JP2002347224A - Apparatus and method for adjusting discharge amount of ink jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet head which can be utilized for a thin film- applying apparatus, a color filter-manufacturing apparatus or the like by suppressing dispersions in the discharge amount of liquid drops discharged from each nozzle. SOLUTION: Liquid drops are discharged at constant time intervals from nozzles and taken as an image. The image is analyzed, and flying characteristics of the liquid drops are calculated from only positions of the liquid drops in the image and compared with a target value. The discharge amount of each nozzle is adjusted to be constant in this manner.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge amount adjusting apparatus for an ink jet head which adjusts a discharge amount of droplets discharged from each nozzle by applying a discharge pulse to each nozzle of the ink jet head having a plurality of nozzles. And a discharge amount adjustment method.

[0002]

2. Description of the Related Art Conventionally, an ink jet head has been used mainly in an apparatus (ink jet printer) for forming an image by landing ink droplets (droplets) on paper.
In order to form a high-quality image, it is necessary to adjust the ejection amount from the nozzle with high precision in a production line. FIG.
Shows a method for adjusting the ejection amount of the ink jet head of Conventional Example 1. In FIG. 7, a droplet 2 is ejected from an ink jet head 1 and printing is performed on a paper surface 71. The printed dot diameter 72 was measured, and the dot diameter 7 corresponding to each nozzle was measured.
The ejection amount of each nozzle is adjusted so that 2 becomes uniform. FIG. 8 shows a method of adjusting the ejection amount of the ink jet head of the second conventional example. In FIG. 8, the droplet 2 is ejected from the nozzle 21 of the ink jet head 1 at a fixed position to capture the flying droplet 2, and the droplet position of the captured image (82 indicates an imaging region) And the flight characteristics (velocity / volume) of the droplet from the relationship between the droplet and the reference position 81 set in advance.
Is calculated to adjust the discharge amount of each nozzle.

[0003]

However, in the method of measuring the dot diameter, the dot diameter may be different even for the same discharge amount depending on the degree of ink bleeding on the paper surface. The amount cannot be constant. Further, in the method of calculating the flight characteristics, since the reference position is fixed, a measurement error due to the mounting position accuracy when the inkjet head is replaced, and a measurement error due to wobbling of the droplet caused by mechanical vibration are included. For this reason, it is difficult to use the apparatus in which adjustment of the nozzle discharge amount is highly required (for example, a thin film coating apparatus or a color filter manufacturing apparatus). In addition, fixing the reference position with high accuracy causes an increase in production time and production cost, and thus lowers productivity.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems, and provides a discharge amount adjusting apparatus and a discharge amount adjusting method for an ink jet head capable of adjusting the nozzle discharge amount with high accuracy in a short time and at low cost. The purpose is to:

[0005]

Means for Solving the Problems In order to solve the above problems, a discharge amount adjusting apparatus and a discharge amount adjusting method for an ink jet head according to the present invention have the following configurations. Claim 1
The present invention provides a synchronous timing signal generating means for outputting a discharge pulse generation timing signal, an irradiation timing signal, and an imaging timing signal at fixed time intervals and in synchronism with each other, and an inkjet apparatus in accordance with the discharge pulse generation timing signal. Irradiating means for irradiating droplets ejected from each nozzle of the ink jet head having a plurality of nozzles by a driving unit of the head according to the irradiation timing signal, and imaging for imaging the droplets according to the imaging timing signal Means, image analysis means for specifying any two adjacent droplets included in the captured image, and calculating a distance L between the two droplets;
Adjusting means for automatically adjusting the drive unit that determines the ejection amount of droplets of each nozzle of the inkjet head so as to approach a target value. .

According to a second aspect of the present invention, there is provided a synchronous timing signal generating means for outputting an ejection pulse generation timing signal, an irradiation timing signal, and an imaging timing signal at a constant time interval and synchronizing with each other; An irradiation unit configured to irradiate droplets ejected from each nozzle of the inkjet head having a plurality of nozzles by a driving unit of the inkjet head in accordance with a timing signal in accordance with the irradiation timing signal; and Imaging means for imaging a droplet; a distance L1 between a droplet closest to a nozzle surface and a droplet adjacent to the nozzle surface among droplets included in the captured image; Calculating the distance L2 between the droplet located farthest from the nozzle surface and the droplet adjacent thereto,
Image analysis means for calculating the ratio between L1 and L2; and the driving unit for determining the ejection amount of droplets from each nozzle of the inkjet head such that the ratio between the distance L1 and the distance L2 approaches a target value. Adjusting means for automatically adjusting the
A discharge amount adjusting device for an inkjet head, comprising:

According to a third aspect of the present invention, the adjusting means automatically adjusts the voltage of the ejection pulse of the driving section so that the distance L or the ratio of the distance L1 to the distance L2 approaches the target value. The ejection amount adjusting device for an ink jet head according to claim 1 or 2, wherein the adjustment is performed in a controlled manner.

According to a fourth aspect of the present invention, there is provided a synchronous timing signal generating step of outputting an ejection pulse generation timing signal, an irradiation timing signal, and an imaging timing signal at fixed time intervals and synchronizing each other with each other; An irradiation step of irradiating droplets ejected from each nozzle of the inkjet head having a plurality of nozzles by a driving unit of the inkjet head in response to a timing signal in accordance with the irradiation timing signal; and An imaging step of imaging a droplet, an image analysis step of identifying any two adjacent droplets included in the captured image, and calculating a distance L between the two droplets, and the distance L Before determining the ejection amount of droplets from each nozzle of the inkjet head so as to approach the target value. An adjusting step of automatically adjusting the drive unit, a discharge amount adjustment method for an ink jet head characterized by having a.

According to a fifth aspect of the present invention, there is provided a synchronous timing signal generating step of outputting an ejection pulse generation timing signal, an irradiation timing signal, and an imaging timing signal at fixed time intervals and synchronizing each other with each other; An irradiation step of irradiating droplets ejected from each nozzle of the inkjet head having a plurality of nozzles by a driving unit of the inkjet head in response to a timing signal in accordance with the irradiation timing signal; and An imaging step of imaging a droplet, a distance L1 between a droplet closest to a nozzle surface and a droplet adjacent to the nozzle surface among droplets included in the captured image, Distance L between the droplet farthest from the nozzle surface and the adjacent droplet
2 and an image analysis step of calculating a ratio between L1 and L2, and a discharge amount of droplets from each nozzle of the inkjet head so that the ratio between the distance L1 and the distance L2 approaches a target value. And an adjusting step of automatically adjusting the driving unit that determines the discharge amount of the ink jet head.

According to a sixth aspect of the present invention, in the adjusting step, the voltage of the ejection pulse of the driving unit is automatically adjusted so that the distance L or a ratio of the distance L1 to the distance L2 approaches the target value. The ejection amount adjusting method for an ink-jet head according to claim 4 or 5, wherein the adjustment is performed in an appropriate manner.

According to the present invention, the nozzle ejection amount is adjusted by calculating the flight characteristics (moving distance, ratio of moving distance) of the droplets only based on the positional relationship of the droplets in the imaged image. In addition, there is an effect that an ejection amount adjusting apparatus and an ejection amount adjusting method for an inkjet head which can adjust the nozzle ejection amount with high accuracy in a short time and at low cost without being affected by a measurement error due to mechanical vibration.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a preferred embodiment of the present invention.

Embodiment 1 An ejection amount adjusting device for an ink jet head according to Embodiment 1 will be described with reference to FIGS. 1 to 3 and FIG. FIG. 1 is a block diagram illustrating a configuration of a discharge amount adjusting device for an inkjet head according to a first embodiment of the present invention. The inkjet head 1 has a plurality of nozzles arranged in a horizontal row, and can eject droplets by applying a voltage (ejection pulse). FIG. 2 is a structural diagram of the inkjet head 1. The nozzle 21 indicates a nozzle of the inkjet head 1, and the nozzle surface 22 indicates a surface on which the nozzles 21 of the inkjet head 1 are arranged.

The droplet 2 is a discharged droplet that is in a flying state. The drive unit 4 has an electronic variable amplifier corresponding to each nozzle 21 and a non-volatile memory that stores a discharge amount adjustment value, and performs the generation of the discharge pulse for each nozzle 21. Also,
The inkjet head 1 and the drive unit 4 are a part of a product to be shipped, and are incorporated into the product after adjusting the ejection amount according to the present invention. The flexible cable 3 is a cable that connects the inkjet head 1 and the drive unit 4. The irradiating means 6 is a strobe for irradiating the ejected droplets with light. The image pickup means 7 picks up an image of the droplet being ejected and flying.
It is a CD camera. The synchronization timing signal generation means 5
An ejection pulse generation timing signal is transmitted to the driving unit 4, an irradiation timing signal is transmitted to the irradiation unit 6, and an imaging timing signal is transmitted to the imaging unit 7. These timing signals are at fixed time intervals, and are synchronized with each other. The image display device 11 is a display device that displays a captured image so that each droplet can be visually confirmed. The arithmetic processing unit 8 is a computer (for example, a personal computer) having the image analysis unit 9 and the adjustment unit 10. The image analysis means 9 analyzes the captured image and calculates the flight characteristics of the droplet. The adjusting means 10 automatically adjusts the voltage of the ejection pulse so that the flying characteristic of the droplet approaches a target value.

The irradiating means 6 and the imaging means 7 are provided with the droplet 2
Is installed at a position which is perpendicular to the flight direction of the object and symmetrical with the droplet 2 interposed therebetween. The inkjet head 1 is movable in the left-right direction with respect to a line connecting the irradiation unit 6 and the imaging unit 7.

The driving section 4 generates a discharge pulse having a discharge frequency of 8 kHz according to a discharge pulse generation timing signal.
The irradiation unit 6 outputs an irradiation timing signal (for example, 60H
In accordance with z), a strobe light is emitted, and the droplet 2 is irradiated. The imaging unit 7 images the droplet 2 according to an imaging timing signal (for example, 60 Hz).

FIG. 3 is a view showing a state in which the image display device 11 is displaying an image taken in this embodiment. The display screen 31 is a screen that displays the captured image so that each droplet 2 can be visually confirmed. The image processing area 32 is a display screen 3 of the droplet 2 discharged from the nozzle 21 to be adjusted.
1 is a region where the entire flight state can be confirmed, and indicates a region to be processed by the image analysis means 9. First, the inkjet head 1 is moved so that droplets ejected from the nozzle 21 located at the left end of the inkjet head 1 are displayed in the image processing area 32. The flight direction 33 indicates the flight direction of the droplet. The droplet 2a and the droplet 2b are formed on the nozzle surface 22 selected by the image analysis unit 9 in the image processing area 32.
The droplet closest to (the left end of the display screen 31) and the droplet adjacent to the droplet are shown. The image analysis means 9 calculates the distance L between the droplet 2a and the droplet 2b.

The adjusting means 10 compares the distance L with a target value determined by the conditions at the time of adjustment, and when target value> distance L, increases the voltage of the ejection pulse for the nozzle 21 of the drive unit 4 to increase the target. If the value <the distance L, the ejection amount of the nozzle 21 is adjusted by lowering the voltage of the ejection pulse. The adjusting unit 10 adjusts the ejection amount of the nozzle 21 by writing the ejection amount adjustment value to the address of the nonvolatile memory corresponding to the nozzle 21.

When the adjustment of the nozzle 21 is completed, the inkjet head 1 is moved by the same distance as the pitch of the nozzle 21. When the droplets ejected from the nozzle 21 adjacent to the nozzle 21 whose adjustment has been completed are displayed in the image processing area 32, the ejection amount of the nozzle 21 is adjusted by the same method as described above. By repeating this, the ejection amount of all the nozzles 21 is adjusted.

FIG. 5 is a flowchart showing an algorithm for calculating the distance between liquid droplets on a captured image and automatically adjusting the discharge amount of the nozzle 21. In step S1, the synchronization timing signal generator 5 outputs a synchronization timing signal. In step S2, 1 is set to the nozzle number N to be adjusted as an initial setting. In step S3, the inkjet head 1 ejects droplets at the set ejection pulse voltage. In step S4, the irradiating means 6 irradiates the droplet with light. In step S5, the imaging means 7 images the droplet. In step S6, the image analysis means 9 calculates the distance L between droplets on the captured image. In step S7, the distance L is compared with a target value,
If they match, the process proceeds to step S9. If they do not match, the process proceeds to step S8. In step S8, the adjusting means 10 changes the discharge pulse voltage of the target nozzle 21. When the target value> the distance L, the voltage of the ejection pulse is increased, and when the target value <the distance L, the voltage of the ejection pulse is decreased. In step S9, the next nozzle 21
The nozzle number N is incremented in order to adjust. In step S10, it is determined whether the adjustment has been completed for all nozzles 21. If the processing has been completed, the process ends. If the processing has not been completed, the process proceeds to step S3.

In the apparatus for adjusting the discharge amount of the ink jet head of the first embodiment, for example, even if the position of the ink jet head 1 on the screen is slightly shifted, the liquid droplets 2a and 2b
Does not change.

By adjusting the nozzle ejection amount based on the distance L between droplets calculated using only the droplet positions on the image thus captured, the position of the ink jet head 1 is not affected by the displacement. A discharge amount adjusting device for an inkjet head can be realized.

In this embodiment, the ejection amount is adjusted by using the liquid droplet closest to the left end of the display screen 31 in the image processing area 32 and the liquid droplet adjacent to the liquid droplet. Alternatively, the ejection amount may be adjusted using two droplets near an arbitrary fixed position in the image processing area 32.

<< Embodiment 2 >> An ejection amount adjusting device for an ink jet head according to Embodiment 2 will be described with reference to FIG. The ejection amount adjusting device for the inkjet head according to the second embodiment has the same configuration (FIG. 1) as the ejection amount adjusting device for the inkjet head according to the first embodiment. In the second embodiment, the functions of the image analysis unit 9 and the adjustment unit 10 are different from those of the first embodiment. FIG. 4 is a diagram illustrating a state in which the image display device 11 displays an image captured under the same conditions and method as in the first embodiment. The droplet 2c is a droplet located closest to the nozzle surface 22 in the image processing area 32. The droplet 2d is a droplet adjacent to the droplet 2c in the image processing area 32. Droplet 2
f is a droplet located farthest from the nozzle surface 22 in the image processing area 32. The droplet 2e is placed in the image processing area 32
Is a droplet adjacent to the droplet 2f.

The image analyzing means 9 comprises a droplet 2c, a droplet 2d,
The droplet 2e and the droplet 2f are specified, and the droplet 2c and the droplet 2
d, distance L1 (distance before deceleration), droplet 2e and droplet 2f
A distance L2 (distance after deceleration) is calculated, and a measurement ratio (L2 / L1) between the distance before deceleration and the distance after deceleration is calculated.

The measured ratio is compared with a target ratio determined by the conditions at the time of adjustment. If target ratio> measured ratio, the voltage of the ejection pulse for the nozzle 21 of the drive unit 4 is increased,
When the target ratio <the measurement ratio, the discharge amount of the nozzle 21 is adjusted by lowering the voltage of the discharge pulse.

When the adjustment of the nozzle 21 is completed, the ink jet head 1 is moved to the nozzle 2 in the same manner as in the first embodiment.
Move by the same distance as pitch 1. When the droplets ejected from the nozzle 21 adjacent to the nozzle 21 whose adjustment has been completed are displayed in the image processing area 32, the ejection amount of the nozzle 21 is adjusted by the same method as described above. By repeating this, the ejection amount of all the nozzles 21 is adjusted.

FIG. 6 is a flowchart showing an algorithm for calculating the ratio of the distance between two droplets on a captured image and automatically adjusting the discharge amount of the nozzle 21. In step S11, the synchronization timing signal generator 5 outputs a synchronization timing signal. In step S12, 1 is set to the nozzle number N to be adjusted as an initial setting. In step S13, the inkjet head 1 ejects droplets at the set ejection pulse voltage. Step S1
In 4, the irradiating means 6 irradiates the droplet with light. In step S15, the imaging means 7 images the droplet. In step S16, the image analysis means 9 calculates the distances L1 and L2 between the two droplets on the captured image and calculates the measurement ratio (L2
/ L1). In step S17, the measured ratio is compared with the target ratio. If they match, the process proceeds to step S19, and if they do not match, the process proceeds to step S18.
In step S18, the adjusting unit 10 changes the discharge pulse voltage of the target nozzle. When the target ratio> the measurement ratio, the voltage of the ejection pulse is increased, and when the target ratio <the measurement ratio, the voltage of the ejection pulse is decreased. In step S19, the nozzle number N is incremented to adjust the next nozzle. In step S20, it is determined whether adjustment has been completed for all nozzles. If the processing has been completed, the process ends. If the processing has not been completed, the process proceeds to step S13.

In the ejection amount adjusting device for an ink jet head according to the second embodiment, for example, when the device vibrates and the flying direction 33 of the droplet suddenly changes, the value L in the first embodiment is affected to some extent. However, since L1 and L2 of the second embodiment are affected by the same ratio, the L1 and L2 are affected.
The ratio (L2 / L1) to 2 does not change.

When the timing at which the droplets 2 are ejected from the nozzle 21 and the imaging timing of the imaging means 7 deviate from each other, the L in the first embodiment is slightly affected by the deviation, but the L in the second embodiment is affected. Since L1 and L2 are affected at the same ratio, L2 / L1 does not change.

By adjusting the nozzle discharge amount based on the ratio of the distance between two droplets on the image thus captured,
A discharge amount adjustment device for an inkjet head that is not affected by mechanical vibration or a measurement error due to a difference between a discharge timing and an imaging timing can be realized.

In the first and second embodiments, the adjusting means 10 compares the L or the L2 / L1 with a target value and automatically changes the discharge pulse voltage of the target nozzle. By adjusting the discharge amount, the time required to adjust the discharge amount per nozzle is short (about 4 seconds),
Even if the number of all nozzles is adjusted, the process is completed in a few minutes, so that the man-hour for adjusting the discharge amount of the inkjet head 1 can be reduced.

In the embodiment, the drive unit 4 has a plurality of electronic variable amplifiers and a nonvolatile memory, and the adjusting means 10 writes the adjustment values of each electronic variable amplifier in the nonvolatile memory. In another embodiment, the driving unit 4 has a plurality of amplifiers each having one variable resistor,
Adjusts each amplifier by rotating a variable resistor with an adjustment driver.

[0034]

As described above, according to the apparatus and method for adjusting the discharge amount of the ink jet head of the present invention,
Captures images when droplets are ejected from the nozzle at regular time intervals, calculates the distance between any adjacent droplets, and compares it with the target distance value. And the variation of the ejection amount of each nozzle can be controlled within ± 0.5%. Thereby, for example, an ink jet head that can be used for industrial applications such as a thin film coating apparatus and a color filter can be manufactured.

Further, according to the apparatus and method for controlling the discharge amount of the ink jet head of the present invention, the distance L1 between the droplet closest to the nozzle surface and the droplet adjacent thereto and the position farthest from the nozzle surface To calculate the distance L2 between a certain droplet and a droplet adjacent thereto and use the ratio L2 / L1 as an adjustment factor of the nozzle discharge amount, a mechanical error or a measurement error due to a difference between the discharge timing and the imaging timing is measured. The nozzle discharge amount can be adjusted without being affected.

Further, according to the apparatus and method for adjusting the discharge amount of the ink jet head of the present invention, after the image analysis result, the voltage of the discharge pulse of the target nozzle is automatically changed. Can be adjusted automatically. Thereby, the man-hour for adjusting the discharge amount of the inkjet head can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a discharge amount adjusting device for an inkjet head according to the present invention.

FIG. 2 is a structural view of an inkjet head 1 according to the present invention.

FIG. 3 is a diagram showing a state in which a captured image is displayed on an image display device 11 according to the first embodiment of the present invention.

FIG. 4 is a diagram showing a state in which a captured image is displayed on an image display device 11 according to a second embodiment of the present invention.

FIG. 5 is a flowchart illustrating an algorithm for calculating a distance between droplets on a captured image and automatically adjusting a nozzle discharge amount in the first embodiment of the present invention.

FIG. 6 is a flowchart illustrating an algorithm for calculating a ratio of a distance between two droplets on a captured image and automatically adjusting a nozzle discharge amount in Embodiment 2 of the present invention.

FIG. 7 is a diagram showing a method of adjusting the nozzle discharge amount of the ink jet head of Conventional Example 1.

FIG. 8 is a diagram showing a method of adjusting the nozzle discharge amount of the ink jet head of Conventional Example 2.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ink jet head 2 Droplet 3 Flexible cable 4 Driver 5 Synchronization timing signal generation means 6 Irradiation means 7 Imaging means 8 Arithmetic processing unit 9 Image analysis means 10 Adjustment means 11 Image display device 21 Nozzle 22 Nozzle surface 31 Display screen 32 Image processing Area 33 Flight direction 71 Paper surface 72 Dot diameter 81 Reference position 82 Imaging area

Claims (6)

[Claims] A synchronous timing signal generating means for outputting an ejection pulse generation timing signal, an irradiation timing signal, and an imaging timing signal at fixed time intervals and in synchronization with each other; and an ink jet head according to the ejection pulse generation timing signal. Irradiating means for irradiating droplets ejected from each nozzle of the inkjet head having a plurality of nozzles according to the irradiation timing signal, and imaging means for imaging the droplets according to the imaging timing signal And image analysis means for specifying any two adjacent droplets included in the captured image and calculating a distance L between the two droplets, such that the distance L approaches a target value. Adjusting means for automatically adjusting the driving unit that determines the ejection amount of droplets from each nozzle of the inkjet head; Discharge amount adjusting apparatus of an ink jet head characterized by having a. 2. A synchronous timing signal generating means for outputting an ejection pulse generation timing signal, an irradiation timing signal, and an imaging timing signal in synchronization with each other at fixed time intervals, and an inkjet head according to the ejection pulse generation timing signal. Irradiating means for irradiating droplets ejected from each nozzle of the inkjet head having a plurality of nozzles according to the irradiation timing signal, and imaging means for imaging the droplets according to the imaging timing signal And the distance L1 between the droplet closest to the nozzle surface among the droplets included in the captured image and the droplet adjacent thereto and the furthest from the nozzle surface among the droplets included in the captured image. An image analyzer that calculates a distance L2 between a droplet at a position and a droplet adjacent thereto and calculates a ratio between L1 and L2. A step, and adjusting means for automatically adjusting the driving unit that determines the ejection amount of the droplets from each nozzle of the inkjet head so that the ratio of the distance L1 and the distance L2 approaches a target value. A discharge amount adjusting device for an inkjet head, comprising: 3. The method according to claim 2, wherein the adjusting unit automatically adjusts the voltage of the ejection pulse of the driving unit such that the distance L or the ratio of the distance L1 to the distance L2 approaches the target value. The ejection amount adjusting device for an ink jet head according to claim 1 or 2, wherein: 4. A synchronous timing signal generating step of outputting an ejection pulse generation timing signal, an irradiation timing signal, and an imaging timing signal at fixed time intervals and synchronizing with each other, and an inkjet head according to the ejection pulse generation timing signal. An irradiation step of irradiating droplets ejected from each nozzle of the inkjet head having a plurality of nozzles according to the irradiation timing signal, and an imaging step of imaging the droplets according to the imaging timing signal An image analysis step of identifying any two adjacent droplets included in the captured image and calculating a distance L between the two droplets; and causing the distance L to approach a target value. The drive unit, which determines the ejection amount of droplets from each nozzle of the inkjet head, is automatically adjusted. Ejection amount adjustment method for an ink jet head, characterized in that it comprises an adjusting step of, a. 5. A synchronous timing signal generating step of outputting an ejection pulse generation timing signal, an irradiation timing signal, and an imaging timing signal at fixed time intervals and in synchronism with each other, and an inkjet head according to the ejection pulse generation timing signal. An irradiation step of irradiating droplets ejected from each nozzle of the inkjet head having a plurality of nozzles according to the irradiation timing signal, and an imaging step of imaging the droplets according to the imaging timing signal And the distance L1 between the droplet closest to the nozzle surface among the droplets included in the captured image and the droplet adjacent thereto and the furthest from the nozzle surface among the droplets included in the captured image. The distance L2 between the droplet at the position and the droplet adjacent thereto is calculated, and the ratio between L1 and L2 is calculated. An image analyzing step, and an adjusting step of automatically adjusting the drive unit that determines the ejection amount of droplets from each nozzle of the inkjet head so that the ratio of the distance L1 to the distance L2 approaches a target value. A method for adjusting the ejection amount of an inkjet head, comprising: 6. The method according to claim 6, wherein the adjusting step automatically adjusts the voltage of the ejection pulse of the driving unit such that the distance L or a ratio of the distance L1 to the distance L2 approaches the target value. The discharge amount adjusting method for an ink jet head according to claim 4 or claim 5, wherein: