Inkjet head monitoring apparatus and method

Abstract

An inkjet head monitoring apparatus, according to an embodiment of the present invention, relates to an inkjet head monitoring apparatus of an inkjet printing system comprising an inkjet head for ejecting ink droplets, a motion stage for moving the inkjet head, a light source device for irradiating light onto the ink droplets, and a camera for acquiring images of the ink droplets, and the inkjet head monitoring apparatus may comprise: a motion stage controller for periodically generating an encoder signal and moving the motion stage at a constant speed without stopping; an inkjet head controller for periodically generating an ejection signal that causes the inkjet head to eject ink droplets; a light source device controller for generating a flash signal for turning the light source device on and off with a predetermined delay from the time point at which the ejection signal is generated; and a camera controller for generating a trigger pulse signal on the basis of the encoder signal and the flash signal and determines camera exposure start time on the basis of the trigger pulse signal.

Description

Inkjet head monitoring device and method

[0001] The present invention relates to a device and method for monitoring an inkjet head.

[0002] Inkjet printing technology is a technology that deposits ink by spraying tiny droplets onto a workpiece such as a substrate. Its application range is expanding beyond office inkjet printers to various industrial fields such as semiconductors, displays, and medicine, and its usability is increasing day by day.

[0003] Inkjet heads used in industrial inkjet printing systems contain hundreds to thousands of microscopic nozzles for high productivity. However, not all nozzles are in good condition, and some abnormal nozzles can cause serious printing defects. Research is ongoing into monitoring technologies for inkjet head inspection to detect these ejection defects.

[0004] Inkjet head monitoring devices primarily use vision inspection to capture images of ink droplets being ejected from an inkjet head, and use this to inspect whether the inkjet head is operating normally. Conventional vision inspection methods primarily sequentially inspect multiple nozzles included in an inkjet head by separately operating the movement of a motion stage and the image capturing process for inspection, and using a method of capturing images of ink droplets ejected through the nozzles while the motion stage is stationary. However, this method has the problem of taking a lot of time during the inspection process due to the repetitive movement and stopping of the motion stage, which soon causes delays in the entire process.

[0005] In order to solve the above-mentioned problem, the present invention provides an inkjet head monitoring device and method that can acquire images of ink droplets ejected from each inkjet head while the motion stage is moving, thereby eliminating the need for stopping the motion stage during inspection.

[0006] An inkjet head monitoring device according to one embodiment of the present invention relates to an inkjet head monitoring device of an inkjet printing system including an inkjet head that ejects ink droplets, a motion stage that moves the inkjet head, a light source device that irradiates light to the ink droplets, and a camera that acquires an ink droplet image, and may include a motion stage control unit that periodically generates an encoder signal and moves the motion stage at a constant speed without stopping, an inkjet head control unit that periodically generates a spray signal that causes the inkjet head to eject ink droplets, a light source device control unit that generates a blinking signal that blinks the light source device with a constant delay from the time of generation of the spray signal, and a camera control unit that generates a trigger pulse signal based on the encoder signal and determines a camera exposure start time based on the trigger pulse signal.

[0007] Additionally, according to one embodiment, the camera control unit may be characterized in that it generates a trigger pulse signal with the starting point of the encoder signal as a rising point and the starting point of the flashing signal or the injection signal as a falling point.

[0008] Additionally, according to one embodiment, the camera control unit may be characterized in that it determines the falling point of the trigger pulse signal as the camera exposure start point.

[0009] Additionally, according to one embodiment, the camera control unit may be characterized by selecting some encoder signals from among the encoder signals based on preset criteria and generating a trigger pulse signal based on the selected some encoder signals.

[0010] Additionally, according to one embodiment, the camera control unit may be characterized by selecting a first encoder signal at each preset sampling period among the encoder signals.

[0011] Additionally, according to one embodiment, the camera control unit may be characterized in that it sets the sampling cycle based on the nozzle spacing of the inkjet head and the constant speed of the motion stage.

[0012] Additionally, according to one embodiment, the light source device control unit may be characterized in that it generates a blinking signal based only on some of the injection signals that are first generated after some of the selected encoder signals.

[0013] Additionally, according to one embodiment, the camera control unit may be characterized by setting the exposure time of the camera to be longer than the blinking time of the light source device and shorter than the jetting cycle of the inkjet head.

[0014] Additionally, in one embodiment, the light source device control unit may be characterized by generating a blink signal twice within the time that the camera is exposed.

[0015] Additionally, according to one embodiment, the camera control unit may be characterized in that it determines the point in time at which the flashing of the light source device ends as the point in time at which the camera exposure ends.

[0016] A method for monitoring an inkjet head according to another embodiment of the present invention relates to a method for monitoring an inkjet head of an inkjet printing system including an inkjet head for ejecting ink droplets, a motion stage for moving the inkjet head, a light source device for irradiating light on the ink droplets, and a camera for acquiring an image of the ink droplets, the method including a motion stage control step for periodically generating an encoder signal in a motion stage control unit and moving the motion stage at a constant speed without stopping, an inkjet head control step for periodically generating an ejection signal for ejecting ink droplets from the inkjet head in the inkjet head control unit, a light source device control step for generating a blinking signal for blinking the light source device with a constant delay from the time of generation of the ejection signal in a light source device control unit, and a camera control step for generating a trigger pulse signal based on the encoder signal in a camera control unit and determining a camera exposure start time based on the trigger pulse signal.

[0017] Additionally, according to one embodiment, the camera control step may be characterized by generating a trigger pulse signal with the starting point of the encoder signal as a rising point and the starting point of the flashing signal or injection signal as a falling point.

[0018] Additionally, according to one embodiment, the camera control step may be characterized by determining the falling point of the trigger pulse signal as the camera exposure start point.

[0019] Additionally, according to one embodiment, the camera control step may be characterized by selecting some encoder signals from among the encoder signals based on preset criteria and generating a trigger pulse signal based on the selected some encoder signals.

[0020] Additionally, according to one embodiment, the camera control step may be characterized by selecting a first encoder signal at each preset sampling period among the encoder signals.

[0021] Additionally, according to one embodiment, the camera control step may be characterized by setting a sampling cycle based on a gap between nozzles of the inkjet head and a constant speed of the motion stage.

[0022] Additionally, according to one embodiment, the light source device control step may be characterized by generating a blinking signal based only on some of the injection signals that are first generated after some of the selected encoder signals.

[0023] Additionally, according to one embodiment, the camera control step may be characterized by setting the exposure time of the camera to be longer than the blinking time of the light source device and shorter than the jetting cycle of the inkjet head.

[0024] Additionally, in one embodiment, the light source device control step may be characterized by generating a blink signal twice within the time that the camera is exposed.

[0025] Additionally, according to one embodiment, the camera control step may be characterized by determining the point in time at which the flashing of the light source device ends as the camera exposure end point.

[0026] The inkjet head monitoring device and method of the present invention can significantly improve the speed of inkjet head inspection by acquiring images of ink droplets ejected from each inkjet head while the motion stage is moving, thereby minimizing waste of expensive ink and labor costs required during the inspection process and accelerating the manufacturing process.

[0027] Figure 1 is a schematic diagram of an inkjet printing system according to one embodiment.

[0028] FIG. 2 is a block diagram of an inkjet head monitoring device according to one embodiment.

[0029] FIG. 3 is a schematic diagram of a speed profile and encoder signal of a motion stage according to one embodiment.

[0030] Figure 4 is a schematic diagram of a spray signal and a flashing signal according to one embodiment.

[0031] FIG. 5 is a schematic diagram of a trigger pulse signal and camera exposure start and end times according to one embodiment.

[0032] Figures 6 and 7 are schematic diagrams showing signals of each control unit according to an embodiment.

[0033] Figure 8 is an image captured by a camera according to an exposure time according to one embodiment.

[0034] Figures 9 to 11 are schematic diagrams showing signals of each control unit according to an embodiment.

[0035] Figure 12 is a flowchart of the operation of each control unit according to one embodiment.

[0036] Figure 13 is a flowchart of an inkjet head monitoring method according to one embodiment.

[0037] The advantages and features of the present invention, and the methods for achieving them, will become clearer with reference to the embodiments described below together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and may be implemented in various different forms. These embodiments are provided solely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined solely by the scope of the claims.

[0038] The terms used in this specification will be briefly explained, and the present invention will be described in detail.

[0039] The terms used in this invention have been selected from widely used, current terms, taking into account the functions of the invention. However, these terms may vary depending on the intentions of those skilled in the art, precedents, the emergence of new technologies, etc. Furthermore, in certain cases, terms may be arbitrarily selected by the applicant, in which case their meanings will be described in detail in the relevant description of the invention. Therefore, the terms used in this invention should not be defined simply as names, but rather based on their inherent meanings and the overall content of the invention.

[0040] When a part of the specification is said to "include" a component, this does not mean that other components are excluded, but rather that other components may be included, unless otherwise specifically stated. Furthermore, terms such as "part," "module," and "unit" used in the specification mean a unit that processes at least one function or operation, and may be implemented by software, a hardware component such as an FPGA or ASIC, or a combination of software and hardware. However, terms such as "part," "module," and "unit" are not limited to software or hardware. A "part," "module," and "unit" may be configured to reside on an addressable storage medium, or may be configured to execute one or more processors. Thus, as an example, terms such as "part," "module," "unit," etc., include components such as software components, object-oriented software components, class components, and task components, as well as processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays, and variables.

[0041] Below, with reference to the attached drawings, embodiments of the present invention are described in detail so that those skilled in the art can easily practice them. Furthermore, in order to clearly explain the present invention, portions irrelevant to the description are omitted in the drawings.

[0042] Terms including ordinal numbers, such as "first," "second," etc., may be used to describe various components, but the components are not limited by the terms. The terms are used solely to distinguish one component from another. For example, without departing from the scope of the present invention, the first component could be referred to as the second component, and similarly, the second component could also be referred to as the first component. The term "and / or" includes any combination of multiple related items or any one of multiple related items.

[0043]

[0044] Hereinafter, the inkjet head monitoring device and method of the present invention will be described.

[0045] The inkjet head monitoring device of the present invention relates to a device for monitoring an inkjet head of an inkjet printing system, and unlike conventional inkjet head monitoring technology, it can monitor ink droplets sprayed from an inkjet head by capturing images of the ink droplets without stopping the motion stage during the inkjet printing process.

[0046]

[0047] Referring to Fig. 1, an inkjet printing system (1) will be described.

[0048] FIG. 1 is a schematic diagram of an inkjet printing system (1) including an inkjet head monitoring device (10) of the present invention.

[0049] Referring to FIG. 1, an inkjet printing system (1) according to one embodiment may include an inkjet head monitoring device (10) of the present invention and other inkjet printing configurations. Specifically, the inkjet printing system (1) may include an inkjet head (20) that ejects ink droplets, a motion stage (30) that moves the inkjet head (20), a light source device (40) that irradiates light onto the ink droplets, a camera (50) that acquires images of the ink droplets, an ink supply device (60) that supplies ink to the inkjet head (20), and an inkjet monitoring device for inspecting the inkjet head (20). The inkjet printing system (1) may include various configurations in addition to the configurations described above.

[0050] The inkjet head (20) can eject ink droplets through nozzles. The inkjet head (20) may be a multi-nozzle inkjet head (20) in which a plurality of small nozzles having fine holes for ejecting ink droplets are assembled. The inkjet head (20) can be operated by an ejection signal, which will be described later, to eject ink droplets through the nozzles.

[0051] In one embodiment, the nozzles included in the inkjet head (20) may be arranged in a row at regular intervals. Furthermore, the nozzles arranged in a row may be distributed across multiple columns. For example, 256 nozzles may be arranged in a row at regular intervals.

[0052] The jetting performance of the inkjet head (20) can be determined based on various criteria. For example, the jetting performance of the inkjet head (20) can be determined based on criteria such as the speed at which ink droplets are jetted, the trajectory, and the volume of the jetted ink droplets.

[0053] In one embodiment, the inkjet head (20) can have its internal negative pressure controlled so that ink does not leak from the inkjet head (20) (or nozzle) according to a command from a control unit described later. In one embodiment, this process may be performed by an ink supply device (60) described later.

[0054] The inkjet head (20) can be moved during inkjet printing operation. The inkjet head (20) is physically connected to a motion stage (30) to be described later, and can be moved in the same manner as the motion stage (30) moves.

[0055] The motion stage (30) is a device used to control the movement of the inkjet head (20) and can move the inkjet head (20). The motion stage (30) is physically connected to the inkjet head (20) and can adjust the position of the inkjet head (20) by adjusting the position of the motion stage (30) itself. For example, the motion stage (30) can move so that the inkjet head (20) can be positioned at a target point according to a command for adjusting the position of the inkjet head (20).

[0056] The motion stage (30) can control the movement speed of the inkjet head (20). The motion stage (30) can increase or decrease the movement speed of the inkjet head (20) or maintain a constant speed by controlling its own movement speed.

[0057] In inkjet printing technology, it is very important to control the movement of the inkjet head (20) to spray ink droplets at an accurate location, so the motion stage (30) can finely adjust the position of the inkjet head (20) and precisely control the speed of the movement.

[0058] In one embodiment, the motion stage (30) is also physically connected to a camera (50) and a light source device (40) to control the movement of these components.

[0059] The camera (50) can acquire an image of an ink droplet. The camera (50) can be positioned to capture the image of an ink droplet falling, and the direction of the lens can be adjusted to the direction in which the inkjet head (20) and the path along which the ink droplet falls exist.

[0060] The camera (50) can capture images of ink droplets being sprayed and falling by taking pictures of the inkjet head (20) and / or ink droplets according to control. The camera (50) can start and end exposure of the lens according to the determination of the start and end points of exposure of the camera (50), and can capture images of the inkjet head (20) and ink droplets while the lens is exposed.

[0061] The ink droplets and the inkjet head (20) that sprays them are very small in size, and it is desirable that the camera (50) to obtain an image thereof have the performance to be able to capture images of very small sizes.

[0062] The camera (50) can be a scan camera (50) capable of high-speed shooting, but is not limited thereto, and a camera (50) used in the monitoring technology of a general inkjet head (20) can be utilized without limitation.

[0063] The light source device (40) can irradiate light so that the camera (50) can clearly capture the sprayed ink droplets when photographing them. The light source device (40) can be positioned at a point where light can be irradiated onto the sprayed ink droplets and can be directed toward the ink droplets.

[0064] The light source device (40) can irradiate light by a blinking signal to be described later.

[0065] The light source device (40) can be controlled to emit light for a controlled period of time. The light source device (40) can emit light to the ink droplet for a very short period of time to minimize motion blur in the image. In an embodiment, the light source device (40) can emit light for a period of time in nanoseconds (ns).

[0066] The light source device (40) can utilize a strobe LED, but is not limited thereto, and a light source device (40) used in the monitoring technology of a general inkjet head (20) can be utilized without limitation.

[0067] The ink supply device (60) can supply ink to the inkjet head (20). The ink supply device (60) can continuously supply ink to the inkjet head (20) using a water level difference or a pump so that the ink is not insufficient, and is not limited thereto, and an ink supply device (60) used in a general inkjet printing system (1) can be utilized without limitation. In addition, according to one embodiment, the ink supply device (60) can maintain a meniscus shape of the ink in the nozzle by controlling the negative pressure inside the inkjet head (20) using a vacuum pump, and can prevent the ink from leaking.

[0068] In one embodiment, the ink supply device (60) may be configured as an integrated unit with the inkjet head (20).

[0069] In addition to the aforementioned configuration, the inkjet printing system (1) of the present invention may further include various configurations necessary for inkjet printing. For example, the inkjet printing system (1) may further include a PC (not shown) for information processing, an input device (not shown) for inputting information and commands, and an output device (not shown) for displaying processing results to a user. Here, the input device may include a mouse, a keyboard, a touchpad, etc., and the output device may include a display, a speaker, etc.

[0070] Each component, including the inkjet head monitoring device (10) of the inkjet printing system (1), can transmit or receive data and / or commands through communication between each component. Each component can be provided with a separate transmission / reception device for communication, through which data and / or commands can be transmitted and received.

[0071]

[0072] Hereinafter, an inkjet head monitoring device (10) according to one embodiment of the present invention will be described.

[0073] The inkjet head monitoring device (10) can transmit data and / or commands to each component of the inkjet printing system (1), or receive results obtained by each component executing a command. For example, the inkjet head monitoring device (10) can transmit a command to the inkjet head (20) to eject ink droplets, and can transmit a command to the motion stage (30) to move the inkjet head (20) at a set speed. In addition, the inkjet head monitoring device (10) can transmit a command to the camera (50) and the light source device (40) to irradiate light on the ink droplets ejected from the inkjet head (20) and photograph them.

[0074] The inkjet head monitoring device (10) can periodically generate an encoder signal and move the motion stage (30) at a constant speed without stopping. In addition, the inkjet head monitoring device (10) can periodically generate an ejection signal to eject ink droplets from the inkjet head (20). In addition, the inkjet head monitoring device (10) can generate a blinking signal to blink the light source device (40) with a constant delay from the time of generation of the ejection signal. In addition, the inkjet head monitoring device (10) can generate a trigger pulse signal based on the encoder signal and determine the camera (50) exposure start time based on the trigger pulse signal.

[0075] Fig. 2 is a block diagram of an inkjet head monitoring device (10).

[0076] The inkjet head monitoring device (10) may include a receiving unit (110), a storage unit (120), a transmitting unit (130), and a processor (140).

[0077] The receiving unit (110) can receive various pieces of information necessary for monitoring the inkjet head (20). The receiving unit (110) can receive data and / or commands through communication with various components included in the inkjet printing system (1). For example, the receiving unit (110) can receive an ink droplet image captured by a camera (50), position information of the inkjet head (20), speed information of the motion stage (30), etc.

[0078] In addition, the receiving unit (110) can receive data and / or commands from outside the inkjet printing system (1) via communication. For example, the receiving unit (110) can receive input data and / or commands, etc., through a user's input device.

[0079] The storage unit (120) can store various data and / or commands required for monitoring the inkjet head (20). The storage unit (120) can receive and store various data and commands received or generated during the inkjet head (20) monitoring process, and can transmit the stored data to other components.

[0080] The storage unit (120) may include at least one of a main memory device and an auxiliary memory device. The main memory device may be implemented using a semiconductor storage medium such as, for example, ROM and / or RAM, and the auxiliary memory device may be implemented based on a device capable of permanently or semi-permanently storing data, such as a flash memory device (such as a solid state drive (SSD)), a Secure Digital (SD) card, a hard disk drive (HDD), a compact disc, a DVD, or a laser disc.

[0081] The transmitter (130) can transmit various data generated during the inkjet head (20) monitoring process to other components of the inkjet printing system (1). The transmitter (130) can receive data and / or commands stored in the processor (140) and / or the storage (120) and transmit them to components other than the inkjet head monitoring device (10) (camera (50), motion stage (30), etc.). For example, the transmitter (130) can transmit a spray signal to the inkjet head (20) and a blinking signal to the light source device (40).

[0082] In addition, the transmitter (130) can transmit data and / or commands to the outside of the inkjet printing system (1) via communication. For example, the transmitter (130) can transmit an image received from a camera (50) to an output device.

[0083] The processor (140) can receive data and / or commands from the receiving unit (110) and / or the storage unit (120), process them, and then transmit the resulting results to the storage unit (120) and / or the transmitting unit (130).

[0084] According to an embodiment, the processor (140) may include one or more of a central processing unit (CPU), a graphic processing unit (GPU), a microcontroller unit (MCU), an application processor (AP), an electronic control unit (ECU), a microprocessor (Micom), or at least one other electronic device capable of performing various calculations and control processing. These processing or control devices may be implemented by using, for example, one or more semiconductor chips, circuits, or related components, either singly or in combination.

[0085] The processor (140) can periodically generate an encoder signal and move the motion stage (30) at a constant speed without stopping. In addition, the processor (140) can periodically generate an ejection signal to eject ink droplets from the inkjet head (20). In addition, the processor (140) can generate a blinking signal to blink the light source device (40) with a constant delay from the time of generation of the ejection signal. In addition, the processor (140) can generate a trigger pulse signal based on the encoder signal and determine the camera (50) exposure start time based on the trigger pulse signal.

[0086] The processor (140) may perform all of the aforementioned processes, depending on the embodiment, or may perform only some of them, or may perform additional processes. To perform these operations, a program pre-stored in the storage unit (120) or the like may be utilized. The program may be directly written by a designer or the like, or may be acquired or updated through an electronic software distribution network.

[0087] The processor (140) may include a motion stage control unit (1410), an inkjet head control unit (1430), a light source device control unit (1450), and a camera control unit (1470).

[0088] Referring to FIG. 3, the motion stage control unit (1410) will be described.

[0089] FIG. 3 is a schematic diagram of a velocity profile and encoder signal of a motion stage (30) according to one embodiment.

[0090] The motion stage control unit (1410) can periodically generate an encoder signal and move the motion stage (30) at a constant speed without stopping.

[0091] The motion stage control unit (1410) can generate an encoder signal having a constant cycle (c1). Referring to FIG. 3, the motion stage control unit (1410) of the present invention starts generating an encoder signal simultaneously with the movement of the motion stage (30), and can continue to generate the signal until the movement of the motion stage (30) ends at a constant cycle (c1). Here, the constant cycle (c1) may be a cycle set in advance according to the needs of inkjet printing.

[0092] The motion stage control unit (1410) can move the motion stage (30). Specifically, the motion stage control unit (1410) can control the movement of the motion stage (30) by generating a command to move the motion stage (30) and transmitting the command to the motion stage (30). Under the control of the motion stage control unit (1410), the motion stage (30) can accelerate until it reaches a preset speed, and once it reaches the speed, it can move while maintaining the speed. Thereafter, the motion stage (30) can move at a constant speed without acceleration or deceleration according to the command of the motion stage control unit (1410). Here, the constant speed may be a speed preset for optimal inkjet printing.

[0093] Unlike the conventional inkjet head (20) monitoring technology that repeatedly stops the motion stage (30) to capture an image of an ink droplet during the inkjet head (20) inspection process, the inkjet head monitoring device (10) of the present invention can acquire an image of an ink droplet while the motion stage (30) moves at a constant speed without stopping during the inspection process.

[0094] According to one embodiment, the motion stage control unit (1410) can move the motion stage (30) after the injection signal to be described later. It is preferable that the motion stage control unit (1410) start moving the motion stage (30) after a certain delay time after the injection signal is generated from the inkjet head control unit (1430) to be described later. This may be because it is preferable to move the inkjet head (20) after the injection signal starts. However, the point in time at which the motion stage (30) moves is not limited thereto, and it may be determined regardless of the injection point in time of the inkjet head (20).

[0095] Referring to FIG. 4, the inkjet head control unit (1430) and the light source device control unit (1450) will be described.

[0096] Figure 4 is a schematic diagram of an injection signal and a flashing signal according to one embodiment.

[0097] The inkjet head control unit (1430) can generate a jetting signal to jet ink droplets from the inkjet head (20). Here, it is preferable that the jetting signal be generated at a regular cycle. This is because jetting performance, such as the speed, trajectory, and volume of the ink droplets, can vary depending on the jetting frequency.

[0098] The inkjet head control unit (1430) can generate a spray signal periodically. That is, as illustrated in FIG. 4, the inkjet head control unit (1430) can generate a spray signal with a constant cycle (c2). The constant cycle (c2) may be a preset cycle according to inkjet printing needs.

[0099] An ejection signal generated from the inkjet head control unit (1430) can be transmitted to the inkjet head (20) to eject ink droplets. The inkjet head (20) can eject ink droplets at a constant cycle according to an ejection signal having a constant cycle (c2).

[0100] The light source device control unit (1450) can generate a flashing signal for flashing the light source device (40) with a certain delay (d) from the time of generating the injection signal.

[0101] Referring to FIG. 4, the light source device control unit (1450) can generate a blinking signal with a predetermined delay (d) based on the ejection signal generated from the inkjet head control unit (1430). Accordingly, the light source device control unit (1450) can also generate a blinking signal with the same cycle as the ejection signal. Here, the predetermined delay (d) can be a preset time value.

[0102] A flashing signal generated from the light source device control unit (1450) can be transmitted to the light source device (40) to cause the light source device (40) to flash. The light source device (40) can irradiate light onto the ink droplet at a regular cycle according to the flashing signal.

[0103] In one embodiment, the light source device control unit (1450) may generate a blinking signal based only on some of the ejection signals. That is, the light source device control unit (1450) may not generate a blinking signal based on all of the ejection signals generated from the inkjet head control unit, but may generate a blinking signal based only on some of the ejection signals with a predetermined delay (d) from the time of generation of these some of the ejection signals. When the light source device control unit (1450) generates a blinking signal based only on some of the ejection signals, this may be achieved by generating a separate signal that is distinct from the blinking signal.

[0104] The camera control unit (1470) will be described with reference to FIGS. 5 to 7.

[0105] FIG. 5 is a schematic diagram of a trigger pulse signal and a camera (50) exposure start and end time according to one embodiment, and FIGS. 6 and 7 are schematic diagrams showing the relationship between signals of each control unit according to various embodiments.

[0106] The camera control unit (1470) can generate a trigger pulse signal based on an encoder signal and a flash signal or a spray signal, and determine the camera (50) exposure start time based on the trigger pulse signal.

[0107] The camera control unit (1470) can generate a trigger pulse signal according to an encoder signal and a flashing signal or a spray signal. Here, the trigger pulse signal is a signal for determining the exposure time of the camera (50) and can have a rising point and a falling point of the signal. The rising point is the time when the trigger pulse signal is generated, and the falling point is the time when the trigger pulse signal disappears, and can have a pulse width between the rising point and the falling point.

[0108] Since there is no special relationship between the encoder signal, the flash signal and the injection signal on which it is based, the trigger pulse signal determined by these signals may not have a constant period and pulse width.

[0109] According to one embodiment, the camera control unit (1470) may generate a trigger pulse signal with the starting point of the encoder signal as the rising point and the starting point of the blinking signal as the falling point. Specifically, the camera control unit (1470) may generate a trigger pulse signal with the starting point of the encoder signal generated from the motion stage control unit (1410) as the rising point and with the starting point of the blinking signal that first appears after the starting point (rising point) of the encoder signal as the falling point. This may be more clearly understood with reference to FIG. 6. As described above, since there is no correlation between the cycle and signal timing of the encoder signal and the blinking signal, the width or cycle of the trigger pulse signal may not be constant.

[0110] According to another embodiment, the camera control unit (1470) may generate a trigger pulse signal with the starting point of the encoder signal as the rising point and the starting point of the injection signal as the falling point. Specifically, the camera control unit (1470) may generate a trigger pulse signal with the starting point of the encoder signal generated from the motion stage control unit (1410) as the rising point and with the starting point of the injection signal that first appears after the starting point (rising point) of the encoder signal as the falling point. This may be more clearly understood with reference to FIG. 7. As described above, since there is no correlation between the period and signal time of the encoder signal and the injection signal, the width or period of the trigger pulse signal may not be constant.

[0111] The camera control unit (1470) can determine the exposure start time of the camera (50) based on a trigger pulse signal. The camera control unit (1470) can determine the exposure start time at which the camera (50) lens is exposed based on the trigger pulse signal, and control the camera (50) accordingly to capture an image through exposure of the lens.

[0112] In one embodiment, the camera control unit (1470) may determine the rising point of the trigger pulse signal as the camera (50) exposure start point. However, in this case, underexposure and overexposure phenomena may occur. Fig. 8 shows ink droplet images captured at different exposure times when the camera (50) exposure start point is determined as the rising point of the trigger pulse signal. Referring to the example of Fig. 8, underexposure and overexposure phenomena may occur due to a mismatch between the spray start point and the camera (50) exposure start point. Here, if the exposure time (e) of the camera (50) is longer than the spray cycle, the captured image may appear too bright, and if the exposure time (e) of the camera (50) is shorter than the spray cycle, the captured image may appear too dark. In this way, if the rising point of the trigger pulse signal is determined as the camera (50) exposure start point, underexposure and overexposure phenomena may occur, which may cause serious errors in image analysis.

[0113] According to one embodiment, the camera control unit (1470) may determine the falling point of the trigger pulse signal as the camera (50) exposure start point. Referring to FIGS. 5 to 7, the camera control unit (1470) may generate a trigger pulse signal according to the above-described criteria, and then determine the camera (50) exposure start point based on the falling point of the trigger pulse signal. As in FIG. 6, when the falling point of the trigger pulse signal is the starting point of the blinking signal, the light source device (40) may blink simultaneously with the start of shooting of the camera (50). By synchronizing the start of exposure of the camera (50) and the blinking of the light source device (40), a clear image of an ink droplet may be obtained without the underexposure and overexposure phenomena described above. In addition, as in FIG. 7, when the falling point of the trigger pulse signal is the starting point of the spraying signal, the light source device (40) may blink after the start of shooting of the camera (50). By blinking the light source device (40) after the exposure of the camera (50) begins, more stable shooting can be achieved. Therefore, it may be desirable to base the exposure start time of the camera (50) on the falling point of the trigger pulse signal.

[0114] In one embodiment, the light source device control unit (1450) can generate a blinking signal twice within the camera exposure time (e). FIG. 9 is a schematic diagram showing the relationship between signals of each control unit according to one embodiment. Referring to FIG. 9, the light source device control unit (1450) can generate a blinking signal twice consecutively within one camera exposure time (e). In this case, since images for two different times during the falling of one ink droplet can be acquired, the speed and trajectory of the corresponding ink droplet can be measured. The light source device control unit (1450) can make the intervals of consecutive blinking signals generated within one camera exposure time (e) the same, thereby enabling comparison of the speed and trajectory of each ink droplet measured thereafter to determine whether there is an abnormality.

[0115] According to one embodiment, the camera control unit (1470) may select some encoder signals from among the encoder signals based on preset criteria and generate a trigger pulse signal based only on the selected encoder signals. Referring again to FIGS. 6 and 7, the camera control unit (1470) may not generate a trigger pulse signal based on all encoder signals generated from the motion stage control unit (1410), but may select only some signals and generate a trigger pulse signal based thereon. By generating a trigger pulse signal based only on some encoder signals, the camera control unit (1470) may prevent unnecessary camera (50) exposure and optimize monitoring by enabling images to be captured only at necessary times.

[0116] In one embodiment, the camera control unit (1470) can select the first encoder signal at each preset sampling cycle among the encoder signals. Specifically, the camera control unit (1470) can divide the entire encoder signal according to the sampling cycle, select the first signal belonging to each sample, and generate a trigger pulse signal based on this. Referring to the embodiment of FIG. 6, when sampling all encoder signals, the camera control unit (1470) can select only the first signal of each sample and generate a trigger pulse signal based only on these selected signals, since each sample can include four signals. This is because, as the motion stage (30) moves at a constant speed, the time points at which each inkjet head (20) is photographed can also have a constant cycle, and accordingly, monitoring can be optimized by starting the camera (50) exposure at a constant cycle to photograph images.

[0117] In one embodiment, the camera control unit (1470) can determine the sampling period based on the nozzle spacing of the inkjet head (20) and the constant speed of the motion stage (30). Since the nozzles of the inkjet head (20) can be arranged at a constant interval and the motion stage (30) moves the inkjet head (20) at a constant speed, the camera control unit (1470) can determine the sampling period based on this, thereby enabling shooting with the minimum camera (50) exposure for all inkjet heads (20).

[0118] In one embodiment, the light source device control unit (1450) may generate a light source device blinking signal based only on some of the ejection signals that are first generated after some of the selected encoder signals. FIGS. 10 and 11 are schematic diagrams showing the relationship between signals of each control unit according to various embodiments. Referring to FIGS. 10 and 11, the light source device control unit (1450) may generate a blinking signal not based on all of the ejection signals, but only on the ejection signal that is first generated after the selected encoder signal is generated. Through this, the light source device control unit (1450) may generate a blinking signal only during the time (e) when the camera is exposed, thereby preventing the light source device from being turned on unnecessarily during the time when the camera is not exposed and ink droplets are not captured.

[0119] In one embodiment, the camera control unit (1470) can determine the end point of exposure. The camera control unit (1470) can determine the end point of exposure and, accordingly, stop exposing the camera (50) to terminate the shooting. The inkjet head monitoring device (10) of the present invention can optimize the balance between image capturing and power consumption by determining the end point of exposure of the camera (50).

[0120] In one embodiment, the camera control unit (1470) can set the exposure time of the camera (50) to be longer than the blinking time of the light source device (40) and shorter than the spraying cycle of the inkjet head (20). The camera control unit (1470) can capture an image of an ink droplet sufficiently illuminated by setting the exposure time of the camera (50) to be longer than the blinking time of the light source device (40), while preventing multiple ink droplets from being captured by setting the exposure time to be shorter than the spraying cycle of the inkjet head (20).

[0121] In one embodiment, the camera control unit (1470) can determine the point in time when the blinking of the light source device (40) ends as the end point of exposure of the camera (50). That is, the camera control unit (1470) can set the exposure time (e) of the camera (50) to be the same as the blinking time of the light source device (40). Accordingly, the camera control unit (1470) can minimize the exposure time (e) of the camera (50) by exposing the camera (50) only during the blinking time of the light source, thereby optimizing monitoring of the inkjet head (20).

[0122] Figure 12 is a flowchart showing the sequential operation process of each control unit according to one embodiment.

[0123] Referring to FIG. 12, the operation of each control unit according to one embodiment will be summarized and explained. When monitoring starts, the inkjet head monitoring device (10) generates an ejection signal from the inkjet head control unit (1430), and based on this, ink droplets can be ejected from the inkjet head (20). The motion stage control unit (1410) can move the motion stage (30) at a constant speed and periodically generate an encoder signal as the ejection signal is generated. The light source device control unit (1450) can generate a blinking signal having a constant delay (d) with the ejection signal as the ejection signal is generated, and based on this, the light source device (40) can blink. The camera control unit (1470) generates a trigger pulse signal based on the encoder signal, and based on this, camera (50) exposure can be initiated.

[0124]

[0125] The inkjet head monitoring device (10) of the present invention further includes an image analysis unit (not shown), which can acquire images of ink droplets ejected from each nozzle through exposure of the camera (50) through the above process, and analyze the images to inspect the status of each nozzle. For example, the image analysis unit can determine the speed, volume, trajectory, etc. of the ink droplets through analysis of the acquired images, and can use these to determine the ejection performance of each nozzle. In addition, defective ejection can be detected through the ejection performance.

[0126] The inkjet head monitoring device (10) can perform inspection on the inkjet head (20) without stopping the motion stage (30) during the monitoring operation through the above process, and can detect defective nozzles.

[0127]

[0128] The inkjet head monitoring method of the present invention will be described with reference to FIG. 13.

[0129] Figure 13 is a flowchart of an inkjet head monitoring method according to one embodiment of the present invention.

[0130] Referring to FIG. 13, the inkjet head monitoring method of the present invention relates to a method for monitoring an inkjet head (20) of an inkjet printing system (1) including an inkjet head (20) for ejecting ink droplets, a motion stage (30) for moving the inkjet head (20), a light source device (40) for irradiating light on the ink droplets, and a camera (50) for acquiring an ink droplet image, and may include a motion stage control step (S110) for periodically generating an encoder signal in a motion stage control unit (1410) and moving the motion stage (30) at a constant speed without stopping. In addition, the inkjet head monitoring method may include an inkjet head control step (S120) for periodically generating an ejection signal for ejecting ink droplets from the inkjet head in an inkjet head control unit (1430). In addition, the inkjet head monitoring method may include a light source device control step (S130) in which a light source device control unit (1450) generates a flashing signal for flashing the light source device with a predetermined delay from the time of generating the injection signal. In addition, the inkjet head monitoring method may include a camera control step (S140) in which a camera control unit (1470) generates a trigger pulse signal based on an encoder signal and determines a camera (50) exposure start time based on the trigger pulse signal.

[0131] In addition, according to one embodiment, the camera (50) control step (S140) may be characterized by generating a trigger pulse signal with the starting point of the encoder signal as a rising point and the starting point of the flashing signal or injection signal as a falling point.

[0132] Additionally, according to one embodiment, the camera (50) control step (S140) may be characterized by determining the falling point of the trigger pulse signal as the camera (50) exposure start point.

[0133] In addition, according to one embodiment, the camera (50) control step (S140) may be characterized by selecting some of the encoder signals from among the encoder signals based on preset criteria and generating a trigger pulse signal based on the selected some of the encoder signals.

[0134] Additionally, according to one embodiment, the camera (50) control step (S140) may be characterized by selecting the first encoder signal at each preset sampling cycle among the encoder signals.

[0135] Additionally, according to one embodiment, the camera (50) control step (S140) may be characterized by setting a sampling cycle based on the nozzle spacing of the inkjet head (20) and a constant speed of the motion stage (30).

[0136] Additionally, according to one embodiment, the light source device control step (S130) may be characterized by generating a blinking signal based only on some of the injection signals that are first generated after some of the selected encoder signals.

[0137] In addition, according to one embodiment, the camera (50) control step (S140) may be characterized by setting the exposure time of the camera (50) to be longer than the blinking time of the light source device (40) and shorter than the jetting cycle of the inkjet head (20).

[0138] Additionally, according to one embodiment, the light source device control step (S130) may be characterized by generating a blink signal twice within the time that the camera is exposed.

[0139] Additionally, according to one embodiment, the camera (50) control step (S140) may be characterized by determining the point in time at which the blinking of the light source device (40) ends as the point in time at which the camera (50) exposure ends.

[0140]

[0141] Although embodiments of the present invention have been described with reference to the attached drawings, those skilled in the art will appreciate that the present invention can be implemented in other specific forms without altering the technical spirit or essential characteristics of the present invention. Therefore, the embodiments described above should be understood to be illustrative in all respects and not restrictive.

[0142]

[0143] The inkjet head monitoring device and method of the present invention can significantly improve the speed of inkjet head inspection by acquiring images of ink droplets ejected from each inkjet head while the motion stage is moving, and has the effect of minimizing waste of expensive ink and labor costs required during the inspection process and advancing the manufacturing process, so it has high industrial applicability.

Claims

1. An inkjet head monitoring device of an inkjet printing system including an inkjet head that sprays ink droplets, a motion stage that moves the inkjet head, a light source device that irradiates light on the ink droplets, and a camera that acquires an image of the ink droplets, A motion stage control unit that periodically generates an encoder signal and moves the motion stage at a constant speed without stopping; An inkjet head control unit that periodically generates an ejection signal to eject ink droplets from the inkjet head; A light source device control unit that generates a flashing signal for flashing the light source device with a certain delay from the time of generating the injection signal; and A camera control unit that generates a trigger pulse signal based on the encoder signal and determines the camera exposure start time based on the trigger pulse signal; Inkjet head monitoring device.

2. In paragraph 1, The above camera control unit, It is characterized in that the trigger pulse signal is generated by setting the starting point of the encoder signal as the rising point and the starting point of the flashing signal or the injection signal as the falling point. Inkjet head monitoring device.

3. In paragraph 2, The above camera control unit, Characterized in that the falling point of the above trigger pulse signal is determined as the camera exposure start point. Inkjet head monitoring device.

4. In paragraph 1, The above camera control unit, It is characterized in that some of the encoder signals are selected based on preset criteria, and the trigger pulse signal is generated based on the selected some of the encoder signals. Inkjet head monitoring device.

5. In paragraph 4, The above camera control unit, It is characterized in that the first encoder signal is selected at each preset sampling period among the above encoder signals. Inkjet head monitoring device.

6. In paragraph 5, The above camera control unit, Characterized in that the sampling cycle is set based on the nozzle spacing of the inkjet head and the constant speed of the motion stage. Inkjet head monitoring device.

7. In paragraph 4, The above light source device control unit, Characterized in that the flashing signal is generated only based on some of the injection signals that are first generated after some of the selected encoder signals. Inkjet head monitoring device.

8. In paragraph 1, The above camera control unit, Characterized in that the exposure time of the camera is set to be longer than the blinking time of the light source device and shorter than the jetting cycle of the inkjet head. Inkjet head monitoring device.

9. In paragraph 1, The above light source device control unit, characterized in that the above camera generates the above blinking signal twice within the exposure time. Inkjet head monitoring device.

10. In paragraph 1, The above camera control unit, It is characterized in that the point in time when the blinking of the above light source device ends is determined as the point in time when the camera exposure ends. Inkjet head monitoring device.

11. A method for monitoring an inkjet head of an inkjet printing system, comprising an inkjet head that sprays ink droplets, a motion stage that moves the inkjet head, a light source device that irradiates light on the ink droplets, and a camera that acquires an image of the ink droplets. A motion stage control step for periodically generating an encoder signal from a motion stage control unit and moving the motion stage at a constant speed without stopping; An inkjet head control step for periodically generating an ejection signal to eject ink droplets from the inkjet head in an inkjet head control unit; In a light source device control unit, a light source device control step of generating a flashing signal for flashing the light source device with a certain delay from the time of generating the injection signal; and In the above camera control unit, a camera control step for generating a trigger pulse signal based on the encoder signal and determining the camera exposure start time based on the trigger pulse signal; How to monitor inkjet heads.

12. In paragraph 11, The above camera control step is, It is characterized in that the trigger pulse signal is generated by setting the starting point of the encoder signal as the rising point and the starting point of the flashing signal or the injection signal as the falling point. How to monitor inkjet heads.

13. In paragraph 12, The above camera control step is, Characterized in that the falling point of the above trigger pulse signal is determined as the camera exposure start point. How to monitor inkjet heads.

14. In paragraph 11, The above camera control step is, It is characterized in that some of the encoder signals are selected based on preset criteria, and the trigger pulse signal is generated based on the selected some of the encoder signals. How to monitor inkjet heads.

15. In paragraph 14, The above camera control step is, It is characterized in that the first encoder signal is selected at each preset sampling period among the above encoder signals. How to monitor inkjet heads.

16. In paragraph 15, The above camera control step is, Characterized in that the sampling cycle is set based on the nozzle spacing of the inkjet head and the constant speed of the motion stage. How to monitor inkjet heads.

17. In paragraph 14, The above light source device control step is, Characterized in that the flashing signal is generated only based on some of the injection signals that are first generated after some of the selected encoder signals. How to monitor inkjet heads.

18. In paragraph 11, The above camera control step is, Characterized in that the exposure time of the camera is set to be longer than the blinking time of the light source device and shorter than the jetting cycle of the inkjet head. How to monitor inkjet heads.

19. In paragraph 11, The above light source device control step is, characterized in that the above camera generates the above blinking signal twice within the exposure time. Inkjet head monitoring device.

20. In paragraph 11, The above camera control step is, It is characterized in that the point in time when the blinking of the above light source device ends is determined as the point in time when the camera exposure ends. How to monitor inkjet heads.

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