JP2019098734A - Image forming apparatus and image forming method - Google Patents

Abstract

To adjust the image position in a print accurately.SOLUTION: An image forming method includes: forming an image on a recording medium; scanning the recording medium having a position detection mark on the recording medium as the image to generate a scanned image; calculating a plurality of correction values to adjust a position of the image to be formed on the recording medium, based on the scanned image; calculating a first correction value of the plurality of correction values, based on a scanned image generated from a first face of the recording medium; calculating a second correction value, based on a second scanned image generated from a second face of the recording medium; and calculating a third correction value to adjust a position of an image to be formed on the second face of the recording medium, based on the scanned image generated from the first face of the recording medium on which the position detection mark is formed using the first correction value.SELECTED DRAWING: Figure 3

Description

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

  Conventionally, the position adjustment of an image in a printed matter has been performed by a person with high specialized skills, but in recent years, an apparatus for adjusting the position of the image as a post-process of printing is used. In such an image position adjusting device, the printed matter is read by an external scanner, the adjustment value of the image position is acquired based on the read image, and the image position in the printed matter is adjusted (see, for example, Patent Document 1).

  However, in the conventional image position adjusting apparatus, the shape of the recording medium used for printing can not be accurately grasped depending on the fixing process after image formation, the cutting shape of the recording medium, and the like. Therefore, even if the image position is adjusted on the first surface side (front surface) and the second surface side (back surface), relative to the first surface side, the image printed on the second surface side is relative to the first surface side. Misalignment occurs.

  The present invention has been made to solve such problems, and it is an object of the present invention to accurately adjust the position of an image in a printed matter.

  In order to solve the above problems, one aspect of the present invention is an image forming apparatus that forms an image on a recording medium by adjusting the position of the image, and an image forming unit that forms the image on the recording medium; A reading unit that reads a recording medium on which a position detection mark is formed as the image and generates a read image, and a correction value for adjusting the position of the image formed on the recording medium based on the read image A correction value calculation unit to calculate, the correction value calculation unit calculates a first correction value based on the read image of the first surface of the recording medium, and the read image of the second surface of the recording medium The second correction value is calculated based on the second correction value, and the second correction value is formed on the second surface of the recording medium based on the read image of the first surface of the recording medium on which the position detection mark is formed. Third correction value to adjust the position of the image Characterized in that it.

  According to the present invention, adjustment of the image position in the printed matter can be performed with high accuracy.

FIG. 1 is a diagram showing an entire configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 1 is a block diagram showing a hardware configuration of an image position detection device according to an embodiment of the present invention. 1 is a block diagram showing functional configurations of a control device, a print engine, and an image position detection device according to an embodiment of the present invention. FIG. 2 is a block diagram showing the configuration of a job information processing unit according to the embodiment of the present invention. FIG. 1 is a view showing a mechanical configuration of an image forming apparatus according to an embodiment of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS The figure which shows the principal part of the image position detection apparatus which concerns on embodiment of this invention. The perspective view of the opposing member which concerns on embodiment of this invention. The enlarged view of the perspective cut surface of the opposing member which concerns on embodiment of this invention. FIG. 5 is a transport route diagram of a recording medium at the time of printing of the first surface according to the embodiment of the present invention. FIG. 7 is a view showing a reading mode of the position detection mark printed on the first surface according to the embodiment of the present invention. FIG. 7 is a transport route diagram of a recording medium at the time of printing of the second surface according to the embodiment of the present invention. FIG. 7 is a view showing a reading mode of the position detection mark printed on the second surface according to the embodiment of the present invention. The figure which illustrated the composition of the position detection mark concerning the embodiment of the present invention. FIG. 7 is a view showing an aspect of calculating a correction value for adjusting the position of an image according to the embodiment of the present invention. FIG. 7 is a view showing an aspect of calculating a correction value for adjusting the position of an image according to the embodiment of the present invention. FIG. 7 is a view showing an aspect of calculating a correction value for adjusting the position of an image according to the embodiment of the present invention. FIG. 7 is a view showing an aspect of calculating a correction value for adjusting the position of an image according to the embodiment of the present invention. FIG. 7 is a view showing an aspect of calculating a correction value for adjusting the position of an image according to the embodiment of the present invention. FIG. 7 is a view showing an aspect of calculating a correction value for adjusting the position of an image according to the embodiment of the present invention. FIG. 7 is a view showing an aspect of calculating a correction value for adjusting the position of an image according to the embodiment of the present invention. 5 is a flowchart showing a flow of processing of calculating a correction value for adjusting the position of an image according to the embodiment of the present invention. 5 is a flowchart showing a flow of processing for determining a correction value used in image formation according to the embodiment of the present invention. The figure which illustrated the chart for confirmation concerning the embodiment of the present invention. The figure which shows the aspect of the offset process which concerns on embodiment of this invention. The figure which shows the aspect of the magnification process which concerns on embodiment of this invention. The figure which shows the aspect of the skew correction processing which concerns on embodiment of this invention. FIG. 6 is a view showing another configuration of the image forming apparatus according to the embodiment of the present invention. 5 is a flowchart showing a flow of processing of adjusting the position of an image according to the embodiment of the present invention. 5 is a flowchart showing a flow of processing of adjusting the position of an image according to the embodiment of the present invention. 5 is a flowchart showing a flow of processing of adjusting the position of an image according to the embodiment of the present invention. The figure which illustrated the shape of the printing paper concerning the embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the present embodiment, based on the read image obtained by reading the position detection mark for detecting the position of the image formed on the recording medium, the image is output to the target position on the recording medium. An image forming apparatus including an image position detection device for adjusting the position of an image will be described. FIG. 1 is a diagram showing an entire configuration of an image forming apparatus 5 according to the present embodiment.

  As shown in FIG. 1, the image forming apparatus 5 according to the present embodiment includes a control device 1000, a print engine 300, and an image position detection device 400. The control device 1000 generates image data to be printed out based on the print job received by the image forming device 5, that is, bitmap data which is an output target image, and controls the print engine 300 based on the generated bitmap data. And execute image formation output.

  The print engine 300 is an image forming unit that executes image formation output on a recording medium such as the printing paper M based on bitmap data under the control of the control device 1000. The image position detection apparatus 400 reads the position detection mark printed on the printing paper M, and corrects the bitmap data to be output to the target position on the printing paper M based on the read image. Calculate the correction value of

  The correction value calculated by the image position detection device 400 is transmitted to the control device 1000, and is used as a correction value for generating the bitmap data and a correction value for transporting the printing paper M to the print engine 300. Used.

  The image position detection apparatus 400 according to the present embodiment calculates a correction value based on the coordinates of the end portion of the printing paper M and the center coordinates of the position detection mark on the printing paper M in the read image described above. Depending on the cut shape and thickness of the printing paper M, the coordinates of the edge of the printing paper M and the positional deviation of the image printed on the printing paper M may be generated. It is a gist according to the present embodiment to calculate the correction value. Details will be described later.

  Here, a hardware configuration that constitutes functional blocks of the control device 1000, the print engine 300, and the image position detection device 400 according to the present embodiment will be described with reference to FIG. FIG. 2 is a block diagram showing the hardware configuration of the image position detection apparatus 400 according to the present embodiment. Although FIG. 2 shows the hardware configuration of the image position detection apparatus 400, the hardware configurations of the control device 1000 and the print engine 300 are also configured similarly to the image position detection apparatus 400.

  As shown in FIG. 2, the image position detection apparatus 400 according to the present embodiment has the same configuration as an information processing apparatus such as a general PC (Personal Computer) or a server. That is, the image position detection apparatus 400 according to the present embodiment includes a central processing unit (CPU) 10, a random access memory (RAM) 20, a read only memory (ROM) 30, a hard disk drive (HDD) 40 and an I / F 50. It is connected via a bus 90. Further, an LCD (Liquid Crystal Display) 60, an operation unit 70, and a dedicated device 80 may be connected to the I / F 50.

  The CPU 10 is an arithmetic unit, and controls the overall operation of the image position detection apparatus 400. The RAM 20 is a volatile storage medium capable of high-speed reading and writing of information, and is used as a work area when the CPU 10 processes information. The ROM 30 is a read only non-volatile storage medium, and stores programs such as firmware. The HDD 40 is a non-volatile storage medium capable of reading and writing information, and stores an operating system (OS), various control programs, application programs, and the like.

  The I / F 50 connects and controls the bus 90 and various hardware and networks. The LCD 60 is, for example, a visual user interface for the user to confirm the operation state of the image forming apparatus 5 via the control device 1000. The operation unit 70 is a user interface for a user such as a keyboard and a mouse to input information to the control device 1000.

  The dedicated device 80 is hardware for realizing a dedicated function in the control device 1000, the print engine 300 and the image position detection device 400. In the case of the print engine 300, the dedicated device 80 transports a sheet for image formation output It is a mechanism or plotter that executes image formation output on a sheet of paper.

  Also, in the case of the control device 1000 and the image position detection device 400, it is a dedicated calculation device for performing image processing at high speed. Such an arithmetic unit is configured, for example, as an application specific integrated circuit (ASIC). Also included is a reading device such as a sensor for reading an image output on a sheet of paper.

  In such a hardware configuration, a program stored in the ROM 30, the HDD 40, or a recording medium such as an optical disk is read out to the RAM 20, and the CPU 10 performs an operation according to the programs to configure a software control unit. A combination of the software control unit configured as described above and hardware configures a functional block that implements the functions of the control device 1000, the print engine 300, and the image position detection device 400 according to the present embodiment.

  FIG. 3 is a block diagram showing functional configurations of the control device 1000, the print engine 300, and the image position detection device 400 according to the present embodiment. As shown in FIG. 3, the control device 1000 according to the present embodiment includes an image processing unit 100 and an engine controller 200. The print engine 300 also includes a print processing unit 310. Further, the image position detection apparatus 400 includes a reading unit 401, a sensor image acquisition unit 410, a correction value calculation unit 420, and a coordinate conversion unit 430.

  The image processing unit 100 includes a RIP processing unit 110 and a job information processing unit 120. As shown in FIG. 4, the job information processing unit 120 includes an offset processing unit 121, a magnification adjustment processing unit 122, and a skew correction processing unit 123. The offset processing unit 121, the magnification adjustment processing unit 122, and the skew correction processing unit 123 execute correction processing for correcting the position of the image formed on the printing paper M. Specific modes of the correction process will be described later.

  It controls execution of image formation output based on a print job input from the outside via a network or a print job generated from image data stored in the control apparatus 1000 by an operation of the operator. The RIP processing unit 110 generates bitmap data based on the image data included in the print job and transmits the generated bitmap data to the engine controller 200 when executing image formation output.

  When generating bitmap data, the RIP processing unit 110 generates bitmap data for the print engine 300 to execute image formation output based on the image data included in the print job. The bitmap data is information of each pixel constituting an image to be formed and output.

  The print engine 300 according to the present embodiment executes image formation output based on a binary image for each of CMYK (Cyan, Magenta, Yellow, Key plate). On the other hand, in general, image data included in a print job is a multi-valued image in which one pixel is expressed by multiple gradations such as 256 gradations. Therefore, the RIP processing unit 110 converts the image data included in the print job from a multi-value image to a low-value image, and generates binary bitmap data for each of CMYK.

  The data acquisition unit 210 acquires the print job and the bitmap data from the image processing unit 100, and operates the engine control unit 220. The engine control unit 220 causes the print engine 300 to execute image formation output based on the print job and the bitmap data transferred from the data acquisition unit 210. The engine control unit 220 also causes the reading unit 401 to execute a reading operation based on the print job transferred from the data acquisition unit 210.

  The print processing unit 310 is an image forming unit that acquires bitmap data input from the engine controller 200, performs image formation output on the printing paper M, and outputs the printing paper M on which an image is printed. The print processing unit 310 according to the present embodiment is realized by a general image forming mechanism of the electrophotographic method, but it is also possible to use another image forming mechanism such as an inkjet method.

  The reading unit 401 is configured by a line sensor or the like disposed in the conveyance path of the printing paper M inside the image position detection apparatus 400, and the reading unit 401 is based on control information such as a print job input from the engine control unit 220. Is scanned on the surface of the printing paper M being conveyed, and the position detection mark formed on the printing paper M is read.

  The read image is an image generated by the reading unit 401 reading the printing paper M on which the position detection mark is output, and thus is an image indicating an output result by the image forming apparatus 5. The sensor image acquisition unit 410 acquires a read image generated by reading the sheet of the printing paper M by the reading unit 401. The read image acquired by the sensor image acquisition unit 410 is input to the correction value calculation unit 420 and the coordinate conversion unit 430 together with the print job when the reading unit 401 generates the read image.

  The correction value calculation unit 420 sets the printing sheet M on the printing sheet M based on the center coordinates of the position detection mark 7 included in the read image acquired from the sensor image acquiring unit 410 and the coordinates of the end of the printing sheet M. A correction value for correcting the position of the formed image is calculated.

  The correction value calculation unit 420 sets the first correction value C1 of the first surface (front surface) of the print sheet M and the second surface of the print sheet M based on the read image and the information of the print job when the read image is generated. A correction value C2 for (rear surface) and a correction value C3 for the second surface (rear surface) of printing paper M for the second time are respectively calculated. The correction value C1 is a first correction value, the correction value C2 is a second correction value, and the correction value C3 is a third correction value.

  The correction value C1, the correction value C2, and the correction value C3 are sent to the job information processing unit 120 and the engine control unit 220, respectively, and the correction for correcting the position of the image formed on the printing paper M at the time of image formation output Used as a value. Specific modes of the correction process will be described later.

  The coordinate conversion unit 430 forms an image of the center coordinates of the position detection mark detected by reading the position detection mark formed on the first surface of the printing paper M and the coordinates of the end portion of the printing paper M with respect to the second surface. Transform to the coordinate system in the first plane when performing the output.

  The converted coordinate information is output to the correction value calculation unit 420, and is used to calculate the second correction value C3 of the second surface (rear surface) of the printing paper M. Specific modes of the coordinate conversion process will be described later. With such a functional configuration, in the image forming apparatus 5 according to the present embodiment, the process of correcting the position of the image formed on the printing paper M is executed.

  Next, the mechanical configuration of the print engine 300 and the image position detection apparatus 400 in the image forming apparatus 5 and the conveyance path R of the print sheet M will be described with reference to FIG. As shown in FIG. 5, the print processing unit 310 included in the print engine 300 according to this embodiment is a photosensitive belt 12Y, 12M, 12C, 12K of each color along the transport belt 11, which is an endless moving unit In general, the photosensitive drums 12 are arranged side by side, which is a so-called tandem type.

  That is, along the transport belt 11 which is an intermediate transfer belt on which an intermediate transfer image to be transferred to the printing paper M fed from the paper feed tray 13 is formed, from the upstream side in the transport direction of the transport belt 11 A plurality of photosensitive drums 12Y, 12M, 12C, and 12K are arranged.

  The image of each color developed with the toner as the colorant on the surface of the photosensitive drum 12 of each color is superimposed on the conveyance belt 11 and transferred to form a full-color image. The full-color image thus formed on the conveyance belt 11 is transferred onto the surface of the printing paper M by the function of the transfer roller 14 at the position closest to the paper conveyance path R shown by the broken line in FIG. Ru.

  The transfer roller 14 is configured by a pair of rollers 14 a and 14 b disposed so as to sandwich the transport belt 11. The roller 14 a disposed on the upper side of the conveyance belt 11 is a driven roller that rotates following the operation of the conveyance belt 11.

  On the other hand, the roller 14 b disposed below the conveyance belt 11 is a roller driven by the engine control unit 220 independently of the operation of the conveyance belt 11. Therefore, the engine control unit 220 functions as a speed control unit that controls the speed of the roller 14a.

  Therefore, at the timing when the image formed on the conveyance belt 11 is transferred onto the printing paper M, the conveyance is controlled by adjusting the rotational speed of the transfer roller 14, particularly the roller 14b disposed below the conveyance belt 11. The magnification of the image formed on the belt 11 in the sub-scanning direction is adjusted and transferred onto the printing paper M.

  The printing sheet M on which an image is formed on the sheet is further conveyed, and after the image is fixed by the fixing roller 15, the sheet is conveyed to the reading unit 401 before being conveyed out of the casing of the image forming apparatus 5. Further, in the case of double-sided printing, an image is formed on the first surface (on the front surface), and the fixed printing paper M is conveyed via the reverse path 16.

  In this manner, the printing paper M is in a state where image formation is possible on the second side (rear side), that is, the image formed on the transport belt 11 is transferred to the second side of the printing paper M. In the above state, the sheet is conveyed again to the transfer position of the transfer roller 14.

  The reading unit 401 reads each side of the printing paper M conveyed from the printing processing unit 310 in the conveyance path R of the printing paper M inside the image forming apparatus 5, generates a read image, and generates the inside of the image position detection apparatus 400. The information is output to a sensor image acquisition unit 410 configured by the information processing apparatus of In addition, the print sheet M read by the reading unit 401 is further conveyed inside the image forming apparatus 5 and discharged onto the sheet discharge tray 500. Specific modes for reading the first and second sides of the printing paper M will be described later.

  Next, the configuration of the image position detection apparatus 400 according to the present embodiment will be described with reference to FIGS. 6 to 8. FIG. 6 is a view showing the main part of the mechanical configuration of the image position detection apparatus 400, and FIGS. 7 and 8 are perspective views of the facing member 93. As shown in FIG.

  As shown in FIG. 5, the reading unit 401 is a downstream side of the fixing roller 15 in the conveyance direction of the printing sheet M, and the printing sheet M on which an image is formed is used as the housing of the image forming apparatus 5. The printing paper M is disposed on the upstream side in the conveyance direction of the printing paper M with respect to the branching portion 17 for discharging the printing paper M to the outside or conveying the printing paper M to the reverse path 16.

  The reading unit 401 optically reads an image such as a position detection mark formed on the printing paper M, and generates a read image. Then, the correction value calculation unit 420 calculates the correction value C1, the correction value C2, and the correction value C3 based on the generated read image. For this reason, in the image position detection apparatus 400 according to the present embodiment, the color of the facing member 93 and the gap between the contact glass 94 can be changed according to the paper thickness, color, etc. of the printing paper M. .

  As shown in FIG. 6, the image position detection device 400 includes an illumination light source 91, a reading unit 401, a facing member 93, a contact glass 94, and a support member 95.

  The illumination light source 91 is disposed on the side of the image forming surface on which the image is formed on the printing paper M conveyed. Then, light is applied to the reading position at which the image formed on the print sheet M is read in the transport path R of the portion of the transport path R of the print sheet M where the print sheet M passes the image position detection device 400. The reading position is a position at which the reading unit 401 can read the print sheet M on the conveyance path R.

  The reading unit 401 can use a reflection mirror, an imaging lens, an image sensor having an imaging device, a line sensor in which the imaging devices are arranged, or the like. Read the image formed on the forming surface. Further, when the print sheet M is not at the reading position, the reading unit 401 reads the outer peripheral surfaces 931 a, 932 a, 933 a, 934 a of the opposing member 93, the reference surface member of the opposing member 93, and the like. Then, the reading unit 401 generates a read image based on the amount of light received by the imaging device.

  The facing member 93 is disposed on the back side of the image forming surface on which the image is formed on the conveyed printing paper M. The opposing member 93 is configured such that the rollers 931, 932, 933, 934 are rotatably held by the roller bracket 935 as shown in FIGS. 7 and 8. The rollers 931, 932, 933, and 934 are rotatable members having outer peripheral surfaces 931a, 932a, 933a, and 934a, which are convexly curved reference surfaces, and rotate independently of the roller bracket 935. .

  The roller bracket 935 is fastened to the roller bracket shaft 936. When the roller bracket shaft 936 rotates, the roller bracket 935 rotates while holding the rollers 931, 932, 933, and 934. In this manner, the outer peripheral surfaces 931a, 932a, 933a, 934a selectively switch the rollers 931, 932, 933, 934 so that the predetermined reading facing the contact glass 94 with a gap through which the printing paper M can pass. Placed in position.

  The reading position is set, for example, at a position closest to the contact glass 94 on the outer peripheral surface of the roller disposed facing the contact glass 94 among the outer peripheral surfaces 931a, 932a, 933a, and 934a. Further, the reading position is, for example, from the position closest to the contact glass 94 on the outer peripheral surface of the roller disposed facing the contact glass 94 to the position corresponding to the thickness of the printing paper M close to the contact glass 94 side. May be set.

  The contact glass 94 is made of a light transmitting member, and is conveyed to the reading position and disposed at a position facing the image forming surface of the printing paper M.

  The support member 95 is a member to which the illumination light source 91 and the reading unit 401 are fixed. The path of the portion of the transport path R of the printing sheet M through which the printing sheet M passes the reading unit 401 is separated from the upstream portion and the downstream transport path R and supported by the support member 95. The conveyance roller 96 and the conveyance roller 97 are disposed in the upstream portion and the downstream portion of the conveyance route R other than the passage of the printing paper M through the reading unit 401.

  Then, when the printing paper M is conveyed, the reading unit 401 reads the image forming surface from the arrow 940 side through the contact glass 94. The outer peripheral surface 931 a of the roller 931 is disposed at a position facing the contact glass 94, and rotates in conjunction with the conveyance of the printing paper M. As described above, the roller 931 has a function of transporting the print sheet M, and even if the gap is such a narrow gap that the print sheet M does not move, jamming or the like is less likely to occur.

  The rollers 931, 932, 933, 934 are rollers different in color and / or diameter, respectively. For example, the roller 931 is black and normal diameter, the roller 932 is white and small diameter, the roller 933 is white and normal diameter, and the roller 934 is black and small diameter.

  Therefore, by switching the rollers in accordance with the color of the printing paper M, the boundary between the printing paper M and the rollers can be easily recognized in the read image. Further, the diameter of the roller can be changed by switching the roller depending on the thickness of the printing paper M and whether it is used at the time of shading operation. Furthermore, the size of the gap between the printing paper M and the opposing member 93 can be changed by switching the rollers.

  Furthermore, drive means may be provided to rotationally drive the rollers 931, 932, 933, 934. In this case, even if the gap between the contact glass 94 and the roller disposed opposite to the contact glass 94 among the rollers 931, 932, 933, and 934 becomes narrower, the recording material P Can be transported.

  FIG. 7 is a perspective view of the facing member 93 capable of rotationally driving the rollers 931, 932, 933, 934. FIG. 8 is an enlarged perspective cross-sectional view of the opposing member 93 of FIG.

  Roller gears 931b, 932b, 933b, and 934b are disposed on the rollers 931, 932, 933, and 934, respectively, and a roller drive gear 937a sharing the center of rotation with the roller bracket 935 is drivingly connected.

  As a result, as the roller drive gear 937a rotates, the rollers 931, 932, 933, 934 are rotationally driven via the roller gears 931b, 932b, 933b, 934b. A roller drive pulley 937 b is integrally formed with the roller drive gear 937 a and is drivingly connected by a pulley for driving the transport rollers 96 and 97 and a drive belt. The drive system has a function as a rotational drive unit that rotationally drives the rollers 931, 932, 933, 934.

  Then, when the drive pulley rotates, the pulley for driving the transport rollers 96 and 97 and the roller drive pulley 937b are simultaneously rotated via the drive belt. Thus, the rollers 931, 932, 933, 934 are rotationally driven via the roller drive gear 937a and the roller gears 931b, 932b, 933b, 934b at the same time as the transport rollers 96, 97 are rotationally driven. At this time, the surface of the roller 931 disposed at the position facing the contact glass 94 moves in the same direction as the direction in which the printing paper M is conveyed.

  The engine control unit 220 selectively connects the four rollers 931, 932, 933, 934, the reference surface members 991, 992, 993 or the guide member 994 and places them in the reading position. Control the rotational drive position.

  Next, the conveyance path R of the printing paper M at the time of printing of the first side will be described with reference to FIG. FIG. 9 is a view showing a conveyance path R of the printing paper M at the time of printing on the first surface according to the present embodiment.

  At the time of image formation on the first side, the printing paper M is conveyed on the conveyance path R from the paper feed tray 13 toward the conveyance belt 11 in accordance with a path indicated by an arrow in FIG. Then, the image formed on the conveyance belt 11 is transferred to the first surface (front surface) of the printing paper M by the function of the transfer roller 14.

  The image is fixed by the fixing roller 15 on the printing paper M on which the image has been transferred. The fixing roller 15 fixes the image on the print sheet M by heating or pressing the print sheet M.

  When the image is fixed, the printing paper M is conveyed to the reading unit 401, and as shown in FIG. 10, the image G1 formed on the first surface of the printing paper M is read. After passing through the reading unit 401, the print sheet M is conveyed to the reverse path 16.

  Next, the conveyance path R of the printing paper M at the time of printing on the second side will be described with reference to FIG. FIG. 11 is a diagram showing a transport path of the printing sheet M at the time of printing on the second surface according to the present embodiment.

  At the time of image formation on the second surface, the printing paper M is transported on the transport path R from the reverse path 16 toward the transport belt 11 according to the path shown by the arrow in FIG. Then, the image formed on the conveyance belt 11 is transferred to the second surface (back surface) of the printing paper M by the function of the transfer roller 14.

  The image is fixed by the fixing roller 15 on the printing paper M on which the image has been transferred. When the image is fixed, the print sheet M is conveyed to the reading unit 401, and as shown in FIG. 12, the image G2 formed on the second surface of the print sheet M is read. After passing through the reading unit 401, the print sheet M is conveyed toward the discharge tray 500.

  As described above, the image forming apparatus 5 according to the present embodiment has the printing paper M outside the apparatus even when double-sided printing is performed by providing the reading unit 401 between the fixing roller 15 and the branch unit 17. The image formed on the printing paper M can be read on both sides without being taken out.

  Next, in order to detect the position of the image formed on the printing paper M, the position detection mark 7 formed on the printing paper M will be described with reference to FIG. FIG. 13 is a diagram illustrating the configuration of the position detection mark 7 according to the present embodiment. In the present embodiment, the position detection mark 7 is formed on the center side of the printing paper M at a position separated from the edge of the printing paper M by a predetermined distance D.

  Specifically, the position detection marks 7a, 7b, 7c and 7d are formed apart from the end portions of the printing paper M in the main scanning direction and the sub scanning direction by the distance D, respectively. Then, the respective position detection marks 7 can be read to obtain the coordinates of the position coordinates 8a, 8b, 8c, 8d. The position coordinates 8 correspond to the center coordinates of the position detection mark 7.

  The correction value calculation unit 420 and the coordinate conversion unit 430 correct the position of the image formed on the printing paper M based on the coordinates of the position coordinates 8a, 8b, 8c, 8d and the coordinates of the four corners of the printing paper M Execute the process to

  Next, how to calculate the correction value for correcting the position of the image formed on the printing paper M will be described with reference to FIGS. 14 to 16. FIGS. 14 to 16 are diagrams showing an aspect of calculating the correction value C1 and the correction value C2 for adjusting the position of the image formed on the printing paper M according to the present embodiment.

  The correction value C1 is a correction value for adjusting the position of the image formed on the printing paper M on the first side, and the correction value C2 is a printing paper M on the second side (the back side of the first side) It is a correction value for adjusting the position of the image formed on. Further, since the correction value C1 and the correction value C2 are calculated in the same manner, in the description of FIG. 14 to FIG. 16, only the manner of calculation of the correction value C1 will be described, and redundant description will be omitted.

  The reading result of the printing paper M by the reading unit 401 is transmitted to the sensor image acquisition unit 410, and the sensor image acquisition unit 410 acquires a read image including the position detection marks 7a, 7b, 7c, and 7d. The correction value calculation unit 420 acquires a read image from the sensor image acquisition unit 410, and acquires coordinates of position coordinates 8a, 8b, 8c, 8d on the printing paper M and coordinates of an end of the printing paper M.

  FIG. 14 is a diagram showing P1, P2, P3 and P4 which are coordinates of position coordinates 8a, 8b, 8c and 8d on the printing paper M. Position detection mark 7a, P1 to P4, are respectively based on P1 for position coordinate 8a, P2 for position coordinate 8b, P3 for position coordinate 8c, P4 for position coordinate 8d and the coordinates of the end portion of printing paper M. The coordinates 7b, 7c, and 7d indicate coordinates on which position of the printing paper M, respectively.

  Depending on the operation state of the image forming apparatus 5 and the cut shape of the printing paper M, position coordinates 8a, 8b, 8c, 8d on the printing paper M should be originally formed on the printing paper M, as shown in FIG. It may be different from the ideal positions P1 ', P2', P3 'and P4'. Here, the ideal position to be originally formed on the printing paper M is a position determined based on the information for setting the margin from the end of the printing paper M in the print job.

  The correction value calculation unit 420 moves the position coordinates 8a, 8b, 8c and 8d respectively when moved from P1 to P1 ′, from P2 to P2 ′, from P3 to P3 ′, and from P4 to P4 ′. Is calculated as the correction value C1. The correction value calculation unit 420 also calculates the correction value C2 in the same manner as the correction value C1.

  FIG. 16 is a diagram showing P1 ′, P2 ′, P3 ′ and P4 ′ which are coordinates obtained by moving P1, P2, P3 and P4 in FIG. 14 by the correction value C1. By applying the calculated correction value C1 to P1, P2, P3, and P4 in FIG. 14, it is possible to obtain an image corrected to the ideal positions P1 ′, P2 ′, P3 ′, and P4 ′.

  Next, how to calculate the correction value for correcting the relative position of the image formed on both sides of the printing paper M will be described with reference to FIGS. FIGS. 17 to 20 show how to calculate the correction value C3 for adjusting the position of the image formed on the printing paper M according to the present embodiment.

  The correction value C3 is based on the reading result of the position detection mark 7 on the first surface, with the position of the image formed on the second surface corrected as the ideal position at the time of image formation by reflecting the correction value C2. It is a correction value for adjusting the position to correspond to the position coordinates 8a, 8b, 8c, 8d.

  Therefore, when the coordinate conversion unit 430 calculates the correction value C3, the position detection mark 7a formed on the first surface is as seen when the printing sheet M is seen through the printing sheet M and the first surface is viewed from the second surface side. , 7b, 7c, 7d and the coordinates on the second surface of the position coordinates 8a, 8b, 8c, 8d.

  FIG. 17 is a diagram showing P1, P2, P3 and P4 which are coordinates of position coordinates 8a, 8b, 8c and 8d on the printing paper M on the first surface. In the calculation of the correction value C3, as described above, the position coordinates 8a of the first surface on which the correction value C1 is reflected, as when the printing paper M is seen through the printing sheet M and the first surface is viewed from the second surface side. A process of converting the coordinates (P1, P2, P3, P4) of 8b, 8c, 8d into a position on the second surface is performed. The correction value C3 is the coordinates of the position coordinates 8a, 8b, 8c, 8d of the first surface determined based on the reading result of the position detection mark 7 formed on the first surface with the correction value C1 reflected. It is calculated based on P1, P2, P3 and P4).

  FIG. 18 is a diagram showing P1, P2, P3 and P4 after coordinate conversion. The coordinate conversion unit 430 is configured such that P1, P2, P3, and P4 in FIG. 17 are at positions inverted in the main scanning direction of the printing paper M, that is, in the direction orthogonal to the conveyance direction X of the printing paper M. , P2, P3 and P4 coordinates are converted.

  Then, the correction value calculation unit 420 calculates the correction value C3 for adjusting the position of the image formed on the second surface after the correction value C2 is applied. The correction value calculation unit 420, as shown in FIG. 19, positions P1 ′, P2 ′, P3 ′, and P4 ′ of the image formed on the second surface after the correction value C2 is applied is P3, respectively. A correction value C3 for adjusting the position of the image is calculated to correspond to P4, P1 and P2.

  That is, the correction value calculation unit 420 corrects the movement amount when the image position P1 'to P3 on the second surface, P2' to P4, P3 'to P1, and P4' to P2 are moved from the position P1 'to P3. Calculated as

  FIG. 20 is a diagram showing P1 ′ ′, P2 ′ ′, P3 ′ ′, P4 ′ ′ which are coordinates obtained by moving P1 ′, P2 ′, P3 ′, P4 ′ of FIG. 19 by the correction value C3. An image corrected to the ideal positions P1 ′ ′, P2 ′ ′, P3 ′ ′, P4 ′ ′ by applying the calculated correction value C3 to P1 ′, P2 ′, P3 ′, P4 ′ in FIG. You can get

  Next, the flow of the process of calculating the correction value for correcting the position of the image formed on the printing paper M according to the present embodiment will be described with reference to FIG. FIG. 21 is a flowchart showing a flow of processing for calculating a correction value for correcting the position of the image formed on the printing paper M according to the present embodiment.

  In the present embodiment, first, the user of the image forming apparatus 5 performs an operation to execute the operation mode for correcting the position of the image formed on the printing paper M, and the printing paper M is sent to the control device 1000. A job for executing an operation mode (image position adjustment mode) for correcting the position of the formed image is input. That is, the control device 1000 treats the image position adjustment mode as one of print jobs.

  When a print job for executing the image position adjustment mode is input to the control device 1000, the job information processing unit 120 causes the RIP processing unit 110 to generate bitmap data for forming the position detection mark 7 on the printing paper M. . The engine control unit 220 receives bit map data including the position detection mark 7 via the data acquisition unit 210, inputs the bit map data to the print processing unit 310, and executes image formation of the position detection mark 7 on the printing paper M (S2101).

  When the position detection mark 7 is formed, the engine control unit 220 conveys the print sheet M to the reading unit 401 so that the surface on which the position detection mark 7 is formed can be read by the reading unit 401. The reading unit 401 scans the printing paper M to generate a read image, and the sensor image acquisition unit 410 acquires a read image including the position detection mark 7 (S2102). Note that the read image generated in step S2102 is used as a read image of the printing paper M on the first side.

  The correction value calculation unit 420 calculates the correction value C1 as described above based on the coordinates of the position detection mark 7 included in the read image of the first surface and the coordinates of the end portion of the printing paper M (S2103).

  At this time, the read image of the printing paper M is acquired by an arbitrary number of sheets for the correction value C1, and the correction values calculated based on the coordinates of the position detection mark 7 and the coordinates of the end of the printing paper M are averaged. It is also good. In the case of averaging, the operations of S2101 to S2103 are repeatedly executed until the correction value C1 in the read image of the print sheet M for an arbitrary number of sheets is obtained, and the correction value calculation unit 420 calculates the average value of the obtained correction values C1. Is calculated (S2104). When the correction values C1 are not averaged by a plurality of read images, the process of S2104 is omitted.

  In the image forming apparatus 5, a limit correction value which is a range of correction values for adjusting the position of the image at the time of image formation is defined. The limit correction value is a correction value in which the upper limit value and the lower limit value are determined, and the correction value C1 calculated based on the operation state and performance of the image forming apparatus 5, the size of the printing paper M, the paper characteristics, etc. When applying and not performing image formation, it is used as a correction value for adjusting the position of the image at the time of image formation.

  The correction value calculation unit 420 determines which of the calculated correction value C1 and the limit correction value to use, according to the flowchart shown in FIG. FIG. 22 is a flowchart showing a flow of processing for determining a correction value used in image formation according to the present embodiment. The flowchart in FIG. 22 is executed as processing for reflecting the correction value in step S2105.

  The correction value calculation unit 420 determines whether the calculated correction value C1 is within the range of the limit correction value (S2201). If the calculated correction value C1 is within the range of the limit correction value (S2201 / YES), the correction value calculation unit 420 transmits the calculated correction value C1 to the job information processing unit 120 and the engine control unit 220 (S2202) .

  If the calculated correction value C1 is not within the range of the limit correction value (S2201 / NO), the correction value calculation unit 420 determines whether the calculated correction value C1 is equal to or more than the limit correction value (S2203) . If the calculated correction value C1 is equal to or larger than the limit correction value (S2203 / YES), the correction value calculation unit 420 transmits the upper limit value of the limit correction value to the job information processing unit 120 and the engine control unit 220 (S2204).

  On the other hand, when the calculated correction value C1 is not equal to or greater than the limit correction value (S2203 / NO), the correction value C1 calculated by the correction value calculation unit 420 is a value that does not reach the limit correction value. Therefore, when the calculated correction value C1 is not equal to or more than the limit correction value, the correction value calculation unit 420 transmits the lower limit value of the limit correction value to the job information processing unit 120 and the engine control unit 220 (S2204).

  The job information processing unit 120 and the engine control unit 220 adjust the position of the image on the printing paper M on the first side based on the received correction value C1 or the limit correction value. By this process, the position of the image formed on the first surface of the printing paper M is adjusted to the ideal position.

  After the process of step S2105, the job information processing unit 120 causes the RIP processing unit 110 to generate bitmap data for forming the position detection mark 7 on the printing paper M. The engine control unit 220 receives bit map data including the position detection mark 7 via the data acquisition unit 210, inputs the bit map data to the print processing unit 310, and executes image formation of the position detection mark 7 on the printing paper M (S2106).

  When the position detection mark 7 is formed, the engine control unit 220 conveys the print sheet M to the reading unit 401 so that the surface on which the position detection mark 7 is formed can be read by the reading unit 401. The reading unit 401 scans the print sheet M to generate a read image, and the sensor image acquisition unit 410 acquires a read image including the position detection mark 7 (S2107). The read image generated in step S2107 is used as a read image of the printing paper M on the second side.

  The correction value calculation unit 420 calculates the correction value C2 as described above based on the coordinates of the position detection mark 7 included in the read image on the second side and the coordinates of the end of the printing paper M (S2108).

  At this time, for the correction value C2, the read image of the printing paper M is obtained by an arbitrary number of sheets, and the correction value calculated based on the coordinates of the position detection mark 7 and the coordinates of the end of the printing paper M is averaged. May be In the case of averaging, the operations of S2106 to S2108 are repeated until the correction value C2 in the read image of the printing paper M for an arbitrary number of sheets is obtained, and the correction value calculation unit 420 calculates the average value of the obtained correction values C2. (S2109). When the correction values C2 are not averaged by a plurality of read images, the process of S2109 is omitted.

  Further, similarly to the correction value C1, the process of determining the correction value used in the image formation described in FIG. 22 is executed in step S2110 also for the correction value C2. As a result of this processing, the correction value calculation unit 420 determines which correction value is to be used among the correction value C2, the upper limit value of the limit correction value, and the lower limit value of the limit correction value, and the determined correction value is processed by the job information processing. It transmits to section 120 and engine control section 220. The job information processing unit 120 and the engine control unit 220 adjust the position of the image on the printing paper M on the second side based on the received correction value C2 or the limit correction value. By this process, the position of the image formed on the second surface of the printing paper M is adjusted to the ideal position.

  At this time, when the shape of the printing paper M is the ideal shape, the image of the first surface formed on the printing paper M by using the correction value reflected in the image formation by the time when the process of S2110 is completed. The image on the second surface side should have a positional relationship in which the positions of the image on the first surface and the image on the second surface correspond when the printing paper M is viewed through the watermark.

  However, in actuality, the shape of the printing paper M is ideal because the shape of the printing paper M expands and contracts due to the dispersion of the shape of the printing paper M due to a cutting error or the like in the manufacturing process of the printing paper M It is rare to be shaped.

  Therefore, in the present embodiment, the correction value C3 for adjusting the relative position of the image formed on the first surface and the second surface is calculated. The job information processing unit 120 causes the RIP processing unit 110 to generate bitmap data for forming the position detection mark 7 on the printing paper M, using the correction value reflected in S2105.

  The engine control unit 220 receives bit map data including the position detection mark 7 via the data acquisition unit 210, inputs the bit map data to the print processing unit 310, and executes image formation of the position detection mark 7 on the printing paper M (S2111).

  When the position detection mark 7 is formed, the engine control unit 220 conveys the print sheet M to the reading unit 401 so that the surface on which the position detection mark 7 is formed can be read by the reading unit 401. The reading unit 401 scans the printing paper M to generate a read image, and the sensor image acquisition unit 410 acquires a read image including the position detection mark 7 (S2112). Note that the read image generated in S2112 is used as a read image of the printing paper M on the first surface when calculating the correction value C3.

  The coordinate conversion unit 430 executes the process of converting the coordinates as described above based on the coordinates of the position detection mark 7 included in the read image of the first surface acquired in S2112 and the coordinates of the end of the printing paper M. (S2113).

  Then, based on the coordinates of the position detection mark 7 included in the read image of the first surface and the coordinates of the end portion of the printing paper M, the correction value calculation unit 420 converts the ideal position of the second surface and the conversion as described above. The correction value C3 is calculated based on the difference with the position coordinate 8 on the later first surface (S2114).

  At this time, as for the correction value C3, the read image of the printing paper M is acquired for an arbitrary number of sheets, and the correction value calculated based on the coordinates of the position detection mark 7 and the coordinates of the end of the printing paper M is averaged. May be In the case of averaging, after the operations of S2111 to S2114 are repeated until the correction value C3 in the read image of the print sheet M for an arbitrary number of sheets is obtained, the correction value calculation unit 420 averages the obtained correction values C3. A value is calculated (S2115). When the correction values C3 of the plurality of read images are not averaged, the process of S2115 is omitted.

  Also for the correction value C3, similarly to the correction value C1 and the correction value C2, the process of determining the correction value used in the image formation described in FIG. 22 is executed in S2116. As a result of this processing, the correction value calculation unit 420 determines which correction value is to be used among the correction value C3, the upper limit value of the limit correction value, and the lower limit value of the limit correction value, and the determined correction value is processed by the job information processing. It transmits to section 120 and engine control section 220.

  The job information processing unit 120 and the engine control unit 220 adjust the position of the image on the printing paper M on the second side based on the received correction value C3 or the limit correction value. By this process, the position of the image formed on the second side of the printing paper M is adjusted to the position corresponding to the ideal position of the image to be printed on the first side.

  When the job information processing unit 120 reflects the received correction value C3 or limit correction value, the RIP processing unit 110 receives bit map data for forming the confirmation chart CH1 as shown in FIG. 23 on the printing paper M. Generate The engine control unit 220 receives the bitmap data including the chart CH1 via the data acquisition unit 210, and inputs the bitmap data to the print processing unit 310 to execute the image formation of the chart CH1 on the printing paper M (S2117) .

  It is desirable that the chart CH1 has lines parallel to the transport direction X of the printing paper M and a direction orthogonal to the transport direction X, and can check the degree of deviation by watermarking. The user of the image forming apparatus 5 confirms the chart CH1, and controls that when the deviation of the chart CH1 formed on the first and second surfaces is less than a predetermined value and there is no problem in the printing result The operation to be input to the device 1000 is executed.

  When the information indicating that there is no problem in the print result of the chart CH1 formed on the first surface and the second surface output from the control device 1000 is received (S2118 / YES), the correction value calculation unit 420 corrects the correction value The C1, the correction value C2, and the correction value C3 are stored in the correction value storage unit 420a configured by the storage medium (S2119), and the job information processing unit 120 ends the present processing. Therefore, the correction value calculation unit 420 determines whether to store the correction value C1, the correction value C2, and the correction value C3 in the correction value storage unit 420a based on the reading result of the chart CH1.

  The correction value C1, the correction value C2, and the correction value C3 stored in S2119 are always reflected when an image forming output is performed. The correction value storage unit 420a may store the correction value C1, the correction value C2, and the correction value C3 in association with the sheet setting information for each type of printing sheet M. At this time, when the correction value C1, the correction value C2, and the correction value C3 are stored in association with each type of printing paper M, setting information for each paper tray may be used. The type of printing paper M indicates, for example, a paper type, a brand name assigned to each maker, characteristics of the paper, and the like.

  When the correction value C1, the correction value C2, and the correction value C3 are finely adjusted by the user of the image forming apparatus 5 after storing the correction value C1, the correction value C2, and the correction value C3 in the correction value storage unit 420a, The correction value calculation unit 420 may be configured to update the values of the correction value C1, the correction value C2, and the correction value C3 stored in the correction value storage unit 420a based on the control information from the control device 1000. .

  In addition, the job information processing unit 120 adjusts the position of the image formed on the printing paper M as shown in FIG. 24 to FIG. 26 based on the correction value C1, the correction value C2, the correction value C3 and the limit correction value. Then, the RIP processing unit 110 generates bitmap data.

  FIG. 24 shows an offset process for moving the image from the actual position (P1, P2, P3, P4) of the image formed on the printing paper M to the ideal position (P1 ', P2', P3 ', P4'). It is a figure which shows an aspect. The offset process is a process executed by the offset processing unit 121.

  The offset processing unit 121 sets the correction value C1, the correction value C2, the correction value C3, and the limit correction value as the movement amount of coordinates from the coordinates of the actual position (P1, P2, P3, P4) to the ideal position (P1 ', P2'). , P3 ', P4').

  FIG. 25 is a magnification process for enlarging the image from the actual position (P1, P2, P3, P4) of the image formed on the printing paper M to the ideal position (P1 ', P2', P3 ', P4'). It is a figure which shows an aspect. The magnification process is a process executed by the magnification adjustment processing unit 122. Although FIG. 25 shows the case where the actual image is enlarged and adjusted to the ideal position, the actual image may be reduced and adjusted to the ideal position.

  The magnification adjustment processing unit 122 uses the correction value C1, the correction value C2, the correction value C3, and the limit correction value as the magnification of the coordinates, and multiplies the coordinates of the actual position (P1, P2, P3, P4) to obtain the ideal position. Move the image to (P1 ', P2', P3 ', P4').

  FIG. 26 is a skew correction that tilts the image from the actual position (P1, P2, P3, P4) of the image formed on the printing paper M to the ideal position (P1 ', P2', P3 ', P4') It is a figure which shows the aspect of a process. The skew correction process is a process executed by the skew correction processing unit 123.

  The skew correction processing unit 123 uses the correction value C1, the correction value C2, the correction value C3, and the limit correction value as an angle for moving the coordinates, with respect to the coordinates of the actual position (P1, P2, P3, P4). The amount of movement is determined by the trigonometric function, and the image is moved to the ideal positions (P1 ', P2', P3 ', P4').

  As described above, the image forming apparatus according to the present embodiment calculates the correction value based on the coordinates of the end portion of the printing paper and the central coordinates of the position detection mark on the printing paper. Further, by performing the image formation while reflecting the calculated correction value, it is possible to eliminate the positional deviation of the image printed on the printing paper. Furthermore, when performing duplex printing on printing paper, it is possible to accurately adjust the relative positional relationship between the position of the image formed on the front side and the position of the image formed on the back side.

  When the positional deviation in the sub scanning direction is eliminated by the correction value calculated based on the detection result of the position detection mark 7, the rotational speed of the transfer roller 14 is further adjusted after reflecting the limit correction value. Can change the magnification in the sub-scanning direction.

  FIG. 28 is a flow chart showing a process flow of changing the magnification in the sub scanning direction by adjusting the rotational speed of the transfer roller 14. The process described in FIG. 28 is an additional process of the process described in FIG. Therefore, processing blocks that perform the same processing as the flowchart in FIG.

  After the process of S2115, the correction value calculation unit 420 executes a process of determining whether the correction value C3 is to be used as a correction value for image formation (S2801). FIG. 29 is a flow chart showing a process of determining whether the correction value C3 is to be used as a correction value used in image formation.

  If the calculated correction value C3 is within the range of the limit correction value (S2901 / YES), the correction value calculation unit 420 transmits the calculated correction value C3 to the job information processing unit 120 and the engine control unit 220 (S2902) ).

  If the calculated correction value C3 is not within the range of the limit correction value (S2901 / NO), the correction value calculation unit 420 sends the lower limit value or the upper limit value of the limit correction value to the job information processing unit 120 and the engine control unit 220. It transmits (S2903).

  In the process of S2903, when the calculated correction value C3 exceeds the upper limit value of the limit correction value, the correction value calculation unit 420 transmits the upper limit value of the limit correction value to the job information processing unit 120 and the engine control unit 220. Do.

  On the other hand, if the calculated correction value C3 is less than the lower limit value of the limit correction value in the process of S2903, the correction value calculation unit 420 sets the lower limit value of the limit correction value to the job information processing unit 120 and the engine control unit. Send to 220

  Then, the engine control unit 220 adjusts the rotational speed of the roller 14b, and adjusts the magnification in the sub-scanning direction of the image transferred onto the printing paper M (S2904). When the rotational speed of the roller 14b is adjusted, the engine control unit 220 executes the process from S2101 again.

  When the calculated correction value C3 is transmitted to the job information processing unit 120 and the engine control unit 220 (S2902), the engine control unit 220 receives bitmap data including the chart CH1 via the data acquisition unit 210. The print processing unit 310 inputs the image formation of the chart CH1 on the printing paper M (S2802).

  The user of the image forming apparatus 5 confirms the chart CH1, and when the magnification shift in the sub scanning direction of the chart CH1 formed on the first surface and the second surface is smaller than a predetermined value, the controller 1000 recognizes that. The operation input to is executed (S2803 / NO).

  On the other hand, the user of the image forming apparatus 5 confirms the chart CH1, and if the deviation of the magnification of the chart CH1 formed on the first surface and the second surface in the sub scanning direction is equal to or more than a predetermined value, An operation to be input to the control device 1000 is executed (S2803 / YES).

  When the information indicating that the shift in magnification in the sub-scanning direction of the chart CH1 formed on the first surface and the second surface is smaller than a predetermined value output from the control device 1000 is received (S2803 / NO), the correction value The calculation unit 420 stores the correction value C1, the correction value C2, and the correction value C3 in the correction value storage unit 420a configured by the storage medium (S2804), and the job information processing unit 120 ends the present processing.

  When the information indicating that the shift in magnification in the sub-scanning direction of the chart CH1 formed on the first surface and the second surface is greater than or equal to a predetermined value output from the control device 1000 is received (S2803 / YES), job information The processing unit 120 ends this processing.

  As described above, when processing is performed according to the flowchart shown in FIG. 28, in addition to regenerating bit map data to adjust the position of the image formed on the printing paper M, the rotational speed of the roller 14b is adjusted. The magnification in the sub-scanning direction of the image transferred to the printing paper M can be adjusted.

  In the flowchart of FIG. 28, the chart CH1 is checked after it is determined whether to reflect the correction value C3. Here, as shown in FIG. 30, the chart CH1 may be confirmed before reflecting the correction value C3, and the magnification in the sub-scanning direction of the image transferred onto the printing paper M may be adjusted.

  FIG. 30 is a flow chart showing another processing flow of changing the magnification in the sub scanning direction by adjusting the rotational speed of the transfer roller 14. The process described with reference to FIG. 30 is an additional process to the process described with reference to FIG. Therefore, processing blocks that perform the same processing as the flowchart in FIG.

  After the process of S2115, the engine control unit 220 receives the bitmap data including the chart CH1 via the data acquisition unit 210, and inputs the bitmap data to the print processing unit 310 to form the image of the chart CH1 on the printing paper M. Is executed (S3001).

  The bitmap data used for the chart CH1 generated in S3001 is the one in which the correction value C1, the correction value C2, or the respective limit correction values are reflected. That is, the correction value C3 is not reflected in the chart CH1 generated in S3001.

  The user of the image forming apparatus 5 confirms the chart CH1, and when the magnification shift in the sub scanning direction of the chart CH1 formed on the first surface and the second surface is smaller than a predetermined value, the controller 1000 recognizes that. The operation to be input to is executed (S3002 / NO).

  On the other hand, the user of the image forming apparatus 5 confirms the chart CH1, and if the deviation of the magnification of the chart CH1 formed on the first surface and the second surface in the sub scanning direction is equal to or more than a predetermined value, The operation to be input to the control device 1000 is executed (S3002 / YES).

  When the information indicating that the shift in magnification in the sub-scanning direction of the chart CH1 formed on the first surface and the second surface is greater than or equal to a predetermined value output from the control device 1000 is received (S3002 / YES), job information The processing unit 120 ends this processing.

  When the information indicating that the shift in magnification in the sub-scanning direction of the chart CH1 formed on the first surface and the second surface is smaller than a predetermined value output from the control device 1000 is received (S3002 / NO), the correction value The calculation unit 420 stores the correction value C1, the correction value C2, and the correction value C3 in the correction value storage unit 420a configured by the storage medium (S3003).

  Then, when the calculated correction value C3 is within the range of the limit correction value (S3004 / YES), the correction value calculation unit 420 transmits the calculated correction value C3 to the job information processing unit 120 and the engine control unit 220. .

  When the calculated correction value C3 is transmitted to the job information processing unit 120 and the engine control unit 220 (S3004 / YES), the engine control unit 220 generates a bitmap including the chart CH1 via the data acquisition unit 210. The data is received and input to the print processing unit 310, and the image formation of the chart CH1 is executed again on the print sheet M (S3005).

  If the calculated correction value C3 is not within the range of the limit correction value (S3004 / NO), the correction value calculation unit 420 notifies the job information processing unit 120 to that effect, and the job information processing unit 120 performs this processing. finish.

  The user of the image forming apparatus 5 confirms the chart CH1, and when the magnification shift in the sub-scanning direction of the chart CH1 formed on the first surface and the second surface is equal to or more than a predetermined value, the controller 1000 is notified. The operation to input to is executed (S3006 / YES).

  When the information indicating that the shift in magnification in the sub-scanning direction of the chart CH1 formed on the first surface and the second surface is greater than or equal to a predetermined value output from the control device 1000 is received (S3006 / YES), engine control The unit 220 adjusts the rotational speed of the roller 14b, and adjusts the magnification in the sub-scanning direction of the image transferred onto the printing paper M (S2904). When the rotational speed of the roller 14b is adjusted, the engine control unit 220 executes the process from S2101 again.

  When the information indicating that the shift in magnification in the sub-scanning direction of the chart CH1 formed on the first surface and the second surface and output from the control device 1000 is less than or equal to a predetermined value is received (S3006 / NO), job information The processing unit 120 ends this processing.

  As described above, in the flowchart shown in FIG. 30, whether the magnification deviation of the chart CH1 formed on the first surface and the second surface in the subscanning direction is confirmed by the user's visual observation, and the rotational speed of the roller 14b is adjusted It is determined whether or not. Therefore, the magnification in the sub-scanning direction of the image transferred to the printing paper M can be adjusted by reflecting the user's sense more.

  Although the image forming apparatus according to the present embodiment has been described by taking an electrophotographic image forming apparatus as an example, the present invention can be similarly applied to, for example, an inkjet image forming apparatus 5. In the inkjet type image forming apparatus 5, as shown in FIG. 27, the reading unit 401 is a printing sheet on which an image is formed in the image forming unit including the inkjet head 2 and the drum 3 in the conveyance path R of the printing sheet M. It is disposed on the downstream side of the drying unit 31 that dries M and on the upstream side of the reversing conveyance unit 51 for reversing the printing paper M.

  Further, in the present embodiment, the shape of the printing paper M has been described as a rectangle, but as shown in FIG. 31, the present invention can be similarly applied to, for example, a circle and a polygon. For example, as shown in FIG. 31, the position detection mark 7 may be printed by drawing a plurality of tangents to the circular printing paper M and regarding the tangents as the end of the printing paper M. The position detection mark 7 must be formed on the printing paper M. The position of the image can be adjusted by forming the position detection mark 7 in the same manner for the printing paper M of other polygons and other shapes.

  Further, in the image forming apparatus according to the present embodiment, the reading unit is provided inside the image forming apparatus. Therefore, since it is possible to reduce the operation that the user of the image forming apparatus has to perform in order to read the printed matter, the effect of reducing the time required to adjust the position of the image can be expected. In addition, since there is no need to provide a scanner mechanism outside the image forming apparatus, the present invention can be applied even when an external scanner is not installed.

5 Image forming apparatus 10 CPU
20 RAM
30 ROM
40 HDD
50 I / F
60 LCD
70 operation unit 80 dedicated device 90 bus 11 conveyance belt 12, 12Y, 12C, 12K photosensitive drum 13 paper feed tray 14 transfer roller 15 fixing roller 16 reverse pass 100 image processing unit 200 engine controller 300 print engine 400 image position detection device 1000 Control device

U.S. Patent Application Publication 2004/0215411

Claims (11)

An image forming apparatus that adjusts an image position to form an image on a recording medium,
An image forming unit for forming the image on the recording medium;
A reading unit that reads a recording medium on which a position detection mark is formed as the image and generates a read image;
A correction value calculation unit that calculates a correction value for adjusting the position of the image formed on the recording medium based on the read image;
Including
The correction value calculation unit
Calculating a first correction value based on the read image of the first surface of the recording medium;
Calculating a second correction value based on the read image of the second surface of the recording medium;
Third, adjusting the position of the image formed on the second surface of the recording medium based on the read image of the first surface of the recording medium on which the position detection mark is formed by reflecting the first correction value An image forming apparatus characterized by calculating a correction value. The correction value calculation unit
The first correction value, the second correction value, and the third correction value are calculated based on the coordinates of the position detection mark and the coordinates of the end portion of the recording medium included in the read image. The image forming apparatus according to claim 1. The image forming unit is
The position of the image formed on the recording medium is adjusted based on the first correction value, the second correction value, and the third correction value. Image forming device. The reading unit is
Reading a predetermined number of the recording media to generate the predetermined number of read images;
The correction value calculation unit
The first correction value, the second correction value, and the third correction value are calculated based on the predetermined number of read images. An image forming apparatus according to claim 1. 5. A correction value storage unit for storing the first correction value, the second correction value, and the third correction value in association with each type of the recording medium. An image forming apparatus according to any one of the preceding claims. The image forming unit is
The image is formed on the recording medium by moving the position of the image based on the first correction value, the second correction value, and the third correction value. 5. The image forming apparatus according to any one of 5. The image forming unit is
The image is formed on the recording medium by enlarging or reducing the image based on the first correction value, the second correction value, and the third correction value. 5. The image forming apparatus according to any one of 5. The image forming unit is
The image is formed on the recording medium by inclining the image based on the first correction value, the second correction value, and the third correction value. An image forming apparatus according to any one of the preceding claims. The image forming unit is
Forming a chart for confirming the position of an image formed on the recording medium on the first surface and the second surface;
The correction value calculation unit
It is determined whether or not the first correction value, the second correction value, and the third correction value are stored in the correction value storage unit based on the reading result of the chart. 5. The image forming apparatus according to 5. A speed control unit that controls the speed of a transfer roller that forms the image on the recording medium;
The speed control unit
The image forming apparatus according to any one of claims 1 to 9, wherein the speed is controlled such that the image adjusted based on the correction value is formed on the recording medium. An image forming method for adjusting an image position to form an image on a recording medium, comprising:
Forming the image on the recording medium;
Reading a recording medium on which position detection marks are formed as the image, and generating a read image;
As a correction value for adjusting the position of the image formed on the recording medium based on the read image,
Calculating a first correction value based on the read image of the first surface of the recording medium;
Calculating a second correction value based on the read image of the second surface of the recording medium;
Third, adjusting the position of the image formed on the second surface of the recording medium based on the read image of the first surface of the recording medium on which the position detection mark is formed by reflecting the second correction value An image forming method characterized by calculating a correction value.