Image forming apparatus, image adjustment method, and program

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 Image adjustment method and program . [Background Art]

[0002] In the printing industry, it is common practice to print an image together with crop marks on a sheet of paper larger than the final product, and perform post-processing including cutting after printing. However, since printing paper is not always a rectangle of accurate dimensions, much labor has been expended on the process of cutting accurately at the crop mark positions during cutting work.

[0003] Therefore, for example, Patent Document 1 discloses a technology that facilitates cutting work by indicating an initial paper cutting position on a cut paper bundle and controlling the image position to be aligned with the opposite side. Patent Document 1 proposes a means for measuring distortion of an image based on the distance between the outer shape of the paper and a measurement pattern (register mark) for measuring the image position, and adjusting the image position through image deformation.

[0004] In addition, in order to sequentially measure and correct temporal image positional deviation during printing, a method (called real-time adjustment) is generally used in which register marks are printed at the four corners of the image to be printed, the distances between these register marks and the paper edges are measured, and adjustment is performed so that the distances between the paper edges and the register marks at the four corners are constant, thereby adjusting image positional deviation during printing. Real-time adjustment can appropriately respond to temporal changes of the image forming apparatus during continuous printing, and achieve favorable image positioning. [Prior Art Literature] [Patent Literature]

[0005] [Patent Document 1] Japanese Unexamined Patent Application Publication 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 relative positions of the paper edge and the crop marks at the four corners, there are generally no problems if the cutting accuracy of the paper stack used for printing is sufficient. However, if the cutting accuracy of the paper is poor, the relative positions of the paper edge and the crop marks at the four corners change "due to the paper" as printing progresses. Adjusting to stabilize this can change the image magnification, which can cause image position shifts during the post-processing cutting stage.

[0007] Figure 13A shows an image of a precisely cut stack of paper. As shown in Figure 13A, if the stack of paper is precisely cut into a rectangle, by continuously adjusting the distance between the paper edge and the crop marks at the four corners, the image can always be printed in a stable position, as shown in Figure 13B. In Figure 13B, the area inside the crop marks at the four corners is the image position. (The same applies to Figure 14B).

[0008] Figure 14A shows an example of an inaccurately cut stack of paper, where the paper size increases towards the bottom. As shown in Figure 14A, if the cutting 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 crop marks at the four corners is constant, as shown in Figure 14B, the image position relative to each paper edge will be stable, but the image magnification will change with the change in paper size. If the stack of paper is cut based on the position at the start of printing, the image position after cutting will change between the start of printing (using the paper at the top of the stack) and the end of printing (using the paper at the bottom of the stack). Also, when cutting, the paper printed at the end of printing will be cut at the position of the dotted line in Figure 14B, so the image may extend beyond the edge of the paper.

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

[0010] To solve the above problems, The image forming apparatus of the present invention is Image forming means for forming an image on paper, for Paper An image adjustment means adjusts the position and magnification of the image printed on the paper by the image forming means based on the positional relationship between the ledge and the measurement pattern printed on the paper by the image forming means, Equipped with 、 During printing, the image being printed by the image forming means is adjusted in real time by the image adjustment means. An image forming apparatus, The real-time adjustment has multiple modes, including a first mode for adjusting the magnification and position of the image, and a second mode for adjusting the position while limiting the magnification adjustment of the image. The second mode is, Based on the positional relationship between only one of a pair of opposing paper edges and the measurement pattern, the image forming means adjusts the position of the image printed on the paper. It is, One of the multiple modes of the aforementioned real-time adjustment can be selected. It is characterized by the following: [Effects of the Invention]

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

[0012] [Figure 1] This is a block diagram showing the functional configuration of an image forming apparatus. [Figure 2] This diagram shows the mechanical components of each part of an image forming apparatus. [Figure 3] This is a diagram to explain the background material. [Figure 4] This figure shows an example of registration marks printed in the first adjustment mode. [Figure 5A] This figure shows the range of adjustment values ​​and the adjustment image for each adjustment item: vertical magnification, horizontal magnification, vertical image shift, and horizontal image shift. [Figure 5B]It is a diagram showing the range of adjustment values and adjustment images for each of the adjustment items: rotation, skew, vertical trapezoid, horizontal trapezoid, curvature, and curvature position. [Figure 6] It is a diagram showing an example of a registration mark printed in the second adjustment mode. [Figure 7] In a conventional job subjected to real-time adjustment, it is a diagram showing printed matters at the job start time point and the job end time point when the paper size changes during the job and the paper size is larger at the job end time point than at the job start time point. [Figure 8A] It is a diagram showing printed matters at the job start time point and the job end time point when image position adjustment is performed in the edge reference mode of the second mode. [Figure 8B] It is a diagram showing printed matters at the job start time point and the job end time point when image position adjustment is performed in the center reference mode of the second mode. [Figure 9] It is a diagram showing an example where when image position adjustment is performed in the second mode, after an image is printed on the first side of a sheet to be printed first, the sheet expands or contracts, causing a deviation in magnification between the front and back images. [Figure 10A] It is a diagram showing printed matters at the job start time point and the job end time point when front-back position adjustment is performed in the edge reference mode of the third mode. [Figure 10B] It is a diagram showing printed matters at the job start time point and the job end time point when front-back magnification adjustment is performed in the edge reference mode of the third mode. [Figure 11] It is a flowchart showing the flow of setting processing executed by the control unit of FIG. 1. [Figure 12] It is a flowchart showing the flow of image position adjustment processing executed by the control unit of FIG. 1. [Figure 13A] It is a schematic diagram of a correctly trimmed paper stack. [Figure 13B] It is a diagram showing image positions at the start and end of printing when printing is performed while performing adjustment as needed so that the distance between the paper edge and the registration marks at the four corners is constant, using the paper stack shown in FIG. 13A. [Figure 14A]This is an illustration of a stack of paper, where the paper size increases as you go down the page. [Figure 14B] This figure shows the image positions at the start and end of printing when printing is performed using the paper stack shown in Figure 14A, while continuously adjusting the distance between the paper edge and the crop marks at the four corners to maintain a constant distance. [Modes for carrying out the invention]

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

[0014] [Configuration of the image forming apparatus] First, the configuration of the image forming apparatus 100 in this embodiment will be described. Figure 1 is a functional block diagram showing the functional configuration of each part of the image forming apparatus 100, and Figure 2 is a diagram showing the mechanical components of each part of the image forming apparatus 100.

[0015] As shown in Figure 1, the image forming apparatus 100 is configured to include a control unit 101, a communication unit 102, an operation display unit 103, a storage unit 104, a paper feeding unit 105, a transport 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), ROM (Read Only Memory), 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 works in cooperation with the loaded program to centrally control the operation of each part of the image forming apparatus 100.

[0017] The communication unit 102 is composed of a communication control card, such as a LAN (Local Area Network) card, and performs various data transmission and reception with external devices (such as a controller) connected to a communication network such as a LAN or WAN (Wide Area Network).

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

[0019] The storage unit 104 is composed of, for example, a non-volatile semiconductor memory (so-called flash memory) or a hard disk drive. The storage unit 104 stores various data, including various setting information related to the image forming apparatus 100, as well as job information (setting information and image data). For example, the storage unit 104 stores setting information related to the second adjustment mode set in the setting process described later (see Figure 11) (such as adjustment mode and registration mark position settings). The storage unit 104 also stores the adjustment values ​​for each adjustment item of image position adjustment (adjustment values ​​for the front and back sides).

[0020] The paper feeding unit 105 feeds paper from the paper tray according to instructions from the control unit 101. The transport unit 106 has a transport path and multiple transport roller pairs, such as a pair of registration rollers, and transports the paper fed from the paper feeding unit 105 within the image forming apparatus 100. The transport unit 106 also has a reversal mechanism 106a, which allows the paper to be transported to the image forming unit 150 with its front and back sides reversed.

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

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

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

[0024] The output reading unit 170 reads the image printed on the 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 located downstream of the image forming unit 150 and the fixing unit 160, and is configured to read images while the paper is being transported. The output reading unit 170 comprises a reading unit 170a that reads the image on one side of the paper, and a reading unit 170b that reads the image on the other side of the paper. Background members 171a and 171b are provided at positions opposite each other across the paper transport path, respectively, for reading unit 170a and reading unit 170b. The background members 171a and 171b have, for example, a black surface 1711 and a white surface 1712, as shown in Figure 3, and can be rotated by a drive source (not shown) to switch the background when reading the paper between black and white. Furthermore, the reading size of the output reading unit 170 is larger than the paper size, and it is configured to be able to read the edges on 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 position of the images to be printed on the front and back sides of the paper, and outputs them to the control unit 101.

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

[0027] The first adjustment mode is a mode in which the image forming unit 150 adjusts the position of the image to be printed on the paper before the actual print (before printing based on the job). Specifically, in the first adjustment mode, the image forming unit 150 first prints the measurement patterns (called registration marks) T1 to T4 shown in Figure 4, at a predetermined distance (for example, 10 mm from the paper edge) inward from the edges of all four sides of the paper on which the job will be printed, on both sides of the paper. The printed material 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 so that the distance between the paper edge and the registration marks T1 to T4 (registration marks facing each paper edge) becomes a predetermined distance for both the front and back sides, and stores these 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 printed materials with the aforementioned registration marks T1 to T4 may be printed, adjustment values ​​calculated for each, and the average value may be used. During printing, the control unit 101 controls the image processing unit 140, image forming unit 150, transport unit 106, etc., based on the adjustment values ​​stored in the storage unit 104 to adjust the position of the image printed on the paper.

[0028] In the first adjustment mode, several adjustment items are calculated, including the vertical and horizontal magnification, vertical and horizontal image shift, rotation, skew, vertical trapezoidal distortion, horizontal trapezoidal distortion, curvature, and curvature position. Each of these adjustment items can be adjusted independently. By adjusting the magnification, image shift, rotation, skew, vertical trapezoidal distortion, and horizontal trapezoidal distortion items, the image position at the four corners can be adjusted. Furthermore, curvature and curvature position are used to adjust image distortion, and by using these in combination, more advanced image position adjustments are possible.

[0029] Figure 5A shows the range of adjustment values ​​and adjustment images for each adjustment item: vertical magnification, horizontal magnification, vertical image shift, and horizontal image shift. Figure 5B shows the range of adjustment values ​​and adjustment images for each adjustment item: rotation, skew, vertical trapezoid, horizontal trapezoid, curve, and curve position. In Figures 5A and 5B, the thick arrow A 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 the adjustment. Note that for the image shift in Figure 5A, showing both the current image position and the target image position would make it difficult to read, so they are represented as the same, and only the direction in which the image moves due to the adjustment is shown. Also, in Figure 5B, the solid line representing the paper is omitted.

[0030] In this embodiment, the first adjustment mode is described as automatically obtaining the adjustment values ​​for each adjustment item shown in Figures 5A and 5B by reading the paper on which registration marks T1 to T4 are printed with the output reading unit 170 and analyzing the obtained read image data with the image analysis unit 180. However, it is also possible to obtain the adjustment values ​​for each adjustment item by receiving input from the operation display unit 103, which is determined by the user visually observing the paper on which registration marks T1 to T4 are printed. Alternatively, the document reading unit 110 may be configured to read and analyze the paper on which registration marks T1 to T4 are printed. In this case, since the document reading unit 110 is designed for copying purposes, the background will be white. For this purpose, in order to clearly read the paper edge, for example, a dark-colored background paper may be placed on top of the paper on which registration marks T1 to T4 are printed, and the front and back, top and bottom of the printed paper may be reversed and read and analyzed as appropriate (for example, 4 times) so that the paper edge can be read properly.

[0031] The second adjustment mode is a mode in which the image forming unit 150 adjusts the position of the image printed on the paper during the actual printing process (a so-called real-time adjustment mode). Specifically, in the second adjustment mode, first, the image forming unit 150 prints the registration marks T11 to T14 shown in Figure 6 onto the four corners of the paper on which the job will be printed, at a predetermined distance (for example, 3 mm from each of the two paper edges that make up the four corners of the paper) from the four corners of the paper. The printed material 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 registration marks T11 to T14 (registration marks facing each paper edge). The image analysis unit 180 then calculates and updates the adjustment values ​​for each adjustment item to be acquired based on the acquired distance between the paper edge and the registration 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 transport unit 106, etc., to adjust the position of the image to be printed on the paper in subsequent printing. The reason the previously mentioned preset distance is smaller in the second adjustment mode is that the second adjustment mode utilizes the user content image printed together with the registration marks T11-T14, and this is to prevent the user content from overlapping with the registration marks T11-T14. In addition, auxiliary information, such as that used by the printing operator to check printing conditions, is often printed near the edges of the paper. If this overlaps with the registration marks T11-T14, the second adjustment mode may not function correctly, so it is advisable to add a process to white out (prevent toner printing) the image information around the registration marks.

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

[0033] In conventional image forming apparatuses, real-time adjustments performed during printing involved adjusting the image position 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 printed output at the start of the job (start of printing) and the end of the job (end of printing) in a job where the paper size changed during the job due to inaccurate cutting of the paper stack used for printing, resulting in the paper size being larger at the end of the job than at the start. The dotted line on the printed output 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 printed output from the job, an image based on the job is printed inside the registration marks T11 to T14, but this is omitted in Figures 7 to 10B for simplification.

[0035] As mentioned above, in conventional real-time adjustment, the image magnification is adjusted so that the distance between the paper edge and the crop marks at the four corners remains constant. Therefore, if the paper size changes during the job, the image size will change accordingly, as shown in Figure 7. In that case, for example, if the stack of printed paper is cut based on the position at the start of the job, problems such as the image being cut off in the printed material at the end of the job may occur.

[0036] Therefore, the second adjustment mode of this embodiment includes a first mode that performs adjustments equivalent to conventional real-time adjustments, a second mode that restricts magnification adjustments, and a third mode that restricts magnification adjustments and adjusts the front-to-back difference caused by restricting magnification adjustments. Furthermore, each of the second and third modes is configured so that the operation display unit 103 can select either an edge-reference mode, which adjusts the position of the image so that the distance between the image printed on at least one side of the paper and a specific paper edge is a predetermined distance, or a center-reference mode, which adjusts the position of the image so that the position of the image printed on the paper is located in the center of the paper.

[0037] Figure 8A shows the printouts at the start and end of a job when image position adjustment is performed using the second mode's edge-reference mode. In Figure 8A, edges E1 and E4 are set as specific paper edges. In the second mode, edge-reference mode, magnification adjustment is limited, and the image position is adjusted to be at a predetermined distance from specific paper edges (E1, E4 in Figure 8A). Therefore, if the post-processing is set up to cut the edges (E3, E2) opposite to the specific paper edges, as shown in Figure 8A, the image position in the printed material at the start and end of the job can be easily aligned.

[0038] Figure 8B shows the printed materials at the start and end of a job when image position adjustment is performed using the second mode's central reference mode. In the second mode, the central reference mode, the magnification adjustment is limited, and the image position is adjusted so that the image is evenly spaced from each edge of the paper. As shown in Figure 8B, the image can be positioned in the center of the paper. For example, if there is no subsequent trimming process and the image size needs to be finished to a specified standard, adjusting the image position in this adjustment mode may be preferable.

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

[0040] In the third mode, there are two methods for adjusting the difference between the front and back sides of the paper: one is to adjust the image magnification of the image printed later on the paper by using the image printed first on the image printed first as a reference in the image forming unit 150 (called front-to-back magnification adjustment); and the other is to adjust the position of the image printed later on the paper to a position where the positional misalignment of the image printed later on the image printed first is minimized on average at the four corners (called front-to-back position adjustment). The user can select which adjustment method to adopt using the operation display unit 103.

[0041] Figure 10A shows the printed materials at the start and end of the job when front-to-back position adjustment is performed in the third mode, edge-reference mode. Figure 10B shows the printouts at the start and end of the job when front and back magnification adjustment is performed in the third mode, edge-reference mode. As shown in Figures 10A and 10B, in the third mode, even if the paper expands or contracts between printing on the front and back sides, the relative position of the images on the front and back sides can be maintained in good condition.

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

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

[0044] First, the control unit 101 displays a selection button on the operation display unit 103 for selecting whether or not to restrict the performance of magnification adjustment. If the user selects the button to not restrict the performance of magnification adjustment through 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 terminates the setting process.

[0045] In step S1, if the user selects a selection button on the operation display unit 103 to restrict the performance of magnification adjustment (step S1; YES), the control unit 101 displays a selection button on the operation display unit 103 to select whether or not to perform front-to-back difference adjustment. If the user selects a selection button on the operation display unit 103 to not perform front-to-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] If the user selects the button on the operation display unit 103 to perform front-to-back difference adjustment (step S3; YES), the control unit 101 displays a selection button on the operation display unit 103 to select whether or not to perform front-to-back magnification adjustment. If the user selects the button on the operation display unit 103 to not perform front-to-back magnification adjustment (step S5; NO), the control unit 101 sets the adjustment mode to the third mode (front-to-back position adjustment) (step S6) and proceeds to step S8. When the user selects the button on the operation display unit 103 to perform front / back magnification adjustment (step S5; YES), the control unit 101 sets the adjustment mode to the third mode (front / back magnification adjustment) (step S7) and proceeds to step S8.

[0047] In step S8, the control unit 101 displays a selection button on the operation display unit 103 for the user to choose whether or not to adjust the registration mark position. If the user selects the selection button to adjust the registration mark position by operating the operation display unit 103 (step S8; YES), the control unit 101 sets the registration mark position for the second adjustment mode to be a predetermined distance away from the paper edge from the preset reference position (step S9), and proceeds to step S11. If the user selects the button on the operation display unit 103 to select not to adjust the registration mark position (step S8; NO), the control unit 101 sets the registration mark position for 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 a selection button on the operation display unit 103 for selecting whether or not to align the image position to a specific paper edge. If the user selects the selection button to align the image position to a specific paper edge by operating the operation display unit 103 (step S11; YES), the control unit 101 adds the edge reference mode to the currently set adjustment mode (step S12) and terminates the setting process. If the user selects a button on the operation display unit 103 to select not to align the image position to a specific paper edge (step S11; NO), the control unit 101 adds the central reference mode to the currently set adjustment mode (step S13) and terminates the setting process.

[0049] Furthermore, the control unit 101 can automatically set specific paper edges, for example, according to the printing settings, paper path, and post-printing processes. For example, if, after printing, there are two types of output: face-up, where the first page is ejected with the top face up, and face-down, where the first page is ejected with the bottom face up, and the face-up / face-down switching control is performed after the output reading unit 170 has fed the paper, then if a specific paper edge direction (edge) is set for the convenience of the subsequent process, the direction of that specific paper edge in the image read by the output reading unit 170 will differ depending on the face-up / face-down setting. Furthermore, if an online paper cutter, stapler, or binding machine such as a saddle binder is installed in the subsequent process, 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 sets the specific paper edge according to the configuration of the subsequent device.

[0050] Furthermore, while the above-described setting process was explained using the example of a user making various settings related to image position adjustment on the control panel, the image position adjustment setting function could also be provided on a screen restricted to administrators, allowing only administrators to make the settings. Alternatively, a service technician performing maintenance on the image forming apparatus 100 could open a dedicated maintenance mode screen to make the settings. Or, the settings could be made using a mechanical or electrical mechanism such as a DIP switch.

[0051] The following describes the image position adjustment process executed by the control unit 101 based on the settings made during the above setup process. Figure 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 the image position adjustment set and printing is instructed to start.

[0052] First, the control unit 101 performs image position adjustment for both the front and back sides in the first adjustment mode (step S21). The image position adjustment for the first adjustment mode is as described above, so we will refer to that explanation. Furthermore, the control unit 101 switches the black side 1711 or the white side 1712 of the background members 171a and 171b that are placed opposite the paper in the output reading unit 170, depending on the color of the paper being used (for white paper, the black side 1711 is placed opposite; for black paper, the white side 1712 is placed opposite; and for other paper colors, an appropriate color of background member that is easy to read or read is selected. In the case of black paper, the registration marks printed on the paper may also be made of a colorant that can be easily distinguished from the paper, such as white toner), so that the four edges of the paper 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] In other words, the control unit 101 first adds registration marks T11 to T14 to the margins of the image on the page to be printed, for measuring the distance from the edge of the paper (step S23). Here, the control unit 101 assigns the registration marks T11 to T14 based on the registration mark position setting information stored in the memory unit 104.

[0055] Next, the control unit 101 controls the image processing unit 140, image forming unit 150, transport unit 106, etc., based on the adjustment values ​​of each adjustment item stored in the memory unit 104 to adjust the position of the image to be printed on the paper, print the image with registration marks T11 to T14 onto the paper, and fix it with the fuser unit 160 (step S24). In the case of double-sided printing, the control unit 101 controls the transport unit 106 and the image forming unit 150 to perform double-sided printing.

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

[0057] Next, the control unit 101 analyzes the read image data acquired by the output reading unit 170 using the image analysis unit 180 to obtain the distance between the paper edge and the registration marks T11 to T14 (step S26).

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

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

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

[0061] For example, if the adjustment mode is set to the third mode (front / back position adjustment), first, the adjustment values ​​for image shift, rotation, skew, vertical trapezoid, and horizontal trapezoid adjustment items are calculated so that the position of the registration marks T11-T14 on the first printed side facing a specific paper edge is at a predetermined distance from that specific paper edge, and these adjustment values ​​are updated in the storage unit 104. Magnification adjustment is not performed. Next, the adjustment values ​​for image shift, rotation, skew, vertical trapezoid, and horizontal trapezoid adjustment items are calculated so that the positional misalignment between the registration marks T11-T14 on the second printed side and the adjusted registration marks T11-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 the adjustment mode where magnification adjustment is not restricted, the adjustment values ​​for magnification, image shift, rotation, skew, vertical trapezoidal distortion, and horizontal trapezoidal distortion are calculated. In the adjustment mode where magnification adjustment is restricted, the adjustment values ​​for image shift, rotation, skew, vertical trapezoidal distortion, and horizontal trapezoidal distortion are calculated. However, adjustment items with small deviations may be omitted. Furthermore, the system may be configured so that the user can set which adjustment items' adjustment values ​​are calculated from the operation display unit 103.

[0063] In the second adjustment mode, the printed sheet is read to measure the distance between the registration marks T11-T14 and the paper edge, and an adjustment value is calculated based on the measurement result. This calculated adjustment value is then applied to the image to be printed. As a result, a delay of several to several dozen sheets of paper occurs between the print used for measurement and the print 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 over-adjustment.

[0064] Furthermore, when calculating each adjustment value, it is preferable for the image analysis unit 180 to store the adjustment values ​​from the most recent multiple adjustments (for example, 20 adjustments), and to calculate the adjustment value taking into account the trend using the adjustment value calculated based on the currently read image data and the adjustment values ​​from the most recent multiple adjustments. This can improve the accuracy of the adjustment.

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

[0066] The following describes variations of the image position adjustment process described above. [Variation 1] The flowchart in Figure 12 illustrates the case where adjustments are made in the first adjustment mode before job execution. However, adjustments in the first adjustment mode only need to be made before job execution immediately after changing the paper stack; it is not necessary to perform the first adjustment mode before every job execution. However, if the user reconfigures the mode settings in the second adjustment mode between jobs, and has only updated the adjustment values ​​by adjusting the previously set adjustment mode, the adjustment values ​​for the newly set adjustment mode will not be retained. Therefore, it will be necessary to reset the adjustment values ​​and reconfigure in the first adjustment mode before starting the next job. To avoid this and to enable a smooth switch to the second adjustment mode without performing adjustments in the first adjustment mode, it is preferable that in the second adjustment mode, the image analysis unit 180 calculates adjustment values ​​for at least two adjustment modes in parallel and stores them in the storage unit 104. For example, the calculation of adjustment values ​​for the adjustment mode set by the user and the calculation of adjustment values ​​for the first mode without magnification adjustment restrictions are performed in parallel and each adjustment value is stored in the storage unit 104. Alternatively, the adjustment modes to be calculated in parallel can be set from the operation display unit 103, and the adjustment values ​​for the set adjustment mode can be calculated and stored in parallel with the adjustment values ​​for the actual adjustment mode. In this case, the print result obtained when the adjustment value is updated is only available for the currently set adjustment mode. Therefore, the adjustment value for the adjustment mode that calculates the adjustment value in parallel should be calculated as the difference between that value and the adjustment value of the currently set adjustment mode, and updated accordingly.

[0067] [Variation 2] If a cutting process is performed in a subsequent step, it is preferable that the cutting position can be easily adjusted. If the image position is adjusted by the above image position adjustment process so that the image is placed at a predetermined distance from a specific paper edge, cutting the side opposite the specific paper edge first makes it easier to handle and cut the paper even if there are variations in the paper size of the stack of printing paper. Here, when performing the cutting process, the user needs to correctly understand the direction of a specific paper edge. Therefore, in the image position adjustment process described above, for example, to make it easy to identify the direction (edge) to be cut first, the design of the trim marks for the direction (edge) to be cut first may be changed, a specific mark may be added, or a sheet with post-processing information indicating the cutting direction and cutting method may be printed and overlaid on the top surface of the print job stack, separate from the actual printed materials based on the job. Furthermore, control may be combined to send post-processing information from the image forming apparatus 100 to a display device installed in front of the cutting machine, or to send post-processing information from the image forming apparatus 100 to a display device installed in front of the cutting machine via a server.

[0068] [Example 3] In the above embodiment, the image position was described as being adjusted by defining a specific paper edge and adjusting the distance between that edge and the registration mark. However, the same processing result can be obtained by defining a specific registration mark and adjusting the distance between the paper edge and the registration mark in relation to the paper edge closest to it. Alternatively, paper edges and registration marks that are not used for adjusting the distance between the paper edge and the registration mark may be identified.

[0069] [Variation 4] In the image position adjustment of the above embodiment, other correction processes such as conventional bias correction may be used in combination, for example, by detecting the paper feeding position before printing and calculating and adjusting the amount of bias correction for the paper position and printed image based on the detected information. For example, a sensor is provided to read the paper feeding position of the paper edge before printing, and a mechanism is generally used to correct the bias of the paper just before printing based on the result. However, if the sensor detects only one side of the paper edge (for example, the front side), the image position can be expected to be controlled more stably with respect to the front side of the paper edge. In such cases, the system may be configured to set the edge side read by the sensor as the specific paper edge, or to display a message on the operation screen recommending that this setting be used. Similarly, if there is a separate mechanism to regulate the paper position, the paper edge in which the relationship between the image position and the paper edge is more stable under that regulation can be set or recommended as the specific paper edge.

[0070] [Variation 5] In the image forming apparatus 100 of the above embodiment, the second adjustment mode is configured to have multiple adjustment modes, and the user is given the option to select which adjustment mode to use for the adjustment. However, only one of these adjustment modes may be incorporated into the image forming apparatus.

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

[0072] As described above, the image forming apparatus 100 has two operating modes for image position adjustment: a first adjustment mode in which the image forming unit 150 adjusts the position of the image to be printed on the paper before the actual printing, and a second adjustment mode in which the image forming unit 150 adjusts the position of the image to be printed on the paper during the actual printing. When operating in the second adjustment mode, the control unit 101 restricts the implementation of at least the magnification adjustment among the adjustment items performed in the first adjustment mode. Therefore, even if the cutting precision of the paper stack used for printing is insufficient, it is possible to reduce image magnification shifts throughout the job and obtain good printing results with less image misalignment between cut sheets in subsequent processes.

[0073] Furthermore, the second adjustment mode has a first mode that does not restrict magnification adjustment and a second mode that does restrict magnification adjustment, and the user can select either the first or second mode, making it possible to adjust the image to fit the paper's outline without imposing magnification restrictions.

[0074] Furthermore, the second adjustment mode restricts the implementation of magnification adjustments and has a third mode that adjusts the difference between the front and back of the image printed on both sides of the paper. Therefore, even if the paper expansion / contraction rate changes due to changes in the machine temperature or paper condition during the job, it is possible to obtain print results with less 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 restricts the implementation of magnification adjustment is configured to allow selection of either an adjustment mode in which the image forming unit 150 adjusts the position of the image so that the distance between the image printed on at least one side of the paper and a specific edge of the paper is a predetermined distance, or an adjustment mode in which the image forming unit 150 adjusts the position of the image so that the position of the image printed on the paper is located in the center of the paper. Therefore, by selecting the adjustment mode in which the position of the image adjusts the distance from the specific edge to a predetermined distance, the relationship between the image position and the specific edge of the paper can be maintained throughout the job, making subsequent cutting processes easier. It is also possible to position the image in the center of the paper. Here, the maintenance of the relationship between the image position and a specific edge of the paper, as described above, may be configured to maintain a predetermined distance, or it may be configured to maintain the relationship (distance) when printing was started in the second adjustment mode. This configuration may be predetermined, or it may be set according to the settings made by means of an operation panel or the like. Furthermore, while the above description specifically described magnification and image position as control targets for image position adjustment, the present invention is not limited to these. For example, the rotational image position adjustment shown in Figure 5B is usually adjusted so that there is no tilt with respect to the rectangular outline of the paper, but it may also be configured to adjust so that there is no tilt with respect to the edge of the paper when the edge of the paper is identified.

[0076] Furthermore, when the control unit 101 performs adjustments in the second adjustment mode, it calculates the adjustment values ​​for at least two adjustment modes included in the second adjustment mode and stores them in the storage 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 the paper by the image forming unit 150 and the edge of the paper is greater than when the implementation of magnification adjustment is not restricted. Therefore, if the cutting accuracy of the paper stack is poor and the paper gets smaller as the job progresses, it is possible to prevent the measurement pattern from extending beyond the edge of the paper.

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

[0079] Furthermore, while the above description discloses examples using non-volatile semiconductor memory or hard disks as computer-readable media for storing programs to execute each process, the invention is not limited to these examples. Portable recording media such as CD-ROMs can also be used as other computer-readable media. In addition, a carrier wave may be used as the medium for providing program data via a communication line.

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

[0081] 100 Image forming apparatus 101 Control Unit 102 Communications Department 103 Operation display section 104 Storage section 105 Paper feed section 106 Conveying section 110 Manuscript Reading Unit 140 Image Processing Unit 150 Image forming unit 160 Fixing section 170 Output reading unit 180 Image Analysis Department

Claims

1. Image forming means for forming an image on paper, An image adjustment means adjusts the position and magnification of the image printed on the paper by the image forming means based on the positional relationship between the paper edge and the measurement pattern printed on the paper by the image forming means, Equipped with, An image forming apparatus that performs real-time adjustments during printing, adjusting the image printed by the image forming means using the image adjustment means, The real-time adjustment has multiple modes, including a first mode for adjusting the magnification and position of the image, and a second mode for adjusting the position while limiting the magnification adjustment of the image. The second mode adjusts the position of the image printed on the paper by the image forming means based on the positional relationship between only one of a pair of opposing paper edges and the measurement pattern. An image forming apparatus characterized by allowing selection of one of several modes of real-time adjustment.

2. The image forming apparatus according to claim 1, characterized in that the first mode is adjusted so that the distance between the paper edge and the measurement pattern is a predetermined distance.

3. The opposing paper edges are a pair of paper edges that face each other in the paper transport direction, The image forming apparatus according to claim 1, characterized in that the image adjustment means adjusts the position of the image printed on the paper by the image forming means in the second mode based on the positional relationship between only one of a pair of paper edges facing each other in the paper transport direction and the measurement pattern.

4. The opposing paper edges are a pair of paper edges that face each other in a direction perpendicular to the paper transport direction, The image forming apparatus according to claim 1, characterized in that the image adjustment means adjusts the position of the image printed on the paper by the image forming means in the second mode based on the positional relationship between only one of a pair of opposing paper edges in a direction perpendicular to the paper transport direction and the measurement pattern.

5. The opposing paper edges include a pair of paper edges that face each other in the paper transport direction and a pair of paper edges that face each other in a direction perpendicular to the paper transport direction, The image forming apparatus according to claim 1, characterized in that the image adjustment means adjusts the position of the image printed on the paper by the image forming means in the second mode, based on the positional relationship between only one of a pair of opposing paper edges in the paper transport direction and the measurement pattern, and the positional relationship between only one of a pair of opposing paper edges in a direction perpendicular to the paper transport direction and the measurement pattern.

6. The image forming apparatus according to claim 1, characterized in that the position adjustment by the image adjustment means includes adjustment of at least one item of image shift, rotation, skew, vertical trapezoid, and horizontal trapezoid.

7. The image forming apparatus according to claim 1, characterized in that the magnification adjustment by the image adjustment means includes at least one adjustment of magnification in the paper transport direction and magnification in a direction perpendicular to the paper transport direction.

8. A reading means for reading a sheet of paper on which an image has been formed by the image forming means, An image analysis unit analyzes the read image data obtained by the reading means to acquire the positional relationship, The image forming apparatus according to claim 1, further comprising the following:

9. The image forming apparatus according to claim 1, wherein the second mode adjusts the position of the image such that the distance between the image printed on at least one side of the paper and a specific paper edge is a predetermined distance.

10. The second mode includes an edge reference mode that adjusts the position of an image so that the distance between the image printed on at least one side of the paper and a specific paper edge is a predetermined distance, and a center reference mode that adjusts the position of an image so that the position of the image printed on the paper is located in the center of the paper, The image forming apparatus according to claim 1, characterized in that one of the edge-referenced mode and the central-referenced mode can be selected.

11. The image forming apparatus according to claim 1, characterized in that the real-time adjustment is selectable from one of a plurality of modes, which include the first mode, the second mode, and the third mode, which performs position adjustment with limited magnification adjustment of the image and adjustment of the difference between the front and back of the image printed on the front and back of the paper.

12. The image forming apparatus according to claim 11, characterized in that the adjustment of the front-to-back difference in the third mode is adjusted by the image forming means to match the magnification of the image of the side printed later with respect to the image of the side printed first.

13. The image forming apparatus according to claim 11, characterized in that the adjustment of the front-to-back difference in the third mode is performed by adjusting the position of the image on the later printed surface in the image forming means to a position in which the positional displacement of the image on the later printed surface with respect to the image on the first printed surface is minimized on average at the four corners.

14. The image forming apparatus according to claim 11, characterized in that the adjustment of the front-to-back difference in the third mode is made by selecting one of the following: front-to-back magnification adjustment, which adjusts the magnification of the image on the later printed surface to match the magnification of the image on the first printed surface with respect to the image on the first printed surface; and front-to-back position adjustment, which adjusts the position of the image on the later printed surface to a position where the positional misalignment of the image on the later printed surface with respect to the image on the first printed surface is minimized on average at the four corners.

15. The image forming apparatus according to any one of claims 1 to 14, wherein performing position adjustment while restricting the magnification adjustment of the image means performing position adjustment without performing magnification adjustment of the image.

16. The image forming apparatus according to claim 15, characterized in that the selection of the mode is performed in accordance with the operation of the user.

17. An image forming means for forming an image on paper, An image adjustment means adjusts the position and magnification of the image printed on the paper by the image forming means based on the positional relationship between the paper edge and the measurement pattern printed on the paper by the image forming means, Equipped with, An image adjustment method in an image forming apparatus that performs real-time adjustment of an image printed by the image forming means during printing, wherein the image adjustment means adjusts the image being printed by the image forming means, The real-time adjustment has multiple modes, including a first mode for adjusting the magnification and position of the image, and a second mode for adjusting the position while limiting the magnification adjustment of the image. The second mode adjusts the position of the image printed on the paper by the image forming means based on the positional relationship between only one of a pair of opposing paper edges and the measurement pattern. An image adjustment method characterized by allowing selection of one of several modes of the aforementioned real-time adjustment.

18. A computer for an image forming apparatus that includes an image forming means for forming an image on paper, Image adjustment means adjusts the position and magnification of the image printed on the paper by the image forming means based on the positional relationship between the paper edge and the measurement pattern printed on the paper by the image forming means. Control means for performing real-time adjustments to adjust the image printed by the image forming means during printing, using the image adjustment means. To make it function as, The real-time adjustment has multiple modes, including a first mode for adjusting the magnification and position of the image, and a second mode for adjusting the position while limiting the magnification adjustment of the image. The second mode adjusts the position of the image printed on the paper by the image forming means based on the positional relationship between only one of a pair of opposing paper edges and the measurement pattern. A program characterized by allowing selection of one of several modes of real-time adjustment.

Images