Image forming apparatus

Abstract

To provide an image forming apparatus with which, even when the accuracy of cutting a sheet bundle used for printing is not sufficient, a good printing result is obtained with less positional deviation of images between the sheets after cutting in a subsequent step.SOLUTION: An image forming apparatus comprises: image forming means that forms an image on a sheet; and image position adjustment means that adjusts the image on the sheet printed by the image forming means, on the basis of the positional relationship between the edges of the sheet and measurement patterns on the sheet printed by the image forming means. The image position adjustment means adjusts the position of the image on the sheet printed by the image forming means on the basis of the positional relationship between the measurement patterns and only one of opposing sheet edges, of the edges of the sheet.SELECTED DRAWING: Figure 8A

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus. [Background technology]

[0002] In the printing industry, it is common to print images along with crop marks on paper that is larger than the final product, and then perform post-processing, including cutting, after printing. However, because printing paper is not necessarily a precise rectangle, cutting the paper accurately at the position of the crop marks requires a lot of effort.

[0003] Therefore, for example, Patent Document 1 discloses a technology that indicates the initial paper cutting position on the stack of paper to be cut and controls the image position to be aligned with the opposite edge, thereby making it possible to easily carry out the cutting work. Patent Document 1 proposes a means for measuring image distortion based on the distance between the paper outline and a measurement pattern (register mark) for measuring the image position, and adjusting the image position based on the image deformation.

[0004] Furthermore, in order to successively measure and correct image misalignment over time during printing, a commonly used method (called real-time adjustment) is to print registration marks at the four corners of the image to be printed, measure the distance between these and the paper edge, and adjust the distance between the paper edge and the registration marks at the four corners to maintain a constant distance, thereby adjusting image misalignment during printing. Real-time adjustment makes it possible to appropriately respond to changes over time in the image forming device during continuous printing, thereby achieving good image registration. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-76845 Summary of the Invention [Problem to be solved by the invention]

[0006] As mentioned above, when adjusting the image position based on the positional relationship between the paper edge and the registration marks at the four corners, no particular problems arise if the cutting precision of the paper stack used in printing is sufficient; however, if the paper cutting precision is poor, the positional relationship between the paper edge and the registration marks at the four corners will change "due to the paper" as the printing progresses, and if adjustments are made to stabilize this, the image magnification will change, and the image position may shift during the cutting process in post-processing.

[0007] Figure 13A shows an image of a stack of paper that has been accurately cut. If the stack of paper has been accurately cut into a rectangle as shown in Figure 13A, by adjusting the distance between the paper edge and the registration marks at the four corners as needed to keep them constant, it is possible to print the image at a stable image position, as shown in Figure 13B. In Figure 13B, the image position is inside the registration marks at the four corners (the same applies to Figure 14B).

[0008] Figure 14A shows an example of an inaccurately cut stack of paper, with the paper size increasing toward the bottom. As shown in Figure 14A, if the cut state of the stack of paper used for printing is distorted, the paper size will change as printing progresses. In this case, if the image position is adjusted so that the distance between the paper edge and the four corner registration marks is constant, as shown in Figure 14B, the image position relative to each paper edge will be stable, but the image magnification will change as the paper size changes. If the printed stack of paper is trimmed based on the position at the start of printing, the image position after trimming will be different between the start of printing (when the paper at the top of the stack is used) and the end of printing (when the paper at the bottom of the stack is used). Furthermore, when trimming, the printed paper at the end of printing is trimmed at the dotted line in Figure 14B, which may cause the image to extend beyond the edge of the paper.

[0009] The present invention aims to provide an image forming apparatus that can produce good print results with little misalignment of images between sheets of paper after cutting in a subsequent process, even when the cutting accuracy of the stack of sheets used for printing is insufficient. [Means for solving the problem]

[0010] In order to solve the above problem, the invention described in claim 1 is: an image forming means for forming an image on a sheet; an image position adjusting means for adjusting the position of the image printed on the paper by the image forming means based on the positional relationship between the edge of the paper and the measurement pattern printed on the paper by the image forming means; An image forming apparatus comprising: The image position adjusting means adjusts the position of the image printed on the paper by the image forming means based on the positional relationship between only one of the opposing paper edges and the measurement pattern. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide an image forming apparatus that can produce good printing results with little misalignment of images between sheets of paper after cutting in the subsequent process, even if the cutting accuracy of the stack of sheets of paper used for printing is insufficient. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 2 is a block diagram showing a functional configuration of the image forming apparatus. [Figure 2] FIG. 2 is a diagram illustrating mechanical components of each section of the image forming apparatus. [Figure 3] FIG. 10 is a diagram illustrating a background member. [Figure 4] FIG. 10 is a diagram showing an example of a printer's mark printed in the first adjustment mode. [Figure 5A] 10A and 10B are diagrams showing ranges of adjustment values ​​and adjustment images for each adjustment item, namely, vertical magnification, horizontal magnification, vertical image shift, and horizontal image shift. [Figure 5B] 10A and 10B are diagrams showing the range of adjustment values ​​and an image of adjustment for each of the adjustment items of rotation, skew, vertical trapezoid, horizontal trapezoid, bend, and bend position. [Figure 6] FIG. 10 is a diagram showing an example of printer's marks printed in the second adjustment mode. [Figure 7]FIG. 10 is a diagram showing printed matter at the start and end of a job in which a conventional real-time adjustment is performed, in which the paper size changes during the job and the paper size at the end of the job is larger than the paper size at the start of the job. [Figure 8A] 10A and 10B are diagrams showing printed matter at the start and end of a job when image position adjustment is performed in the edge-based mode of the second mode. [Figure 8B] 10A and 10B are diagrams illustrating printed matter at the start and end of a job when image position adjustment is performed in the center reference mode of the second mode. [Figure 9] FIG. 10 is a diagram showing an example in which, when image position adjustment is performed in the second mode, the paper expands or contracts after an image is printed on the first side of the paper to be printed first, causing a discrepancy in the magnification of the images on the front and back sides. [Figure 10A] 10A and 10B are diagrams showing printed matter at the start and end of a job when front and back position adjustment is performed in the edge-based mode of the third mode. [Figure 10B] 10A and 10B are diagrams showing printed matter at the start and end of a job when front and back magnification adjustment is performed in the edge-based mode of the third mode. [Figure 11] 2 is a flowchart showing the flow of a setting process executed by the control unit of FIG. 1. [Figure 12] 10 is a flowchart showing the flow of an image position adjustment process executed by the control unit in FIG. [Figure 13A] FIG. 10 is an image diagram of a stack of sheets that has been accurately cut. [Figure 13B] 13B is a diagram showing the image positions at the start and end of printing when printing is performed using the paper stack shown in FIG. 13A while making adjustments as needed to keep the distances between the paper edges and the register marks at the four corners constant. FIG. [Figure 14A] This is an image diagram of a stack of paper sheets with paper sizes increasing downwards. [Figure 14B] 14B is a diagram showing the image positions at the start and end of printing when printing is performed using the paper stack shown in FIG. 14A while making adjustments as needed to keep the distances between the paper edges and the register marks at the four corners constant. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings, but the scope of the invention is not limited to the illustrated examples.

[0014] [Configuration of Image Forming Apparatus] First, the configuration of an image forming apparatus 100 according to this embodiment will be described. FIG. 1 is a functional block diagram showing the functional configuration of each unit of the image forming apparatus 100, and FIG. 2 is a diagram showing the mechanical components of each unit of the image forming apparatus 100. As shown in FIG.

[0015] As shown in FIG. 1, the image forming apparatus 100 is configured to include a control unit 101, a communication unit 102, an operation display unit 103, a memory unit 104, a paper feed unit 105, a conveying unit 106, a document reading unit 110, an image processing unit 140, an image forming unit 150, a fixing unit 160, an output reading unit 170, and an image analysis unit 180.

[0016] The control unit 101 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc. The CPU of the control unit 101 reads a program corresponding to the processing content from the ROM, loads it into the RAM, and centrally controls the operations of each unit of the image forming apparatus 100 in cooperation with the loaded program.

[0017] The communication unit 102 is configured by a communication control card such as a LAN (Local Area Network) card, and transmits and receives various data to and from external devices (for example, controllers) connected to a communication network such as a LAN or WAN (Wide Area Network).

[0018] The operation display unit 103 includes a display device such as a liquid crystal display or an organic EL display, and an input device (operation unit) such as operation keys, a touch panel or a numeric keypad arranged over the screen of the display device. The operation display unit 103 displays various information on the display device, and converts user input operations on the input device into operation signals and outputs them to the control unit 101.

[0019] The storage unit 104 is configured, for example, by a non-volatile semiconductor memory (so-called flash memory), a hard disk drive, etc. The storage unit 104 stores various data including various setting information related to the image forming apparatus 100, job information (setting information and image data), etc. For example, the storage unit 104 stores setting information (adjustment mode, register mark position setting, etc.) related to the second adjustment mode set in the setting process (see FIG. 11) described below. The storage unit 104 also stores adjustment values ​​(adjustment values ​​for the front and back) for each adjustment item of image position adjustment.

[0020] The paper feed unit 105 feeds paper sheets stored in a paper feed tray in accordance with instructions from the control unit 101 . Conveying unit 106 has a conveying path and a plurality of conveying roller pairs such as registration roller pairs, and conveys paper fed from paper feeding unit 105 within image forming apparatus 100. Conveying unit 106 also has a reversing mechanism 106a, which can reverse the paper and convey it to image forming unit 150.

[0021] The document reading unit 110 is configured to include an automatic document feeder called an ADF (Auto Document Feeder), a document image scanning device (scanner), and the like, and reads an image of a document to generate image data.

[0022] Under the control of the control unit 101, the image processing unit 140 converts image data read by the document reading unit 110 and PDL data transmitted from an external device (for example, a PC (Personal Computer)). Image data input from a device (such as a controller that performs rasterization processing on data) is subjected to various image processing such as image position adjustment, tone correction, color conversion, shading correction, and compression processing. The image data that has undergone these processes is input to the image forming unit 150.

[0023] The image forming unit 150 prints an image on a sheet based on the job setting information and image data. The fixing unit 160 fixes the toner image printed on the paper to the paper using heat and pressure. In FIG. 2, the image forming unit 150 is illustrated as an image forming unit of a so-called electrophotographic type, but is not limited to this, and may be, for example, an inkjet type image forming unit.

[0024] The output reading unit 170 reads an image printed on paper by the image forming unit 150 and fixed by the fixing unit 160, and outputs the obtained read image data to the image analysis unit 180. The output reading unit 170 is disposed downstream of the image forming unit 150 and the fixing unit 160 and is configured to read an image while paper is being transported. The output reading unit 170 includes a reading unit 170a that reads an image on one side of the paper and a reading unit 170b that reads an image on the other side of the paper. The reading units 170a and 170b are provided with background members 171a and 171b, respectively, at positions facing each other across the paper transport path. As shown in FIG. 3, the background members 171a and 171b have a black surface 1711 and a white surface 1712, and can be rotated by a drive source (not shown) to switch the background when reading paper between black and white. The reading size of the output reading unit 170 is larger than the paper size, and is configured to be able to read the edges of all four sides of the paper.

[0025] The image analysis unit 180 analyzes the read image data output by the output reading unit 170, calculates adjustment values ​​for the positions of the images to be printed on the front and back sides of the paper, and outputs the adjustment values ​​to the control unit 101.

[0026] [Image position adjustment operation] Next, the operation of adjusting the image position in the image forming apparatus 100 will be described. Image position adjustment adjusts the position of an image printed on paper in image forming apparatus 100, and has a first adjustment mode and a second adjustment mode.

[0027] The first adjustment mode is a mode in which the position of an image printed on paper by the image forming unit 150 is adjusted before actual printing (before printing based on a job). Specifically, in the first adjustment mode, the image forming unit 150 first prints measurement patterns (called registration marks) T1 to T4 shown in FIG. 4 on the front and back of the paper, each of which is provided a predetermined distance inward from the edges of the four sides of the paper on which the job is printed (e.g., 10 mm from the paper edge). The printout is then read by the output reading unit 170, and the obtained read image data is analyzed by the image analysis unit 180 to obtain the positional relationship (distance) between the paper edge and the registration marks T1 to T4. The image analysis unit 180 then calculates adjustment values ​​for multiple adjustment items for each of the front and back sides so that the distance between the paper edge and the registration marks T1 to T4 (the registration marks facing each paper edge) is a predetermined distance, and stores the calculated values ​​in the storage unit 104. Note that the first adjustment mode may be repeated multiple times to improve measurement accuracy and stability. Alternatively, multiple sheets of printed matter with the registration marks T1 to T4 may be printed, and the adjustment value may be calculated for each sheet, and the average value may be used. During actual printing, the control unit 101 controls the image processing unit 140, the image forming unit 150, the conveying unit 106, etc., based on the adjustment value stored in the storage unit 104, to adjust the position of the image to be printed on the paper.

[0028] The multiple adjustment items calculated in the first adjustment mode include the vertical and horizontal magnification, the vertical and horizontal image shift, rotation, skew, vertical trapezoid, horizontal trapezoid, curvature, and curvature position. It is possible to calculate adjustment values ​​for each of these adjustment items independently. Of the above adjustment items, the magnification, image shift, rotation, skew, vertical trapezoid, and horizontal trapezoid adjustment items can be used to adjust the image position at the four corners. Furthermore, curvature and curvature position are used to adjust image distortion, and using these together allows for more advanced image position adjustment.

[0029] Figure 5A shows the range of adjustment values ​​and an image of the adjustment for each of the adjustment items: vertical magnification, horizontal magnification, vertical image shift, and horizontal image shift. Figure 5B shows the range of adjustment values ​​and an image of the adjustment for each of the adjustment items: rotation, skew, vertical trapezoid, horizontal trapezoid, curvature, and curvature position. Note that the thick arrow A in Figures 5A and 5B indicates the paper transport direction, the solid line indicates the paper, the dotted line indicates the target image position, the hatching indicates the current image position, and the thin arrow indicates the direction in which the image moves due to adjustment. Note that for image shift in Figure 5A, showing both the current image position and the target image position would be difficult to see, so both are shown as the same, and only the direction in which the image moves due to adjustment is shown. Also, the solid line indicating the paper has been omitted from Figure 5B.

[0030] In this embodiment, the first adjustment mode is described as automatically acquiring adjustment values ​​for each adjustment item shown in FIGS. 5A and 5B by reading paper on which register marks T1 to T4 are printed using the output reading unit 170 and analyzing the obtained read image data using the image analysis unit 180. However, the adjustment values ​​for each adjustment item determined by a user visually observing the paper on which register marks T1 to T4 are printed may be input via the operation display unit 103, and the adjustment values ​​may be acquired. Alternatively, the document reading unit 110 may be configured to read and analyze paper on which register marks T1 to T4 are printed. In this case, because the document reading unit 110 is designed for copying, the background is white. For this purpose, to clearly read the paper edges, a dark background paper may be placed on top of the paper on which register marks T1 to T4 are printed, and the printed paper may be read and analyzed as needed (for example, four times) while being turned over and upside down so that the paper edges can be properly read.

[0031] The second adjustment mode is a mode in which the position of an image printed on paper by the image forming unit 150 is adjusted during actual printing (so-called real-time adjustment mode). Specifically, in the second adjustment mode, first, the printer's marks T11 to T14 shown in FIG. 6 are added to the four corners of the paper on which the job is printed, a preset distance inward from the four corners (for example, 3 mm from each of the paper edges on two sides that make up the four corners of the paper), and then the printer's marks are printed on the paper by the image forming unit 150. The printout is then read by the output reading unit 170, and the obtained read image data is analyzed by the image analysis unit 180 to obtain the distance between the paper edge and the printer's marks T11 to T14 (the printer's marks facing each paper edge). Then, the image analysis unit 180 calculates and updates the adjustment value for each adjustment item to be obtained based on the obtained distance between the paper edge and the printer's marks T11 to T14. Based on the updated adjustment values, the control unit 101 controls the image processing unit 140, the image forming unit 150, the conveying unit 106, etc., to adjust the position of the image to be printed on the paper in subsequent printing. The reason why the aforementioned preset distance is smaller in the second adjustment mode is that the second adjustment mode uses images of user content printed together with the registration marks T11 to T14, and this is to prevent the registration marks T11 to T14 from overlapping with the user content. Also, auxiliary information is often printed near the edges of the paper to allow the printing operator to check the printing conditions, etc. If this information overlaps with the registration marks T11 to T14, the second adjustment mode may not function correctly, so a process can be added to white out the image information around the registration marks (so that it is not printed with toner).

[0032] In this embodiment, in the second adjustment mode, adjustment of the bend and bend position is omitted to simplify the process, and therefore independent register marks T11 to T14 are used at the four corners as shown in Fig. 6. Note that, as in the first adjustment mode, adjustment of the bend and bend position may also be performed using register marks T1 to T4.

[0033] Here, in the real-time adjustment performed during actual printing in conventional image forming devices, the image position was adjusted so that the distance between the paper edge and the registration marks T1 to T4 was a predetermined distance, similar to the first adjustment mode described above.

[0034] Figure 7 shows the printout at the start of a job (start of printing) and the end of a job (end of printing) when the paper size changes during the job due to inaccurate cutting of the stack of paper used for printing by the job, resulting in the paper size being larger at the end of the job than at the start of the job, in a job for which conventional real-time adjustment has been performed. The dotted line on the printout at the end of the job in Figure 7 indicates the paper size at the start of the job (the same applies to Figures 8A to 10B). Note that in the printout output by the job, an image based on the job is printed inside the register marks T11 to T14, but this is omitted in Figures 7 to 10B for simplicity.

[0035] As mentioned above, with conventional real-time adjustment, the image magnification is adjusted so that the distance between the paper edge and the four corner register marks remains constant, so if the paper size changes during a job, the image size changes accordingly, as shown in Figure 7. This can result in problems such as the image being cut off after cutting in the printed material at the end of the job, for example, when a stack of printed papers is cut based on the position at the start of the job.

[0036] Therefore, the second adjustment mode of this embodiment includes a first mode that performs adjustment equivalent to conventional real-time adjustment, a second mode that limits the magnification adjustment, and a third mode that limits the magnification adjustment and adjusts the difference between the front and back sides that occurs due to the limiting of the magnification adjustment. Furthermore, each of the second and third modes is configured so that either an edge-based mode that adjusts the position of an image printed on at least one side of the paper so that the distance between the image and a specific paper edge is a predetermined distance, or a center-based mode that adjusts the position of the image printed on the paper so that it is positioned at the center of the paper, can be selected using the operation and display unit 103.

[0037] 8A shows printed matter at the start and end of a job when image position adjustment is performed in the edge-based mode of the second mode, in which edges E1 and E4 are set as specific paper edges. In the second mode, edge-based mode, magnification adjustment is limited and the image position is adjusted to be a specified distance from a specific paper edge (E1, E4 in Figure 8A). Therefore, if a subsequent process is set up to cut the edge (E3, E2) opposite the specific paper edge, as shown in Figure 8A, the image position on the printed material at the start and end of the job can be easily aligned.

[0038] FIG. 8B is a diagram showing printed matter at the start and end of a job when image position adjustment is performed in the center reference mode of the second mode. The second mode, center reference mode, limits the magnification adjustment and adjusts the image position so that it is positioned evenly from each paper edge, allowing the image to be positioned in the center of the paper, as shown in Figure 8B. For example, if there is no cutting in the subsequent process and it is necessary to finish the image to a specified size, image position adjustment in this adjustment mode may be preferable.

[0039] When image position adjustment is performed in the second mode, as shown in Figure 9, after an image is printed on the first side of the paper (here, the front side), the paper may expand or contract, causing a discrepancy in the magnification of the images on the front and back sides. In Figure 9, the solid line register marks represent the front side register marks, and the dotted line register marks represent the back side register marks (similar to Figures 10A and 10B). The third mode is a mode that can adjust the difference between the front and back sides when a discrepancy in the magnification of the images on the front and back sides occurs by limiting the magnification adjustment in this way.

[0040] The methods for adjusting the difference between the front and back sides in the third mode include a method for adjusting the difference between the front and back sides of the images printed on the front and back sides of the paper by adjusting the magnification of the image on the side that will be printed later to match the image on the side that will be printed first in the image forming unit 150 as a reference (called front and back magnification adjustment), and a method for adjusting the position of the image on the side that will be printed later to a position where the positional deviation of the image on the side that will be printed later relative to the image on the side that will be printed first is minimized on average at the four corners (called front and back position adjustment).Which adjustment method to use can be selected using the operation display unit 103.

[0041] FIG. 10A is a diagram showing printed matter at the start and end of a job when front and back position adjustment is performed in the third mode, edge-based mode. FIG. 10B is a diagram showing printed matter at the start and end of a job when the front / back magnification adjustment is performed in the third mode, edge-based mode. As shown in FIGS. 10A and 10B, in the third mode, even if the paper expands or contracts between the printing on the front and back sides, the image positional relationship between the front and back sides can be maintained in a good condition.

[0042] 7 to 10B illustrate the case where the paper size increases as printing progresses. However, conversely, the paper size may also decrease as printing progresses. In this case, if the printer's marks T11 to T14 are printed near the edge of the paper, it is possible that the distance between one of the marks and the paper edge decreases as printing progresses, and that the mark may even extend beyond the edge of the paper. In this case, it may become impossible to adjust the image position correctly. Therefore, in this embodiment, when the magnification adjustment is restricted in the second adjustment mode (i.e., in the second or third mode), the positions of the printer's marks T11 to T14 can be adjusted so that the distance between the marks T11 to T14 and the paper edge is greater than when the magnification adjustment is not restricted. Whether or not to adjust the positions of the printer's marks T11 to T14 can be selected using the operation display unit 103.

[0043] Fig. 11 is a flowchart showing the flow of a setting process for setting various settings such as the adjustment mode in the image position adjustment described above. The setting process shown in Fig. 11 is executed by the CPU of the control unit 101 in cooperation with a program stored in the RAM.

[0044] First, the control unit 101 displays selection buttons for selecting whether or not to restrict the implementation of magnification adjustment on the operation display unit 103. When the selection button for selecting not to restrict the implementation of magnification adjustment is selected by the user's operation of the operation display unit 103 (step S1; NO), the control unit 101 sets the adjustment mode to the first mode (step S2) and ends the setting process.

[0045] In step S1, when the user operates the operation display unit 103 to select a selection button for selecting to limit the implementation of magnification adjustment (step S1; YES), the control unit 101 displays selection buttons for selecting whether or not to implement front-back difference adjustment on the operation display unit 103. When the user operates the operation display unit 103 to select a selection button for selecting not to implement front-back difference adjustment (step S3; NO), the control unit 101 sets the adjustment mode to the second mode (step S4), and proceeds to step S8.

[0046] When the user operates the operation display unit 103 to select a selection button for selecting whether to perform front / back difference adjustment (step S3; YES), the control unit 101 displays selection buttons for selecting whether to perform front / back magnification adjustment on the operation display unit 103. When the user operates the operation display unit 103 to select a selection button for selecting not to perform front / back magnification adjustment (step S5; NO), the control unit 101 sets the adjustment mode to the third mode (front / back position adjustment) (step S6), and proceeds to step S8. When the user operates the operation display unit 103 to select the selection button to select performing front and back magnification adjustment (step S5; YES), the control unit 101 sets the adjustment mode to the third mode (front and back magnification adjustment) (step S7) and proceeds to step S8.

[0047] In step S8, the control unit 101 displays a selection button for selecting whether or not to adjust the register mark position on the operation display unit 103. When the selection button for selecting to adjust the register mark position is selected by the user operating the operation display unit 103 (step S8; YES), the control unit 101 sets the register mark position in the second adjustment mode in a direction away from the paper edge by a predetermined distance from the preset reference position (step S9), and proceeds to step S11. When the user operates the operation display unit 103 to select the selection button for not adjusting the registration mark position (step S8; NO), the control unit 101 sets the registration mark position in the second adjustment mode to a preset reference position (step S10) and proceeds to step S11.

[0048] In step S11, the control unit 101 displays selection buttons for selecting whether or not to align the image position with a specific paper edge on the operation display unit 103. When the selection button for selecting aligning the image position with a specific paper edge is selected by the user operating the operation display unit 103 (step S11; YES), the control unit 101 adds the edge-based mode to the currently set adjustment modes (step S12), and ends the setting process. When the user operates the operation display unit 103 to select a selection button that selects not to align the image position to a specific paper edge (step S11; NO), the control unit 101 adds the center reference mode to the currently set adjustment mode (step S13) and ends the setting process.

[0049] The specific paper edge may be automatically set by the control unit 101 according to, for example, the settings at the time of printing, the paper path, and the post-processing after printing. For example, in a case where, after printing, there are two types of paper, face-up, where the first page is ejected facing up, and face-down, where the first page is ejected facing down, and the face-up / face-down switching control is performed after the paper passes through the output reading unit 170, if a specific paper edge direction (side) is set for the convenience of a subsequent process, the direction of the specific paper edge in the image read by the output reading unit 170 will differ depending on the face-up / face-down setting. Also, if a subsequent process includes an online paper cutter, stapler, or bookbinding machine such as a saddle binder, it is easy to imagine that the paper edge that should be set as the specific paper edge will differ depending on the subsequent device. Therefore, it is preferable that the control unit 101 automatically set the specific paper edge according to the configuration of the subsequent device.

[0050] In addition, in the above setting process, an example has been described in which the user performs various settings related to image position adjustment on the operation panel, but it is also possible to provide a setting function for image position adjustment on a screen restricted to the administrator so that only the administrator can perform the settings, or it is also possible for a service person who performs maintenance on image forming apparatus 100 to open a dedicated maintenance mode screen and perform the settings. Alternatively, it is also possible to set the settings using a mechanical or electrical mechanism such as a DIP switch.

[0051] The image position adjustment process executed by the control unit 101 based on the settings made in the above setting process will be described below. 12 is a flowchart showing the flow of the image position adjustment process. The image position adjustment process is executed by the control unit 101 when a job is selected with image position adjustment set and a command to start printing is issued.

[0052] First, the control unit 101 adjusts the image positions on the front and back sides in the first adjustment mode (step S21). The image position adjustment in the first adjustment mode is as described above, and the same description will be used here. Depending on the color of the paper being used, the control unit 101 switches the surface of the background members 171a and 171b that face the paper in the output reading unit 170 between the black surface 1711 and the white surface 1712 (for white paper, the black surface 1711 faces, and for black paper, the white surface 1712 faces; for other paper colors, an easy-to-read or readable color of the background member is appropriately selected. For black paper, the color of the registration marks printed on the paper may also be formed with a color material that can be easily distinguished from the paper, such as white toner), so that the four sides of the paper edge can be read by the output reading unit 170.

[0053] Next, the control unit 101 starts printing based on the job (step S22), and prints each page of the job while adjusting the image position in the second adjustment mode.

[0054] That is, the control unit 101 first provides the printer's marks T11 to T14 for measuring the distance from the edge of the paper to the margins of the image on the page to be printed (step S23). Here, the control unit 101 adds the register marks T11 to T14 based on the setting information of the register mark positions stored in the storage unit 104.

[0055] Next, the control unit 101 controls the image processing unit 140, the image forming unit 150, the conveying unit 106, etc., based on the adjustment values ​​of each adjustment item stored in the storage unit 104, to adjust the position of the image to be printed on the paper, and causes the image with the registration marks T11 to T14 to be printed on the paper, and the image is fixed by the fixing unit 160 (step S24). Note that when double-sided printing is performed, the control unit 101 controls the conveying unit 106 and the image forming unit 150 to perform double-sided printing.

[0056] Next, the control unit 101 causes the output reading unit 170 to read the printed paper (printed paper) and acquires read image data including the paper edge (step S25).

[0057] Next, the control unit 101 causes the image analysis unit 180 to analyze the read image data acquired by the output reading unit 170 and acquire the distances between the paper edge and the register marks T11 to T14 (step S26).

[0058] Next, the control unit 101 calculates and updates the adjustment values ​​for each adjustment item to be obtained based on the distance between the paper edge and the registration marks T11 to T14 in the set adjustment mode using the image analysis unit 180 (step S27), and proceeds to step S28.

[0059] For example, when the adjustment mode is set to the first mode, the adjustment values ​​for the adjustment items of magnification, image shift, rotation, skew, vertical trapezoid, and horizontal trapezoid are calculated so that the distance between the paper edge and the registration marks T11 to T14 (the registration marks facing each paper edge) is a specified distance, and these adjustment values ​​are updated in the memory unit 104.

[0060] For example, when the adjustment mode is set to the second mode, edge-based mode, the adjustment values ​​for the image shift, rotation, skew, vertical trapezoid, and horizontal trapezoid adjustment items are calculated so that the distance between a specific paper edge and the register mark facing that specific edge is a predetermined distance, and these adjustment values ​​are updated in the storage unit 104. Magnification adjustment is not performed. For example, when the adjustment mode is set to the second mode, center reference mode, the adjustment values ​​for the image shift, rotation, skew, vertical trapezoid, and horizontal trapezoid adjustment items are calculated so that the register marks T11 to T14 are positioned evenly from the paper edge (at the center of the paper), and these adjustment values ​​are updated in the storage unit 104. Magnification adjustment is not performed.

[0061] For example, when the adjustment mode is set to the third mode (front and back position adjustment), first, adjustment values ​​for the adjustment items of image shift, rotation, skew, vertical trapezoid, and horizontal trapezoid are calculated so that the position of the register marks T11 to T14 on the first side that face a specific paper edge is a predetermined distance from the specific paper edge, and these adjustment values ​​are updated in the storage unit 104. Magnification adjustment is not performed. Next, adjustment values ​​for the adjustment items of image shift, rotation, skew, vertical trapezoid, and horizontal trapezoid are calculated so that the positional deviation between the register marks T11 to T14 on the second side printed later and the adjusted register marks T11 to T14 on the first side is minimized on average at the four corners, and these adjustment values ​​are updated in the storage unit 104. Magnification adjustment is not performed.

[0062] In this embodiment, in an adjustment mode that does not restrict magnification adjustment, adjustment values ​​for the adjustment items of magnification, image shift, rotation, skew, vertical trapezoid, and horizontal trapezoid are calculated, and in an adjustment mode that restricts magnification adjustment, adjustment values ​​for the adjustment items of image shift, rotation, skew, vertical trapezoid, and horizontal trapezoid are calculated, but adjustment items with little deviation may be omitted. Also, a configuration may be adopted in which the user can set, via operation display unit 103, which adjustment items the adjustment values ​​of which are to be calculated.

[0063] In the second adjustment mode, the printed paper is read to measure the distance between the registration marks T11 to T14 and the paper edge, and an adjustment value is calculated based on the measurement result. The calculated adjustment value is then applied to the image to be printed. As a result, a delay of, for example, several to several dozen sheets of paper occurs between the printing used for measurement and the printing to which the adjustment value is applied. Therefore, the control unit 101 may control the degree to which the adjustment value is updated to avoid excessive adjustment.

[0064] Furthermore, when calculating each adjustment value, it is preferable that the image analysis unit 180 saves the adjustment values ​​of the most recent multiple adjustments (for example, 20 adjustments), and calculates the adjustment value by taking into account trends using the adjustment value calculated based on the current scanned image data and the most recent multiple adjustment values, thereby improving the adjustment accuracy.

[0065] In step S28, the control unit 101 determines whether printing of all pages has been completed (step S28). If it is determined that printing of all pages has not been completed (step S28; NO), the control unit 101 returns to step S23 and repeats the processes of steps S23 to S28 for the next page. If it is determined that printing of all pages has been completed (step S28; YES), the control unit 101 ends the image position adjustment process.

[0066] A modified example of the image position adjustment process will now be described. [Variation 1] 12 illustrates a case where adjustments are made in the first adjustment mode before a job is executed, but adjustments in the first adjustment mode only need to be made before the execution of a job immediately after replacing a stack of paper, and it is not necessary to perform the first adjustment mode before each job. However, if the user resets the mode settings in the second adjustment mode between jobs and has updated the adjustment values ​​by adjusting only the adjustment mode that was set up until then, the adjustment values ​​in the newly set adjustment mode will not be retained, so it will be necessary to reset the adjustment values ​​and redo the adjustments in the first adjustment mode before the start of the next job. To avoid this and enable smooth switching of the adjustment mode in the second adjustment mode without making adjustments in the first adjustment mode, it is preferable that, in the second adjustment mode, the image analysis unit 180 calculates adjustment values ​​in at least two adjustment modes in parallel and stores them in the storage unit 104. For example, calculation of adjustment values ​​in an adjustment mode set by the user and calculation of adjustment values ​​in a first mode that does not impose restrictions on magnification adjustment are performed in parallel, and each adjustment value is stored in the storage unit 104. Alternatively, the adjustment mode for parallel calculation may be set from the operation display unit 103, and adjustment values ​​in the set adjustment mode may be calculated and stored in parallel with adjustment values ​​in the actual adjustment mode. In this case, the printing result when the adjustment value is updated is actually obtained only in the currently set adjustment mode, so the adjustment value of the adjustment mode for which the adjustment value is calculated in parallel can be calculated as a difference value from the adjustment value of the currently set adjustment mode and updated.

[0067] [Variation 2] If cutting processing is included in the subsequent process, it is preferable that the cutting position can be easily adjusted. If the image position adjustment processing is used to adjust the image position so that it is positioned a predetermined distance from a specific paper edge, by first cutting the edge opposite the specific paper edge, paper cutting and cutting processing can be easily performed even if the paper sizes of the stack of printing paper vary. Here, when performing the cutting process, the user needs to correctly grasp the direction of a specific paper edge, so in the image position adjustment process, for example, to make the first cutting direction (edge) easily identifiable, the design of the crop marks for the first cutting direction (edge) may be changed, a specific mark may be added, or a sheet on top of the print job stack may be printed and overlaid with post-process information indicating the cutting direction and cutting method in a manner that is visible, separate from the actual printed material based on the job. Also, control may be combined in which post-process information is sent from image forming apparatus 100 to a display device installed in front of the cutter, or post-process information is sent from image forming apparatus 100 to a display device installed in front of the cutter via a server.

[0068] [Variation 3] In the above embodiment, a specific paper edge is defined and the image position is adjusted by adjusting the distance between that edge and the register mark, but similar processing results can be obtained by defining a specific register mark and adjusting the distance between the paper edge and the register mark with the paper edge closest to that. Alternatively, a paper edge or register mark that is not used to adjust the distance between the paper edge and the register mark may be specified.

[0069] [Variation 4] The image position adjustment of the above embodiment may be combined with other correction processes, such as conventional misalignment correction, which detects the paper's passage position before printing and calculates and adjusts the paper position and print image misalignment correction amount based on the detected information. For example, a mechanism is generally used that provides a sensor to read the paper's passage position before printing and corrects paper misalignment immediately before printing based on the results. However, if the sensor detects only one side of the paper edge (e.g., the front side), it is expected that the image position will be more stably controlled relative to the front side of the paper edge. In such cases, the edge side read by the sensor may be set as the specific paper edge, or a message recommending that setting be displayed on the operation screen. Similarly, if a separate mechanism for regulating paper position is provided, the paper edge that is most likely to stabilize the relationship between the image position and the paper edge through that regulation may be set or recommended as the specific paper edge.

[0070] [Variation 5] In the image forming device 100 of the above embodiment, the second adjustment mode is configured to have multiple adjustment modes, and it has been described that the user selects which adjustment mode to use for adjustment, but any one of the adjustment modes may be incorporated into the image forming device.

[0071] [Variation 6] Furthermore, in the above embodiment, the image analysis unit 180 analyzes the image data read by the output reading unit 170 on the printed paper to calculate an adjustment value, and the control unit 101 controls each unit including the image forming unit 150 based on the calculated adjustment value to adjust the image position. However, the calculation of the adjustment value by analyzing the image data read by the printed paper may also be performed by the control unit 101. Alternatively, the adjustment values ​​calculated by the image analysis unit 180 may be transmitted to an external device (a controller or a server) via the communication unit 102, and the external device may generate a paper image including an image whose position on the paper has been adjusted according to the received adjustment values ​​and a margin, and transmit the image to the image forming apparatus 100. The image forming apparatus 100 may then print the received image as is without adjusting the position, thereby outputting a printed product whose image position has been adjusted. Alternatively, the communication unit 102 may transmit the measurement results of the distance between the paper edge and the register marks to an external device, and the external device may also calculate the adjustment values.

[0072] As described above, according to image forming apparatus 100, control unit 101 has, as operating modes for adjusting image position, a first adjustment mode in which the position of the image printed on paper by image forming unit 150 is adjusted before actual printing, and a second adjustment mode in which the position of the image printed on paper by image forming unit 150 is adjusted during actual printing, and when operating in the second adjustment mode, at least the magnification adjustment is restricted from being performed among the adjustment items performed in the first adjustment mode. Therefore, even if the cutting accuracy of the stack of paper used for printing is insufficient, it is possible to reduce the deviation in image magnification throughout the job, and to obtain good printing results with little deviation in the position of the image between the papers after cutting in the subsequent process.

[0073] In addition, the second adjustment mode has a first mode that does not restrict the implementation of magnification adjustment and a second mode that restricts the implementation of magnification adjustment, and is configured so that the user can select either the first mode or the second mode, so it is also possible to fit the image to the outline of the paper without implementing magnification restrictions.

[0074] In addition, the second adjustment mode limits the implementation of magnification adjustment, and further has a third mode that adjusts the difference between the front and back of the image printed on the front and back of the paper, so that even if the paper expansion / contraction rate changes during the job due to changes in the temperature inside the machine or the condition of the paper, it is possible to obtain print results with little difference between the front and back.

[0075] Furthermore, among the multiple adjustment modes included in the second adjustment mode, each of the adjustment modes that restrict the implementation of magnification adjustment is configured to allow selection between an adjustment mode that adjusts the position of an image so that the distance between the image printed on at least one side of the paper by image forming unit 150 and a specific edge of the paper is a predetermined distance, and an adjustment mode that adjusts the position of the image printed on the paper by image forming unit 150 so that the position of the image is located at the center of the paper. Therefore, by selecting an adjustment mode that adjusts the position of the image so that the distance from the specific edge is a predetermined distance, the relationship between the image position and the specific edge of the paper can be maintained throughout the job, facilitating the cutting process in the subsequent process. The image position can also be located at the center of the paper. Here, the aforementioned maintenance of the relationship between the image position and the specific edge of the paper may be configured to maintain a predetermined distance, or may be configured to maintain the relationship (distance) when printing is started in the second adjustment mode. The selection of this configuration may be predetermined, or may be based on the content set by means of a control panel or the like. In addition, in the above description, the magnification and image position are specifically described as control targets as examples of image position adjustment, but the present invention is not limited to these. For example, the rotational image position adjustment shown in Fig. 5B is usually adjusted so that there is no tilt relative to the outline of the paper that is approximated as a rectangle, but when the edge of the paper is identified, it may be configured to adjust so that there is no tilt relative to the edge of the paper.

[0076] Furthermore, when performing adjustment in the second adjustment mode, the control unit 101 calculates adjustment values ​​for at least two adjustment modes included in the second adjustment mode and stores them in the memory unit 104, making it easy to switch to another adjustment mode.

[0077] Furthermore, when the control unit 101 restricts the implementation of magnification adjustment in the second adjustment mode, it adjusts the position of the measurement pattern so that the distance between the measurement pattern printed on paper by the image forming unit 150 and the edge of the paper is larger than when the implementation of magnification adjustment is not restricted. Therefore, it is possible to prevent the measurement pattern from extending beyond the edge of the paper when the cutting accuracy of the paper stack is poor and the paper becomes smaller as the job progresses.

[0078] The description of the above embodiment is a preferred example of the image forming apparatus according to the present invention, and the present invention is not limited to this.

[0079] In the above description, examples have been disclosed in which a nonvolatile semiconductor memory or a hard disk is used as a computer-readable medium storing a program for executing each process, but this is not limiting. Other computer-readable media may also be portable recording media such as CD-ROMs. Furthermore, a carrier wave may also be used as a medium for providing program data via a communication line.

[0080] In addition, the detailed configuration and operation of each part of the image forming apparatus can be modified as appropriate without departing from the spirit of the present invention. [Explanation of symbols]

[0081] 100 Image forming device 101 Control section 102 Communications Department 103 Operation display section 104 Storage section 105 Paper feed section 106 Conveyor 110 Document reading unit 140 Image processing section 150 Image forming unit 160 Fixing unit 170 Output reading unit 180 Image Analysis Unit

Claims

[Claim 1] an image forming means for forming an image on a sheet; an image position adjusting means for adjusting the position of the image printed on the paper by the image forming means based on the positional relationship between the edge of the paper and the measurement pattern printed on the paper by the image forming means; An image forming apparatus comprising: The image position adjustment means adjusts the position of the image printed on the paper by the image forming means based on the positional relationship between only one of the opposing paper edges and the measurement pattern.

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