Image processing method and image formation apparatus

Abstract

To distinctively detect scratches or stains on a surface of a conveyor belt and a sheet(s) on the conveyor belt.SOLUTION: A line sensor 6 is arranged at a specified position along a conveyor belt 320. A processor 80 processes plural line image data sequentially obtainable by the line sensor 6. Regarding the respective plural line image data, the processor 80 determines whether they are irregular data including plural irregular pixel values, each of which is a pixel value outside an allowable range and in which the number of the plural irregular pixel values exceeds the standard number of pixels (S202). The processor 80 detects the arrival of each sheet to the specified position when, in the plural line image data, the number of the sequential irregular data reaches a standard sequential number (S206).SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to an image processing method and an image forming apparatus for processing data obtained by a line sensor that indicates the state of a conveyor belt that conveys a sheet. [Background technology]

[0002] An image forming apparatus may include a belt conveying device that conveys a sheet by a rotating conveying belt, and a printing device that forms an image on the sheet conveyed by the conveying belt. For example, the printing device forms an image on the sheet by an inkjet method.

[0003] In the image forming apparatus, a sensor for detecting the sheet is disposed at a specific position along the conveyor belt, and the detection result of the sheet by the sensor is used to control the timing of starting image formation by the printing device.

[0004] For example, a reflective optical sensor may be disposed opposite the conveyor belt, and a control unit may determine the presence or absence of the sheet on the conveyor belt and a defect in the conveyor belt based on the detection level of the reflected light by the reflective optical sensor (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2021-169358 Summary of the Invention [Problem to be solved by the invention]

[0006] However, there are cases where the light reflection characteristics of scratches or stains on the surface of the conveyor belt are similar to the light reflection characteristics of the sheet on the conveyor belt, and in this case, the scratches or stains on the surface of the conveyor belt may be erroneously detected as the sheet.

[0007] SUMMARY OF THE INVENTION An object of the present invention is to provide an image processing method and an image forming apparatus that can distinguish and detect scratches or stains on the surface of a conveyor belt from a sheet on the conveyor belt. [Means for solving the problem]

[0008] An image processing method according to one aspect of the present invention processes a plurality of line image data sequentially obtained by a line sensor disposed along a second direction intersecting a first direction at a specific position along a conveyor belt that can convey a sheet in the first direction by rotating. The image processing method includes a processor determining, for each of the plurality of line image data, whether the plurality of line image data is anomalous data that includes a plurality of anomalous pixel values ​​that are pixel values ​​outside an allowable range and the number of the plurality of anomalous pixel values ​​exceeds a reference pixel number. The image processing method further includes the processor detecting that the sheet has reached the specific position when the number of consecutive anomalous data in the plurality of line image data reaches a reference consecutive number.

[0009] An image processing method according to another aspect of the present invention processes a plurality of line image data sequentially obtained by a line sensor arranged in a second direction intersecting a first direction at a specific position along a conveyor belt that can convey a sheet in the first direction by rotating. The image processing method includes a processor determining, for each of the plurality of line image data, whether the plurality of line image data is anomalous data that includes a plurality of anomalous pixel values ​​that are pixel values ​​outside an allowable range and the number of the plurality of anomalous pixel values ​​exceeds a reference pixel number. The image processing method further includes the processor determining a degree of abnormality of the conveyor belt according to the number of consecutive anomalous data in the plurality of line image data.

[0010] According to another aspect of the present invention, an image forming apparatus includes a conveyor belt, a line sensor, a printing device, and the processor that implements the image processing method. The conveyor belt is capable of conveying a sheet along a first direction by rotating. The line sensor is disposed along a second direction intersecting the first direction at a specific position along the conveyor belt. The printing device forms an image on the sheet conveyed by the conveyor belt. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide an image processing method and an image forming apparatus that can distinguish and detect scratches or stains on the surface of a conveyor belt from a sheet on the conveyor belt. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram illustrating the configuration of an image forming apparatus according to an embodiment. [Figure 2] FIG. 2 is a block diagram showing the configuration of a control device in the image forming apparatus according to the embodiment. [Figure 3] FIG. 3 is a plan view of the vicinity of a sheet feed portion onto a conveyor belt in the image forming apparatus according to the embodiment. [Figure 4] FIG. 4 is a flowchart showing an example of a procedure for belt abnormality determination processing in the image forming apparatus according to the embodiment. [Figure 5] FIG. 5 is a flowchart showing an example of a procedure for sheet detection processing in the image forming apparatus according to the embodiment. [Figure 6] FIG. 6 is a diagram schematically showing a plurality of line image data obtained in the image forming apparatus according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the following embodiment is an example of the present invention, and does not limit the technical scope of the present invention.

[0014] [Configuration of image forming apparatus 10] The image forming apparatus 10 according to the embodiment includes a sheet storage unit 1, a sheet conveying device 3, and a printing device 4. The image forming apparatus 10 further includes a drying device 5, an operating device 801, a display device 802, a control device 8, and the like.

[0015] The sheet transport device 3 includes a sheet feeding mechanism 30, a plurality of pairs of transport rollers 31, a first belt transport device 32, a second belt transport device 33, and a discharge roller pair .

[0016] The sheet feeding mechanism 30 feeds the sheet 9 in the sheet storage unit 1 to a first conveying path 301. A plurality of pairs of conveying rollers 31 convey the sheet 9 along the first conveying path 301, and further sends the sheet 9 from the first conveying path 301 to a first belt conveying device 32.

[0017] The first belt conveying device 32 takes over from the plurality of pairs of conveying rollers 31 to convey the sheet 9, and sends the sheet 9 to the second belt conveying device 33. The first belt conveying device 32 includes a circular conveying belt 320, a plurality of support rollers 321, and a suction device 322.

[0018] The plurality of support rollers 321 rotatably support the conveyor belt 320. A belt drive motor (not shown) rotates one of the plurality of support rollers 321, causing the conveyor belt 320 to rotate.

[0019] The plurality of pairs of conveying rollers 31 convey the sheet 9 onto the upper surface of the conveying belt 320. The sheet feeding mechanism 30 and the plurality of pairs of conveying rollers 31 are an example of a front-stage conveying mechanism arranged upstream of the conveying belt 320 in the sheet conveying direction FD1.

[0020] The rotating conveyor belt 320 further conveys the sheet 9 that has been conveyed onto its upper surface. The suction device 322 causes the sheet 9 to adhere to the upper surface of the conveyor belt 320 by suctioning air.

[0021] The second belt conveying device 33 takes over from the first belt conveying device 32 to convey the sheet 9 , and then sends the sheet 9 out to the second conveying path 302 .

[0022] The discharge roller pair 34 conveys the sheet 9 along the second conveying path 302, and then sends the sheet 9 from the second conveying path 302 to a subsequent stage. For example, the subsequent stage is a discharge tray or a post-processing device.

[0023] The printing device 4 performs a printing process on the sheet 9 conveyed by the conveyor belt 320 of the first belt conveying device 32. The printing process is a process of forming an image on the sheet 9.

[0024] In this embodiment, the printing device 4 performs the printing process by an inkjet method. That is, the printing device 4 forms an image on the sheet 9 by ejecting ink onto the sheet 9. The ink is an example of a developer.

[0025] The printing device 4 has a plurality of ink heads 41 and a plurality of ink supply units 42, each corresponding to a different color ink. Specifically, the printing device 4 has four ink heads 41 and four ink supply units 42, corresponding to yellow, magenta, cyan, and black.

[0026] Each of the ink heads 41 has a plurality of ejection nozzles 41a that eject ink. The ink heads 41 are fixed at positions facing the surface of the conveyor belt 320 of the first belt conveying device 32. The ink supply units 42 each contain ink of a different color and supply the ink to the ink heads 41.

[0027] The drying device 5 dries the ink image on the sheet 9 by blowing hot air onto the sheet 9 being conveyed by the second belt conveying device 33 .

[0028] 1 and 3, the first direction D1 is a direction along the sheet conveying direction FD1 in the first belt conveying device 32. The sheet conveying direction FD1 is a direction in which the sheet 9 is conveyed by the first belt conveying device 32.

[0029] 1 and 3, the second direction D2 is a direction that intersects with the first direction D1. In this embodiment, the second direction D2 is a direction that is perpendicular to the first direction D1. The second direction D2 is the main scanning direction in the printing process, and the first direction D1 is the sub-scanning direction in the printing process.

[0030] The operation device 801 detects operations by a person. For example, the operation device 801 includes a plurality of operation buttons and a touch panel. The display device 802 is capable of displaying various types of information. For example, the display device 802 is a panel display device such as a liquid crystal display panel.

[0031] As shown in FIG. 2, the control device 8 includes a central processing unit (CPU) 80, a random access memory (RAM) 81, a secondary storage device 82, a signal interface 83, a communication device 84, and the like.

[0032] The CPU 80 executes various control and data processing operations by executing computer programs. The RAM 81 temporarily stores the computer programs executed by the CPU 80 and various data.

[0033] The secondary storage device 82 is a computer-readable non-volatile storage device. The secondary storage device 82 stores the computer programs executed by the CPU 80 and various data. For example, one or both of a flash memory and a hard disk drive may be used as the secondary storage device 82.

[0034] The signal interface 83 converts the detection signals of the various sensors into digital detection data and transmits the detection data to the CPU 80. Furthermore, the signal interface 83 converts the control commands output from the CPU 80 into control signals and transmits the control signals to the devices to be controlled.

[0035] The communication device 84 communicates with other devices such as the host device 7 through the network 70. The CPU 80 communicates with other devices through the communication device 84. The host device 7 is an information processing device that requests the image forming device 10 to perform the print processing.

[0036] The CPU 80 includes a plurality of processing modules that are realized by executing the computer programs, including a main control unit 8a and a print control unit 8b (see FIG. 2).

[0037] The main control unit 8a executes start control for starting various processes in response to an operation on the operation device 801 or a processing request received through the communication device 84.

[0038] The print control unit 8b controls the sheet transport device 3 and the print device 4. The print control unit 8b controls the sheet transport device 3, thereby controlling the transport of the sheet 9.

[0039] Furthermore, the print control unit 8b causes the printing device 4 to execute the print process in synchronization with the conveyance of the sheet 9. Furthermore, the print control unit 8b causes the drying device 5 to operate when the print process is executed for the image to be printed.

[0040] The image forming apparatus 10 further includes a line sensor 6 arranged in a specific position P1 along the conveyor belt 320 of the first belt conveying device 32 in the second direction D2 (see FIGS. 1 and 3). The specific position P1 is a position upstream of the multiple ink heads 41 of the printing device 4 in the sheet conveying direction FD1.

[0041] The line sensor 6 is an image sensor that reads an image of an area along the second direction D2 at the specific position P1.

[0042] The line sensor 6 includes a light-emitting unit 6a and a plurality of photoelectric conversion elements 6b (see FIG. 3). The light-emitting unit 6a irradiates light onto a band-shaped region along the second direction D2 on the surface of the conveyor belt 320. The plurality of photoelectric conversion elements 6b are arranged in the second direction D2.

[0043] The photoelectric conversion elements 6b each detect the amount of diffusely reflected light on the surface of the conveyor belt 320 and output a plurality of pixel signals representing the detected light amounts. The pixel signals are converted into a plurality of pixel data by the signal interface 83, and the pixel data are transmitted to the CPU 80 as line image data LD1 (see FIG. 2).

[0044] That is, the line image data LD1 is the plurality of pixel data obtained by the operation of the line sensor 6. The line image data LD1 is used to detect the sheet 9 reaching the specific position P1.

[0045] In this embodiment, the plurality of processing modules includes an image processing unit 8c that processes line image data LD1. The image processing unit 8c detects the sheet 9 that has reached a specific position P1 by processing the line image data LD1. The detection result of the sheet 9 by the image processing unit 8c is used to control the timing of the start of image formation by the printing device 4.

[0046] Incidentally, there are cases where the light reflection characteristics of scratches or stains on the surface of the conveyor belt 320 are similar to the light reflection characteristics of the sheet 9 on the conveyor belt 320. In this case, there is a risk that the scratches or stains on the surface of the conveyor belt 320 will be erroneously detected as the sheet 9.

[0047] In this embodiment, the image processing unit 8c executes a belt abnormality determination process and a sheet detection process, which will be described later. The abnormality determination process and the sheet detection process include processes for distinguishing between scratches or stains on the surface of the conveyor belt 320 and the sheet 9 on the conveyor belt 320.

[0048] The abnormality determination process and the sheet detection process are examples of processes that realize an image processing method for processing a plurality of line image data LD1 sequentially obtained by the line sensor 6.

[0049] Note that some or all of the processes executed by the CPU 80 may be executed by a DSP (Digital Signal Processor) or an SoC (System on a Chip), etc. The CPU 80, the DSP, or the SoC that executes the abnormality determination process and the sheet detection process is an example of a processor that realizes the image processing method.

[0050] [Belt abnormality detection process] The image processing unit 8c executes the belt abnormality determination process when the conveying belt 320 is rotating in a non-conveying state in which the sheet 9 is not being conveyed to the conveying belt 320 by the sheet feeding mechanism 30 and the plurality of pairs of conveying rollers 31.

[0051] That is, the image processing unit 8c executes the belt abnormality determination process based on a plurality of line image data LD1 obtained by the line sensor 6 operating when the conveyor belt 320 is rotating in the non-conveying state.

[0052] An example of the procedure for the belt abnormality determination process will be described below with reference to the flowchart shown in FIG.

[0053] In the following description, S101, S102, ... represent identification codes of a plurality of steps in the belt abnormality determination process. In the belt abnormality determination process, the process of step S101 is executed first.

[0054] <Process S101> In step S101, the image processing unit 8c acquires line image data LD1 for one line obtained by the operation of the line sensor 6.

[0055] For example, a plurality of line image data LD1 obtained sequentially by the operation of the line sensor 6 is stored in the RAM 81, and the image processing unit 8c acquires one of the plurality of line image data LD1 stored in the RAM 81 in step S101.

[0056] After executing the process of step S101, the image processing unit 8c executes the process of step S102.

[0057] <Process S102> In step S102, the image processing unit 8c executes a peculiar data determination process to determine whether the line image data LD1 obtained in step S101 is peculiar data that satisfies a predetermined peculiar condition or not.

[0058] The peculiar condition is a condition that the line image data LD1 includes a plurality of peculiar pixel values ​​that are pixel values ​​that are out of an allowable range, and the number of the peculiar pixel values ​​included in the line image data LD1 exceeds a reference pixel number. The pixel values ​​are values ​​of the plurality of pixel data in the line image data LD1.

[0059] The allowable range is the range of variation of the pixel values ​​when there is no sheet 9 on the conveyor belt 320 and no scratches or stains exceeding the allowable limit exist on the surface of the conveyor belt 320 .

[0060] Fig. 6 is a diagram schematically showing a plurality of line image data LD1. In Fig. 6, a plurality of anomalous pixels G1 in the plurality of line image data LD1 are indicated by black dots. Each of the anomalous pixels G1 is a pixel having one of the plurality of anomalous pixel values. In Fig. 6, the horizontal direction is the main scanning direction corresponding to the second direction D2, and the vertical direction is the sub-scanning direction corresponding to the first direction D1.

[0061] In this embodiment, the image processing unit 8c sets the reference pixel number according to pre-obtained sheet size information. The sheet size information is information that indicates the size of the sheets 9 stored in the sheet storage unit 1. For example, the sheet size information is input in advance via the operation device 801 or the communication device 84.

[0062] For example, the image processing unit 8c derives the reference number of pixels by multiplying the number of pixels corresponding to the size of the sheet 9 in the second direction D2, which is indicated by the sheet size information, by a predetermined coefficient.

[0063] The image processing unit 8c determines that the line image data LD1 that satisfies the unique condition is the unique data, and determines that the line image data LD1 that does not satisfy the unique condition is non-unique data.

[0064] The image processing unit 8c executes the process of step S103 when it determines that the line image data LD1 is the non-unique data, and executes the process of step S105 when it determines that the line image data LD1 is the unique data.

[0065] The image processing unit 8c sets the number of consecutive lines LN1 and the maximum number of consecutive lines LN2 as variables related to the processing of the line image data LD1. The initial values ​​of the number of consecutive lines LN1 and the maximum number of consecutive lines LN2 are 0.

[0066] The number of consecutive lines LN1 is a variable that represents the number of consecutive peculiar data in the plurality of line image data LD1. The maximum number of consecutive lines LN2 is the maximum value of the number of consecutive lines LN1 for the plurality of line image data LD1 obtained during one rotation of the conveyor belt 320.

[0067] <Process S103> In step S103, the image processing unit 8c sets the maximum number of consecutive lines LN2 to the larger of the number of consecutive lines LN1 at the time step S103 is executed and the maximum number of consecutive lines LN2.

[0068] That is, when the number of consecutive lines LN1 is greater than the maximum number of consecutive lines LN2, the image processing unit 8c updates the maximum number of consecutive lines LN2 to the number of consecutive lines LN1, and otherwise maintains the maximum number of consecutive lines LN2.

[0069] After executing the process of step S103, the image processing unit 8c executes the process of step S104.

[0070] <Process S104> In step S104, the image processing unit 8c initializes the number of consecutive lines LN1 to 0. After executing the process of step S104, the image processing unit 8c executes the process of step S107.

[0071] <Process S105> In step S105, the image processing unit 8c counts up the number of consecutive lines LN1 by 1. After executing the process of step S105, the image processing unit 8c executes the process of step S106.

[0072] <Process S106> In step S106, the image processing unit 8c sets the maximum number of consecutive lines LN2 to the larger of the number of consecutive lines LN1 at the time step S106 is executed and the maximum number of consecutive lines LN2.

[0073] That is, when the number of consecutive lines LN1 is greater than the maximum number of consecutive lines LN2, the image processing unit 8c updates the maximum number of consecutive lines LN2 to the number of consecutive lines LN1, and otherwise maintains the maximum number of consecutive lines LN2.

[0074] After executing the process of step S106, the image processing unit 8c executes the process of step S107.

[0075] <Process S107> In step S107, the image processing unit 8c selects the next process depending on whether the conveyor belt 320 has completed one rotation by performing the processes of steps S101 to S106 on the multiple line image data LD1 obtained while the conveyor belt 320 makes at least one rotation.

[0076] In this embodiment, the detection of reflected light by the line sensor 6 and the output of line image data LD1 by the signal interface 83 are performed at regular intervals. In this case, the image processing unit 8c recognizes the state where the number of times the processes of steps S101 to S106 have been performed reaches a predetermined target number of times as the state where one rotation has been completed.

[0077] It should be noted that a rotary encoder (not shown) may be connected to the rotation shaft of one of the support rollers 321. In this case, the image processing unit 8c may recognize the state in which the number of output pulses from the rotary encoder reaches a target number as the state in which one rotation has been completed.

[0078] If the state of step S107 is not the one-rotation-completed state, the image processing unit 8c repeats the process from step S101. On the other hand, if the state of step S107 is the one-rotation-completed state, the image processing unit 8c executes the process of step S108.

[0079] <Process S108> In step S108, the image processing unit 8c executes a line number determination process to compare the maximum number of consecutive lines LN2 with each of a plurality of preset reference numbers N1 and N2. The image processing unit 8c selects the next process depending on the result of the line number determination process.

[0080] In this embodiment, the plurality of reference numbers N1, N2 includes a first reference number N1 and a second reference number N2 that is greater than the first reference number N1.

[0081] If the maximum number of consecutive lines LN2 is smaller than the first reference number N1, the image processing unit 8c determines that the conveyor belt 320 is normal, and ends the belt abnormality determination process.

[0082] The image processing unit 8c executes the process of step S109 when the maximum number of consecutive lines LN2 is within the range from the first reference number N1 to the second reference number N2. The image processing unit 8c executes the process of step S110 when the maximum number of consecutive lines LN2 exceeds the second reference number N2.

[0083] <Process S109> In step S109, the image processing unit 8c executes a first alarm output process to output first alarm information indicating that there is a high possibility that there is a slight scratch or stain on the conveyor belt 320. For example, the image processing unit 8c outputs the first alarm information through one or both of the display device 802 and the communication device 84.

[0084] After executing the process of step S109, the image processing unit 8c ends the belt abnormality determination process.

[0085] <Process S110> In step S110, the image processing unit 8c executes a second alarm output process to output second alarm information indicating that there is a high possibility that the conveyor belt 320 is severely damaged or dirty. For example, the image processing unit 8c outputs the second alarm information through one or both of the display device 802 and the communication device 84.

[0086] For example, the second alarm information includes information prompting inspection of the conveyor belt 320 and, if necessary, replacement of the conveyor belt 320. The second alarm information may include information indicating that conveyance of the sheet 9 is prohibited until inspection of the conveyor belt 320 or the like is performed.

[0087] After executing the process of step S110, the image processing unit 8c executes the process of step S111.

[0088] <Process S111> In step S111, the image processing unit 8c executes a process of prohibiting the sheet conveying device 3 including the first belt conveying device 32 from conveying the sheet 9.

[0089] For example, the image processing unit 8c sets a transport prohibition flag to ON to prohibit the sheet transport device 3 from transporting the sheet 9. When the transport prohibition flag is set to ON, the print control unit 8b does not allow the sheet transport device 3 to transport the sheet 9.

[0090] For example, the main control unit 8a sets the transport prohibition flag to OFF when a release command is input via the display device 802 or the communication device 84. The print control unit 8b continues to prohibit transport of the sheet 9 until the transport prohibition flag is set to OFF.

[0091] Note that setting the transport prohibition flag to ON and prohibiting the sheet transport device 3 from transporting the sheet 9 are examples of restricting the transport of the sheet 9 by the transport belt 320.

[0092] After executing the process of step S111, the image processing unit 8c ends the belt abnormality determination process.

[0093] As described above, the image processing unit 8c determines whether each of the plurality of line image data LD1 obtained in the non-conveying state is the peculiar data or not (see step S102).

[0094] Specifically, the image processing unit 8c determines whether each of the multiple line image data LD1 obtained while the conveying belt 320 rotates at least once in the non-conveying state is the peculiar data or not (see steps S102 and S107).

[0095] Furthermore, the image processing unit 8c determines the degree of abnormality of the conveyor belt 320 according to the number of consecutive anomalous data in the plurality of line image data LD1 obtained in the non-conveying state (see steps S108 to S110).

[0096] The second alarm output process is executed when a more serious abnormality of the conveyor belt 320 is detected than when the first alarm output process is executed.

[0097] The image processing unit 8c notifies the result of the determination of the abnormality level of the conveyor belt 320 via one or both of the display device 802 and the communication device 84 (see steps S109 and S110).

[0098] The first alarm output process and the second alarm output process are examples of processes for notifying the determination result of the abnormality level of the conveyor belt 320. The display device 802 and the communication device 84 are each an example of an information output device.

[0099] When the determination result of the abnormality degree of the conveyor belt 320 exceeds the upper limit, the image processing unit 8c restricts the conveyance of the sheet 9 by the conveyor belt 320 (see step S111).

[0100] In this embodiment, the second alarm output process is executed when the determination result of the abnormality level of the conveyor belt 320 exceeds the upper limit. The process of prohibiting the sheet conveying device 3 from conveying the sheet 9 is an example of a process of restricting the conveyance of the sheet 9 by the conveyor belt 320.

[0101] [Sheet detection process] The image processing unit 8c executes the sheet detection process when the conveyance belt 320 is rotating in a sheet conveying state in which the sheet 9 is conveyed to the conveyance belt 320 by the sheet feeding mechanism 30 and the plurality of pairs of conveyance rollers 31.

[0102] That is, the image processing unit 8c executes the sheet detection process based on a plurality of line image data LD1 obtained by the line sensor 6 operating when the conveyor belt 320 is rotating in the sheet conveying state.

[0103] An example of the procedure of the sheet detection process will be described below with reference to the flowchart shown in FIG.

[0104] In the following description, S201, S202, ... represent identification codes of a plurality of steps in the sheet detection process. In the sheet detection process, the process of step S201 is executed first.

[0105] <Process S201> In step S201, the image processing unit 8c acquires line image data LD1 for one line obtained by the operation of the line sensor 6, similarly to step S101 in FIG.

[0106] After executing the process of step S201, the image processing unit 8c executes the process of step S202.

[0107] <Process S202> In step S202, the image processing unit 8c executes the peculiar data determination process on the line image data LD1 obtained in step S201. The process in step S202 is the same as the process in step S102 in FIG.

[0108] The image processing unit 8c executes the process of step S203 when it determines that the line image data LD1 is the non-unique data, and executes the process of step S204 when it determines that the line image data LD1 is the unique data.

[0109] <Process S203> In step S203, the image processing unit 8c initializes the number of consecutive lines LN1 to 0. After executing the process of step S203, the image processing unit 8c repeats the processes from step S201. Note that in step S203, the image processing unit 8c determines that the sheet 9 has not yet reached the specific position P1.

[0110] <Process S204> In step S204, the image processing unit 8c counts up the number of consecutive lines LN1 by 1. After executing the process of step S204, the image processing unit 8c executes the process of step S205.

[0111] <Process S205> In step S205, the image processing unit 8c executes a line number comparison process to compare the number of consecutive lines LN1 with the reference consecutive number SN1, and selects the next process depending on the result of the line number comparison process.

[0112] The reference continuation number SN1 is a preset integer equal to or greater than 2. For example, the reference continuation number SN1 is the number of line image data LD1 corresponding to a length of approximately 5 to 10 millimeters in the first direction D1. The second reference number N2 used in the belt abnormality determination process is equal to or smaller than the reference continuation number SN1.

[0113] If the number of consecutive lines LN1 is smaller than the reference consecutive number SN1, the image processing unit 8c determines that the sheet 9 has not yet reached the specific position P1, and repeats the process from step S201.

[0114] On the other hand, if the number of consecutive lines LN1 is equal to or greater than the reference consecutive number SN1, the image processing unit 8c executes the process of step S206.

[0115] <Process S206> In step S206, the image processing unit 8c determines that the sheet 9 has reached the specific position P1, and sets the sheet detection flag to ON The initial state of the sheet detection flag is OFF.

[0116] The sheet detection flag being set to ON indicates that the arrival of the sheet 9 at the specific position P1 has been detected. The print control unit 8b controls the start timing of image formation by the printing device 4, starting from the point in time when the sheet detection flag is set to ON (see step S206a in FIG. 5).

[0117] After executing the process of step S206, the image processing unit 8c executes the process of step S207.

[0118] <Process S207> In step S207, the image processing unit 8c initializes parameters related to the sheet detection process.

[0119] Specifically, the image processing unit 8c initializes the number of consecutive lines LN1 to 0, and further initializes the sheet detection flag to OFF.

[0120] After executing the process of step S207, the image processing unit 8c repeats the process from step S201. Note that the image processing unit 8c ends the sheet detection process when the print process ends.

[0121] As described above, the image processing unit 8c determines whether each of the plurality of line image data LD1 obtained in the sheet conveying state is the peculiar data or not (see step S202).

[0122] Furthermore, the image processing unit 8c detects that the sheet 9 has reached the specific position P1 when the number of consecutive peculiar data in the plurality of line image data LD1 obtained in the sheet conveying state reaches a reference consecutive number SN1 (see steps S205 to S206).

[0123] Therefore, unless scratches or stains on the surface of the conveyor belt 320 are widespread, the sheet 9 can be detected separately from scratches or stains on the surface of the conveyor belt 320 .

[0124] Furthermore, if scratches or stains occur over a wide area on the surface of the conveyor belt 320, the conveyance of the sheet 9 by the conveyor belt 320 is restricted by the conveyor belt abnormality determination process (see step S111 in FIG. 4). This prevents the sheet 9 from being erroneously detected as being due to scratches or stains on the surface of the conveyor belt 320.

[0125] As described above, by employing the image forming apparatus 10, it is possible to distinguish between scratches or stains on the surface of the conveyor belt 320 and the sheet 9 on the conveyor belt 320 and detect them.

[0126] [Notes on the Invention] The following is a summary of the invention extracted from the above-described embodiment. Note that the configurations and processing functions described in the following supplementary notes can be selected and combined as desired.

[0127] <Appendix 1> An image processing method for processing a plurality of line image data sequentially obtained by a line sensor arranged along a second direction intersecting with a first direction at a specific position along a conveyor belt that can convey a sheet along the first direction by rotating, a processor determining whether each of the plurality of line image data is anomalous data that includes a plurality of anomalous pixel values ​​that are pixel values ​​outside an allowable range and the number of the plurality of anomalous pixel values ​​exceeds a reference pixel number, or whether the data is not anomalous data; and detecting, by the processor, that the sheet has reached the specific position when the number of consecutive peculiar data in the plurality of line image data reaches a reference consecutive number.

[0128] <Appendix 2> the processor determines whether each of the plurality of line image data obtained in a non-conveying state in which the sheet is not being conveyed to the conveying belt by a pre-stage conveying mechanism arranged upstream of the conveying belt in the sheet conveying direction, is the peculiar data; the processor determines the degree of abnormality of the conveyor belt according to the number of consecutive peculiar data in the plurality of line image data obtained in the non-conveying state; the processor determines whether each of the plurality of line image data obtained in a sheet conveying state in which the sheet is conveyed to the conveying belt by the front-stage conveying mechanism is the peculiar data or not; The image processing method described in Appendix 1 includes the processor detecting that the sheet has reached the specific position when the number of consecutive peculiar data in the multiple line image data obtained in the sheet transport state reaches the reference consecutive number.

[0129] <Appendix 3> The image processing method according to claim 2, further comprising the processor restricting the conveyance of the sheet by the conveyance belt when the determined result of the abnormality level of the conveyance belt exceeds an upper limit.

[0130] <Appendix 4> The image processing method according to claim 2 or 3, further comprising the processor notifying the result of the determination of the abnormality level of the conveyor belt through an information output device.

[0131] <Appendix 5> The image processing method described in any one of Supplementary Note 1 to Supplementary Note 4, including the processor controlling the start timing of image formation by a printing device that forms an image on the sheet transported by the transport belt depending on the time when it is detected that the sheet has reached the specific position.

[0132] <Appendix 6> An image processing method for processing a plurality of line image data sequentially obtained by a line sensor arranged along a second direction intersecting with a first direction at a specific position along a conveyor belt that can convey a sheet along the first direction by rotating, a processor determining whether each of the plurality of line image data is anomalous data that includes a plurality of anomalous pixel values ​​that are pixel values ​​outside an allowable range and the number of the plurality of anomalous pixel values ​​exceeds a reference pixel number, or whether the data is not anomalous data; and determining the degree of abnormality of the conveying belt according to the number of consecutive peculiar data in the plurality of line image data.

[0133] <Appendix 7> The image processing method described in Appendix 6, wherein the processor determines whether each of the multiple line image data obtained during at least one rotation of the conveying belt in a non-conveying state in which the sheet is not being conveyed to the conveying belt by a pre-stage conveying mechanism arranged upstream of the conveying belt in the sheet conveying direction is peculiar data or not.

[0134] <Appendix 8> a conveyor belt that can convey the sheet along a first direction by rotating; a line sensor disposed along a second direction intersecting the first direction at a specific position along the conveyor belt; a printing device for forming an image on the sheet conveyed by the conveyor belt; An image forming apparatus comprising: a processor that realizes the image processing method according to any one of Supplementary Note 1 to Supplementary Note 7. [Explanation of symbols]

[0135] 3: Sheet transport device 4: Printing device 6: Line sensor 8: Control device 10: Image forming device 32: First belt conveyor 33: Second belt conveyor 320: Conveyor belt

Claims

1. An image processing method for processing a plurality of line image data sequentially obtained by a line sensor disposed along a second direction intersecting with a first direction at a specific position along a conveyor belt that can convey a sheet along the first direction by rotating, a processor determining whether each of the plurality of line image data is anomalous data that includes a plurality of anomalous pixel values ​​that are pixel values ​​outside an allowable range and the number of the plurality of anomalous pixel values ​​exceeds a reference pixel number, or whether the data is not anomalous data; and detecting, by the processor, that the sheet has reached the specific position when the number of consecutive peculiar data in the plurality of line image data reaches a reference consecutive number.

2. the processor determines whether each of the plurality of line image data obtained in a non-conveying state in which the sheet is not being conveyed to the conveying belt by a pre-stage conveying mechanism arranged upstream of the conveying belt in the sheet conveying direction, is the peculiar data; the processor determines the degree of abnormality of the conveyor belt according to the number of consecutive peculiar data in the plurality of line image data obtained in the non-conveying state; the processor determines whether each of the plurality of line image data obtained in a sheet conveying state in which the sheet is conveyed to the conveying belt by the front-stage conveying mechanism is the peculiar data or not; The image processing method of claim 1, further comprising: detecting that the sheet has reached the specific position when the number of consecutive peculiar data in the plurality of line image data obtained in the sheet transport state reaches the reference consecutive number.

3. The image processing method according to claim 2 , further comprising the processor restricting the conveyance of the sheet by the conveyance belt when the determined result of the abnormality degree of the conveyance belt exceeds an upper limit.

4. 4. The image processing method according to claim 2, further comprising the processor notifying the result of the determination of the abnormality level of the conveyor belt via an information output device.

5. 3. The image processing method according to claim 1, further comprising: controlling the timing of starting image formation by a printing device that forms an image on the sheet transported by the transport belt, depending on the time when the arrival of the sheet at the specific position is detected.

6. An image processing method for processing a plurality of line image data sequentially obtained by a line sensor disposed along a second direction intersecting with a first direction at a specific position along a conveyor belt that can convey a sheet along the first direction by rotating, a processor determining whether each of the plurality of line image data is anomalous data that includes a plurality of anomalous pixel values ​​that are pixel values ​​outside an allowable range and the number of the plurality of anomalous pixel values ​​exceeds a reference pixel number, or whether the data is not anomalous data; and determining the degree of abnormality of the conveying belt according to the number of consecutive peculiar data in the plurality of line image data.

7. The image processing method described in claim 6, wherein the processor determines whether each of the plurality of line image data obtained during at least one rotation of the conveying belt in a non-conveying state in which the sheet is not being conveyed to the conveying belt by a pre-stage conveying mechanism arranged upstream of the conveying belt in the sheet conveying direction is peculiar data or not.

8. a conveyor belt that can convey a sheet along a first direction by rotating; a line sensor disposed along a second direction intersecting the first direction at a specific position along the conveyor belt; a printing device for forming an image on the sheet conveyed by the conveyor belt; An image forming apparatus comprising: a processor that implements the image processing method according to any one of claims 1 to 3, 6 and 7.

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