Inspection apparatus and liquid discharge apparatus

Abstract

A liquid discharge apparatus includes: a controller configured to control a discharge head having a discharge surface that has a nozzle to discharge a liquid from the nozzle; an imager to capture an image of the liquid discharged from the nozzle, as a luminance change, to detect a discharge state of the discharge head; a mover to move one of the discharge head or the imager relative to each other in one direction; a detector to detect a position of the discharge surface of the discharge head in the image with the luminance change imaged by the imager; and a determination unit to determine the discharge state of the discharge head based on the position of the discharge surface and the discharge state of the liquid discharged from the nozzle.

Description

[DESCRIPTION][Title of Invention]INSPECTION APPARATUS AND LIQUID DISCHARGE APPARATUS [Technical Field]

[0001] The present embodiment relates to an inspection apparatus and a liquid discharge apparatus. [Background Art]

[0002] There is known a technique for cleaning dirt off a nozzle of an ink discharge head so as to eliminate a failure of ink discharge from the ink discharge head in an inkjet liquid discharge apparatus.

[0003] As a technique for detecting such a failure of ink discharge from the ink discharge head, there is disclosed a technique for calculating states of a flying ink droplet discharged from the ink discharge head, such as the speed and flying direction of the ink droplet, by an optical detection apparatus including a stroboscopic light source and a camera, and performing cleaning when the speed and flying direction of the ink droplet are out of allowable value ranges (for example, Patent Literature (PTL) 1). In a case where there are ink droplets accumulating in the vicinity of a nozzle, ink is thickened in the vicinity of the nozzle due to drying, or ink is thickened due to precipitation of solid content of the ink in the vicinity of the nozzle, the speed of a flying ink droplet becomes slower, the bend of the ink droplet becomes larger, and the volume of the ink droplet tends to change, but a stable flying state may be entered after several droplets are discharged. In a method using such a stroboscopic light source, the average position of a plurality of ink droplets is imaged to detect the speed, bend, volume, and the like of ink. Therefore, it is not possible to detect the speed, bend, volume, and the like of a first droplet. In order to eliminate this disadvantage, there is a method for performing imaging at a high frame rate with a camera, such as a high-speed camera, to image the discharge states of droplets from the first droplet. However, due to a high calculation load, a high-speed camera requires a large cooling device, so that the detection apparatus also becomes large. In order to eliminate this disadvantage, there is a method for recording, as a captured image, only a moving portion in an image, that is, a portion where a luminance difference (luminance change) occurs, to perform imaging at a high frame rate and with a low calculation load. This method enables the flying states of ink droplets to be grasped from the first droplet with a low calculation load and without requiring a cooling device. [Summary of Invention] [Technical Problem]

[0004] However, the above-described technique is disadvantageous in that, unlike a case where a camera using strobe light or a high-speed camera is used, when a camera is used whichrecords, as a captured image, only a portion where a luminance difference (luminance change) occurs, it is not possible to capture an image of a discharge surface of an ink discharge head where no luminance difference occurs, and thus it is not possible to recognize a reference position where the speed, bend, and the like of an ink droplet are detected.

[0005] The present embodiment has been made in view of the above, and an object of the present embodiment is to provide an inspection apparatus and a liquid discharge apparatus that enable reduction of a calculation load, prevention of an increase in apparatus size, and detection of a discharge surface of a discharge head.[Solution to Problem]

[0006] In an aspect of the present disclosure, a liquid discharge apparatus is provided that includes: a controller configured to control a discharge head having a discharge surface that has a nozzle to discharge a liquid from the nozzle; an imager to capture an image of the liquid discharged from the nozzle, as a luminance change, to detect a discharge state of the discharge head; a mover to move one of the discharge head or the imager relative to each other in one direction; a detector to detect a position of the discharge surface of the discharge head in the image with the luminance change imaged by the imager; and a determination unit to determine the discharge state of the discharge head based on the position of the discharge surface and the discharge state of the liquid discharged from the nozzle. The imager captures an image of the discharge surface while the mover moves the one of the discharge head or the imager to change the position of the discharge surface relative to the imager in the one direction. [Advantageous Effects of Invention]

[0007] According to the present embodiment, it is possible to reduce the calculation load, prevent an increase in apparatus size, and detect the discharge surface of the discharge head.[Brief Description of Drawings]

[0008] A more complete appreciation of embodiments of the present disclosure and many of the attendant advantages and features thereof can be readily obtained and understood from the following detailed description with reference to the accompanying drawings.[FIGS. 1A and IB]FIGS. 1A and IB are diagrams illustrating an exemplary overall configuration of a liquid application apparatus according to an embodiment.[FIG. 2]FIG. 2 is a diagram illustrating an exemplary configuration of an inspection apparatus according to the embodiment.[FIG. 3]FIG. 3 is a diagram for describing a positional relationship between the inspection apparatus and a maintenance unit in the liquid application apparatus according to the embodiment. [FIG. 4]FIG. 4 is a diagram for describing an operation outline of an event-based camera.[FIG. 5]FIG. 5 is a diagram for describing operation of detecting an ink droplet in the inspection apparatus according to the embodiment.[FIGS. 6 A to 6C]FIGS. 6A to 6C are diagrams for describing operation of detecting a discharge surface of an ink discharge head in the inspection apparatus according to the embodiment.[FIGS. 7 A and 7B]FIGS. 7A and 7B are diagrams illustrating an exemplary captured image of an ink droplet detected in the inspection apparatus according to the embodiment.[FIGS. 8 A to 8C]FIGS. 8 A to 8C are diagrams for describing operation of a telecentric lens mounted on the event-based camera of the inspection apparatus according to the embodiment.[FIG. 9]FIG. 9 is a diagram for describing operation of calculating a pixel size in the inspection apparatus according to the embodiment.[FIG. 10]FIG. 10 is a diagram illustrating an exemplary hardware configuration of the liquid application apparatus according to the embodiment.[FIG. 11]FIG. 11 is a diagram illustrating an exemplary configuration of functional blocks of the liquid application apparatus according to the embodiment.[FIGS. 12A and 12B]FIGS. 12A and 12B are flowcharts illustrating an exemplary flow of a discharge inspection operation of the liquid application apparatus according to the embodiment.[FIG. 13]FIG. 13 is a diagram illustrating an exemplary configuration of an inspection apparatus according to a first modification of the embodiment.[FIG. 14]FIG. 14 is a diagram illustrating an exemplary configuration of an inspection apparatus according to a second modification of the embodiment.[FIG. 15]FIG. 15 is a diagram illustrating an exemplary configuration of an inspection apparatus according to a third modification of the embodiment.[FIG. 16]FIG. 16 is a diagram for describing light emission operation of a light source in an inspection apparatus according to a fourth modification of the embodiment.[FIG. 17]FIG. 17 is a diagram illustrating an exemplary configuration of an inspection apparatus according to a fifth modification of the embodiment.The accompanying drawings are intended to depict embodiments of the present disclosure and should not be interpreted to limit the scope thereof. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted. Also, identical or similar reference numerals designate identical or similar components throughout the several views. [Description of Embodiments]In describing embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this specification is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that have a similar function, operate in a similar manner, and achieve a similar result.Referring now to the drawings, embodiments of the present disclosure are described below. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0009] Hereinafter, an embodiment of an inspection apparatus and a liquid discharge apparatus according to the present disclosure will be described in detail with reference to the drawings. The present embodiment, however, is not limited to the embodiment described below, and the constituent elements of the embodiment include elements that may be easily conceived by those skilled in the art, those being substantially the same ones, and those being within equivalent ranges. Various omissions, substitutions, changes, and combinations of constituent elements can be made without departing from the gist of the embodiment described below.

[0010] Overall Configuration of Liquid Application ApparatusFIGS. 1A and IB are diagrams illustrating an exemplary overall configuration of a liquid application apparatus according to an embodiment. An overall configuration of a liquid application apparatus 1 according to the present embodiment will be described with reference to FIGS. 1A and IB.

[0011] The liquid application apparatus 1 illustrated in FIGS. 1A and IB is an apparatus (an example of a liquid discharge apparatus) that divides a wide liquid application region such as a road surface or a wall surface of a building (may be hereinafter referred to as a printing surface) into a plurality of print areas and sequentially moves to each print area and then, divides print data for printing on the liquid application region into a plurality of print images and prints thedivided print images. FIG. 1A is a side view of the liquid application apparatus 1, and FIG. IB is a plan view of the liquid application apparatus 1 as viewed from above. Note that the term “printing” refers to applying ink to or spraying ink onto a printing surface.

[0012] As illustrated in FIGS. 1A and IB, the liquid application apparatus 1 includes a printing unit 21 and a control unit 22. Note that the liquid application apparatus 1 may have a system configuration in which the printing unit 21 and the control unit 22 are separate bodies.

[0013] The printing unit 21 is a unit for discharging ink onto a printing surface to perform printing on the printing surface while moving. Note that the term “ink” refers to a liquid to be applied to or sprayed onto the printing surface. As illustrated in FIGS. 1A and IB, the printing unit 21 includes a carriage 2, a rail 3, a three-dimensional camera 7, a two-dimensional camera 8, a global navigation satellite system (GNSS) receiver 9, tires 10, a frame 11, a structure 12, and an inspection apparatus 50.

[0014] The carriage 2 is a member on which an ink discharge head 2a to be described below is mounted, and which moves in a main scanning direction (arrow A indicated in FIG. IB) along the rail 3, and moves in a sub-scanning direction (arrow B indicated in FIG. IB) together with the rail 3 moving in the sub- scanning direction. The carriage 2 reciprocally moves in the main scanning direction along the rail 3 by means of a head moving mechanism 23 (see FIG. 10 to be described below) including a belt, a pulley, a motor, and the like.

[0015] The rail 3 is a rail member that supports the carriage 2 so as to cause the carriage 2 to move in the main scanning direction and is horizontally supported by the frame 11 in such a way as to be movable in the sub-scanning direction. The rail 3 reciprocates on the frame 11 in the subscanning direction orthogonal to the main scanning direction by means of a rail moving mechanism 24 (see FIG. 10 to be described below) including a belt, a pulley, a motor, and the like.

[0016] That is, the carriage 2 on which the ink discharge head 2a is mounted can freely move in a front-back direction (sub- scanning direction) and a left-right direction (main scanning direction) on a plane surrounded by the frame 11 of the liquid application apparatus 1.

[0017] The three-dimensional camera 7 is a three-dimensional shape measuring device for peripheral measurement. The three-dimensional camera 7 is supported on a front portion of the frame 11, and images the periphery of the liquid application apparatus 1. Note that the three- dimensional camera 7 may be supplied with power from a battery mounted thereon, or may be supplied with power from a power supply system 5, assuming continuous operation.

[0018] The two-dimensional camera 8 is an imager that images a printing surface, an image printed on the printing surface, and the vicinity of the printed image. Therefore, an imaging direction of the two-dimensional camera 8 is a downward direction. The two-dimensional camera 8 transmits a captured image to a controller unit 6 to be described below. Note that the two-dimensional camera 8 may be supplied with power from a battery mounted thereon, or may be supplied with power from the power supply system 5, assuming continuous operation. The controller unit 6 may be referred to also simply as “a controller”.

[0019] The GNSS receiver 9 is a receiving device that receives, from a positioning satellite, a positioning signal for measuring a current location on the earth based on the GNSS (for example, a global positioning system (GPS)). The GNSS receiver 9 transmits a received positioning signal to the controller unit 6.

[0020] A plurality of tires 10 is attached to a lower portion of the frame 11. The tires 10 are members that rotate by, for example, being manually pushed by an operator, to cause the printing unit 21 to move. Thus, the liquid application apparatus 1 can be moved in four directions of front, back, left, and right.

[0021] The frame 11 is a frame structure that serves as a base of the printing unit 21 and supports the rail 3, the three-dimensional camera 7, the GNSS receiver 9, the structure 12, and the like from below.

[0022] The structure 12 is a structure in which a pipe and the like are assembled to form an outer frame of the printing unit 21. The structure 12 has an upper surface on which the two- dimensional camera 8 is mounted.

[0023] The inspection apparatus 50 is an apparatus for inspecting flying states of ink droplets discharged from the ink discharge head 2a (discharge head) of the carriage 2. The configuration of the inspection apparatus 50 will be described below with reference to FIG. 2. Note that the flying state can also be referred to as a discharge state.

[0024] As illustrated in FIGS. 1A and IB, the control unit 22 includes an ink supply system 4, the power supply system 5, and the controller unit 6.

[0025] The ink supply system 4 is a unit that supplies ink to be used for printing to the ink discharge head 2a of the carriage 2 via a pipe 4a that is a flow path of ink. The present embodiment assumes that the ink supply system 4 moves following the printing unit 21, but the configuration of the ink supply system 4 is not limited thereto. The ink supply system 4 may be a self-propelled unit that moves independently of the printing unit 21.

[0026] The power supply system 5 is a unit that supplies power for driving the control unit 22, the head moving mechanism 23, the ink discharge head 2a, and the like.

[0027] The controller unit 6 is a control unit for controlling operation of the liquid application apparatus 1. For example, the controller unit 6 controls operation of the head moving mechanism 23, the rail moving mechanism 24, and the ink discharge head 2a, and estimates the position of the liquid application apparatus 1 from a positioning signal received by the GNSS receiver 9. The controller unit 6 uses an image captured by the three-dimensional camera 7 mainly for avoiding contact with an obstacle by means of a method such as image correlation, or for estimating the amount of movement, position, or the like of the liquid application apparatus 1. Furthermore, the controller unit 6 stores the positioning signal received by the GNSS receiver 9, as odometry information such as the cumulative amount of movement of the liquid application apparatus 1. Note that the liquid application apparatus 1 may include a plurality of GNSS receivers 9 such that the controller unit 6 corrects position information on the basis of positioning signals received by the plurality of GNSS receivers 9.

[0028] Note that the liquid application apparatus 1 illustrated in FIGS. 1A and IB has been described as an apparatus that moves by being manually pushed by an operator in principle, but the liquid application apparatus 1 is not limited to such an apparatus. The liquid application apparatus 1 may be a self-propelled apparatus including a motor or the like that can control rotation of the tires 10.

[0029] Configuration of Inspection ApparatusFIG. 2 is a diagram illustrating an exemplary configuration of the inspection apparatus according to the embodiment. FIG. 3 is a diagram for describing a positional relationship between the inspection apparatus and a maintenance unit in the liquid application apparatus according to the embodiment. A configuration of the inspection apparatus 50 according to the present embodiment will be described with reference to FIGS. 2 and 3.

[0030] As illustrated in FIG. 2, the inspection apparatus 50 includes a camera 51, a light source 52, a dummy discharge receiver 53, and a frame 54.

[0031] As described above, the carriage 2 is supported by the rail 3 such that the carriage 2 can reciprocate in an A direction (main scanning direction), and has the ink discharge head 2a mounted thereon. The ink discharge head 2a discharges ink onto the printing surface. The ink discharge head 2a is a thermal (bubble jet) or piezoelectric inkjet head. Note that the ink discharge head 2a may include a plurality of nozzles provided for a single color or ink material, or may include a plurality of nozzles separately provided for different colors or inkmaterials. The inspection apparatus 50 may include an encoder that can detect the amount of movement and speed of the carriage 2. The “A direction (main scanning direction)” may be also referred to as “one direction” intersecting the discharge direction (another direction) of the ink discharge head 2a.

[0032] The camera 51 is an imager (may be hereinafter referred to as an event-based camera) that can record only a portion where a luminance difference (luminance (intensity) change) occurs, as data in a captured image. Operation of the camera 51, which is an event-based camera, will be described below with reference to FIGS. 4 to 7B . As illustrated in FIG. 2, the camera 51 also includes an optical system 51a that is a telecentric lens that operates such that a principal ray is parallel to an optical axis. Operation of the optical system 51a, which is a telecentric lens, will be described below with reference to FIGS. 8 A to 8C. The camera 51 is installed such that at least a discharge surface of the ink discharge head 2a of the carriage 2 falls within the angle of view when the carriage 2 moves in the main scanning direction to an inspection position for inspecting the flying states of ink droplets discharged from the ink discharge head 2a.

[0033] The light source 52 is a light source such as a light-emitting diode (LED) disposed in such a way as to face the camera 51 and be located on a side opposite to the camera 51 with respect to the carriage 2 when the carriage 2 is at the inspection position. That is, the light source 52 emits light toward an imaging surface of the camera 51 from behind the ink discharge head 2a and ink discharged from the ink discharge head 2a. Thus, a luminance difference can be easily generated with respect to the behavior of ink in a captured image.

[0034] The dummy discharge receiver 53 is a receiving member that receives ink discharged for inspection from the ink discharge head 2a. The dummy discharge receiver 53 is secured to the frame 54 such that the dummy discharge receiver 53 is located at a position immediately below the ink discharge head 2a of the carriage 2 when the carriage 2 moves to the inspection position.

[0035] The frame 54 is a frame member formed in, for example, a U-shape, and secures the camera 51, the light source 52, and the dummy discharge receiver 53 as illustrated in FIG. 2.

[0036] Note that the inspection apparatus 50 may be formed as a single unit that can be detached from the liquid application apparatus 1 and also attach to the liquid application apparatus.

[0037] When inspection of ink discharge of the ink discharge head 2a is performed in the inspection apparatus 50 having such a configuration, the carriage 2 moves to the inspection position and stops at the inspection position as described above. Then, the light source 52 emits light, theink discharge head 2a starts ink discharge for inspection, and the camera 51 starts imaging. As described above, the light source 52 emits light toward an imaging surface of the camera 51 from behind the ink discharge head 2a and ink discharged from the ink discharge head 2a. Therefore, the camera 51 images an ink droplet as a shadow. An ink droplet is imaged as a shadow so as to create an environment in which the camera 51 can easily detect the ink droplet, as follows: when there is no ink droplet, the entire surface is put under the light such that there is no luminance difference, and when an ink droplet starts moving, a shadow is cast to generate a large luminance difference.

[0038] As illustrated in FIG. 3, the liquid application apparatus 1 includes a maintenance unit 13. The maintenance unit 13 includes, for example, a cleaning device 14 to be described below, for cleaning the nozzles on the discharge surface of the ink discharge head 2a.

[0039] The carriage 2 including the ink discharge head 2a moves to a position (standby position) corresponding to the maintenance unit 13 located outside a print area PAR before printing, and moves to the inspection position so as to inspect the flying state of an ink droplet when a print command is issued. Then, in a case where the ink discharge state is within an allowable range at the inspection position, the carriage 2 moves onto the print area PAR and starts printing.

[0040] In the exemplary configuration illustrated in FIG. 3, the maintenance unit 13 and the inspection apparatus 50 are located across the print area PAR from each other, but the present embodiment is not limited thereto. The maintenance unit 13 and the inspection apparatus 50 may be arranged adjacent to each other.

[0041] Operation of Event-based CameraFIG. 4 is a diagram for describing an operation outline of an event-based camera. FIG. 5 is a diagram for describing operation of detecting an ink droplet in the inspection apparatus according to the embodiment. FIGS. 6A to 6C are diagrams for describing operation of detecting the discharge surface of the ink discharge head in the inspection apparatus according to the embodiment. FIGS. 7A and 7B are diagrams illustrating an exemplary captured image of an ink droplet detected in the inspection apparatus according to the embodiment.Operation of the event-based camera (camera 51) will be described with reference to FIGS. 4 to 7B.

[0042] When a luminance change of light detected for each pixel of an imaging element exceeds a predetermined threshold, the event-based camera detects the luminance change as an event, and records, as a captured image, coordinates (X, Y) of a pixel in which the event has occurred, time, and polarity (whether luminance has changed in higher direction or lowerdirection). That is, the captured image can be assumed to be an image including, for each imaging time, pixel values of ternary data of positive polarity (luminance has changed in higher direction), negative polarity (luminance has changed in lower direction), and no data. Therefore, it is not necessary to perform processing to obtain a grayscale image or binarized image as often performed in image processing. As described above, the captured image includes data on only coordinates of a pixel in which a luminance change has occurred, time, and polarity. Thus, a calculation load of the processing can be reduced. Note that it is possible to use, as the event-based camera, known cameras disclosed in, for example, Japanese Translation of PCT International Application Publication No. JP-T-2020-503752 and Japanese Translation of PCT International Application Publication No. JP-T-2020- 505801.

[0043] For example, the trajectory of a ball moving on a parabola is exemplified in FIG. 4, but a captured image BIMI captured at a timing when the ball was thrown up includes only data (coordinates, time, and polarity) on a pixel corresponding to a portion of the ball located on the left side where a luminance change has occurred. Then, a captured image BIM2 that is an image of the ball that has reached a highest point of the parabola includes only data on a pixel corresponding to a portion of the ball where a luminance change has occurred, and a captured image BIM3 that is an image of the ball further descending includes only data on a pixel corresponding to a portion of the ball where a luminance change has occurred.

[0044] When the camera 51, which is an event-based camera that can perform the operation as described above, captures an image of an ink droplet discharged for inspection from the ink discharge head 2a as illustrated in FIG. 5, the ink droplet moves and a luminance difference (luminance change) occurs. Thus, the camera 51 can capture the image. Meanwhile, when an ink droplet for inspection is discharged, the carriage 2 on which the ink discharge head 2a is mounted does not move, and stops at the inspection position. As a result, the camera 51 cannot image the carriage 2, as illustrated in FIG. 6A. In a case where the carriage 2 cannot capture an image, it is not possible to recognize the position of the discharge surface of the ink discharge head 2a, serving as a reference position for calculating the speed, bend, and the like of the ink droplet. Therefore, in the present embodiment, the camera 51 captures an image of the carriage 2 when the carriage 2 moves to the inspection position, that is, when the carriage 2 moves parallel to the discharge surface of the ink discharge head 2a, as illustrated in FIG. 6B. The moving direction parallel to the discharge surface of the ink discharge head 2a is an example of “one predetermined direction” of the present embodiment. Thus, the position of the discharge surface of the ink discharge head 2a can be detected as an edge that causes a luminance difference, and the speed, bend, and the like of an ink droplet can be calculated with reference to the position. Here, the position of the discharge surface of theink discharge head 2a refers to the position and angle of the discharge surface of the ink discharge head 2a in a captured image.

[0045] As illustrated in FIG. 6C, even when the carriage 2 is fixed in an inclined manner with respect to the angle of view of the camera 51, it is possible to detect the discharge surface of the ink discharge head 2a by moving the carriage 2 in the one predetermined direction.

[0046] As described above, after the discharge surface of the ink discharge head 2a is detected while the carriage 2 is moving to the inspection position, the ink discharge head 2a discharges an ink droplet for inspection, and the camera 51 images the ink droplet. Here, an ink droplet imaged by the camera 51 is exemplified in FIGS. 7A and 7B. FIG. 7A illustrates an image of an ink droplet captured immediately after discharge of the ink droplet from the discharge surface of the ink discharge head 2a, and FIG. 7B illustrates a captured image of the ink droplet in a state where a predetermined time has elapsed from the state of FIG. 7A. As in the captured images illustrated in FIGS. 7A and 7B, the ink droplet can be recognized as an aggregate of pixel values of positive and negative polarities. Furthermore, since the position of the discharge surface is detected, it is possible to calculate the speed of an ink droplet and the bend of the ink droplet with respect to the discharge surface (inclination of the path of the ink droplet with respect to the discharge surface) with reference to the position, and make a comparison between the nozzles. Furthermore, the amount of ink in an ink droplet can be calculated from the size of the ink droplet included in the captured image. Furthermore, it is also possible to count the actual numbers of main droplets, satellite droplets, and mist droplets discharged in response to a discharge signal for discharging a single droplet from the nozzle of the ink discharge head 2a.

[0047] Furthermore, as illustrated in FIGS. 7A and 7B, the rear end of a flying ink droplet has a positive polarity, where there is no ligament and the ink droplet disappears. Thus, the image appears bright. Here, the ligament refers to a tail shaped ink portion extending toward the rear end side in a discharge direction after discharge of the ink droplet. The “discharge direction” may be referred to also as “another direction”. Furthermore, in a case where a ligament is generated when an ink droplet is discharged downward, the ligament remains at a location of generation of the ligament, and is on a corresponding pixel. Thus, there is no change in polarity, and the ligament does not appear in a captured image. However, in a case where the ink discharge head 2a performs discharge while moving in a single direction as illustrated in FIGS. 6A to 6C, an ink droplet also moves in the moving direction of the ink discharge head 2a. Therefore, in a case where a ligament is generated, it is possible to detect, in the captured image, the ligament which is negative in polarity on a side to which the ink discharge head 2a moves and is positive in polarity on the opposite side.

[0048] Operation of Calculating Pixel SizeFIGS. 8 A to 8C are diagrams for describing operation of the telecentric lens mounted on the event-based camera of the inspection apparatus according to the embodiment. FIG. 9 is a diagram for describing operation of calculating a pixel size in the inspection apparatus according to the embodiment. Operation of the optical system 51a, which is a telecentric lens mounted on the camera 51 of the inspection apparatus 50 according to the present embodiment, and operation of calculating a pixel size will be described with reference to FIGS. 8A to 9.

[0049] First, as illustrated in FIG. 8A, it is assumed that two rectangular parallelepiped objects equal in size are arranged at positions with different depths in an imaging direction of the camera 51. In this case, when an image is captured by use of a standard lens having a fixed focal point, an object on the front side appears larger, and an object on the back side appears smaller, due to a difference in depth as illustrated in FIG. 8B. Therefore, when the distance to a subject changes, the size of the subject also changes, and thus, in a case where an ink droplet is a subject, it is not possible to accurately calculate the speed, bend, and volume of the ink droplet.

[0050] Meanwhile, the optical system 51a mounted on the camera 51 is a telecentric lens as described above, and collimates a principal ray from a subject with respect to the optical axis of the optical system 51a. Thus, as illustrated in FIG. 8C, even if objects are arranged at positions with different depths, the objects are imaged as equally sized objects as long as the objects are equal in size. Therefore, it is possible to calculate a pixel size, which is an actual distance or length corresponding to a single pixel of a captured image, regardless of a depth at which an ink droplet is captured. It is thus possible to accurately calculate the speed, bend, and volume of the ink droplet. Specifically, as illustrated in FIG. 9, the inspection apparatus 50 can calculate a pixel size, which is an actual distance or length corresponding to a single pixel, by dividing the actual amount of movement of the carriage 2 by the number of pixels corresponding to the amount of movement of the carriage 2 in a captured image during a discharge inspection operation. The pixel size may be calculated by multiplication of the pixel size of the event-based camera by the magnification of the telecentric lens, if known.

[0051] Hardware Configuration of Liquid Application ApparatusFIG. 10 is a diagram illustrating an exemplary hardware configuration of the liquid application apparatus according to the embodiment. A hardware configuration of the liquid application apparatus 1 according to the present embodiment will be described with reference to FIG. 10.

[0052] As illustrated in FIG. 10, the liquid application apparatus 1 includes the carriage 2, the controller unit 6, the three-dimensional camera 7, the two-dimensional camera 8, the GNSS receiver 9, the cleaning device 14, an operation panel 15, the head moving mechanism 23, the rail moving mechanism 24, and the inspection apparatus 50.

[0053] The ink discharge head 2a that discharges ink on a printing surface is mounted on the carriage 2. The carriage 2 moves in the main scanning direction along the rail 3 illustrated in FIGS. 1A and IB, and moves in the sub- scanning direction together with the rail 3 moving in the sub-scanning direction.

[0054] The controller unit 6 includes a central processing unit (CPU) 61, a memory 62, an interface (I / F) 63, and a unit control circuit 64.

[0055] The CPU 61 is an arithmetic device that integrally controls the operation of the liquid application apparatus 1. The CPU 61 performs data communication with the memory 62, the I / F 63, and the unit control circuit 64 via a bus. Furthermore, the CPU 61 controls the driving of the head moving mechanism 23, the rail moving mechanism 24, and the ink discharge head 2a via the unit control circuit 64, and estimates a self-position of the liquid application apparatus 1 from a positioning signal received by the GNSS receiver 9.

[0056] The memory 62 is a storage medium, such as a read only memory (ROM) or a random access memory (RAM), that stores a program to be used to drive the CPU 61. In addition, the memory 62 is used as a work area for the CPU 61.

[0057] The I / F 63 is a communication interface for connecting various external devices 30 such as a tablet terminal, a smartphone, a personal computer (PC), a server, and a notebook PC. In the present embodiment, the I / F 63 performs data communication with the inspection apparatus 50.

[0058] The unit control circuit 64 is a control circuit that controls the operation of the head moving mechanism 23, the rail moving mechanism 24, and the ink discharge head 2a under the control of the CPU 61.

[0059] The three-dimensional camera 7 and the two-dimensional camera 8 transmit captured images to the CPU 61 of the controller unit 6.

[0060] The GNSS receiver 9 receives a positioning signal for measuring a current location on the earth from a positioning satellite based on the GNSS (for example, GPS), and transmits the positioning signal to the CPU 61 of the controller unit 6.

[0061] The cleaning device 14 is a device that cleans the discharge surface on which the nozzles of the ink discharge head 2a are located, under the control of the CPU 61.

[0062] The operation panel 15 is a device that receives an operation on the liquid application apparatus 1 and displays a result of processing performed by the liquid application apparatus 1.

[0063] The head moving mechanism 23 is a mechanism that includes a belt, a pulley, a motor, and the like, and reciprocates the carriage 2 in the main scanning direction along the rail 3 under the control of the unit control circuit 64.

[0064] The rail moving mechanism 24 is a mechanism that includes a belt, a pulley, a motor, and the like, and reciprocates the rail 3 on the frame 11 in the sub-scanning direction orthogonal to the main scanning direction under the control of the unit control circuit 64. As a result, the carriage 2 supported by the rail 3 reciprocates in the sub-scanning direction.

[0065] As illustrated in FIG. 10, the inspection apparatus 50 includes the camera 51, the light source 52, and a control circuit 55. Note that the camera 51 and the light source 52 are as described above.

[0066] The control circuit 55 is a control circuit for controlling operation of the inspection apparatus 50. As illustrated in FIG. 10, the control circuit 55 includes a CPU 71, a memory 72, an I / F 73, an imaging I / F 74, and a light source drive circuit 75.

[0067] The CPU 71 is an arithmetic device that integrally controls the operation of the inspection apparatus 50. The CPU 71 performs data communication with the memory 72, the I / F 73, the imaging I / F 74, and the light source drive circuit 75 via a bus. Furthermore, the CPU 71 controls the imaging operation of the camera 51 via the imaging I / F 74, and controls the light emitting operation of the light source 52 via the light source drive circuit 75.

[0068] The memory 72 is a storage medium, such as a ROM or a RAM, which stores a program to be used to drive the CPU 71. In addition, the memory 72 is used as a work area for the CPU 71.

[0069] The I / F 73 is an interface for performing data communication with the controller unit 6.

[0070] The imaging I / F 74 is an interface for performing data communication with the camera 51. Specifically, the imaging I / F 74 receives an image captured by the camera 51, and transmits,to the camera 51, a control signal received from the CPU 71, the control signal being related to the imaging operation.

[0071] The light source drive circuit 75 is a drive circuit that causes the light source 52 to emit light, under the control of the CPU 71.

[0072] Note that the hardware configuration of the liquid application apparatus 1 illustrated in FIG. 10 is an example, and other components may be included in the liquid application apparatus 1. For example, the inspection apparatus 50 may include a display device that displays an inspection result of the discharge inspection operation.

[0073] Configuration and Operation of Functional Blocks of Liquid Application ApparatusFIG. 11 is a diagram illustrating an exemplary configuration of functional blocks of the liquid application apparatus according to the embodiment. The configuration and operation of the functional blocks of the liquid application apparatus 1 according to the present embodiment will be described with reference to FIG. 11.

[0074] As illustrated in FIG. 11, the control circuit 55 of the inspection apparatus 50 includes a communicator 101, an inspection controller 102, a pixel calculator 103, a discharge surface detector 104 (detection unit), a discharge command unit 105, a discharge calculator 106 (calculation unit), a determination unit 107, a cleaning command unit 108, an imaging controller 109, a light source controller 110, and a display controller 111. The discharge surface detector 104 (detection unit) may be referred to simply as “a detector”.

[0075] The communicator 101 is a functional unit that performs data communication with the controller unit 6 via the I / F 73.

[0076] The inspection controller 102 is a functional unit for controlling the discharge inspection operation in cooperation with the controller unit 6 while transmitting and receiving control signals to and from the controller unit 6 in the execution of the discharge inspection operation. For example, the inspection controller 102 receives a start signal of the discharge inspection operation from the controller unit 6 via the communicator 101, and transmits a result of inspection of the flying state of an ink droplet to the controller unit 6 via the communicator 101.

[0077] The pixel calculator 103 is a functional unit that calculates a pixel size which is an actual distance or length corresponding to a single pixel in an image captured by the camera 51 and acquired by the imaging controller 109. Specifically, the pixel calculator 103 acquires the amount of movement of the carriage 2 to the inspection position, from the controller unit 6 viathe communicator 101. Next, the pixel calculator 103 calculates the number of pixels corresponding to the amount of movement of the carriage 2 in the image captured by the camera 51 and acquired by the imaging controller 109, based on the path of the discharge surface of the ink discharge head 2a detected by the discharge surface detector 104. Then, the pixel calculator 103 calculates the pixel size by dividing the acquired amount of movement of the carriage 2 to the inspection position by the calculated number of pixels.

[0078] The discharge surface detector 104 is a functional unit that detects the position of the discharge surface of the ink discharge head 2a of the carriage 2 from the image captured by the camera 51 and acquired by the imaging controller 109, the image being captured in a state where the carriage 2 moves to the inspection position. Operation of detecting the discharge surface is as described above.

[0079] The discharge command unit 105 is a functional unit that transmits a command signal for providing an instruction for discharge of an ink droplet for inspection, to the controller unit 6 via the communicator 101. The discharge controller 202 (to be described below) of the controller unit 6 causes the ink discharge head 2a to discharge an ink droplet for inspection a predetermined number of times (for example, 10 times) via the unit control circuit 64 in response to the command signal.

[0080] The discharge calculator 106 is a functional unit that calculates the speed of an ink droplet discharged for inspection from the ink discharge head 2a, the bend of the ink droplet, the bend comparison value of the ink droplet for each nozzle, the volume of the ink droplet, the number of ink droplets discharged in response to a single discharge signal, and the presence or absence of a ligament with reference to the position of the discharge surface of the ink discharge head 2a detected by the discharge surface detector 104, by using a captured image of the ink droplet acquired by the imaging controller 109. Furthermore, the discharge calculator 106 detects, from the captured image, the number of times an ink droplet was discharged from the ink discharge head 2a for inspection. The discharge calculator 106 may calculate at least one of the speed, bend, and volume of the ink droplet with reference to the position of the discharge surface of the ink discharge head 2a.

[0081] The determination unit 107 is a functional unit that performs determination on a result of calculation performed by the discharge calculator 106. Specifically, the determination unit 107 determines whether each of the following calculated by the discharge calculator 106 is within an allowable range: the speed of the ink droplet, the bend of the ink droplet, the bend comparison value of the ink droplet for each nozzle, the volume of the ink droplet, the number of ink droplets discharged in response to a single discharge signal, and the presence or absence of a ligament. Furthermore, the determination unit 107 determines whether thenumber of times an ink droplet was discharged is correct, the number of times being detected by the discharge calculator 106. Here, the correct number of times an ink droplet was discharged refers to the number of times the ink discharge head 2a discharged ink according to an instruction from the discharge controller 202 of the controller unit 6.

[0082] The cleaning command unit 108 is a functional unit that transmits a command to cause the cleaning device 14 to clean the discharge surface of the ink discharge head 2a, to the controller unit 6 via the communicator 101.

[0083] The imaging controller 109 is a functional unit that controls the imaging operation of the camera 51 via the imaging UF 74.

[0084] The light source controller 110 is a functional unit that controls the light emitting operation of the light source 52 via the light source drive circuit 75.

[0085] The display controller 111 is a functional unit that transmits a display command to display predetermined information on the operation panel 15, to the controller unit 6 via the communicator 101.

[0086] Some or all of the communicator 101, the inspection controller 102, the pixel calculator 103, the discharge surface detector 104, the discharge command unit 105, the discharge calculator 106, the determination unit 107, the cleaning command unit 108, the imaging controller 109, the light source controller 110, and the display controller 111 may be implemented by a hardware circuit (integrated circuit) such as a field-programmable gate array (FPGA) or an application specific integrated circuit (ASIC) instead of a software program.

[0087] In addition, each functional unit of the inspection apparatus 50 is illustrated in FIG. 11 so as to conceptually illustrate a function thereof, so that the configuration of the inspection apparatus 50 is not limited to the configuration illustrated in FIG. 11. For example, a plurality of functional units illustrated as separate functional units in the inspection apparatus 50 illustrated in FIG. 11 may be configured as a single functional unit. Meanwhile, the function of a single functional unit in the inspection apparatus 50 illustrated in FIG. 11 may be divided into a plurality of functions such that the plurality of functions is performed by a plurality of functional units. In addition, each functional unit of the inspection apparatus 50 does not need to be configured as a definite software module as the block illustrated in FIG. 11 as long as the functions of the functional units are implemented as a whole as a result of execution of a program in the inspection apparatus 50.

[0088] As illustrated in FIG. 11, the controller unit 6 includes a communicator 201, a discharge controller 202, a movement controller 203, and a cleaning controller 204.

[0089] The communicator 201 is a functional unit that performs data communication with the inspection apparatus 50 via the I / F 63.

[0090] The discharge controller 202 is a functional unit that controls the ink discharge operation of the ink discharge head 2a via the unit control circuit 64.

[0091] The movement controller 203 is a functional unit that controls the reciprocating movement of the carriage 2, on which the ink discharge head 2a is mounted, in the main scanning direction and the sub-scanning direction by controlling the head moving mechanism 23 and the rail moving mechanism 24.

[0092] The cleaning controller 204 is a functional unit that controls the operation of cleaning the discharge surface of the ink discharge head 2a, performed by the cleaning device 14.

[0093] Note that some or all of the communicator 201, the discharge controller 202, the movement controller 203, and the cleaning controller 204 may be implemented by a hardware circuit (integrated circuit) such as an FPGA or an ASIC instead of a software program.

[0094] In addition, each functional unit of the controller unit 6 is illustrated in FIG. 11 so as to conceptually illustrate a function thereof, so that the configuration of the controller unit 6 is not limited to the configuration illustrated in FIG. 11. For example, a plurality of functional units illustrated as separate functional units in the controller unit 6 illustrated in FIG. 11 may be configured as a single functional unit. Meanwhile, the function of a single functional unit in the controller unit 6 illustrated in FIG. 11 may be divided into a plurality of functions such that the plurality of functions is performed by a plurality of functional units. In addition, each functional unit of the controller unit 6 does not need to be configured as a definite software module as the block illustrated in FIG. 11 as long as the functions of the functional units are implemented as a whole as a result of execution of a program in the controller unit 6.

[0095] In addition, at least some or all of the inspection controller 102, the pixel calculator 103, the discharge surface detector 104, the discharge command unit 105, the discharge calculator 106, the determination unit 107, the cleaning command unit 108, the imaging controller 109, the light source controller 110, and the display controller 111 of the control circuit 55 may be implemented by the controller unit 6.

[0096] Discharge Inspection Operation of Liquid Application ApparatusFIGS. 12A and 12B are flowcharts illustrating an exemplary flow of the discharge inspection operation of the liquid application apparatus according to the embodiment. The flow of the discharge inspection operation of the liquid application apparatus 1 according to the present embodiment will be described with reference to FIGS. 12A and 12B.

[0097] Step Si lThe controller unit 6 transmits, to the inspection apparatus 50, a start signal of the discharge inspection operation for inspecting an ink droplet discharged by the ink discharge head 2a, before starting printing of print data on the printing surface. Then, the inspection controller 102 of the inspection apparatus 50 receives the start signal via the communicator 101. As a result, the inspection apparatus 50 enters a state of execution of the discharge inspection operation. Then, the movement controller 203 of the controller unit 6 moves the carriage 2 in the main scanning direction to the inspection position for inspecting the flying state of an ink droplet discharged from the ink discharge head 2a. Specifically, the movement controller 203 moves the carriage 2 to the inspection position parallel to the discharge surface of the ink discharge head 2a. Furthermore, the movement controller 203 transmits a movement amount specified so as to instruct the carriage 2 to move to the inspection position, to the inspection apparatus 50 via the communicator 201. Then, the pixel calculator 103 of the inspection apparatus 50 acquires the movement amount via the communicator 101. Note that the movement controller 203 may transmit an actual movement amount detected by an encoder or the like to the inspection apparatus 50 via the communicator 201, instead of the movement amount specified as an instruction. Then, the process proceeds to step S12.

[0098] Step S 12The imaging controller 109 of the inspection apparatus 50 causes the camera 51 to capture an image of a state of the carriage 2 moving to the inspection position, by detecting the state as a luminance difference, and acquires the captured image. That is, the camera 51 captures an image by detecting a luminance difference due to a change in the position of the ink discharge head 2a relative to the camera 51. Here, detecting a luminance difference refers to detecting a luminance (intensity) change. At this time, the light source controller 110 of the inspection apparatus 50 causes the light source 52 to emit light while the camera 51 is performing imaging. Then, the discharge surface detector 104 of the inspection apparatus 50 detects the position of the discharge surface of the ink discharge head 2a of the carriage 2 from the captured image of the state of the carriage 2 moving to the inspection position, the captured image being acquired by the imaging controller 109. The exemplary flow illustrated in FIG. 12A assumes that the discharge surface detector 104 detects the position of the discharge surface of the ink discharge head 2a before discharge of an ink droplet for inspection. Meanwhile, the flow of the discharge inspection operation of the present embodiment is not limited thereto, and the discharge surface detector 104 may detect the position of thedischarge surface after discharge of an ink droplet for inspection. Then, the process proceeds to step S 13.

[0099] Step S 13The pixel calculator 103 calculates a pixel size which is an actual distance or length corresponding to a single pixel in an image captured by the camera 51 and acquired by the imaging controller 109. Specifically, the pixel calculator 103 calculates the number of pixels corresponding to the amount of movement of the carriage 2 in the image captured by the camera 51 and acquired by the imaging controller 109, based on the path of the discharge surface of the ink discharge head 2a detected by the discharge surface detector 104. Then, the pixel calculator 103 calculates the pixel size by dividing the acquired amount of movement of the carriage 2 to the inspection position by the calculated number of pixels. Note that the pixel size may be calculated in advance by the pixel calculator 103. Then, the process proceeds to step S14.

[0100] Step S 14The discharge command unit 105 of the inspection apparatus 50 transmits a command signal for providing an instruction for discharge of an ink droplet for inspection, to the controller unit 6 via the communicator 101. The discharge controller 202 of the controller unit 6 causes the ink discharge head 2a of the carriage 2 having stopped at the inspection position to discharge an ink droplet for inspection a predetermined number of times in response to the command signal received by the communicator 201. Furthermore, the imaging controller 109 causes the camera 51 to capture an image of a discharge state of the ink droplet discharged from the ink discharge head 2a, and acquires the captured image. At this time, the light source controller 110 of the inspection apparatus 50 causes the light source 52 to emit light while the camera 51 is performing imaging. Then, the process proceeds to step S15.

[0101] Step S 15The discharge calculator 106 of the inspection apparatus 50 calculates the speed of an ink droplet discharged for inspection from the ink discharge head 2a, the bend of the ink droplet, the bend comparison value of the ink droplet for each nozzle, the volume of the ink droplet, the number of ink droplets discharged in response to a single discharge signal, and the presence or absence of a ligament with reference to the position of the discharge surface of the ink discharge head 2a detected by the discharge surface detector 104, by using a captured image of the ink droplet acquired by the imaging controller 109. Then, the process proceeds to step S16.

[0102] Step S 16Furthermore, the discharge calculator 106 detects, from the captured image, the number of times an ink droplet was discharged from the ink discharge head 2a for inspection. Then, the process proceeds to step S17.

[0103] Step S 17The determination unit 107 of the inspection apparatus 50 determines whether each of the speed, bend, and volume of the ink droplet calculated by the discharge calculator 106 is within the allowable range. In a case where the speed of the ink droplet, the bend of the ink droplet, the bend comparison value of the ink droplet for each nozzle, the volume of the ink droplet, the number of ink droplets discharged in response to a single discharge signal, and the presence or absence of a ligament are each within the allowable range (step S17: Yes), the process proceeds to step S18, and in a case where at least one thereof is outside the allowable range (step S17: No), the process proceeds to step S20.

[0104] Step S 18Furthermore, the determination unit 107 determines whether the number of times an ink droplet was discharged is correct, the number of times being detected by the discharge calculator 106. In a case where the number of times an ink droplet was discharged is correct (step S18: Yes), the process proceeds to step S19, and in a case where the number of times an ink droplet was discharged is incorrect (step S18: No), the process proceeds to step S20.

[0105] Step S 19The inspection controller 102 transmits information to the effect that results of inspection of the flying state of the ink droplet are OK to the controller unit 6 via the communicator 101. When the controller unit 6 receives the information indicating OK, the controller unit 6 proceeds to a process of printing print data on the printing surface. Then, the discharge inspection operation is ended.

[0106] Step S20Furthermore, the determination unit 107 determines whether the number of times cleaning operation was performed by the cleaning device 14 in the discharge inspection operation is equal to or less than a predetermined number of times (for example, three times). When the number of times cleaning operation was performed is equal to or less than the predetermined number of times (step S20: Yes), the process proceeds to step S22, and when the number of times exceeds the predetermined number of times (step S20: No), the process proceeds to step S21.

[0107] Step S21The inspection controller 102 transmits information to the effect that the results of inspection of the flying state of the ink droplet are failure (“judged to be FAILURE” in FIG. 12B) to the controller unit 6 via the communicator 101. Then, the controller unit 6 causes the operation panel 15 to display the information to the effect that the inspection results are failure. Note that the display controller 111 of the inspection apparatus 50 may cause the operation panel 15 to display the information to the effect that the inspection results are failure. Then, the discharge inspection operation is ended.

[0108] Step S22The cleaning command unit 108 of the inspection apparatus 50 transmits a command to cause the cleaning device 14 to clean the discharge surface of the ink discharge head 2a, to the controller unit 6 via the communicator 101. Then, the cleaning controller 204 of the controller unit 6 causes the cleaning device 14 to clean the ink discharge head 2a in accordance with the cleaning command received by the communicator 201. Then, the process returns to step Si l.

[0109] As described above, in the inspection apparatus 50 according to the present embodiment, the camera 51 captures an image of the flying state of liquid discharged from the ink discharge head 2a by detecting the flying state as a luminance difference, and the discharge surface detector 104 detects the position of the discharge surface of the ink discharge head 2a in the captured image with the luminance difference that the camera 51 has detected by changing the position of the ink discharge head 2a relative to the camera 51. As a result, it is possible to reduce the calculation load, prevent an increase in the size of the inspection apparatus 50 and the liquid application apparatus 1, and detect the discharge surface of the ink discharge head 2a.

[0110] The configuration in which the inspection apparatus 50 is applied to the liquid application apparatus 1 that performs printing on a printing surface such as a road or a wall has been described in the above-described embodiment, but the configuration of the present embodiment is not limited thereto. For example, the liquid application apparatus 1 may be an inkjet printing apparatus that performs printing on a normal paper medium or the like. In addition, it is also possible to use the inspection apparatus 50 for inspecting the flying state of an ink droplet of an ink discharge head in a production process of the liquid application apparatus 1.

[0111] First ModificationA liquid application apparatus 1 according to a first modification of the present embodiment will be described focusing on differences from the liquid application apparatus 1 according to the present embodiment.

[0112] FIG. 13 is a diagram illustrating an exemplary configuration of an inspection apparatus according to the first modification of the embodiment. Configurations of the liquid application apparatus 1 and an inspection apparatus 50 according to the present modification will be described with reference to FIG. 13.

[0113] As illustrated in FIG. 13, the liquid application apparatus 1 according to the present modification further includes a vertical rail 16. Except for this point, the configuration of the liquid application apparatus 1 according to the present modification is the same as the configuration of the liquid application apparatus 1 according to the above-described embodiment.

[0114] The vertical rail 16 is a rail member that is supported by a rail 3 and movably supports a carriage 2 in a height direction (arrow C indicated in FIG. 13). That is, the carriage 2 moves in the main scanning direction together with the vertical rail 16 moved in the main scanning direction (arrow A indicated in FIG. 13) by a head moving mechanism 23. Thus, a movement controller 203 can reciprocate the carriage 2 on which an ink discharge head 2a is mounted, in the height direction. The movement in the height direction is performed in a case where, for example, a printing surface is not a flat surface but an uneven or inclined surface, so as to keep the ink discharge head 2a at a constant distance from a point on the printing surface to which an ink droplet is applied.

[0115] In the present modification, the movement controller 203 moves the carriage 2 in the height direction (that is, in a direction orthogonal to a discharge surface of the ink discharge head 2a) when the position of the discharge surface is detected by a discharge surface detector 104. That is, in this case, the camera 51 captures an image by detecting a luminance difference due to a change in the position of the ink discharge head 2a relative to the camera 51. The moving direction orthogonal to the discharge surface of the ink discharge head 2a is an example of “one predetermined direction” of the present embodiment. Even in this case, the position of the discharge surface of the ink discharge head 2a can be detected as an edge that causes a luminance difference, and the speed, bend, and the like of an ink droplet can be calculated with reference to the position. The movement controller 203 may be referred to also as “a mover”.

[0116] Second ModificationA liquid application apparatus 1 according to a second modification of the present embodiment will be described focusing on differences from the liquid application apparatus 1 according to the present embodiment.

[0117] FIG. 14 is a diagram illustrating an exemplary configuration of an inspection apparatus according to the second modification of the embodiment. A configuration of an inspection apparatus 50a according to the present modification will be described with reference to FIG.14.

[0118] For example, as illustrated in FIG. 14, a camera 51 of the inspection apparatus 50a according to the present modification can move in the main scanning direction (arrow A indicated in FIG. 14) and the height direction (arrow C indicated in FIG. 14). In this case, the camera 51 is moved in the main scanning direction and the height direction by a drive mechanism.

[0119] In the discharge inspection operation, instead of causing the camera 51 to image the state of a carriage 2 moving to an inspection position as in the above-described embodiment, an imaging controller 109 causes the camera 51 to perform imaging while the camera 51 is moving in a direction parallel or orthogonal to a discharge surface of an ink discharge head 2a in the present modification. That is, in this case, the camera 51 captures an image by detecting a luminance difference due to a change in the position of the ink discharge head 2a relative to the camera 51. Thus, the position of the discharge surface of the ink discharge head 2a can be detected as an edge that causes a luminance difference, and the speed, bend, and the like of an ink droplet can be calculated with reference to the position. Except for this point, the operation of the liquid application apparatus 1 is the same as the operation of the liquid application apparatus 1 according to the above-described embodiment.

[0120] Third ModificationA liquid application apparatus 1 according to a third modification of the present embodiment will be described focusing on differences from the liquid application apparatus 1 according to the present embodiment.

[0121] FIG. 15 is a diagram illustrating an exemplary configuration of an inspection apparatus according to the third modification of the embodiment. A configuration of an inspection apparatus 50b according to the present modification will be described with reference to FIG.15.

[0122] For example, as illustrated in FIG. 15, a camera 51 of the inspection apparatus 50b according to the present modification is movable in such a way as to rotate about an ink discharge direction of an ink discharge head 2a of a carriage 2 as a central axis, along a plane parallel to a discharge surface of the ink discharge head 2a. In this case, the camera 51 is rotationally moved by a drive mechanism.In the discharge inspection operation, instead of causing the camera 51 to image the state of the carriage 2 moving to an inspection position as in the above-described embodiment, an imaging controller 109 causes the camera 51 to perform imaging while the camera 51 is rotationally moving along the plane parallel to the discharge surface of the ink discharge head 2a with the ink discharge direction of the ink discharge head 2a as the central axis in the present modification. That is, in this case, the camera 51 captures an image by detecting a luminance difference due to a change in the position of the ink discharge head 2a relative to the camera 51. Thus, the position of the discharge surface of the ink discharge head 2a can be detected as an edge that causes a luminance difference, and the speed, bend, and the like of an ink droplet can be calculated with reference to the position. Except for this point, the operation of the liquid application apparatus 1 is the same as the operation of the liquid application apparatus 1 according to the above-described embodiment.

[0124] Fourth ModificationA liquid application apparatus 1 according to a fourth modification of the present embodiment will be described focusing on differences from the liquid application apparatus 1 according to the present embodiment.

[0125] FIG. 16 is a diagram for describing light emission operation of a light source in an inspection apparatus according to the fourth modification of the embodiment. Operation of an inspection apparatus 50 according to the present modification will be described with reference to FIG. 16.

[0126] In the present modification, when detecting the position of a discharge surface of an ink discharge head 2a, a light source controller 110 of the inspection apparatus 50 causes a light source 52 to emit light at a predetermined lighting rate (for example, 25%) via a light source drive circuit 75 as illustrated in FIG. 16. Thus, the position of the discharge surface of the ink discharge head 2a can be detected as an edge due to a luminance difference between a state in which the light source 52 is on and a state in which the light source is off, and the speed, bend, and the like of an ink droplet can be calculated with reference to the position. Except for this point, the operation of the liquid application apparatus 1 is the same as the operation of the liquid application apparatus 1 according to the above-described embodiment.

[0127] Fifth ModificationA liquid application apparatus 1 according to a fifth modification of the present embodiment will be described focusing on differences from the liquid application apparatus 1 according to the present embodiment.

[0128] FIG. 17 is a diagram illustrating an exemplary configuration of an inspection apparatus according to the fifth modification of the embodiment. A configuration of an inspection apparatus 50c according to the present modification will be described with reference to FIG. 17.

[0129] A camera 51 of the inspection apparatus 50c according to the present modification can vibrate as illustrated in, for example, FIG. 17.

[0130] In the discharge inspection operation, instead of causing the camera 51 to image the state of a carriage 2 moving to an inspection position as in the above-described embodiment, an imaging controller 109 causes the camera 51 to perform imaging while the camera 51 is vibrating in the present modification. That is, in this case, the camera 51 captures an image by detecting a luminance difference due to a change in the position of an ink discharge head 2a relative to the camera 51 caused by vibration. Thus, it is possible to detect the position of the discharge surface of the ink discharge head 2a as an edge by causing a luminance difference by vibration, and the speed, bend, and the like of an ink droplet can be calculated with reference to the position. Except for this point, the operation of the liquid application apparatus 1 is the same as the operation of the liquid application apparatus 1 according to the above-described embodiment.

[0131] When at least one of the functions of the liquid application apparatus 1 and the inspection apparatuses 50 and 50a to 50c is implemented by execution of a program in the abovedescribed embodiment and modifications, the program is provided by being stored in advance in a ROM or the like. Furthermore, in the above-described embodiment and modifications, programs to be executed in the liquid application apparatus 1 and the inspection apparatuses 50 and 50a to 50c may each be provided by being recorded, as a file in an installable format or an executable format, in a computer-readable recording medium such as a compact disc read only memory (CD-ROM), a flexible disk (FD), a compact disk-recordable (CD-R), or a digital versatile disc (DVD). Furthermore, in the above-described embodiment and modifications, the programs to be executed in the liquid application apparatus 1 and the inspection apparatuses 50 and 50a to 50c may be stored on a computer connected to a network such as the Internet and provided by being downloaded via the network. Furthermore, in the above-described embodiment and modifications, the programs to be executed in the liquid application apparatus 1 and the inspection apparatuses 50 and 50a to 50c may be provided or distributed via a network such as the Internet. Furthermore, in the above-described embodiment and modifications, the program to be executed in each of the liquid application apparatus 1 and the inspection apparatuses 50 and 50a to 50c has a module configuration including at least one of the above-described functional units, and the CPU reads the programfrom the above-described storage device and executes the program to load and generate the above-described functional units on a main storage device as actual hardware.The functionality of the elements disclosed herein may be implemented using circuitry or processing circuitry which includes general purpose processors, special purpose processors, integrated circuits, application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), and / or combinations thereof which are configured or programmed, using one or more programs stored in one or more memories, to perform the disclosed functionality. Processors are considered processing circuitry or circuitry as they include transistors and other circuitry therein. In the disclosure, the circuitry, units, or means are hardware that carry out or are programmed to perform the recited functionality. The hardware may be any hardware disclosed herein which is programmed or configured to carry out the recited functionality.There is a memory that stores a computer program which includes computer instructions. These computer instructions provide the logic and routines that enable the hardware (e.g., processing circuitry or circuitry) to perform the method disclosed herein. This computer program can be implemented in known formats as a computer-readable storage medium, a computer program product, a memory device, a record medium such as a CD-ROM or DVD, and / or the memory of an FPGA or ASIC.

[0132] Aspects of the present embodiment are as follows.First AspectAccording to a first aspect, an inspection apparatus for inspecting a discharge state of liquid discharged from a discharge head of a liquid discharge apparatus, the discharge head including one or more nozzles, includes: an imager that captures an image by detecting, as a luminance change, a discharge state of liquid discharged from the discharge head; and a detection unit that detects a position of a discharge surface of the discharge head in a captured image with a luminance change that the imager has detected by changing a position of the discharge head relative to the imager.Second AspectAccording to a second aspect, the inspection apparatus of the first aspect further includes a calculation unit that calculates at least one of a speed of a droplet discharged from the discharge head, a bend of the droplet, a bend comparison value of the droplet for each nozzle, a volume of the droplet, a number of droplets discharged in response to a single discharge signal, and presence or absence of a ligament by using an image of the discharge state with reference to the position of the discharge surface detected by the detection unit, the image of the discharge state being captured by the imager.Third AspectAccording to a third aspect, in the inspection apparatus of the second aspect, the detection unit detects the position of the discharge surface at a same timing as discharge of liquid from the discharge head.Fourth AspectAccording to a fourth aspect, in the inspection apparatus of any one of the first to third aspects, the discharge head is movable in at least one predetermined direction, and the detection unit detects the position of the discharge surface in an image captured by the imager while the discharge head is moving in the one direction.Fifth AspectAccording to a fifth aspect, in the inspection apparatus of the fourth aspect, the discharge head is movable parallel to the discharge surface, and the detection unit detects the position of the discharge surface in an image captured by the imager while the discharge head is moving parallel to the discharge surface.Sixth AspectAccording to a sixth aspect, in the inspection apparatus of the fourth aspect, the discharge head is movable in a direction orthogonal to the discharge surface, and the detection unit detects the position of the discharge surface in an image captured by the imager while the discharge head is moving in the direction orthogonal to the discharge surface.Seventh AspectAccording to a seventh aspect, in the inspection apparatus of any one of the first to third aspects, the imager is movable in at least one predetermined direction, and the detection unit detects the position of the discharge surface in an image captured by the imager while the imager is moving in the one direction.Eighth AspectAccording to an eighth aspect, in the inspection apparatus of any one of the first to third aspects, the imager is movable in such a way as to rotate about a liquid discharge direction of the discharge head as a central axis, along a plane parallel to the discharge surface, andthe detection unit detects the position of the discharge surface in an image captured by the imager during the rotational movement of the imager.Ninth AspectAccording to a ninth aspect, in the inspection apparatus of any one of the first to third aspects, the imager can vibrate, and the detection unit detects the position of the discharge surface in an image captured by the imager while the imager is vibrating.Tenth AspectAccording to a tenth aspect, the inspection apparatus of any one of the first to ninth aspects, further includes a light source facing the imager, the light source being disposed on a side opposite to the imager with respect to the discharge head in a case where the discharge head is imaged by the imager, in which the light source emits light in a case where an image is captured by the imager. Eleventh AspectAccording to an eleventh aspect, in the inspection apparatus of the tenth aspect, the light source emits light at a predetermined lighting rate in a case where an image is captured by the imager for detection of the position of the discharge surface by the detection unit.Twelfth AspectAccording to a twelfth aspect, in the inspection apparatus of any one of the first to eleventh aspects, the imager captures an image via a telecentric lens.Thirteenth AspectAccording to a thirteenth aspect, the inspection apparatus of any one of the first to twelfth aspects further includes a discharge receiver fixed at a position immediately below the discharge head when a discharge state of liquid discharged from the discharge head is inspected.Fourteenth AspectAccording to a fourteenth aspect, a liquid discharge apparatus includes: the discharge head that discharges liquid; and the inspection apparatus of any one of the first to thirteenth aspects.The above-described embodiments are illustrative and do not limit the present invention. Thus, numerous additional modifications and variations are possible in light of the above teachings. For example, elements and / or features of different illustrative embodiments may be combined with each other and / or substituted for each other within the scope of the present invention. Any one of the above-described operations may be performed in various other ways, for example, in an order different from the one described above.This patent application is based on and claims priority to Japanese Patent Application No. 2024-006256, filed on January 18, 2024, in the Japan Patent Office, and Japanese PatentApplication No. 2024-147940, filed on August 29, 2024, in the Japan Patent Office, the entire disclosure of which is hereby incorporated by reference herein.[Reference Signs List]

[0133] 1 liquid application apparatus2 carriage2a ink discharge head3 rail4 ink supply system4a pipe5 power supply system6 controller7 three-dimensional camera8 two-dimensional camera9 GNSS receiver10 tire11 frame12 structure13 maintenance unit14 cleaning device15 operation panel16 vertical rail21 printing unit22 control unit23 head moving mechanism24 rail moving mechanism50, 50a to 50c inspection apparatus51 camera51a optical system52 light source53 dummy discharge receiver54 frame55 control circuit61 CPU62 memory63 VF64 unit control circuit71 CPU72 memory73 I / F74 imaging I / F75 light source drive circuit101 communicator102 inspection controller103 pixel calculator104 discharge surface detector105 discharge command unit106 discharge calculator107 determination unit108 cleaning command unit109 imaging controller110 light source controller111 display controller201 communicator202 discharge controller203 movement controller204 cleaning controllerBIMI to BIM3 captured imagePAR print area[Citation List][Patent Literature]

[0134] [PTL 1]Japanese Unexamined Patent Application Publication No. 10-206624

Claims

[CLAIMS]

1. A liquid discharge apparatus comprising: a controller configured to control a discharge head having a discharge surface that has a nozzle to discharge a liquid from the nozzle; an imager to capture an image of the liquid discharged from the nozzle, as a luminance change, to detect a discharge state of the discharge head; a mover to move one of the discharge head or the imager relative to each other in one direction; a detector to detect a position of the discharge surface of the discharge head in the image with the luminance change imaged by the imager; and a determination unit to determine the discharge state of the discharge head based on the position of the discharge surface and the discharge state of the liquid discharged from the nozzle, wherein the imager captures an image of the discharge surface while the mover moves the one of the discharge head or the imager to change the position of the discharge surface relative to the imager in the one direction.

2. The liquid discharge apparatus according to claim 1, further comprising a calculator to calculate at least one of: a speed of a droplet discharged from the discharge head; a bend of the droplet; a bend comparison value of the droplet for each nozzle; a volume of the droplet; a number of droplets discharged in response to a single discharge signal; or a presence or an absence of a ligament, with reference to the position of the discharge surface detected by the detector by using the image of the discharge surface captured by the imager.

3. The liquid discharge apparatus according to claim 2, wherein the detector detects the position of the discharge surface when the discharge head discharges the liquid.

4. The liquid discharge apparatus according to any one of claims 1 to 3, wherein the detector detects the position of the discharge surface in the image of the discharge surface captured by the imager while the mover moves the discharge head in the one direction.

5. The liquid discharge apparatus according to claim 4,wherein the detector detects the position of the discharge surface in the image of the discharge surface captured by the imager while the mover moves the discharge head parallel to the discharge surface in the one direction.

6. The liquid discharge apparatus according to claim 4, wherein the detector detects the position of the discharge surface in the image of the discharge surface captured by the imager while the mover moves the discharge head in the one direction orthogonal to the discharge surface.

7. The liquid discharge apparatus according to any one of claims 1 to 3, wherein the discharge head discharges the liquid in another direction intersecting the one direction, and the detector detects the position of the discharge surface in the image of the discharge surface captured by the imager while the mover moves the imager in the one direction.

8. The liquid discharge apparatus according to any one of claims 1 to 3, wherein the discharge head discharges the liquid in another direction intersecting the one direction, the detector detects the position of the discharge surface in the image of the discharge surface captured by the imager while the mover rotates the imager about said another direction as a central axis along a plane parallel to the discharge surface.

9. The liquid discharge apparatus according to any one of claims 1 to 3, wherein the imager includes a vibrator to vibrates the imager, and the detector detects the position of the discharge surface in the image of the discharge surface captured by the imager while the vibrator vibrates the imager.

10. The liquid discharge apparatus according to any one of claims 1 to 3, further comprising: a light source facing the imager, wherein the light source is disposed on an opposite side of the imager with the discharge head in between and emits light, when the imager captures an image of the discharge head.

11. The liquid discharge apparatus according to claim 10, wherein the light source emits light at a predetermined lighting rate when the detector detects the position of the discharge surface.

12. The liquid discharge apparatus according to any one of claims 1 to 3,wherein the imager includes a telecentric lens to capture an image.

13. The liquid discharge apparatus according to any one of claims 1 to 3, further comprising: a discharge receiver fixed at a position immediately below the discharge head at the discharge state to discharge the liquid.

14. The liquid discharge apparatus according to any one of claims 1 to 3, further comprising the discharge head to discharge the liquid.

Images