Image forming system and program

Abstract

To acquire position information used for correction of an image forming position even when a reference point of a mark for positioning is deviated from an analysis area set to a read image.SOLUTION: An image sensor is provided at a subsequent stage of an image forming unit. In an intermediate state in which a reference point P0 of a mark M for positional deviation detection is not included in an analysis region W set for a read image and a part m of the mark M is included, a processor determines a temporary position instead of the actual position of the reference point P0 on the basis of the part m of the mark M. The temporary position is the position of a point of contact P1.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to an image forming system and a program. [Background technology]

[0002] An image forming system is a system that forms an image on paper. In an image forming system, the image formation position on paper changes due to various errors during the paper transport process, expansion and contraction of the paper, etc. Therefore, an image forming system has been proposed that has a function for correcting the image formation position during execution of a print job. More specifically, a first image formed on a first sheet (the previous sheet) is read, and the amount of misalignment of the first image relative to the first sheet is determined by analyzing the read image obtained. Based on the amount of misalignment, the position at which the second image is formed on a second sheet (the subsequent sheet) is corrected. This feedback correction based on the read image is repeatedly performed.

[0003] Image forming systems that correct the image formation position by test printing are also known. In such image forming systems, test printing is performed by printing a chart containing multiple marks on paper. After the test printing, the paper is discharged and scanned using a document scanning device to generate a scanned image. Based on the scanned image, specifically the positions of the multiple marks included in the scanned image, the position at which the image is formed on the paper is corrected.

[0004] Patent Document 1 discloses a chart used in test printing. The chart includes a plurality of marks, each of which has a cross shape. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-25446 Summary of the Invention [Problem to be solved by the invention]

[0006] When correcting the image formation position based on a scanned image in an image forming system, if the entire scanned image is analyzed when analyzing multiple marks contained in the scanned image, problems such as increased analysis time and analysis load arise. Therefore, a local analysis area is generally set for each mark in the scanned image. In this case, if the reference point of the mark (for example, the intersection of a cross-shaped mark) is included in the analysis area, the actual position of the reference point can be identified through analysis of the mark, and the amount of positional deviation can be calculated based on that actual position. In other words, that actual position can be used to correct the image formation position.

[0007] On the other hand, there may be cases where the reference point is not included in the analysis area due to factors such as a large misalignment of the image relative to the paper. In such cases, the actual position of the reference point cannot be directly identified. Generally, the smaller the mark size, the smaller the analysis area, making it more likely that the mark's reference point will fall outside the analysis area. Even if the mark's reference point falls outside the analysis area, it is desirable to obtain position information that can be used to correct the image formation position as much as possible.

[0008] The object of the present invention is to enable the acquisition of positional information used to correct the image formation position, even if the reference point of the positioning mark deviates from the analysis area set for the read image, as long as the analysis area and the mark are in a certain positional relationship. [Means for solving the problem]

[0009] The image forming system described in claim 1 includes an image reading unit that reads an image formed on paper, and a processor that controls image formation based on the read image obtained by reading the image reading unit, and is characterized in that, in an intermediate state in which the reference point of a mark for detecting misalignment is not included within an analysis area set for the read image but a portion of the mark is included, the processor determines a virtual position that replaces the actual position of the reference point based on the portion of the mark, and corrects the image formation position on the paper based on the virtual position.

[0010] The image forming system of claim 2 is the image forming system of claim 1, characterized in that the processor determines the virtual position on or outside the outer frame of the analysis area.

[0011] The image forming system of claim 3 is the image forming system of claim 2, wherein the temporary position is determined on the outer frame, and the processor, when the mark crosses a specific horizontal side of the outer frame, determines the vertical coordinate of the temporary position based on the vertical coordinate of the specific horizontal side and determines the horizontal coordinate of the temporary position based on the horizontal coordinate of a portion of the mark, and when the mark crosses a specific vertical side of the outer frame, determines the horizontal coordinate of the temporary position based on the horizontal coordinate of the specific vertical side and determines the vertical coordinate of the temporary position based on the vertical coordinate of a portion of the mark.

[0012] The image forming system of claim 4 is the image forming system of claim 3, characterized in that the processor identifies the specific horizontal side or the specific vertical side by identifying at least one of the contact point between the outer frame and a portion of the mark, the end of the portion of the mark within the outer frame, and the gap between the outer frame and a portion of the mark.

[0013] The image forming system of claim 5 is the image forming system of claim 4, characterized in that the processor generates a vertically integrated image and a horizontally integrated image by accumulating partial images within the analysis area in the vertical and horizontal directions, and identifies at least one of the contact portion, the edge portion, and the gap by analyzing the vertically integrated image and the horizontally integrated image.

[0014] The image forming system of claim 6 is characterized in that, in the image forming system of claim 3, the abscissa or ordinate of a portion of the mark is the abscissa or ordinate of a representative point that represents the portion of the mark.

[0015] The image forming system described in claim 7 is characterized in that, in the image forming system described in claim 6, a part of the mark is a line segment, and the representative point is the point of contact between a part of the mark and the outer frame.

[0016] The image forming system of claim 8 is the image forming system of claim 1, characterized in that the mark has a first vertical line extending vertically from the reference point and a first horizontal line extending horizontally from the reference point, the outer frame of the analysis area has a first vertical size in the vertical direction and a first horizontal size in the horizontal direction, the first vertical line has a second vertical size in the vertical direction that is smaller than the first vertical size, and the first horizontal line has a second horizontal size in the horizontal direction that is smaller than the first horizontal size.

[0017] The image forming system of claim 9 is the image forming system of claim 8, characterized in that the mark further has a second vertical line extending vertically from the reference point and connected to the first vertical line via the reference point, and a second horizontal line extending horizontally from the reference point and connected to the first horizontal line via the reference point, the second vertical line having the second vertical size in the vertical direction, and the second horizontal line having the second horizontal size in the horizontal direction.

[0018] The image forming system of claim 10 is the image forming system of claim 1, characterized in that the outer frame of the analysis area has a first vertical size in the vertical direction and a first horizontal size in the horizontal direction, the mark has a size twice the second vertical size in the vertical direction and a size twice the second horizontal size in the horizontal direction, the second vertical size is smaller than the first vertical size, and the second horizontal size is also smaller than the second horizontal size.

[0019] The image forming system of claim 11 is characterized in that, in the image forming system of claim 1, the processor estimates the position of the reference point based on a portion of the mark in the intermediate state and sets the estimated position as the tentative position.

[0020] The image forming system described in claim 12 is the image forming system described in claim 1, characterized in that the processor, in an appropriate state in which the reference point of the mark is included within the analysis area, determines the actual position of the reference point, corrects the image forming position based on the actual position, and determines an error in an inappropriate state in which the mark is not included within the analysis area.

[0021] The image forming system described in claim 13 is the image forming system described in claim 1, characterized in that the processor determines the actual position or the virtual position based on a first read image obtained by reading a first image formed on a first sheet of paper, and corrects in real time the position at which the second image is formed on the second sheet of paper based on the actual position or the virtual position.

[0022] The image forming system described in claim 14 is a program executed in an image forming system, the image forming system including an image reading unit that reads an image formed on paper, and a processor that controls image formation based on the read image obtained by reading by the image reading unit, and is characterized in that, by executing the program, the processor, in an intermediate state in which the reference point of a mark for detecting misalignment is not included within an analysis area set for the read image but a portion of the mark is included, determines a virtual position that replaces the actual position of the reference point based on the portion of the mark, and corrects the image formation position on the paper based on the virtual position. [Effects of the Invention]

[0023] According to the image forming system of claim 1, a temporary position used for correcting the image forming position can be acquired in the intermediate state.

[0024] According to the image forming system of claim 2, the virtual position can be made closer to the actual position of the reference point.

[0025] According to the image forming system of claim 3, the coordinates of the temporary position can be determined using the ordinate of the horizontal side or the abscissa of the vertical side.

[0026] According to the image forming system of claim 4, it is possible to correctly identify a specific horizontal side or a specific vertical side.

[0027] According to the image forming system of claim 5, it is possible to easily identify a specific horizontal side or a specific vertical side.

[0028] According to the image forming system of claim 6, the horizontal coordinate or the vertical coordinate of the temporary position can be clearly specified.

[0029] According to the image forming system of claim 7, when the part is a line segment, the abscissa or ordinate of the tentative position can be easily specified.

[0030] According to the image forming system of claim 8, it becomes easier to identify the moving direction of the mark in the intermediate state.

[0031] According to the image forming system of claim 9, when a mark having a cross shape is used, it becomes easier to identify the moving direction of the mark.

[0032] According to the image forming system of claim 10, when a mark having a rectangular shape, a cross shape, or the like is used, it becomes easier to identify the moving direction of the mark.

[0033] According to the image forming system of claim 11, the virtual position can be made closer to the actual position of the reference point.

[0034] According to the image forming system of claim 12, a process corresponding to the state is executed.

[0035] According to the image forming system of claim 13, the image forming position is corrected in real time.

[0036] According to the image forming system of claim 14, in the intermediate state, a temporary position used for correcting the image forming position can be acquired. [Brief explanation of the drawings]

[0037] [Figure 1] FIG. 1 is a schematic diagram illustrating an image forming system according to an embodiment. [Figure 2] FIG. 2 is a diagram illustrating a plurality of functions provided in a processor. [Figure 3] FIG. 10 is a diagram illustrating the synthesis of a main image and a sub-image. [Figure 4] 10A and 10B are diagrams illustrating an example of image misalignment relative to a sheet of paper. [Figure 5] FIG. 1 is a diagram showing a plurality of analysis regions. [Figure 6] FIG. 10 is a diagram illustrating an example of an appropriate state. [Figure 7] FIG. 10 is a diagram illustrating an example of an intermediate state. [Figure 8] FIG. 10 is a diagram illustrating an example of an inappropriate state. [Figure 9] FIG. 10 is a diagram illustrating a first example of a tentative position determination method. [Figure 10] FIG. 10 is a diagram illustrating a second example of a tentative position determination method. [Figure 11] FIG. 10 is a diagram illustrating a method for detecting an edge. [Figure 12] FIG. 10 is a diagram showing size conditions for a cross mark. [Figure 13] FIG. [Figure 14] FIG. 10 is a diagram showing size conditions for an L-shaped mark. [Figure 15] FIG. 10 is a diagram showing determination of a tentative position based on an L-shaped mark. [Figure 16] FIG. 10 is a diagram showing size conditions for a rectangular mark. [Figure 17] FIG. 10 is a diagram illustrating determination of a tentative position based on a rectangular mark. [Figure 18] 10 is a flowchart showing an example of operation. [Figure 19] FIG. 10 is a diagram illustrating a processor according to a modified example. [Figure 20] FIG. 10 is a diagram illustrating estimation of a tentative position according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0038] Hereinafter, an embodiment will be described with reference to the drawings.

[0039] (1) Overview of the embodiment An image forming system according to an embodiment includes an image reading unit and a processor. The image reading unit reads an image formed on paper. The processor controls image formation based on the read image obtained by reading by the image reading unit. More specifically, in an intermediate state in which a reference point of a mark for detecting misalignment is not included but a portion of the mark is included within an analysis area set for the read image, the processor determines a temporary position that replaces the actual position of the reference point based on the portion of the mark. The processor corrects the image formation position on the paper based on the temporary position.

[0040] According to the above configuration, even if the reference point is not included in the analysis area, that is, even if the actual position of the reference point cannot be identified, it is possible to determine a temporary position in place of the actual position based on a portion of the mark (which may also be called a portion of interest) included in the analysis area. The image formation position on the paper is corrected based on the temporary position. Based on this mechanism, a relatively small analysis area may be set. The reference point may also be called a feature point. The temporary position may also be called an orientation position or a provisional position.

[0041] The image reading unit is, for example, an image sensor. Generally, a mark is a graphic for identifying the amount of misalignment. An analysis area is a local area set on the read image. Since multiple marks are usually formed on the paper, multiple analysis areas corresponding to the multiple marks are set on the read image. For each analysis area, the partial image contained therein is analyzed. This determines the actual position of the reference point, determines a temporary position in place of the actual position, or determines the absence of a mark. The image formation position may be corrected in real time during execution of a print job, or may be corrected prior to execution of a print job.

[0042] Methods for determining a temporary position include a first method in which the temporary position is set on the outer frame of the analysis area, and a second method in which the temporary position is set outside the outer frame of the analysis area. The first method allows a reliable temporary position to be set. Therefore, excessive correction can be avoided. Furthermore, the first method can eliminate part of the positional deviation in the initial correction, increasing the likelihood that the reference point will be included within the analysis area in the subsequent correction. On the other hand, the second method allows the temporary position to be closer to the actual position. Note that a variant in which the temporary position is set inside the outer frame of the analysis area is also possible.

[0043] In an embodiment, a tentative position is defined on an outer frame. When a mark crosses a specific horizontal side of the outer frame, the processor determines the vertical coordinate of the tentative position based on the vertical coordinate of the specific horizontal side and the horizontal coordinate of the tentative position based on the horizontal coordinate of a portion of the mark. On the other hand, when a mark crosses a specific vertical side of the outer frame, the processor determines the horizontal coordinate of the tentative position based on the horizontal coordinate of the specific vertical side and the vertical coordinate of the tentative position based on the vertical coordinate of a portion of the mark.

[0044] According to the above configuration, when determining the coordinates of the temporary position, the coordinates of the side that the mark crosses can be used. The outer frame typically has a rectangular shape, and in this case, the outer frame is composed of two horizontal sides (top and bottom sides) and two vertical sides (left and right sides).

[0045] In an embodiment, the processor identifies a specific horizontal edge or a specific vertical edge by identifying at least one of a contact portion between the outer frame and a portion of the mark, an edge of the portion of the mark within the outer frame, and a gap between the outer frame and a portion of the mark. The size of the analysis region and the size of the mark are determined so that an edge and a gap occur in an intermediate state, in other words, so that two contact portions do not occur simultaneously. The contact portion is, for example, a contact point or a contact area. The edge portion is, for example, an end point or an end area.

[0046] In an embodiment, the processor generates a vertically integrated image and a horizontally integrated image by integrating partial images in the analysis region in the vertical and horizontal directions. The processor identifies at least one of the contact portion, the edge, and the gap by analyzing the vertically integrated image and the horizontally integrated image. By analyzing the vertically integrated image and the horizontally integrated image, a portion of the mark, i.e., a portion of interest, can be easily and accurately analyzed.

[0047] In an embodiment, the abscissa or ordinate of a portion of a mark is the abscissa or ordinate of a representative point that represents the portion of the mark. The representative point is, for example, a contact point, an end point, a midpoint, or a centroid point. In an embodiment, the portion of the mark is a line segment. The representative point is a contact point between the portion of the mark and the outer frame. Generally, within the analysis region, the portion of the mark has a width. Any position within the contact area created by the intersection of the portion and the outer frame is defined as the contact point.

[0048] In an embodiment, the mark has a first vertical line extending vertically from a reference point and a first horizontal line extending horizontally from the reference point. The outer frame of the analysis area has a first vertical size in the vertical direction and a first horizontal size in the horizontal direction. The first vertical line has a second vertical size in the vertical direction that is smaller than the first vertical size. The first horizontal line has a second horizontal size in the horizontal direction that is smaller than the first horizontal size.

[0049] In the above configuration, the mark has, for example, a cross shape or an L shape. If the sizes of the analysis area and the mark are determined so that the above size conditions are satisfied, partial edges and gaps appear in the intermediate state, making it easy to identify the movement direction of the mark relative to the analysis area. In other words, in the intermediate state, a state in which a portion of the mark simultaneously crosses two vertical sides or two horizontal sides does not occur.

[0050] In an embodiment, the mark further includes a second vertical line extending vertically from the reference point and connecting to the first vertical line via the reference point, and a second horizontal line extending horizontally from the reference point and connecting to the first horizontal line via the reference point. The second vertical line has a second vertical size in the vertical direction. The second horizontal line has a second horizontal size in the horizontal direction.

[0051] In the above configuration, the mark has, for example, a cross shape. With the above configuration, the movement direction of the mark can be identified regardless of whether the mark moves in the positive or negative vertical direction or whether the mark moves in the positive or negative horizontal direction.

[0052] In an embodiment, the outer frame of the analysis region has a first vertical size in the vertical direction and a first horizontal size in the horizontal direction. The mark has a size twice as large as a second vertical size in the vertical direction and a size twice as large as the second horizontal size in the horizontal direction. The second vertical size is smaller than the first vertical size, and the second horizontal size is also smaller than the second horizontal size.

[0053] In the above configuration, the mark has, for example, a rectangle or a cross shape. When a rectangular mark (including a filled rectangle) is used, the center of gravity of the mark may be determined as the reference point.

[0054] In an embodiment, the processor estimates the position of the reference point based on a portion of the mark in the intermediate state and defines the estimated position as a tentative position. For example, the actual position of the reference point may be estimated from a portion within the analysis region using an extrapolation method. The tentative position may be defined outside the outer frame on an extension of the portion.

[0055] In an embodiment, the processor determines an actual position of the reference point in a proper state where the reference point of the mark is included in the analysis region, and corrects the image formation position based on the actual position. The processor determines an error in an improper state where the mark is not included in the analysis region.

[0056] In this embodiment, the processor determines an actual position or a tentative position based on a first scanned image obtained by scanning a first image formed on a first sheet. The processor corrects in real time the position where the second image is formed on the second sheet based on the actual position or the tentative position. This configuration corrects the image formation position in real time during execution of a print job, based on feedback control.

[0057] The program executed by the processor may be installed in the image forming system via a network or a portable storage medium. The image forming system may be physically composed of one device or multiple devices. These devices may be connected to each other via a network. The image forming system is an information processing device. The image forming system includes a non-transitory storage medium that stores the program.

[0058] (2) Details of the embodiment 1 shows an example of the configuration of an image forming system according to an embodiment. The illustrated image forming system 10 sequentially forms multiple images on multiple sheets of paper and has a function for correcting the image formation position in real time using feedback control while a print job is being executed. Correction of the image formation position is also called registration correction or registration adjustment.

[0059] 1, an image forming system 10 includes a paper feeder 12, an image forming device 14, an inspection device 16, and a post-processing device 18. Correction of the image formation position involves at least the image forming device 14 and the inspection device 16. The inspection device 16 may be incorporated into the image forming device 14.

[0060] The paper feed device 12 has two paper feed trays 20 and 22. Each of the paper feed trays 20 and 22 is a large paper feed tray that can accommodate, for example, several thousand sheets of paper. A plurality of sheets of paper are sequentially fed from the paper feed device 12 to the image forming device 14. Each sheet of paper is a medium on which an image is formed.

[0061] The image forming device 14 has an image forming unit 24. In this embodiment, the image forming unit 24 is an image forming engine that forms each image on each sheet of paper using an electrophotographic method. More specifically, the image forming unit 24 has a rotating intermediate transfer belt and multiple photosensitive units. The multiple photosensitive units are aligned in the direction of movement of the intermediate transfer belt. Multiple color toner images are sequentially transferred onto the intermediate transfer belt by the multiple photosensitive units. The resulting multiple toner image is then transferred from the intermediate transfer belt to the sheet of paper. Images may also be formed on the sheet using a method other than electrophotography (e.g., inkjet method).

[0062] The image forming device 14 is equipped with paper feed trays 26, 28. As needed, multiple sheets of paper are sequentially supplied from the paper feed trays 26, 28 to the image forming unit 24. The capacity of each paper feed tray 26, 28 is smaller than the capacity of each paper feed tray 20, 22. Reference numeral 30 denotes a paper transport path. The paper transport path 30 is provided across the paper feed device 12, the image forming device 14, the inspection device 16, and the post-processing device 18. In FIG. 1, the left side of the paper transport path 30 is the upstream side, and the right side is the downstream side.

[0063] The image forming device 14 has a control unit 32. The control unit 32 controls the operation of each element in the image forming system 10. Image data is sequentially transferred from the control unit 32 to the image forming unit 24. The control unit 32 controls the operation of the image forming unit 24. In other words, the control unit 32 controls the formation of each image on each sheet of paper. The control of the control unit 32 includes real-time misalignment correction control. The control unit 32 corrects the positional misalignment of the image on the sheet of paper.

[0064] The control unit 32 has a processor that executes a program. The processor is, for example, a CPU. An operation panel 34 and a display 36 are connected to the control unit 32. The operation panel 34 is, for example, a screen panel with a touch sensor. Other input devices may be connected to the control unit 32. The display 36 is, for example, a liquid crystal display. All or part of the control unit 32 may be provided outside the image forming apparatus 14.

[0065] The control unit 32 is generally connected to an information processing device via a network and executes print jobs sent from the information processing device. A print job includes multiple images and their print instructions. Hereinafter, each input image may be referred to as a "main image."

[0066] The control unit 32 generates a composite image by combining a sub-image with each main image. The composite image is formed on each sheet of paper. The sub-image has multiple marks for identifying the amount of misalignment after the fact. Such marks are also called registration marks. The image forming device 14 is equipped with a return paper transport path used when forming an image on the back side of a sheet of paper, but this is not shown in the figure.

[0067] The inspection device 16 reads images to inspect the images formed on each sheet of paper. Specifically, the inspection device 16 has an image sensor 38. The image sensor 38 corresponds to an image reading unit. The image sensor 38 is an in-line sensor provided on the paper transport path 30. The image sensor 38 has, for example, a plurality of detection elements arranged in a direction (hereinafter sometimes referred to as a second direction) perpendicular to the paper transport direction (hereinafter sometimes referred to as a first direction). A reader that reads an image by laser scanning in the second direction may also be used as the image sensor 38. Other image reading devices may also be used as the image sensor 38.

[0068] The image sensor 38 is provided on the paper transport path 30 downstream of the image forming unit 24. In the illustrated configuration example, the read image (more precisely, read image data) obtained by reading by the image sensor 38 is sent to the control unit 32.

[0069] In addition to the image sensor 38, the inspection device 16 also has an image sensor 39. The image formed on the front side of the paper is read by the image sensor 38. The image formed on the back side of the paper is read by the image sensor 39. The correction of the image formation position applied to the front side of the paper and the correction of the image formation position applied to the back side of the paper are basically the same, and the following will explain the correction of the image formation position applied to the front side of the image.

[0070] The post-processing device 18 has multiple post-processing functions such as cutting, folding, and punching. In the post-processing device 18, the peripheral area of ​​each sheet of paper is usually cut off. The peripheral area is a margin area in which multiple marks, etc. are formed. The sub-image is, for example, an image for forming multiple marks, etc. in the peripheral area of ​​the sheet of paper. A device having a discharge tray or discharge stacker is usually provided downstream of the post-processing device 18.

[0071] The operation of the image forming system 10 will be summarized below. Multiple sheets of paper with images formed on them are sequentially discharged downstream from the image forming unit 24. The image formed on each sheet includes multiple marks for identifying the amount of misalignment. The image sensor 38 sequentially reads the multiple images formed on the multiple sheets of paper. The multiple read images thus generated are sequentially sent from the image sensor 38 to the control unit 32. The control unit 32 analyzes each read image and calculates the amount of misalignment. For each read image, multiple analysis areas corresponding to the multiple marks are defined. The control unit 32 analyzes the partial images included in each analysis area. The control unit 32 calculates the amount of misalignment based on multiple analysis results corresponding to the multiple analysis areas. Based on the amount of misalignment, the control unit 32 corrects the image formation position relative to the paper to eliminate the amount of misalignment.

[0072] If the paper to be read is referred to as the first paper and the image formed on the first paper is referred to as the first image, the amount of misalignment is determined by analyzing the first read image obtained by reading the first image, and the formation position of the second image on the second paper is corrected based on the amount of misalignment. Here, the first paper is the earlier paper, and the second paper is the later paper. Between the first and second paper, there are usually multiple printed papers waiting to be read.

[0073] The positional deviation may be a positional deviation due to a vertical image shift, a positional deviation due to a horizontal image shift, a positional deviation due to image rotation, a positional deviation due to a scale deviation, etc. The control unit 32 actually has a function to collectively correct these positional deviations.

[0074] In order to correct the misalignment, it is necessary to identify the misalignment or the amount of misalignment of each mark itself. In the embodiment, to identify the misalignment of the marks, a partial image within the analysis region is analyzed as follows.

[0075] Fig. 2 shows an example of the configuration of the control unit 32. The control unit 32 has a processor 40. A memory (not shown) is connected to the processor. In Fig. 2, multiple functions performed by the processor 40 are represented by multiple blocks. The processor 40 functions as an image analyzer 44, a correction amount calculator 46, a controller 48, a generator 50, and a combiner 52. Note that in Fig. 2, configurations that are not directly related to correction of the image formation position are omitted from the illustration.

[0076] The image analyzer 44 has a real position calculator 55, a tentative position calculator 56, and an error determiner 57, which function selectively depending on the state. In a proper state where the reference point of the mark (e.g., the intersection of a cross mark) is included in the analysis area, the real position calculator 55 calculates the position of the reference point as the real position. In an intermediate state where the reference point of the mark is not included in the analysis area but a portion of the mark is included, the tentative position calculator 56 calculates a tentative position instead of the real position based on the portion. In the intermediate state, the portion of the mark can be called a target portion. In an embodiment, the tentative position is determined on the outer frame of the analysis area. This will be described in detail later. The error determiner 57 determines an error in an improper state where the mark is not included in the analysis area. In other words, an error is determined when neither the real position nor the tentative position can be calculated.

[0077] The correction amount calculator 46 calculates the amount of misalignment of the image relative to the paper for each scanned image 54 based on multiple analysis results corresponding to multiple analysis regions. Specifically, the correction amount calculator 46 calculates the amount of misalignment of the image by individually comparing multiple actual positions or multiple virtual positions calculated by analyzing multiple marks with multiple predetermined positions. The correction amount calculator 46 calculates the current correction amount based on the amount of misalignment.

[0078] The controller 48 controls the operation of the image forming unit, and specifically, corrects the image forming position based on the correction amount so as to eliminate or reduce misalignment of the image with respect to the paper. The correction of the image forming position may include correction by electronic control as well as correction by mechanical control.

[0079] The generator 50 generates a sub-image 64 including a plurality of marks. The generator 50 may be configured with a memory. The combiner 52 combines the sub-image 64 with each input image, i.e., each main image 62, to generate a composite image 66. In the illustrated configuration example, the composite image 66 is sent to the image forming unit via the controller 48.

[0080] FIG. 3 shows the composition of a main image 200 and a sub-image 202. The main image 200 is an input image. The main image 200 has a content area 200A that includes text, graphics, photographs, etc. The sub-image 202 has a first area 202A that corresponds to the content area 200A, and a second area 202B that corresponds to the peripheral area. The second area 202B includes multiple marks 204. A composite image is formed on paper. Note that the formation of the image may also be referred to as printing the image.

[0081] An example of misalignment is shown schematically in Figure 4. An image 70 is formed on a sheet of paper 68. Reference numeral 68A indicates the correct image formation area. The peripheral area of ​​the image 70 includes multiple marks 72. In Figure 4, the left-right direction is the paper transport direction, i.e., the first direction. The direction perpendicular to the vertical direction is the second direction.

[0082] An image 70 is misaligned with respect to a sheet of paper 68. Specifically, reference numeral 74 indicates the amount of misalignment in a first direction, and reference numeral 76 indicates the amount of misalignment in a second direction. While the sheet of paper 68 is being transported, the image sensor 38 reads the image 70, thereby generating a read image 54. The read image 54 is sent to the control unit. The control unit analyzes the position of each mark in the read image 54, thereby calculating a vertical misalignment amount 74 and a horizontal misalignment amount 76.

[0083] FIG. 5 shows a scanned image 80. The scanned image 80 has a plurality of marks 82-1 to 82-4. More precisely, each of the marks 82-1 to 82-4 is a mark image. Here, the marks 82-1 to 82-4 each have a cross shape. When analyzing the scanned image, a plurality of analysis regions 84-1 to 84-4 are set in the scanned image 80. Each of the analysis regions 84-1 to 84-4 is a local region or a small region, and a partial image within each of the analysis regions 84-1 to 84-4 is the subject of analysis. If the entire scanned image 80 were to be analyzed, the amount of processing would increase, but by setting a plurality of analysis regions 84-1 to 84-4, the amount of processing can be reduced.

[0084] As described above, the image forming system according to the embodiment includes a temporary position calculator that functions in the intermediate state, where a temporary position is calculated instead of the actual position, and the temporary position is used to correct the image forming position.

[0085] Figure 6 shows the correct state. The x direction is horizontal and the y direction is vertical. The analysis domain W is a rectangular (square in the illustrated example) domain. The analysis domain W has an outer frame F. The outer frame F consists of a horizontal side (top side) H1, a horizontal side (bottom side) H2, a vertical side (left side) V1, and a vertical side (right side) V2. The analysis domain W has a center Q. The coordinates of the upper left corner of the outer frame F are (0,0), the coordinates of the upper right corner of the outer frame F are (xa,0), the coordinates of the lower left corner of the outer frame F are (0,ya), and the coordinates of the lower right corner of the outer frame F are (xa,ya).

[0086] Mark M has a reference point P0 as an intersection point. The positional deviation of reference point P0 is expressed by vector R. Mark M has a horizontal line A1 extending from reference point P0 in the -x direction, a horizontal line A2 extending in the +x direction, a vertical line B1 extending in the -y direction, and a vertical line B2 extending in the +y direction. Horizontal line A1 and horizontal line A2 are connected via reference point P0. Similarly, vertical line B1 and vertical line B2 are connected via reference point P0.

[0087] As shown in Figure 6, in the correct state, the reference point P0 is included within the analysis region W, so the position (i.e., the actual position) of the reference point P0 can be easily identified based on a partial image within the analysis region W. In this case, an x-direction projection image and a y-direction projection image may be generated based on the partial image, and the actual position of the reference point P0 may be calculated by analyzing them. When calculating the actual position, a pattern matching method, a line extraction method, or the like may be used.

[0088] An intermediate state is shown in Figure 7. The reference point P0 of the mark M is located outside the analysis region W, i.e., outside the outer frame F. In the intermediate state, the reference point P0 is not included in the partial image to be analyzed, and it is difficult to directly identify the actual position of the reference point P0.

[0089] In the mark M, a portion m of the vertical line B2 exists within the analysis region W. Therefore, in this embodiment, based on the portion m, the position of the tangent point P1 is calculated as a tentative position instead of the actual position of the reference point P0. The portion m is a line segment having an end point P2, and the portion m is tangent to the outer frame F at the tangent point P1.

[0090] In the illustrated example, the contact point P1 is located on the horizontal side H1, and the coordinates of the tentative position are (x1, 0). Specifically, the x-coordinate (x1) of the tentative position is determined by analyzing the portion m. The y-coordinate of the tentative position is determined by the y-coordinate of the horizontal side H1. In other words, the coordinates of the horizontal side or vertical side to which the portion m is in contact are used to determine the coordinates of the tentative position.

[0091] When the mark M shifts relative to the analysis region W, an end point P2 appears, and at the same time, a gap 86 appears between the end point P2 and the outer frame F. When identifying the horizontal or vertical side to which the portion m is in contact, the end point P2 or the gap 86 can be used instead of the contact point. Multiple feature quantities that appear in the intermediate state may be referenced simultaneously.

[0092] Figure 8 shows an improper state. Mark M is completely outside the analysis area W. That is, the reference point P0 of mark M is outside the analysis area W, and none of the lines of mark M are within the analysis area W. In such an improper state, neither the actual position nor the tentative position can be calculated, and therefore an error is determined.

[0093] 9 shows a first example of a tentative position determination method. By projecting a partial image G1 in the analysis region in the x direction, an x-direction projection image (which can also be called a horizontal projection image) 88 is generated. Similarly, by projecting the partial image G1 in the y direction, a y-direction projection image (which can also be called a vertical projection image) 90 is generated. In practice, a black-and-white inversion process is applied to the partial image G1, and the respective projection images 88 and 90 are generated from the partial image G1 after black-and-white inversion. In the black-and-white inversion process, the lowest pixel value is converted to the highest pixel value, and the highest pixel value is converted to the lowest pixel value.

[0094] The x-direction projection image 88 has a y-axis and an axis indicating an integrated value. Here, the integrated value is a value calculated by an integration process after black-and-white inversion processing. In the illustrated example, the y-coordinate (y1) of the endpoint is identified by edge detection, threshold processing, etc. on the x-direction projection image 88. The portion m1 is present in the section s1 above the coordinate y1. The portion m1 is not included in the section s2 below the coordinate y1. Therefore, the side to which the portion m1 is in contact can be identified based on the x-direction projection image 88. The side to which the portion m1 is in contact may also be identified based on the gap adjacent to the endpoint P2.

[0095] The y-direction projection image has an x-axis and an axis showing the integrated value. In the example shown, a large integrated value occurs over the range from x2 to x3. For example, if the absolute value of the difference Δx between x2 and x3 is smaller than threshold A, x4, the midpoint between x2 and x3, is determined to be the x-coordinate of the tentative position. Threshold A is a numerical value used to evaluate the degree of inclination.

[0096] Even when the part m1 of the mark is parallel to the x direction instead of the y direction, the tentative position can be identified by the same method as above.

[0097] 10 shows a second example of the tentative position determination method. Partial image G2 includes a portion m2 that is slightly tilted with respect to the y direction. By projecting partial image G2 in the analysis region in the x direction, an x-direction projection image 94 is generated. Similarly, by projecting partial image G2 in the y direction, a y-direction projection image 96 is generated. In practice, first, black-and-white inversion processing is applied to partial image G2, and each projection image 94, 96 is generated from the black-and-white inverted partial image G1.

[0098] Similarly to the above, the y coordinate (y1) of the end point P2 can be identified by edge detection, threshold processing, etc. on the x-direction projection image 94. Using the y coordinate of the end point P2 as a boundary, a section s1 having the portion m2 and a section s2 not having the portion m2 are determined.

[0099] The y-direction projection image 96 spreads slightly in the x-direction. The x-coordinates of its two ends are x5 and x6. The absolute value of the difference Δx between them is equal to or greater than threshold A. Although it is possible to determine the intermediate position x7 between x5 and x6 as the x-coordinate (xs) of the tentative position, in the illustrated example, the following process is applied.

[0100] A Y-direction projection image 98 is generated by projecting only a strip-shaped region 92 (for example, a region with y coordinates from 0 to yy) near the horizontal side H1 in partial image G2 in the Y direction. The intermediate position x10 between the x coordinates x8 and x9 of both ends is determined as the x coordinate of the tangent point P1, that is, the x coordinate (xs) of the temporary position. The intermediate position x10 is simply the x coordinate of the tangent point. Even when a portion m2 of the mark extends while tilting along the x direction, the coordinate of the temporary position can be calculated using the same method as above.

[0101] FIG. 11 shows another example of an endpoint detection method. Partial image G3 includes a portion m3 of a mark. Here, the background color of partial image G3 is white, and the mark color is black. A two-dimensional matrix 100 is composed of multiple cells 102 arranged in the x and y directions. The two-dimensional matrix 100 is used to downsample partial image G3. A minimum value pooling process is applied to each cell in partial image G3, which extracts the minimum value from the region (pixel value group) corresponding to the cell and stores it in the cell.

[0102] Through the above process, in the illustrated example, a portion m3 of the mark is aggregated within a specific cell string 104. In the illustrated example, the cell string 104 is made up of a plurality of cells 106 that include the portion m3 and a plurality of cells 108 that do not include the portion m3. When a differentiation process is performed on the cell string 104 from one end to the other, a differentiated waveform 110 is obtained. Here, when the differentiated waveform 110 appears on the negative side, it indicates a transition from a gap (white) to a mark (black). In other words, it indicates the presence of the upper end of the portion m3. Note that when the differentiated waveform 110 appears on the positive side, it indicates a transition from a mark to a gap.

[0103] In the illustrated example, symbol s1 indicates a section that includes the portion m3, and symbol s2 indicates a section that does not include the portion m3. Even when the portion m3 is along the x direction, the endpoints can be identified using the same method as above.

[0104] When the end points are identified, the specific edges that contact the portion can be identified from the end points. The edges that contact the portion may also be identified from the direction in which the portion extends from the end points or the position of the gap. Of course, the specific edges may also be identified by identifying the contact points in the portion.

[0105] Next, a plurality of size conditions for a plurality of marks will be described with reference to FIGS.

[0106] FIG. 12 shows a cross-shaped mark M. Mark M has a reference point P0, and horizontal lines A1, A2, and vertical lines B1 and B2 extending from the reference point. Analysis area W has an outer frame F, which has horizontal sides H1, H2, and vertical sides V1 and V2. The horizontal size of analysis area W is X1, and the vertical size of analysis area W is Y1. The two horizontal lines A1 and A2 have the same size, specifically, X2. The two vertical lines B1 and B2 have the same size, specifically, Y2.

[0107] In an embodiment, in the intermediate state, the size conditions of X2 < X1 and Y2 < Y1 are satisfied such that an edge of a part of the mark appears, or conversely, such that a part does not cross two sides simultaneously. If the size conditions are not satisfied, a situation as shown in FIG. 13 occurs. In FIG. 13, the reference point P0 in the mark M is outside the analysis region W, and moreover, a part (vertical line B1) of the mark M is included in the analysis region W. Thus, an intermediate state has occurred. However, the vertical line B1 passes through both of the two horizontal sides, and the shift direction of the mark M cannot be specified from only the partial image within the analysis region W. The size conditions are defined such that an edge of a part of the mark appears before or at the time when the reference point P0 moves outside the analysis region W. As will be described below, the size conditions are also effective for other marks.

[0108] FIG. 14 shows an L-shaped mark M1. The mark M1 has a reference point P0 and also has a horizontal line A3 and a vertical line B3 extending from the reference point P0. The size of the analysis region W1 in the x direction is X3, and its size in the y direction is Y3. In the mark M1, the size of the horizontal line A3 is X4, and the size of the vertical line B3 is Y4. Here, the size conditions of X4 < X3 and Y4 < Y3 are satisfied. When the size conditions are satisfied, as shown in FIG. 15, when the mark M1 shifts in the x direction and the reference point P0 moves outside the analysis region W1, the end point P2 of the horizontal line A3 surely appears within the analysis region W1. In the illustrated example, the vertical side V5 intersects the horizontal line A3, and a contact point P1 is defined on the vertical side V5. The position of the contact point P1 is defined as a temporary position that replaces the actual position.

[0109] Figure 16 shows a rectangular mark M2. The mark M1 is filled, for example, with black. Here, the center of gravity of the mark M2 is the reference point P0 of the mark M2. The horizontal size of the analysis region W is X5, and the vertical size of the analysis region W is Y5. The mark M2 has a size of X6×2 in the x direction and a size of Y6×2 in the y direction. Here, the size conditions of X6 < X5 and Y6 < Y5 are satisfied. As shown in Figure 17, in the intermediate state, a part m4 of the mark M2 belongs to the analysis region W2. The center of gravity Pb of the part m4 is calculated. The coordinates of the center of gravity Pb are (xb, yb). The x coordinate of the vertical line V6 that the part m4 touches is xa. From the above, the coordinates (xa, yb) of the contact point P1 are specified as the coordinates of the temporary position.

[0110] Figure 18 shows the processing flow in the image analyzer shown in Figure 1 as a flowchart. In S10, the partial image within the analysis region is analyzed, and the state of the partial image is determined. Specifically, a proper state, an intermediate state, or an improper state is determined. If the proper state is determined, in S12, the actual position of the reference point is specified. That is, the x coordinate and y coordinate of the reference point are calculated by analyzing the partial image. If the improper state is determined in S10, an error is determined in S14.

[0111] If the intermediate state is determined in S10, in S16, the line type of a specific side (hereinafter referred to as the contact side) that touches a part of the mark (i.e., the part of interest) is identified. If the contact side is a vertical line, in S18, it is determined whether the contact side is the upper side or the lower side. If it is determined in S18 that the contact side is the upper side, in S20, the position of the contact point of the part of interest with respect to the upper side is set as the temporary position. Specifically, the x coordinate of the part of interest is specified by analyzing the partial image. As the y coordinate of the part of interest, 0, which is the y coordinate of the upper side, is specified.

[0112] If it is determined in S18 that the contacting edge is the bottom edge, the position of the contact point of the target portion with respect to the bottom edge is set as a tentative position in S22. Specifically, the x coordinate of the target portion is determined by analyzing the partial image. The y coordinate of the target portion, ya, which is the y coordinate of the bottom edge, is determined.

[0113] If the contacting edge is a vertical line, it is determined in S24 whether the contacting edge is the left edge or the right edge. If it is determined in S24 that the contacting edge is the left edge, the position of the point of contact of the portion of interest with respect to the left edge is set as a tentative position in S26. Specifically, 0, which is the x-coordinate of the left edge, is identified as the x-coordinate of the portion of interest. The y-coordinate of the portion of interest is identified by analyzing the partial image. If it is determined in S24 that the contacting edge is the right edge, the position of the point of contact of the portion of interest with respect to the right edge is set as a tentative position in S28. Specifically, xa, which is the x-coordinate of the right edge, is identified as the x-coordinate of the portion of interest. The y-coordinate of the portion of interest is identified by analyzing the partial image.

[0114] In S30, it is determined whether or not to analyze the next mark. If the next mark is to be analyzed, the steps from S10 onwards are executed again.

[0115] A modified example is shown in Fig. 19. In Fig. 19, the same components as those shown in Fig. 2 are denoted by the same reference numerals, and the description thereof will be omitted.

[0116] The control unit 32A has a processor 40A. The processor 40A functions as an image analyzer 44A. The image analyzer 44A has a real position calculator 55, a position estimator 120, and an error determiner 57. As already explained, the real position calculator 55 calculates the real position of the reference point in a proper state. As already explained, the error determiner 57 determines an error in an improper state.

[0117] The position estimator 120 estimates the position of the reference point in the intermediate state and determines the estimated position as a tentative position. The position may be estimated using the extrapolation method described below or other methods.

[0118] FIG. 20 illustrates a method for estimating the actual position. The analysis region W includes only a portion m1 of the mark M, resulting in an intermediate state. Using the method described above, the coordinates of the end point P2 and the tangent point P4 can be determined. The length X1 of the horizontal line is known, and the distance X1a between the end point P2 and the tangent point P4 can be easily calculated. The extrapolated length X1b is calculated by subtracting the distance X1a from X1. For example, the coordinates (xa, yc) of the tangent point P4 and the length X1b can be used to determine the coordinates (xd, yc) of the reference point. The estimated coordinates are used as the tentative position P3. xd is calculated by adding X1b to xa. Even if the portion m1 is tilted, the position of the reference point can be estimated using the extrapolation method, and this position can be used as the tentative position.

[0119] A temporary position may be set on an extension line of the portion. For example, the x coordinate may be set by xd = xa + k × X1b, where k is a weight and is a value less than 1. Note that a modified example in which the temporary position is set inside the outer frame F may also be considered. Such a modified example may be adopted when it is desired to suppress the amount of positional deviation. In that case, the temporary position may be set on the portion m1.

[0120] By setting a temporary position on the outer frame, the temporary position can be brought closer to the actual position and the reliability of the temporary position can be increased. For example, if a partial image contains noise, estimation errors are likely to occur when estimating the actual position of the reference point. In contrast, according to the above embodiment, a temporary position can be set on a portion of interest that can actually be observed in the direction in which the mark has shifted. This increases the likelihood that the actual position will be included in the analysis region during the next position correction.

[0121] In the above embodiment, the partial image within the analysis area is analyzed during the execution of the print job. However, for example, the partial image within the analysis area may be analyzed during test printing, and the correction amount for the image formation position may be calculated based on the analysis results. In the above embodiment, instead of a rectangular analysis area, an analysis area having another shape may be used. In this case, the size conditions are determined according to the shape of the analysis area and the shape of the mark.

[0122] In each of the above embodiments, the term "processor" refers to a processor in a broad sense, and includes general-purpose processors (e.g., CPU: Central Processing Unit, etc.) and dedicated processors (e.g., GPU: Graphics Processing Unit, ASIC: Application Specific Integrated Circuit, FPGA: Field Programmable Gate Array, programmable logic device, etc.).

[0123] Furthermore, the operations of the processor in each of the above embodiments may be performed not only by a single processor but also by multiple processors located at physically separate locations working together. Furthermore, the order of the operations of the processor is not limited to the order described in each of the above embodiments and may be changed as appropriate.

[0124] (Addendum) (((1))) an image reading unit that reads an image formed on a sheet; a processor that controls image formation based on the read image obtained by reading the image reading unit; Including, The processor: In an intermediate state in which a reference point of a mark for detecting positional deviation is not included in an analysis area set for the read image but a part of the mark is included, a temporary position is determined in place of the actual position of the reference point based on the part of the mark; correcting the image forming position on the paper based on the temporary position; An image forming system comprising: (((2))) In the image forming system described in (((1))), the processor determines the tentative position on or outside the outer boundary of the analysis region. An image forming system comprising: (((3))) In the image forming system described in (((2))), the temporary position is defined on the outer frame; The processor: When the mark crosses a specific horizontal side of the outer frame, determining a vertical coordinate of the temporary position based on a vertical coordinate of the specific horizontal side, and determining a horizontal coordinate of the temporary position based on a horizontal coordinate of a portion of the mark; When the mark crosses a specific vertical side of the outer frame, a horizontal coordinate of the temporary position is determined based on a horizontal coordinate of the specific vertical side, and a vertical coordinate of the temporary position is determined based on a vertical coordinate of a portion of the mark. An image forming system comprising: (((4))) In the image forming system described in (((3))), the processor identifies the particular horizontal side or the particular vertical side by identifying at least one of a contact portion between the outer frame and a portion of the mark, an edge of the portion of the mark within the outer frame, and a gap between the outer frame and a portion of the mark; An image forming system comprising: (((5))) In the image forming system described in (((4))), The processor: generating a vertically integrated image and a horizontally integrated image by integrating the partial images in the analysis region in the vertical and horizontal directions; identifying at least one of the contact portion, the edge portion, and the gap by analyzing the vertical direction integrated image and the horizontal direction integrated image; An image forming system comprising: (((6))) In the image forming system described in (((3))), The abscissa or ordinate of a portion of the mark is the abscissa or ordinate of a representative point that represents the portion of the mark. An image forming system comprising: (((7))) In the image forming system described in (((6))), the portion is a line segment, The representative point is a point of contact between a part of the mark and the outer frame. An image forming system comprising: (((8))) In the image forming system according to any one of (((1))) to (((7))), the mark has a first vertical line extending vertically from the reference point and a first horizontal line extending horizontally from the reference point, the outer frame of the analysis region has a first vertical size in the vertical direction and a first horizontal size in the horizontal direction; the first vertical line has a second vertical size in the vertical direction that is smaller than the first vertical size; The first horizontal line has a second horizontal size in the horizontal direction that is smaller than the first horizontal size. An image forming system comprising: (((9))) In the image forming system described in (((8))), the mark further includes a second vertical line extending vertically from the reference point and connected to the first vertical line via the reference point, and a second horizontal line extending horizontally from the reference point and connected to the first horizontal line via the reference point, the second vertical line has the second vertical size in the vertical direction, The second horizontal line has the second horizontal size in the horizontal direction. An image forming system comprising: (((10))) In the image forming system according to any one of (((1))) to (((9))), the outer frame of the analysis region has a first vertical size in the vertical direction and a first horizontal size in the horizontal direction; the mark has a size twice the second vertical size in the vertical direction and a size twice the second horizontal size in the horizontal direction; the second vertical size is smaller than the first vertical size, the second lateral size is smaller than the second lateral size; An image forming system comprising: (((11))) In the image forming system according to any one of (((1))) to (((10))), the processor estimates a position of the reference point based on a portion of the mark in the intermediate state and defines the estimated position as the tentative position; An image forming system comprising: (((12))) In the image forming system according to any one of (((1))) to (((11))), The processor: In an appropriate state in which the reference point of the mark is included within the analysis region, an actual position of the reference point is determined, and the image formation position is corrected based on the actual position; determining an error in an improper state in which the mark is not included in the analysis region; An image forming system comprising: (((13))) In the image forming system according to any one of (((1))) to (((12))), The processor: determining the actual position or the tentative position based on a first read image obtained by reading a first image formed on a first sheet; correcting in real time the position at which the second image is to be formed on the second sheet based on the actual position or the virtual position; An image forming system comprising: (((14))) A program executed in an image forming system, The image forming system includes: an image reading unit that reads an image formed on a sheet; a processor that controls image formation based on the read image obtained by reading the image reading unit; Including, Execution of the program causes the processor to: In an intermediate state in which a reference point of a mark for detecting positional deviation is not included in an analysis area set for the read image but a part of the mark is included, a temporary position is determined in place of the actual position of the reference point based on the part of the mark; correcting the image forming position on the paper based on the temporary position; A program characterized by:

[0125] According to the image forming system described in (((1))), a temporary position used for correcting the image forming position can be acquired in the intermediate state. According to the image forming system described in (((2))), the virtual position can be made closer to the actual position of the reference point. According to the image forming system described in (((3))), the coordinates of the temporary position can be determined using the ordinate of the horizontal side or the abscissa of the vertical side. According to the image forming system described in (((4))), it is possible to correctly identify a specific horizontal side or a specific vertical side. According to the image forming system described in (((5))), it is possible to easily identify a specific horizontal side or a specific vertical side. According to the image forming system described in (((6))), the horizontal coordinate or the vertical coordinate of the tentative position can be clearly specified. According to the image forming system described in (((7))), when a part is a line segment, the horizontal coordinate or vertical coordinate of the tentative position can be easily specified. According to the image forming system described in (((8))), it becomes easier to identify the movement direction of the mark in the intermediate state. According to the image forming system described in (((9))), when a mark having a cross shape is used, it becomes easier to identify the moving direction of the mark. According to the image forming system described in (((10))), when a mark having a rectangular shape, a cross shape, or the like is used, it becomes easier to identify the moving direction of the mark. According to the image forming system described in (((11))), the virtual position can be made very close to the actual position of the reference point. According to the image forming system described in (((12))), a process corresponding to the state is executed. According to the image forming system described in (((13))), the image forming position is corrected in real time. According to the image forming system described in (((14))), a temporary position used for correcting the image forming position can be acquired in the intermediate state. [Explanation of symbols]

[0126] 10 Image forming system, 14 Image forming device, 16 Inspection device, 24 Image forming unit, 30 Paper transport path, 32 Control unit, 38 Image sensor, 40 Processor, 44 Image analyzer, 46 Correction amount calculator, 48 Controller, 55 Actual position calculator, 56 Virtual position calculator, 57 Error determiner.

Claims

1. an image reading unit that reads an image formed on a sheet; a processor that controls image formation based on the read image obtained by reading the image reading unit; Including, The processor: In an intermediate state in which a reference point of a mark for detecting positional deviation is not included in an analysis area set for the read image but a part of the mark is included, a temporary position is determined in place of the actual position of the reference point based on the part of the mark; correcting the image forming position on the paper based on the temporary position; An image forming system comprising:

2. 2. The image forming system according to claim 1, the processor determines the tentative position on or outside the outer boundary of the analysis region. An image forming system comprising:

3. 3. The image forming system according to claim 2, the temporary position is defined on the outer frame; The processor: When the mark crosses a specific horizontal side of the outer frame, determining a vertical coordinate of the temporary position based on a vertical coordinate of the specific horizontal side, and determining a horizontal coordinate of the temporary position based on a horizontal coordinate of a portion of the mark; When the mark crosses a specific vertical side of the outer frame, a horizontal coordinate of the temporary position is determined based on a horizontal coordinate of the specific vertical side, and a vertical coordinate of the temporary position is determined based on a vertical coordinate of a portion of the mark. An image forming system comprising:

4. 4. The image forming system according to claim 3, the processor identifies the particular horizontal side or the particular vertical side by identifying at least one of a contact portion between the outer frame and a portion of the mark, an edge of the portion of the mark within the outer frame, and a gap between the outer frame and a portion of the mark; An image forming system comprising:

5. 5. The image forming system according to claim 4, The processor: generating a vertically integrated image and a horizontally integrated image by integrating the partial images in the analysis region in the vertical and horizontal directions; identifying at least one of the contact portion, the edge portion, and the gap by analyzing the vertical direction integrated image and the horizontal direction integrated image; An image forming system comprising:

6. 4. The image forming system according to claim 3, The abscissa or ordinate of a portion of the mark is the abscissa or ordinate of a representative point that represents the portion of the mark. An image forming system comprising:

7. 7. The image forming system according to claim 6, a portion of the mark is a line segment, The representative point is a point of contact between a part of the mark and the outer frame. An image forming system comprising:

8. 2. The image forming system according to claim 1, the mark has a first vertical line extending vertically from the reference point and a first horizontal line extending horizontally from the reference point, the outer frame of the analysis region has a first vertical size in the vertical direction and a first horizontal size in the horizontal direction; the first vertical line has a second vertical size in the vertical direction that is smaller than the first vertical size; The first horizontal line has a second horizontal size in the horizontal direction that is smaller than the first horizontal size. An image forming system comprising:

9. 9. The image forming system according to claim 8, The mark further includes a second vertical line extending vertically from the reference point and connected to the first vertical line via the reference point, and a second horizontal line extending horizontally from the reference point and connected to the first horizontal line via the reference point, the second vertical line has the second vertical size in the vertical direction; the second horizontal line has the second horizontal size in the horizontal direction; An image forming system comprising:

10. 2. The image forming system according to claim 1, the outer frame of the analysis region has a first vertical size in the vertical direction and a first horizontal size in the horizontal direction; the mark has a size twice the second vertical size in the vertical direction and a size twice the second horizontal size in the horizontal direction; the second vertical size is smaller than the first vertical size, the second lateral size is smaller than the second lateral size; An image forming system comprising:

11. 2. The image forming system according to claim 1, the processor estimates a position of the reference point based on a portion of the mark in the intermediate state and defines the estimated position as the tentative position; An image forming system comprising:

12. 2. The image forming system according to claim 1, The processor: In an appropriate state in which the reference point of the mark is included within the analysis region, an actual position of the reference point is determined, and the image formation position is corrected based on the actual position; determining an error in an improper state in which the mark is not included in the analysis region; An image forming system comprising:

13. 2. The image forming system according to claim 1, The processor: determining the actual position or the tentative position based on a first read image obtained by reading a first image formed on a first sheet; correcting in real time the position where the second image is to be formed on the second sheet based on the actual position or the virtual position; An image forming system comprising:

14. A program executed in an image forming system, The image forming system includes: an image reading unit that reads an image formed on a sheet; a processor that controls image formation based on the read image obtained by reading the image reading unit; Including, Execution of the program causes the processor to: In an intermediate state in which a reference point of a mark for detecting positional deviation is not included in an analysis area set for the read image but a part of the mark is included, a temporary position is determined in place of the actual position of the reference point based on the part of the mark; correcting the image forming position on the paper based on the temporary position; A program characterized by:

Images