JP2018185479A - Image forming apparatus, control program, and control method - Google Patents

Abstract

An image forming apparatus 10 includes a CPU 100, an image forming unit 30, and a paper detection unit 80. The image forming unit 30 includes the first paper transport path L1 and forms an image on the paper transported through the first paper transport path L1. The paper detection unit 80 includes a line sensor 82 and a reference member 84. The line sensor 82 and the reference member 84 are disposed at positions facing each other across the first paper transport path L1. A reference pattern including a dark first region 840 and a light second region 842 is formed on the surface of the reference member 84. The CPU 100 compares the reference image including the entire reference pattern with the detection image including a part of the reference pattern and a part of the sheet conveyed on the first sheet conveyance path L1, and compares the edge of the sheet in the width direction. The position of the part is detected.
[Effect] The detection accuracy of the position of the end portion in the width direction of the paper can be enhanced.
[Selection] Figure 5

Description

  The present invention relates to an image forming apparatus, a control program, and a control method, and more particularly to an image forming apparatus, a control program, and a control method for forming an image on a sheet.

  Patent Document 1 discloses an example of a background art image forming apparatus. Background Art An image forming apparatus includes a line sensor and a guide member. The guide member is a black member, and is provided at a position facing the line sensor across the paper transport path. When the paper is transported on the paper transport path, the position where the color difference between the white paper and the black guide member in the image taken by the line sensor is detected as the position of the edge in the paper width direction. Is done.

JP 2007-298772 A

  However, in the image forming apparatus of the background art, when an image is formed at the edge in the width direction of the paper, black is detected even at the position where the paper exists, and the position of the edge in the width direction of the paper is erroneously detected. There is a problem of detecting.

  Therefore, a main object of the present invention is to provide a novel image forming apparatus, control program, and control method.

  Another object of the present invention is to provide an image forming apparatus, a control program, and a control method that can improve the detection accuracy of the position of the end of the sheet in the width direction.

  1st invention is an image forming apparatus provided with an image formation part, a line sensor, a reference member, and a detection means. The image forming unit includes a paper transport path and forms an image on a paper transported through the paper transport path. The line sensor is provided so as to extend in the width direction of the paper in the paper transport path. The reference member is provided at a position facing the line sensor across the paper conveyance path, and a reference pattern in which a dark first region and a light second region are regularly arranged on a surface facing the line sensor. It is formed. However, the color can be expressed in the Munsell color system (color display method based on JIS Z 8721 three attributes), and can be determined by comparison with a standard color chart based on JIS Z 8721, for example. In the present invention, the light color is a color having a lightness of 5 or more in the Munsell color system, and the dark color is a color having a lightness of less than 5. The detection means detects a position where the regularity of the reference pattern is interrupted in the width direction of the paper in a detection image including a part of the paper conveyed by the line sensor and a part of the reference pattern. Detect as end position.

  According to the first invention, in the detection image including a part of the sheet conveyed on the sheet conveyance path imaged by the line sensor and a part of the reference pattern, the position where the regularity of the reference pattern is interrupted is determined. Therefore, even if an image is formed on the paper, the detection accuracy of the position of the edge in the width direction of the paper can be improved.

  A second aspect of the invention is an image forming apparatus according to the first aspect of the invention, wherein the detection means detects a candidate position that is a candidate for the position of the edge in the width direction of the paper based on the detection image. Position detection means, and determination means for determining the candidate position as the position of the edge in the paper width direction based on whether or not the regularity of the reference pattern is interrupted inside the paper width direction from the candidate position. Including.

  According to the second invention, the same operational effects as the first invention can be obtained, and the detection accuracy of the position of the end portion in the width direction of the paper can be increased.

  A third invention is an image forming apparatus according to the first or second invention, wherein the size of the first area in the width direction of the paper is larger than the size of the second area in the width direction of the paper.

  According to the third aspect of the invention, since the size of the dark first region in the width direction of the paper is larger than the size of the light second region in the width direction of the paper, there is a margin at the end of the paper in the width direction. Can be detected with high accuracy in the width direction of the paper.

  A fourth invention is an image forming apparatus according to any one of the first to third inventions, further comprising a storage means for storing a reference image including a reference pattern, wherein the detection means includes a reference image and a detection The position where the regularity of the reference pattern is interrupted is detected in the detection image by comparing with the image for detection.

  In the fourth invention, since the reference image stored in the storage means is used, an image of an ideal reference pattern can be used even when paper dust or dust adheres to the reference member. For this reason, the detection accuracy of the position of the edge part of the width direction of a paper can be raised.

  A fifth invention is an image forming apparatus according to the fourth invention, wherein the storage means is a nonvolatile memory.

  According to the fifth aspect, the same effects as the third aspect can be achieved, and an image of an ideal reference pattern can be used. Therefore, the detection accuracy of the position of the end in the width direction of the paper is improved. Can do.

  A sixth invention is an image forming apparatus according to the fourth or fifth invention, wherein the storage means stores the lightness of the first area and the lightness of the second area included in the reference image, and the detection means comprises The position of the edge in the width direction of the paper is detected according to the brightness of the first area and the brightness of the second area included in the reference image and the brightness of each read pixel of the detection image.

  According to the sixth aspect, since the brightness of the first area and the brightness of the second area included in the reference image are used, even when a sheet other than white is used, the edge in the width direction of the sheet is accurately obtained. Can be detected.

  A seventh invention is an image forming apparatus according to any one of the fourth to sixth inventions, and is detected by an adhering matter detection means for detecting the position of the adhering matter adhering to the reference member, and the adhering matter detection means. And a correction unit that corrects the detection image according to the position of the adhered matter, and the detection unit conveys the sheet according to the reference image including the reference pattern and the detection image corrected by the correction unit. The position of the edge in the width direction of the sheet conveyed along the path is detected.

  According to the seventh aspect of the present invention, the image forming apparatus further includes a correcting unit that corrects the detection image according to the position of the attached matter attached to the reference member. Therefore, even when the attached matter adheres to the reference member, the paper is accurately obtained. The position of the end in the width direction can be detected.

  An eighth invention is an image forming apparatus according to any one of the first to seventh inventions, wherein the first region is assumed to pass through an end portion in a main scanning direction of a sheet used in the image forming apparatus. It is arranged at the assumed position.

  According to the eighth aspect, since the first area is arranged at the assumed position where the end portion in the main scanning direction of the paper used in the image forming apparatus is assumed to pass, the margin is formed at the end portion in the width direction of the paper. Can be detected with high accuracy in the width direction of the paper.

  A ninth invention is an image forming apparatus according to any one of the first to eighth inventions, and is formed on the paper according to the position of the end in the width direction of the paper detected by the detecting means. Adjusting means for adjusting the position of the image in the width direction of the paper.

  According to the ninth aspect, since the position in the width direction of the image formed on the sheet is adjusted according to the position of the end portion in the width direction of the sheet, the positional deviation of the image formed on the sheet is reduced. Can be prevented.

  A tenth aspect of the invention includes an image forming unit that includes a sheet conveyance path and forms an image on a sheet conveyed through the sheet conveyance path, and a line sensor provided in the sheet conveyance path so as to extend in the width direction of the sheet. A reference pattern is formed at a position facing the line sensor across the paper conveyance path, and the dark first region and the light second region are regularly arranged on the surface facing the line sensor. A control program for an image forming apparatus including a reference member, wherein the image of the image forming apparatus includes a part of a sheet conveyed through a sheet conveyance path imaged by a line sensor and a part of a reference pattern. In FIG. 2, the position where the regularity of the reference pattern is interrupted is made to function as a detecting means for detecting the position of the edge in the width direction of the paper.

  An eleventh aspect of the invention includes an image forming unit that includes a sheet conveyance path and forms an image on a sheet conveyed through the sheet conveyance path, and a line sensor provided in the sheet conveyance path so as to extend in the width direction of the sheet; A reference pattern is formed at a position facing the line sensor across the paper conveyance path, and the dark first region and the light second region are regularly arranged on the surface facing the line sensor. A processor of an image forming apparatus including a reference member has (a) regularity of the reference pattern in a detection image including a part of a sheet conveyed by a line sensor and a part of a reference pattern conveyed on a sheet conveyance path. The step of detecting the position where the interruption occurs as the position of the end in the width direction of the sheet is executed.

  According to the tenth and eleventh aspects, the same operational effects as those of the first aspect can be achieved, and the detection accuracy of the position of the end in the width direction of the paper can be increased.

  According to this invention, the detection accuracy of the position of the edge part of the width direction of a paper can be improved.

FIG. 1 is an illustrative view showing a schematic configuration of an image forming apparatus according to a first embodiment of the present invention. FIG. 2 is a side view showing a schematic configuration of a sheet detection unit provided in the image forming apparatus of FIG. FIG. 3 is an illustrative view of the paper detection unit viewed from the paper conveyance direction. 4 is a block diagram showing an electrical configuration of the image forming apparatus of FIG. FIG. 5 is an illustrative view showing a reference pattern formed on the reference member of the first embodiment. FIG. 6A is an illustrative view showing a case where a margin is present at the end of the paper in the main scanning direction, and FIG. 6B is an illustrative view showing a case where no margin is present at the end of the paper in the main scanning direction. FIG. FIG. 7 is an illustrative view showing one example of a memory map of the RAM shown in FIG. FIG. 8 is a flowchart showing an example of detection processing of the image forming apparatus. FIG. 9 is an illustrative view showing a method for detecting a deposit in the second embodiment. FIG. 10 is an illustrative view showing a method of detecting an edge position in the second embodiment. FIG. 11 is a flowchart showing an example of detection processing in the second embodiment. FIG. 12 is an illustrative view showing a reference pattern of a reference member in the third embodiment. FIG. 13 is an illustrative view showing a reference pattern of a reference member in the fourth embodiment.

[First embodiment]
Referring to FIG. 1, an image forming apparatus 10 according to an embodiment of the present invention is an electrophotographic image forming apparatus having a double-sided printing function, and includes processes of charging, exposure, development, transfer, and thermal fixing. As a result, a multicolor or single color image is formed (printed) on the front and back surfaces of the paper (recording medium).

  In the first embodiment, the image forming apparatus 10 is a multifunction peripheral (MFP) having a copying function, a printer function, a scanner function, a facsimile function, and the like. However, the image forming apparatus 10 does not have to be limited to a multifunction peripheral, and may be any one of a copying machine, a printer, and a facsimile. Further, the image forming apparatus 10 may be a color machine or a monochrome machine.

  In the present invention, the direction in which the paper is conveyed (paper conveyance direction) is referred to as the sub-scanning direction. On the other hand, the direction orthogonal to the direction in which the paper is conveyed is called the main scanning direction. Therefore, the vertical direction of the conveyed paper corresponds to the sub-scanning direction. Further, the width direction of the conveyed paper corresponds to the main scanning direction.

  First, the basic configuration of the image forming apparatus 10 will be schematically described. As shown in FIG. 1, the image forming apparatus 10 includes an apparatus main body 12 including an image forming unit 30 and the like, and an image reading apparatus 14 disposed above the apparatus main body 12.

  The image reading device 14 includes a document placing table 16 formed of a transparent material. A document pressing cover 18 is attached above the document placing table 16 through a hinge or the like so as to be freely opened and closed. The document pressing cover 18 is provided with an ADF (automatic document feeder) 24 that automatically feeds the documents placed on the document placing tray 20 one by one to the image reading position 22. Further, an operation unit 28 (see FIG. 4) including a touch panel and operation buttons for receiving an input operation such as a print start instruction by a user is provided on the front side of the document table 16.

  The image reading device 14 includes an image reading unit 26 including a light source, a plurality of mirrors, an imaging lens, a line sensor, and the like. The image reading unit 26 exposes the document surface with a light source, and guides the reflected light reflected from the document surface to the imaging lens by a plurality of mirrors. Then, the reflected light is imaged on the light receiving element of the line sensor by the imaging lens. The line sensor detects the luminance and chromaticity of the reflected light imaged on the light receiving element, and generates image data based on the image on the document surface. As the line sensor, a charge coupled device (CCD), a contact image sensor (CIS), or the like is used.

  The image forming unit 30 includes an exposure device 32, a developing device 34, a photoconductor drum 36, a photoconductor cleaner unit 38, a charger 40, a transfer unit 42, a fixing unit 44, and the like, and a paper feed tray 48 or a manual paper feed tray 50. Then, an image is formed on the paper conveyed from the printer, and the paper on which the image has been formed is discharged to the paper discharge tray 52. As image data for forming an image on a sheet, image data read by the image reading unit 26 or image data transmitted from an external computer is used.

  The image data handled in the image forming apparatus 10 corresponds to four color images of black (K), cyan (C), magenta (M), and yellow (Y). For this reason, each of the developing device 34, the photoconductor drum 36, the photoconductor cleaner unit 38, and the charger 40 is provided in four units so as to form four types of electrostatic latent images corresponding to the respective colors. One image station is configured.

  The photosensitive drum 36 is an image carrier in which a photosensitive layer is formed on the surface of a conductive cylindrical substrate. The charger 40 is a member that charges the surface of the photosensitive drum 36 to a predetermined potential. is there. The exposure device 32 is configured as a laser scanning unit including a laser diode (LD) and a polygon mirror, and is disposed below the photosensitive drum 36. The exposure device 32 exposes the surface of the charged photosensitive drum 36 to form an electrostatic latent image corresponding to the image data on the surface of the photosensitive drum 36. The developing device 34 visualizes the electrostatic latent image formed on the photoconductive drum 36 with toner of four colors (YMCK). The photoreceptor cleaner unit 38 removes toner remaining on the surface of the photoreceptor drum 36 after development and image transfer.

  The transfer unit 42 includes an intermediate transfer belt 54, a driving roller 56, a driven roller 58, four intermediate transfer rollers 60 and a secondary transfer roller 62, and is disposed above the photosensitive drum 36. Note that the transfer unit 42 does not necessarily include the intermediate transfer belt 54, and a configuration in which the toner image on the photosensitive drum 36 is directly transferred to a sheet may be employed.

  The intermediate transfer belt 54 is an endless belt having flexibility, and is formed of a synthetic resin or rubber appropriately blended with a conductive material such as carbon black. The intermediate transfer belt 54 is suspended by a driving roller 56 and a driven roller 58, and is arranged so that the outer peripheral surface thereof is in contact with the outer peripheral surface of the photosensitive drum 36. The intermediate transfer belt 54 rotates in a predetermined direction as the driving roller 56 rotates.

  The drive roller 56 is provided so as to be rotatable around its axis by a drive unit (not shown). The driven roller 58 rotates as the intermediate transfer belt 54 rotates and applies a constant tension to the intermediate transfer belt 54 to prevent the intermediate transfer belt 54 from loosening.

  The intermediate transfer roller 60 is disposed at a position facing each photosensitive drum 36 with the intermediate transfer belt 54 interposed therebetween. During image formation, a predetermined voltage (primary transfer voltage) is applied to the intermediate transfer roller 60, whereby a transfer electric field is formed between the photosensitive drum 36 and the intermediate transfer belt 54. The toner image formed on the outer peripheral surface of the photosensitive drum 36 is transferred to the outer peripheral surface of the intermediate transfer belt 54 by the action of the transfer electric field.

  The secondary transfer roller 62 is provided so as to press the intermediate transfer belt 54 with the driving roller 56. During image formation, a predetermined voltage (secondary transfer voltage) is applied to the secondary transfer roller 62, whereby a transfer electric field is formed between the intermediate transfer belt 54 and the secondary transfer roller 62. The toner image formed on the outer peripheral surface of the intermediate transfer belt 54 is applied to the sheet while the sheet passes through the transfer nip region between the intermediate transfer belt 54 and the secondary transfer roller 62 by the action of the transfer electric field. Transfer (secondary transfer) is performed.

  The fixing unit 44 includes a heat roller 64 and a pressure roller 66 and is disposed above the secondary transfer roller 62. The heat roller 64 is set to have a predetermined fixing temperature. When the paper passes through the nip region between the heat roller 64 and the pressure roller 66, the toner image transferred to the paper is melted. The toner image is heat-fixed on the sheet by mixing and pressing.

  In such an apparatus main body 12, a sheet for feeding paper from the paper feed tray 48 or the manual paper feed tray 50 to the paper discharge tray 52 via the registration roller 68, the secondary transfer roller 62 and the fixing unit 44 is provided. A one-sheet conveyance path L1 is formed. Further, when performing duplex printing on a sheet, the sheet after printing on the front side and passing through the fixing unit 44 is transferred to the first sheet conveyance path on the upstream side in the sheet conveyance direction of the secondary transfer roller 62. A second paper transport path L2 for returning to L1 is formed. In the first paper transport path L1 and the second paper transport path L2, a plurality of transport rollers 70 are provided as appropriate to supplementarily apply a driving force to the paper.

  The registration roller 68 is also called a paper stop roller (PS roller), and conveys the sheet at a speed equal to the process speed at which the image forming unit 30 forms an image of the sheet. For example, the registration roller 68 waits (temporarily stops) while sandwiching the sheet conveyed by the conveying roller 70, and starts conveying the sheet in synchronization with the transfer unit 42. At this time, the registration roller 68 is rotated at a peripheral speed equal to the peripheral speed of the intermediate transfer belt 54.

  When single-sided printing is performed in the apparatus main body 12, the sheets are guided one by one from the sheet feeding tray 48 or the manual sheet feeding tray 50 to the first sheet conveying path L <b> 1 and conveyed to the registration rollers 68 by the conveying rollers 70. . Then, the registration roller 68 conveys the sheet to the secondary transfer roller 62 (transfer nip portion) at a timing when the leading edge of the sheet and the leading edge of the image information on the intermediate transfer belt 54 are aligned, and the toner image is transferred onto the sheet. Is done. Thereafter, when the toner passes through the fixing unit 44 (fixing nip portion), the unfixed toner on the paper is melted and fixed by heat, and the paper is discharged onto the paper discharge tray 52.

  On the other hand, when performing double-sided printing, when the rear end portion of the sheet that has passed through the fixing unit 44 after the front side printing is finished reaches the conveyance roller 70 near the paper discharge tray 52, the conveyance roller 70 is reversed. By rotating, the sheet runs backward and is guided to the second sheet conveyance path L2. The paper guided to the second paper transport path L2 is transported through the second paper transport path L2 by the transport roller 70, and is guided to the first paper transport path L1 on the upstream side of the registration roller 68 in the paper transport direction. At this time, the front and back sides of the sheet are reversed, so that the sheet passes through the registration roller 68 and then passes through the secondary transfer roller 62 and the fixing unit 44, whereby printing is performed on the back side of the sheet.

  However, center lines (see FIG. 3) in the main scanning direction (width direction of the conveyed paper) are set in the first paper conveyance path L1 and the second paper conveyance path L2. The sheet is conveyed on the basis of the center so that the center in the main scanning direction is along the center line in the main scanning direction of the first sheet conveying path L1 and the second sheet conveying path L2.

  FIG. 2 is a side view showing a schematic configuration of the sheet detection unit 80 provided in the image forming apparatus 10 of FIG. FIG. 3 is an illustrative view of the sheet detection unit 80 included in the image forming apparatus 10 as viewed from the sheet conveyance direction.

  As shown in FIGS. 1 and 2, the first paper transport path L1 includes a paper detection unit 80 for detecting the position of the end of the paper in the main scanning direction (end of the paper in the width direction). Provided. The sheet detection unit 80 is disposed between the registration roller 68 and the conveyance roller 70 disposed on the upstream side of the registration roller 68 in the sheet conveyance direction. In addition, the paper detection unit 80 is disposed on the upstream side of the registration roller 68 in the paper transport direction and on the downstream side of the joining position of the first paper transport path L1 and the second paper transport path L2 in the paper transport direction. . Further, when the minimum size paper used in the image forming apparatus 10 is held between the registration rollers 68 and stopped, the paper detection unit 80 is located downstream of the rear end position of the paper in the paper conveyance direction. Be placed. That is, the paper detection unit 80 is disposed at a position where the paper exists when the paper is nipped by the registration rollers 68 and stopped.

  Also, as shown in FIG. 3, the paper detection unit 80 is provided so as to extend in the main scanning direction. The paper detection unit 80 is provided from the position of the center line in the main scanning direction of the first paper transport path L1 to the position where the end (edge) in the main scanning direction of the largest size paper passes. That is, the paper detection unit 80 is provided at a position where the edge of the paper transported through the first paper transport path L1 passes regardless of the paper size.

  The sheet detection unit 80 includes a line sensor 82 and a reference member 84. As shown in FIGS. 1 to 3, the line sensor 82 and the reference member 84 are disposed so as to face each other with the first paper transport path L1 interposed therebetween.

  The line sensor 82 is disposed on the secondary transfer roller 62 side (pressure roller 66 side) of the first paper transport path L1. That is, the line sensor 82 is disposed on the non-printing side (non-image forming side) of the first paper transport path L1. On the other hand, the reference member 84 is disposed on the intermediate transfer belt 54 side (heat roller 64 side) of the first paper transport path L1. That is, the reference member 84 is disposed on the printing side (image forming side) of the first paper transport path L1.

  The line sensor 82 is an imaging device such as a CCD or CIS, and includes a plurality of light receiving elements 820 and a light source. The plurality of light receiving elements 820 and the light source are provided on the surface of the line sensor 82 facing the reference member 84. Each light receiving element 820 is arranged in a line in the main scanning direction. The light source is, for example, an LED, and is provided along the plurality of light receiving elements 820. Further, the plurality of light receiving elements 820 and the light source pass through one end portion in the main scanning direction of the largest size sheet from the position of the center line in the main scanning direction of the first paper transport path L1 in the main scanning direction. It is provided so as to include the position. However, one of the plurality of light receiving elements 820 is arranged at a position overlapping the center line of the first paper transport path L1 in the main scanning direction in the main scanning direction. The light receiving element 820 serves as a reference in the main scanning direction of the line sensor 82. In addition, the position of the light receiving element 820 serving as a reference in the main scanning direction becomes the reference position of the line sensor 82 in the main scanning direction.

  The line sensor 82 exposes the sheet conveyed through the reference member 84 or the first sheet conveyance path L1 with a light source, and detects the reflected light reflected by the light receiving element 820. The light receiving element 820 detects the brightness and chromaticity of the reflected light and generates image data. The line sensor 82 outputs captured image data that is a set of image data generated by the plurality of light receiving elements 820.

  The reference member 84 has a substantially rectangular plate shape and is provided so as to extend in the main scanning direction. The reference member 84 is made of, for example, a synthetic resin. The reference member 84 is provided in a range corresponding to at least the plurality of light receiving elements 820 included in the line sensor 82 in the main scanning direction.

  4 is a block diagram showing an electrical configuration of the image forming apparatus of FIG. Referring to FIG. 4, image forming apparatus 10 includes a CPU 100. A RAM 102, a memory 104, a sensor control unit 106, an image reading unit 26, an image forming unit 30, and an operation unit 28 are connected to the CPU 100 via a bus 110. A line sensor 82 is connected to the sensor control unit 106.

  The CPU 100 governs overall control of the image forming apparatus 10. The RAM 102 is used as a work area and a buffer area for the CPU 100. The memory 104 is a main storage device of the image forming apparatus 10, and appropriately stores a control program and data for the CPU 100 to control the operation of each part of the image forming apparatus 10. As the memory 104, a non-volatile memory such as a ROM, HDD, flash memory, or EEPROM can be used.

  The sensor control unit 106 includes a controller 106a and an SRAM 106b. Under the instruction of the CPU 100, the controller 106 a inputs a control signal to the line sensor 82 and drives each of the plurality of light receiving elements 820 included in the line sensor 82. Further, the controller 106 a turns on or off the light source of the line sensor 82 under the instruction of the CPU 100.

  The read signal (analog signal) output from the line sensor 82 is input to the SRAM 106b. However, the read signal input from the line sensor 82 is A / D converted and temporarily stored in the SRAM 106b as photographed image data. The captured image data is read (output) from the SRAM 106b in response to a read request from the CPU 100. However, the captured image data corresponding to the captured image acquired by the line sensor 82 is image data including a plurality of pixel (read pixel) data arranged in a line in the main scanning direction. Each of the plurality of read pixel data included in the photographed image corresponds to each of the image data generated by each of the plurality of light receiving elements 820. That is, each of the plurality of reading pixels corresponds to each of the plurality of light receiving elements 820. Note that the size of the read pixel (the imaging range of one light receiving element 820) is about 0.1 mm.

  As described above, the operation unit 28 is a part that receives an input operation by the user, and includes a touch panel, operation buttons, and the like. A signal indicating setting information such as the number of sheets to be printed, whether double-sided printing is performed and the type of paper, and a print start instruction, which are input using the operation unit 28, are input to the CPU 100.

  Note that the electrical configuration of the image forming apparatus 10 illustrated in FIG. 4 is merely an example, and need not be limited to this.

  In the image forming apparatus configured as described above, a member having a black surface is used as the reference member. In this case, the read pixels read by each of the plurality of light receiving elements of the line sensor are distinguished as white or black. White reading pixels are output from the light receiving elements at positions facing the paper, and black reading pixels are output from the light receiving elements at positions not facing the paper (facing the reference member). Then, the position that is the boundary between the white reading pixel and the black reading pixel is detected as the position of the edge of the sheet in the main scanning direction (edge position of the sheet).

  Further, the position of the image formed on the paper in the main scanning direction (printing position in the main scanning direction) is adjusted in accordance with the detected edge position of the paper. Specifically, the position of the image formed on the paper in the main scanning direction is adjusted by adjusting the position of the toner image (electrostatic latent image) formed on the outer peripheral surface of the photosensitive drum. However, a shift mechanism may be provided between the sheet detection unit 80 and the transfer nip region between the intermediate transfer belt 54 and the secondary transfer roller 62. In this case, instead of adjusting the position of the toner image formed on the outer peripheral surface of the photosensitive drum, the main scanning direction of the image formed on the paper is adjusted by adjusting the position of the paper in the main scanning direction. The position of is adjusted.

  However, when the paper is transported, a deposit such as paper dust or dust may adhere to the surface of the reference member. In this case, a white read pixel is output from the light receiving element at a position facing the deposit. For this reason, there is a problem in that the position where the adherent has adhered to the surface of the reference member is erroneously detected as the edge position of the paper.

  In order to avoid this problem, when a predetermined number (for example, 8 pixels) or more of white reading pixels are continuously output, it is conceivable to detect them as the edge position of the paper. However, when an image is formed on the paper, the size of the margin at the edge of the paper may be smaller than the size of the predetermined number of read pixels. In this case, there is a problem in that a predetermined number of white reading pixels are not continued at the edge of the sheet, and the edge position of the sheet cannot be detected. This problem occurs because when the back side is printed in double-sided printing, the front side on which the image is first formed is conveyed so as to be the line sensor 82 side.

  In order to avoid such an inconvenience, in the first embodiment, a reference pattern in which a dark first region and a light second region are regularly arranged on the surface of the reference member 84 is formed.

  However, in the present invention, the color can be expressed in the Munsell color system (color display method based on JIS Z 8721 three attributes), and can be determined by comparison with a standard color chart based on JIS Z 8721, for example. The light color is, for example, a color having a lightness of 5 or more in the Munsell color system, and the dark color is a color having a lightness of less than 5, for example.

  FIG. 5 is an illustrative view showing a reference pattern formed on the reference member 84 of the first embodiment. As shown in FIG. 5, a reference pattern including black as a dark color and white as a bright color is formed on the surface of the reference member 84. For example, white in the reference pattern is a color having a brightness of 7 or more, and black is a color having a brightness of 3 or less.

  The reference pattern includes a plurality of black first regions 840 and a plurality of white second regions 842. Specifically, the first regions 840 and the second regions 842 are alternately arranged in the main scanning direction. That is, the reference pattern is a striped pattern in the sheet transport direction formed by the plurality of first regions 840 and the plurality of second regions 842. For this reason, the second region 842 is disposed on both sides of the first region 840 in the main scanning direction. In addition, first regions 840 are arranged on both sides of the second region 842 in the main scanning direction.

  In addition, each of the plurality of first regions 840 has the same size in the main scanning direction. Similarly, each of the plurality of second regions 842 has the same size in the main scanning direction. Further, the size of the first region 840 in the main scanning direction is larger than the size of the second region 842 in the main scanning direction.

  Specifically, the size of the first region 840 in the main scanning direction is a size corresponding to a plurality of (for example, four) reading pixels (light receiving elements 820 of the line sensor 82). The size of the second region 842 in the main scanning direction is a size corresponding to one read pixel. For this reason, the reference pattern of the first embodiment includes a first region 840 having a size corresponding to four read pixels and a second region 842 having a size corresponding to one read pixel. A plurality of groups Gr are included.

  In the first embodiment, a photographed image (hereinafter referred to as “reference image”) having a reference pattern of the reference member 84 as a subject, and a reference pattern of the reference member 84 and a sheet conveyed on the first sheet conveyance path L1 are defined as the subject. A captured image (hereinafter referred to as “detection image”) is captured by the line sensor 82. Then, the edge position of the sheet is detected according to the difference between the reference image data 304c corresponding to the reference image and the detection image data 304d (see FIG. 7) corresponding to the detection image. Hereinafter, a specific method for detecting the edge position of the paper will be described.

  First, the reference image is captured when there is no sheet passing through the sheet detection unit 80. For example, the image is captured at the stage where the image forming apparatus 10 is manufactured (before being shipped from a factory or the like). When the reference image is captured, all the light receiving elements 820 included in the line sensor 82 are driven, and all the light sources included in the line sensor 82 are turned on. Therefore, the reference image includes the entire reference pattern of the reference member 84. When the reference image is captured, reference image data 304 c corresponding to the reference image is stored in the memory 104.

  However, the reference image includes a plurality of pixels (reference reading pixels) corresponding to the plurality of light receiving elements 820, respectively. The reference image data 304c corresponding to the reference image includes a plurality of reference read pixel data corresponding to each of the plurality of reference read pixels. Each of the plurality of reference read pixel data includes light receiving element 820 information, position information, and color information. The light receiving element 820 information is information of the light receiving element 820 corresponding to the reference read pixel data. The position information is information about the position in the main scanning direction according to the distance between the light receiving element 820 corresponding to the reference read pixel data and the above-described light receiving element 820 serving as the reference in the main scanning direction. That is, the position information of the reference read pixel data is also information on the position of the reference read pixel corresponding to the reference read pixel data in the main scanning direction. The color information is information indicating the color of the reference reading pixel corresponding to the reference reading pixel data in black or white. This color information is set according to the brightness of the reference read pixel corresponding to the reference read pixel data. When the lightness of the reference read pixel corresponding to the reference read pixel data is equal to or higher than a predetermined threshold (for example, lightness 5), white is assigned to the reference read pixel data. On the other hand, when the brightness of the reference read pixel corresponding to the reference read pixel data is less than a predetermined threshold, black is assigned to the reference read pixel data.

  As described above, the detection image is picked up when the paper transported through the first paper transport path L1 reaches the paper detection unit 80. However, the time when the paper reaches the paper detection unit 80 means that the paper is held by the registration roller 68 and stopped. That is, the detection image is an image captured when a sheet exists between the line sensor 82 and the reference member 84.

  When a detection image is captured, a part of the light receiving elements 820 included in the line sensor 82 is driven, and the light source is turned on according to the position of the driven light receiving elements 820. Specifically, a light receiving element included in a predetermined range in the main scanning direction around a position (assumed position) where the end of the sheet conveyed in the first sheet conveying path L1 is assumed to pass. 820 is driven. However, the range in which the light receiving element 820 is driven is set in consideration of variations during conveyance in the main scanning direction of the sheet conveyed on the first sheet conveyance path L1. For this reason, the detection image includes a part of the reference pattern of the reference member 84 and a part of the sheet conveyed through the first sheet conveyance path L1. However, when performing duplex printing, the sheet conveyed through the first sheet conveyance path L1 passes through the sheet detection unit 80 twice. For this reason, when performing double-sided printing, a detection image when the front side of the paper is printed (front side detection image) and a detection image when the back side of the paper is printed (back side detection) Image) for each of the images.

  When the detection image is captured, detection image data 304d corresponding to the detection image is temporarily stored in the SRAM 106b. The detection image data 304d stored in the SRAM 106b is read from the SRAM 106b in response to an instruction from the CPU 100.

  However, the detection image includes a plurality of reading pixels (detection reading pixels) corresponding to the plurality of light receiving elements 820, as in the above-described reference image. Therefore, the detection image data 304d corresponding to the detection image includes a plurality of detection read pixel data corresponding to each of the plurality of detection read pixels. Each of the plurality of detection read pixel data includes light receiving element information, position information, and color information, similarly to the above-described partial reference image data.

  When the detection image is captured, the CPU 100 reads the reference image data 304c from the memory 104 and reads the detection image data 304d from the SRAM 106b, and compares the reference image data 304c and the detection image data 304d. The edge position of the paper is detected according to the difference between the reference image data 304c and the detection image data 304d.

  Specifically, first, a position where the color of the reference read pixel at the same position and the color of the detection read pixel are different is detected. Here, each color information of the plurality of reference read pixel data included in the reference image data 304c is compared with each color information of the plurality of detection read pixel data included in the detection image data 304d. More specifically, the color information of the reference read pixel data at the same position is compared with the color information of the detection read pixel data.

  When the color information of the reference read pixel data at the same position matches the color information of the detection read pixel data, the color of the reference read pixel at the position of the read pixel corresponding to the read pixel data, It is determined that the color of the detection reading pixel matches.

  On the other hand, when the color information of the reference read pixel data at the same position is different from the color information of the detection read pixel data, the color of the reference read pixel is set at the position of the read pixel corresponding to the read pixel data. It is determined that the color of the detection read pixel is different.

  Of the positions where the color of the reference read pixel is different from the color of the detection read pixel, the position farthest from the center line in the main scanning direction (the position outside in the width direction) is set as the edge candidate position of the paper. .

  Next, it is determined whether or not the regularity of the reference pattern is interrupted on the side closer to the center line in the main scanning direction than the edge candidate position (inside the main scanning direction) in the detection image. Whether or not the regularity of the reference pattern is interrupted depends on whether the detection image has a color different from that of the reference image in the group Gr (including the group Gr including the edge candidate position) inside the main scanning direction from the edge candidate position. It is determined depending on whether a position exists.

  In the group Gr inside the main scanning direction from the edge candidate position, when there is a position where the detection image has a different color from the reference image, it is determined that the regularity of the reference pattern is interrupted in the group Gr. Is done. On the other hand, in the group Gr inside the main scanning direction from the edge candidate position, when there is no position where the detection image has a different color from the reference image, the regularity of the reference pattern is not interrupted in the detection image. (The regularity of the reference pattern is maintained).

  When it is determined that the regularity of the reference pattern is interrupted in the group Gr inside the main scanning direction from the edge candidate position, the above-described edge candidate position is detected (determined) as the edge position of the sheet.

  However, if it is determined that the regularity of the reference pattern is interrupted in the group Gr inside the main scanning direction from the edge candidate position, the next edge candidate position inside the edge candidate position is set. Then, it is determined whether the regularity of the reference pattern is interrupted on the side closer to the center line in the main scanning direction than the next edge candidate position.

  FIG. 6A is an illustrative view showing a case where a margin is present at the end of the paper in the main scanning direction, and FIG. 6B is an illustrative view showing a case where no margin is present at the end of the paper in the main scanning direction. FIG. In FIGS. 6A and 6B, it is assumed that the back side is printed after the image is printed on the front side in double-sided printing. However, it is assumed that the image printed on the front side of the paper has a lightness smaller than a predetermined threshold, and the color information of the image data for partial detection corresponding to the portion where the image is printed indicates black. Further, it is assumed that a portion (margin) where a paper image is not printed has a brightness higher than a predetermined threshold value and indicates white.

  As shown in FIG. 6A, when there is a margin at the edge of the paper in the main scanning direction, the color information of the detection read pixel data at the position corresponding to the margin of the paper indicates white. . On the other hand, the color information of the reference read pixel data at the position corresponding to the first area 840 of the reference pattern indicates black. For this reason, when the margin of the paper and the first area 840 of the reference pattern overlap, there is a position where the color of the reference reading pixel and the color of the detection reading pixel are different. In the example shown in FIG. 6A, the color of the reference read pixel is black and the color of the detection read pixel is white at the positions of the eighth and ninth read pixels from the left. That is, the color of the reference read pixel is different from the color of the detection read pixel. Then, the position of the eighth read pixel from the left outermost in the main scanning direction among the read pixels in which the color of the reference read pixel is different from the color of the detection read pixel is set as the edge candidate position. Further, it is determined that the regularity of the reference pattern is interrupted in the second group Gr2 including the eighth and ninth read pixels from the left.

  Further, the color information of the detection read pixel data corresponding to the portion where the image of the paper is printed indicates black. On the other hand, the color information of the reference read pixel data corresponding to the second area 842 of the reference pattern in the reference image data 304c indicates white. For this reason, when the portion on which the paper image is printed and the second area 842 of the reference pattern overlap, there is a position where the color of the reference read pixel and the color of the detection read pixel are different. In the example shown in FIG. 6A, the color of the reference reading pixel is white at the positions corresponding to the third and eighth reading pixels from the right (15th and 20th from the left), and the detection reading pixels The color is black. That is, the color of the reference read pixel is different from the color of the detection read pixel. Therefore, the regularity of the reference pattern is interrupted in the third group Gr3 from the left including the eighth read pixel from the right and the fourth group Gr4 from the left including the third read pixel from the right. To be judged.

  Thus, in the example shown in FIG. 6A, the regularity of the reference pattern is interrupted in all the groups Gr inside the main scanning direction from the edge candidate position (the eighth read pixel from the left). The edge candidate position is determined as the sheet edge position.

  Further, as shown in FIG. 6B, when there is no margin at the end of the paper in the main scanning direction, the color information of all the detection read pixel data at the position corresponding to the paper indicates black. . Therefore, there is a position where the color of the reference read pixel and the color of the detection read pixel are different at a position where the sheet and the second area 842 of the reference pattern included in the reference image overlap.

  In the example shown in FIG. 6B, at the positions corresponding to the tenth, fifteenth and twentieth read pixels from the left, the color of the reference read pixel (white) and the color of the detection read pixel (black) are the same. Different. Of the read pixels having different reference read pixel colors and detection read pixel colors, the position corresponding to the tenth read pixel from the left most outside in the main scanning direction is set as the edge candidate position. Further, the second group Gr2 from the left including the tenth read pixel from the left, the third group Gr3 from the left including the fifteenth read pixel from the left, and the fourth from the left including the twentieth read pixel from the left. In the second group Gr4, it is determined that the regularity of the reference pattern is interrupted.

  Thus, in the example shown in FIG. 6B, the regularity of the reference pattern is interrupted in all the groups Gr inside the main scanning direction from the edge candidate position (the tenth read pixel from the left). The edge candidate position is determined as the sheet edge position. Although the position shifted by two pixels with respect to the actual position of the edge of the paper is determined, the size of the read pixel is about 0.1 mm, so that the print quality is not greatly affected.

  The above-described operation of the image forming apparatus 10 is realized by the CPU 100 executing a control program stored in the RAM 102. Specific processing will be described later with reference to a flowchart.

  FIG. 7 is an illustrative view showing one example of a memory map 300 of the RAM 102 shown in FIG. As shown in FIG. 7, the RAM 102 includes a program storage area 302 and a data storage area 304. The program storage area 302 of the RAM 102 stores the control program for the image forming apparatus 10 as described above. The control program includes an operation detection program 302a, a reference image acquisition program 302b, a detection image acquisition program 302c, an edge candidate position detection program 302d, a determination program 302e, an image reading program 302f, and an image formation program 302g.

  The operation detection program 302a is a program for detecting a user's operation input through the operation buttons and the touch panel included in the operation unit 28. In accordance with the operation detection program 302a, the CPU 100 detects operation data or an operation signal when the user operates the operation button, or detects touch coordinate data input when the touch panel is operated.

  The reference image acquisition program 302b controls the sensor control unit 106 to capture a reference image including the entire reference pattern of the reference member 84 with the line sensor 82 when there is no sheet passing through the sheet detection unit 80. This is a program for acquiring reference image data 304c corresponding to a reference image.

  The detection image acquisition program 302c controls the sensor control unit 106 so that the line sensor 82 includes a part of the reference pattern of the reference member 84 and a part of the sheet when the sheet passes through the sheet detection unit 80. This is a program for capturing an image and obtaining detection image data 304d corresponding to the detection image.

  The edge candidate position detection program 302d compares the reference image data 304c acquired according to the reference image acquisition program 302b with the detection image data 304d acquired according to the detection image acquisition program 302c, and determines the above-described edge candidate position. It is a program for detecting.

  The determination program 302e compares the reference image data 304c and the detection image data 304d to determine whether the regularity of the reference pattern is interrupted on the side closer to the center line in the main scanning direction than the edge candidate position. It is a program for.

  The image reading program 302f is a program for controlling the image reading unit 26 to read an image of a document and to output an image signal (image data) corresponding to the read image.

  The image forming program 302g is a program for controlling the image forming unit 30 to print a multicolor or single color print image on paper according to the print image data 304b. However, the image forming program 302g determines the position of the toner image (electrostatic latent image) formed on the outer peripheral surface of the photosensitive drum 36 in the main scanning direction according to the edge position detected by the edge candidate position detection program 302d. It is also a program for adjusting.

  Although illustration is omitted, the program storage area 302 also stores programs for selecting and executing various functions of the image forming apparatus 10.

  In the data storage area 304 of the RAM 102, operation detection data 304a, print image data 304b, reference image data 304c, detection image data 304d, and the like are stored.

  The operation detection data 304a is operation input data including operation data or / and touch coordinate data detected according to the operation detection program 302a.

  As described above, the print image data 304b is image data read by the image reading unit 26 or image data input from an external computer.

  The reference image data 304c is image data corresponding to the reference image acquired according to the reference image acquisition program 302b. However, the reference image data 304 c is read from the memory 104 and developed (stored) in the RAM 102.

  The detection image data 304d is image data corresponding to the detection image acquired according to the detection image acquisition program 302c.

  Although not shown in the figure, the data storage area 304 is provided with a register for setting an imaging range of the detection image in the main scanning direction, or a register necessary for executing another control program. Other data necessary for the execution of the control program is stored.

  FIG. 8 is a flowchart showing an example of detection processing of the image forming apparatus 10. This detection process is executed when a print job is executed in the image forming apparatus 10. As shown in FIG. 8, when the detection process is started, the CPU 100 reads the reference image data 304c in step S1, and determines whether or not the sheet has reached the sheet detection unit 80 in step S3. Here, when the leading edge of the paper transported through the first paper transport path L 1 reaches the registration roller 68, it is determined that the paper has reached the paper detection unit 80. If “NO” in the step S3, that is, if the sheet has not reached the sheet detecting unit 80, the process returns to the step S3. On the other hand, if “YES” in the step S3, that is, if the paper reaches the paper detection unit 80, the line sensor 82 is driven in a step S5, and the detection image data 304d is obtained in a step S7. .

  Subsequently, in step S9, the reference image data 304c and the detection image data 304d are compared to detect an edge candidate position. In step S11, the reference image data 304c and the detection image data 304d are compared. It is determined whether the regularity of the reference pattern is interrupted on the side closer to the center line in the main scanning direction than the edge candidate position. If “NO” in the step S11, that is, if the regularity is not interrupted, a next edge candidate position is detected in a step S13, and the process returns to the step S11. On the other hand, if “YES” in the step S11, that is, if the regularity is interrupted, the edge candidate position is determined as the edge position in a step S15, and the detection process is ended.

  According to the first embodiment, by using the reference member 84 having a reference pattern including a plurality of color regions on the surface, a position where the regularity of the reference pattern is interrupted in the detection image is detected as an edge position. Therefore, even if an image is formed on the surface of the sheet facing the line sensor 82, the edge position can be detected with high accuracy.

  Further, according to the first embodiment, the size of the dark first region 840 in the main scanning direction is larger than the size of the light second region 842 in the main scanning direction. When there is a margin in the part, the edge position can be detected with high accuracy.

  Further, according to the first embodiment, the position of the image formed on the paper in the main scanning direction is adjusted according to the edge position, so that the positional deviation of the image formed on the paper can be prevented. it can.

  In the first embodiment, the reference image data 304c corresponding to the reference image is stored in the memory 104 in advance. However, the present invention is not limited to this. For example, instead of the reference image data 304c, a program in which information conditions such as position information and color information of each read pixel are written in a logical expression may be stored. For example, the program includes conditions such that the color of the nth read pixel from the read pixel serving as the reference in the main scanning direction is black, and the mth read pixel is white. In this case, the authenticity determination of each of the plurality of detection read pixels (detection read pixel data) may be performed according to the program, and the edge position may be detected according to the determination result. In this way, since it is not necessary to use the reference image data 304c, the memory 104 for storing the reference image data 304c can be omitted, or the storage capacity of the memory 104 can be reduced.

Further, when detecting the edge position, a plurality of (for example, four) detection images continuously captured when the paper is at the same position may be used. In this case, information obtained by averaging the color information is calculated in the detection read pixels included in the detection image data corresponding to each of the plurality of detection images. Specifically, in a certain reading pixel, information obtained by averaging the color information of the detection reading pixel data corresponding to the detection reading pixel at the same position as the reading pixel is calculated. The detection image data 304d includes averaged color information assigned to each read pixel. The edge position is detected according to the averaged color information. In this way, even if a sudden noise occurs in the detection image, the influence of the noise can be reduced. However, the number of detection images used (number of lines) can be changed as appropriate. By changing the number of lines, the processing time for averaging the color information for each read pixel can be adjusted.
[Second Embodiment]
The image forming apparatus 10 according to the second embodiment is the same as the first embodiment except that the edge position is detected using the corrected image data for detection obtained by correcting the data of the position corresponding to the deposit attached to the surface of the reference member 84. Since it is the same as the image forming apparatus 10 of the first embodiment, the contents different from those of the first embodiment will be described, and redundant description will be omitted.

  FIG. 9 is an illustrative view showing a method for detecting a deposit in the second embodiment. FIG. 10 is an illustrative view showing a method for detecting the edge position of the paper in the second embodiment.

  As shown in FIG. 9, deposits such as paper dust or dust may adhere to the surface of the reference member 84. In the second embodiment, in order to detect an adhering matter, an adhering matter detection image is captured when there is no paper passing through the paper detecting unit 80. For example, the deposit detection image is captured before the first sheet is transported when a print job is executed. In the second embodiment, when a deposit detection image is captured, all the light receiving elements 820 included in the line sensor 82 are driven and all the light sources included in the line sensor 82 are turned on. Therefore, the attached matter detection image includes the entire reference pattern of the reference member 84.

  When the attached matter detection image is captured, attached matter detection image data corresponding to the attached matter detection image is generated. The attached matter detection image data includes a plurality of attached matter detection pixel data, like the reference image data 304c and the detection image data 304d. Each of the plurality of attached matter detection pixel data includes light receiving element 820 information, position information, and color information. Then, the color information of the reference reading pixel data at the same position is compared with the color information of the attached matter detection pixel data, and a position where the reference image and the attached matter detection image have different colors is detected.

  In the example shown in FIG. 9, the color information differs between the reference image and the adhering matter detection image at positions corresponding to the third, fourth, sixth, and seventh reading pixels from the left. Thus, when there is a position where the color differs between the reference image and the attached matter detection image, it is determined that the attached matter is present on the surface of the reference member 84.

  Corrected image data is generated at positions where the color information differs between the reference image and the adhering matter detection image. The corrected image data is data obtained by copying the reference image data (reference read pixel data) at a position where the color information is different between the reference image and the attached matter detection image. However, the corrected image data does not include data corresponding to the position where the color information matches between the reference image and the adhering matter detection image.

  In the second embodiment, when a detection image is captured, corrected image data for detection in which the detection image data 304d is corrected is generated by the corrected image data. Here, the correction image data for detection is data obtained by replacing the detection image data 304d with the correction image data at a position where the correction image data exists. Specifically, the detection read pixel data at the same position is overwritten with the adhering matter detection pixel data corresponding to the position where the corrected image data exists.

  For example, as shown in FIG. 10, when there is an attachment at positions corresponding to the third, fourth, sixth, and seventh read pixels from the left, corrected image data is generated at the positions of these read pixels. Is done. With this corrected image data, the detection image data 304d is corrected, and detection corrected image data is generated. In the detection image data 304d, the third, fourth, sixth, and seventh read pixels from the left are white due to the influence of the attached matter. However, in the correction image data for detection, these read pixels are black. It is corrected to.

  Then, the corrected image data for detection and the reference image data 304c are compared, and the edge position of the paper is detected by the same method as in the first embodiment.

  Hereinafter, the detection process of the image forming apparatus 10 in the second embodiment will be described with reference to a flowchart. The same processes as the detection process described in the first embodiment are denoted by the same reference numerals, and the duplicated contents are described. Will be omitted or briefly described.

  FIG. 11 is a flowchart showing an example of detection processing in the second embodiment. As shown in FIG. 11, when the CPU 100 starts the detection process, the CPU 100 reads the reference image data 304c in step S1, drives the line sensor 82 in step S31, and loads the detected object image data in step S33. get. Subsequently, in step S35, it is determined whether or not there is a deposit. Here, the color information of the reference read pixel data at the same position is compared with the color information of the attached matter detection pixel data, and it is determined whether there is a position where the reference image and the attached matter detected image have different colors.

  If “NO” in the step S35, that is, if there is no deposit, the process proceeds to a step S3. On the other hand, if “YES” in the step S35, that is, if there is a deposit, corrected image data is generated in a step S37, and the process proceeds to the step S3.

  If the detection image data 304d is acquired in step S7, it is determined in step S39 whether or not correction image data exists. If “NO” in the step S39, that is, if there is no corrected image data, the process proceeds to the step S9 without correcting the detection image data 304d. On the other hand, if “YES” in the step S39, that is, if the corrected image data exists, the corrected image data for detection is generated in a step S41, and the process proceeds to the step S9.

  Note that the contents of the processing from step S3 to step S7 and step S9 and subsequent steps are the same as those in the first embodiment, and thus the description thereof is omitted.

  According to the second embodiment, since the edge position is detected using the correction image data for detection obtained by correcting the position data corresponding to the deposit attached to the surface of the reference member 84, the influence of the deposit is reduced. be able to.

In addition, when it is determined that the deposit is present on the surface of the reference member 84, the user or the service person may be notified that the deposit is present on the surface of the reference member 84. For example, when the image forming apparatus 10 includes a display, a message indicating that the deposit is present on the surface of the reference member 84 may be displayed on the display. In this case, the message indicating that the deposit is present on the surface of the reference member 84 may be displayed only during maintenance of the image forming apparatus 10.
[Third embodiment]
The image forming apparatus 10 according to the third embodiment is the same as the image forming apparatus 10 according to the first embodiment except that the reference pattern of the reference member 84 is changed. The description will be omitted.

  FIG. 12 is an illustrative view showing a reference pattern of the reference member 84 in the third embodiment. As shown in FIG. 12, in the reference pattern of the reference member 84 of the third embodiment, the size of each of the plurality of first regions 840 in the main scanning direction depends on the position of the first region 840 in the main scanning direction. Changed.

  Specifically, the size of the first region 840 arranged at an assumed position where the end of the sheet used in the image forming apparatus 10 in the main scanning direction is assumed to be large is set. The For example, the size in the main scanning direction of the first region 840 arranged at the assumed position may be set larger than the range of variation in the main scanning direction when the paper is conveyed, and can be changed as appropriate. The first region 840 arranged at the assumed position is arranged such that the center position in the main scanning direction matches the assumed position. In this way, when the paper is transported, the edge position of the paper passes over the first region 840 even if the position of the paper in the main scanning direction is slightly shifted.

  On the other hand, the size of the first region 840 arranged at a position other than the assumed position is set to be smaller than the size of the first region 840 arranged at the assumed position in the main scanning direction.

  For example, the size of the first region 840 arranged at the assumed position in the main scanning direction is set to the size of 5 pixels of the read pixels. In addition, the size of the first region 840 arranged at a position other than the assumed position is set to the size of one pixel in the main scanning direction.

  In the range shown in FIG. 12, the first region 840 having a large size in the main scanning direction is arranged at the assumed position of A4 size and the assumed position of letter size. Further, first regions 840 having a small size in the main scanning direction are arranged at positions other than the assumed position of A4 size and the assumed position of letter size. Although illustration is omitted, the first region 840 having a large size in the main scanning direction is also arranged at an assumed position of a paper size other than the above.

According to the third embodiment, in the reference pattern of the reference member 84, the first region 840 is arranged at an assumed position where the end of the sheet used in the image forming apparatus 10 in the main scanning direction is assumed to pass. Therefore, when there is a margin at the end of the paper in the main scanning direction, the edge position detection accuracy can be increased.
[Fourth embodiment]
The image forming apparatus 10 according to the fourth embodiment forms the image according to the first embodiment except that the brightness level is set for each of the plurality of read pixels included in the reference image data 304c and the detection image data 304d. Since it is the same as the apparatus 10, the contents different from the first embodiment will be described, and redundant description will be omitted.

  FIG. 13 is an illustrative view showing a method of detecting an edge position in the fourth embodiment. As shown in FIG. 13, a lightness level corresponding to the lightness is set for each of the plurality of read pixels included in the reference image data 304c and the detection image data 304d. For example, the lightness level is represented by a numerical value in 101 steps, where black (the darkest color) is “0” and white (lightest color) is “100”. In the fourth embodiment, information indicating a lightness level is used as color information set for each read pixel instead of information indicating black or white.

  Further, the brightness level range of the read pixel is set for each of the color of the first area 840 and the color of the second area 842 of the reference pattern included in the reference image data 304c. For example, the brightness level range of the read pixel corresponding to the first area 840 of the reference pattern included in the reference image data 304c is “0 to 30”. The brightness level of the read pixel corresponding to the second area 842 of the reference pattern included in the reference image data 304c is “70 to 100”.

  Therefore, when the lightness level of a certain detection read pixel included in the detection image is a lightness level other than “0-30” or “70-100”, the color of the detection read pixel is the reference member 84. It is determined that the color is not the color used for the reference pattern. That is, it is determined that the color is different from the color included in the reference pattern. It is determined that the color of the reference read pixel is different from the color of the detection read pixel at the position of the detection read pixel having a color different from the color used for the reference pattern. Note that the range of the brightness level of the read pixel in each of the first area 840 and the second area 842 of the reference pattern included in the reference image data 304c is not limited to the above-described example, and can be changed as appropriate. Further, instead of the lightness level range, threshold values corresponding to the colors of the first region 840 and the color of the second region 842 may be used.

  In the fourth embodiment, the position of the outermost reading pixel in the main scanning direction among the reading pixels (detection reading pixels) of a color different from the color used for the reference pattern is determined as the edge position. For example, in the example shown in FIG. 13, the position of the eighth read pixel from the left is determined as the edge position.

  In the fourth embodiment, a brightness level is set for each of the plurality of read pixels included in the reference image data 304c and the detection image data 304d, and the read pixels having a color different from the color used for the reference pattern are set. The edge position is detected accordingly. In this way, even when paper other than white is used, the edge position detection accuracy can be increased.

  Note that the modifications shown in the third and fourth embodiments can be applied to the image forming apparatus 10 of the second embodiment. Further, the modification shown in the fourth embodiment can also be applied to the image forming apparatus 10 of the third embodiment.

  In addition, the specific numerical values, configurations, and the like given in the above-described embodiments are examples, and can be appropriately changed according to the actual product.

DESCRIPTION OF SYMBOLS 10 ... Image forming apparatus 14 ... Image reading apparatus 30 ... Image reading part 80 ... Paper detection part 82 ... Line sensor 84 ... Reference | standard member 100 ... CPU
102 ... RAM

Claims (11)

An image forming unit that includes a sheet conveyance path and forms an image on a sheet conveyed through the sheet conveyance path;
A line sensor provided in the paper transport path so as to extend in the width direction of the paper;
A reference pattern is formed at a position facing the line sensor across the paper conveyance path, and a dark color first area and a light color second area are regularly arranged on a surface facing the line sensor. A position where the regularity of the reference pattern is interrupted in the detection image including a part of the sheet conveyed on the sheet conveyance path imaged by the line sensor and a part of the reference pattern. An image forming apparatus comprising detection means for detecting the position of an end in the width direction of a sheet.   The detection means is a candidate position detection means for detecting a candidate position that is a candidate for the position of the edge in the width direction of the paper based on the detection image, and an inner side in the width direction of the paper than the candidate position. 2. The image forming apparatus according to claim 1, further comprising: a determination unit that determines the candidate position as the position of the edge in the width direction of the paper based on whether the regularity of the reference pattern is interrupted.   The image forming apparatus according to claim 1, wherein a size of the first region in the width direction of the paper is larger than a size of the second region in the paper width direction. Storage means for storing a reference image including the reference pattern;
The said detection means compares the said reference image with the said image for a detection, and detects the position where the regularity of the said reference pattern interrupted in the said image for a detection. Image forming apparatus.   The image forming apparatus according to claim 4, wherein the storage unit is a nonvolatile memory. The storage means stores the brightness of the first area and the brightness of the second area included in the reference image,
The detecting means detects the edge of the width direction of the paper according to the brightness of the first area and the brightness of the second area included in the reference image, and the brightness of each reading pixel of the detection image. The image forming apparatus according to claim 4, wherein the position is detected. An adhering matter detecting means for detecting the position of the adhering matter adhering to the reference member; and a correcting means for correcting the detection image according to the position of the adhering matter detected by the attached matter detecting means,
The detection unit detects a position of an end portion in a width direction of a sheet conveyed on the sheet conveyance path according to a reference image including the reference pattern and the detection image corrected by the correction unit. The image forming apparatus according to claim 4.   The image forming apparatus according to claim 1, wherein the first area is disposed at an assumed position where an end portion in a main scanning direction of a sheet used in the image forming apparatus is assumed to pass.   9. The apparatus according to claim 1, further comprising an adjusting unit configured to adjust a position in the width direction of the sheet of an image formed on the sheet according to the position of the end in the width direction of the sheet detected by the detecting unit. The image forming apparatus according to any one of the above. An image forming unit that includes a sheet conveyance path and forms an image on a sheet conveyed through the sheet conveyance path, a line sensor provided in the sheet conveyance path so as to extend in the width direction of the sheet, and facing the line sensor A control program for an image forming apparatus, comprising: a reference member on which a reference pattern in which a dark first region and a light second region are regularly arranged on a surface to be formed is formed;
A processor of the image forming apparatus;
In a detection image including a part of a sheet conveyed through the sheet conveyance path and a part of the reference pattern captured by the line sensor, a position where the regularity of the reference pattern is interrupted is determined in the width direction of the sheet. A control program for an image forming apparatus that functions as a detection unit that detects the position of an end. An image forming unit that includes a sheet conveyance path and forms an image on a sheet conveyed through the sheet conveyance path, a line sensor provided in the sheet conveyance path so as to extend in the width direction of the sheet, and facing the line sensor A processor of an image forming apparatus including a reference member on which a reference pattern in which a dark first region and a light second region are regularly arranged is formed on a surface to be processed;
(A) In a detection image including a part of a sheet conveyed through the sheet conveyance path and a part of the reference pattern imaged by the line sensor, a position where the regularity of the reference pattern is interrupted is A control method that executes a step of detecting the position of the end portion in the width direction.

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