Ejection apparatus and method for determining ejection timing

Abstract

To improve calculation accuracy of ejection speed of an ink droplet.SOLUTION: An ejection apparatus includes: a droplet detection sensor for detecting a droplet that is ejected from a recording head; and change means for changing a distance between the recording head and a droplet detection sensor. The ejection apparatus measures time from ejecting an ink droplet from the recording head to detecting the ink droplet by the droplet detection sensor several times while changing a distance between the recording head and the droplet detection sensor and calculates an ejection speed of an ink droplet on the basis of a distance difference and a time difference.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a discharge device and a method for calculating a discharge speed. [Background technology]

[0002] In inkjet recording devices, the ejection speed of ink droplets can change over time due to individual differences in the recording device and recording head, the physical properties of the ink, and even the operating conditions and environmental influences. If the ink droplet ejection speed changes, for example, when recording an image by reciprocating scanning of the recording head, the relationship between the landing positions of ink droplets ejected in the forward direction and those ejected in the backward direction will be shifted, affecting image quality.

[0003] Patent Document 1 discloses a registration adjustment method that includes an optical detector that measures the ejection speed of ejected ink, and that appropriately sets the ejection timing from the moving speed of the print head and the ejection speed based on the measurement results. This document also discloses a method for measuring the ink ejection speed, in which the time from the ink ejection timing until it reaches a light beam irradiated from the optical detector is measured, and the ejection speed is calculated based on the measurement result and the distance from the print head to the light beam. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-152853 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the method of calculating the ejection speed by setting the distance between the ejection head and the droplet detection sensor constant, as in Patent Document 1, if there is an error in the distance between the ejection head and the droplet detection sensor, the ejection speed cannot be determined with high accuracy.

[0006] The present invention has been made in view of the above-mentioned problems, and has an object to improve the accuracy of calculating the ejection velocity of ink droplets. [Means for solving the problem]

[0007] The present invention provides a discharge device having a discharge head that discharges droplets from discharge ports formed in a discharge port surface; detection means having a light-emitting portion that emits light and a light-receiving portion that receives the light emitted by the light-emitting portion; droplet detection means that detects droplets discharged from the discharge head based on the amount of light received by the light-receiving portion when the discharge head and the detection means are positioned so that droplets discharged from the discharge head pass between the light-emitting portion and the light-receiving portion; time detection means that detects the time from when the discharge head starts to discharge the droplets to when the droplet detection means detects that the droplets have passed through the light; and calculation means that calculates the discharge speed of the droplets based on the time detected by the time detection means and the distance between the discharge port surface and the light emitted by the light-emitting portion. The apparatus further includes a change means for changing the distance between the ejection head and the detection means, wherein the time detection means detects a first time from when the ejection of droplets from the ejection port begins to when the droplet detection means detects the droplets, when a distance between the ejection port surface of the ejection head and the light emitted by the light-emitting unit is a first distance, and detects a second time from when the ejection of droplets from the ejection port begins to when the droplet detection means detects the droplets, when a distance between the ejection port surface of the ejection head and the light emitted by the light-emitting unit is a second distance different from the first distance, by the change means, and wherein the calculation means calculates the ejection speed of the droplets based on the first distance, the second distance, the first time, and the second time. [Effects of the Invention]

[0008] According to the present invention, the time from when an ink droplet is ejected from the ejection head to when the ink droplet is detected by the droplet detection sensor can be measured multiple times by changing the distance between the ejection head and the droplet detection sensor, thereby improving the accuracy of calculating the ejection speed of the ink droplet. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing the appearance of a recording apparatus according to a first embodiment. [Figure 2] FIG. 1 is a perspective view showing the internal configuration of a recording apparatus according to a first embodiment. [Figure 3] FIG. 2 is a block diagram showing the control configuration of the recording apparatus according to the first embodiment. [Figure 4] FIG. 10 is a schematic diagram showing the correlation between the ejection speed and the landing position of an ink droplet. [Figure 5] 5A and 5B are diagrams for explaining a method for calculating the ejection velocity of ink droplets in the first embodiment. [Figure 6] FIG. 4 is a diagram showing detection time and ejection speed in the first embodiment. [Figure 7] 10 is a flowchart of a process for calculating a discharge velocity in the first embodiment. [Figure 8] 10A and 10B are diagrams illustrating an internal configuration of a distance detection sensor and an example of detection according to a second embodiment. [Figure 9] FIG. 10 is a diagram showing detection times and ejection speeds in the second embodiment. [Figure 10] 10 is a flowchart of a process for calculating a discharge velocity in the third embodiment. [Figure 11] FIG. 10 is a diagram showing a pattern for adjusting a print position deviation in the third embodiment. [Figure 12] FIG. 11 is a diagram showing detection times and ejection speeds in the third embodiment. [Figure 13] 10 is a flowchart of a correction process for ejection timing according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] (First embodiment) <Overall overview of the recording device> FIG. 1 is a diagram showing the appearance of an inkjet recording apparatus (hereinafter referred to as a recording apparatus) 100 as an example of a droplet ejection apparatus according to an embodiment.

[0011] The recording device 100 shown in FIG. 1 includes a paper discharge guide 101 for stacking output recording media, a display panel 103 for displaying various recording information and setting results, and operation buttons 102 for setting the recording mode, recording paper, etc. The recording device 100 also includes an ink tank unit 104 that houses ink tanks for storing ink of colors such as black, cyan, magenta, and yellow, and supplies ink to a recording head 201 (FIG. 2) as an example of a droplet ejection head. The recording device of FIG. 1 is capable of recording on recording media of multiple widths up to a 60-inch size. Roll paper or cut paper can be used as the recording medium 203. Furthermore, the recording medium 203 is not limited to paper, and may be, for example, cloth or vinyl.

[0012] FIG. 2 is a perspective view showing the internal configuration of the recording apparatus 100. The platen 212 is a member that supports the recording medium 203, which is positioned opposite the recording head 201. The recording medium 203 is supported by the platen 212 and transported in the transport direction (Y direction) by a paper transport roller 213. The recording head 201 has an ejection port surface 201a (FIG. 5) in which ejection ports are formed. The ejection port surface 201a has ejection port arrays, each for each ink color, with multiple ejection ports arranged in the Y direction, and the ejection port arrays are arranged in the X direction. The recording head 201 is mounted on a carriage 202. The recording head 201 also has a distance detection sensor 204 for detecting the distance between the recording medium 203 on the platen 212 and the recording head 201. The distance detection sensor 204 is an optical sensor that has a light-emitting element (FIG. 8) that irradiates light onto the recording medium 203 and a light-receiving element (FIG. 8) that receives light reflected from the recording medium 203, and measures distance from changes in the output of the light-receiving element. Details will be explained in FIG. 8. The droplet detection sensor 205 is a sensor that detects droplets, in this case ink droplets, ejected from the recording head. The droplet detection sensor 205 is an optical sensor that includes a light-emitting element 401 (FIG. 5), a light-receiving element 402 (FIG. 5), and a control circuit board 403 (FIG. 5). Details will be explained in FIG. 5. A main rail 206 supports the carriage 202, which scans back and forth along the main rail 206 in the X direction (a direction perpendicular to the recording medium transport direction). The carriage 202 scans by being driven by a carriage motor 208 via a carriage transport belt 207. The linear scale 209 is disposed in the scanning direction, and an encoder sensor 210 mounted on the carriage 202 detects the linear scale 209 to obtain position information. Furthermore, the recording device 100 is equipped with a lift cam (not shown) for gradually varying the height of the main rail 206 that supports the carriage 202, and a lift motor 211 for driving the lift cam. By driving the lift cam with the lift motor 211, the recording head 201 is raised and lowered, and the distance between the recording head 201 and the recording medium 203 can be increased or decreased.The height can be varied in multiple stages with a predetermined accuracy based on the stop position of the lift cam, and the amount of height variation is driven relative to the height of the predetermined stage, so the variation distance between stages can be set with high accuracy.

[0013] 3 is a block diagram showing the control configuration of the recording device 100. The recording device 100 includes a CPU 301 that controls the entire device, a sensor / motor control unit 302 that controls each sensor and motor, and a memory 303 that stores various information such as the discharge speed and the thickness of the recording medium. The CPU 301, sensor and motor control unit 302, and memory 303 are connected to each other so that they can communicate with each other. The sensor and motor control unit 302 controls the distance detection sensor 204, the droplet detection sensor 205, and the carriage motor 208 that scans the carriage 202. The sensor and motor control unit 302 also controls the head control circuit 305 based on position information detected by the encoder sensor 210, causing ink to be ejected from the print head 201.

[0014] Image data transmitted from the host device 1 is converted into ejection signals by the CPU 301, and ink is ejected from the print head 201 in accordance with the ejection signals to print on the recording medium 203. The CPU 301 includes a driver unit 306, a sequence control unit 307, an image processing unit 308, a timing control unit 309, and a head control unit 310. The sequence control unit 307 controls overall printing, specifically starting and stopping the various functional blocks of the image processing unit 308, the timing control unit 309, and the head control unit 310, controlling the transportation of the recording medium, and controlling the scanning of the carriage 202. The sequence control unit 307 controls each functional block by reading and executing various programs from the memory 303. Based on commands from the sequence control unit 307, the driver unit 306 generates control signals for the sensor / motor control unit 302, the memory 303, the head control circuit 305, etc., and transmits input signals from each block to the sequence control unit 307.

[0015] The image processing unit 308 performs image processing, which involves color separation and conversion of input image data from the host device 1 and converting the data into print data that can be printed by the print head 201. The timing control unit 309 transfers the print data converted and generated by the image processing unit 308 to the head control unit 310 in conjunction with the position of the carriage 202. The timing control unit 309 also controls the timing of the ejection of the print data. The timing control is performed according to the ejection timing determined based on the ejection speed calculated in the ejection speed calculation process described below. The head control unit 310 functions as an ejection signal generating unit, converting the print data input from the timing control unit 309 into an ejection signal and outputting it. It also controls the temperature of the print head 201 by outputting a control signal that does not eject ink based on commands from the sequence control unit 307. The head control circuit 305 functions as a drive pulse generating unit, generating a drive pulse according to the ejection signal input from the head control unit 310 and applying it to the print head 201.

[0016] Next, adjustment of the ejection timing will be described using Figure 4. Figure 4(a) is a schematic diagram showing the relationship between the ejection speed and landing position of ink droplets. The distance in the Z direction between the ejection port surface 201a of the print head 201 and the print medium 203 is defined as H. The print head 201 ejects ink while scanning back and forth in the X direction at a speed Vcr to print an image on the print medium 203. The ejection speed of ink droplets ejected from the print head 201 is defined as Va. As shown in Figure 4(a), the scanning directions are different between the forward scan and the backward scan, so the ink landing position relative to the position where the ink droplets were ejected differs. The ejection timing of the ink droplets is adjusted to match the landing position of the ink droplets ejected by the print head 201. First, the distance Xa from the position where the ink droplets were ejected during the forward scan to the position where the ink droplets land on the print medium 203 is described by the following formula:

[0017] Xa = (H / Va) × Vcr Furthermore, the distance Xb from the position where the ink droplets are ejected to the position where the ink droplets land on the recording medium 203 during the backward scan is expressed by the following formula:

[0018] Xb = (H / Va) × (-Vcr) = -Xa As described above, an appropriate ejection timing for the position of the print head 201 detected by the encoder sensor 210 is determined based on the distance between the print head 201 and the print medium 203 and the ejection speed of ink droplets detected by the droplet detection sensor 205. In this embodiment, a default ejection speed and the ejection timing for the default ejection speed are determined in advance and stored in the memory 303. The adjustment value for the ejection timing for this default ejection speed is set to 0, and the adjustment value is adjusted by a value ranging from -4 to +4 depending on the ejection speed. The adjustment is performed in 1200 dpi increments. A table in which the ejection speed and the adjustment value for the ejection timing are associated is stored in the memory 303 in advance. Then, the adjustment value for the ejection timing corresponding to the speed obtained by the ejection speed calculation process shown in FIG. 7 (described later) is obtained from the table, and the ejection timing is adjusted.

[0019] 4(b) shows a case where the ink droplet ejection speed detected by the droplet detection sensor 205 is slower than the ink droplet ejection speed shown in FIG. 4(a). In this case, the distance Xa' from the position where the ink droplet is ejected during the forward scan to the position where the ink droplet lands on the recording medium 203 is expressed by the following formula:

[0020] Xa' = (H / Va') × Vcr If we assume that the ejection speed of ink droplets ejected from the print head 201 is attenuated by 10% until they land on the print medium 203, the distance from the ejection position to the landing position can be calculated as follows:

[0021] Xa'=(H / Va')× Vcr =(H / (Va×0.9))×Vcr = 1.11×Xa As described above, when the ejection speed slows, the landing position shifts in the scanning direction of the print head 201. Once the distance from the ejection position to the landing position is determined, an appropriate adjustment value for the ejection timing can be determined based on the ejection speed, as in the case of FIG. 4A. In the first embodiment, it is assumed that the print medium 203 is sufficiently thin, and that the distance between the ejection port surface 201a of the print head 201 and the print medium 203 can be considered to be the same as the distance between the ejection port surface 201a and the platen 212.

[0022] Next, a method for calculating the ejection velocity of ink droplets ejected from the print head 201 in this embodiment will be described with reference to Fig. 5. Fig. 5 shows a schematic diagram of the print head 201 and the droplet detection sensor 205 when the printing apparatus 100 is cut along the YZ cross section. It also shows a timing chart of an ejection signal for applying a drive pulse to the print head 201 and a detection signal when the droplet detection sensor 205 detects the passage of an ink droplet.

[0023] As shown in FIG. 5A, the print head 201 has an ejection orifice surface 201a. The droplet detection sensor 205 is composed of a light-emitting element 401, a light-receiving element 402, a control circuit board 403, and other components. The light-emitting element 401 emits light 404, and the light-receiving element 402 receives the light 404 emitted by the light-emitting element 401. The control circuit board 403 detects the amount of light received by the light-receiving element 402. When an ink droplet passes through the light 404, the amount of received light decreases, allowing the passage of the ink droplet to be detected. The droplet detection sensor 205 is installed so that the optical axis of the light 404 is aligned in the Z direction with the surface of the platen 212 that supports the recording medium 203. Slits are provided near the light-emitting element 401 and the light-receiving element 402, respectively, to narrow the incident light 404 and improve the S / N ratio. The detection position is the position of the print head 201 in the X direction at which ink droplets can be ejected so that the ink droplets pass through the light 404. When detecting ink droplets to calculate their ejection speed, the sequence control unit 307 causes the sensor motor control unit 302 to control the carriage motor 208, and the recording head 201 moves to a detection position. In this embodiment, the cross-sectional area of the light beam 404 is approximately 1 (mm^2). The parallel light projection area of the ink droplet when it passes through the light 404 is approximately 2^-3 (mm^2).

[0024] FIG. 5A shows the state when the distance in the height direction (Z direction) between the ejection port surface 201a of the print head 201 and the light 404 emitted by the light-emitting element 401 is H1. If the distance between the ejection port surface 201a and the light 404 is not H1, the sensor / motor control unit 302 drives the lift motor 211 to move the height of the print head 201 using a lift cam. When the state shown in FIG. 5A is reached, an ejection signal from the head control unit 310 in the CPU 301 is sent to the head control circuit 305 via the driver unit 306. The driver unit 306 transmits the timing of sending the ejection signal to the sequence control unit 307. The head control circuit 305 generates a drive pulse in accordance with the ejection signal and applies it to the print head 201 to eject ink from the ejection port. When an ink droplet passes through the light 404 emitted by the light-emitting element 401 and the amount of light received by the light-receiving element 402 changes, the timing of the change in the amount of received light is output as a detection signal from the control circuit board 403. The output detection signal is sent to the sequence control unit 307 via the sensor / motor control unit 302. The sequence control unit 307 then detects the detection time T1 from when the ejection signal is issued until the detection signal is output. As described above, the sequence control unit 307 functions as a time detection means that detects the time from when the ink ejection starts until the ejected ink droplets are detected, and detects the detection time for calculating the ejection speed.

[0025] 5(b) shows a state in which, after detecting ink droplets in FIG. 5(a), the lift motor 211 is driven, and the distance in the height direction (Z direction) between the ejection port surface 201a of the print head 201 and the light 404 emitted by the light emitting element 401 is set to H2. As in FIG. 5(a), the timing at which the amount of light received by the light receiving element 402 changes when an ink droplet passes through the light 404 of the droplet detection sensor 205 is output as a detection signal. Then, the sequence control unit 307 detects the detection time T2, which is the time from when an ejection signal to cause the print head 201 to eject ink droplets is issued until the detection signal is output.

[0026] 5(a) and 5(b), the sequence control unit 307 calculates the ejection velocity V1 of the ink droplet passing between the distance H2 and the distance H1 based on the time difference between the detection times T1 and T2 and the distance difference between the distances H1 and H2. The calculation formula is as follows:

[0027] V1=(H2-H1) / (T2-T1) After calculating the ejection velocity V1, the lift motor 211 is driven to increase the vertical distance between the ejection orifice surface 201a and the light 404 to H3, which is greater than the distance H2. This state is shown in FIG. 5(c). As in FIGS. 5(a) and 5(b), ink droplets are ejected from the ejection orifices of the print head 201. The timing of the change in the amount of light when the ejected ink droplets pass through the light 404 of the droplet detection sensor 205 is detected as a detection signal by the control circuit board 403. The sequence controller 307 then detects the detection time T3, which is the time from when an ejection signal to cause the print head 201 to eject an ink droplet is issued to when the detection signal is output. As in the case described with reference to FIGS. 5(a) and 5(b), the ejection velocity V2 of the ink droplets passing between the distances H3 and H2 is calculated based on the difference between the detection times T2 and T3 detected at the distances H2 and H3, respectively, and the distance difference between the distances H2 and H3. The calculation formula is as follows:

[0028] V2 = (H3 - H2) / (T3 - T2) After calculating the ejection velocity V2, the lift motor 211 is further driven to increase the vertical distance between the ejection orifice surface 201a and the light 404 to H4, which is greater than the distance H3. This state is shown in FIG. 5(d). As in FIGS. 5(a), 5(b), and 5(c), ink droplets are ejected from the ejection orifices of the print head 201. The control circuit board 403 detects the timing of the change in the amount of light when the ejected ink droplets pass through the light 404 of the droplet detection sensor 205, and outputs a detection signal. The sequence control unit 307 then detects the detection time T4, which is the time from when an ejection signal to cause the print head 201 to eject an ink droplet is issued to when the detection signal is output. As described with reference to FIGS. 5(a) to 5(c), the ejection velocity V3 of the ink droplets passing between the distances H4 and H3 is calculated based on the difference between the detection times T3 and T4 detected at the distances H3 and H4, respectively, and the distance difference between the distances H3 and H4. The calculation formula is as follows:

[0029] V3 = (H4 - H3) / (T4 - T3) As described above, the distance between the print head 201 and the droplet detection sensor 205 is changed, and the ink droplet ejection velocity V is calculated by detecting the detection time at each distance. While the detection times are detected in order from shortest to longest distances, the detection order is not limited to this. For example, the detection times may be detected in order from longest to longest distances. In this embodiment, the separation distance H is between 1.2 mm and 2.2 mm.

[0030] Furthermore, the ejection speed may be calculated by measuring the detection time at more distances between the print head 201 and the droplet detection sensor 205. Because the ejection speed corresponding to more distances can be calculated, the attenuation effect of the ejection speed (whether the ejection speed is constant or changes depending on the distance) can be obtained in more detail. As a result, the ejection speed and attenuation effect of the ink droplets can be obtained with higher accuracy.

[0031] Figures 6(a) and (c) are diagrams showing the distance between the ejection port surface 201a and the light 404 of the droplet detection sensor 205, and the output results of the detection time at each distance, as explained in Figure 5. Figures 6(b) and (d) are diagrams showing the relationship between the ejection speed calculated from the distances and detection times shown in Figures 6(a) and (c), respectively, and the difference between each distance.

[0032] In the graph shown in Figure 6(a), the vertical axis represents the detection time detected by the sequence control unit 307, and the horizontal axis represents the distance between the ejection port surface 201a of the print head 201 and the light 404 of the droplet detection sensor 205. The points indicated by the hatched circles in Figure 6(a) are the points where measurements were actually taken. Here, detection was performed at distances H1 to H5. Distance H5 is a distance further away than distance H4.

[0033] In the graph shown in Figure 6(b), the vertical axis represents the discharge speed, and the horizontal axis represents the difference in each distance. At this time, the calculated discharge speed data may be subject to nonlinear changes due to various influences. Therefore, in order to more accurately calculate the discharge speed data shown for each distance difference, an approximate curve of a polynomial of second or higher order is calculated from the acquired discharge speed data, and the polynomial of the calculated approximate curve is used as the equation representing the discharge speed. To calculate the approximate curve, three or more discharge speeds are used. To calculate three or more discharge speeds, it is necessary to detect the detection times at four or more distances. The method for calculating the discharge speed is as described above.

[0034] Furthermore, the inventors' experiments have revealed that it is possible to obtain data that transitions linearly, depending on individual differences between print heads, differences in the physical properties of each ink color, and even usage conditions and environmental influences. Data for such a linear transition is shown in Figure 6(c). In this case, as with the above, the ejection velocity can be calculated from the detection time at each distance and the difference in distance between the ejection port surface 201a and the light 404. Figure 6(d) shows the relationship between the calculated ejection velocity and the difference in distance. As shown in Figure 6(d), the ejection velocity calculated for each difference in distance indicates a constant ejection velocity regardless of the difference in distance. If it is known that data transitioning linearly can be obtained, a single ejection velocity is sufficient because the ejection velocity is constant regardless of the distance. To calculate a single ejection velocity, the detection times at two distances are simply measured.

[0035] Furthermore, even if the transition of the ejection speed is nonlinear, it is not necessary to calculate an approximation curve if printing is performed only when the distance between the ejection port surface 201a and the printing medium 203 is constant. In this case, it is sufficient to detect the detection times at two distances between which the distance at the time of printing is included.

[0036] FIG. 7 corresponds to FIGS. 5 and 6 and shows a flowchart of the process for calculating the discharge velocity.

[0037] The discharge velocity calculation process shown in Fig. 7 is performed when the user of the recording apparatus 100 operates the recording apparatus 100 for the first time, or when the recording head 201 is replaced with a new one and installed. It may also be performed periodically as part of maintenance, or in response to a user instruction. The process shown in Fig. 7 is performed by the sequence control unit 307 of the CPU 301 in accordance with a program stored in the memory 303, for example.

[0038] First, in step S601, the sequence control unit 307 drives the lift motor 211 to separate the print head 201 and the droplet detection sensor 205 by a predetermined distance. The separation distance is set in advance in the memory 303, and in this embodiment, is the distances H1 to H4 described in Figure 5. The order of the separation distances is H1, H2, H3, and H4, as described in Figure 5.

[0039] Next, the process proceeds to step S602, where preprocessing required to detect the ejection speed is performed. Specifically, this includes presetting the optimal ejection control to detect the ejection speed, performing a preliminary ejection operation to ensure stable ejection of ink droplets, and stopping the suction fan to stabilize airflow control inside the recording device.

[0040] Next, proceeding to step S603, an ejection operation is performed in which test ink droplets are ejected from the print head 201 in response to light 404 emitted by the light emitting element 401 of the droplet detection sensor 205. More specifically, a detection time is detected, which is the time from when ink droplet ejection begins from a predetermined nozzle of the print head 201 at the distance separated in step S601 until the light receiving element 402 of the droplet detection sensor 205 detects that the ink droplet has passed through the light 404. At this time, multiple detection times are detected using multiple nozzles of the print head 201. It is desirable to select a wide range of nozzles, including both ends and the center, as the nozzles to be targeted for detection time measurement in order to accurately detect the ejection speed.

[0041] Next, proceeding to step S604, data processing of the detection time acquired in step S603 is performed to calculate the detection time for the distance set in step S601. Specifically, data processing such as averaging based on the number of acquired samples required to stabilize the measurement of the detection time and deleting data outside the upper and lower error ranges to prevent the inclusion of abnormal values in the data is performed.

[0042] Next, the process proceeds to S605, where it is determined whether or not the detection time has been detected for all distances set in the memory 303. In this embodiment, it is determined whether or not the current distance between the ejection port surface 201a and the light 404 of the droplet detection sensor 205 is the final distance H4. If the distance is not distance H4, the process returns to step S601, where the distance is increased by the next set distance, and subsequent data acquisition and processing are performed. If it is determined in step S605 that the current distance is distance H4, it is determined that acquisition of the detection time for all distances has been completed, and the process proceeds to S606.

[0043] In step S606, the ejection speed is calculated. More specifically, as described with reference to Figs. 5 and 6, the ejection speed is calculated based on the difference between the distances and the detection time at each distance. Once the ejection speed is calculated, the process proceeds to step S607, where the information on the ejection speed calculated in step S606 is stored in the memory 303. The ejection speed information stored here is used thereafter for data processing and drive control of the print head 201 according to the required processing.

[0044] Next, the process proceeds to step S608, where termination processing is performed. More specifically, since the calculation of the ejection speed has been completed, the print head 201 may be retracted to a predetermined position, or the process may transition to a standby state for the next printing operation, or further, based on the acquired ejection speed information, the process may transition to cleaning processing of the print head 201, and then this processing ends.

[0045] 7 is completed, a table in which ejection speeds and ejection timing adjustment values correspond to each other and which is stored in advance in memory 303, and an ejection timing adjustment value is obtained from the table based on the ejection speed obtained by the process in Fig. 7, and the ejection timing is adjusted. When printing an image, a timing control unit 309 controls the timing of ejecting ink in accordance with the print data.

[0046] As described above, in this embodiment, the distance between the print head 201 and the droplet detection sensor 205 is changed, and the time from ink droplet ejection to detection is detected for each of the distances. The ejection velocity is then calculated based on the difference between the distances and the difference in the detection time. This allows the ink droplet ejection velocity to be calculated with high accuracy, even without a highly accurate assembly. Furthermore, by detecting the detection time for four or more distances, it is possible to more accurately obtain information on the individual differences between the printing apparatus and print head, the physical properties of each ink color, the usage conditions and environmental influences, and the attenuation effect of the ejection velocity at each distance. Furthermore, by adjusting the ejection timing based on the ejection velocity, it is possible to suppress degradation of image quality due to misalignment of the ink droplet landing position.

[0047] In the above embodiment, the print head 201 is configured to move relative to the droplet detection sensor 205 to change the distance, but it is sufficient if the distance in the Z direction between the droplet detection sensor 205 and the print head 201 changes relatively. Therefore, for example, the droplet detection sensor 205 may be moved in the Z direction to change the distance.

[0048] In the above embodiment, a method for calculating the ejection speed from the difference between each distance and the difference between the detection times has been described with respect to calculation of the ejection speed by the droplet detection sensor 205. However, a method may also be used in which the detection times are acquired at multiple distances and the ejection speed is calculated based on each distance and the corresponding detection time.

[0049] It was also shown that the target nozzles for measuring the detection time of the ejection velocity can be set to a wider range. However, depending on the user's usage, the ejection speed may be measured for nozzles that are used more frequently in printing. (Second embodiment) Next, a first embodiment will be described. In the first embodiment, the thickness of the recording medium 203 was not taken into consideration, but in reality, the recording medium 203 has a thickness, so the distance between the ejection port surface 201a and the platen 212 and the distance between the ejection port surface 201a and the recording medium 203 are different. In particular, when recording is performed using a thick recording medium, an adjustment value determined based on the distance between the ejection port surface 201a and the platen 212 may cause the ejection position to shift due to the difference in the distance between the ejection port surface 201a and the recording medium 203. In this embodiment, the ejection timing is adjusted based on the distance between the ejection port surface 201a and the recording medium 203.

[0050] The distance between the ejection port surface 201a and the recording medium 203 is measured by a distance detection sensor 204. Then, ejection timing control is performed based on the distance between the print head 201 and the recording medium 203 detected by the distance detection sensor 204 and ejection speed information calculated in the ejection speed calculation process.

[0051] FIG. 8 is a diagram showing the internal configuration of the distance detection sensor 204 and the changes in light intensity (output) of the irradiation area and light-receiving area that change depending on the distance from the irradiation surface of the recording medium 203. As shown in FIG. 8(a), the distance detection sensor 204 is equipped with a control board 701 that turns on and off a light source at a position where the recording medium 203 is transported, a light-emitting unit 702 for emitting light, and light-receiving units 703 and 704 for receiving the reflected light. In this embodiment, the surface of the distance detection sensor 204 facing the recording medium 203 is located at the same position in the Z direction as the ejection port surface 201a of the print head 201. Therefore, the distance to the recording medium 203 measured by the distance detection sensor 204 corresponds to the distance between the ejection port surface 201a of the print head 201 and the recording medium 203. Furthermore, the intensity of the reflected light obtained by the light-receiving units 703 and 704 is converted into an output signal of a current value or a voltage value, and a predetermined arithmetic operation is performed on the output signal, and the result is stored in the memory 303. For example, the ratio of the output signals obtained by the light receiving units 703 and 704 is stored as distance information data indicating the relationship between the distance from the recording head 201 to the recording medium 203. FIG. 8(b) shows the relationship between the distance, the output signal, and the distance information data. As shown in FIG. 8(b), when the distance from the irradiation surface of the recording medium 203 is M1, the amount of light reflected to the light receiving unit 704 is maximum, and the amount of light reflected to the light receiving unit 703 is minimum. Therefore, the ratio of the output signals from the distance detection sensor 204, i.e., the distance information data, also shows a minimum. Furthermore, when the irradiation surface of the recording medium is M3, the amount of light reflected to the light receiving units 703 and 704 is approximately half of its peak. Therefore, the output distribution of the distance detection sensor is equal between light receiving unit 703 and light receiving unit 704, and the ratio of the output signal of distance detection sensor 204, i.e., the distance information data, is also 1. Furthermore, when the irradiation surface of the recording medium is M5, the amount of reflected light to light receiving unit 704 is minimum and the amount of reflected light to light receiving unit 703 is maximum. Therefore, the output distribution of the distance detection sensor is minimum for light receiving unit 704 and maximum for light receiving unit 703, and the ratio of the output signal of distance detection sensor 204, i.e., the distance information data, is also maximum. Here, the relationship between the reference irradiation surface position and the proportional value of the output signal of distance detection sensor 204 may be calculated in advance and stored in memory 303. For example, a value detected for a recording medium of a predetermined thickness can be retained as a reference value. Furthermore, it is possible to store the positions of the recording head 201 when the distances from the recording head 201 to the recording medium 203 are M1 to M5 and the distance from the recording head 201 to the droplet detection sensor 205 at that time.

[0052] FIG. 9(a) is a diagram showing distances H1 to H5 at which the droplet detection sensor 205 and the print head 201 are separated, and the output results of the detection time detected by the droplet detection sensor 205 at each distance. FIG. 9(b) is a diagram showing the relationship between the distances shown in FIG. 9(a) and the ejection speed calculated from the detection time. The detection time and ejection speed are obtained using the same method as described in FIG. 6 of the first embodiment. In FIG. 9, the detected speeds at distances H1 to H5 are obtained, and the corresponding ejection speeds V1 to V5 are calculated. After the ejection speeds are obtained, an approximation curve representing the ejection speeds is calculated from the obtained ejection speeds, as in the first embodiment.

[0053] To determine the adjustment value for the ejection timing, first, the recording medium 203 is transported onto the platen 212, and the distance between the transported recording medium 203 and the ejection port surface 201a is measured by the distance detection sensor 204. Then, the speed corresponding to the measured distance between the ejection port surface 201a and the recording medium 203 is obtained from the ejection speed approximation curve. In this way, by calculating the ejection speed of ink droplets from the actually measured distance between the ejection port surface 201a and the recording medium 203, it is possible to calculate a more accurate ejection speed.

[0054] In Figure 9(a), measurement points are indicated by diagonally shaded circles. Figure 9(a) shows the detection time of ink droplets when the distance between the print head 201 and the droplet detection sensor 205 is increased from distance H1 to distance H5. Figure 9(b) shows the relationship between the ejection velocity calculated based on Figure 9(a) and the difference between each distance. By interpolating the output results of the detection times measured at distances H1 to H5 on an approximation curve, it is possible to predict the detection time and ejection velocity for distances other than the measured distances H1 to H5 (H0, H6, etc.). In addition to distances far from the distance range H1 to H5, such as distances H0 and H6, it is also possible to determine the velocity at distances between H1 and H2.

[0055] For example, assume that the ejection speeds have been calculated when the distance between the ejection port surface 201a and the droplet detection sensor 205 is 1.0 mm and 1.5 mm. In this case, if the distance between the ejection port surface 201a and the recording medium 203 measured by the distance detection sensor 204 is 1.1 mm, the ejection speed when the distance is 1.1 mm can be calculated by linearly interpolating the calculated ejection speed.

[0056] In the above, the distance between the ejection port surface 201a and the recording medium 203 is measured by the distance detection sensor 204, but other methods may be used. For example, the thicknesses of various target recording media may be stored in the memory 303, and the user may select the target recording medium from the operation panel on the recording device 100 to set the corresponding distance. In such a configuration, it is not necessary to install a distance detection sensor.

[0057] Once the ejection speed at the distance between the ejection port surface 201a and the recording medium 203 is calculated, an adjustment value for the ejection timing is obtained based on the calculated ejection speed and the table stored in the memory 303, as in the first embodiment.

[0058] As described above, it is possible to calculate the ink droplet ejection velocity with higher accuracy by calculating the ink droplet ejection velocity based on the distance between the ejection port surface 201a of the print head 201 and the print medium 203. By adjusting the ejection timing based on such a highly accurate ejection velocity, it is possible to further suppress deviations in the landing position. (Third embodiment) Next, a third embodiment will be described. The ejection speed of ink droplets gradually decreases when a print head is used over a long period of time. If the ejection speed decreases after the ejection timing adjustment value is set, there is a risk that the landing position of ink droplets will be shifted with the set adjustment value. Therefore, in this embodiment, a form will be described in which the ejection timing adjustment value is reset at a predetermined timing after the ejection timing adjustment value has been set once. In this embodiment, parts that are similar to those in the above-mentioned embodiments will be omitted.

[0059] 10 is a flowchart showing a process for determining an adjustment value for the ejection timing from an adjustment pattern and calculating the ejection speed from the determined adjustment value. The process in FIG. 10 is performed by the sequence control unit 307 of the CPU 301 in accordance with a program stored in the memory 303, for example. This process is started when the printing apparatus is initially installed or when the print head is replaced with a new one. Alternatively, the process may be started by a user issuing an instruction from the operation panel of the printing apparatus 100 to print an adjustment pattern and adjust the ejection timing. The ink droplet ejection speed calculated by the process in FIG. 10 is set as the reference ejection speed.

[0060] First, in step S1101, an adjustment pattern for ejection timing is inspected. Specifically, an adjustment pattern for acquiring an adjustment value for ejection timing is printed, and the adjustment value is determined from the adjustment pattern.

[0061] FIG. 11 shows patterns used to adjust the misalignment between the forward and reverse printing directions in this embodiment. Vertical ruled line 901 is a ruled line pattern printed by 64 nozzles in each nozzle array during forward scanning, while vertical ruled line 902 is a ruled line pattern printed by 64 nozzles in each nozzle array during reverse scanning. The printing conditions for these patterns are a carriage speed of 25 inches / second and a drive frequency of 30 kHz. The patterns are five patterns in which the ejection timing during reverse scanning is changed so that the printing position of vertical ruled line 902 is changed in five steps from "-2" to "+2" in 1 / 1200 inch increments, with vertical ruled line 901 as the reference. Note that the "-" direction indicates that the printing timing is advanced relative to the reference, and the "+" direction indicates that the printing timing is delayed relative to the reference. From these adjustment patterns, the pattern with the smallest misalignment between the two ruled lines is selected, and the selected adjustment value is stored in memory 303. The ejection timing in the scanning direction in which the non-reference ruled line was printed is determined based on the selected adjustment value. If the recording device has an optical sensor on the carriage, the pattern with the least misalignment between the two vertical ruled lines may be detected automatically. Alternatively, the user may look at the recording paper on which the adjustment pattern is recorded and input the value of the pattern with the least misalignment between the two vertical ruled lines via the operation unit.

[0062] Next, the process proceeds to step S1102, where the ejection speed at the time when the adjustment pattern is printed is calculated from the adjustment value acquired in step S1101. Hereinafter, the ejection speed at the time when the adjustment pattern is printed is referred to as the reference ejection speed. The method for calculating the reference ejection speed will be described with reference to FIG. 4.

[0063] First, once the adjustment value is determined, the amount of deviation of the landing position from the reference ejection timing adjustment value (here, "0") can be determined. As explained with reference to FIG. 4, the deviation amount is Xa' - Xa. For example, if the adjustment value is determined to be "-1," the deviation is reduced by shifting the reference by 1 / 1200 inch. This is the deviation amount including deviations in the forward and backward directions, so the deviation amount Xa' - Xa due to scanning in one direction is 1 / 2400 inch. Note that the distance Xa between the ejection position at the reference ejection speed and the landing position is stored in advance in memory 303. As described above, since the deviation amount and Xa are known, the distance Xa' from the ejection position at the current reference ejection speed can be calculated.

[0064] As explained in Figure 4, the distance Xa' from the ejection position to the impact position at the current reference ejection velocity is Xa' = (H / Va') × Vcr. From this formula, the current reference ejection velocity Va' can be calculated using the following formula:

[0065] Va' = (H × Vcr) / Xa' The distance H between the ejection port surface 201a and the recording medium 203 is measured by the distance detection sensor 204. The scanning speed Vcr of the print head 201 is stored in advance in the memory 303. Then, as described above, the distance Xa' from the ejection position to the impact position at the current reference ejection speed is calculated from the distance Xa and the deviation amount obtained from the adjustment value determined from the pattern. The current reference ejection speed Va' can be calculated by substituting each value into the formula. The calculated current reference ejection speed Va' is stored in the memory 303. In this embodiment, patterns are printed when the distance between the ejection port surface 201a and the recording medium 203 is distance M1, distance M3, or distance M5, and the respective ejection speeds are calculated. The adjustment value is determined by the above process, and the reference ejection speed is calculated from the adjustment pattern.

[0066] As the print head 201 is used, the ejection speed decreases over time. When the ejection speed decreases, deviations in the landing position occur when printing is performed using adjustment values determined by the adjustment pattern. Therefore, at a predetermined timing after printing the adjustment pattern, the ejection speed is calculated using the droplet detection sensor 205 described in the first and second embodiments, and the attenuation rate of the ejection speed since the previous ejection speed calculation is determined. An adjustment value for the ejection timing is set based on this attenuation rate. Details will be explained using FIG. 13.

[0067] 12 is a diagram for explaining the reference ejection speed and the ejection speed calculated based on the detection time detected by the droplet detection sensor 205. Here, the detection time by the droplet detection sensor 205 is detected at a timing after the timing at which the adjustment pattern for calculating the reference ejection speed is printed.

[0068] Fig. 12(a) is a diagram showing the distance between the ejection port surface 201a and the platen 212 or the recording medium 203, and the output results of the detection time at each distance. The horizontal axis represents the distance (H1 to H5, etc.) between the ejection port surface 201a of the print head 201 and the light 404 of the droplet detection sensor 205, or the distance (M1 to M5) between the ejection port surface 201a and the recording medium 203. The vertical axis represents the detection time detected by the droplet detection sensor 205. Fig. 12(b) shows the ejection speed corresponding to the detection time and distance in Fig. 12(a).

[0069] The values indicated by the white circles in Figure 12(b) are the reference ejection velocities calculated in the process of Figure 10 when the distances between the ejection port surface 201a and the recording medium 203 are M1, M3, and M5, respectively. Although not actually calculated, the detection times when the reference ejection velocities corresponding to Figure 12(b) are obtained are indicated by the white circles in Figure 12(a). By finding an approximate curve of the velocity from the velocities indicated by the white circles in Figure 12(b), it is possible to calculate the ejection velocities corresponding to distances H1 to H5. The detection times and ejection velocities at this time are each indicated by a shaded circle surrounded by a dotted line.

[0070] Next, at predetermined timings, as in the first embodiment, the detection times detected by the droplet detection sensor 205 at distances H1 to H5 are shown as detection times T1' to T5', which are indicated by hatched circles surrounded by solid lines in Figure 12(a). Discharge velocities V1' to V4' calculated from the detection times T1' to T5' are shown by hatched circles surrounded by solid lines in Figure 12(b). An approximate curve of the discharge velocities can be obtained from the discharge velocities V1' to V4'.

[0071] FIG. 13 shows the ejection timing correction process. As described above, this process is performed at a timing after the timing at which an adjustment pattern for calculating the detection reference ejection speed for the detection time is printed. For example, this is when a predetermined time has elapsed since the previous ejection speed was calculated, when a predetermined number of ink droplets have been ejected, or when a predetermined number of sheets have been printed. In this embodiment, it is assumed that the process of FIG. 10 is completed before the process of FIG. 13 is started. The process of FIG. 13 is performed by the sequence control unit 307 of the CPU 301 in accordance with a program stored in the memory 303, for example.

[0072] First, in step S1201, the ejection speed of ink droplets ejected from the print head 201 is calculated by a process similar to the ejection speed detection process of Fig. 7 in the first embodiment. The calculated speeds are the ejection speeds V1' to V4' shown in Fig. 12(b).

[0073] Next, in step S1202, the ejection speed calculated in step S1201 is compared with the reference ejection speed obtained in the process of Fig. 10 to determine whether the ejection speed has changed. This determination is made based on whether the difference between the reference ejection speed and the speed calculated in step S1201 is equal to or greater than a threshold value stored in advance in memory 303. If the difference is equal to or greater than the threshold value, the process proceeds to step S1203. If the difference is not equal to or greater than the threshold value, the process proceeds to step S1205.

[0074] If the process proceeds to step S1203, the rate of decrease in the ink droplet ejection speed obtained in step S1201 relative to the reference ejection speed is calculated.

[0075] Next, proceeding to step S1204, a correction process is performed for the ejection timing adjustment value based on the rate of decrease from the reference ejection speed calculated in step S1203. Based on the attenuation rate, the adjustment value can be corrected by calculating how much to deviate from the adjustment value when the ink droplet ejection speed is the reference ejection speed.

[0076] Next, the process proceeds to step S1205, where the calculated discharge speed and the result of the correction process are stored in the memory 303. Then, in step S1206, a termination process is performed. The termination process is the same process as step S608 in FIG. 7 of the first embodiment.

[0077] As described above, by correcting the ejection timing adjustment value, it is possible to set an appropriate ejection timing adjustment value for the current ink droplet ejection speed, and it is possible to suppress deterioration in image quality.

[0078] 13 is completed, or a predetermined amount of time has elapsed, or a predetermined number of sheets have been printed, the ejection speed may be calculated using the droplet detection sensor 205. In this case, the ejection speed calculated in step S1201 of FIG. 13 is used as the reference speed, and an appropriate ejection timing adjustment value can be set by performing the processing of FIG. 13.

[0079] 13, in step S1204, the deviation in the ink landing position is corrected by correcting the adjustment value of the ejection timing, but other methods may also be used. For example, the pulse width of the drive pulse applied to the print head 201 to eject ink may be increased. By increasing the pulse width in accordance with the attenuation rate of the ejection speed, the ejection speed can be increased, and the ejection speed can be corrected.

[0080] In the above, the initial reference ejection speed is calculated from the adjustment pattern, but the ejection speed may also be calculated at the timing when the adjustment pattern is printed using the droplet detection sensor 205. Alternatively, the adjustment value may be determined based on the ejection speed calculated using the droplet detection sensor 205 first, and then the adjustment value may be updated by printing a pattern.

[0081] Furthermore, this embodiment can also be applied to a configuration that does not have the function of printing an adjustment pattern to obtain an adjustment value for the ejection timing, as long as the initial adjustment value is set based on the ejection speed calculated using the droplet detection sensor 205. [Explanation of symbols]

[0082] 100 Recording device 201 Recording head 203 Recording Media 204 Distance detection sensor 205 Droplet detection sensor 301 CPU 302 Sensor and motor control unit 303 Memory

Claims

1. a discharge head that discharges droplets from discharge ports formed on a discharge port surface; a detecting means having a light emitting portion that emits light and a light receiving portion that receives the light emitted by the light emitting portion; a droplet detection unit that detects droplets ejected from the ejection head based on the amount of light received by the light receiving unit, when the ejection head and the detection unit are positioned in a positional relationship for detection in which droplets ejected from the ejection head pass between the light emitting unit and the light receiving unit; a time detection means for detecting the time from when the ejection head starts ejecting the droplets until when the droplet detection means detects that the droplets have passed through the light; a calculation means for calculating the ejection speed of the droplets based on the time detected by the time detection means and the distance between the ejection port surface and the light emitted by the light emitting unit; A discharge device having a change unit that changes the distance between the ejection port surface of the ejection head and the detection unit in the positional relationship; the time detection means detects a first time from when droplets start to be ejected from the ejection port in a state where a distance between the ejection port surface of the ejection head and the light emitted by the light-emitting unit is a first distance to when the droplet detection means detects the droplets, and detects a second time from when droplets start to be ejected from the ejection port in a state where a distance between the ejection port surface of the ejection head and the light emitted by the light-emitting unit is a second distance different from the first distance by the changing means to when the droplet detection means detects the droplets; The ejection device is characterized in that the calculation means calculates the ejection velocity of the droplets based on the first distance, the second distance, the first time period, and the second time period.

2. 2. The ejection device according to claim 1, wherein the calculation means calculates the ejection velocity of the droplet based on the difference between the first distance and the second distance and the time difference between the first time and the second time.

3. 3. The ejection device according to claim 1, further comprising a timing control means for determining the timing of ejection of droplets when the ejection head records an image on a recording medium, based on the ejection speed calculated by the calculation means.

4. the changer changes the distance between the ejection port surface of the ejection head and the light emitted by the light-emitting unit in the positional relationship to a third distance different from the first distance and the second distance, the time detection means detects a third time that is a time from when the ejection of droplets from the ejection port starts in the third state until the droplet detection means detects the droplets; the calculation means calculates a discharge velocity based on the second distance, the third distance, the second time period, and the third time period; The ejection device according to any one of claims 1 to 3, characterized in that the ejection speed at a fourth distance different from the first distance, the second distance, and the third distance is calculated based on an ejection speed calculated based on the time detected by the time detection means at the first distance and the second distance, and an ejection speed calculated based on the time detected by the time detection means at the second distance and the third distance.

5. The ink jet head further includes a determination unit that determines a timing for ejecting droplets when the ejection head records an image on a recording medium, based on the ejection speed calculated by the calculation unit, the fourth distance is a distance between the ejection head and a recording medium on which the ejection head starts ejecting the droplets to record an image, 5. The ejection device according to claim 4, wherein the determining means determines the timing of ejecting droplets when recording on the recording medium based on the ejection speed at the fourth distance calculated by the calculating means.

6. 6. The ejection device according to claim 5, further comprising a measuring means for measuring the distance between the ejection head and the recording medium.

7. 7. The ejection device according to claim 3, wherein the determining means determines the ejection timing in accordance with a table showing the relationship between the ejection speed of the droplets and the ejection timing.

8. the ejection head records a pattern for adjusting the ejection timing on the recording medium; the calculation means calculates the droplet ejection speed based on the ejection timing determined based on the pattern; the time detection means detects the time from when the ejection head starts ejecting the droplets at a predetermined timing different from the timing at which the pattern is recorded until when the droplet detection means detects that the droplets have passed through the light, the calculation means calculates a discharge speed based on the time detected by the time detection means, The ejection device according to any one of claims 3 and 5 to 7, characterized in that the determination means determines the ejection timing from the ejection speed calculated by the calculation means based on the ejection timing determined based on the pattern and the ejection speed calculated based on the time detected by the time detection means.

9. The ejection head ejects droplets by applying a driving pulse to the ejection head. the ejection head records a pattern for adjusting the ejection timing on the recording medium; the calculation means calculates the droplet ejection speed based on the ejection timing determined based on the pattern; the time detection means detects the time from when the ejection head starts ejecting the droplets at a predetermined timing different from the timing at which the pattern is recorded until when the droplet detection means detects that the droplets have passed through the light, An ejection device as described in any one of claims 3 and 5 to 7, characterized in that the calculation means calculates the ejection speed based on the time detected by the time detection means, and the determination means determines the length of the drive pulse to be applied to the ejection head from the ejection speed calculated by the calculation means based on the ejection timing determined based on the pattern and the ejection speed calculated based on the time detected by the time detection means.

10. 10. The ejection device according to claim 8, wherein the ejection head records the pattern when the ejection head is attached to the ejection device.

11. 11. The ejection device according to claim 8, wherein the predetermined timing is a timing when a predetermined time has elapsed since the ejection speed was calculated by the calculation means.

12. 11. The ejection device according to claim 8, wherein the predetermined timing is a timing at which a predetermined number of droplets have been ejected after the ejection speed has been calculated by the calculation means.

13. an ejection signal generating means for generating an ejection signal; a drive pulse generating unit that generates a drive pulse for ejecting the droplets from the ejection opening of the ejection head in accordance with the input of the ejection signal, The ejection head ejects droplets from the ejection openings when the drive pulse is applied, The ejection device according to any one of claims 1 to 12, characterized in that the time detection means detects the time when the ejection signal generation means inputs the ejection signal to the drive pulse generation means as the time when the ejection of the droplets from the ejection port begins.

14. detecting droplets ejected from an ejection port formed on an ejection port surface of the ejection head based on the amount of light received by the light receiving unit, with the ejection head located at a detection position where the droplets pass between a light emitting unit that emits light and a light receiving unit that receives the light emitted by the light emitting unit; detecting a time from when the ejection head starts ejecting the droplet to when it is detected that the droplet has passed through the light; a method for calculating a droplet ejection velocity based on the detected time and a distance between the ejection port surface and light emitted by the light-emitting unit, detecting a first time period from when the ejection of droplets from the ejection port begins to when it is detected that the droplets have passed through the light, in a state where the distance between the ejection port surface of the ejection head at the detection position and the light emitted by the light-emitting unit is a first distance; changing a distance between the ejection head at the detection position and the light-emitting unit and the light-receiving unit to a second distance different from the first distance; detecting a second time from when the ejection of droplets from the ejection port begins to when it is detected that the droplets have passed through the light, in a state where the distance between the ejection port surface of the ejection head at the detection position and the light emitted by the light-emitting unit is the second distance; a method for calculating an ejection velocity of the droplet, the method comprising: calculating an ejection velocity of the droplet based on the first distance, the second distance, the first time, and the second time;

15. 15. The method for calculating the ejection velocity of the droplet according to claim 14, further comprising calculating the ejection velocity of the droplet based on the difference between the first distance and the second distance and the time difference between the first time and the second time.

Images