JP2016060066A - Nozzle inspection device, image forming device, and nozzle inspection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately inspect the discharge failure of a nozzle for discharging color ink and the discharge failure of a nozzle for discharging clear ink or white ink.SOLUTION: The nozzle inspection device includes a light source part for illuminating an object region so that the image Im of the object region captured by a two-dimensional image sensor can include a specular reflection region R1 and a diffuse reflection region R2. The two-dimensional image sensor captures the image Im of the object region so that a first pattern P1 formed by color ink can be positioned in the diffuse reflection region R2, and a second pattern P2 formed by clean ink or white ink can be positioned in the specular reflection region R1. A detection part analyzes the specular reflection region R1 of the image Im of the object region to inspect the discharge failure of a nozzle for discharging the clear ink or the white ink, and analyzes the diffuse reflection region R2 of the image Im of the object region to inspect the discharge failure of a nozzle for discharging the color ink.SELECTED DRAWING: Figure 8

Description

  The present invention relates to a nozzle inspection apparatus, an image forming apparatus, and a nozzle inspection method.

  In an ink jet printer that performs printing by ejecting ink onto a recording medium, if an ejection failure occurs due to clogging of a nozzle that ejects ink, the image quality of a printed image is degraded. Therefore, ink is actually ejected from the nozzles onto the recording medium to form a test pattern for inspection. The test pattern is used to inspect nozzle ejection defects, and if a ejection defect is detected, nozzle maintenance or the like is performed. It is known.

  For example, Patent Document 1 describes a technique for inspecting ejection failure of a nozzle that ejects clear ink in addition to a nozzle that ejects color ink. In the technique described in Patent Document 1, two sensors are used for diffuse reflection detection and regular reflection detection. When a test pattern is to be formed on plain paper, a test pattern in which color ink is superimposed on clear ink is formed, and the ejection failure of nozzles that eject clear ink is inspected based on the diffuse reflected light in this test pattern. To do. On the other hand, when a test pattern is formed on glossy paper, the test pattern is formed only with clear ink, and the ejection failure of the nozzle that ejects the clear ink is inspected based on the regular reflection light in this test pattern.

  However, in the technique described in Patent Document 1, it is necessary to separately provide a sensor that detects diffusely reflected light and a sensor that receives specularly reflected light, and to place these two sensors at appropriate positions in the apparatus. There is a disadvantage that the degree of freedom in layout is reduced.

  In order to solve the above-described problem, the present invention provides a two-dimensional image sensor that captures a predetermined imaging range including a pattern formed by ejecting ink onto a recording medium from a nozzle row including a plurality of nozzles; The imaging range so that an image of the imaging range captured by the two-dimensional image sensor includes a regular reflection region that is an image region based on specular reflection light and a diffuse reflection region that is an image region based on diffuse reflection light. A light source unit that illuminates a light source and a detection unit that detects an ejection failure of the nozzle by analyzing an image in the imaging range, and the two-dimensional image sensor includes a first pattern in which the pattern is formed of color ink The first pattern is positioned in the diffuse reflection region, and the second pattern is formed when the pattern is a second pattern formed of clear ink or white ink. When the pattern is the first pattern, the detection unit analyzes the diffuse reflection area to form the first pattern so that the image is located in the regular reflection area. The ejection failure of the nozzle is inspected, and when the pattern is the second pattern, the regular reflection area is analyzed to inspect the ejection failure of the nozzle on which the second pattern is formed.

  According to the present invention, with a simple configuration, the ejection failure of the nozzle that ejects the color ink and the ejection failure of the nozzle that ejects the ink whose visibility is lowered after being ejected to the recording medium such as the clear ink and the white ink are appropriately performed. There is an effect that it can be inspected.

FIG. 1 is a perspective view illustrating the inside of the image forming apparatus. FIG. 2 is a top view showing an internal mechanical configuration of the image forming apparatus. FIG. 3 is a plan view of the recording head as viewed from the ink ejection surface side. FIG. 4A is a longitudinal sectional view of the colorimetric camera. FIG. 4B is a plan view of the inside of the color measurement camera housing as viewed in the X1 direction of FIG. 4A. FIG. 5 is a diagram illustrating a specific example of the reference chart. FIG. 6 is a block diagram illustrating a schematic configuration of a control mechanism of the image forming apparatus. FIG. 7 is a block diagram illustrating a configuration example of the control mechanism of the colorimetric camera. FIG. 8 is a diagram schematically showing an image of the subject area captured by the two-dimensional image sensor. FIG. 9 is a diagram illustrating an example of processing by the detection unit. FIG. 10 is a diagram illustrating an example of processing by the detection unit. FIG. 11 is a flowchart illustrating an example of the operation of the colorimetric camera. FIG. 12 is a diagram illustrating a modification of the colorimetric camera.

  Hereinafter, a nozzle inspection apparatus, an image forming apparatus, and a nozzle inspection method according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. The following embodiment is mounted on an image forming apparatus configured as an ink jet printer, and has a function of calculating a colorimetric value by capturing an image of a colorimetric pattern formed on a recording medium by the image forming apparatus. This is an example in which the colorimetric camera is provided with a function as a nozzle inspection device of the present invention.

<Mechanical configuration of image forming apparatus>
First, the mechanical configuration of the image forming apparatus 100 of the present embodiment will be described with reference to FIGS. 1 to 3. 1 is a perspective view showing the inside of the image forming apparatus 100 as seen through, FIG. 2 is a top view showing the mechanical configuration inside the image forming apparatus 100, and FIG. 3 is a recording head 6 mounted on the carriage 5. FIG. 6 is a plan view when viewed from the ink ejection surface side.

  As shown in FIG. 1, the image forming apparatus 100 of the present embodiment includes a carriage 5 that reciprocates in the main scanning direction (the direction of arrow A in the figure). The carriage 5 is supported by a main guide rod 3 extending along the main scanning direction. The carriage 5 is provided with a connecting piece 5a. The connecting piece 5 a engages with the sub guide member 4 provided in parallel with the main guide rod 3 to stabilize the posture of the carriage 5.

  As shown in FIG. 2, for example, five recording heads 6y, 6m, 6c, 6k, and 6cl are mounted on the carriage 5. The recording head 6y is a recording head that discharges yellow ink. The recording head 6m is a recording head that discharges magenta ink. The recording head 6c is a recording head that discharges cyan ink. The recording head 6k is a recording head that discharges black ink. The recording head 6cl is a recording head that discharges clear ink. Hereinafter, the recording heads 6y, 6m, 6c, 6k, and 6cl are collectively referred to as the recording head 6. The recording head 6 is supported by the carriage 5 so that the ink ejection surface (nozzle surface) faces downward (recording medium M side).

  A cartridge 7, which is an ink supply body for supplying ink to the recording head 6, is not mounted on the carriage 5 and is disposed at a predetermined position in the image forming apparatus 100. The cartridge 7 and the recording head 6 are connected by a pipe (not shown), and ink is supplied from the cartridge 7 to the recording head 6 through this pipe.

  The carriage 5 is connected to a timing belt 11 stretched between a driving pulley 9 and a driven pulley 10. The drive pulley 9 is rotated by driving the main scanning motor 8. The driven pulley 10 has a mechanism for adjusting the distance to the driving pulley 9 and has a role of applying a predetermined tension to the timing belt 11. The carriage 5 reciprocates in the main scanning direction when the timing belt 11 is fed by driving the main scanning motor 8. The movement of the carriage 5 in the main scanning direction is controlled based on an encoder value obtained when the encoder sensor 13 provided on the carriage 5 detects a mark on the encoder sheet 14 as shown in FIG.

  In addition, the image forming apparatus 100 according to the present embodiment includes a maintenance mechanism 15 for maintaining the reliability of the recording head 6. The maintenance mechanism 15 performs cleaning and capping of the ejection surface of the recording head 6 and discharging unnecessary ink from the recording head 6. In this embodiment, when a discharge failure is detected at the nozzles of the recording head 6, the maintenance mechanism 15 performs recovery operations such as wiping of the discharge surface and empty ink discharge to eliminate the discharge failure.

  A platen 16 is provided at a position facing the ink discharge surface of the recording head 6 as shown in FIG. The platen 16 is for supporting the recording medium M when ink is ejected from the recording head 6 onto the recording medium M. The image forming apparatus 100 according to the present embodiment is a wide-width machine in which the moving distance of the carriage 5 in the main scanning direction is long. For this reason, the platen 16 is configured by connecting a plurality of plate-like members in the main scanning direction (movement direction of the carriage 5). The recording medium M is nipped by a conveyance roller driven by a sub scanning motor (not shown), and is intermittently conveyed on the platen 16 in the sub scanning direction (direction perpendicular to the main scanning direction) indicated by an arrow B in the drawing. .

  As shown in FIG. 3, the recording head 6 has a nozzle row 17 in which a plurality of nozzles are arranged along the sub-scanning direction (the direction of arrow B in the figure). As the carriage 5 reciprocates in the main scanning direction (the direction of arrow A in the figure), the recording head 6 moves from the nozzle row 17 to the ink while moving relative to the recording medium M on the platen 16 in the main scanning direction. Are ejected to form an image on the recording medium M. In the recording head 6 shown in FIG. 3, two nozzle rows 17 are provided. One nozzle row 17 is formed such that each nozzle is positioned approximately ½ · p away from the other nozzle row 17 in the sub-scanning direction. Thereby, an image with high resolution in the sub-scanning direction can be formed.

  Each of the above-described constituent elements constituting the image forming apparatus 100 of the present embodiment is disposed inside the exterior body 1. The exterior body 1 is provided with a cover member 2 that can be opened and closed. At the time of maintenance of the image forming apparatus 100 or when a jam occurs, the cover member 2 can be opened to perform work on each component provided inside the exterior body 1.

  The image forming apparatus 100 according to the present embodiment forms a large number of colorimetric patterns by ejecting ink from the nozzle row 17 of the recording head 6 onto the recording medium M on the platen 16 during color adjustment. Then, the colorimetry of this colorimetric pattern is performed. The color measurement pattern is what the image forming apparatus 100 actually forms on the recording medium M using ink, and reflects the characteristic unique to the image forming apparatus 100. Therefore, a device profile describing characteristics unique to the image forming apparatus 100 can be generated or modified using the colorimetric values of a large number of colorimetric patterns. Then, by performing color conversion between the standard color space and the device-dependent color based on this device profile, the image forming apparatus 100 can output an image with high reproducibility.

  The image forming apparatus 100 according to this embodiment includes a colorimetric camera 20 having a function of capturing a colorimetric pattern image formed on a recording medium M and calculating a colorimetric value. As shown in FIG. 2, the colorimetric camera 20 is supported by a carriage 5 on which the recording head 6 is mounted. When the colorimetric camera 20 moves on the recording medium M on which the colorimetric pattern is formed by transporting the recording medium M and moving the carriage 5 and comes to a position facing the colorimetric pattern, the image is displayed. Image. Then, based on the RGB value of the color measurement pattern obtained by imaging, the color measurement value of the color measurement pattern is calculated.

  Further, in the image forming apparatus 100 of the present embodiment, the colorimetric camera 20 is used to inspect whether or not ejection failure has occurred in the nozzles of the recording head 6. When inspecting nozzle ejection defects in the recording head 6, a test pattern formed by using each of the recording heads 6 y, 6 m, 6 c, 6 k, and 6 cl independently (hereinafter, “inspection is distinguished from a colorimetric pattern”). The color measurement camera 20 performs imaging using the “use pattern”) as a subject. At this time, a light source unit 31 described later is used for illumination of the inspection pattern. The light source unit 31 is an illumination unit that illuminates the captured image so that the regular reflection region and the diffuse reflection region are included. The regular reflection area is an image area based on regular reflection light from a subject, and is an area in an image formed when a two-dimensional image sensor 25 described later receives regular reflection light. The diffuse reflection area is an image area based on diffuse reflection light from a subject, and is an area (an area other than the regular reflection area) in an image formed by the two-dimensional image sensor 25 receiving diffuse reflection light.

  The colorimetric camera 20 is formed by using these recording heads 6y, 6m, 6c, and 6k independently when inspecting nozzle ejection defects in the recording heads 6y, 6m, 6c, and 6k that eject color inks. An image is picked up so that an inspection pattern made of single color ink (hereinafter, an inspection pattern made of color ink is particularly referred to as a “first pattern”) enters the diffuse reflection region. Then, color ink is ejected by analyzing the diffuse reflection area in the image and detecting a defect line which is a high luminance (low density) streak defect generated in the image of the first pattern located in the diffuse reflection area. The nozzles in the recording heads 6y, 6m, 6c, and 6k are inspected for defective ejection.

  On the other hand, when inspecting nozzle ejection defects in the recording head 6cl that ejects clear ink, an inspection pattern made of clear ink (hereinafter referred to as an inspection pattern made of clear ink) is formed using the recording head 6cl. An image is picked up so that “second pattern”) enters the regular reflection region. Then, the recording head 6cl that discharges clear ink is analyzed by analyzing the regular reflection area in the image and detecting a defect line that is a low-brightness streak defect generated in the image of the second pattern located in the regular reflection area. The nozzle is inspected for defective discharge.

  In the case of simultaneously inspecting the nozzle ejection failure in the recording heads 6y, 6m, 6c, and 6k that ejects color ink and the nozzle ejection failure in the recording head 6cl that ejects clear ink, the colorimetric camera 20 is the first one. An image is picked up so that the pattern enters the diffuse reflection region and the second pattern enters the regular reflection region. Then, by detecting the defective line by analyzing the diffuse reflection area, the nozzles in the recording heads 6y, 6m, 6c, and 6k that discharge colored ink are inspected for defective ejection, and the regular reflection area is analyzed to detect the defective line. By detecting this, the ejection failure of the nozzles in the recording head 6cl that ejects clear ink is inspected.

<Specific examples of colorimetric cameras>
Next, a specific example of the colorimetric camera 20 will be described in detail with reference to FIGS. 4A and 4B. 4A and 4B are diagrams illustrating an example of the mechanical configuration of the colorimetric camera 20, and FIG. 4A is a longitudinal sectional view of the colorimetric camera 20 (X2- in FIG. 4B). FIG. 4B is a plan view of the inside of the housing 23 of the colorimetric camera 20 as viewed in the X1 direction of FIG. 4A. In FIG. 4B, in order to show the positional relationship between the members disposed inside the housing 23 of the colorimetric camera 20, the illustration of the structure that supports these members is omitted as appropriate. ing.

  The colorimetric camera 20 includes a housing 23 configured by combining a frame body 21 and a substrate 22. The frame body 21 is formed in a bottomed cylindrical shape in which one end side which is the upper surface of the housing 23 is opened. The substrate 22 is fastened to the frame body 21 so as to close the open end of the frame body 21 and constitute the upper surface of the housing 23, and is integrated with the frame body 21.

  The housing 23 is fixed to the carriage 5 so that the bottom surface portion 23a faces the recording medium M on the platen 16 with a predetermined gap d. An opening 24 for allowing a pattern (color measurement pattern or inspection pattern) formed on the recording medium M to be photographed from the inside of the casing 23 is formed in the bottom surface portion 23 a of the casing 23 facing the recording medium M. Is provided.

  A two-dimensional image sensor 25 that captures an image is provided inside the housing 23. The two-dimensional image sensor 25 includes an imaging element such as a CCD sensor or a CMOS sensor, an imaging lens, and the like, and for example, the inner surface side (component mounting surface) of the substrate 22 so that the light receiving surface faces the bottom surface portion 23a side of the housing 23. ) Is implemented.

  Further, inside the housing 23, a reference chart 40 imaged together with the colorimetric pattern by the two-dimensional image sensor 25 when performing colorimetry of the colorimetric pattern, and an optical image of the reference chart 40 are two-dimensionally displayed. A reflection mirror 26 for guiding the image sensor 25 is provided. For example, the reference chart 40 is pressed against the structure by a compression restoring force of the buffer member 27 and is fixed and arranged in a state of being parallel to the side surface of the frame body 21. The reflection mirror 26 is pressed against the structure by, for example, the compression restoring force of the buffer member 28 and is fixed and arranged in a state inclined at a predetermined angle with respect to the bottom surface portion 23 a of the housing 23. Details of the reference chart 40 will be described later.

  In addition, a colorimetric light source 30 for illuminating the imaging range of the two-dimensional image sensor 25 substantially uniformly with diffused light is provided inside the housing 23 when performing colorimetry of the colorimetric pattern. (See FIG. 4-2). As the colorimetric light source 30, for example, an LED (Light Emitting Diode) is used. The colorimetric light source 30 is mounted on the inner surface side of the substrate 22, for example. However, the colorimetric light source 30 is only required to be disposed at a position where the imaging range of the two-dimensional image sensor 25 can be illuminated almost uniformly, and is not necessarily mounted directly on the substrate 22. In this embodiment, an LED is used as the colorimetric light source 30, but the type of the light source is not limited to the LED. For example, an organic EL or the like may be used as the colorimetric light source 30. When the organic EL is used as the colorimetric light source 30, illumination light close to the spectral distribution of sunlight can be obtained, so that improvement in colorimetric accuracy can be expected.

  In addition, a light source unit 31 that illuminates an imaging range including an inspection pattern formed on the recording medium M when the nozzle 23 in the recording head 6 is inspected for defective ejection is provided inside the housing 23. The light source unit 31 is an image captured by the two-dimensional image sensor 25 using the test pattern as a subject, in particular, a range captured through the opening 24 of the housing 23 (hereinafter referred to as “subject region”). The periphery of the opening 24 is illuminated so that the image includes the above-described regular reflection area and diffuse reflection area.

  In the colorimetric camera 20 of this embodiment, in the image of the subject area captured by the two-dimensional image sensor 25, the regular reflection area is in the relative movement direction of the recording head 6 and the recording medium M when forming the inspection pattern. It is formed so as to be longer in a direction corresponding to a certain main scanning direction (arrow A direction in the figure). In other words, the light source unit 31 reflects the object region image captured by the two-dimensional image sensor 25 in a shape that is longer in the direction corresponding to the main scanning direction than in the direction corresponding to the sub-scanning direction. A region is configured to be formed. In the following description, for convenience of explanation, a direction corresponding to the main scanning direction in the inspection pattern image is simply referred to as a main scanning direction, and a direction corresponding to the sub scanning direction in the inspection pattern image is simply referred to as a sub scanning direction.

  For example, as illustrated in FIG. 4B, the light source unit 31 includes a plurality of inspection light sources 32 arranged inside the housing 23 so as to be linearly arranged along the main scanning direction (the arrow A direction in the drawing). It is set as the structure which has. For example, an LED is used as the inspection light source 32. Since the colorimetric camera 20 is fixed to the carriage 5 on which the recording head 6 is mounted, the direction in which the plurality of inspection light sources 32 are arranged and the relative movement between the recording head 6 and the recording medium M when forming the inspection pattern. The direction matches. Therefore, in the image of the subject area captured by the two-dimensional image sensor 25, a regular reflection area in which the regular reflection light from the plurality of inspection light sources 32 is arranged in the main scanning direction is formed.

  The light source unit 31 only needs to have a configuration in which a regular reflection region that is longer in the main scanning direction than in the sub-scanning direction is formed in the image of the subject region captured by the two-dimensional image sensor 25. You may be comprised from the single light source for a test | inspection which forms a long strip | belt-shaped regular reflection area | region.

  In addition, ink mist, dust, or the like that enters the inside of the housing 23 through the opening 24 is inside the housing 23, the two-dimensional image sensor 25, the colorimetric light source 30, the inspection light source 32 of the light source unit 31, the reference A cover member 33 for preventing adhesion to the chart 40 or the like is provided. The cover member 33 is a transparent optical member having a sufficient transmittance with respect to light from the colorimetric light source 30 and the inspection light source 32 of the light source unit 31, and is disposed inside the housing 23 in parallel with the opening 24. Has been.

  The cover member 33 is disposed in the optical path of light emitted from the inspection light source 32 of the light source unit 31 to the subject area. For this reason, the light from the inspection light source 32 is regularly reflected not only by the subject region but also by the cover member 33. When the specularly reflected light from the cover member 33 is incident on the two-dimensional image sensor 25, there is a possibility that the inspection of the nozzle ejection failure of the recording head 6 is adversely affected. For this reason, a light shielding member 34 is further provided inside the housing 23 to block the regular reflection light from the cover member 33 and prevent the light from entering the two-dimensional image sensor 25. For example, as shown in FIG. 4A, the light shielding member 34 is configured as a partition wall arranged perpendicular to the cover member 33.

  It should be noted that the specularly reflected light that is specularly reflected by the subject region is incident on the two-dimensional image sensor 25 and the specularly reflected light that is specularly reflected by the cover member 33 is not incident on the two-dimensional image sensor 25. In the case where the light source 32 can be arranged, the light blocking member 34 may not be provided.

  The colorimetric camera 20 of the present embodiment turns on the colorimetric light source 30 during colorimetry of the colorimetric pattern, and the colorimetric pattern formed on the recording medium M is illuminated by the colorimetric light source 30. The two-dimensional image sensor 25 takes an image. On the other hand, when the nozzle of the recording head 6 is inspected, the plurality of inspection light sources 32 of the light source unit 31 are turned on, and the inspection pattern formed on the recording medium M is illuminated by the inspection light source 32 under the two-dimensional image sensor 25. Take an image. Then, an image of a subject area captured using the inspection pattern as a subject is analyzed, and a nozzle ejection defect in the recording head 6 is detected.

<Specific examples of reference chart>
Next, the reference chart 40 arranged in the housing 23 of the colorimetric camera 20 will be described in detail with reference to FIG. FIG. 5 is a diagram illustrating a specific example of the reference chart 40.

  The reference chart 40 shown in FIG. 5 includes a plurality of reference patch rows 41 to 44 in which color measurement reference patches are arranged, a dot diameter measurement pattern row 46, a distance measurement line 45, and a chart position specifying marker 47. .

  The reference patch rows 41 to 44 include a reference patch row 41 in which YMCK primary color reference patches are arranged in gradation order, a reference patch row 42 in which RGB secondary color reference patches are arranged in gradation order, and a gray scale. The reference patch row 43 in which the reference patches are arranged in the order of gradation and the reference patch row 44 in which the reference patches of the tertiary colors are arranged. The dot diameter measurement pattern array 46 is a geometric shape measurement pattern array in which circular patterns of different sizes are arranged in order of size, and is used for measuring the dot diameter of an image formed on the recording medium M. it can.

  The distance measurement line 45 is formed as a rectangular frame surrounding the plurality of reference patch rows 41 to 44 and the dot diameter measurement pattern row 46. The chart position specifying markers 47 are provided at the positions of the four corners of the distance measuring line 45 and function as markers for specifying the positions of the respective reference patches. By specifying the distance measurement line 45 and the chart position specifying markers 47 at the four corners from the image of the reference chart 40 imaged by the two-dimensional image sensor 25, the position of the reference chart 40 and the position of each reference patch or pattern Can be specified.

  Each reference patch constituting the reference patch rows 41 to 44 for colorimetry is used as a color reference reflecting the imaging conditions of the colorimetric camera 20. The configuration of the colorimetric reference patch rows 41 to 44 arranged in the reference chart 40 is not limited to the example shown in FIG. 5, and any reference patch row can be applied. . For example, a reference patch that can specify a color range as wide as possible may be used, and the YMCK primary color reference patch row 41 and the grayscale reference patch row 43 are used in the image forming apparatus 100. It may be composed of patches of colorimetric values of ink. Further, the RGB secondary color reference patch row 42 may be composed of patches of colorimetric values that can be developed with ink used in the image forming apparatus 100, and further, colorimetric values such as Japan Color are used. A predetermined reference color chart may be used.

  In this embodiment, the reference chart 40 having the reference patch rows 41 to 44 having a general patch (color chart) shape is used. However, the reference chart 40 is not necessarily limited to such reference patch rows 41 to 44. It may not be the form which has. The reference chart 40 may have a configuration in which a plurality of colors that can be used for colorimetry are arranged so that their positions can be specified.

  In the colorimetric camera 20 of the present embodiment, the colorimetric pattern formed on the recording medium M by the two-dimensional image sensor 25 under illumination by the colorimetric light source 30 when performing colorimetry of the colorimetric pattern. And the reference chart 40 inside the housing 23 are imaged simultaneously. Then, the colorimetric value of the colorimetric pattern is calculated using the obtained image. At this time, the position and angle of the reflection mirror 26 are adjusted so that an image focused on both the color measurement pattern outside the housing 23 and the reference chart 40 inside the housing 23 can be taken. Here, simultaneous imaging means obtaining one frame of image data including the colorimetric pattern and the reference chart 40. That is, even if there is a time difference in data acquisition for each pixel, if the image data including the color measurement pattern and the reference chart 40 is acquired within one frame, the color measurement pattern and the reference chart 40 are simultaneously captured. become.

  The mechanical configuration of the colorimetric camera 20 described above is an example, and the present invention is not limited to this. The colorimetric camera 20 of the present embodiment only needs to be configured to perform colorimetry of a colorimetric pattern using at least the two-dimensional image sensor 25 and inspection of nozzle ejection defects of the recording head 6 using the inspection pattern. Various modifications and changes can be made to the above configuration.

  In this embodiment, the colorimetric camera 20 having the function of measuring the colorimetric pattern has a function as a nozzle inspection device. However, the nozzle inspection device is different from the colorimetric camera 20. The structure implement | achieved using this imaging device may be sufficient. In this case, an imaging device different from the colorimetric camera 20 includes a two-dimensional image sensor similar to the two-dimensional image sensor 25 described above and a light source unit corresponding to the light source unit 31 described above. Then, the inspection pattern is imaged by the two-dimensional image sensor under illumination by the light source unit, and the defective image is detected by analyzing the image of the subject region, thereby detecting the ejection failure of the nozzle of the recording head 6.

<Schematic configuration of control mechanism of image forming apparatus>
Next, the schematic configuration of the control mechanism of the image forming apparatus 100 of the present embodiment will be described with reference to FIG. FIG. 6 is a block diagram illustrating a schematic configuration of a control mechanism of the image forming apparatus 100.

  As shown in FIG. 6, the image forming apparatus 100 according to the present embodiment includes a CPU 101, a ROM 102, a RAM 103, a recording head driver 104, a main scanning driver 105, a sub scanning driver 106, a control FPGA (Field-Programmable Gate Array) 110, A recording head 6, a colorimetric camera 20, an encoder sensor 13, a main scanning motor 8, and a sub-scanning motor 12 are provided. The CPU 101, ROM 102, RAM 103, print head driver 104, main scanning driver 105, sub scanning driver 106, and control FPGA 110 are mounted on the main control board 120. The recording head 6, the encoder sensor 13, and the colorimetric camera 20 are mounted on the carriage 5 as described above.

  The CPU 101 governs overall control of the image forming apparatus 100. For example, the CPU 101 uses the RAM 103 as a work area, executes various control programs stored in the ROM 102, and outputs control commands for controlling various operations in the image forming apparatus 100.

  The recording head driver 104, the main scanning driver 105, and the sub scanning driver 106 are drivers for driving the recording head 6, the main scanning motor 8, and the sub scanning motor 12, respectively.

  The control FPGA 110 controls various operations in the image forming apparatus 100 in cooperation with the CPU 101. The control FPGA 110 includes, for example, a CPU control unit 111, a memory control unit 112, an ink ejection control unit 113, a sensor control unit 114, and a motor control unit 115 as functional components.

  The CPU control unit 111 communicates with the CPU 101 to transmit various information acquired by the control FPGA 110 to the CPU 101 and inputs a control command output from the CPU 101.

  The memory control unit 112 performs memory control for the CPU 101 to access the ROM 102 and the RAM 103.

  The ink discharge control unit 113 controls the operation of the print head driver 104 in accordance with a control command from the CPU 101, thereby controlling the discharge timing of ink from the print head 6 driven by the print head driver 104.

  The sensor control unit 114 performs processing on sensor signals such as encoder values output from the encoder sensor 13.

  The motor control unit 115 controls the main scanning motor 105 driven by the main scanning driver 105 by controlling the operation of the main scanning driver 105 in accordance with a control command from the CPU 101, and moves the carriage 5 in the main scanning direction. Control the movement of. In addition, the motor control unit 115 controls the sub-scanning motor 106 driven by the sub-scanning driver 106 by controlling the operation of the sub-scanning driver 106 in accordance with a control command from the CPU 101, and records on the platen 16. The movement of the medium M in the sub-scanning direction is controlled.

  Each of the above-described units is an example of a control function realized by the control FPGA 110, and various other control functions may be realized by the control FPGA 110. Moreover, the structure which implement | achieves all or one part of said control function with the program run by CPU101 or another general purpose CPU may be sufficient. Further, a configuration in which a part of the control function is realized by dedicated hardware such as another FPGA different from the control FPGA 110 or an ASIC (Application Specific Integrated Circuit) may be used.

  The recording head 6 is driven by a recording head driver 104 whose operation is controlled by the CPU 101 and the control FPGA 110 and ejects ink onto the recording medium M on the platen 16 to form an image.

As described above, the colorimetric camera 20 images the colorimetric pattern formed on the recording medium M together with the reference chart 40 at the time of color adjustment of the image forming apparatus 100, and RGB of the colorimetric pattern obtained from the captured image. based on the RGB values of each reference patch value and the reference chart 40, a color value in color measurement value (standard color space color measurement pattern, for example, ^L * ^a * ^{b *} in the color space ^L * ^{a *} b ^* value) is calculated. The colorimetric values of the colorimetric pattern calculated by the colorimetric camera 20 are sent to the CPU 101 via the control FPGA 110. As a specific method for calculating the colorimetric value of the colorimetric pattern, for example, a method disclosed in Japanese Patent Application Laid-Open No. 2013-05671 can be used.

  Further, the colorimetric camera 20 has a function of inspecting nozzle ejection defects in the recording head 6 as described above. When inspecting the ejection failure of the nozzles in the recording head 6, the colorimetric camera 20 is obtained by performing imaging using the inspection pattern as a subject by the two-dimensional image sensor 25 under illumination by the light source unit 31 as described above. By detecting the defective line by analyzing the image of the subject area, the ejection failure of the nozzle is detected. The inspection result of nozzle discharge failure is sent from the colorimetric camera 20 to the CPU 101 via the control FPGA 110.

  The encoder sensor 13 outputs an encoder value obtained by detecting the mark on the encoder sheet 14 to the control FPGA 110. This encoder value is sent from the control FPGA 110 to the CPU 101 and used, for example, to calculate the position and speed of the carriage 5. The CPU 101 generates and outputs a control command for controlling the main scanning motor 8 based on the position and speed of the carriage 5 calculated from the encoder value.

<Configuration of colorimetric camera control mechanism>
Next, the control mechanism of the colorimetric camera 20 will be specifically described with reference to FIG. FIG. 7 is a block diagram illustrating a configuration example of the control mechanism of the colorimetric camera 20.

  As shown in FIG. 7, the colorimetric camera 20 includes a timing signal generation unit 51, a frame memory 52, an averaging processing unit 53, a measurement unit, in addition to the above-described two-dimensional image sensor 25, colorimetric light source 30 and light source unit 31. A color calculation unit 54, a nonvolatile memory 55, a light source drive control unit 56, and a detection unit 57 are provided.

  The two-dimensional image sensor 25 converts light incident on the two-dimensional image sensor 25 into an electrical signal, and outputs image data obtained by imaging the imaging range. The two-dimensional image sensor 25 AD converts an analog signal obtained by photoelectric conversion into digital image data, and performs various types of image data conversion such as shading correction, white balance correction, γ correction, and image data format conversion. Built-in function to output after image processing. Various operating conditions of the two-dimensional image sensor 25 are set according to various setting signals from the CPU 101. Various image processing on the image data may be performed partly or entirely outside the two-dimensional image sensor 25.

  The timing signal generation unit 51 generates a timing signal for controlling the timing of starting imaging by the two-dimensional image sensor 25 and supplies the timing signal to the two-dimensional image sensor 25. In the present embodiment, imaging is performed by the two-dimensional image sensor 25 not only when the colorimetric pattern is measured, but also when the ejection failure of the nozzles in the recording head 6 is inspected. The timing signal generation unit 51 generates a timing signal for controlling the timing of the start of imaging by the two-dimensional image sensor 25 at the time of the color measurement of these color measurement patterns and the inspection of the nozzles of the recording head 6, and sends the timing signal to the two-dimensional image sensor 25. Supply.

  The frame memory 52 temporarily stores the image output from the two-dimensional image sensor 25.

  When performing colorimetry of the colorimetric pattern, the averaging processing unit 53 captures an area in which the colorimetric pattern is projected from an image captured by the two-dimensional image sensor 25 and temporarily stored in the frame memory 52. The color measurement target area set near the center and the area where each reference patch of the reference chart 40 is projected are extracted. Then, the averaging processing unit 53 averages the extracted image data of the color measurement target region, and outputs the obtained value to the color measurement calculation unit 54 as the RGB value of the color measurement pattern. Each of the image data of the projected area is averaged, and the obtained value is output to the colorimetric calculation unit 54 as RGB of each reference patch.

  The colorimetric calculation unit 54 determines the colorimetric value of the colorimetric pattern based on the RGB value of the colorimetric pattern obtained by the processing of the averaging processing unit 53 and the RGB value of each reference patch of the reference chart 40. Is calculated. The colorimetric values of the colorimetric pattern calculated by the colorimetric calculation unit 54 are sent to the CPU 101 on the main control board 120. Note that the colorimetric calculation unit 54 can calculate the colorimetric values of the colorimetric pattern by a method disclosed in, for example, Japanese Patent Application Laid-Open No. 2013-05671, and therefore the detailed description of the processing of the colorimetric calculation unit 54 is here Omitted.

  The nonvolatile memory 55 stores various data necessary for the colorimetric calculation unit 54 to calculate the colorimetric values of the colorimetric pattern.

  The light source drive control unit 56 generates a light source drive signal for driving the colorimetric light source 30 and the light source unit 31 (inspection light source 32) and supplies the light source drive signal to the colorimetric light source 30 and the light source unit 31. As described above, the colorimetric camera 20 of the present embodiment drives the colorimetric light source 30 during colorimetry of the colorimetric pattern, and drives the light source unit 31 during nozzle inspection of the recording head 6. The light source drive control unit 56 supplies a light source drive signal to the colorimetric light source 30 at the timing of driving the colorimetric light source 30, and supplies the light source drive signal to the light source unit 31 (inspection light source 32 at the timing of driving the light source unit 31. ).

  The detection unit 57 detects a subject area from an image captured by the two-dimensional image sensor 25 under illumination by the light source unit 31 and temporarily stored in the frame memory 52 when inspecting the ejection failure of the nozzles in the recording head 6. This image is extracted and the image of the subject area is analyzed to detect nozzle ejection defects.

  FIG. 8 is a diagram schematically illustrating an image Im of a subject area extracted from an image captured by the two-dimensional image sensor 25 at the time of nozzle inspection of the recording head 6. Since the colorimetric camera 20 of the present embodiment drives the light source unit 31 and picks up an image by the two-dimensional image sensor 25 at the time of nozzle inspection of the recording head 6, the image Im of the subject region is as shown in FIG. In addition, a regular reflection region R1 and a diffuse reflection region R2 other than the regular reflection region R1 are formed. As described above, the regular reflection region R1 is a direction corresponding to the direction of relative movement between the recording head 6 and the recording medium M when the inspection pattern is formed on the recording medium M (in the present embodiment, it is indicated by an arrow A in the figure). A long region along the main scanning direction) is formed in the image Im of the subject region.

  Here, when inspecting the nozzle ejection failure in the recording head 6cl that ejects clear ink, the two-dimensional image sensor 25 has the second pattern P2 formed by the recording head 6cl that ejects clear ink as described above. An image is captured so as to enter the regular reflection region R1. For this reason, when the recording head 6cl has a nozzle that has an ejection failure, a low-luminance defect line along the main scanning direction appears in the regular reflection region R1 of the image Im in the subject region. The detection unit 57 can detect the ejection failure of the nozzle in the recording head 6cl that ejects clear ink by analyzing the regular reflection region R1 of the image Im of the subject region and detecting such a defective line.

  For example, the detection unit 57 first extracts the image Im of the subject area from the captured image of the two-dimensional image sensor 25 temporarily stored in the frame memory 52. Then, the detection unit 57 adds and averages the pixel values of each pixel included in the regular reflection region R1 of the extracted image of the subject region Im in the main scanning direction, and approximates the pixel average value for each sub-scanning position with an approximate curve. . Then, the detection unit 57 compares the difference (residual) between the pixel average value for each sub-scanning position and the approximate curve with a predetermined threshold, and if there is a position where the residual exceeds the threshold, the nozzle at that position It is determined that a discharge failure has occurred.

  FIG. 9 is a diagram illustrating an example of processing performed by the detection unit 57 when inspecting nozzle ejection defects in the recording head 6cl. FIG. 9A shows an example in which the pixel values of each pixel included in the regular reflection region R1 are averaged in the main scanning direction, and the pixel average value (solid line) for each sub-scanning position is approximated by an approximate curve (dashed line). The vertical axis represents the average pixel value in the main scanning direction, and the horizontal axis represents the sub-scanning position. FIG. 9B shows the difference (residual) between the pixel average value and the approximate curve for each sub-scanning position shown in FIG. 9A, and the vertical axis indicates the residual value and the horizontal axis. Is the sub-scanning position. When there is a nozzle having a discharge failure in the recording head 6cl, the residual value (absolute value) becomes extremely large at any of the sub-scanning positions as shown in FIG. 9B. Therefore, the detection unit 57 determines an appropriate threshold value that can determine the variation in the residual due to such a nozzle ejection failure, and compares the residual at each sub-scanning position with this threshold value, thereby recording. It is possible to detect a nozzle ejection failure in the head 6cl.

  Also, when inspecting nozzle ejection defects in the recording heads 6y, 6m, 6c, and 6k that eject color inks, the two-dimensional image sensor 25 alone uses these recording heads 6y, 6m, 6c, and 6k as described above. The image is picked up so that the first pattern P1 formed by using the method enters the diffuse reflection region R2. For this reason, when there is a nozzle in which ejection failure has occurred in the recording heads 6y, 6m, 6c, and 6k, the diffuse reflection region R2 of the image Im in the subject region has high luminance (low density) along the main scanning direction. A defect line appears. The detection unit 57 analyzes the diffuse reflection region R2 of the image Im of the subject region, and detects such defective lines, thereby detecting nozzle ejection defects in the recording heads 6y, 6m, 6c, and 6k that eject color ink. It can be detected.

  For example, the detection unit 57 first extracts the image Im of the subject area from the captured image of the two-dimensional image sensor 25 temporarily stored in the frame memory 52. Then, the detection unit 57 adds and averages the pixel values of each pixel at the position of the first pattern P1 in the diffuse reflection region R2 of the extracted image Im of the subject region in the main scanning direction, and averages the pixels for each sub-scanning position. Find the value. Then, the detection unit 57 compares the pixel average value for each sub-scanning position with a predetermined threshold value, and if there is a position where the pixel average value exceeds the threshold value, it is determined that ejection failure has occurred in the nozzle at that position. To do.

  FIG. 10 is a diagram illustrating an example of processing performed by the detection unit 57 when inspecting nozzle ejection defects in the recording head 6m. FIG. 10 shows an example in which pixel values (RGB data) of each pixel at the position of the first pattern P1 formed of magenta ink in the diffuse reflection region R2 are averaged in the main scanning direction. 10A shows the pixel average value of R data, FIG. 10B shows the pixel average value of G data, and FIG. 10C shows the pixel average value of B data.

  When the recording head 6m that discharges magenta ink includes a nozzle that has an ejection failure, as shown in FIGS. 10B and 10C, the values of the G data and B data are particularly at the sub-scanning position. It becomes extremely large in either. Therefore, the detection unit 57 sets an appropriate threshold value that can determine the variation in G data and B data due to such a nozzle ejection failure, and compares the residual at each sub-scanning position with this threshold value. Thus, it is possible to detect nozzle ejection defects in the recording head 6m.

  As shown in the image Im of the subject area shown in FIG. 8, the second pattern P2 formed with clear ink is positioned in the regular reflection area R1, and the first pattern formed with color ink in the diffuse reflection area R2. When the two-dimensional image sensor 25 captures an image in which the pattern P1 is located, the detection unit 57 uses the one image to detect nozzle ejection defects in the recording heads 6y, 6m, 6c, and 6k that eject color ink. In addition, it is possible to simultaneously inspect nozzle ejection defects in the recording head 6cl that ejects clear ink.

  As described above, the inspection result of the nozzle ejection failure in the recording head 6 is sent from the colorimetric camera 20 to the CPU 101 via the control FPGA 110. In the image forming apparatus 100 according to the present embodiment, when the CPU 101 receives a test result indicating that the ejection failure of the nozzles has occurred in the recording head 6, the maintenance mechanism 15 performs wiping on the ejection surface of the recording head 6 in accordance with a command from the CPU 101. A recovery operation such as empty ink ejection is performed to eliminate nozzle ejection defects. At this time, the recovery operation by the maintenance mechanism 15 may be performed on the entire ejection surface of the recording head 6, or may be performed on a defective area that is an area including a nozzle in which ejection failure is detected. The defective area in the recording head 6 includes, for example, the position in the sub-scanning direction where the defective line is detected in the image Im of the subject area, and the feed amount (movement amount in the sub-scanning direction) of the recording medium M when the defective line is detected. ) And can be identified.

  Further, in the image forming apparatus 100 according to the present embodiment, when a nozzle ejection failure in the recording head 6 is detected, a nozzle ejection failure occurs in the recording head 6 due to, for example, display on an operation panel (not shown). This may be notified to the operator. In this case, the maintenance mechanism 15 performs the recovery operation of the recording head 6 in accordance with the operation of the operator, so that the ejection failure of the nozzle can be eliminated.

  FIG. 11 is a flowchart showing an example of the operation of the colorimetric camera 20 when inspecting the ejection failure of the nozzles in the recording head 6, and the recording head 6 y that discharges color ink by one-time imaging by the two-dimensional image sensor 25. , 6m, 6c, and 6k, and a nozzle ejection defect in the recording head 6cl that ejects clear ink are simultaneously inspected.

  In the case of this example, the test pattern is formed on the recording medium M so that the first pattern formed using the color ink and the second pattern formed using the clear ink are arranged side by side. Then, the recording medium M formed so that the first pattern and the second pattern are arranged is set at a predetermined position on the platen 16 of the image forming apparatus 100. The predetermined position is such that when the two-dimensional image sensor 25 of the colorimetric camera 20 captures an image of the inspection pattern, the second pattern P2 is in the regular reflection region R1 in the image Im of the subject region described above (see FIG. 8). This is the position of the recording medium M where the first pattern P1 enters the diffuse reflection region R2.

  When the recording medium M is set at a predetermined position, first, the inspection light source 32 of the light source unit 31 is turned on to illuminate the subject area (step S101). Then, the two-dimensional image sensor 25 captures an image under illumination by the inspection light source 32 of the light source unit 31 (step S102). An image captured by the two-dimensional image sensor 25 is stored in the frame memory 52.

  Next, the detection unit 57 extracts the image Im of the subject area from the image stored in the frame memory 52 (step S103). Then, as described above, the detection unit 57 analyzes the regular reflection region R1 of the image Im of the subject region, thereby inspecting nozzle ejection defects in the recording head 6cl that ejects clear ink (step S104). In addition, the detection unit 57 analyzes the diffuse reflection region R2 of the image Im of the subject region, thereby inspecting nozzle ejection defects in the recording heads 6y, 6m, 6c, and 6k that eject color ink (step S105). Note that the order of the process of step S104 and the process of step S105 may be reversed.

  Next, the detection unit 57 determines whether or not the inspection for all the nozzles of the recording head 6 to be inspected has been completed (step S106). When the inspection for all nozzles has not been completed (step S106: No), the recording medium M on which the inspection pattern is formed is transported by a predetermined amount in the sub-scanning direction (step S107), and the processing after step S102 is repeated. . Then, when the inspection for all nozzles is completed (step S106: Yes), the inspection light source 32 of the light source unit 31 is turned off (step S108), and a series of processing ends.

  In the case of individually inspecting nozzle ejection defects in the recording heads 6y, 6m, 6c, and 6k that eject color ink and nozzle ejection defects in the recording head 6cl that ejects clear ink, the two-dimensional image sensor 25 is used. Thus, the first pattern P1 and the second pattern P2 are separately imaged, the above-described processing of step S105 is performed on the image captured of the first pattern P1, and the image captured of the second pattern P2 is described above. The process of step S104 may be performed.

  As described above in detail with specific examples, the colorimetric camera 20 (an example of a nozzle inspection apparatus) according to the present embodiment is an inspection pattern in which the two-dimensional image sensor 25 is formed of color ink. An image Im of the subject area is captured so that a certain first pattern P1 is positioned in the diffuse reflection area R2 and a second pattern P2 that is an inspection pattern formed by clear ink is positioned in the regular reflection area R1. Then, the detection unit 57 analyzes the regular reflection region R1 of the image Im of the subject region, inspects the nozzle ejection failure in the recording head 6cl that ejects clear ink, and analyzes the diffuse reflection region R2 of the image Im of the subject region. The nozzles in the recording heads 6y, 6m, 6c, and 6k that discharge the color inks are inspected for defective ejection. Accordingly, there is no need to provide two sensors for detecting diffuse reflection light and for detecting regular reflection light as in the prior art, and recording that discharges color ink with a simple configuration using only one two-dimensional image sensor 25. Both nozzle ejection defects in the heads 6y, 6m, 6c, and 6k and nozzle ejection defects in the recording head 6cl that ejects clear ink can be appropriately inspected.

  In addition, the regular reflection region R1 in the image Im of the subject region has a size in a direction corresponding to a relative movement direction (main scanning direction) between the nozzle row 17 of the recording head 6cl and the recording medium M in a direction orthogonal thereto. It is made bigger than this. That is, the light source unit 31 illuminates the subject region so that the regular reflection region R1 is formed on the image Im of the subject region captured by the two-dimensional image sensor 25. Therefore, according to the colorimetric camera 20 of the present embodiment, it is possible to detect a nozzle ejection failure in the recording head 6cl that ejects clear ink as a defective line in the image, and the nozzle in the recording head 6cl that ejects clear ink. It is possible to properly inspect the ejection failure.

  Further, according to the colorimetric camera 20 of the present embodiment, the recording head 6cl uses the inspection pattern image captured by the two-dimensional image sensor 25 regardless of the type of the recording medium M on which the inspection pattern is formed. It is possible to appropriately inspect nozzle discharge defects. For example, even when a test pattern is formed on glossy paper having a coat layer, or when a test pattern is formed on plain paper without a coat layer, the recording head 6cl that discharges clear ink. If there is a nozzle ejection failure, a defective line appears in the regular reflection region R1 of the image Im in the subject region. For this reason, according to the colorimetric camera 20 of the present embodiment, it is possible to appropriately detect nozzle ejection defects in the recording head 6cl by the above-described method regardless of the type of the recording medium M on which the test pattern is formed. .

  Further, since the image forming apparatus 100 according to the present embodiment includes the colorimetric camera 20 having a function of inspecting the nozzle ejection failure in the recording head 6 described above, the recording head 6 is detected when the nozzle ejection failure is detected. By performing the recovery operation, it is possible to suppress the deterioration of the image quality of the printed image.

  Although specific embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments as they are, and various modifications and changes are made without departing from the scope of the invention in the implementation stage. It can be embodied. For example, in the above-described embodiment, an example of inspecting the nozzle ejection failure in the recording head 6cl that ejects clear ink has been described. However, the present invention is not limited to the recording head 6cl that ejects clear ink, but may be white ink or the like. Also, the present invention can be effectively applied to the case of inspecting nozzle ejection defects in a recording head that ejects ink whose visibility decreases when ejected onto the recording medium M. The inspection pattern formed by discharging the white ink from the recording head to the white recording medium M is less visible under illumination by the colorimetric light source 30, and the nozzle discharge failure is caused by the same method as in the prior art. It is difficult to inspect. However, under illumination by the light source unit 31 (inspection light source 32), an image Im of the subject region is captured so that the inspection pattern formed with white ink enters the regular reflection region R1, and the image Im of the subject region is analyzed. By doing so, similarly to the above-described example, it is possible to appropriately inspect nozzle ejection defects in the recording head that ejects white ink.

  In the above-described embodiment, the serial head type that forms an image by ejecting ink from the nozzle row 17 of the recording head 6 to the recording medium M while reciprocating the carriage 5 on which the recording head 6 is mounted in the main scanning direction. This is an example applied to the image forming apparatus 100. However, the present invention fixes a recording head (line head) having a nozzle array along the main scanning direction, and discharges ink from the nozzle array of the recording head to the recording medium while conveying the recording medium in the sub-scanning direction. Thus, the present invention can also be effectively applied to a line head type image forming apparatus that forms an image.

  When the present invention is applied to a line head type image forming apparatus, the relative movement direction between the nozzle array and the recording medium when the above-described inspection pattern is formed is the sub-scanning direction. For this reason, the nozzle inspection apparatus has a regular reflection region in which the size in the direction corresponding to the sub-scanning direction is larger than the size in the direction corresponding to the main scanning direction in the image of the inspection pattern captured by the two-dimensional image sensor. Configured to be formed.

  When the nozzle inspection apparatus corresponding to the line head type image forming apparatus is realized with the same configuration as the color measurement camera 20 of the above-described embodiment (hereinafter referred to as the color measurement camera 20 ′), the color measurement camera 20 ′ For example, the configuration is as shown in FIG. In other words, the colorimetric camera 20 ′ is attached to the line head so as to be movable in the main scanning direction (direction of arrow A in the figure), for example. As shown in FIG. 12, the light source unit 31 of the colorimetric camera 20 ′ includes a plurality of light sources 31 arranged inside the housing 23 so as to be arranged in a straight line along the sub-scanning direction (the arrow B direction in the figure). The inspection light source 32 is included. Accordingly, the direction in which the plurality of inspection light sources 32 are arranged matches the relative movement direction of the recording head 6cl and the recording medium M when forming the inspection pattern. Therefore, a regular reflection region R1 in which regular reflected light from a plurality of inspection light sources 32 is arranged in the main scanning direction is formed in the image Im of the subject region captured by the two-dimensional image sensor 25, which is described above. Similar to the embodiment, it is possible to appropriately inspect nozzle ejection defects in the recording head 6cl that ejects clear ink.

6 Recording head 17 Nozzle array 20 Colorimetric camera 25 Two-dimensional image sensor 31 Light source unit 32 Inspection light source 57 Detection unit 100 Image forming apparatus M Recording medium Im Image of subject area R1 Regular reflection area R2 Diffuse reflection area P1 First pattern P2 Second pattern

Japanese Patent Laying-Open No. 2005-22218

Claims (6)

A two-dimensional image sensor that images a predetermined imaging range including a pattern formed by ejecting ink onto a recording medium from a nozzle row composed of a plurality of nozzles;
The imaging range so that an image of the imaging range captured by the two-dimensional image sensor includes a regular reflection region that is an image region based on specular reflection light and a diffuse reflection region that is an image region based on diffuse reflection light. A light source unit for illuminating
A detection unit that analyzes an image of the imaging range and detects a discharge failure of the nozzle, and
In the two-dimensional image sensor, when the pattern is a first pattern formed of color ink, the first pattern is located in the diffuse reflection area, and the pattern is formed of a clear ink or a white ink. In the case of a pattern, the imaging range is imaged so that the second pattern is located in the regular reflection region,
When the pattern is the first pattern, the detection unit analyzes the diffuse reflection area to inspect the ejection failure of the nozzle that has formed the first pattern, and the pattern is the second pattern Is a nozzle inspection apparatus that analyzes the regular reflection region and inspects the ejection failure of the nozzle on which the second pattern is formed. The two-dimensional image sensor includes the imaging range including both the first pattern and the second pattern, wherein the first pattern is located in the diffuse reflection area and the second pattern is located in the regular reflection area. To image,
The detection unit analyzes the diffuse reflection region to inspect the ejection failure of the nozzle that has formed the first pattern, and analyzes the regular reflection region to analyze the ejection failure of the nozzle that has formed the second pattern. The nozzle inspection device according to claim 1, wherein: The pattern is formed while relatively moving the nozzle row and the recording medium in a direction perpendicular to the nozzle row,
The specular reflection region has a size in a direction corresponding to a relative movement direction between the nozzle row and the recording medium in an image in the imaging range, which is larger than a direction perpendicular to the direction corresponding to the relative movement direction. The nozzle inspection apparatus according to claim 1, wherein the nozzle inspection apparatus is large. The light source unit has a plurality of light sources,
The plurality of light sources are arranged such that in the image in the imaging range, the specular reflection region is formed by aligning specularly reflected light of each light source along a direction corresponding to the relative movement direction. The nozzle inspection apparatus according to claim 3.   An image forming apparatus comprising the nozzle inspection apparatus according to claim 1. A two-dimensional image sensor that images a predetermined imaging range including a pattern formed by ejecting ink onto a recording medium from a nozzle row composed of a plurality of nozzles;
An image of the imaging range captured by the two-dimensional image sensor is a regular reflection region that is an image region based on specular reflection light of the imaging range, and a diffuse reflection region that is an image region based on diffuse reflection light of the imaging range; A light source unit that illuminates the imaging range,
A nozzle inspection method that is executed by a nozzle inspection device comprising: a detection unit that analyzes an image of the imaging range and detects a discharge failure of the nozzle,
When the two-dimensional image sensor is a first pattern in which the pattern is formed by color ink, the first pattern is located in the diffuse reflection area, and the pattern is formed by a clear ink or a white ink. In the case of a pattern, imaging the imaging range so that the second pattern is located in the regular reflection region;
When the detection unit analyzes the diffuse reflection region when the pattern is the first pattern and inspects the ejection failure of the nozzle that has formed the first pattern, and the pattern is the second pattern Analyzing the regular reflection area and inspecting the ejection failure of the nozzle having the second pattern formed thereon.