Image forming apparatus and detection method

Abstract

To provide an image forming apparatus capable of detecting an inclination of an imaging portion, and a detection method.SOLUTION: An image forming apparatus includes an image forming unit 3 that forms an image on a sheet conveyed along a predetermined conveyance path, and a line sensor 51 that is provided on an upstream side of an image forming unit 3 in a conveyance direction D11 of the sheet in the conveyance path so as to be long along a widthwise direction D12 and captures an image of the sheet. The image forming apparatus detects an inclination angle θ 3 of the line sensor 51 with respect to the widthwise direction D12 based on shape data indicating a shape of a specific sheet acquired using the line sensor 51.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus and a detection method. [Background technology]

[0002] There is known an image forming apparatus that includes an imaging unit such as a line sensor that captures an image of a sheet being conveyed through an image forming position by an image forming unit. Also, there is known a related art image forming apparatus that can detect the inclination of the imaging unit with respect to the width direction based on the imaging result of a mark image that is elongated in the width direction perpendicular to the conveying direction of the sheet and is formed on a conveying belt used to convey the sheet (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-25697 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the image forming apparatus according to the related art, when the axis of the tension roller that stretches the conveyor belt is inclined with respect to the width direction, the mark image is inclined with respect to the width direction, and therefore, in the image forming apparatus according to the related art, when the axis of the tension roller is inclined with respect to the width direction, the inclination of the imaging unit cannot be detected.

[0005] An object of the present invention is to provide an image forming apparatus and a detection method that can detect the tilt of an imaging unit. [Means for solving the problem]

[0006] According to one aspect of the present invention, an image forming apparatus includes an image forming unit, an imaging unit, a conveying processing unit, an acquisition processing unit, a first detection processing unit, a mask processing unit, a second detection processing unit, and a third detection processing unit. The image forming unit forms an image on a sheet conveyed along a predetermined conveying path. The imaging unit is disposed upstream of the image forming unit in the conveying direction of the sheet and elongated along a width direction perpendicular to the conveying direction, and captures an image of the sheet. The conveying processing unit conveys a predetermined specific sheet along the conveying path. The acquisition processing unit uses the imaging unit to acquire shape data indicating the shape of the specific sheet conveyed by the conveying processing unit. The first detection processing unit detects a first amount of inclination of an end of a sheet area in a second direction corresponding to the width direction, the end being included in the shape data acquired by the acquisition processing unit, with respect to a first direction corresponding to the conveying direction. The mask processing unit uses the shape data acquired by the acquisition processing unit to mask an overhanging area of specific image data that is larger in size in the first direction than the sheet area and that extends beyond the sheet area. The second detection processing unit detects a second tilt amount with respect to the second direction of a boundary between a masked area and an unmasked area that face each other along the first direction in the specific image data in which the protruding area is masked by the mask processing unit. The third detection processing unit detects a third tilt amount with respect to the width direction of the imaging unit based on the first tilt amount detected by the first detection processing unit and the second tilt amount detected by the second detection processing unit.

[0007] A detection method according to another aspect of the present invention is performed by an image forming apparatus including an image forming unit that forms an image on a sheet transported along a predetermined transport path, and an imaging unit that is disposed on the transport path upstream of the image forming unit in the sheet transport direction and extends longitudinally along a width direction perpendicular to the transport direction, and that images the sheet. The detection method includes a transport step, an acquisition step, a first detection step, a masking step, a second detection step, and a third detection step. In the transport step, a predetermined specific sheet is transported along the transport path. In the acquisition step, shape data indicating the shape of the specific sheet transported in the transport step is acquired using the imaging unit. In the first detection step, a first amount of inclination of an end of a sheet area included in the shape data acquired in the acquisition step, the end in a second direction corresponding to the width direction, with respect to a first direction corresponding to the transport direction, is detected. In the masking step, the shape data acquired in the acquisition step is used to mask an area of specific image data that is larger in size in the first direction than the sheet area and that extends beyond the sheet area. In the second detecting step, a second tilt amount with respect to the second direction of a boundary between a masked area and an unmasked area that face each other along the first direction in the specific image data in which the protruding area has been masked in the masking step is detected. In the third detecting step, a third tilt amount with respect to the width direction of the imaging unit is detected based on the first tilt amount detected in the first detecting step and the second tilt amount detected in the second detecting step. [Effects of the Invention]

[0008] According to the present invention, the tilt of the imaging unit can be detected. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view showing the configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 2]FIG. 2 is a plan view showing the configuration of the image forming section, the transport unit, and the line sensor in the image forming apparatus according to the embodiment of the present invention. [Figure 3] FIG. 3 is a block diagram showing the system configuration of the image forming apparatus according to the embodiment of the present invention. [Figure 4] FIG. 4 is a flowchart showing an example of tilt amount detection processing executed in the image forming apparatus according to the embodiment of the present invention. [Figure 5] FIG. 5 is a diagram showing an example of shape data acquired by the image forming apparatus according to the embodiment of the present invention. [Figure 6] FIG. 6 is a diagram showing an example of shape data acquired by the image forming apparatus according to the embodiment of the present invention. [Figure 7] FIG. 7 is a diagram showing an example of specific image data to be masked in the image forming apparatus according to the embodiment of the present invention. [Figure 8] FIG. 8 is a diagram showing an example of specific image data masked by the image forming apparatus according to the embodiment of the present invention. [Figure 9] FIG. 9 is a block diagram showing the system configuration of an image forming apparatus according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Note that the following embodiment is an example of a specific embodiment of the present invention and does not limit the technical scope of the present invention.

[0011] [Configuration of image forming apparatus 100] First, the configuration of an image forming apparatus 100 according to an embodiment of the present invention will be described with reference to Figures 1 to 3. In Figure 1, a sheet transport path R11 is indicated by a two-dot chain line.

[0012] Image forming apparatus 100 is a printer capable of forming an image on a sheet using an inkjet method. The present invention may also be applied to a fax machine, a copier, or a multifunction peripheral capable of forming an image on a sheet using an inkjet method. The present invention may also be applied to an image forming apparatus capable of forming an image on a sheet using a method other than the inkjet method, such as an electrophotographic method.

[0013] 1, the image forming apparatus 100 includes a housing 1, a sheet conveying section 2, an image forming section 3, a conveying unit 4, and a shape reading section 5. The image forming apparatus 100 also includes an operation display section 6, a control section 7, and an image processing section 8 shown in FIG.

[0014] The housing 1 houses each component of the image forming apparatus 100. A paper feed cassette 11 (see FIG. 1) is removably provided in the housing 1. The paper feed cassette 11 stores sheets on which images are to be formed. A paper output tray 12 (see FIG. 1) is provided on the outer surface of the housing 1. Sheets on which images are formed by the image forming unit 3 are discharged to the paper output tray 12. Inside the housing 1, the sheets stored in the paper feed cassette 11 are transported along a sheet transport path R11 (see FIG. 1) that passes through an image formation position by the image forming unit 3 and reaches the paper output tray 12.

[0015] The sheet transport unit 2 transports sheets stored in the paper feed cassette 11 along a sheet transport path R11 (see FIG. 1). As shown in FIG. 1, the sheet transport unit 2 includes a pickup roller 21 and multiple transport rollers 22. The pickup roller 21 picks up the top sheet of the stack of sheets stored in the paper feed cassette 11 and sends the sheet to the sheet transport path R11. The multiple transport rollers 22 are arranged side by side along the sheet transport path R11. Each transport roller 22 transports the sheet along the sheet transport path R11. Each transport roller 22 transports the sheet in a transport direction D11 (see FIG. 1) from the paper feed cassette 11 to the paper output tray 12.

[0016] The image forming unit 3 forms an image on a sheet transported along a sheet transport path R11 (see FIG. 1) (one example of a transport path of the present invention). As shown in FIG. 1, the image forming unit 3 includes line heads 31 to 34 and a head frame 35.

[0017] 2, each of the line heads 31 to 34 is elongated in a width direction D12 perpendicular to the conveying direction D11. Specifically, each of the line heads 31 to 34 has a length in the width direction D12 corresponding to the width of the largest size sheet that can be accommodated in the paper feed cassette 11. The line heads 31 to 34 are arranged side by side at equal intervals along the conveying direction D11.

[0018] As shown in FIG. 2, each of the line heads 31 to 34 has a plurality of recording heads 30. Each of the recording heads 30 ejects ink toward a sheet transported by the transport unit 4. Each of the recording heads 30 provided in the line head 31 ejects black ink. Each of the recording heads 30 provided in the line head 32 ejects cyan ink. Each of the recording heads 30 provided in the line head 33 ejects magenta ink. Each of the recording heads 30 provided in the line head 34 ejects yellow ink.

[0019] Each of the recording heads 30 includes a plurality of nozzles 30A (see FIG. 2) that eject ink. The plurality of nozzles 30A are provided on the surface of the recording head 30 that faces the sheet transported by the transport unit 4.

[0020] Each recording head 30 also includes a pressure chamber (not shown), a piezoelectric element (not shown), and an individual flow path (not shown) corresponding to each nozzle 30A. The pressure chamber communicates with the nozzle 30A and stores ink. The piezoelectric element ejects ink from the nozzle 30A in response to application of a predetermined drive voltage. The individual flow path is an ink flow path provided between the pressure chamber and a common flow path (not shown) shared by the multiple nozzles 30A. A plurality of the individual flow paths corresponding to the multiple nozzles 30A are connected to the common flow path. The common flow path is connected to an ink supply unit (not shown) that supplies ink to each of the pressure chambers.

[0021] 2, the line head 31 includes three recording heads 30 arranged in a staggered pattern along the width direction D12. Similarly to the line head 31, each of the other line heads 32 to 34 also includes three recording heads 30 arranged in a staggered pattern along the width direction D12.

[0022] The head frame 35 supports the line heads 31 to 34. The head frame 35 is supported by the housing 1. The number of line heads provided in the image forming unit 3 does not have to be four. Also, the number of recording heads 30 provided in each of the line heads 31 to 34 does not have to be three.

[0023] The image forming unit 3 forms an image on a sheet based on image data input from the image processing unit 8. Specifically, the image forming unit 3 controls the ejection of ink from each of the line heads 31 to 34 based on the image data input from the image processing unit 8.

[0024] As shown in FIG. 1, the transport unit 4 is disposed below the line heads 31 to 34. The transport unit 4 transports a sheet while facing the recording head 30. For example, the transport unit 4 transports the sheet by a predetermined transport distance each time the recording head 30 ejects ink. The transport unit 4 also stops transporting the sheet while the recording head 30 is ejecting ink. As shown in FIG. 1, the transport unit 4 includes a transport belt 41 on which the sheet is placed, a first tension roller 42, a second tension roller 43, and a third tension roller 44 that tension the transport belt 41, and a transport frame 45 that supports these. The gap between the transport belt 41 and the recording head 30 is adjusted so that the gap between the surface of the sheet and the recording head 30 during image formation is a predetermined distance (for example, 1 mm).

[0025] The first tension roller 42 is rotationally driven by a rotational driving force supplied from a motor (not shown). As a result, the conveyor belt 41 rotates in a direction that allows the sheet to be conveyed in the conveying direction D11 (see FIG. 1). The conveying unit 4 is also provided with a suction unit (not shown) that sucks air through a number of through holes formed in the conveyor belt 41 to attract the sheet to the conveyor belt 41.

[0026] The shape reading unit 5 reads the shape of the sheet being conveyed along the sheet conveying path R11.

[0027] As shown in FIG. 3, the shape reading unit 5 includes a line sensor 51 and an AFE (analog front end) circuit 52.

[0028] As shown in FIG. 1, the line sensor 51 is provided on the sheet transport path R11 upstream of the image forming unit 3 in the sheet transport direction D11. The line sensor 51 is also provided above the transport belt 41. As shown in FIG. 2, the line sensor 51 is provided elongated along the width direction D12 perpendicular to the transport direction D11. The line sensor 51 captures an image of the sheet transported along the sheet transport path R11. The line sensor 51 is an example of an imaging unit of the present invention.

[0029] For example, the line sensor 51 is a CIS (contact image sensor). The line sensor 51 includes multiple imaging elements arranged side by side in the width direction D12 (see FIG. 2). Each of the imaging elements includes a light-emitting unit and a light-receiving unit. The light-emitting unit emits light toward the conveyor belt 41. The light-receiving unit is configured to receive light emitted from the light-emitting unit and reflected by the conveyor belt 41 or the conveyed sheet, and outputs an analog electrical signal corresponding to the amount of received light. The line sensor 51 captures an image of the sheet conveyed along the sheet conveyance path R11 at a predetermined imaging cycle. Specifically, the line sensor 51 outputs an analog electrical signal corresponding to an image of the object (sheet and conveyor belt 41) facing the line sensor 51 at the imaging cycle. The outer circumferential surface of the conveyor belt 41 is colored, such as black, to suppress reflection of light emitted from the light-emitting unit compared to the background color (white) of the sheet.

[0030] The AFE circuit 52 is an electronic circuit that performs predetermined processing on the analog electrical signal output from the line sensor 51. Specifically, the AFE circuit 52 includes a signal conversion unit that converts the analog electrical signal output from the line sensor 51 into a digital electrical signal (image data). The AFE circuit 52 also includes a binarization unit that performs binarization processing on the image data output from the signal conversion unit. The binarization processing is a process of binarizing each pixel included in the image data output from the signal conversion unit into a value that indicates the presence or absence of a sheet. The image data binarized by the binarization unit (hereinafter referred to as "line data") is input to the image processing unit 8.

[0031] The operation display unit 6 is a user interface of the image forming apparatus 100. The operation display unit 6 includes a display unit and an operation unit. The display unit displays various information in response to control instructions from the control unit 7. For example, the display unit is a flat panel display such as a liquid crystal display. The operation unit inputs various information to the control unit 7 in response to user operations. For example, the operation unit includes operation keys and a touch panel.

[0032] The control unit 7 performs overall control of the image forming apparatus 100. As shown in FIG. 3, the control unit 7 includes a CPU 61, a ROM 62, and a RAM 63. The CPU 61 is a processor that executes various types of arithmetic processing. The ROM 62 is a non-volatile storage device that stores in advance information such as control programs for causing the CPU 61 to execute various types of processing. The RAM 63 is a volatile or non-volatile storage device that is used as a temporary storage memory (work area) for the various types of processing executed by the CPU 61. The CPU 61 performs overall control of the image forming apparatus 100 by executing the various control programs that are stored in advance in the ROM 62.

[0033] The image processing unit 8 adjusts the image data input to the image forming unit 3, i.e., the image data used to form an image on a sheet, based on the image data input from the shape reading unit 5. For example, the image processing unit 8 masks, based on the image data input from the shape reading unit 5, a portion of the image data input to the image forming unit 3 that is used to form an image on the outside of the sheet transported along the sheet transport path R11. This prevents ink from being ejected onto the outside of the sheet. The image processing unit 8 is composed of electronic circuits such as integrated circuits (ASIC, DSP).

[0034] Incidentally, an image forming device capable of detecting the inclination of a line sensor 51 relative to the width direction D12 based on the imaging results of a mark image formed on a conveying belt 41 that is long in the width direction D12 by the line sensor 51 is known as related technology.

[0035] However, in the image forming apparatus according to the related art described above, when the axis of the tension roller that stretches the conveyor belt 41 is inclined with respect to the width direction D12, the mark image is inclined with respect to the width direction D12. Therefore, in the image forming apparatus according to the related art described above, when the axis of the tension roller is inclined with respect to the width direction D12, the inclination of the line sensor 51 cannot be detected.

[0036] In contrast to this, the image forming apparatus 100 according to the embodiment of the present invention is capable of detecting the inclination of the line sensor 51, as will be described below.

[0037] 3, the control unit 7 includes a transport processing unit 64 and an output processing unit 65. Specifically, the CPU 61 of the control unit 7 executes the control program stored in the ROM 62 to function as the transport processing unit 64 and the output processing unit 65. Note that the transport processing unit 64 and the output processing unit 65 may be realized by electronic circuits.

[0038] 3, the image processing unit 8 includes an acquisition processing unit 71, a first detection processing unit 72, a mask processing unit 73, a second detection processing unit 74, and a third detection processing unit 75. The CPU 61 of the control unit 7 may function as each of the above-mentioned processing units by executing the control program stored in the ROM 62.

[0039] The conveying processing unit 64 executes a conveying process for conveying a predetermined specific sheet along the sheet conveying path R11. Here, the specific sheet is a sheet of a predetermined size.

[0040] For example, the conveyance processing unit 64 displays a guide screen on the operation display unit 6 in response to a predetermined user operation on the operation display unit 6. The guide screen includes a message urging the user to place the specific sheet in the paper feed cassette 11. The guide screen also includes an execution key used to perform the conveyance processing.

[0041] Then, when the user operates the execution key, the conveying processing unit 64 executes the conveying process. In the conveying process, the sheet conveying unit 2 and the conveying unit 4 are used to convey the specific sheet along the sheet conveying path R11.

[0042] The acquisition processing unit 71 uses the line sensor 51 to acquire shape data X10 (see FIG. 5) that indicates the shape of the specific sheet conveyed by the conveyance processing unit 64.

[0043] For example, when the leading edge of the specific sheet is detected by a sheet sensor (not shown) located upstream of the line sensor 51 in the sheet conveying path R11 (see FIG. 1) in the conveying direction D11, the acquisition processing unit 71 starts reading the shape of the specific sheet by the shape reading unit 5. This causes the shape reading unit 5 to output the line data at the imaging period. Furthermore, the acquisition processing unit 71 ends reading the shape of the specific sheet by the shape reading unit 5 when a predetermined time has elapsed since the trailing edge of the specific sheet was detected by the sheet sensor. The specific time is set so that reading the shape of the specific sheet by the shape reading unit 5 ends after the trailing edge of the specific sheet passes a position facing the line sensor 51. The acquisition processing unit 71 then acquires each of the line data output from the shape reading unit 5 during the period in which the shape reading unit 5 reads the shape of the specific sheet. In other words, the shape data X10 is data composed of the multiple line data output from the shape reading unit 5 during the period in which the shape reading unit 5 reads the shape of the specific sheet.

[0044] FIG. 5 shows an example of shape data X10. The shape data X10 shown in FIG. 5 is shape data X10 acquired by the acquisition processing unit 71 when the specific sheet is inclined with respect to the conveying direction D11 (see FIG. 2) and the line sensor 51 is inclined with respect to the width direction D12 as shown in FIG. 2. The shape data X10 includes a sheet area X11 indicating the specific sheet. The sheet area X11 is an area formed by pixels indicating the presence of a sheet. The outside of the sheet area X11 in the shape data X10 is formed by pixels indicating the absence of a sheet. Note that the first direction D13 shown in FIG. 5 is the direction corresponding to the conveying direction D11. Furthermore, the second direction D14 shown in FIG. 5 is the direction corresponding to the width direction D12.

[0045] The first detection processing unit 72 detects a first tilt angle θ1 (see FIG. 5) with respect to the first direction D13 corresponding to the conveying direction D11 of an end portion in the second direction D14 corresponding to the width direction D12 in the sheet area X11 included in the shape data X10 acquired by the acquisition processing unit 71. The first tilt angle θ1 is an example of a first tilt amount of the present invention. Note that the first tilt amount of the present invention is not limited to an angle.

[0046] For example, each time the acquisition processing unit 71 acquires the line data, the first detection processing unit 72 determines whether the acquired line data includes a pixel indicating the presence of a sheet. The first detection processing unit 72 measures the elapsed time from time T0 (see FIG. 5) when it is first determined that the line data includes a pixel indicating the presence of a sheet. The first detection processing unit 72 acquires a distance L1 (see FIG. 5) (number of pixels) from an end of the line data on the fifth direction D23 (see FIG. 5) side along the second direction D14 to an end of the sheet area X11 on the fifth direction D23 side, the distance L1 being obtained at time T1 (see FIG. 5) when the elapsed time from time T0 reaches a predetermined first time. The first detection processing unit 72 acquires a distance L2 (see FIG. 5) (number of pixels) from an end of the line data on the fifth direction D23 side to an end of the sheet area X11 on the fifth direction D23 side, the distance L2 being obtained at time T2 (see FIG. 5) when the elapsed time from time T0 reaches a second time longer than the first time. Then, the first detection processing unit 72 calculates the first tilt angle θ1 based on the difference between the distance L2 and the distance L1 and the distance (number of pixels) corresponding to the time from the timing T1 to the timing T2.

[0047] Here, FIG. 6 shows another example of the shape data X10. The shape data X10 shown in FIG. 6 is the shape data X10 acquired by the acquisition processing unit 71 when the specific sheet is not tilted with respect to the conveying direction D11 and the line sensor 51 is tilted with respect to the width direction D12 as shown in FIG. 2. When the specific sheet is not tilted with respect to the conveying direction D11, the distance L1 and the distance L2 are equal. Therefore, the first tilt angle θ1 detected by the first detection processing unit 72 is zero. In other words, the first tilt angle θ1 detected by the first detection processing unit 72 does not reflect the third tilt angle θ3 (see FIG. 2) of the line sensor 51 with respect to the width direction D12, but only reflects the tilt angle of the specific sheet with respect to the conveying direction D11.

[0048] The mask processing unit 73 uses the shape data X10 acquired by the acquisition processing unit 71 to perform masking processing to mask the protruding area of specific image data Y10 (see Figure 7) that is larger in size in the first direction D13 than the sheet area X11 and that protrudes beyond the sheet area X11.

[0049] For example, the specified image data Y10 is data of the same size as the shape data X10.

[0050] Then, the mask processing unit 73 determines, as the protruding area, the outside of the area in the specified image data Y10 that overlaps with the sheet area X11 when the shape data X10 is superimposed on the specified image data Y10 without misalignment.

[0051] For example, if a pixel in the protruding area in the specified image data Y10 is a pixel of a color other than white, the mask processing unit 73 replaces the pixel with a white pixel to mask the protruding area.

[0052] For example, the mask processing unit 73 performs the masking process on a plurality of pixel rows along the second direction D14 included in the specified image data Y10, in order along the first direction D13, starting from the pixel row that is most downstream in the first direction D13. Specifically, each time the acquisition processing unit 71 acquires the line data, the mask processing unit 73 determines the protruding area included in the pixel row based on the acquired line data, and masks the determined protruding area.

[0053] FIG. 7 shows an example of the specific image data Y10. Note that in FIG. 7, the area of the specific image data Y10 that overlaps with the sheet area X11 is indicated by a two-dot chain line. The specific image data Y10 has a colored area Y11. The colored area Y11 is positioned in the specific image data Y10 so as to overlap with the end of the sheet area X11 in the third direction D21 (an example of the specific direction of the present invention) along the first direction D13, based on the distance between the sheet sensor and the line sensor 51 in the sheet transport path R11 (see FIG. 1) and the sheet transport speed. The colored area Y11 is formed in a long strip shape in the second direction D14. The colored area Y11 is also positioned in the center of the specific image data Y10 in the second direction D14. For example, the colored area Y11 is a black-colored area. The area outside the colored area Y11 in the specific image data Y10 is a colorless area. In other words, the area outside the colored area Y11 in the specific image data Y10 is formed by white pixels. The colored area Y11 may be positioned so as to overlap the end of the specific image data Y10 in the fourth direction D22 (another example of the specific direction of the present invention), which is opposite to the third direction D21, of the sheet area X11. The colored area Y11 may also occupy the entire specific image data Y10. The color of the colored area Y11 is not limited to black, and may be any color other than white.

[0054] 8 shows an example of specific image data Y10 in which the protruding area has been masked by the mask processing unit 73. In FIG. 8, a masked mask area Y12 of the colored area Y11 is shown by a dotted line. In FIG. 8, an unmasked non-masked area Y13 of the colored area Y11 is shown by a solid line.

[0055] The specified image data Y10 may be data of a different size from the shape data X10. In this case, the mask processing unit 73 determines the protruding area to be the area outside the area in the specified image data Y10 that overlaps with the sheet area X11 when the shape data X10 is superimposed on the specified image data Y10 so that the first reference position in the specified image data Y10 coincides with the second reference position in the shape data X10. For example, the first reference position is a position in the specified image data Y10 that is the center in the first direction D13 and the center in the second direction D14. The second reference position is a position in the shape data X10 that is the center in the first direction D13 and the center in the second direction D14.

[0056] The second detection processing unit 74 detects a second tilt angle θ2 (see FIG. 8) of a boundary Y14 (see FIG. 8) between a masked area Y12 (see FIG. 8) and an unmasked area Y13 (see FIG. 8) that face each other along the first direction D13 in the specified image data Y10 (see FIG. 8) in which the protruding area has been masked by the mask processing unit 73, with respect to the second direction D14. The second tilt angle θ2 is an example of a second tilt amount of the present invention. Note that the second tilt amount of the present invention does not need to be limited to an angle.

[0057] For example, each time the mask processing unit 73 masks the protruding region included in the pixel row, the second detection processing unit 74 determines whether the masked pixel row includes pixels that constitute the colored region Y11. When the second detection processing unit 74 first determines that the masked pixel row includes pixels that constitute the colored region Y11, it acquires the length L3 (see FIG. 8) (number of pixels) of the colored region Y11 included in the pixel row. Each time the mask processing unit 73 masks the protruding region included in the pixel row, from the time the second detection processing unit 74 first determines that the masked pixel row includes pixels that constitute the colored region Y11, it counts the number of pixels that constitute the colored region Y11 included in the masked pixel row. When the second detection processing unit 74 determines that the number of pixels that constitute the colored region Y11 included in the masked pixel row exceeds a predetermined threshold that is less than the number of pixels corresponding to the size of the colored region Y11 along the second direction D14, it acquires the length L4 (see FIG. 8) (number of pixels) of the colored region Y11 included in the pixel row. Then, the second detection processing unit 74 calculates the second tilt angle θ2 based on the difference between the length L4 and the length L3 and the distance (number of pixels) corresponding to the time from when the length L3 was acquired to when the length L4 was acquired.

[0058] The second detection processing unit 74 also determines whether the second tilt angle θ2 is positive or negative based on the shape of the non-mask region Y13. For example, as shown in FIG. 8, when the non-mask region Y13 has a shape with a notch on the side of a fifth direction D23 (see FIG. 8) along the second direction D14, the second detection processing unit 74 determines that the second tilt angle θ2 is positive. When the non-mask region Y13 has a shape with a notch on the side of a sixth direction D24 (see FIG. 8) opposite to the fifth direction D23, the second detection processing unit 74 determines that the second tilt angle θ2 is negative. For example, the second detection processing unit 74 determines the shape of the non-mask region Y13 based on whether the portion of the pixel row used to acquire the length L3 that constitutes the colored region Y11 is located on the fifth direction D23 or the sixth direction D24.

[0059] The third detection processing unit 75 detects a third tilt angle θ3 (see FIG. 2) of the line sensor 51 with respect to the width direction D12 based on the first tilt angle θ1 detected by the first detection processing unit 72 and the second tilt angle θ2 detected by the second detection processing unit 74. The third tilt angle θ3 is an example of a third tilt amount of the present invention. Note that the third tilt amount of the present invention does not have to be limited to an angle.

[0060] Here, the first tilt angle θ1 is a value that reflects the tilt angle of the specific sheet with respect to the conveying direction D11. The second tilt angle θ2 is a value that reflects both the tilt angle of the specific sheet with respect to the conveying direction D11 and the third tilt angle θ3. In other words, the third tilt angle θ3 can be obtained by removing the influence of the tilt angle of the specific sheet with respect to the conveying direction D11 from the second tilt angle θ2.

[0061] For example, the third detection processing unit 75 calculates the third tilt angle θ3 by subtracting the first tilt angle θ1 from the second tilt angle θ2.

[0062] The output processing unit 65 outputs the third tilt angle θ3 detected by the third detection processing unit 75.

[0063] For example, the output processing unit 65 causes the operation display unit 6 to display the third tilt angle θ3 detected by the third detection processing unit 75.

[0064] [Tilt detection process] 4, the detection method of the present invention will be described along with an example of the procedure of the tilt amount detection process executed by the control unit 7 and image processing unit 8 in the image forming apparatus 100. Here, steps S11, S12, etc. represent the numbers of the processing procedures (steps) executed by the control unit 7 or the image processing unit 8. The tilt amount detection process is executed when the user's operation on the execution key on the guidance screen is accepted.

[0065] <Step S11> First, in step S11, the control unit 7 executes the conveying process of conveying the specific sheet along the sheet conveying path R11. The process of step S11 is an example of a conveying step of the present invention, and is executed by the conveying process unit 64 of the control unit 7.

[0066] <Step S12> In step S12, the image processing unit 8 acquires shape data X10 (see FIG. 5) indicating the shape of the specific sheet conveyed in the conveying process, using the line sensor 51. The process of step S12 is an example of an acquisition step of the present invention, and is executed by the acquisition processing unit 71 of the image processing unit 8.

[0067] Specifically, when the leading edge of the specific sheet is detected by the sheet sensor, the image processing unit 8 causes the shape reading unit 5 to start reading the shape of the specific sheet. Furthermore, when the specific time has elapsed since the rear edge of the specific sheet was detected by the sheet sensor, the image processing unit 8 causes the shape reading unit 5 to end reading the shape of the specific sheet. Then, the image processing unit 8 acquires each of the line data output from the shape reading unit 5 during the period when the shape reading unit 5 is reading the shape of the specific sheet.

[0068] <Step S13> In step S13, the image processing unit 8 detects a first tilt angle θ1 (see FIG. 5) of an end portion of the seat area X11 in the second direction D14 with respect to the first direction D13, the end portion being included in the shape data X10 acquired in the processing of step S12. The processing of step S13 is an example of a first detection step of the present invention, and is executed by the first detection processing unit 72 of the image processing unit 8.

[0069] Specifically, each time the line data is acquired in the process of step S12, the image processing unit 8 determines whether the acquired line data includes a pixel indicating the presence of a sheet. The image processing unit 8 also measures the elapsed time from timing T0 (see FIG. 5) when it is first determined that the line data includes a pixel indicating the presence of a sheet. The image processing unit 8 also acquires a distance L1 (see FIG. 5) (number of pixels) from the end of the line data on the fifth direction D23 (see FIG. 5) side to the end of the sheet area X11 on the fifth direction D23 side, which is acquired at timing T1 (see FIG. 5) when the elapsed time from timing T0 reaches the first time. The image processing unit 8 also acquires a distance L2 (see FIG. 5) (number of pixels) from the end of the line data on the fifth direction D23 side to the end of the sheet area X11 on the fifth direction D23 side, which is acquired at timing T2 (see FIG. 5) when the elapsed time from timing T0 reaches the second time. Then, the image processing unit 8 calculates the first tilt angle θ1 based on the difference between the distance L2 and the distance L1 and the distance (number of pixels) corresponding to the time from the timing T1 to the timing T2.

[0070] <Step S14> In step S14, the image processing unit 8 performs the masking process to mask the protruding area of the specific image data Y10 (see FIG. 7) that protrudes from the sheet area X11, using the shape data X10 acquired in the process of step S12. The process of step S14 is an example of a masking step of the present invention, and is performed by the mask processing unit 73 of the image processing unit 8.

[0071] Specifically, the image processing unit 8 performs the masking process on the plurality of pixel rows along the second direction D14 included in the specified image data Y10, in order along the first direction D13, starting from the pixel row that is furthest downstream in the first direction D13. More specifically, each time the line data is acquired in the process of step S12, the image processing unit 8 determines the protruding area included in the pixel row based on the acquired line data, and masks the determined protruding area.

[0072] The specific image data Y10, whose protruding area has been masked in the process of step S14, is input to the image forming unit 3. In response to the input of the specific image data Y10, the image forming unit 3 forms an image based on the specific image data Y10 on the specific sheet.

[0073] <Step S15> In step S15, the image processing unit 8 detects a second tilt angle θ2 (see FIG. 8) with respect to the second direction D14 of a boundary Y14 (see FIG. 8) between a masked area Y12 (see FIG. 8) and a non-masked area Y13 (see FIG. 8) that face each other along the first direction D13 in the specified image data Y10 (see FIG. 8) in which the protruding area has been masked in the processing of step S14. The processing of step S15 is an example of a second detection step of the present invention, and is executed by the second detection processing unit 74 of the image processing unit 8.

[0074] Specifically, each time the protruding region included in the pixel row is masked in the process of step S14, the image processing unit 8 determines whether the masked pixel row includes pixels that constitute the colored region Y11. When the image processing unit 8 first determines that the masked pixel row includes pixels that constitute the colored region Y11, it acquires the length L3 (see FIG. 8) (number of pixels) of the colored region Y11 included in the pixel row. From the time the image processing unit 8 first determines that the masked pixel row includes pixels that constitute the colored region Y11, each time the image processing unit 8 masks the protruding region included in the pixel row in the process of step S14, it counts the number of pixels that constitute the colored region Y11 included in the masked pixel row. When the image processing unit 8 determines that the number of pixels that constitute the colored region Y11 included in the masked pixel row exceeds the threshold, it acquires the length L4 (see FIG. 8) (number of pixels) of the colored region Y11 included in the pixel row. The image processing unit 8 also calculates the second tilt angle θ2 based on the difference between the length L4 and the length L3 and the distance (number of pixels) corresponding to the time from when the length L3 was acquired to when the length L4 was acquired. Then, the image processing unit 8 determines whether the second tilt angle θ2 is positive or negative based on the shape of the non-mask region Y13.

[0075] <Step S16> In step S16, the image processing unit 8 detects a third tilt angle θ3 (see FIG. 2) of the line sensor 51 with respect to the width direction D12, based on the first tilt angle θ1 detected in the process of step S13 and the second tilt angle θ2 detected in the process of step S15. The process of step S16 is an example of a third detection step of the present invention, and is executed by the third detection processing unit 75 of the image processing unit 8.

[0076] Specifically, the image processor 8 calculates the third tilt angle θ3 by subtracting the first tilt angle θ1 from the second tilt angle θ2.

[0077] <Step S17> In step S17, the control unit 7 outputs the third tilt angle θ3 detected in the process of step S 16. The process of step S17 is executed by the output processing unit 65 of the control unit 7.

[0078] Specifically, the control unit 7 displays the third tilt angle θ3 detected in the process of step S16 on the operation display unit 6. This allows the worker adjusting the attitude of the line sensor 51 to recognize the third tilt angle θ3.

[0079] In this manner, the image forming apparatus 100 acquires shape data X10 indicating the shape of the specific sheet conveyed along the sheet conveyance path R11. A first tilt angle θ1 is detected based on the acquired shape data X10. The acquired shape data X10 is used to mask the protruding area of the specific image data Y10 that protrudes from the sheet area X11. A second tilt angle θ2 is detected with respect to the second direction D14 of a boundary Y14 between a masked area Y12 and an unmasked area Y13 that face each other along the first direction D13 in the specific image data Y10 in which the protruding area is masked. A third tilt angle θ3 of the line sensor 51 with respect to the width direction D12 is detected based on the first tilt angle θ1 and the second tilt angle θ2. This makes it possible to detect the third tilt angle θ3 even when the axis of the tension roller that stretches the conveyance belt 41 is inclined with respect to the width direction D12.

[0080] The control unit 7 may include an adjustment processing unit 66 shown in FIG.

[0081] The adjustment processing unit 66 adjusts the attitude of the line sensor 51 based on the third tilt angle θ3 detected by the third detection processing unit 75. Specifically, the adjustment processing unit 66 adjusts the attitude of the line sensor 51 using an adjustment mechanism (not shown) that can adjust the attitude of the line sensor 51.

[0082] This allows the attitude of the line sensor 51 to be adjusted automatically.

[0083] [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.

[0084] <Appendix 1> an image forming unit that forms an image on a sheet transported along a predetermined transport path; an imaging unit that is provided on the transport path upstream of the image forming unit in the sheet transport direction and elongated along a width direction perpendicular to the transport direction, and that images the sheet; a transport processing unit that transports a predetermined specific sheet along the transport path; an acquisition processing unit that uses the imaging unit to acquire shape data that indicates the shape of the specific sheet transported by the transport processing unit; and a first detection processing unit that detects a first amount of inclination with respect to a first direction corresponding to the transport direction of an end portion in a second direction corresponding to the width direction in a sheet area included in the shape data acquired by the acquisition processing unit. An image forming apparatus comprising: a mask processing unit that uses the shape data acquired by the acquisition processing unit to mask an overhanging area that extends beyond the sheet area in specific image data that is larger in size in the first direction than the sheet area; a second detection processing unit that detects a second tilt amount with respect to the second direction of the boundary between a masked area and a non-masked area that face each other along the first direction in the specific image data in which the overhanging area has been masked by the mask processing unit; and a third detection processing unit that detects a third tilt amount with respect to the width direction of the imaging unit based on the first tilt amount detected by the first detection processing unit and the second tilt amount detected by the second detection processing unit.

[0085] <Appendix 2> The image forming apparatus described in Appendix 1, wherein the specific image data is data of the same size as the shape data, the mask processing unit determines the area outside the area in the specific image data that overlaps with the sheet area when the shape data is overlaid on the specific image data without shifting as the protruding area, and the specific image data has a colored area positioned at a position that overlaps with the end of the sheet area on a specific direction side along the first direction.

[0086] <Appendix 3> 3. The image forming apparatus according to claim 1, further comprising an output processing unit that outputs the third tilt amount detected by the third detection processing unit.

[0087] <Appendix 4> 4. The image forming apparatus according to claim 1, further comprising an adjustment processing unit that adjusts the attitude of the imaging unit based on the third tilt amount detected by the third detection processing unit.

[0088] <Appendix 5> a detection method to be performed by an image forming apparatus including an image forming unit that forms an image on a sheet conveyed along a predetermined conveying path, and an imaging unit that is provided on the conveying path upstream of the image forming unit in the sheet conveying direction and elongated along a width direction perpendicular to the conveying direction, and that images the sheet, the detection method including a conveying step of conveying a predetermined specific sheet along the conveying path, an acquisition step of acquiring shape data indicating a shape of the specific sheet conveyed in the conveying step using the imaging unit, and detecting a first skew amount with respect to a first direction corresponding to the conveying direction of an end portion in a second direction corresponding to the width direction in a sheet area included in the shape data acquired in the acquisition step a masking step of using the shape data acquired by the acquisition step to mask an overhanging area that overhangs the sheet area in specific image data that is larger in size in the first direction than the sheet area; a second detection step of detecting a second tilt amount with respect to the second direction of a boundary between a masked area and a non-masked area that face each other along the first direction in the specific image data in which the overhanging area has been masked by the masking step; and a third detection step of detecting a third tilt amount with respect to the width direction of the imaging unit based on the first tilt amount detected by the first detection step and the second tilt amount detected by the second detection step. [Explanation of symbols]

[0089] 1 chassis 2 Sheet transport section 3 Image forming unit 4 Transport unit 5 Shape reading unit 6 Operation display section 7 Control Unit 8 Image processing section 11 Paper cassette 12 Paper output tray 21 Pickup roller 22 Transport roller 30 Recording head 30A nozzle 31 Line Head 32 Line Head 33 Line Head 34 Line Head 35 Head Frame 41 Conveyor belt 42 First tension roller 43 Second tension roller 44 Third tension roller 45 Transport frame 51 Line Sensor 52 AFE circuit 61 CPU 62 ROM 63 RAM 64 Transport processing section 65 Output Processing Section 66 Adjustment processing section 71 Acquisition processing unit 72 First detection processing section 73 Mask processing section 74 Second detection processing section 75 Third detection processing section 100 Image forming device

Claims

1. an image forming unit that forms an image on a sheet that is conveyed along a predetermined conveying path; an imaging unit that is provided on the conveying path upstream of the image forming unit in the sheet conveying direction and elongated along a width direction perpendicular to the conveying direction, and that images the sheet; a conveyance processing unit that conveys a predetermined specific sheet along the conveyance path; an acquisition processing unit that acquires shape data indicating a shape of the specific sheet conveyed by the conveyance processing unit using the imaging unit; a first detection processing unit that detects a first inclination amount of an end portion in a second direction corresponding to the width direction in a sheet area included in the shape data acquired by the acquisition processing unit with respect to a first direction corresponding to the conveying direction; a mask processing unit that uses the shape data acquired by the acquisition processing unit to mask a protruding area of specific image data that is larger in size in the first direction than the sheet area and that protrudes from the sheet area; a second detection processing unit that detects a second tilt amount with respect to the second direction of a boundary between a masked area and a non-masked area that face each other along the first direction in the specific image data in which the protruding area has been masked by the mask processing unit; a third detection processing unit that detects a third tilt amount of the imaging unit with respect to the width direction based on the first tilt amount detected by the first detection processing unit and the second tilt amount detected by the second detection processing unit; An image forming apparatus comprising:

2. The specific image data is data of the same size as the shape data, the mask processing unit determines, as the protruding area, an area outside a region in the specific image data that overlaps with the sheet area when the shape data is superimposed on the specific image data without any misalignment; the specific image data has a colored area arranged at a position overlapping an end of the sheet area on a specific direction side along the first direction, The image forming apparatus according to claim 1 .

3. an output processing unit that outputs the third tilt amount detected by the third detection processing unit; 3. The image forming apparatus according to claim 1.

4. an adjustment processing unit that adjusts the attitude of the imaging unit based on the third tilt amount detected by the third detection processing unit; 3. The image forming apparatus according to claim 1.

5. A detection method executed in an image forming apparatus including: an image forming unit that forms an image on a sheet conveyed along a predetermined conveying path; and an imaging unit that is provided on the conveying path upstream of the image forming unit in a conveying direction of the sheet, the imaging unit being elongated along a width direction perpendicular to the conveying direction, and that images the sheet, a conveying step of conveying a predetermined specific sheet along the conveying path; an acquiring step of acquiring shape data indicating a shape of the specific sheet conveyed by the conveying step using the imaging unit; a first detection step of detecting a first inclination amount of an end portion in a second direction corresponding to the width direction in a sheet area included in the shape data acquired in the acquisition step, with respect to a first direction corresponding to the conveying direction; a masking step of masking a protruding area of specific image data that is larger in size in the first direction than the sheet area, using the shape data acquired by the acquiring step; a second detection step of detecting a second tilt amount with respect to the second direction of a boundary between a masked area and a non-masked area that face each other along the first direction in the specific image data in which the protruding area has been masked by the mask step; a third detection step of detecting a third tilt amount of the imaging unit with respect to the width direction based on the first tilt amount detected in the first detection step and the second tilt amount detected in the second detection step; A detection method comprising:

Images