Image forming apparatus and image position adjustment method

Abstract

To provide an image forming apparatus and an image position adjustment method that, even when a sheet bundle used for printing is not cut with sufficient accuracy, can obtain a good printing result with the reduced positional deviation between images on 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 position of 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 has a first adjustment mode for adjusting 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 the opposing sheet edges, of the edges of the sheet, and a second adjustment mode for adjusting the position on the sheet printed by the image forming means on the basis of the positional relationship between the measurement patterns and one of the opposing sheet edges.SELECTED DRAWING: Figure 12

Description

Technical Field

[0001] The present invention relates to an image forming apparatus and an image position adjustment method.

Background Art

[0002] In the printing industry, it has been practiced to print an image together with cutting marks on a sheet of paper larger than the final product, and to perform post-processing including cutting after printing. However, since the printing paper is not necessarily a rectangle with an exact size, a great deal of labor has been required for the process of accurately cutting at the cutting mark position during the cutting operation.

[0003] Therefore, for example, Patent Document 1 discloses a technique that enables easy execution of a cutting operation by indicating the first paper cutting position on a stack of cut papers and performing control to align the image position with the side opposite thereto. This Patent Document 1 proposes a means for measuring the distortion of an image based on the distance between the outer shape of the paper and a measurement pattern (mark) for measuring the image position, and adjusting the image position due to image deformation.

[0004] Also, in order to sequentially measure and correct the positional deviation of an image over time during printing, marks are printed at the four corners of the image to be printed, the distance between these and the paper edge (paper end) is measured, and adjustment is made so that the distances between the paper edge and the marks at the four corners are constant, thereby adjusting the positional deviation of the image during printing (referred to as real-time adjustment). By real-time adjustment, it is possible to appropriately respond to changes over time in an image forming apparatus during continuous printing and achieve good image alignment.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] As described above, when performing image position adjustment based on the positional relationship between the paper edge and the four-corner pins, if the cutting accuracy of the paper bundle used for printing is sufficient, there is no particular problem. However, when the cutting accuracy of the paper is poor, the positional relationship between the paper edge and the four-corner pins "due to the paper" changes as the printing progresses. When adjusting to stabilize this relationship, the image magnification changes, and image position misalignment may occur in the post-processing cutting step.

[0007] FIG. 13A shows an image diagram of a paper bundle accurately cut. For a paper bundle accurately cut into a rectangle as shown in FIG. 13A, by performing adjustment at any time so that the distances between the paper edge and the four-corner pins are constant, as shown in FIG. 13B, an image can always be printed at a stable image position. Note that in FIG. 13B, the inside of the four-corner pins is the image position. (The same applies to FIG. 14B).

[0008] FIG. 14A shows an image diagram of a paper bundle with inaccurate cutting, specifically, a paper bundle in which the paper size increases as it goes down. As shown in FIG. 14A, when the cutting state of the paper bundle used for printing is distorted, the paper size changes as printing progresses. In this case, when adjusting the image position so that the distances between the paper edge and the four-corner pins are constant, as shown in FIG. 14B, although the image positions with respect to each paper edge are stable, the image magnification changes as the paper size changes. When cutting the printed paper bundle with reference to the position at the start of printing, the image position after cutting changes between the start point of printing (using the paper at the upper part of the paper bundle) and the end point of printing (using the paper at the lower part of the paper bundle). Also, when cutting, since the paper printed at the end of printing is cut at the position of the dotted line in FIG. 14B, the image may protrude from the paper.

[0009] An object of the present invention is to provide an image forming apparatus and an image position adjustment method that can obtain a good printing result with less image position misalignment between the papers after cutting in a post-process even when the cutting accuracy of the paper bundle used for printing is not sufficient.

Means for Solving the Problem

[0010] In order to solve the above problems, the invention according to claim 1 is image forming means for forming an image on a sheet; image position adjusting means for adjusting the position of an image printed on a sheet by the image forming means based on the positional relationship between an edge of the sheet and a measurement pattern printed on the sheet by the image forming means; An image forming apparatus comprising: The image position adjusting means includes a first adjustment mode for adjusting the position of an image printed on a sheet by the image forming means based on the positional relationship between each of the opposing edges of the sheet and the measurement pattern, and a second adjustment mode for adjusting the position of an image printed on a sheet by the image forming means based on the positional relationship between one of the opposing sheet edges and the measurement pattern.

[0011] The invention according to claim 2 is the invention according to claim 1, wherein In the second adjustment mode, the image position adjusting means adjusts the position of an image printed on a sheet by the image forming means based on one of the opposing sheet edges in a direction parallel to the sheet conveyance direction and one of the opposing sheet edges in a direction perpendicular to the sheet conveyance direction.

[0012] The invention according to claim 3 is the invention according to claim 1 or 2, wherein In the first adjustment mode, the measurement pattern is formed so as to be at a predetermined distance from each of the opposing edges of the sheet.

[0013] The invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein In the second adjustment mode, the measurement pattern is formed so as to be at a predetermined distance from one of the opposing sheet edges.

[0014] The invention according to claim 5 is the invention according to any one of claims 1 to 4, wherein In the first adjustment mode, the image position adjustment means further adjusts the magnification of the image printed on the paper based on the positional relationship between each edge of the opposing paper and the measurement pattern.

[0015] The invention according to claim 6 is the invention according to any one of claims 1 to 5, In the second adjustment mode, when printing images on both sides of the paper, the image position adjustment means adjusts the front-back difference of the image on the other side printed later with reference to the image on one side printed first.

[0016] The invention according to claim 7 is An image position adjustment method for adjusting the position of an image printed on a paper by an image forming means based on the positional relationship between an edge of the paper and a measurement pattern printed on the paper by the image forming means, Among the edges of the paper, a first adjustment mode for adjusting the position of the image printed on the paper by the image forming means based on the positional relationship between each edge of the opposing paper and the measurement pattern, and a second adjustment mode for adjusting the position of the image printed on the paper by the image forming means based on the positional relationship between one of the opposing paper edges and the measurement pattern are included.

Advantages of the Invention

[0017] According to the present invention, even when the cutting accuracy of the paper bundle used for printing is not sufficient, it is possible to provide an image forming apparatus and an image position adjustment method that can obtain a good printing result with less positional deviation of the images between the papers after cutting in a subsequent process.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5A

Figure 5B

Figure 6

Figure 7

Figure 8A

Figure 8B

Figure 9

Figure 10A

Figure 10B

Figure 11

Figure 12

Figure 13A

Figure 13B

Figure 14A

Figure 14B

DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the scope of the invention is not limited to the illustrated examples.

[0020] 〔Configuration of Image Forming Apparatus〕 First, the configuration of the image forming apparatus 100 in the present embodiment will be described. FIG. 1 is a functional block diagram showing the functional configuration of each part of the image forming apparatus 100, and FIG. 2 is a diagram showing the mechanical components of each part of the image forming apparatus 100.

[0021] As shown in FIG. 1, the image forming apparatus 100 includes a control unit 101, a communication unit 102, an operation display unit 103, a storage unit 104, a paper feeding unit 105, a conveyance unit 106, an original 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.

[0022] 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 and expands it in the RAM, and centrally controls the operations of each part of the image forming apparatus 100 in cooperation with the expanded program.

[0023] The communication unit 102 is composed of a communication control card such as a LAN (Local Area Network) card, etc., and is connected to an external device (such as a controller) to transmit and receive various data.

[0024] 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 overlaid on the screen of the display device. The operation display unit 103 causes the display device to display various information, and converts a user's input operation on the input device into an operation signal and outputs it to the control unit 101.

[0025] The storage unit 104 is composed of, for example, 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, and information (setting information and image data) of jobs (Jobs). For example, the storage unit 104 stores each setting information (adjustment mode, thumb position setting, etc.) related to the second adjustment mode set in the setting process (see FIG. 11) described later. In addition, the storage unit 104 stores adjustment values (adjustment values for the front and back respectively) of each adjustment item for image position adjustment.

[0026] The paper feeding unit 105 feeds the paper stored in the paper feed tray according to an instruction from the control unit 101. The conveyance unit 106 has a plurality of conveyance roller pairs such as a conveyance path and a registration roller pair, and conveys the paper fed from the paper feeding unit 105 within the image forming apparatus 100. In addition, the conveyance unit 106 has a reversing mechanism 106a and can reverse the front and back of the paper and convey it to the image forming unit 150.

[0027] The original document reading unit 110 is configured to include an automatic document feeder called ADF (Auto Document Feeder) and an original document image scanning device (scanner), etc., reads the image of the original document, and generates image data.

[0028] Under the control of the control unit 101, the image processing unit 140 performs various image processes such as image position adjustment, gradation correction, color conversion, and shading correction, as well as compression processing, on the image data read by the original document reading unit 110 or the image data input from an external device (for example, a PDL controller or the like that rasterizes the PDL data transmitted from a PC (Personal Computer)). The image data subjected to these processes is input to the image forming unit 150. The image forming unit 150 prints an image on a sheet based on the job setting information and the image data.

[0029] The fixing unit 160 fixes the toner image printed on the sheet to the sheet using heat and pressure. Note that in FIG. 2, the image forming unit 150 is illustrated as an electrophotographic image forming unit, but is not limited thereto, and may be, for example, an inkjet image forming unit.

[0030] The output reading unit 170 reads the image printed on the sheet 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 on the downstream side of the image forming unit 150 and the fixing unit 160, and is configured to read the image during sheet conveyance. The output reading unit 170 includes a reading unit 170a that reads the image on one side of the sheet and a reading unit 170b that reads the image on the other side of the sheet. Background members 171a and 171b are provided at positions facing each other across the sheet conveyance path in each of the reading unit 170a and the reading unit 170b. The background members 171a and 171b have, for example, a black surface 1711 and a white surface 1712 as shown in FIG. 3, and can switch the background to black or white when reading the sheet by rotating with a drive source (not shown). Further, the reading size by the output reading unit 170 is larger than the sheet size, and is configured to be able to read the edges of the four sides of the sheet.

[0031] ​ The image analysis unit 180 analyzes the read image data output by the output item reading unit 170, calculates adjustment values for the positions of the images to be printed on the front and back surfaces of the paper, and outputs them to the control unit 101.

[0032] 〔Operation of Image Position Adjustment〕 Next, the operation of image position adjustment in the image forming apparatus 100 will be described. Image position adjustment is for adjusting the position of the image printed on the paper in the image forming apparatus 100, and has a first adjustment mode and a second adjustment mode.

[0033] The first adjustment mode is a mode for adjusting the position of the image printed on the paper by the image forming unit 150 before this printing (before printing based on a job). Specifically, in the first adjustment mode, first, the measurement patterns (referred to as ticks) T1 to T4 shown in FIG. 4 are provided by the image forming unit 150 inside by a preset distance (for example, 10 mm from the paper edge) from the edges of the four sides of the paper for printing on the front and back surfaces of the paper for the image forming unit 150. Then, the printed matter is read by the output item 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 ticks T1 to T4. Then, for each of the front and back surfaces, the image analysis unit 180 calculates adjustment values for a plurality of adjustment items so that the distance between the paper edge and the ticks T1 to T4 (the ticks facing each paper edge) becomes a predetermined distance, and stores them in the storage unit 104. Note that in order to improve measurement accuracy and stability, the first adjustment mode may be repeated a plurality of times. Also, printed matters with a plurality of the ticks T1 to T4 provided may be printed, adjustment values may be calculated for each of them, and the average value thereof may be used. At the time of this printing, the control unit 101 controls the image processing unit 140, the image forming unit 150, the conveyance 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.

[0034] Examples of the plurality of adjustment items calculated in the first adjustment mode include magnification in the vertical and horizontal directions, image shift in the vertical and horizontal directions, rotation, skew, vertical trapezoid, horizontal trapezoid, curvature, and curvature position. Each of these adjustment items can independently obtain an adjustment value. Among the above adjustment items, by adjusting the magnification, image shift, rotation, skew, vertical trapezoid, and horizontal trapezoid adjustment items, the image positions at the four corners can be adjusted. Also, the curvature and curvature position are for adjusting the distortion of the image, and by using them in combination, more advanced image position adjustment is possible.

[0035] FIG. 5A shows the adjustment value ranges and adjustment images for each adjustment item of vertical magnification, horizontal magnification, vertical image shift, and horizontal image shift. FIG. 5B shows the adjustment value ranges and adjustment images for each adjustment item of rotation, skew, vertical trapezoid, horizontal trapezoid, curvature, and curvature position. Note that the thick arrow A in FIGS. 5A and 5B indicates the paper conveyance direction, the solid line represents the paper, the dotted line represents the target image position, the hatching represents the current image position, and the thin arrow indicates the direction in which the image moves due to adjustment. For the image shift in FIG. 5A, since it is difficult to show both the current image position and the target image position, they are represented as the same, and it is shown as a diagram indicating only the direction in which the image moves due to adjustment. Also, for FIG. 5B, the solid line indicating the paper is omitted.

[0036] In this embodiment, the first adjustment mode has been described as automatically obtaining the adjustment values of each adjustment item shown in FIGS. 5A and 5B by having the output reading unit 170 read the paper on which the dragonflies T1 to T4 are printed and analyzing the obtained read image data by the image analysis unit 180. However, it is also possible to receive, from the operation display unit 103, the input of the adjustment values of each adjustment item determined by the user visually observing the paper on which the dragonflies T1 to T4 are printed, and obtain the values of the respective adjustment values. Further, the document reading unit 110 may be configured to read and analyze the paper on which the dragonflies T1 to T4 are printed. In this case, since the document reading unit 110 is made for the purpose of the copying function, the background is white. For the purpose of clearly reading the paper edge, for example, a dark background paper is overlaid on the paper on which the dragonflies T1 to T4 are printed, and the front and back, top and bottom of the printed paper are swapped as appropriate (for example, 4 times) and read and analyzed as appropriate so that the paper edge can be read appropriately.

[0037] The second adjustment mode is a mode (so-called real-time adjustment mode) for adjusting the position of the image printed on the paper by the image forming unit 150 during this printing. Specifically, in the second adjustment mode, first, the dragonflies T11 to T14 shown in FIG. 6 are provided at the four inner corners at a preset distance (for example, 3 mm from each of the two paper edges constituting the four corners of the paper) from the four corners of the paper on which the job is printed, and printed on the paper by the image forming unit 150. Then, the printed matter is 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 dragonflies T11 to T14 (the dragonflies facing each paper edge). Then, based on the obtained distance between the paper edge and the dragonflies T11 to T14, the image analysis unit 180 calculates and updates the adjustment values of each adjustment item to be obtained. The control unit 101 controls the image processing unit 140, the image forming unit 150, the conveyance unit 106, etc. based on the updated adjustment values to adjust the position of the image printed on the paper in subsequent printing. ) and printed on the paper by the image forming unit 150. Then, the printed matter is 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 dragonflies T11 to T14 (the dragonflies facing each paper edge). Then, based on the obtained distance between the paper edge and the dragonflies T11 to T14, the image analysis unit 180 calculates and updates the adjustment values of each adjustment item to be obtained. The control unit 101 controls the image processing unit 140, the image forming unit 150, the conveyance unit 106, etc. based on the updated adjustment values to adjust the position of the image printed on the paper in subsequent printing. Note that the preset distance described above is smaller in the second adjustment mode because, in the second adjustment mode, the images of the user content printed together with the dragonflies T11 to T14 are used, so as to prevent the dragonflies T11 to T14 from overlapping with the user content. In addition, auxiliary information for, for example, a printing operator to check printing conditions and the like is often printed near the edge of the paper. If these overlap with the dragonflies T11 to T14, the second adjustment mode may not operate correctly. Therefore, a process of blanking out (rendering it non-toner printed) the image information around the dragonflies may be added.

[0038] In the present embodiment, in the second adjustment mode, for simplification of the process, warping is performed and adjustment of the warping position is omitted, and thus, independent dragonflies T11 to T14 are used at the four corners as shown in FIG. 6. Note that, similar to the first adjustment mode, warping may be performed using the dragonflies T1 to T4 and the warping position may also be adjusted.

[0039] Here, in the real-time adjustment performed during the present printing in a conventional image forming apparatus, similar to the first adjustment mode described above, the image position is adjusted so that the distance between the paper edge and the dragonflies T1 to T4 becomes a predetermined distance.

[0040] FIG. 7 is a diagram showing printed materials at the job start time (print start time) and the job end time (print end time) when, in a job in which conventional real-time adjustment was performed, the cutting of the paper bundle used for printing by the job was inaccurate and the paper size changed during the job, with the paper size being larger at the job end time than at the job start time. The dotted line on the printed material at the job end time shown in FIG. 7 indicates the paper size at the job start time (the same applies to FIGS. 8A to 10B). Note that, in the printed material output by the job, an image based on the job is printed inside the dragonflies T11 to T14, but is omitted in FIGS. 7 to 10B for simplification.

[0041] As described above, in the conventional real-time adjustment, in order to adjust the image magnification so that the distances between the paper edges and the corners of the staples are constant, when the paper size changes during the job, as shown in FIG. 7, the image size changes accordingly. Then, for example, when cutting the printed paper stack based on the position at the start of the job, in the printed matter at the end of the job, problems such as the image being cut off after cutting may occur.

[0042] Therefore, the second adjustment mode of the present embodiment has, in addition to the first mode that performs the same adjustment as the conventional real-time adjustment, a second mode that restricts magnification adjustment, and a third mode that restricts magnification adjustment and adjusts the front-back difference caused by restricting magnification adjustment. Further, each of the second mode and the third mode is configured such that either an edge reference mode that 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 becomes a predetermined distance or a center reference mode that adjusts the position of the image so that the position of the image printed on the paper is located at the center of the paper can be selected by the operation display unit 103.

[0043] FIG. 8A is a diagram showing printed matters at the start and end of a job when image position adjustment is performed in the edge reference mode of the second mode. In FIG. 8A, an example is shown in which edges E1 and E4 are specific paper edges. In the edge reference mode of the second mode, while restricting magnification adjustment and adjusting the image position so as to be a predetermined distance from specific paper edges (E1 and E4 in FIG. 8A), as shown in FIG. 8A, when the subsequent process is set up to cut the sides (E3, E2) facing the specific paper edges, the image positions in the printed matters at the start and end of the job can be easily aligned.

[0044] FIG. 8B is a diagram showing printed matters at the start and end of a job when image position adjustment is performed in the center reference mode of the second mode. In the center reference mode of the second mode, since magnification adjustment is restricted and the image position is adjusted so that the image position is at an equal position from each paper edge, as shown in FIG. 8B, the image can be positioned at the center of the paper. For example, when there is no subsequent cutting process and it is necessary to finish the image size as specified, image position adjustment in this adjustment mode may be preferable.

[0045] When image position adjustment is performed in the second mode, as shown in FIG. 9, after printing an image on the first side (here, the front side) of the paper to be printed first, the paper may expand or contract, and a deviation may occur in the magnification of the front and back images. In FIG. 9, the solid arrow represents the arrow on the front side, and the dotted arrow represents the arrow on the back side (the same applies to FIGS. 10A and 10B). The third mode is a mode capable of adjusting the front-back difference when a deviation occurs in the magnification of the front and back images by restricting magnification adjustment in this way.

[0046] As a method for adjusting the front-back difference in the third mode, based on the image on the surface to be printed first in the image forming unit 150, the magnification of the image on the surface to be printed later is adjusted to match, thereby adjusting the front-back difference of the images printed on the front and back of the paper (referred to as front-back magnification adjustment), and the position of the image on the surface to be printed later is adjusted to a position where the positional deviation of the image on the surface to be printed later with respect to the image on the surface to be printed first is minimized on average at the four corners (referred to as front-back position adjustment). Which adjustment method to adopt can be selected by the operation display unit 103.

[0047] FIG. 10A is a diagram showing printed materials at the start and end of a job when front-back position adjustment is performed in the edge reference mode of the third mode. FIG. 10B is a diagram showing printed materials at the start and end of a job when front-back magnification adjustment is performed in the edge reference mode of the third mode. As shown in FIGS. 10A and 10B, in the third mode, even if the paper expands or contracts during printing on the front and back surfaces, the front-back image position relationship can be kept good.

[0048] Note that in FIGS. 7 to 10B, the case where the paper size increases as printing progresses has been described. However, conversely, the paper size may decrease as printing progresses. In this case, when the registration marks T11 to T14 are printed near the paper edge, it is conceivable that as printing progresses, the distance between any of the registration marks and the paper edge approaches, and further, the registration marks may protrude from the paper edge. In this case, it may become impossible to perform correct image position adjustment. Therefore, in the present embodiment, when restricting magnification adjustment in the second adjustment mode (that is, in the second mode and the third mode), it is possible to adjust the positions of the registration marks T11 to T14 so that the distances between the registration marks T11 to T14 and the paper edge are larger than those in the case where magnification adjustment is not restricted. Whether to adjust the positions of the registration marks T11 to T14 can be selected by the operation display unit 103.

[0049] FIG. 11 is a flowchart showing the flow of setting processing for setting various setting items such as the adjustment mode in the above-described image position adjustment. The setting processing shown in FIG. 11 is executed in cooperation with the CPU of the control unit 101 and the program stored in the RAM.

[0050] First, the control unit 101 causes the operation display unit 103 to display a selection button for selecting whether to restrict the execution of magnification adjustment. When a selection button for selecting not to restrict the execution of magnification adjustment is selected by the operation of the user on 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 processing.

[0051] In step S1, when a selection button for selecting to restrict the execution of magnification adjustment is selected by the operation of the user on the operation display unit 103 (step S1; YES), the control unit 101 causes the operation display unit 103 to display a selection button for selecting whether to perform front-back difference adjustment. When a selection button for selecting not to perform front-back difference adjustment is selected by the operation of the user on the operation display unit 103 (step S3; NO), the control unit 101 sets the adjustment mode to the second mode (step S4) and proceeds to step S8.

[0052] When a selection button for selecting to perform front-back difference adjustment by operating the user operation display unit 103 is selected (step S3; YES), the control unit 101 causes the operation display unit 103 to display a selection button for selecting whether to perform front-back magnification adjustment. When a selection button for selecting not to perform front-back magnification adjustment by operating the user operation display unit 103 is selected (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 a selection button for selecting to perform front-back magnification adjustment by operating the user operation display unit 103 is selected (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.

[0053] In step S8, the control unit 101 causes the operation display unit 103 to display a selection button for selecting whether to adjust the position of the staple. When a selection button for selecting to adjust the position of the staple by operating the user operation display unit 103 is selected (step S8; YES), the control unit 101 sets the staple position in the second adjustment mode to be separated from the paper edge by a predetermined distance in a direction away from a preset reference position (step S9) and proceeds to step S11. When a selection button for selecting not to adjust the position of the staple by operating the user operation display unit 103 is selected (step S8; NO), the control unit 101 sets the staple position in the second adjustment mode to the preset reference position (step S10) and proceeds to step S11.

[0054] In step S11, the control unit 101 causes the operation display unit 103 to display a selection button for selecting whether to align the image position with a specific paper edge. When a selection button for selecting to align the image position with a specific paper edge by operating the user operation display unit 103 is selected (step S11; YES), the control unit 101 additionally sets the edge reference mode to the currently set adjustment mode (step S12) and ends the setting process. When a selection button for selecting not to align the image position with a specific paper edge is selected by an operation on the user operation display unit 103 (step S11; NO), the control unit 101 additionally sets the center reference mode to the currently set adjustment mode (step S13), and ends the setting process.

[0055] Note that for a specific paper edge, for example, the control unit 101 may automatically set it according to the settings at the time of printing, the paper path, and the post-process after printing. For example, after printing, there are face-up where the first page is discharged with the top face facing up and face-down where the bottom face is facing down, and when the face-up / face-down switching control is performed after passing the output reading unit 170, if the direction (side) of a specific paper edge is set for the convenience of the post-process, the direction of the specific paper edge in the image read by the output reading unit 170 will be different depending on the face-up / face-down setting. Also, when a post-process is provided with an online cutter, stapler, or bookbinding machine such as a saddle binder, it can be easily imagined that the paper edge to be set as a specific paper edge is different depending on the subsequent device. Therefore, it is preferable that the control unit 101 automatically sets a specific paper edge according to the configuration of the subsequent device.

[0056] Also, in the above setting process, the case where the user makes various settings related to image position adjustment on the operation panel has been described as an example. However, a setting function for image position adjustment may be provided on a screen limited to administrators so that only administrators can set it, or a service technician who performs maintenance on the image forming apparatus 100 may open a dedicated maintenance mode screen and be able to set it. Alternatively, it may be possible to set it with a mechanical or electrical mechanism such as a dip switch.

[0057] Hereinafter, the image position adjustment process executed by the control unit 101 based on the settings by the above setting process will be described. FIG. 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 and printing start is instructed with the image position adjustment set.

[0058] First, the control unit 101 performs image position adjustment for the front and back respectively in the first adjustment mode (step S21). Since the image position adjustment in the first adjustment mode is as described above, the description is incorporated by reference. Note that the control unit 101 switches the surfaces of the background members 171a and 171b facing the paper in the output reading unit 170 between the black surface 1711 and the white surface 1712 according to the color of the paper used (the black surface 1711 is made to face for white paper, the white surface 1712 is made to face for black paper, and for other paper colors, the color of the background member that is easy to read or readable is appropriately selected. In the case of black paper, the color tone of the barcodes printed on the paper may also be formed with a coloring material that can be easily distinguished from the paper, such as white toner), and the four sides of the paper edge are read by the output reading unit 170.

[0059] 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.

[0060] That is, the control unit 101 first assigns barcodes T11 to T14 for measuring the distance from the paper edge to the margin of the image of the page to be printed (step S23). Here, the control unit 101 assigns barcodes T11 to T14 based on the barcode position setting information stored in the storage unit 104.

[0061] Next, the control unit 101 controls the image processing unit 140, the image forming unit 150, the conveyance unit 106, etc. based on the adjustment values of the respective adjustment items stored in the storage unit 104 to adjust the position of the image printed on the paper, and prints the image with the pins T11 to T14 on the paper and fixes it by the fixing unit 160 (step S24). When performing double-sided printing, the control unit 101 controls the conveyance unit 106 and the image forming unit 150 to perform double-sided printing.

[0062] Next, the control unit 101 causes the output document reading unit 170 to read the printed paper (printed matter) and acquires the read image data including the paper edge (step S25).

[0063] Next, the control unit 101 causes the image analysis unit 180 to analyze the read image data acquired by the output document reading unit 170 to acquire the distances between the paper edge and the pins T11 to T14 (step S26).

[0064] Next, the control unit 101, in the set adjustment mode by the image analysis unit 180, calculates and updates the adjustment values of the respective adjustment items to be acquired based on the distances between the paper edge and the pins T11 to T14 (step S27), and proceeds to step S28.

[0065] For example, when the adjustment mode is set to the first mode, the adjustment values of the adjustment items of magnification, image shift, rotation, skew, vertical trapezoid, and horizontal trapezoid are calculated so that the distances between the paper edge and the pins T11 to T14 (the pins facing each paper edge) become a predetermined distance, and these adjustment values in the storage unit 104 are updated.

[0066] For example, when the adjustment mode is set to the edge reference mode of the second mode, the adjustment values of the adjustment items of image shift, rotation, skew, vertical trapezoid, and horizontal trapezoid are calculated so that the distance between a specific paper edge and the pin facing the specific edge becomes a predetermined distance, and these adjustment values in the storage unit 104 are updated. Magnification adjustment is not performed. For example, when the adjustment mode is set to the center reference mode of the second mode, the adjustment values of the adjustment items such as image shift, rotation, skew, vertical trapezoid, and horizontal trapezoid are calculated so that the pins T11 to T14 come to an equal position from the paper edge (to the center of the paper), and these adjustment values in the storage unit 104 are updated. Magnification adjustment is not performed.

[0067] For example, when the adjustment mode is set to the third mode (front-back position adjustment), first, among the pins T11 to T14 on the first side printed first, the adjustment values of the adjustment items such as image shift, rotation, skew, vertical trapezoid, and horizontal trapezoid are calculated so that the position of the pin facing a specific paper edge is a predetermined distance from the specific paper edge, and these adjustment values in the storage unit 104 are updated. Magnification adjustment is not performed. Next, the adjustment values of the adjustment items such as image shift, rotation, skew, vertical trapezoid, and horizontal trapezoid are calculated so that the displacement between the pins T11 to T14 on the second side printed later and the adjusted pins T11 to T14 on the first side is minimized on average at the four corners, and these adjustment values in the storage unit 104 are updated. Magnification adjustment is not performed.

[0068] In this embodiment, in the adjustment mode where magnification adjustment is not restricted, the adjustment values of the adjustment items such as magnification, image shift, rotation, skew, vertical trapezoid, and horizontal trapezoid are calculated, and in the adjustment mode where magnification adjustment is restricted, the adjustment values of the adjustment items such as image shift, rotation, skew, vertical trapezoid, and horizontal trapezoid are calculated. However, adjustment items with less deviation etc. may be omitted. Also, the user may be configured to be able to set from the operation display unit 103 which adjustment item adjustment values are to be calculated.

[0069] Also, in the second adjustment mode, the printed paper is read to measure the distances between the pins T11 to T14 and the paper edge, the adjustment values are calculated based on the measured results, and the calculated adjustment values are applied to the image to be printed next. Therefore, a delay of about several to several tens of sheets of paper occurs from the printing used for the measurement to the printing to which the adjustment values are applied. Therefore, the control unit 101 may control to adjust the degree of update of the adjustment values so as not to over-adjust.

[0070] Also, when calculating each adjustment value, the image analysis unit 180 preferably stores the adjustment values of the most recent multiple times (for example, 20 times) of adjustments, and calculates the adjustment value in consideration of the trend using the adjustment value calculated based on the current read image data and the adjustment values of the most recent multiple times. Thereby, the adjustment accuracy can be improved.

[0071] 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 repeatedly executes 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.

[0072] Hereinafter, a modification example of the above image position adjustment process will be described. [Modification Example 1] The flowchart shown in FIG. 12 illustrates the case where adjustment in the first adjustment mode is performed before the execution of a job. However, the adjustment in the first adjustment mode may be performed at least before the execution of a job immediately after replacing the paper bundle, and it is not necessary to perform the first adjustment mode before each job execution. However, when the user reconfigures the mode setting in the second adjustment mode between jobs, and if only the adjustment in the adjustment mode set until then has been performed to update the adjustment value, since the adjustment value in the newly set adjustment mode is not held, it becomes necessary to reset the adjustment value and perform the adjustment in the first adjustment mode again before the start of the next job. To avoid this and enable smooth switching of the adjustment mode in the second adjustment mode without performing adjustment in the first adjustment mode, in the second adjustment mode, the image analysis unit 180 preferably calculates the adjustment values by at least two adjustment modes in parallel and stores them in the storage unit 104. For example, the calculation of the adjustment value in the adjustment mode set by the user and the calculation of the adjustment value in the first mode without restricting the magnification adjustment 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 in the set adjustment modes can be calculated and stored in parallel with the adjustment values of the actual adjustment mode. In this case, since the printed result when the adjustment value is updated is actually obtained only in the currently set adjustment mode, the adjustment value of the adjustment mode for calculating the adjustment value in parallel can be calculated as the difference value from the adjustment value of the currently set adjustment mode and updated.

[0073] 〔Modification Example 2〕 When a cutting process is included in the subsequent process, it is preferable that the adjustment of the cutting position can be easily performed. When the image position is adjusted so that the image is arranged at a predetermined distance from a specific paper edge by the above image position adjustment process, by cutting the side facing the specific paper edge first, even if there is a variation in the paper size of the paper bundle of the printing paper, the paper cutting and cutting process can be easily performed. Here, when performing the cutting process, since the user needs to correctly grasp the direction of the specific paper edge, in the above image position adjustment process, for example, to make it easy to identify the direction (side) to be cut first, change the design of the cutting dash line of the direction (side) to be cut first, add a specific mark, or print and stack a sheet that prints post-process information indicating the cutting direction and cutting method in a visible form on the top surface of the print job bundle separately from the actual printed matter based on the job. Also, a control may be combined in which the post-process information is transmitted from the image forming apparatus 100 to a display device installed in front of the cutting machine, or the post-process information is transmitted from the image forming apparatus 100 to a display device installed in front of the cutting machine via a server.

[0074] [Modification 3] In the above embodiment, a specific paper edge is defined, and the image position is adjusted by adjusting the distance between the edge and the register mark, but the same processing result 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 the specific register mark. Alternatively, a paper edge or register mark that is not used for adjusting the distance between the paper edge and the register mark may be specified.

[0075] [Modification 4] The image position adjustment of the above embodiment may be used in combination with other correction processes such as conventional offset correction, which detects the paper passing position before printing and calculates and adjusts the offset correction amount of the paper position and the printed image based on the detected information. For example, a sensor is provided to read the paper passing position of the paper edge before printing, and a mechanism is generally used to correct the offset of the paper just before printing based on the result. For example, if the sensor detects only one side (for example, the front side) of the paper edge, it is expected that the image position is more stably controlled with respect to the front side of the paper edge. In such a case, the edge side read by the sensor may be set as the specific paper edge, or a message recommending that the edge side be set may be displayed on the operation screen. Similarly, if there is a separate mechanism for restricting the paper position, the paper edge that is likely to stabilize the relationship between the image position and the paper edge due to the regulation can be set or recommended as the specific paper edge.

[0076] [Modification 5] In the image forming apparatus 100 of the above embodiment, the second adjustment mode is described as having a plurality of adjustment modes, and the user is described as selecting which adjustment mode to use for adjustment. However, any one of the adjustment modes may be incorporated in the image forming apparatus.

[0077] [Modification 6] In the above-described embodiment, the read image data of the printed paper by the output object reading unit 170 is analyzed by the image analysis unit 180 to calculate an adjustment value, and based on the calculated adjustment value, the control unit 101 controls each unit including the image forming unit 150 to adjust the image position. However, the calculation of the adjustment value by analyzing the read image data of the printed paper may also be performed by the control unit 101. Alternatively, the adjustment value calculated by the image analysis unit 180 may be transmitted by the communication unit 102 to an external device (controller or server), and in the external device, a paper image including an image and a margin whose position on the paper is adjusted according to the received adjustment value is generated and transmitted to the image forming apparatus 100. Then, in the image forming apparatus 100, the received image may be printed as it is without position adjustment to output a printed matter with the image position adjusted. Or, the measurement result of the distance between the paper edge and the pin may be transmitted by the communication unit 102 to an external device, and the external device may also calculate the adjustment value.

[0078] As described above, according to the image forming apparatus 100, the control unit 101 has, as an operation mode for image position adjustment, a first adjustment mode for adjusting the position of the image printed on the paper by the image forming unit 150 before this printing, and a second adjustment mode for adjusting the position of the image printed on the paper by the image forming unit 150 during this printing. During the operation in the second adjustment mode, at least the implementation of magnification adjustment among the adjustment items implemented in the first adjustment mode is restricted. Therefore, even when the cutting accuracy of the paper bundle used for printing is not sufficient, it is possible to reduce the image magnification deviation through the job, and it is possible to obtain a good printing result with little positional deviation of the images between the cut papers in the post process.

[0079] Further, 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 since the user can select the first mode or the second mode, it is also possible to fit the image to the outer shape of the paper without implementing magnification restriction.

[0080] In addition, since the second adjustment mode has a third mode that restricts the implementation of magnification adjustment and further adjusts the front-back difference of the images printed on the front and back of the paper, even when the paper expansion rate changes due to changes in the internal temperature or paper state during the job, it is possible to obtain a printed result with a small front-back difference.

[0081] Also, among the plurality of adjustment modes included in the second adjustment mode, each of the adjustment modes that restricts the implementation of magnification adjustment adjusts the position of the image so that the distance between the image printed on at least one side of the paper by the image forming unit 150 and a specific edge of the paper becomes a predetermined distance, and the position of the image printed on the paper by the image forming unit 150 is adjusted so that the position of the image is located at the center of the paper. Either of the adjustment modes is configured to be selectable. Therefore, if the adjustment mode for adjusting the position of the image so that the distance from a specific edge is a predetermined distance is selected, the relationship between the image position and the specific edge of the paper can be maintained throughout the job, facilitating the subsequent cutting process. Also, the image position can be positioned at the center of the paper. Here, the maintenance of the relationship between the image position and the specific edge of the paper described above may be configured to maintain a predetermined distance, or may be configured to maintain the relationship (distance) at the start of printing in the second adjustment mode. The selection of this configuration may be determined in advance or may be according to the content set by means such as an operation panel. Also, in the above description, as an example of image position adjustment, magnification and image position were specifically described as control targets, but the present invention is not limited to these. For example, the rotational image position adjustment shown in FIG. 5B is usually adjusted so as not to have an inclination with respect to the outer shape approximating the paper to a rectangle, but when a paper edge is specified, it may be configured to be adjusted so as not to have an inclination with respect to the paper edge.

[0082] In addition, when performing adjustment in the second adjustment mode, the control unit 101 calculates the adjustment values of at least two adjustment modes included in the second adjustment mode and stores them in the storage unit 104, facilitating switching to another adjustment mode.

[0083] Further, when the control unit 101 restricts the magnification adjustment in the second adjustment mode, the control unit 101 adjusts the position of the measurement pattern so that the distance between the measurement pattern printed on the sheet by the image forming unit 150 and the edge of the sheet becomes larger than that when the magnification adjustment is not restricted. Therefore, it is possible to prevent the measurement pattern from protruding from the sheet edge when the cutting accuracy of the sheet bundle is poor and the sheet becomes smaller as the job progresses.

[0084] Note that the description in the above embodiment is a preferred example of the image forming apparatus according to the present invention and is not limited thereto.

[0085] Also, in the above description, an example in which a non-volatile semiconductor memory or a hard disk is used as a computer-readable medium storing a program for executing each process is disclosed, but the present invention is not limited to this example. As other computer-readable media, portable recording media such as CD-ROMs can also be applied. Further, a carrier wave may be applied as a medium for providing program data via a communication line.

[0086] In addition, the detailed configuration and detailed operations of each unit constituting the image forming apparatus can be appropriately changed without departing from the spirit of the present invention.

Description of Reference Numerals

[0087] 100 Image forming apparatus 101 Control unit 102 Communication unit 103 Operation display unit 104 Storage unit 105 Paper feeding unit 106 Conveying unit 110 Document reading unit 140 Image processing unit 150 Image forming unit 160 Fixing unit 170 Output reading unit 180 Image analysis unit

Claims

1. an image forming means for forming an image on a sheet; an image position adjusting means for adjusting the position of an image printed on a sheet by the image forming means based on the positional relationship between an edge of the sheet and a measurement pattern printed on the sheet by the image forming means; An image forming apparatus comprising: The image position adjusting means includes a first adjustment mode for adjusting the position of an image printed on a sheet by the image forming means based on the positional relationship between each of the opposing edges of the sheet and the measurement pattern, and a second adjustment mode for adjusting the position of an image printed on a sheet by the image forming means based on the positional relationship between one of the opposing sheet edges and the measurement pattern. An image forming apparatus having the above.

2. In the second adjustment mode, the image position adjusting means adjusts the position of an image printed on a sheet by the image forming means based on one of the opposing sheet edges in a direction parallel to the sheet conveyance direction and one of the opposing sheet edges in a direction perpendicular to the sheet conveyance direction. The image forming apparatus according to claim 1.

3. In the first adjustment mode, the measurement pattern is formed so as to be at a predetermined distance from each of the opposing edges of the sheet. The image forming apparatus according to claim 1 or 2.

4. In the second adjustment mode, the measurement pattern is formed so as to be at a predetermined distance from one of the opposing sheet edges. The image forming apparatus according to any one of claims 1 to 3.

5. In the first adjustment mode, the image position adjusting means further adjusts the magnification of an image printed on a sheet based on the positional relationship between each of the opposing edges of the sheet and the measurement pattern. The image forming apparatus according to any one of claims 1 to 4.

6. In the second adjustment mode, when printing images on both sides of a sheet, the image position adjusting means adjusts the front-back difference of the image on the other side printed later with reference to the image on one side printed first. The image forming apparatus according to any one of claims 1 to 5.

7. An image position adjusting method for adjusting the position of an image printed on a sheet by an image forming means based on the positional relationship between an edge of the sheet and a measurement pattern printed on the sheet by the image forming means, A first adjustment mode for adjusting the position of an image printed on a sheet by the image forming means based on the positional relationship between each of the edges of the opposing sheets and the measurement pattern among the edges of the sheet, and a second adjustment mode for adjusting the position of an image printed on a sheet by the image forming means based on the positional relationship between one of the opposing sheet edges and the measurement pattern. An image position adjustment method including these modes.

Images