Image forming device and control method therefor

Abstract

To provide an image forming device capable of suppressing deterioration in image position adjustment accuracy due to erroneous marker detection.SOLUTION: An image forming device provided herein comprises a printer (140) and a scanner (130). An MFP (100) configured to acquire a front / back misalignment adjustment value by printing and reading an adjustment chart uses markers of a shape represented by a marker (902) as adjustment chart markers.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present invention relates to an image forming system that performs a process for adjusting the formation position of an image on a sheet. The image forming apparatus used in this image forming system can be applied to various apparatuses such as copiers, printers, FAX machines, and multifunction machines thereof.

Background Art

[0002] Conventionally, in a printing apparatus (image processing apparatus) that forms an image on a sheet (paper), a function for adjusting the formation position of the image on the sheet (hereinafter referred to as "image position adjustment") has been used. In Patent Document 1, a technique for obtaining parameters for image position adjustment by printing an adjustment mark on a sheet and reading it with a reading device to obtain the positional relationship between the mark and the paper edge is disclosed. Further, as an example of the reading device, an automatic document feeder for sheets called ADF (Auto Document Feeder) is described. The parameters for image position adjustment are parameters that affect the cut shape for each cut sheet. Therefore, the operation of obtaining the parameters for image position adjustment is performed for each type of sheet.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] There is room for improvement in the configuration for obtaining adjustment coordinates from a rectangular pattern as in Patent Document 1. When dust adheres to the reading unit of the ADF, a streak-like pattern extending in the sub-scanning direction may occur in the read image, and there is a risk that this streak may be erroneously detected as being rectangular and the coordinates required for correct correction calculation may not be obtained.

[0005] In view of the above-mentioned problems, the present invention aims to provide an image forming apparatus capable of suppressing a decrease in image position adjustment accuracy due to erroneous detection of markers. [Means for solving the problem]

[0006] The present invention relates to an image forming apparatus comprising: an image forming unit for forming an image on a sheet; a reading unit for transporting the sheet and reading the image; means for causing the image forming unit to perform an image forming process for forming an image of a predetermined pattern on the sheet; and means for reading the sheet on which the image of the predetermined pattern has been formed with the reading unit, and obtaining adjustment values ​​to be used for further image forming processing based on the reading results, wherein the image of the predetermined pattern includes a marker formed near the corner of the sheet, and the marker is characterized in that a region enclosed by a plurality of sides, including sides that are not parallel to the short and long sides of the sheet, is filled in. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an image forming apparatus that can suppress the decrease in image position adjustment accuracy due to false detection of markers. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1(a) is a block diagram showing the configuration of the MFP. Figure 1(b) is a block diagram showing the configuration of the scanner. Figure 1(c) is a block diagram showing the configuration of the scanner. [Figure 2] This is a mechanical cross-sectional view showing the configuration of the MFP. [Figure 3] This diagram shows the usage sequence of this system. [Figure 4] Figure 4(a) shows the chart printing screen. Figure 4(b) shows the chart printing settings screen. Figure 4(c) shows the chart loading screen. Figure 4(d) shows the error screen. Figure 4(e) shows the completion screen. Figure 4(f) shows a modified version of the completion screen. Figure 4(g) shows a modified version of the completion screen. [Figure 5]This diagram shows a flowchart of the image position adjustment process. [Figure 6] This diagram shows a flowchart of the identification patch sampling process. [Figure 7] This diagram shows a flowchart of the marker sampling process. [Figure 8] Figure 8(a) shows the front surface of the adjustment chart. Figure 8(b) shows the back surface of the adjustment chart. Figure 8(c) is a diagram illustrating the measurement points on the adjustment chart. Figure 8(d) shows specific examples of each measurement point. [Figure 9] Figure 9(a) shows the sampling area of ​​the identification patch. Figure 9(b) shows the sampling area of ​​the marker. Figure 9(c) is a diagram illustrating the measurement points of the adjustment chart. Figure 9(d) shows specific examples of each measurement point. [Figure 10] Figure 10(a) shows the relationship between measured values, ideal values, and adjustment values. Figure 10(b) shows specific examples of adjustment values. [Figure 11] This diagram shows a flowchart of the image position adjustment process. [Figure 12] This figure shows a flowchart of the sampling process for identification patches and markers. [Figure 13] Figure 13(a) shows the front surface of the correction chart. Figure 13(b) shows the back surface of the correction chart. [Figure 14] This figure shows the region where the identification patch and marker sampling process takes place. [Figure 15] This is a flowchart of the coordinate transformation process. [Figure 16] This diagram illustrates the coordinate maps before and after a coordinate transformation process. [Figure 17] This diagram illustrates the coordinate information obtained when five correction charts are loaded. [Figure 18] Figure 18(a) is a diagram listing the coordinate information before the coordinate transformation. Figure 18(b) is a diagram listing the coordinate information after the coordinate transformation. [Modes for carrying out the invention]

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings by way of examples. Note that the examples given below do not limit the invention according to the claims, and not all combinations of the configurations and steps described in the examples are essential for the solution means of the invention. Some or all of the configurations and steps described in the examples may be replaced with equivalents. Also, some of the configurations and steps may be omitted.

[0010] (Example) In this example, an image forming apparatus will be described as an example, in which an adjustment chart (correction chart) is printed on a sheet in an image forming unit and the adjustment value of the image position (printing position) is acquired by reading this with an image reading unit.

[0011] <System> FIG. 1(a) is a system block diagram of an MFP 100 used as an image forming apparatus. As shown in FIG. 1, in the system of this example, the MFP 100 as an image forming apparatus and the PC 170 are communicably connected via the LAN 160. The MFP 100 receives data such as a print job from the PC 170 via the LAN 160.

[0012] FIG. 3 is a sequence diagram showing a usage example of this system. In this example, main exchanges are performed between the operator 300 and the MFP 100. Here, the state of processing from when the cassette library editing screen is displayed will be described.

[0013] In step 301 (hereinafter described as S301 etc.), the operator instructs the start of image position adjustment.

[0014] In S302, the image forming apparatus 100, the MFP 100 determines to start image position adjustment and displays an image position adjustment screen.

[0015] In S303, the operator, after checking the image position adjustment screen, sets the paper cassette to be adjusted and the method for performing the image position adjustment, and then instructs the MFP100 to perform the image position adjustment. Following this instruction, the MFP100 starts the image position adjustment process.

[0016] In S304, the MFP100 outputs an adjustment chart. The output adjustment chart (output) is placed on top of the output tray of the MFP100. The number of adjustment charts output at this time may be one or multiple. The number of adjustment charts output may be a preset number or a number specified by the operator. Along with the output of the adjustment chart, the MFP100 displays the adjustment chart reading screen.

[0017] In S305, the operator places the outputted adjustment chart on the image reading unit according to the notification on the reading screen and instructs the start of reading.

[0018] In S306, the MFP100 performs the process of reading the adjustment chart placed on the image reading unit.

[0019] In S307, the MFP100 obtains adjustment values ​​for the image position based on the image read from the adjustment chart.

[0020] In this embodiment, the image position of the paper feed cassette is adjusted as described above. Then, using the registered image position shift amount (adjustment value) for each paper feed cassette, image formation is performed as follows.

[0021] In S308, the operator uses the host computer to specify, configure, and execute print jobs to be output by the MFP100. For example, the operator configures a print job to print using sheets in a specific cassette, and then issues an execution command for the print job.

[0022] In S309, the host computer sends the print job specified by the operator to the MFP100.

[0023] In S310, the MFP100 executes a print job using paper in a specific cassette. At this time, the image position shift amount registered in the specific cassette is read from the cassette library and applied to the execution of the print job.

[0024] In S311, the MFP100 provides an output with adjusted image position.

[0025] As demonstrated in the above series of processes, once the image position adjustment process has linked the amount of image misalignment to the paper in the paper cassette, adjustments based on the amount of image misalignment will be made when a print job using this paper cassette is executed. Therefore, image position adjustment can be easily applied when executing a print job, reducing the workload on the operator.

[0026] <mfp> As shown in Figure 1(a), the MFP100 comprises a control unit 110, a scanner 130, a printer 140, and an operation unit 150.

[0027] Scanner 130 is a reading unit (reading device) that reads an image from a document.

[0028] The printer 140 is an image forming unit (image forming device) that forms an image on a sheet.

[0029] The control unit 150 is a user interface (operation panel) that outputs information to the operator and receives instructions from the operator. The control unit 150 is equipped with a display (display unit) and a speaker for outputting information. The control unit 150 is equipped with a touch panel and hard keys for inputting information.

[0030] The control unit 110 is a controller that comprehensively controls each component of the MFP 100. The control unit 110 is connected to the scanner 130 and printer 140 and controls the input and output of image information.

[0031] The control unit 110 includes a CPU 111, RAM 112, and ROM 113 as the minimum configuration of the controller. The control unit 110 also includes a storage unit 114, a network interface 115, a device interface 116, an operation interface 117, an image processing unit 118, and an image memory 119, and each component is connected by a communication means such as a bus.

[0032] The CPU111 is a general-purpose processor that performs various types of arithmetic operations.

[0033] RAM112 is volatile memory that functions as the working memory for CPU111.

[0034] ROM113 is a non-volatile memory that stores various programs, including the system's boot program.

[0035] The memory unit 114 is a storage device for storing information. For example, an HDD or SSD can be used for the memory unit 114. The memory unit 114 stores system software, image data, programs for controlling the operation of the MFP 100, and the like.

[0036] The program stored in the memory unit 114 is loaded into the RAM 112. The CPU 111 controls the operation of the MFP 100 based on the program loaded into the RAM 112.

[0037] The network interface 115 is a communication interface for connecting to a network. By connecting to LAN160, the network interface 115 handles the input and output of various information over the network. The network interface 115 may be an interface that supports wired communication, wireless communication, or both.

[0038] The device interface 116 connects the image input / output devices, such as the scanner 130 and printer 140, to the control unit 110 and performs synchronous / asynchronous conversion of image data.

[0039] The control unit interface 117 is an interface that connects the control unit 150 and the control unit 110. The control unit interface 117 outputs output information such as image data in order to display information on the display of the control unit 150. The control unit interface 117 also transmits input information entered by the user using the control unit 150 to the CPU 111.

[0040] The image processing unit 118 is a processor and circuit group specialized for image processing. The image processing unit 118 performs image processing on print data received via LAN. It also performs image processing on image data input and output from the device I / F 116.

[0041] The image memory 119 is a memory for temporarily expanding image data processed by the image processing unit 118.

[0042] The paper used for printing with the MFP100 is managed by the operator using a database called the cassette library. The cassette library is stored in the memory unit 114 or RAM 112, and is read and written to as needed by each software module. Details about the cassette library are omitted as they are publicly known.

[0043] <Scanner> Figure 1(b) is a block diagram showing the configuration of the scanner 130. Figure 2 is a mechanical cross-sectional view showing the structure of the image forming apparatus 100. The scanner 130 consists of a control unit 131 and a scanner mechanism 138. The control unit 131 includes a CPU 132, RAM 133, ROM 134, device I / F 135, image memory 136, and image processing unit 137.

[0044] The CPU 132 controls the operation of the scanner 130 and operates based on a program stored in the ROM 134 and loaded into the RAM 133. The device interface 135 connects to the control unit 110 and performs synchronous / asynchronous conversion of image data. The image memory 136 is a memory for temporarily loading image data input from the scanner mechanism 138. The control unit 131 transmits the image data stored in the image memory 136 to the control unit 110 based on an image transfer command received via the device interface 135.

[0045] The image processing unit 137 performs image processing on the image data expanded in the image memory 136.

[0046] The scanner mechanism 138 includes a pressure platen platen 240 for reading a document placed on a glass platen, and an ADF unit 230 for transporting and reading a document 232 placed on a platen platen 231. In the ADF unit 230, the document placed on the platen platen 231 is transported by transport rollers, and an image sensor such as a CIS reads the image.

[0047] <Printer> Figure 1(c) is a block diagram showing the configuration of the printer 140. The printer 140 consists of a control unit 131 and a printer mechanism 148. The control unit 141 includes a CPU 142, RAM 143, ROM 144, device I / F 145, image memory 146, and image processing unit 147.

[0048] The CPU 142 controls the operation of the printer 140 and operates based on a program stored in the ROM 144 and loaded into the RAM 143. The device interface 145 connects to the control unit 110 and performs synchronous / asynchronous conversion of image data. The image memory 146 is a memory for temporarily loading image data input from the control unit 110. The control unit 141 controls the printer mechanism 148 based on commands received via the device interface 145.

[0049] The printer mechanism 148 is a mechanical mechanism for performing image formation processing using an electrophotographic method. The printer mechanism 148 includes an engine control unit that controls each printing process (for example, paper feeding), and a control board housing that houses a printer controller, etc.

[0050] The various mechanisms that make up the engine section include an optical processing mechanism for latent image development and processing of the image, a transfer processing mechanism for transferring the image to the sheet P, and a fixing processing mechanism for fixing the toner image transferred to the sheet P. Additionally, there is a paper feeding mechanism for the sheet P and a transport mechanism for transporting the sheet P.

[0051] During color image formation, the optical processing mechanism includes a Y (yellow) station 220, an M (magenta) station 221, a C (cyan) station 222, and a K (black) station 223. The toner images developed at each station are sequentially transferred onto an intermediate transfer medium 252, thereby forming a full-color visible image on the intermediate transfer medium 252 (primary transfer).

[0052] Next, the sheet P fed from the sheet (paper) storage unit 210 is transported, and the sheet P is pressed against the intermediate transfer body 252 by the transfer roller 251. At the same time, a bias with characteristics opposite to that of the toner is applied to the transfer roller 251. As a result, the visible image formed on the intermediate transfer body 252 is transferred to the sheet P that is transported by the paper feeding mechanism in synchronization with the transport direction of the sheet P (sub-scanning direction) (secondary transfer).

[0053] After the secondary transfer is complete, the sheet P passes through the fuser unit 260, where the toner transferred to the sheet P is heated and melted, fixing it as an image on the sheet P. In the case of double-sided printing, the sheet passes through the inversion unit 270, is inverted back, and is introduced back into the transfer unit to transfer the image on the back side to the sheet P. Then, the sheet P passes through the fuser unit 260 again in the same manner, where the toner image on the sheet P is heated and fixed, and the sheet is discharged to the paper discharge unit 280, completing the printing process.

[0054] <Image position adjustment> This section provides a detailed explanation of how to obtain adjustment values ​​for image position using an adjustment chart.

[0055] Figure 8(a) shows the front surface of the adjustment chart. Figure 8(b) shows the back surface of the adjustment chart. Figure 8(c) is a diagram illustrating the measurement points on the adjustment chart. Figure 8(d) shows specific examples of each measurement point.

[0056] Figure 10(a) shows the relationship between measured values, ideal values, and adjustment values. Figure 10(b) shows specific examples of adjustment values.

[0057] As shown in Figure 8(a), this explanation uses a chart format in which marks for image position adjustment are printed on the paper as an example.

[0058] Chart 800 includes a marker 801 and an identification patch 802 as an image of a predetermined pattern. Chart 803 includes a marker 801 and an identification patch 804.

[0059] Marker 801 is an image used to measure the image formation position on the paper, and is formed near the corners of the four corners of the sheet.

[0060] Identification patches 802 and 804 are images used to identify the front and back sides and orientation of the chart.

[0061] This chart is used to measure the distances indicated by distances (A) to (J) in Figure 8(c). Distances (A) and (B) are the main scan direction length and sub scan direction length of the chart, respectively, and the ideal length is the paper length defined in the paper library.

[0062] The front and back sides and orientation of the chart surface are determined by the position and orientation of identification patches 802 and 804. For example, if the image detected by the identification patch sampling process is identification patch 802, that side is determined to be the front side of the chart surface. If the image detected by the identification patch sampling process is identification patch 804, that side is determined to be the back side of the chart surface. Furthermore, if the position of identification patch 802 or 804 is in the upper right region, the orientation is determined to be correct. On the other hand, if the position of identification patch 802 or 804 is in the lower left region, the orientation is determined to be reversed.

[0063] Distances (C) to (J) are the distances from the corner of marker 801 to the nearest edge of the paper, as shown in Figure 8(c). As shown in Figure 8(d), each measured distance is compiled into a table as a value and stored in RAM112. These values ​​are used to calculate the adjustment value.

[0064] Item 1411 describes the formula used to handle the measured values. Item 1412 represents the ideal value, and item 1413 describes how to calculate the adjustment value. The calculated adjustment value is stored in the storage unit 114 as an adjustment value set 1420, as shown in Figure 10(b). The adjustment value set 1420 includes a front adjustment value 1422 and a back adjustment value 1423. The front adjustment value 1422 and the back adjustment value 1423 are performed independently.

[0065] To obtain the adjustment values ​​mentioned above, the MFP100 in this embodiment performs a series of processes for the adjustment function. Figure 5 is a flowchart of the image position adjustment process.

[0066] In S501, CPU111 executes the chart printing process.

[0067] In one step of the chart printing process, the CPU 111 displays the image position adjustment screen 407 on the operation unit 150. As shown in Figure 4(a), the image position adjustment screen 407 includes a print start button and multiple cassette information, including cassette information 408 and 409. Here, cassette information 408 shows an example of cassette information where image position adjustment cannot be started due to reasons such as no paper. Cassette information 409 also shows an example of cassette information where image position adjustment cannot be started. It is desirable that the display method differs depending on whether the conditions for starting image adjustment are met. The user specifies the cassette information to be targeted for image position adjustment from among the multiple cassette information and selects the print start button 410. Upon receiving this instruction, the CPU 111 instructs the printer 140 to perform image formation based on the chart image for a predetermined number of copies. As a result, the output unit 280 outputs a predetermined number of charts as shown in Figures 8(a) and 8(b). Furthermore, the number of charts output with a single image position adjustment may be changed according to user instructions.

[0068] For example, as shown in Figure 4(b), the CPU 111 displays the output count setting screen 411 on the operation unit 150. The output count setting screen 411 includes an input form 412 for entering the set value for the number of output pages and an OK button. When the number of output pages is entered in the input form 412 and the OK button is subsequently selected, the CPU 111 stores the number set in the input form 412 in the RAM 112. This information is used when the print start button 410 is selected.

[0069] In S502, CPU111 executes the chart loading process.

[0070] In one step of the chart printing process, the CPU 111 displays the chart reading screen 401 on the operation unit 150. As shown in Figure 4(c), the chart reading screen 401 includes guidance information 402 indicating the orientation of the chart to be read and a start reading button 403. When the chart is set on the document glass 231 and the start reading button 403 is selected, the CPU 111 starts the reading process.

[0071] In S503, CPU111 performs identification patch sampling.

[0072] The identification patch sampling process involves determining the front and back sides and orientation of the chart.

[0073] In S504, CPU111 performs marker sampling.

[0074] In marker sampling, a process is performed to measure the image formation positions of the chart.

[0075] In S505, CPU111 performs paper edge sampling.

[0076] In the paper edge sampling process, the position of the paper edge, particularly the corners, is detected. Methods for detecting the paper edge include detecting the shading of the paper edge and observing the color difference between the paper edge and the area outside the paper. These known techniques will not be explained in this embodiment.

[0077] In S506, CPU111 performs coordinate transformation processing.

[0078] In the coordinate transformation process, the measured distances shown in Figures 8(c) and 8(d) are calculated based on the marker coordinate information obtained in S504 and the paper edge coordinate information based on S505. Furthermore, the coordinate information is corrected as needed during the calculation of the measured values. For example, if the chart is read in the wrong direction, the coordinates are rotated before proceeding with the process.

[0079] In S507, CPU111 performs the correction value calculation process.

[0080] In S507, the CPU 111 calculates a correction value (adjustment value) based on the information obtained from the previous processing. Once the calculation of the correction value is successfully completed, the CPU 111 displays screen 413, shown in Figure 4(e), on the operation unit 150. Screen 413 notifies that the correction is complete. Figure 4(e) shows the completion screen. If rotation processing is performed during coordinate transformation processing, screen 414, shown in Figure 4(g), may be displayed on the operation unit 150. Screen 413 notifies that the correction is complete and that rotation processing has been performed.

[0081] <Marker sampling process> The marker sampling process will now be explained. Figure 7 shows the marker sampling process.

[0082] In S701, the CPU 111 obtains the image size of the image read by the scanner 130.

[0083] In S702, CPU111 calculates the ideal coordinates of the marker based on the acquired image size and index value.

[0084] In S703, the CPU 111 initializes the index.

[0085] In S704, the CPU 111 sets the sampling area based on the acquired image size. 901 in FIG. 9(b) is a diagram showing the area when the index is 0 in S704. FIG. 9(b) is a diagram for explaining the sampling area in the marker sampling process. When the index is 0, a sampling area 901 of a square with a side of 1000 pixels located at the upper left end of the reading chart 900 is set.

[0086] In S705, the CPU 111 performs scanning in the main scanning direction and detects edges. FIG. 9(c) is a diagram schematically showing the state of the sampling process of S705. Here, a state where the marker 902 is included in the sampling area 901 is shown.

[0087] The pixel 903 at the start address is the pixel at the address determined in S704, and the CPU 111 refers to pixel values at a predetermined interval D1 in the direction indicated by the arrow 904 from this address. Pixels 903, 905, 906, and 907 are part of the pixels to be referred to. The interval D1 is, for example, an interval of 10 pixels.

[0088] The CPU 111 takes the difference between the pixel values of the referred pixels, and if the difference is greater than or equal to a predetermined threshold value, it determines that there is an edge in that section on the image. For example, the CPU 111 determines that there are edges in the section between pixel 905 and pixel 906 and in the section between pixel 906 and pixel 907.

[0089] Furthermore, the CPU 111 performs detailed sampling as shown in FIG. 9(d) for the section where an edge is determined to exist. In the detailed sampling of the section between pixel 905 and pixel 906, the CPU 111 refers to pixel values at an interval D2 (D2 < D1). The interval D2 is, for example, an interval of 1 pixel. As a result, it is determined that pixel 908 is an edge. The CPU 111 stores the coordinates of pixel 908 in the RAM 112.

[0090] In S706, the CPU 111 performs scanning in the sub-scanning direction and detects edges.

[0091] CPU 111 performs the same processing as S705, but with a change of direction. Figure 9(e) schematically shows the sampling process of S706. For example, CPU 111 determines that there are edges in the interval between pixel 909 and pixel 910, and in the interval between pixel 910 and pixel 911. CPU 111 further detects edges by sampling at interval D2 and stores the coordinates in RAM 112.

[0092] In S707, the CPU 111 calculates a linear equation by connecting multiple edges detected by operation in the main scanning direction, and calculates a linear equation by connecting multiple edges detected by scanning in the sub-scanning direction.

[0093] In S708, CPU111 finds the intersection points based on the equations of multiple lines. Figure 9(f) schematically shows how CPU111 calculates adjustment coordinates by finding the equations of lines and intersection points in S707 and S708 based on the coordinates obtained above. CPU111 finds the line that passes through the two furthest points among the obtained coordinates. In Figure 9(f), line 927 passes through edge 921 and edge 922, line 928 passes through edge 923 and edge 924, and line 929 passes through edge 925 and edge 926, respectively.

[0094] Next, CPU111 calculates the intersection coordinates 930, 931, and 932 from the line 927 to 929.

[0095] CPU111 stores the intersection coordinates in RAM112 using S710.

[0096] In S709, CPU111 determines whether an intersection point has been found. If an intersection point has been found (S709YES), CPU111 proceeds to S710. If an intersection point has not been found (S709NO), CPU111 proceeds to S713.

[0097] In S710, CPU111 performs the process of saving the intersection coordinates.

[0098] In S711, CPU111 performs index increment.

[0099] In S712, CPU111 compares the index with the number of markers. If the index is less than the number of markers (S712YES), CPU111 returns to S704. If the index is not less than the number of markers (S712NO), CPU111 terminates the series of operations.

[0100] In S713, the CPU 111 displays the sampling failure screen 406 shown in Figure 4(d) on the operation unit 150. Figure 4(d) shows the error screen.

[0101] The marker 902 in this embodiment is formed to have a straight line 927 at an angle (e.g., 45 degrees) that is not parallel to either the short side or the long side of the sheet. Therefore, misrecognition due to reading streaks caused by sheet transport can be suppressed. It is desirable that the straight line 927 has a sufficient angle with respect to both the short side and the long side. Therefore, it is desirable that the angle of the straight line 927 be within approximately 35 to 55 degrees from the short side and the long side. In addition, the marker 902 in this embodiment is a triangle (isosceles triangle) with sides 927, 928, and 929, and the inside of the sides is filled with pixels. With such a configuration, misrecognition caused by image smudges caused by hair or other debris adhering to the chart can be suppressed. Furthermore, even when referring to pixel values ​​at intervals such as interval D1, the marker can be easily detected. Therefore, marker detection can be performed quickly. It is also desirable that the identification patches 802 and 804 have sides and are similarly filled in. However, it would be good to make the size and other specifications different to distinguish it from the Marker 801.

[0102] <Identification Patch Sampling Process> The identification patch sampling process will now be explained. Figure 6 is a flowchart of the identification patch sampling process. In S601, the CPU 111 obtains the image size of the image read by the scanner 130.

[0103] In S602, the CPU 111 calculates the ideal coordinates of the identification patch based on the acquired image size.

[0104] In S603, CPU111 performs index initialization.

[0105] In S604, the CPU 111 sets the sampling area based on the acquired image size and index value. Figure 9(a) is a diagram illustrating the sampling area in the identification patch sampling process. When the index is 0, sampling is performed in the sampling area 951 located in the upper right center of the reading chart 900. In this embodiment, the sampling area 951 is a square area with sides of 2000 pixels, with its center point located at three-quarters of the main scan image size and one-quarter of the sub-scan image size.

[0106] In S605, the CPU 111 performs scanning in the main scanning direction and detects edges. Here, the same processing as described in Figures 9(c) and 9(d) is performed.

[0107] In S606, the CPU 111 performs scanning in the sub-scanning direction and detects edges.

[0108] Here, the same process as described in Figure 9(e) is performed.

[0109] In S607, the CPU 111 calculates a linear equation by connecting multiple edges detected by the operation in the main scanning direction, and calculates a linear equation by connecting multiple edges detected by scanning in the sub-scanning direction.

[0110] In S608, CPU111 finds the intersection points based on the equations of multiple lines. Here, the same process as described in Figure 9(f) is performed.

[0111] In S609, CPU111 determines whether an intersection point has been found. If an intersection point has been found (S609YES), CPU111 proceeds to S610. If an intersection point has not been found (S609NO), CPU111 proceeds to S611.

[0112] In S610, the CPU 111 determines the front / back and mounting orientation.

[0113] In S611, CPU111 performs index increment.

[0114] In S612, CPU111 determines whether the index is less than 2. If the index is less than 2 (S612YES), CPU111 returns to S604. If the index is not less than 2 (S612NO), CPU111 proceeds to S613.

[0115] In S613, the CPU 111 displays a sampling failure screen 406 on the operation unit 150.

[0116] <Remarks> By following the above procedure, image position adjustment can be performed in a way that is less affected by the streaky patterns in scanned images caused by dust in the ADF's scanning area. Furthermore, because the scanned image can be judged and corrected appropriately, users can utilize this function without having to worry about the correct placement of the document.

[0117] (Example 2) In Example 1, a configuration was described in which the identification patch sampling process and the marker sampling process are performed in separate steps. When an identification patch is image-formed separately from the adjustment marks for the purpose of determining the front / back and orientation of a sheet, it is desirable to suppress false detection of this identification patch as well. Furthermore, it is desirable to have a configuration that can appropriately detect each even in sheets where adjustment marks and identification patches are mixed. In this embodiment, the objective is to provide an image forming apparatus that can appropriately detect each in a configuration using an adjustment chart in which adjustment markers and identification patches for front / back and orientation are mixed. In Example 2, a configuration in which the identification patch sampling process and the marker sampling process are performed together at one time is described. Note that Example 2 is the same as Example 1 except for the feature parts. Therefore, the same reference numerals are used for the same components, and their detailed explanation is omitted.

[0118] Figure 11 is a flowchart showing the image position adjustment process in Example 2. The difference from the overall adjustment function flow of Example 1 shown in Figure 5 is that, in Example 2, the identification patch and marker, which were sampled separately in S503 and S504, are sampled simultaneously in S1501.

[0119] <Marker / Identification Patch Sampling Process> Figure 12 shows a flowchart of the identification patch and marker sampling process. Steps S601 to S610 and S613 are the same as the flow in Example 1 shown in Figures 6 and 7, so they are omitted. The process from S1611 onwards will be explained below.

[0120] If CPU111 is S1611YES and S1612YES, it performs the process in S1613; otherwise, it proceeds to the process from S1614 onwards.

[0121] In S1613, CPU111 determines the front / back and orientation of the chart surface currently being sampled based on the position and orientation of the detected identification patch, and saves the results.

[0122] CPU111 increments the index in S1614 and compares the index with the number of markers in S1615.

[0123] If CPU111 is S1615YES, it will repeat the process from S604 onwards.

[0124] CPU111 terminates processing if S1615NO is detected.

[0125] Figure 13(a) shows the front surface of the correction chart. Figure 13(b) shows the back surface of the correction chart. In this embodiment, the case where the number of markers is 4 will be explained as an example.

[0126] The identification patches use a filled right-angled isosceles triangle, identical in shape to the marker, and one is placed on each of the front and back sides of the chart. The placement of the identification patches on both the front and back sides is within the sampling area of ​​a specific marker, and inside the paper relative to this marker. In this embodiment, identification patches 1702 and 1704 are within the sampling area 1705 of marker 1701, and inside the paper relative to marker 1701, i.e., below the bottom edge and to the left of the left edge of marker 1701. This specific marker can be any marker that exists in the same position when the chart is rotated 180 degrees, and is not limited to the position shown in Figure 13.

[0127] Furthermore, the identification patches are oriented so that their equal sides are parallel to the edges of the paper. Identification patch 1702 on the front side is oriented so that the right angle of the right-angled isosceles triangle is in the lower left corner, while identification patch 1704 on the back side is oriented so that the right angle of the right-angled isosceles triangle is in the lower right corner.

[0128] In Example 2, the identification patch is detected within the same sampling area as the marker, but this placement makes it possible to determine whether the detected edge is an identification patch or a marker.

[0129] Figure 14 shows the region where identification patches and marker sampling are performed.

[0130] In Example 2, sampling is performed using S1501.

[0131] As described in Example 1, in S604, the CPU 111 determines the sampling area according to the index value. For the sampling area of ​​the loaded chart image, the sampling area when the index is 0 is designated as area 1801. The sampling area when the index is 1 is designated as area 1802. The sampling area when the index is 2 is designated as area 1803. The sampling area when the index is 3 is designated as area 1804. Here, area 1801 is a square area with sides of 3000 pixels located at the upper left corner of the image, area 1802 at the upper right corner of the image, area 1803 at the lower left corner of the image, and area 1804 at the lower right corner of the image. At this time, the identification patch is detected in areas 1802 or 1803 (S1611YES and S1612YES). Based on the placement of the identification patches as described above, the CPU 111 determines that when an identification patch is detected in area 1802, the chart is placed upright, and when it is detected in area 1803, it is placed upside down. Furthermore, if the right-angle portion of the identification patch detected in area 1802 is at the bottom left, or if the right-angle portion of the identification patch detected in area 1803 is at the top right, the CPU 111 determines that the read chart image is the front side and the other side is the back side. Conversely, if the right-angle portion of the identification patch detected in area 1802 is at the bottom right, or if the right-angle portion of the identification patch detected in area 1803 is at the top left, the CPU 111 determines that the side of the chart image from which it was read is the back side and the other side is the front side. The CPU 111 stores the information regarding the front / back side and placement orientation of the chart, determined from these detected identification patches, in the RAM 112 (S1613).

[0132] <Remarks> By following the above procedure, this embodiment makes it possible to obtain appropriate correction results when performing image position adjustment by sheet reading using an ADF while keeping the number of samplings low.

[0133] <Coordinate transformation process> This embodiment aims to provide an image forming apparatus that can appropriately adjust the image position even if the orientation of the sheet placed by the user differs from a predetermined orientation.

[0134] Figure 15 is a flowchart illustrating the process of converting the marker coordinates determined in S504 and the paper edge coordinates determined in S505. Distances based on multiple coordinates are converted to measured values ​​based on the calculation formula shown in Figure 10(a). If a chart is read with its orientation upside down, a orientation correction process is performed.

[0135] In S1001, the CPU 111 checks the result of the determination in S610 regarding whether the mounting orientation is correct. If there is an error in the mounting orientation (for example, if it is mounted upside down) (S1001 NO), the CPU 111 proceeds to S1002. If it is determined that the orientation is correct (S1002 YES), the CPU 111 proceeds to S1003.

[0136] In S1002, the CPU 111 converts the marker coordinates determined in S504 and the paper edge coordinates determined in S505 to reflect the state in which the chart was placed in the correct orientation, and stores them in the RAM 112.

[0137] Figure 16 illustrates the coordinate maps before and after transformation due to the coordinate transformation process. In Figure 16, the explanation uses the pre-transformation coordinate map 1100 and the post-transformation coordinate map 1101. In the pre-transformation coordinate map 1100 and post-transformation coordinate map 1101, the width of the coordinate map image is X and the height is Y. In the pre-transformation coordinate map 1100, the detected paper edge coordinates are arranged from (x1, y1) to (x4, y4) in the order of top left, top right, bottom right, and bottom left of the image. Also, in the pre-transformation coordinate map 1100, the marker coordinates are arranged from (x5, y5) to (x8, y8) in the order of top left, top right, bottom right, and bottom left of the image. A process is performed to transform this pre-transformation coordinate map 1100 into the post-transformation coordinate map 1101.

[0138] In the transformed coordinate map 1101, the coordinates corresponding to what would occur if the image were rotated 180 degrees and sampled with the correct image orientation are placed. For example, the coordinates (x1, y1) of the top left edge of the paper become (X-x1, Y-y1), which represents the coordinates of the bottom right edge of the paper. In other words, the coordinates representing the bottom right edge of the paper are replaced with (X-x1, Y-y1). Similar coordinate transformations are performed for other points, and the coordinates are stored after swapping the top left and bottom right, and the top right and bottom left.

[0139] This section explains how to load five double-sided charts for correction using the ADF (Automatic Document Feeder). The number of charts loaded should match the number of charts output.

[0140] This figure illustrates the coordinate information obtained when five correction charts are read. It shows the read images of both sides (4 pages) of the first and fifth charts, obtained when the first chart is set up with the correct orientation (top and bottom, front and back) and the fifth chart is set up upside down with the correct orientation (front and back). Although not all are shown, by sampling these images, coordinates for 8 points, including paper edge coordinates and marker coordinates, can be obtained, similar to Figure 16. Assume that all images have width X and height Y.

[0141] Figure 18(a) is a diagram listing the coordinate information before coordinate transformation. Figure 18(a) shows examples of paper edge coordinates and marker coordinates detected in S504 and S505 for the four pages shown in Figure 17. Figure 18(b) is a diagram listing the coordinate information after coordinate transformation. Figure 18(b) shows the results of performing the processing shown in the flow of Figure 15 for each page. Pages 1 and 2, which correspond to the first chart which has the correct up and down orientation, do not undergo coordinate transformation, while pages 9 and 10, which correspond to the fifth chart which is upside down, undergo the aforementioned coordinate transformation. Through this series of processes, the coordinates of all page images become corresponding to the correct orientation. In S1003, CPU 111 acquires measurement values ​​based on the calculation formula described in Figure 10(a). Based on these measurement values, correction values ​​are calculated in S507.

[0142] Alternatively, in addition to the method described above, one could first sample the identification patch and then rotate the scanned image by 180 degrees before performing marker and paper edge sampling. However, in order to perform image position adjustment with high accuracy, it is necessary to sample relatively high-resolution images, and since rotating the image takes time, the method of swapping coordinates as described above is adopted.

[0143] <Remarks> By following the above procedure, it is possible to determine the front / back and orientation of a sheet using a patch that is less affected by the streaky patterns in scanned images caused by dust in the ADF's scanning area. Furthermore, because the scanned image can be judged and corrected appropriately, users can utilize this function without having to worry about the correct placement of the document.

[0144] (Other examples) The present invention can also be realized by supplying a program that implements one or more of the functions of the above-described embodiments to a system or device via a network or storage medium, and by having one or more processors in the computer of that system or device read and execute the program. It can also be realized by a circuit (e.g., an ASIC) that implements one or more functions.

[0145] Furthermore, the present invention may be applied to a system consisting of multiple devices or to a device consisting of a single device. For example, the functionality may be realized by configuring a part of the software module to run on an external server and obtaining the results processed on the external server. For example, the storage unit for storing data may be provided within the external server.

[0146] Although the example described its application to image position adjustment, it can be similarly applied to other functions that read charts with an ADF and perform corrections.

[0147] The present invention is not limited to the embodiments described above, and various modifications (including organic combinations of each embodiment) are possible based on the spirit of the invention, and these are not excluded from the scope of the invention. In other words, all configurations that combine the above-described embodiments and their modified forms are included in the present invention.

[0148] The meanings of the abbreviations used in the examples are as follows: ADF stands for Auto Document Feeder. ASIC stands for Application Specific Integrated Circuit. CPU stands for Central Processing Unit. FAX stands for Facsimile. HDD stands for Hard Disk Drive. HTML stands for Hyper Text Markup Language. LAN stands for Local Area Network. MFP stands for Multi Function Peripheral. PC stands for Personal Computer. RAM stands for Random-Access Memory. ROM stands for Read Only Memory. SSD stands for Solid State Drive. [Explanation of Symbols]

[0149] 100 MFP (Image Forming Machine) 130 Scanner unit (reading unit) 140 Printer section (image forming section) 150 Operation section (display section) 801 Marker< / mfp>

Claims

1. an image forming means for forming an image on a sheet; a reading means for reading the image formed on the sheet; an acquisition unit that acquires an adjustment value for adjusting a further image formation position based on the result of reading, by the reading unit, a sheet on which an image of a predetermined pattern has been formed by the image forming unit, An image forming apparatus characterized in that the image of the specified pattern has a marker formed near a corner of the sheet, and the marker is a marker in which an area surrounded by multiple sides including an edge parallel to the long side of the sheet, an edge parallel to the short side of the sheet, and an edge that is not parallel to the short side or long side of the sheet is filled in.

2. The image forming apparatus further comprises a conveying means for conveying the sheet on which the image is formed, 2. The image forming apparatus according to claim 1, wherein the reading means reads the image formed on the sheet conveyed by the conveying means.

3. 3. The image forming apparatus according to claim 1, wherein the image of the predetermined pattern has markers near each of the four corners of the sheet.

4. 4. The image forming apparatus according to claim 1, wherein the marker is a triangle.

5. 5. The image forming apparatus according to claim 4, wherein the marker is an isosceles triangle.

6. 6. The image forming apparatus according to claim 1, further comprising a detection unit that detects the marker by referencing pixels at predetermined intervals.

7. 7. The image forming apparatus according to claim 1, wherein the predetermined pattern further comprises an identification patch, the identification patch being a patch for distinguishing between the front and back sides of a sheet.

8. 8. The image forming apparatus according to claim 1, wherein the predetermined pattern further comprises an identification patch, the identification patch being a patch for determining the orientation of the sheet.

9. a display means for displaying information; 9. The image forming apparatus according to claim 1, further comprising a display control means for causing the display means to display a screen prompting the user to set the sheet on which the image of the predetermined pattern has been formed into the reading means.

10. 10. The image forming apparatus according to claim 9, wherein the screen includes information about the orientation of a set of sheets on which an image of the predetermined pattern is formed.

11. 1. A control method for an image forming apparatus having an image forming unit that forms an image on a sheet and a reading unit that reads the image formed on the sheet, comprising: an acquisition step of acquiring an adjustment value for adjusting a further image formation position based on the result of reading, by the reading means, a sheet on which an image of a predetermined pattern has been formed by the image forming means; A control method characterized in that the image of the specified pattern has a marker formed near a corner of the sheet, and the marker is a marker in which an area surrounded by multiple sides including an edge parallel to the long side of the sheet, an edge parallel to the short side of the sheet, and an edge not parallel to the short side or long side of the sheet is filled in.

Images