIG. 11B, the original is read from the leading edge of the input image to the position m as in the case of FIG. 11A, so that the original image can be reproduced. However, in the image range of M lines from the position of m to the position of m ′, the image is contracted in the sub-scanning direction due to the influence of local conveyance speed fluctuation due to the eccentricity of the second reading roller 70. It is an image. Further, since the conveyance speed returns to the target speed after the position of m ′, an image as the original can be reproduced.

  When the reduction ratio in the sub-scanning direction of the input image partially varies as shown in FIG. 11B, the scaling factor set in the sub-scanning zooming device 140 is partially set between the position m and the position m ′. By switching to, a partially shrunken image can be corrected. Specifically, individual segment lengths of the image of the conveyance speed reference pattern detected by the pattern analysis unit 120 and output as conveyance information are subordinate from the leading edge of the input image to the position m and after the position m ′. This coincides with the segment length stored as reference data in the scanning magnification data storage unit 116. Therefore, in these regions, the scaling factor set in the sub-scanning variable transformer 140 is 1. On the other hand, in the region for M lines from the position m to the position m ′ of the input image, the segment length of the image of the conveyance speed reference pattern detected by the pattern analysis unit 120 and output as conveyance information is sub-scanned. This is shorter than the segment length (segment length of the image of the transport speed reference pattern in the case of the target transport speed) stored as reference data in the scaling data storage unit 116. Therefore, in the area of M lines from the position m to the position m ′ of the input image, the magnification set in the sub-scanning variable magnification unit 140 is set to the segment length of the image of the conveyance speed reference pattern in the input image. The value is determined according to the ratio with the segment length of the reference data. As a result, even when the document conveyance speed locally fluctuates due to the eccentricity of the second reading roller 70 and the input image is partially distorted in the sub-scanning direction, such partial distortion is reduced. It can be corrected appropriately.

  FIG. 12 schematically shows how the reference data of the conveyance speed reference pattern P1 provided on the first reading roller 68 is registered as initial data. As shown in FIG. 12, the first reading roller 68 is rotated so as to achieve a target conveying speed, and the conveying speed reference pattern P <b> 1 for one rotation of the first reading roller 68 is read by the first reading unit 100 and conveyed. Image data of the speed reference pattern P1 is acquired. Then, by analyzing the image data of the transport speed reference pattern P1 by the first pattern analysis unit 112, the segment length of each segment is detected, and the image of the transport speed reference pattern P1 at the target transport speed is detected. Individual segment lengths (reference data) are registered in the sub-scanned scaling data storage unit 116 as initial data.

  Although not shown, the conveyance speed reference pattern P2 provided on the second reading roller 70 is similarly rotated so as to realize a conveyance speed aimed at the second reading roller 70, and the second reading roller The second reading unit 101 reads the conveyance speed reference pattern P2 for one round of 70 to acquire image data of the conveyance speed reference pattern P2. Then, by analyzing the image data of the transport speed reference pattern P2 by the second pattern analysis unit 113, the segment length of each segment is detected, and the image of the transport speed reference pattern P2 in the case of the target transport speed is detected. The segment length (reference data) is registered in the sub-scanned scaling data storage unit 116 as initial data.

  The registration of the initial data as described above is performed, for example, by the manufacturer at a stage before the MFP 1 is shipped from the factory. The initial data registration process varies depending on each device to be shipped due to variations in the first reading roller 68 and the second reading roller 70, variations in roller bearings on the device side, component assembly errors, and the like. It is executed individually.

  The segment length data (reference data) of the image of the conveyance speed reference patterns P1 and P2 registered as initial data is, for example, the first reading by the CPU 109 executing the data calibration program to operate the multifunction device 1. The image data of the conveyance speed reference patterns P1 and P2 in a state of being rotated so as to realize the conveyance speed aimed at the roller 68 and the second reading roller 70 is acquired, and the segment length of each segment is newly detected. As a result, it is possible to update the data with a new segment length at an arbitrary timing. When the reference data registered in the sub-scanning scaling data storage unit 116 is updated, the scaling factor is set in the sub-scanning scaling unit 140 using new reference data.

  It is effective to update the reference data stored in the sub-scanning magnification data storage unit 116, for example, when the first reading roller 68 or the second reading roller 70 is replaced. FIG. 13 schematically shows how the reference data stored in the sub-scanning scaling data storage unit 116 is updated when the first reading roller 68 is replaced with a new first reading roller 68 ′. is there. As described above, the registration of the initial data for the conveyance speed reference pattern P1 is a state in which the multifunction machine 1 is rotated so as to realize the conveyance speed aimed at the first reading roller 68 in the stage before the factory shipment. This is carried out by detecting the individual segment length of the image data of the transport speed reference pattern P1. After that, when the first reading roller 68 is replaced with a new first reading roller 68 ′, for example, the CPU 109 executes a data calibration program to operate the multi-function device 1 and the new first reading roller 68 ′. By acquiring the image data of the transport speed reference pattern P1 ′ in a state rotated so as to realize the transport speed aiming at, and detecting the segment length of each segment of the transport speed reference pattern P1 ′, The initial data stored in the sub-scanning scaling data storage unit 116 is updated to data of individual segment lengths of the newly detected transport speed reference pattern P1 ′.

  Although FIG. 13 illustrates an example in which the reference data is updated when the first reading roller 68 is replaced, the reference data is similarly updated when the second reading roller 70 is replaced. Further, not only the first reading roller 68 and the second reading roller 70 but also the exchange processing occurs in the same way for various parts related to the document conveyance, so that the document conveyance is affected. The calibration data may be executed to update the reference data stored in the sub-scanned scaling data storage unit 116. Thereby, it is possible to effectively suppress the occurrence of variations in the correction of the reduction ratio of the document image in the sub-scanning direction due to component variations.

  In the above description, each time the document is read, the pattern analysis unit 120 analyzes the images of the conveyance speed reference patterns P1 and P2, and compares the individual segment lengths of the images of the conveyance speed reference patterns P1 and P2 with the reference data. Thus, the scaling factor set in the sub-scanning zooming device 140 is calculated, but the scaling factor once calculated is stored in the sub-scanning scaling data storage unit 116 as a correction value, and this sub-scanning scaling factor is stored. Using the correction value stored in the data storage unit 116, the sub-scanning magnification changer 140 may perform the scaling process in the sub-scanning direction. Specifically, for example, when a document bundle composed of a plurality of documents is set on the document tray 11 of the ADF 2, sub-scan scaling is performed when the first document of the document bundle composed of a plurality of documents is read. The scaling factor is calculated by the device 140 and stored as a correction value in the sub-scanning scaling data storage unit 116, and the sub-scanning scaling data is stored when reading the second and subsequent documents in the document bundle. Using the correction value stored in the unit 116, the sub-scanning magnification changer 140 performs a scaling process in the sub-scanning direction.

  FIG. 14 schematically shows a state in which the image data of the second and subsequent documents is subjected to scaling processing in the sub-scanning direction using the scaling factor (correction value) calculated at the time of reading the first document in the document bundle. is there. At the time of reading the first original of the original bundle, individual segment lengths of the images of the conveyance speed reference patterns P1 and P2 that change according to the conveyance speed at the time of original reading are converted into the number of lines by the pattern analysis unit 120 and detected. Then, the individual segment lengths of the images of the conveyance speed reference patterns P1 and P2 detected by the pattern analysis unit 120 are compared with the reference data stored in the sub-scanning scaling data storage unit 116, and according to the ratio. A magnification ratio in the sub-scanning variable magnification unit 140 is calculated. The calculated scaling factor is stored in the sub-scanning scaling data storage unit 116 as a correction value, and the calculated scaling factor is input to the sub-scanning scaling unit 140 as a setting scaling factor, so that the first original image A scaling process (correction process) is performed on the data in the sub-scanning direction.

  After that, when reading the second and subsequent originals of the original bundle, the pattern analysis unit 120 does not analyze the images of the conveyance speed reference patterns P1 and P2, and performs sub-scanning scaling on the image data of the second and subsequent originals. In the case of performing the scaling process in the sub-scanning direction by the device 140, the scaling factor stored as the correction value in the sub-scanning scaling data storage unit 116 is input to the sub-scanning scaling unit 140 as the set scaling factor. A scaling process (correction process) in the sub-scanning direction is performed on the image data of the original.

  When a document bundle composed of a plurality of documents is set on the document tray 11 of the ADF 2, for example, a screen for accepting a user operation input as shown in FIG. In response to a user operation input from the panel 117, the magnification (correction value) is calculated by the sub-scanning magnification changer 140 every time the document is read, or the sub-scanning magnification is changed only at the time of reading the first document of the document bundle. Whether to calculate the scaling factor (correction value) in the device 140 may be switched. In the screen example of the operation panel 117 shown in FIG. 15, when the user operates the “1” button, the scaling factor in the sub-scanning variable magnification unit 140 is calculated when each document in the document bundle is read. The sub-scanning scaling process is executed at the calculated scaling ratio. On the other hand, when the “2” button is operated by the user, the zoom ratio is calculated by the sub-scanning zooming device 140 only when the first document of the document bundle is read, and the calculated scaling ratio is used as the sub-scanning scaling. The sub-scanning scaling process for the image data of the second and subsequent originals stored in the data storage unit 116 as a correction value is executed using the correction value stored in the sub-scanning scaling data storage unit 116.

  In addition, a button for instructing the operation panel 117 to calculate the scaling factor (correction value), for example, so that the scaling factor (correction value) can be calculated by the sub-scanning zooming device 140 at an arbitrary timing. Is displayed, and when this button is operated by the user, the scaling factor in the sub-scanning zooming device 140 is calculated, and the calculated scaling factor is stored in the sub-scanning scaling data storage unit 116 as a correction value. Thereafter, the sub-scanning scaling process of the image may be executed at a scaling factor stored as a correction value in the sub-scanning scaling data storage unit 116.

  As described above in detail with reference to specific examples, the copying machine 1 according to the present embodiment has the images of the conveyance speed reference patterns P1 and P2 provided on the first reading roller 68 and the second reading roller 70. Are read together with the image of the original by the first reading unit 100 and the second reading unit 101, and the magnification ratio in the sub-scanning variable magnification unit 140 is calculated based on the images of the conveyance speed reference patterns P1 and P2. Then, image formation is performed after the image data of the document is enlarged or reduced in the sub-scanning direction by the sub-scanning magnification changing device 140 at the calculated magnification. Therefore, according to the copying machine 1, the variation in the reduction ratio in the sub-scanning direction caused by the change in the document conveyance speed at the reading position of the document image is appropriately corrected to form an image that accurately reproduces the document image. be able to.

  Further, in order to correct the variation in the reduction ratio of the original image in the sub-scanning direction, the copying machine 1 conveys, for example, a reference original on which a reference image is formed along a conveyance path, and the reference image is transferred from the reference original. Since it is not necessary to perform processing such as reading and measuring the amount of change in the reading magnification, it is possible to correct variations in the reduction ratio of the original image in the sub-scanning direction without interrupting image formation based on a normal original. There is no loss of productivity.

  Further, the conveyance speed reference patterns P1 and P2 are the end positions of the first reading roller 68 and the second reading roller 70 that are out of contact with the original, and the first reading unit 100 and the second reading unit. Since it is provided at a position where the image can be read by the image 101, it is possible to effectively prevent adverse effects such as show-through on the reading of the original image, and to perform image formation with high reproducibility. .

  Further, the copying machine 1 according to the present embodiment has the conveyance speed reference patterns P1 and P2 that are read when the first reading roller 68 and the second reading roller 70 are rotated so that the conveyance speed of the document becomes an appropriate speed. The segment length of the image is stored in the sub-scanned scaling data storage unit 116 as reference data, and the segment length of the image of the conveyance speed reference patterns P1 and P2 read when reading the actual document image is compared with the reference data. Since the magnification to be input to the sub-scanning variable magnification device 140 is set according to the ratio of these segment lengths, the first reading roller 68 and the second reading roller 70 have variations as parts. However, it is possible to appropriately correct the variation in the reduction ratio of the original image in the sub-scanning direction without being affected by the variation of the individual components.

  Further, the copying machine 1 according to the present embodiment has the conveyance speed reference pattern P1 in a state where the first reading roller 68 and the second reading roller 70 are rotated so that the conveyance speed of the document becomes an appropriate speed at an arbitrary timing. , P2 is read, the segment length of the images of the conveyance speed reference patterns P1, P2 is detected, and the reference data stored in the sub-scanning scaling data storage unit 116 is updated with the newly detected segment length. Thus, the variation in the reduction ratio of the original image in the sub-scanning direction can be appropriately corrected without being affected by the temporal change of the first reading roller 68 and the second reading roller 70.

  In addition, the copying machine 1 according to the present embodiment updates the reference data as described above when replacing the first reading roller 68 and the second reading roller 70, so that the document image is not affected by the replacement of parts. The variation in the reduction ratio in the sub-scanning direction can be corrected appropriately.

  Further, the copying machine 1 according to the present embodiment stores the sub-scanning magnification that has been calculated once in the sub-scanning scaling data storage unit 116 as a correction value, and the sub-scanning scaling data storage unit 116 stores the correction value as a correction value. If the sub-scanning magnification change process is performed in the sub-scanning magnification changer 140 using the stored magnification ratio, it is possible to efficiently carry out correction of variation in the reduction ratio of the original image in the sub-scanning direction. For example, when a document bundle composed of a plurality of documents is set on the document tray 11 of the ADF 2, the sub-scanning magnification data storage unit 116 calculates the sub-scanning magnification when reading the image of the first document. Is stored as a correction value, and for the second and subsequent originals, a sub-scanning scaling process in the sub-scanning scaling unit 140 is performed using the scaling factor stored in the sub-scanning scaling data storage unit 116 as a correction value. By performing the above, it is possible to efficiently perform the variation correction of the reduction ratio in the sub-scanning direction of the document image.

  In addition, the copier 1 according to the present embodiment displays a button for the user to instruct the timing of sub-scanning magnification calculation on the operation panel 117, and when this button is operated by the user, the sub-operation scaling factor is displayed. The operability can be improved by performing the calculation.

1 Copier 2 ADF
68 First Reading Roller 70 Second Reading Roller 100 First Reading Unit 101 Second Reading Unit 105 Image Processing Editing Unit 109 CPU
112 1st pattern analysis part 113 2nd pattern analysis part 116 Subscanning magnification data storage part 117 Operation panel 120 Pattern analysis part 140 Subscanning magnification changer P1, P2 Conveyance speed reference pattern

Japanese Patent No. 4312726 Japanese Patent No. 4182072 JP 2006-179970 A

Claims (9)

An image forming apparatus having a first reading position for reading a front surface of a document at a different position in a document transport path and a second reading position for reading a back surface of the document.
A rotating body that is disposed at each of the first reading position and the second reading position and conveys a document while rotating;
A pattern that is provided on each of the rotating bodies and is formed so that a plurality of segments are arranged along the rotation direction of the rotating bodies;
Image reading means disposed at the first reading position and the second reading position, respectively, for reading an image of a pattern provided on the rotating body together with an image of a document;
A sub-scanning direction scaling unit that enlarges or reduces an image of the document read by the image reading unit in a sub-scanning direction corresponding to the document transport direction at a scaling factor calculated based on the image of the pattern;
An image forming apparatus comprising: an image forming unit that forms an image based on image data of an original that has been enlarged or reduced in the sub scanning direction by the sub scanning direction scaling unit.   The image forming apparatus according to claim 1, wherein the pattern is a striped pattern in which segments having different densities are alternately arranged at regular intervals along a rotation direction of the rotating body.   2. The pattern according to claim 1, wherein the pattern is provided at an end position deviating from a position where the original of the rotating body contacts and within a reading range by the image reading unit. The image forming apparatus according to 2. Reference data storage means for storing, as reference data, the segment length of each segment in the image of the pattern when the rotating body is rotated so that the document transport speed is an appropriate speed,
The sub-scanning direction scaling unit calculates a ratio between the segment length of the pattern image actually read together with the original image by the image reading unit and the reference data, and the scaling unit according to the calculated ratio. The image forming apparatus according to claim 1, wherein a magnification is set.   The reference data stored in the reference data storage means is newly detected by detecting the segment length of the image of the pattern when the rotating body is rotated so that the document transport speed becomes an appropriate speed. 5. The image forming apparatus according to claim 4, further comprising reference data updating means for updating with the determined segment length.   The reference data update unit is configured to provide an image segment of the pattern provided on the new rotating body when the new rotating body is rotated so that the document transport speed becomes an appropriate speed when the rotating body is replaced. 6. The length is detected, and the reference data stored in the reference data storage means is updated with a segment length of an image of the pattern provided in a new rotating body. Image forming apparatus. A scaling factor storage unit that stores a scaling factor calculated based on the image of the pattern read by the image reading unit;
The sub-scanning direction scaling unit enlarges or reduces an image of a document read by the image reading unit in the sub-scanning direction using a scaling factor stored in the scaling factor storage unit. The image forming apparatus according to any one of 1 to 6.   The sub-scanning direction scaling unit calculates the scaling factor and stores it in the scaling factor storage unit at the time of forming an image of the first document of a document bundle composed of a plurality of documents, and stores it in the scaling factor storage unit. 8. The original image read by the image reading unit is enlarged or reduced in the sub-scanning direction by using the magnification stored in the magnification storage unit when the original image is formed. The image forming apparatus described in 1. Further comprising an instruction means for the user to instruct the timing of scaling factor calculation by the sub-scanning direction scaling unit;
The image forming apparatus according to claim 7, wherein the sub-scanning direction scaling unit calculates the scaling factor when the instruction unit is operated.