Image forming apparatus, image forming method, and program

Abstract

To provide an image formation device, an image formation method, and a program which can detect a deviation amount of an image with high accuracy.SOLUTION: An image formation device includes: a recording head having a plurality of nozzles; a printing part for printing a reference adjustment pattern on a recording medium using a reference nozzle out of the plurality of nozzles, and printing an adjustment pattern on the recording medium using a designation nozzle that is a nozzle separated by a predetermined distance with the nozzle separated by a predetermined conveyance amount from the reference nozzle in a sub-scanning direction as a reference, when the recording medium is conveyed by the predetermined conveyance amount in the sub-scanning direction from the reference nozzle; a detection part for detecting the reference adjustment pattern and the adjustment pattern; a calculation part for calculating a distance between the reference adjustment pattern and the adjustment pattern in the sub-scanning direction; and a determination part for determining whether or not a standard deviation of the distance calculated by the calculation part is equal to or more than a predetermined value.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Patent Document 1 discloses a technique for detecting the amount of image misalignment during image formation with high accuracy. Summary of the Invention [Problem to be solved by the invention]

[0003] However, with the above technology, if the ejection of liquid such as ink from the nozzle is curved when forming an image of a pattern for detecting the amount of image misalignment, it is difficult to accurately detect the amount of image misalignment.

[0004] The present invention has been made in view of the above, and has an object to provide an image forming apparatus, an image forming method, and a program that are capable of detecting the amount of misalignment of an image with high accuracy. [Means for solving the problem]

[0005] In order to solve the above-mentioned problems and achieve the object, the present invention provides a recording head having a plurality of nozzles; a printing unit that prints a reference adjustment pattern on a recording medium using a reference nozzle among the plurality of nozzles, and when the recording medium is transported a predetermined amount in a sub-scanning direction from the reference nozzle, prints an adjustment pattern on the recording medium using a designated nozzle that is a nozzle that is a predetermined distance away from the reference nozzle in the sub-scanning direction based on the nozzle that is the predetermined amount away from the reference nozzle; a detection unit that detects the reference adjustment pattern and the adjustment patterns; a calculation unit that calculates the distance between the reference adjustment pattern and the adjustment pattern in the sub-scanning direction; and a determination unit that determines whether the standard deviation of the distance calculated by the calculation unit is equal to or greater than a predetermined value. [Effects of the Invention]

[0006] The present invention has the effect of enabling the amount of image misalignment to be detected with high accuracy. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a perspective view showing an example of the interior of an image forming apparatus according to the present embodiment. [Figure 2] FIG. 2 is a top view showing an example of the internal mechanical configuration of the image forming apparatus according to the present embodiment. [Figure 3] FIG. 3 is an explanatory diagram of an example of a carriage of the image forming apparatus according to the present embodiment. [Figure 4] FIG. 4 is a perspective view showing an external appearance of an example of the imaging unit according to the present embodiment. [Figure 5] FIG. 5 is an exploded perspective view of an example of the imaging unit according to the present embodiment. [Figure 6] FIG. 6 is a vertical cross-sectional view of the imaging unit as seen from the X1 direction in FIG. [Figure 7] FIG. 7 is a vertical cross-sectional view of the imaging unit as seen from the X2 direction in FIG. [Figure 8] FIG. 8 is a plan view of the imaging unit according to the present embodiment. [Figure 9] FIG. 9 is a diagram showing a specific example of a reference chart provided in the image forming apparatus according to the present embodiment. [Figure 10] FIG. 10 is a vertical cross-sectional view of an imaging unit included in the image forming apparatus according to this embodiment. [Figure 11] FIG. 11 is a plan view of the imaging unit of FIG. 10 as viewed from the X2 direction. [Figure 12] FIG. 12 is a structural diagram of an example of the conveying roller and its surroundings provided in the image forming apparatus according to the present embodiment. [Figure 13] FIG. 13 is a diagram showing the hardware configuration of the image forming apparatus according to this embodiment. [Figure 14] FIG. 14 is a block diagram showing an example of a functional configuration of the image forming apparatus according to the present embodiment. [Figure 15]FIG. 15 is a diagram showing an example of a test pattern formed on a recording medium by the image forming apparatus according to the present embodiment. [Figure 16] FIG. 16 is an explanatory diagram of an example of a method for forming a test pattern in the image forming apparatus according to the present embodiment. [Figure 17] FIG. 17 is an explanatory diagram of an example of a method for forming a test pattern in the image forming apparatus according to the present embodiment. [Figure 18] FIG. 18 is an explanatory diagram of an example of a method for forming a test pattern in the image forming apparatus according to the present embodiment. [Figure 19] FIG. 19 is an explanatory diagram of an example of a method for forming a test pattern in the image forming apparatus according to the present embodiment. [Figure 20] FIG. 20 is an explanatory diagram of an example of a method for forming a test pattern in the image forming apparatus according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an image forming apparatus, an image forming method, and a program will be described in detail below with reference to the accompanying drawings.

[0009] First, an example of the mechanical configuration of an image forming apparatus according to the present embodiment will be described with reference to Figures 1 to 3. Figure 1 is a perspective view showing an example of the interior of an image forming apparatus according to the present embodiment. Figure 2 is a top view showing an example of the internal mechanical configuration of an image forming apparatus according to the present embodiment. Figure 3 is an explanatory diagram of an example of a carriage of an image forming apparatus according to the present embodiment.

[0010] As shown in Fig. 1, an image forming apparatus 100 according to this embodiment includes a carriage 5 that moves back and forth in the main scanning direction (the direction of arrow A in the figure). The carriage 5 is supported by a main guide rod 3 that extends along the main scanning direction. The carriage 5 also has a connecting piece 5a. The connecting piece 5a engages with a sub-guide member 4 that is provided in parallel with the main guide rod 3, stabilizing the posture of the carriage 5.

[0011] The carriage 5 is connected to a timing belt 11 that is stretched between a drive pulley 9 and a driven pulley 10. The drive pulley 9 is rotated by the drive of a main scanning motor 8. The driven pulley 10 has a mechanism for adjusting the distance between itself and the drive pulley 9, and serves to apply a predetermined tension to the timing belt 11. The carriage 5 moves back and forth in the main scanning direction as the timing belt 11 is advanced by the drive of the main scanning motor 8. The movement amount and movement speed of the carriage 5 are controlled based on an encoder value output by a main scanning encoder sensor 131 provided on the carriage 5 upon detecting marks on an encoder sheet 14, for example, as shown in FIG. 2.

[0012] As shown in FIG. 3, the carriage 5 is equipped with print heads 6A, 6B, and 6C. The print head 6A has a nozzle row 6Ay with a large number of nozzles that eject yellow (Y) ink, a nozzle row 6Ac with a large number of nozzles that eject cyan (C) ink (one example of liquid), a nozzle row 6Am with a large number of nozzles that eject magenta (M) ink, and a nozzle row 6Ak with a large number of nozzles that eject black (K) ink, all arranged in a single row. Hereinafter, these print heads 6A, 6B, and 6C will be collectively referred to as print head 6. The print head 6 is supported by the carriage 5 with its ejection surface (nozzle surface) facing downward (toward the print medium P).

[0013] The cartridge 7, which is an ink supply body for supplying ink to the recording head 6, is not mounted on the carriage 5 but is disposed at a predetermined position within the image forming apparatus 100. The cartridge 7 and the recording head 6 are connected by a pipe, and ink is supplied from the cartridge 7 to the recording head 6 via this pipe.

[0014] As shown in FIG. 2, a platen 16 is provided at a position facing the ejection surface of the recording head 6. The platen 16 supports the recording medium P when ink is ejected from the recording head 6 onto the recording medium P. The platen 16 has a large number of through-holes that penetrate the platen 16 in the thickness direction, and rib-like protrusions are formed to surround each through-hole. A suction fan provided on the opposite side of the platen 16 from the surface that supports the recording medium P is operated to prevent the recording medium P from falling off the platen 16. The recording medium P is sandwiched between conveying rollers driven by a sub-scanning motor 12 (see FIG. 13), which will be described later, and is conveyed intermittently on the platen 16 in the sub-scanning direction (the direction of arrow B in the figure). As described above, the recording head 6 has a large number of nozzles arranged in the sub-scanning direction.

[0015] The image forming apparatus 100 according to this embodiment intermittently transports a recording medium P in the sub-scanning direction, and while the transport of the recording medium P is stopped, the carriage 5 is reciprocated in the main scanning direction while selectively driving the nozzles of the recording head 6 in accordance with image data, causing the recording head 6 to eject ink onto the recording medium P on a platen 16, thereby recording an image on the recording medium P. The image forming apparatus 100 according to this embodiment also includes a maintenance mechanism 15 for maintaining the reliability of the recording head 6. The maintenance mechanism 15 performs cleaning of the ejection surface of the recording head 6, capping, and discharging unnecessary ink from the recording head 6. As shown in FIG. 3, the carriage 5 is also equipped with an imaging unit 20 for capturing an image of a test pattern TP (see FIG. 15) formed on the recording medium P, which will be described later. Details of the imaging unit 20 will be described later.

[0016] The above-described components constituting the image forming apparatus 100 according to this embodiment are disposed inside an exterior body 1. An openable and closable cover member 2 is provided on the exterior body 1. When maintenance of the image forming apparatus 100 is performed or when a jam occurs, the cover member 2 can be opened to perform work on the components provided inside the exterior body 1.

[0017] 3 may or may not have a reference chart that is imaged simultaneously with the test pattern TP. The reference chart is used to calculate the colorimetric values ​​of the test pattern TP using, for example, the RGB values ​​of each reference patch (see FIG. 9).

[0018] Next, a specific example of the imaging unit 20 having a reference chart will be described. Fig. 4 is a perspective view showing the appearance of an example of the imaging unit according to this embodiment. Fig. 5 is an exploded perspective view of an example of the imaging unit according to this embodiment. Fig. 6 is a vertical cross-sectional view of the imaging unit as seen from the X1 direction in Fig. 4. Fig. 7 is a vertical cross-sectional view of the imaging unit as seen from the X2 direction in Fig. 4. Fig. 8 is a plan view of the imaging unit according to this embodiment.

[0019] The imaging unit 20 includes a housing 51 formed, for example, in the shape of a rectangular box. The housing 51 includes, for example, a bottom plate 51a and a top plate 51b that face each other with a predetermined gap between them, and side walls 51c, 51d, 51e, and 51f that connect the bottom plate 51a and the top plate 51b. The bottom plate 51a and the side walls 51d, 51e, and 51f of the housing 51 are integrally formed, for example, by molding, while the top plate 51b and the side wall 51c are detachable. FIG. 5 shows the housing 51 with the top plate 51b and the side wall 51c removed.

[0020] The imaging unit 20 is installed, for example, in a transport path for the recording medium P on which the test pattern TP is formed, with a part of the housing 51 supported by a predetermined support member. At this time, the imaging unit 20 is supported by the predetermined support member so that the bottom plate portion 51a of the housing 51 faces the transported recording medium P in a substantially parallel state with a gap d therebetween, as shown in FIGS.

[0021] An opening 53 is provided in the bottom plate 51a of the housing 51, which faces the recording medium P on which the test pattern TP is formed, to enable the test pattern TP outside the housing 51 to be imaged from inside the housing 51.

[0022] A reference chart 300 is disposed on the inner surface of the bottom plate 51a of the housing 51, adjacent to the opening 53 via a support member 63. The reference chart 300 is imaged together with the test pattern TP by a sensor unit 26 (described later) when measuring the color of the test pattern TP and acquiring its RGB values. Details of the reference chart 300 will be described later.

[0023] Meanwhile, a circuit board 54 is disposed on the top plate portion 51b side inside the housing 51. As shown in Fig. 8, the housing 51 has a rectangular box shape with an open surface facing the circuit board 54, and is fixed to the circuit board 54 by fastening members 54b. The shape of the housing 51 is not limited to a rectangular box, and may be, for example, a cylindrical box shape or an elliptical cylindrical box shape having a bottom plate portion 51a in which an opening 53 is formed.

[0024] Further, a sensor unit 26 that captures an image is disposed between the top panel 51b of the housing 51 and the circuit board 54. As shown in Fig. 6, the sensor unit 26 includes a two-dimensional sensor 27 such as a CCD (Charge Coupled Device) sensor or a CMOS (Complementary Metal Oxide Semiconductor) sensor, and an imaging lens 28 that forms an optical image of the imaging range of the sensor unit 26 on the light receiving surface (imaging area) of the two-dimensional sensor 27. The two-dimensional sensor 27 is a light receiving element array in which light receiving elements that receive reflected light from a subject are arranged two-dimensionally.

[0025] The sensor unit 26 is held by, for example, a sensor holder 56 formed integrally with the side wall 51e of the housing 51. The sensor holder 56 has a ring portion 56a provided in a position facing a through hole 54a formed in the circuit board 54. The ring portion 56a has a through hole of a size following the outer shape of a protruding portion of the sensor unit 26 on the imaging lens 28 side. The protruding portion of the sensor unit 26 on the imaging lens 28 side is inserted into the ring portion 56a of the sensor holder 56, so that the imaging lens 28 faces the bottom plate 51a side of the housing 51 through the through hole 54a of the circuit board 54.

[0026] At this time, sensor unit 26 is held in a positioned state by sensor holder 56 so that the optical axis, indicated by the dashed-dotted line in Fig. 6, is approximately perpendicular to bottom plate 51a of housing 51 and so that opening 53 and reference chart 300 (described later) are included in the imaging range. As a result, sensor unit 26 images test pattern TP outside housing 51 through opening 53 in part of the imaging area of ​​two-dimensional sensor 27. In addition, sensor unit 26 can image reference chart 300 placed inside housing 51 in another part of the imaging area of ​​two-dimensional sensor 27.

[0027] The sensor unit 26 is electrically connected to a circuit board 54, on which various electronic components are mounted, via, for example, a flexible cable. The circuit board 54 is also provided with an external connection connector 57 to which a connection cable for connecting the imaging unit 20 to the main control board of the image forming apparatus 100 is attached.

[0028] In the imaging unit 20, a pair of light sources 58 are disposed on the circuit board 54 at positions on a center line OA in the sub-scanning direction that passes through the center of the sensor unit 26, and at positions spaced apart by a predetermined distance in the sub-scanning direction from the center of the sensor unit 26. The light sources 58 illuminate the imaging range substantially uniformly when the sensor unit 26 captures an image. For example, an LED (Light Emitting Diode) is used as the light source 58, which is advantageous for saving space and power consumption.

[0029] In this embodiment, as shown in Figures 7 and 8, a pair of LEDs are used as light source 58, which are evenly arranged in a direction perpendicular to the direction in which opening 53 and reference chart 300 are aligned, with the center of imaging lens 28 as the reference point.

[0030] The two LEDs used as the light source 58 are mounted, for example, on the surface of the circuit board 54 facing the bottom plate 51a. However, the light source 58 need not necessarily be directly mounted on the circuit board 54 as long as it is positioned so that the imaging range of the sensor unit 26 can be illuminated approximately uniformly with diffused light. The two LEDs are positioned symmetrically about the two-dimensional sensor 27, thereby enabling imaging of the imaging surface under the same illumination conditions as the reference chart 300. In addition, although an LED is used as the light source 58 in this embodiment, the type of light source 58 is not limited to an LED. For example, an organic electroluminescence (EL) element or the like may be used as the light source 58. When an organic EL element is used as the light source 58, illumination light having a spectral distribution similar to that of sunlight can be obtained, which is expected to improve color measurement accuracy.

[0031] 8, sensor unit 26 includes light absorber 55c directly below light source 58 and two-dimensional sensor 27. Light absorber 55c reflects or absorbs light from light source 58 in directions other than toward two-dimensional sensor 27. Light absorber 55c has an acute angled shape and is formed so that incident light from light source 58 is reflected toward the inner surface of light absorber 55c, and is not reflected in the incident direction.

[0032] Additionally, an optical path length changing member 59 is disposed inside the housing 51 in the optical path between the sensor unit 26 and the test pattern TP outside the housing 51, which is imaged by the sensor unit 26 through the opening 53. The optical path length changing member 59 is an optical element with a refractive index n that provides sufficient transmittance for the light from the light source 58. The optical path length changing member 59 functions to bring the imaging plane of the optical image of the test pattern TP outside the housing 51 closer to the imaging plane of the optical image of the reference chart 300 inside the housing 51. In other words, the imaging unit 20 changes the optical path length by disposing the optical path length changing member 59 in the optical path between the sensor unit 26 and the subject outside the housing 51. As a result, the imaging unit 20 aligns both the imaging plane of the test pattern TP outside the housing 51 and the imaging plane of the reference chart 300 inside the housing 51 with the light receiving surface of the two-dimensional sensor 27 of the sensor unit 26. Therefore, the sensor unit 26 can capture images in focus of both the test pattern TP outside the housing 51 and the reference chart 300 inside the housing 51 .

[0033] 6, for example, both end portions of the surface of the optical path length change member 59 facing the bottom plate portion 51a are supported by a pair of ribs 60, 61. Furthermore, a pressing member 62 is disposed between the surface of the optical path length change member 59 facing the top plate portion 51b and the circuit board 54, thereby preventing the optical path length change member 59 from moving inside the housing 51. The optical path length change member 59 is disposed so as to close the opening 53 provided in the bottom plate portion 51a of the housing 51. Therefore, the optical path length change member 59 also has the function of preventing impurities such as ink mist and dust that enter the housing 51 from the outside through the opening 53 from adhering to the sensor unit 26, the light source 58, the reference chart 300, etc.

[0034] The mechanical configuration of the imaging unit 20 described above is merely an example and is not limited to this. The imaging unit 20 may be configured to capture an image of the test pattern TP outside the housing 51 through the opening 53 using the sensor unit 26 provided inside the housing 51 at least while the light source 58 provided inside the housing 51 is turned on. The imaging unit 20 can be modified or changed in various ways with respect to the above configuration.

[0035] For example, in the imaging unit 20 described above, the reference chart 300 is disposed on the inner surface of the bottom plate 51a of the housing 51. However, an opening separate from the opening 53 may be provided at the position where the reference chart 300 is to be disposed on the bottom plate 51a of the housing 51, and the reference chart 300 may be attached from outside the housing 51 at the position where this opening is provided. In this case, the sensor unit 26 captures an image of the test pattern TP formed on the recording medium P through the opening 53, and also captures an image of the reference chart 300 attached from outside to the bottom plate 51a of the housing 51 through another opening separate from the opening 53. This example has the advantage that the reference chart 300 can be easily replaced if it becomes dirty or otherwise defective.

[0036] Next, a specific example of the reference chart 300 arranged on the housing 51 of the imaging unit 20 will be described with reference to Fig. 9. Fig. 9 is a diagram showing a specific example of the reference chart provided in the image forming apparatus according to the present embodiment.

[0037] The reference chart 300 shown in FIG. 9 has a plurality of color measurement patch rows 310 to 340 in which color measurement patches for color measurement are arranged, a distance measurement line 350, and a marker 360 for specifying the chart position.

[0038] The colorimetric patch arrays 310 to 340 include a colorimetric patch array 310 in which colorimetric patches of primary colors YMCK are arranged in gradation order, a colorimetric patch array 320 in which colorimetric patches of secondary colors RGB are arranged in gradation order, a colorimetric patch array (achromatic gradation pattern) 330 in which grayscale colorimetric patches are arranged in gradation order, and a colorimetric patch array 340 in which colorimetric patches of tertiary colors are arranged.

[0039] The distance measurement line 350 is formed as a rectangular frame surrounding the plurality of color measurement patch rows 310 to 340. The chart position specifying markers 360 are provided at the four corners of the distance measurement line 350 and function as markers for specifying the position of each color measurement patch. By identifying the distance measurement line 350 and the chart position specifying markers 360 at its four corners from the image of the reference chart 300 captured by the sensor unit 26, the position of the reference chart 300 and the position of each color measurement patch can be specified.

[0040] Each of the colorimetry patches constituting the colorimetry patch arrays 310-340 is used as a reference for color tones that reflects the imaging conditions of the sensor unit 26. The configuration of the colorimetry patch arrays 310-340 arranged on the reference chart 300 is not limited to the example shown in FIG. 9 , and any colorimetry patch array can be used. For example, colorimetry patches that can identify as wide a color range as possible may be used, or the colorimetry patch array 310 for the primary colors of YMCK and the colorimetry patch array 330 for the grayscale may be composed of patches with colorimetry values ​​of color materials used in the image forming apparatus 100. The colorimetry patch array 320 for the secondary colors of RGB may be composed of patches with colorimetry values ​​that can be produced by the color materials used in the image forming apparatus 100, or a reference color chart with defined colorimetry values, such as Japan Color, may be used.

[0041] In this embodiment, the reference chart 300 is used, which has color measurement patch arrays 310 to 340 in the shape of general patches (color charts), but the reference chart 300 does not necessarily have to have such color measurement patch arrays 310 to 340. The reference chart 300 may have a configuration in which multiple colors that can be used for color measurement are arranged so that their respective positions can be identified.

[0042] As described above, the reference chart 300 is disposed adjacent to the opening 53 on the inner surface side of the bottom plate portion 51a of the housing 51, and therefore can be imaged by the sensor unit 26 simultaneously with the test pattern TP outside the housing 51. Note that "imaging simultaneously" here means acquiring one frame of image data including the test pattern TP outside the housing 51 and the reference chart 300. In other words, even if there is a time lag in acquiring data for each pixel, acquiring image data including the test pattern TP outside the housing 51 and the reference chart 300 in one frame will result in the test pattern TP outside the housing 51 and the reference chart 300 being imaged simultaneously.

[0043] Next, a specific example of the imaging unit 20 that does not have the reference chart 300 will be described. Specific examples of the imaging unit 20 will be described in detail below with reference to FIGS. 10 and 11. FIG. 10 is a vertical cross-sectional view of the imaging unit included in the image forming apparatus according to this embodiment. FIG. 11 is a plan view of the imaging unit of FIG. 10 as viewed from the X2 direction.

[0044] 10, the imaging unit 20 has a light source 42 and a sensor unit 26 mounted on a substrate 41 fixed to the carriage 5. The light source 42 is, for example, an LED, and irradiates illumination light onto a test pattern TP formed on a recording medium P, which is the subject, and the reflected light (diffusely reflected light or specularly reflected light) is incident on the sensor unit 26. As shown in FIG. 11, four light sources 42 are arranged to surround the test pattern TP formed on the recording medium P, and irradiate the test pattern TP with uniform illumination light.

[0045] Sensor unit 26 includes two-dimensional sensor 27, such as a CCD sensor or a CMOS sensor, and imaging lens 28. Sensor unit 26 causes reflected light of illumination light emitted from light source 42 onto test pattern TP to enter two-dimensional sensor 27 through imaging lens 28. Two-dimensional sensor 27 converts the incident light into an analog signal by photoelectric conversion, and outputs the signal as a captured image of test pattern TP.

[0046] Next, a description will be given of a conveying section that conveys the recording medium P, which is the object to be conveyed. Fig. 12 is a structural diagram of an example of the conveying roller and its surroundings that an image forming apparatus according to this embodiment has. As shown in Fig. 12, the recording medium P is conveyed intermittently in a sub-scanning direction (arrow B direction in the figure) that is perpendicular to the main scanning direction (arrow A direction in the figure), which is the direction of movement of the carriage 5. At this time, an encoder 35 provided coaxially with the conveying roller 152 is read by a sub-scanning encoder sensor 132 provided on a side plate.

[0047] Based on the information thus read, the transport amount of the recording medium P is controlled by a sensor control unit 124 (see FIG. 13) electrically connected to the sub-scanning encoder sensor 132. In this example, the encoder 35 is configured as a rotary encoder in which an optical grating is arranged in a disk shape so that the angle, amount of rotation, rotation speed, etc. can be detected.

[0048] Next, the hardware configuration of the image forming apparatus 100 according to this embodiment will be described with reference to Fig. 13. Fig. 13 is a diagram showing the hardware configuration of the image forming apparatus according to this embodiment.

[0049] As shown in FIG. 13, the image forming apparatus 100 according to this embodiment includes a CPU (Central Processing Unit) 110, a ROM (Read Only Memory) 102, a RAM (Random Access Memory) 103, a printhead driver 104, a main scanning driver 105, a sub-scanning driver 106, a control FPGA (Field-Programmable Gate Array) 120, a printhead 6, a main scanning encoder sensor 131, an imaging unit 20, a main scanning motor 8, a conveying unit 150, and a sub-scanning motor 12.

[0050] The CPU 110, ROM 102, RAM 103, printhead driver 104, main scanning driver 105, sub-scanning driver 106, and control FPGA 120 are mounted on a main control board 130. The printhead 6, main scanning encoder sensor 131, and imaging unit 20 are mounted on the carriage 5 as described above. The sub-scanning encoder sensor 132 and conveyance rollers 152 are mounted on the conveyance unit 150 described above.

[0051] The CPU 110 is responsible for overall control of the image forming apparatus 100. For example, the CPU 110 uses the RAM 103 as a work area to execute various control programs stored in the ROM 102 and outputs control commands for controlling various operations in the image forming apparatus 100. In particular, in the image forming apparatus 100 according to this embodiment, the CPU 110 realizes functions such as forming a test pattern TP. Details of these functions will be described later.

[0052] The print head driver 104, main scanning driver 105, and sub-scanning driver 106 are drivers for driving the print head 6, main scanning motor 8, and sub-scanning motor 12, respectively. The control FPGA 120 controls various operations in the image forming apparatus 100 in cooperation with the CPU 110. The control FPGA 120 includes, as functional components, a CPU control unit 121, a memory control unit 122, an ink ejection control unit 123, a sensor control unit 124, and a motor control unit 125, for example.

[0053] The CPU control unit 121 communicates with the CPU 110, transmitting various pieces of information acquired by the control FPGA 120 to the CPU 110, and inputting control commands output from the CPU 110. The memory control unit 122 performs memory control for the CPU 110 to access the ROM 102 and RAM 103. The ink ejection control unit 123 controls the operation of the printhead driver 104 in response to control commands from the CPU 110, thereby controlling the timing of ink ejection from the printhead 6 driven by the printhead driver 104.

[0054] The sensor control unit 124 performs processing on sensor signals such as encoder values ​​output from the main scanning encoder sensor 131 and the sub-scanning encoder sensor 132. For example, the sensor control unit 124 performs processing to calculate the position, movement speed, movement direction, etc. of the carriage 5 based on the encoder value output from the main scanning encoder sensor 131. Furthermore, for example, the sensor control unit 124 performs processing to calculate the rotation speed, rotation direction, etc. of the conveyance roller 152 that conveys the recording medium P based on the encoder value output from the sub-scanning encoder sensor 132.

[0055] The motor control unit 125 controls the operation of the main scanning driver 105 in response to a control command from the CPU 110, thereby controlling the main scanning motor 8 driven by the main scanning driver 105 and controlling the movement of the carriage 5 in the main scanning direction. The motor control unit 125 also controls the operation of the sub scanning driver 106 in response to a control command from the CPU 110, thereby controlling the sub scanning motor 12 driven by the sub scanning driver 106 and controlling the movement (conveyance) of the recording medium P in the sub scanning direction by the conveyance roller 152.

[0056] The above-described units are examples of control functions realized by the control FPGA 120, and various other control functions may be realized by the control FPGA 120. Also, all or part of the above control functions may be realized by a program executed by the CPU 110 or another general-purpose CPU. Also, part of the above control functions may be realized by dedicated hardware, such as another FPGA or an ASIC (Application Specific Integrated Circuit), different from the control FPGA 120.

[0057] The recording head 6 has multiple nozzles that eject ink to form images (see Figure 3), and is driven by a recording head driver 104 whose operation is controlled by the CPU 110 and the control FPGA 120, and ejects liquid such as ink onto a recording medium P on the platen 16 to form (print) various images.

[0058] The main scanning encoder sensor 131 detects the marks on the encoder sheet 14 and outputs the obtained encoder value to the control FPGA 120. This encoder value is used by the sensor control unit 124 of the control FPGA 120 to calculate the position, movement speed, and movement direction of the carriage 5. The position, movement speed, and movement direction of the carriage 5 calculated by the sensor control unit 124 from the encoder value are sent to the CPU 110. The CPU 110 generates a control command for controlling the main scanning motor 8 based on the position, movement speed, and movement direction of the carriage 5 and outputs the control command to the motor control unit 125.

[0059] Image capturing unit 20 captures an image of test pattern TP formed on recording medium P under the control of CPU 110 and performs various processes on the captured image, and includes two-dimensional sensor CPU 140 and two-dimensional sensor 27. As described above, two-dimensional sensor 27 is a CCD sensor, CMOS sensor, or the like, and captures an image of test pattern TP and reference frame (frame line) F under predetermined operating conditions based on various setting signals sent from two-dimensional sensor CPU 140. Two-dimensional sensor 27 then sends the captured image to two-dimensional sensor CPU 140.

[0060] Two-dimensional sensor CPU 140 controls two-dimensional sensor 27 and processes images captured by two-dimensional sensor 27. Specifically, two-dimensional sensor CPU 140 sets various operating conditions for two-dimensional sensor 27 by sending various setting signals to imaging unit 20. Two-dimensional sensor CPU 140 also realizes calculation functions such as detecting markers of test pattern TP from a captured image of test pattern TP.

[0061] Furthermore, imaging unit 20 is provided with RAM and ROM, and two-dimensional sensor CPU 140 uses, for example, RAM as a working area to execute various control programs stored in ROM and output control commands for controlling various operations in imaging unit 20. Two-dimensional sensor CPU 140 also has a built-in function of AD converting the analog signal obtained by photoelectric conversion of two-dimensional sensor 27 into digital image data, and performing various image processing on the image data such as shading correction, white balance correction, gamma correction, and image data format conversion. Note that the various image processing on the captured image may be configured to be performed in part or in whole outside imaging unit 20.

[0062] The sub-scanning encoder sensor 132 reads the encoder 35 and outputs the obtained encoder value to the control FPGA 120. This encoder value is used by a sensor control unit 124 of the control FPGA 120 to calculate the rotation speed and rotation direction of a conveyance roller 152 that conveys the recording medium P. The rotation speed and rotation direction of the conveyance roller 152 calculated from the encoder value by the sensor control unit 124 are sent to the CPU 110. The CPU 110 generates a control command for controlling the sub-scanning motor 12 based on the rotation speed and rotation direction of the conveyance roller 152 and outputs the control command to the motor control unit 125. The conveyance roller 152 conveys the recording medium P by a predetermined conveyance distance by rotating at a rotation speed and in a rotation direction based on the control command received from the motor control unit 125.

[0063] In the image forming apparatus 100 according to this embodiment, the image forming unit that forms various images on the recording medium P is constituted by the recording head driver 104, main scanning driver 105, and sub-scanning driver 106, which are controlled by the CPU 110 and control FPGA 120 described above, and the recording head 6, main scanning motor 8, and sub-scanning motor 12, which are driven by these.

[0064] In Figure 13, the CPU 140 for the two-dimensional sensor and the imaging unit 20 are mounted on the carriage 5, but the CPU 140 for the two-dimensional sensor and the imaging unit 20 only need to be positioned so that they can properly image the test pattern TP formed on the recording medium P, and do not necessarily have to be mounted on the carriage 5.

[0065] Fig. 14 is a block diagram showing an example of the functional configuration of an image forming apparatus according to the present embodiment. Next, characteristic functions realized by CPU 110 and 2D sensor CPU 140 of image forming apparatus 100 will be described with reference to Fig. 14.

[0066] CPU 110, for example, uses RAM 103 as a work area to execute a control program stored in ROM 102, thereby realizing functions such as pattern forming unit 111, calculation unit 114, determination unit 115, and transport control unit 116. Also, CPU 140 for the two-dimensional sensor of imaging unit 20, for example, uses RAM as a work area to execute a control program stored in ROM, thereby realizing functions such as position detection unit 142.

[0067] The transport control unit 116 of the CPU 110 controls the transport rollers 152 of the transport unit 150 that transport the recording medium P. For example, the transport control unit 116 determines the rotation speed and rotation direction of the transport rollers 152 based on the encoder value output from the sub-scanning encoder sensor 132, and controls the transport of the recording medium P by the transport rollers 152 by sending a control command indicating the rotation speed and rotation direction to the transport rollers 152 of the transport unit 150 via the control FPGA 120.

[0068] The pattern forming unit 111 (an example of a printing unit) of the CPU 110 reads, for example, pattern data stored in advance in the ROM 102 or the like, and causes the image forming unit described above to perform an image forming operation according to this pattern data, thereby forming (printing) a test pattern TP on the recording medium P. The test pattern TP formed on the recording medium P by the pattern forming unit 111 is imaged by the imaging unit 20.

[0069] In this embodiment, the test pattern TP is composed of a set of markers M including at least a first marker M1 and a pair of second markers M2a and M2b. Details of the test pattern TP will be described later (see FIG. 15).

[0070] The pattern forming unit 111 uses the image forming unit to form a first marker M1 and one of a pair of second markers M2a, M2b (an example of a reference adjustment pattern) on the recording medium P, and after the recording medium P is transported by a predetermined transport amount, forms the other of the first marker M1 and the pair of second markers M2a, M2b (an example of an adjustment pattern) that was not formed before the transport.

[0071] In this embodiment, an example will be described in which the pattern forming unit 111 forms a first marker M1 on the recording medium P, and then forms a pair of second markers M2a and M2b after the recording medium P has been transported a predetermined transport amount, but the order in which the first marker M1 and the second markers M2a and M2b are formed may be either. For example, the pattern forming unit 111 may form a pair of second markers M2a and M2b on the recording medium P, and then form the first marker M1 after the recording medium P has been transported a predetermined transport amount. In this embodiment, the pattern forming unit 111 forms the test pattern TP using three recording heads 6A, 6B, and 6C, but it is also possible to form the test pattern TP using one or more recording heads 6 having a plurality of nozzles arranged in the sub-scanning direction.

[0072] Here, the test pattern TP will be described. FIG. 15 is a diagram showing an example of a test pattern formed on a recording medium by an image forming apparatus according to this embodiment. As shown in FIG. 15, the test pattern TP is composed of a set of markers M including at least a first marker M1 and a pair of second markers M2a and M2b. In the test pattern TP shown in FIG. 15, the first marker M1 is positioned midway between the pair of second markers M2a and M2b. The first marker M1 and the pair of second markers M2a and M2b are formed of dots and are formed along the sub-scanning direction (the direction of arrow B in the figure), which is the transport direction of the recording medium P. That is, in this embodiment, the first marker M1 is an example of a reference adjustment pattern printed on the recording medium P using any nozzle (an example of a reference nozzle) among the nozzles of the recording head 6. In addition, the second markers M2a and M2b are examples of adjustment patterns that are printed by a nozzle (an example of a designated nozzle) that is a predetermined distance away from the reference nozzle in the sub-scanning direction when the recording medium P is transported a predetermined amount in the sub-scanning direction from the reference nozzle.

[0073] Returning to FIG. 14, position detection unit 142 is an example of a detection unit that detects first marker M1 and second marker M2 included in test pattern TP from an image captured by two-dimensional sensor 27.

[0074] The calculation unit 114 is an example of a calculation unit that calculates the distance between the first marker M1 and the second marker M2 in the sub-scanning direction based on the detection results of the first marker M1 and the second marker M2 by the position detection unit 142. The determination unit 115 is an example of a determination unit that determines whether the standard deviation (an example of variation) of the distance calculated by the calculation unit 114 is equal to or greater than a predetermined value. If the standard deviation is equal to or greater than the predetermined value, the determination unit 115 may determine that there is a deviation in the liquid ejection from the reference nozzle or the designated nozzle. This makes it possible to determine whether there is a deviation in the ink ejection from the reference nozzle or the designated nozzle, thereby enabling highly accurate detection of the amount of image misalignment. Furthermore, the determination unit 115 functions as an example of a notification unit that notifies the user that the standard deviation is equal to or greater than the predetermined value when it is determined that the standard deviation is equal to or greater than the predetermined value. Alternatively, if the determination unit 115 determines that the standard deviation is equal to or greater than the predetermined value and there is a deviation in the ink ejection from the reference nozzle or the designated nozzle, it may notify the user that there is a deviation in the ink ejection from the reference nozzle or the designated nozzle.

[0075] Next, a method for forming the test pattern TP will be described. FIGS. 16 to 20 are explanatory diagrams of an example of a method for forming a test pattern in the image forming apparatus according to this embodiment. First, as shown in FIG. 16(a), the pattern forming unit 111 forms a first marker M1 on the recording medium P. Next, as shown in FIG. 16(b), the conveyance control unit 116 causes the conveyance roller 152 to convey the recording medium P in the sub-scanning direction (the direction of arrow B in the figure) a predetermined conveyance amount L1 (actual conveyance amount L1). After conveying the recording medium P in the sub-scanning direction by the predetermined conveyance amount L1, the pattern forming unit 111 forms second markers M2a and M2b. This pair of second markers M2a and M2b is formed by two nozzles (an example of designated nozzles) spaced a predetermined distance e on both the front and rear sides in the sub-scanning direction, based on a nozzle spaced the ideal conveyance amount L1 from the nozzle that formed the first marker M1. In the following description, this reference nozzle will be referred to as the reference nozzle, and the two nozzles that are spaced a predetermined distance e from the reference nozzle on both sides in the sub-scanning direction will be referred to as designated nozzles.

[0076] Therefore, if the actual transport amount L1 and the ideal transport amount L1 are the same, a test pattern TP is formed in which the first marker M1 is formed at the ideal position, which is the midpoint in the sub-scanning direction between the pair of second markers M2a, M2b. On the other hand, if the actual transport amount L1 and the ideal transport amount L1 are different, a test pattern TP is formed in which the first marker M1 is formed at a position close to either of the pair of second markers M2a, M2b, for example.

[0077] Then, the test pattern TP is imaged by the imaging unit 20, and the relative positional relationship between the first marker M1 and the pair of second markers M2a, M2b is calculated to determine the amount of deviation between the actual transport amount L1 and the ideal transport amount L1. Note that, in this embodiment, an example is described in which the ideal position of the first marker M1 is the intermediate position between the pair of second markers M2a, M2b, but it does not have to be the intermediate position between the pair of second markers M2a, M2b. In other words, as long as the first marker M1 can be imaged together with the pair of second markers M2a, M2b and is formed at a predetermined position, the ideal position of the first marker M1 may be a position close to either one of the pair of second markers M2a, M2b, and does not have to be between the pair of second markers M2a, M2b.

[0078] An example of use in an actual machine will be described. When the user selects a specific type when setting the type of recording medium P on the printing device main body, the CPU 110, which controls the entire image forming device 100, outputs a test pattern TP to the pattern forming unit 111 in accordance with the method for forming the test pattern TP explained in Fig. 16. The first markers M1, M1', M1'', and M1''' are formed by the 6Ak nozzle array arranged in the recording head 6A located upstream in the transport direction of the recording medium P (see Fig. 17).

[0079] The first markers M1, M1', M1'', M1''' formed on the recording medium P are transported intermittently over a transport distance (transport amount) L1 N1 times to the position of the recording head 6C, and then a pair of second markers M2a, M2a', M2a'', M2a''', M2b, M2b', M2b''', M2b''', and a frame line F are formed. The nozzles used to form pairs of second markers M2a, M2a', M2a'', M2a''', M2b, M2b', M2b''', M2b''' are nozzles that are equidistant (predetermined distance) e from the first markers M1, M1', M1'', M1''' when the first markers M1, M1', M1'', M1''' are transported over the ideal transport distance (transport amount) L1 (see Figure 18).

[0080] The recording head 6C forms pairs of second markers M2a, M2a', M2a", M2a'", M2b, M2b', M2b", and M2b'" and a frame line F to complete the test pattern TP, and then conveys the test pattern TP a distance L4 to move the test pattern TP to an imageable area of ​​the imaging unit 20. That is, the pattern forming unit 111 prints the test pattern TP, which includes a plurality of first markers M1, M1', M1", and M1'", and second markers M2a, M2a', M2a", M2a'", M2b, M2b', M2b", and M2b'", that are positioned differently in the main scanning direction, on the recording medium P. Then, after the test pattern TP has moved to the imageable area of ​​the imaging unit 20, the imaging unit 20 captures an image of the test pattern TP. Furthermore, the position detection unit 142 detects first markers M1, M1', M1", and M1'" and pairs of second markers M2a, M2a', M2a", M2a'", M2b, M2b', M2b", and M2b'" included in the captured test pattern TP. Next, the calculation unit 114 calculates the relative positional relationship between the first markers M1, M1', M1", and M1'" and the pairs of second markers M2a, M2a', M2a", M2a'", M2b, M2b', M2b", and M2b'" (see FIG. 19).

[0081] Specifically, as shown in FIG. 20, the calculation unit 114 calculates distances a, a', a'', a''', a''', b, b', b''', b''' between first markers M1, M1', M1'', M1''' and pairs of second markers M2a, M2a', M2a'', M2a''', M2b, M2b', M2b'', M2b''' as relative positional relationships. In this case, the determination unit 115 calculates the standard deviation of the distances a, a', a'', a''', a''' (or distances b, b', b'', b''') and determines whether the standard deviation is equal to or greater than a preset value (an example of a predetermined value). If the standard deviation is equal to or greater than the preset value, the determination unit 115 determines that there is a curve in the ink ejection from the reference nozzle or the designated nozzle. If it is determined that the standard deviation is equal to or greater than a preset value, or if it is determined that there is a deflection in the ink ejection, the determination unit 115 notifies the user, via the operation screen of the image forming apparatus 100, that the standard deviation is equal to or greater than a preset value, or that there is a deflection in the ink ejection. Alternatively, it is possible to perform nozzle cleaning of the print head, and the pattern forming unit 111 to print and detect the test pattern TP again. However, if the entire recording head 6 is tilted, or if all the nozzles printing the test pattern TP are deflecting the ink ejection in the same direction, it is not possible to detect the deflection in the ink ejection.

[0082] In this embodiment, the test pattern TP is drawn as a total of four patterns, including first markers M1, M1', M1'', and M1''', and pairs of second markers M2a, M2a', M2a'', M2a''', M2b, M2b', M2b''', and M2b''', but this does not have to be four. Also, although black ink is used to form the first markers M1, M1', M1'', and M1''' and pairs of second markers M2a, M2a', M2a'', M2a''', M2b, M2b', M2b''', and M2b''', of the test pattern TP, ink of another color may be used. Also, different colors may be used for the first markers M1, M1', M1'', and M1''' and the pairs of second markers M2a, M2a', M2a'', M2a''', M2b, M2b', M2b'', and M2b'''.

[0083] In this way, according to the image forming apparatus 100 of this embodiment, it is possible to determine whether or not there is a deviation in the ink ejection from the reference nozzle or the designated nozzle, and therefore it is possible to detect the amount of image misalignment with high accuracy.

[0084] The program executed by image forming apparatus 100 of this embodiment is provided by being pre-installed in ROM 102 or the like. The program executed by image forming apparatus 100 of this embodiment may be provided by being recorded in an installable or executable file format on a computer-readable recording medium such as a CD-ROM, a flexible disk (FD), a CD-R, or a digital versatile disk (DVD).

[0085] Furthermore, the program executed by image forming apparatus 100 of the present embodiment may be stored on a computer connected to a network such as the Internet and provided by being downloaded via the network. Also, the program executed by image forming apparatus 100 of the present embodiment may be provided or distributed via a network such as the Internet.

[0086] The program executed by the image forming apparatus 100 of this embodiment has a modular configuration including the above-mentioned units (pattern forming unit 111, calculation unit 114, judgment unit 115, conveyance control unit 116, and position detection unit 142), and in terms of actual hardware, the CPU 110 or the CPU 140 for the two-dimensional sensor (an example of a processor) reads and executes the program from the ROM 102 or the like, thereby loading the above-mentioned units onto the main memory, and the pattern forming unit 111, calculation unit 114, judgment unit 115, conveyance control unit 116, and position detection unit 142 are generated on the main memory.

[0087] In the above embodiment, the image forming apparatus of the present invention is described as being applied to a multifunction peripheral having at least two of the functions of a copy function, a printer function, a scanner function, and a facsimile function, but the present invention can be applied to any image forming apparatus such as a copier, printer, scanner device, or facsimile device. [Explanation of symbols]

[0088] 6 recording head 20 Imaging unit 27 Two-dimensional sensor 100 Image forming device 102 ROM 103 RAM 110 CPU 111 Pattern forming section 114 Calculation Unit 115 Judgment Department 116 Transport control unit 120 Control FPGA 140 CPU for two-dimensional sensor 142 Position detection unit 150 Conveyor [Prior art documents] [Patent documents]

[0089] [Patent Document 1] Japanese Patent Application Publication No. 2018-083334

Claims

1. a recording head having a plurality of nozzles; a printing unit that prints a reference adjustment pattern on a recording medium using a reference nozzle among the plurality of nozzles, and when the recording medium is transported a predetermined transport amount in a sub-scanning direction from the reference nozzle, prints an adjustment pattern on the recording medium using a designated nozzle that is a nozzle that is a predetermined distance away from the reference nozzle in the sub-scanning direction, using the nozzle that is the predetermined transport amount away from the reference nozzle as a reference; a detection unit that detects the reference adjustment pattern and the adjustment pattern; a calculation unit that calculates the distance between the reference adjustment pattern and the adjustment pattern in the sub-scanning direction; a determination unit that determines whether the standard deviation of the distances calculated by the calculation unit is equal to or greater than a predetermined value; An image forming apparatus comprising:

2. 2. The image forming apparatus according to claim 1, wherein the printing unit prints the adjustment pattern on the recording medium using the designated nozzles located a predetermined distance away from the reference nozzle in the sub-scanning direction on both sides of the reference nozzle.

3. 3. The image forming apparatus according to claim 1, wherein the printing unit prints a plurality of the reference adjustment patterns and the adjustment patterns at different positions in the main scanning direction on the recording medium.

4. The image forming apparatus according to claim 1 , further comprising a notification unit that, when it is determined that the standard deviation is equal to or greater than the predetermined value, notifies the user that the standard deviation is equal to or greater than the predetermined value.

5. 4. The image forming apparatus according to claim 1, wherein the printing unit prints the reference adjustment pattern and the adjustment pattern again when it is determined that the liquid ejected from the reference nozzle or the designated nozzle is deflected.

6. An image forming method executed by an image forming apparatus, a step in which a printing unit prints a reference adjustment pattern on a recording medium using a reference nozzle among a plurality of nozzles of a recording head, and when the recording medium is transported a predetermined transport amount in a sub-scanning direction from the reference nozzle, prints an adjustment pattern on the recording medium using a designated nozzle that is a nozzle that is a predetermined distance away from the nozzle that is the predetermined transport amount away from the reference nozzle in the sub-scanning direction; a step in which a detection unit detects the reference adjustment pattern and the adjustment pattern; a calculation unit calculating the distance between the reference adjustment pattern and the adjustment pattern in the sub-scanning direction; a step in which a determination unit determines whether or not a standard deviation of the calculated distances is equal to or greater than a predetermined value; An image forming method comprising:

7. Computer, a printing unit that prints a reference adjustment pattern on a recording medium using a reference nozzle among a plurality of nozzles of a recording head, and when the recording medium is transported a predetermined transport amount in a sub-scanning direction from the reference nozzle, prints an adjustment pattern on the recording medium using a designated nozzle that is a nozzle that is a predetermined distance away from the reference nozzle in the sub-scanning direction, based on the nozzle that is the predetermined transport amount away from the reference nozzle; a detection unit that detects the reference adjustment pattern and the adjustment pattern; a calculation unit that calculates the distance between the reference adjustment pattern and the adjustment pattern in the sub-scanning direction; a determination unit that determines whether the standard deviation of the distances calculated by the calculation unit is equal to or greater than a predetermined value; A program to make it function as such.

Images