Image forming system and program

Abstract

To enhance accuracy or responsiveness in feedback correction of an image forming position based on a read image.SOLUTION: An image sensor is provided downstream of the image forming unit. A read image is generated by the image sensor through reading of the image. A deviation amount calculator 56 calculates a deviation amount on the basis of the read image. A correction amount calculator 46 calculates, as an actual deviation amount, a deviation amount that would be generated if the image formation position were not corrected, on the basis of a correction amount and a deviation amount that are corresponding to each other. The actual deviation amount is stored in a memory 42. A controller 48 controls image formation on the basis of the actual deviation amount.SELECTED DRAWING: Figure 2

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 of paper (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 of paper (the subsequent sheet) is corrected. This feedback correction based on the read image is repeatedly performed.

[0003] Patent Document 1 describes an image forming apparatus in which a plurality of misalignment amounts detected in a previous printing process (e.g., a test printing process) are stored, and in a subsequent printing process (e.g., a regular printing process), the positions at which each image is formed on each sheet of paper are corrected based on the stored misalignment amounts. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-14061 Summary of the Invention [Problem to be solved by the invention]

[0005] In an image forming system equipped with a function for correcting the image forming position based on a scanned image, the scanned image is obtained from an image on paper that has undergone correction of the image forming position. The amount of misalignment determined from the scanned image is not the actual amount of misalignment that reflects various misalignment factors, but is relative information that indicates whether the amount of correction applied is excessive or insufficient. Therefore, if the amount of correction is calculated based solely on the amount of misalignment determined from the scanned image, a problem may arise in that the image forming position cannot be corrected correctly.

[0006] Since the deviation amount is relative information, it is conceivable to determine the current correction amount based on the deviation amount and the previous correction amount. In this case, the previous correction amount may affect the response of the feedback correction, which may cause a problem.

[0007] An object of the present invention is to make it possible to perform correction that is superior in terms of accuracy and responsiveness to correction of the image forming position based on the relative amount of misalignment and the previous correction amount. [Means for solving the problem]

[0008] The image forming system of claim 1 includes an image forming unit that forms an image on paper, an image reading unit that reads the image formed on the paper, and a processor that controls the image forming unit based on the read image obtained by reading by the image reading unit, wherein the processor determines a first shift amount that represents the magnitude of shift of the first image relative to the first paper based on a first read image corresponding to a first image formed on a first paper by the image forming unit and obtained by reading by the image reading unit, determines a first correction amount applied when forming the first image, calculates a second correction amount for shift correction based on the first shift amount and the first correction amount, and corrects the position at which the second image is formed on a second paper according to the second correction amount.

[0009] The image forming system of claim 2 is the image forming system of claim 1, characterized in that the processor calculates a first actual shift amount that would have occurred if the image forming position had not been corrected based on the first correction amount, based on the first shift amount and the first correction amount, and calculates the second correction amount based on the first actual shift amount.

[0010] The image forming system of claim 3 is the image forming system of claim 1, characterized in that the processor calculates a first actual shift amount by subtracting the first correction amount from the first shift amount, and calculates the second correction amount based on the first actual shift amount.

[0011] The image forming system according to claim 4 is the image forming system according to claim 2 or 3, characterized in that the processor calculates a first smoothed actual deviation amount based on a plurality of actual deviation amounts on a time axis including the first actual deviation amount, and calculates the second correction amount based on the first smoothed actual deviation amount.

[0012] The image forming system of claim 5 is the image forming system of claim 1, characterized in that the processor stores the first correction amount in memory when forming the first image, and determines the first correction amount by reading the first correction amount from the memory when calculating the second correction amount.

[0013] The image forming system of claim 6 is the image forming system of claim 5, characterized in that the processor stores multiple correction amounts applied sequentially to multiple images in the memory in sequence, and when reading each correction amount from the memory, changes the reading position of the memory depending on the number of waiting sheets of paper corresponding to the time difference from the image formation timing to the image reading timing.

[0014] The image forming system of claim 7 is the image forming system of claim 1, characterized in that the processor sequentially corrects multiple positions for forming multiple images based on multiple read images during execution of a print job including print commands for multiple images.

[0015] The image forming system of claim 8 is a program executed in an image forming system, the image forming system including an image forming unit that forms an image on paper, an image reading unit that reads the image formed on the paper, and a processor that controls the image forming unit based on the read image obtained by reading by the image reading unit, and is characterized in that, by executing the program, the processor determines a first shift amount that represents the magnitude of shift of the first image relative to the first paper based on a first read image corresponding to a first image formed on a first paper by the image forming unit and obtained by reading by the image reading unit, determines a first correction amount applied when forming the first image, calculates a second correction amount for shift correction based on the first shift amount and the first correction amount, and corrects the position at which the second image is formed on a second paper according to the second correction amount. [Effects of the Invention]

[0016] According to the image forming system of claim 1, correction can be performed that is superior in accuracy and responsiveness to correction of the image forming position based on the relative amount of misalignment and the previous correction amount.

[0017] According to the image forming system of claim 2, the image forming position can be corrected based on the original or true amount of misalignment.

[0018] According to the image forming system of claim 3, the first actual deviation amount can be easily calculated.

[0019] According to the image forming system of claim 4, the image forming position is stably corrected.

[0020] According to the image forming system of claim 5, the first correction amount can be easily specified.

[0021] According to the image forming system of claim 6, each correction amount can be accurately specified.

[0022] According to the image forming system of claim 7, the image forming position is corrected in real time.

[0023] According to the image forming system of claim 8, correction can be performed that is superior in accuracy and responsiveness to correction of the image forming position based on the relative amount of misalignment and the previous correction amount. [Brief explanation of the drawings]

[0024] [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] 10A and 10B are diagrams illustrating an example of image misalignment relative to a sheet of paper. [Figure 4] FIG. 10 is a diagram illustrating a correction amount calculation method according to a comparative example. [Figure 5] FIG. 10 is a diagram showing a correction result according to a comparative example. [Figure 6] 5A and 5B are diagrams illustrating a correction amount calculation method according to the embodiment. [Figure 7] FIG. 10 is a diagram showing a correction result according to the embodiment. [Figure 8] FIG. 2 is a diagram illustrating a first information processing method according to the embodiment. [Figure 9] FIG. 10 is a diagram illustrating a second information processing method according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0025] Hereinafter, an embodiment will be described with reference to the drawings.

[0026] (1) Overview of the embodiment An image forming system according to an embodiment includes an image forming unit, an image reading unit, and a processor. The image forming unit forms an image on a sheet of paper. The image reading unit reads the image formed on the sheet of paper, thereby obtaining a read image. The processor controls the image forming unit based on the read image obtained by reading the image reading unit. Specifically, the processor determines a first shift amount representing the magnitude of shift of the first image relative to the first sheet of paper based on a first read image corresponding to a first image formed on the first sheet of paper by the image forming unit and obtained by reading the image reading unit. Meanwhile, the processor determines a first correction amount applied when the first image was formed. The processor then calculates a second correction amount for shift correction based on the first shift amount and the first correction amount, and corrects the position at which the second image is formed on the second sheet of paper according to the second correction amount.

[0027] The first deviation amount is a relative deviation amount that occurs under the application of the first correction amount. Therefore, in the above configuration, when calculating the second correction amount, the first deviation amount and the first correction amount that caused the first deviation are taken into consideration. By taking both the first deviation amount and the first correction amount into consideration, correction that is excellent in terms of accuracy and responsiveness can be performed.

[0028] There are various types of image misalignment relative to the paper, such as misalignment in the paper transport direction, misalignment in a direction perpendicular to the paper transport direction, misalignment in the rotational direction, and misalignment in scale. When correcting any type of misalignment, good correction can be achieved as described above by taking the first misalignment amount and the first correction amount into consideration. The formula for calculating the second correction amount may be switched depending on the nature of the misalignment.

[0029] The first correction amount may be stored in a memory, and the first correction amount may be determined by reading it from the memory. In this case, an internal memory of the image forming system or an external memory of an external device may be used. The first correction amount may be stored in a medium other than the memory, and the first correction amount may be determined by reading it from the medium.

[0030] In the embodiment, the processor calculates a first actual shift amount, based on the first shift amount and the first correction amount, that would have occurred if the image formation position had not been corrected based on the first correction amount. The processor also calculates a second correction amount based on the first actual shift amount. The actual shift amount corresponds to the original or true shift amount. However, it is not required that the first actual shift amount exactly matches the true shift amount. By using the actual shift amount as a basis, it is not necessary to use the previous correction amount as a basis when calculating the current correction amount (i.e., the second correction amount). The calculation of the first actual shift amount and the calculation of the second correction amount may be integrated. For example, the second correction amount may be calculated by executing a formula that includes the calculation of the first actual shift amount. By separating the calculation of the first actual shift amount from the calculation of the second correction amount and saving the first actual shift amount, the first actual shift amount can be reused.

[0031] In the embodiment, the processor calculates the first actual deviation amount by subtracting the first correction amount from the first deviation amount, and calculates the second correction amount based on the first actual deviation amount. With this configuration, the first actual deviation amount can be easily determined. Subtraction is a typical method that is suitable for various deviations. Depending on the type of deviation, other calculations (e.g., division) may be performed using the first deviation amount and the first correction amount. As described above, the calculation of the first actual deviation amount and the calculation of the second correction amount may be performed together or separately.

[0032] In an embodiment, the processor calculates a first smoothed actual deviation amount based on a plurality of actual deviation amounts on a time axis including the first actual deviation amount. Then, the processor calculates a second correction amount based on the first smoothed actual deviation amount. The deviation amount varies over time. By using the first smoothed actual deviation amount, the effect of the deviation amount fluctuation over time becomes less likely. The first smoothed actual deviation amount may be further multiplied by a coefficient for gain adjustment or response adjustment. The smoothed actual deviation amount may be calculated as an average value of the plurality of actual deviation amounts, or may be calculated by applying another smoothing calculation to the plurality of actual deviation amounts.

[0033] In an embodiment, the processor stores a first correction amount in memory when forming a first image. Then, the processor identifies the first correction amount by reading the first correction amount from memory when calculating the second correction amount. This configuration facilitates obtaining and identifying the first correction amount. Specifically, the processor sequentially stores multiple correction amounts applied to multiple images in memory. Meanwhile, when reading each correction amount from memory, the processor changes the memory read position depending on the number of waiting sheets, which corresponds to the time difference between the image formation timing and the image reading timing. Generally, the number of waiting sheets changes depending on the paper size, paper transport speed, etc. With the above configuration, even if such changes occur, it is possible to correctly associate the amount of misalignment with the amount of correction.

[0034] In an embodiment, the processor sequentially corrects multiple positions at which multiple images are formed based on multiple scanned images during execution of a print job that includes a print command for multiple images. This configuration performs real-time correction of image formation positions through feedback control from downstream to upstream.

[0035] 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.

[0036] (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 forming position in real time through feedback control. Correction of the image forming position is also called registration correction or registration adjustment.

[0037] 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.

[0038] 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.

[0039] 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).

[0040] 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.

[0041] 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 various misalignments of the image on the sheet of paper. Misalignment correction will be described in detail later.

[0042] 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.

[0043] 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."

[0044] 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 various amounts 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.

[0045] 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 the horizontal direction) perpendicular to the paper transport direction (hereinafter sometimes referred to as the vertical direction). A reader that reads an image by laser scanning in the horizontal direction may be used as the image sensor 38. Other image reading devices may also be used as the image sensor 38.

[0046] 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.

[0047] 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. Regarding correction of the image formation position, the flow of the correction process applied to the front side of the paper and the flow of the correction process applied to the back side of the paper are basically the same. Therefore, the correction process applied to the front side of the image will be described below.

[0048] 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 an output tray or output stacker is usually provided downstream of the post-processing device 18.

[0049] The operation of the image forming system 10 will be summarized below. A plurality of sheets of paper on which images have been formed are sequentially discharged downstream from the image forming unit 24. The image sensor 38 sequentially reads the images formed on the plurality of sheets of paper. The resulting plurality of read images are sequentially sent from the image sensor 38 to the control unit 32. The control unit 32 analyzes each read image and calculates a plurality of types of misalignment amount. The control unit 32 also corrects the image formation position relative to the paper based on these misalignment amounts.

[0050] The multiple types of misalignment include misalignment due to image shift in the vertical direction, misalignment due to image shift in the horizontal direction, misalignment due to image rotation, misalignment due to scale error, etc. In reality, the control unit 32 has a function to collectively correct all of these misalignments, but to facilitate understanding of the configuration and effects of the embodiment, the following will focus on one type of misalignment and the corresponding correction.

[0051] FIG. 2 shows an example configuration of the control unit 32. The control unit 32 has a processor 40 and a memory 42. Physically, the memory 42 is composed of a single memory or multiple memories. 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.

[0052] The image analyzer 44 has a deviation amount calculator 56. The deviation amount calculator 56 calculates the amount of deviation of the image relative to the paper for each scanned image 54 by analyzing the scanned image 54. Specifically, the deviation amount calculator 56 calculates the amount of deviation by comparing the positions of multiple marks included in the scanned image with multiple reference positions. The amount of deviation is the relative amount of deviation that occurs after correcting the image formation position. In the illustrated configuration example, the calculated amount of deviation is stored in the memory 42.

[0053] The memory 42 has a correction amount storage area 58 and a misalignment amount storage area 60. The correction amount storage area 58 stores the correction amount applied when forming an image on each sheet of paper. More specifically, the correction amount storage area 58 is used to store a plurality of correction amounts arranged in the order of the sheet number. The misalignment amount storage area 60 stores the misalignment amount calculated from each scanned image. More specifically, the misalignment amount storage area 60 is used to store a plurality of misalignment amounts arranged in the order of the sheet number.

[0054] The processor 40 manages the correspondence between the stored correction amounts and the stored misalignment amounts. That is, a specific correction amount applied when forming an image on a specific sheet of paper is associated with a specific misalignment amount calculated by reading the image formed on the specific sheet of paper. The correspondence between the multiple correction amounts and the multiple misalignment amounts may be managed by a management mechanism other than the processor 40. The correction amount storage area 58 and the misalignment amount storage area 60 each have, for example, a ring buffer structure or a stack structure.

[0055] The correction amount calculator 46 identifies the actual deviation amount based on the corresponding correction amount and deviation amount, and calculates the current correction amount based on the actual deviation amount. In practice, the correction amount calculator 46 calculates a smoothed actual deviation amount based on a plurality of correction amounts lined up on the time axis and a plurality of deviation amounts lined up on the time axis, and calculates the current correction amount based on the smoothed actual deviation amount. The calculation of the correction amount will be described in detail later.

[0056] 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 relative to the paper. The correction of the image forming position may include correction by electronic control as well as correction by mechanical control.

[0057] 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.

[0058] For example, if the previous sheet to be read is referred to as the first sheet and the read image obtained by reading the image on the first sheet is referred to as the first read image, a first deviation amount is calculated by analyzing the first read image. Meanwhile, a first correction amount corresponding to the first deviation amount is identified. The correction amount calculator 46 calculates a first actual deviation amount based on the first correction amount and the first deviation amount, and calculates a second correction amount, which is the current correction amount, based on the first actual deviation amount. When forming an image on the subsequent second sheet, the image formation position is corrected based on the second correction amount. In practice, the correction amount calculator 46 calculates a first smoothed actual deviation amount based on multiple actual deviation amounts including the first actual deviation amount, as described below, and calculates a second correction amount based on the first smoothed actual deviation amount.

[0059] The actual deviation amount is the deviation amount that would have occurred if the image formation position had not been corrected, that is, the original deviation amount or true deviation amount estimated by calculation. The actual deviation amount may also be expressed as an estimated actual deviation amount. The actual deviation amount only needs to be close to the true deviation amount, and it is not required that the actual deviation amount exactly matches the true deviation amount. The smoothed actual deviation amount is obtained by applying a smoothing operation to multiple actual deviation amounts lined up on the time axis. Examples of smoothing operations include an average value operation and a weighted average value operation.

[0060] Between the first sheet to be scanned and the second sheet to be image-formed, for example, there may be four or five sheets with images already formed on them. These sheets can be called waiting sheets. The difference between the timing of image formation and the timing of image scanning, or the time difference, usually varies depending on the paper size, paper transport speed, etc., so the number of waiting sheets also varies depending on these factors.

[0061] An example of misalignment is shown schematically in Figure 3. 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 3, the left-to-right direction is the paper transport direction, i.e., the vertical direction. The direction perpendicular to the vertical direction is the horizontal direction.

[0062] The image 70 is misaligned with respect to the paper 68. Specifically, reference numeral 74 indicates the amount of misalignment in the vertical direction, and reference numeral 76 indicates the amount of misalignment in the horizontal direction. While the paper 68 is being conveyed, the image 70 is read by the image sensor 38, 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 determining the amount of misalignment in the vertical direction 74 and the amount of misalignment in the horizontal direction 76.

[0063] Feedback control according to a comparative example will be described with reference to Figs. 4 and 5. In Fig. 4, the left-right direction is the paper transport direction. A plurality of sheets constituting a paper row 80 are lined up in the paper transport direction. n indicates the number of the sheet immediately after image formation. The correction amount applied when forming an image on that sheet is C n n+1 indicates the number of the paper on which the image will be formed. m indicates the number of the paper immediately after the image has been read. The amount of deviation calculated by that reading is r m The deviation amount corresponding to the paper specified by mm is r m-M is.

[0064] Reference numeral 82 indicates a number of sheets of paper waiting to be read, and reference numeral 84 indicates a moving average period. i ) indicates a moving average value, which is the average value of M+1 deviation amounts belonging to the moving average period 84. i takes values ​​from mM to m.

[0065] In the comparative example, the current correction amount C is calculated according to the following formula (1): n+1 is calculated.

number

[0066] In the above equation (1), G is the gain, which is a coefficient for adjusting the response. The first term on the right-hand side includes the moving average value mentioned above. Because the deviation fluctuates over time, the deviation is smoothed to stably calculate the correction amount. The second term on the right-hand side is the previous correction amount.

[0067] In FIG. 4, reference numeral 86 indicates reference to the smoothed deviation amount, and reference numeral 88 indicates reference to the previous correction amount. When the current correction amount is calculated based on the previous correction amount, the current correction amount is easily affected by the previous correction amount. In the above (1), there is a phase difference between the first and second terms on the right side, so responsiveness becomes an issue when calculating the current correction amount. In the comparative example, when a change in state such as jamming occurs, the resulting influence tends to remain for a long time.

[0068] Fig. 5 shows the correction results for the comparative example. Here, in formula (1), 10 is substituted for M and 0.1 is substituted for G. The horizontal axis indicates the number of sheets of paper, which corresponds to the time axis. The vertical axis indicates the amount of deviation and the amount of correction.

[0069] Waveform 90 shows the change in the amount of deviation that occurs when no correction is performed. Waveform 92 shows the change in the smoothed amount of deviation when correction is performed. Waveform 94 shows the change in the amount of correction calculated based on the smoothed amount of deviation. Waveform 96 shows the change in the amount of deviation after correction. In the comparative example, as shown by waveform 96, the amount of deviation converges to zero over time, but over the period until convergence, the amount of deviation fluctuates relatively greatly in both the positive and negative directions. In other words, poor responsiveness can be seen.

[0070] Next, feedback control according to the embodiment will be described with reference to Figs. 6 and 7. In Fig. 6, the left-right direction is the paper transport direction. A plurality of sheets constituting a paper row 98 are lined up in the paper transport direction. n indicates the number of the sheet immediately after image formation. The correction amount applied when forming an image on that sheet is C n n+1 indicates the number of the paper on which the image will be formed. m indicates the number of the paper immediately after the image has been read. The amount of deviation calculated by that reading is r m The deviation amount corresponding to the paper specified by mm is r m-M is.

[0071] Reference numeral 100 denotes a plurality of sheets of paper waiting to be read. In this embodiment, the actual amount of misalignment is calculated for each sheet of paper by subtracting the corresponding correction amount from the calculated amount of misalignment. The actual amount of misalignment is the amount of misalignment that would have occurred if the image formation position had not been corrected, and corresponds to the original or true amount of misalignment. Reference numeral 102 denotes the actual amount of misalignment r corresponding to the sheet of paper specified by m. m -C m where r m is the deviation amount, C m is the correction amount. Note that reference numeral 104 indicates the actual deviation amount r corresponding to the paper specified by mm. m-M -C m-M where r m-M is the deviation amount, C m-M is the correction amount.

[0072] Reference numeral 106 denotes the moving average period. Average(r i -C i ) indicates a moving average value, specifically, the average value of M+1 actual deviation amounts belonging to the moving average period 106. The moving average is one of the smoothing methods, and the moving average value can be called a smoothed actual deviation amount. Note that i takes values ​​from mM to m.

[0073] Specifically, the correction amount C is calculated according to the following formula (2): n+1 is calculated.

number

[0074] In equation (2), G is the gain, a coefficient for adjusting the response. The right-hand side includes the moving average value (i.e., the smoothed actual deviation amount). Because the actual deviation amount fluctuates over time, the actual deviation amount is smoothed to stably calculate the correction amount. Equation (2) does not include the previous correction amount. This avoids the problem of the influence of the previous correction amount remaining or the problem of delayed response. G may be changed in stages according to n. For example, G may be changed from 0 (0%) to 1 (100%) from the first to twentieth sheets. It is also possible to substitute 1 for G in equation (2), which would simplify the equation. The value assigned to G may be changed depending on the situation. For example, the value assigned to G may be changed according to the number of sheets waiting to be read or the time lag between the image formation timing and the image reading timing.

[0075] 6, reference numeral 108 indicates a reference to the smoothed actual deviation amount. Based on the smoothed actual deviation amount, the current correction amount C n+1 In this calculation, the previous correction amount C n There is no need to refer to

[0076] 7 shows the correction result according to the embodiment. Here, in formula (2), 10 is substituted for M and 1 is substituted for G. The horizontal axis indicates the number of sheets of paper, which corresponds to the time axis. The vertical axis indicates the amount of deviation and the amount of correction.

[0077] A waveform 110 containing many small waves indicates a change in the actual deviation amount. A flat waveform 112 indicates a change in the smoothed actual deviation amount. A waveform 114 indicates a change in the correction amount. A waveform 116 containing many small waves indicates a change in the deviation amount.

[0078] According to this embodiment, as shown by waveform 116, the deviation quickly converges to zero and remains at that converged state. No residual correction amount from the previous time is observed, and the responsiveness is extremely good. As a result, the accuracy of image formation position correction is improved.

[0079] FIG. 8 schematically shows a first information processing method according to the embodiment. As described with reference to FIG. 1, the memory 42 includes a correction amount storage area 58 and a deviation amount storage area 60. n indicates the paper number. The conveying direction corresponds to the time axis. The correction amount storage area 58 stores a plurality of correction amounts along the time axis. In the illustrated example, the plurality of correction amounts are associated with the paper number. The deviation amount storage area 60 stores a plurality of deviation amounts along the time axis. In the illustrated example, the plurality of deviation amounts are also associated with the paper number.

[0080] Reference numeral 120 indicates the current time. The correction amount has not yet been calculated. Reference numeral 122 indicates the timing when reading is completed. Reference numeral 124 indicates the period of time waiting for reading. Reference numeral 126 indicates a plurality of actual misalignment amounts corresponding to a plurality of sheets of paper. An area for storing these plurality of actual misalignment amounts may be provided in the memory 42. By adopting such a configuration, the calculated actual misalignment amounts can be reused, thereby reducing the amount of calculation.

[0081] The current correction amount 130 is calculated based on the M+1 actual deviation amounts belonging to the moving average period 128. The current correction amount 130 is used to control the image forming position (see reference numeral 132), and is also stored in the correction amount storage area 58 in the memory 42 (see reference numeral 134). The above process is repeated for each sheet of paper.

[0082] 9 schematically shows a second information processing method according to the embodiment. The memory 140 has a stack structure. Specifically, the memory 140 has a plurality of storage cells 144 corresponding to a plurality of cell numbers (or hierarchical numbers) 142. Every time a correction amount is calculated, the calculated correction amount is stored in a first cell of the memory 140. At that time, one or more correction amounts already stored are shifted downward.

[0083] The number of sheets of paper waiting to be read is managed, and prior to calculating the actual misalignment amount 146, a cell number, i.e., a memory address, corresponding to the misalignment amount is identified. A correction amount is read from a memory cell associated with that cell number. The actual misalignment amount 146 is calculated based on the read correction amount and the calculated misalignment amount. The calculated actual misalignment amount 146 is stored in memory 148.

[0084] Prior to calculating the correction amount 150, a plurality of actual deviation amounts within the moving average period are read from the memory 148, and the correction amount 150 is calculated based on the read values. The image forming position is corrected based on the calculated correction amount 150, and the calculated correction amount 150 is stored in the memory 140. In this way, the second information processing method does not require the storage of a plurality of deviation amounts.

[0085] In the above embodiment, when calculating the smoothed actual deviation amount, first, the average value of a plurality of correction amounts and the average value of a plurality of deviation amounts may be calculated, and then the difference between these two average values ​​may be calculated. In the above embodiment, when correcting the scale deviation, division based on the correction amount and the deviation amount may be performed.

[0086] 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.).

[0087] 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.

[0088] (Addendum) (((1))) an image forming unit that forms an image on a sheet; an image reading unit that reads the image formed on the paper; a processor that controls the image forming unit based on the read image obtained by reading the image reading unit; Including, The processor: determining a first deviation amount representing a deviation of the first image relative to the first sheet based on a first read image corresponding to the first image formed on the first sheet by the image forming unit and obtained by reading the first read image by the image reading unit; Identifying a first correction amount applied during formation of the first image; calculating a second correction amount for correcting the deviation based on the first deviation amount and the first correction amount; correcting a position where a second image is to be formed on a second sheet of paper in accordance with the second correction amount; An image forming system comprising: (((2))) In the image forming system described in (((1))), The processor: calculating a first actual deviation amount that would have occurred if the image forming position had not been corrected based on the first correction amount, based on the first deviation amount and the first correction amount; calculating the second correction amount based on the first actual deviation amount; An image forming system comprising: (((3))) In the image forming system described in (((1))), the processor calculates a first actual deviation amount by subtracting the first correction amount from the first deviation amount; calculating the second correction amount based on the first actual deviation amount; An image forming system comprising: (((4))) In the image forming system according to (((2))) or (((3))), The processor: calculating a first smoothed actual deviation amount based on a plurality of actual deviation amounts on a time axis including the first actual deviation amount; calculating the second correction amount based on the first smoothed actual deviation amount; An image forming system comprising: (((5))) In the image forming system according to any one of (((1))) to (((4))), The processor: storing the first correction amount in a memory when forming the first image; the first correction amount is determined by reading the first correction amount from the memory when calculating the second correction amount. An image forming system comprising: (((6))) In the image forming system described in (((5))), The processor: storing the plurality of correction amounts sequentially applied to the plurality of images in the memory in order; When reading out the correction amounts from the memory, the reading position of the memory is changed in accordance with the number of waiting sheets corresponding to the time difference between the image formation timing and the image reading timing. An image forming system comprising: (((7))) In the image forming system according to any one of (((1))) to (((6))), the processor sequentially corrects a plurality of positions for forming a plurality of images based on a plurality of read images during execution of a print job including a print command for a plurality of images; An image forming system comprising: (((8))) A program executed in an image forming system, The image forming system includes: an image forming unit that forms an image on a sheet; an image reading unit that reads the image formed on the paper; a processor that controls the image forming unit based on the read image obtained by reading the image reading unit; Including, Execution of the program causes the processor to: determining a first deviation amount representing a deviation of the first image relative to the first sheet based on a first read image corresponding to the first image formed on the first sheet by the image forming unit and obtained by reading the first read image by the image reading unit; Identifying a first correction amount applied during formation of the first image; calculating a second correction amount for correcting the deviation based on the first deviation amount and the first correction amount; correcting a position where a second image is to be formed on a second sheet of paper in accordance with the second correction amount; A program characterized by:

[0089] According to the image forming system of (((1))), correction can be performed that is more accurate and responsive than correction of the image forming position based on the relative amount of misalignment and the previous correction amount. According to the image forming system of (((2))), the image forming position can be corrected based on the original or true amount of misalignment. According to the image forming system of (((3))), the first actual deviation amount can be easily calculated. According to the image forming system of (((4))), the image forming position is stably corrected. According to the image forming system of (((5))), the first correction amount can be easily specified. According to the image forming system of (((6))), each correction amount can be accurately specified. According to the image forming system of (((7))), the image forming position is corrected in real time. According to the program (((8))), correction can be performed that is more accurate and responsive than correction of the image forming position based on the relative amount of misalignment and the previous correction amount. [Explanation of symbols]

[0090] 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, 42 memory, 44 image analyzer, 46 correction amount calculator, 48 controller.

Claims

1. an image forming unit that forms an image on a sheet; an image reading unit that reads the image formed on the paper; a processor that controls the image forming unit based on the read image obtained by reading the image reading unit; Including, The processor: determining a first deviation amount representing a deviation of the first image relative to the first sheet based on a first read image corresponding to the first image formed on the first sheet by the image forming unit and obtained by reading the first read image by the image reading unit; Identifying a first correction amount for misalignment correction applied when forming the first image; calculating a second correction amount based on the first deviation amount and the first correction amount; correcting a position where a second image is to be formed on a second sheet of paper in accordance with the second correction amount; An image forming system comprising:

2. 2. The image forming system according to claim 1, The processor: calculating a first actual deviation amount that would have occurred if the image forming position had not been corrected based on the first correction amount, based on the first deviation amount and the first correction amount; calculating the second correction amount based on the first actual deviation amount; An image forming system comprising:

3. 2. The image forming system according to claim 1, the processor calculates a first actual deviation amount by subtracting the first correction amount from the first deviation amount; calculating the second correction amount based on the first actual deviation amount; An image forming system comprising:

4. 4. The image forming system according to claim 2, wherein: The processor: calculating a first smoothed actual deviation amount based on a plurality of actual deviation amounts on a time axis including the first actual deviation amount; calculating the second correction amount based on the first smoothed actual deviation amount; An image forming system comprising:

5. 2. The image forming system according to claim 1, The processor: storing the first correction amount in a memory when forming the first image; the first correction amount is specified by reading the first correction amount from the memory when calculating the second correction amount. An image forming system comprising:

6. 6. The image forming system according to claim 5, The processor: storing the plurality of correction amounts sequentially applied to the plurality of images in the memory in order; When reading out the correction amounts from the memory, the reading position of the memory is changed in accordance with the number of waiting sheets corresponding to the time difference between the image formation timing and the image reading timing. An image forming system comprising:

7. 2. The image forming system according to claim 1, the processor sequentially corrects a plurality of positions for forming a plurality of images based on a plurality of read images during execution of a print job including a print command for a plurality of images; An image forming system comprising:

8. A program executed in an image forming system, The image forming system includes: an image forming unit that forms an image on a sheet; an image reading unit that reads the image formed on the paper; a processor that controls the image forming unit based on the read image obtained by reading the image reading unit; Including, Execution of the program causes the processor to: determining a first deviation amount representing a deviation of the first image relative to the first sheet based on a first read image corresponding to the first image formed on the first sheet by the image forming unit and obtained by reading the first read image by the image reading unit; Identifying a first correction amount for misalignment correction applied when forming the first image; calculating a second correction amount based on the first deviation amount and the first correction amount; correcting a position where a second image is to be formed on a second sheet of paper in accordance with the second correction amount; A program characterized by:

Images