JPH11138820A - Method and system for measuring liquid drop jet characteristic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a system for measuring jet characteristic of ink drops whereby ink drops to be measured are surely specified from a picked-up image and a jet characteristic of the ink drops can be measured highly accurately. SOLUTION: Images of an ink drop 5 jetted from a nozzle hole which are picked up at a delay reference time after a fixed time from a jet start and at a delay increase time after a fixed time from the delay reference time are processed, thereby specifying positions of an object to be picked up at the delay reference time and at the delay increase time. Whether or not the object to be picked up is the ink drop 5 a jet characteristic of which is to be measured is judged on the basis of a relative positional relationship of the object to be picked up at the delay reference time and at the delay increase time. When the positions of the object to be picked up at the delay reference time and delay increase time are within a range of a movement amount corresponding to a jet speed, it is so judged that the object to be picked up is the ink drop 5. If the positions are outside the range, the object to be picked up is judged not to be the liquid drop 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and system for measuring the ejection characteristics of droplets by imaging droplets ejected from nozzle holes and measuring the ejection characteristics of the droplets.
The present invention relates to a method and a system for measuring a droplet ejection characteristic capable of specifying a droplet of an ejection characteristic measurement target from a captured image and measuring the droplet ejection characteristic with high accuracy.

[0002]

2. Description of the Related Art Conventionally, an ink jet printer has been known as an image forming apparatus for forming an image by flying ink droplets (droplets). The ink jet printer emits ink droplets ejected from nozzle holes of a printer head on paper. To form an image. In an ink jet printer of this type, for example, as shown in FIG. 18, the printer head 1 moves in the main scanning direction with the nozzle surface 3 on the lower surface side in which the nozzle holes 2 are arranged facing the paper surface, and the paper surface is moved. An image is formed by moving in the sub-scanning direction, and dot quality, dot position accuracy, density unevenness, sharpness, and the like are evaluated as the quality of the image.

In an ink-jet printer, the superiority of these evaluation items largely depends on the ejection characteristics of the ink droplets 5 by the printer head 1, so that the image quality of the ink-jet printer is improved and secured not only at the time of development but also at the time of mass production. Therefore, it is necessary to measure and adjust the ejection characteristics (ejection speed, ejection angle, and the like) of the ink droplets 5 with the printer head 1 alone with high accuracy.

[0004] The ejection characteristics of the ink droplet 5 are as follows.
It is conceivable to image the ink droplet 5 ejected from the side and obliquely and measure it from the reference position and the positional relationship with the nozzle hole 2.

[0005]

However, FIG.
As shown in (1), if dirt 6 or ink 7 adheres to an optical system such as a lens for imaging the ink droplet 5 or the background of the ink droplet 5, the dirt is measured from the captured video (imaging screen) W. There is a possibility that the ink droplet 5 may be erroneously specified as the target object, and there is a problem that the measurement accuracy is reduced and the reliability is impaired. The wiping of the dust 6 and the ink 7 so as not to affect the imaging of the ink droplets 5 requires monitoring the captured image W at all times, and it is difficult to distinguish them because the ink droplets 5 are extremely fine. .

[0006] From this, the inventor of the present invention has intensively developed to solve this problem.
And invented that measurement is performed by combining measurement 1 to measurement 3. In the measurement 1, since the ink droplets 5 are imaged in a certain range, as shown in FIG. 20, the captured image W is binarized and the area is outside the reference range in which the fluctuation of the ink droplets 5 is considered. Is an image of dirt such as dust 6 and ink 7 and is not an object to be measured. As the measurement 2, as shown in FIG. 20, the ink droplet 5 flies in a spherical shape after being ejected from the nozzle hole 2 and is imaged as a circular image. The degree coefficient is calculated, and the one outside the reference range in consideration of the variation of the circularity of the ink droplet 5 is assumed to be a dirt such as dust 6 or ink 7 and not a measurement object. In measurement 3, since the ink droplet 5 flies within a certain range and is captured as a substantially similar video when a predetermined time has elapsed from the start of the ejection operation, the ink droplet 5 is set in the captured video W as shown in FIG. If the degree of pattern matching with the reference image in the window S is out of the reference range in consideration of the fluctuation of the ink droplet 5, it is assumed that the image is a dirty image such as dust 6 or ink 7 and is not an object to be measured.

However, in the above-described measurements 1 and 2, binarization is performed using the difference in luminance between the object to be measured and its surroundings.
Since the ink droplets 5 and dirt 6 and dirt such as the ink 7 are determined, the influence of the fluctuation of the measured light amount and the state of the lower surface of the printer head 1 is large. The dirt is naturally determined to be a measurement target, and it is difficult to always distinguish the ink droplet 5 from the dirt.

In measurements 1 to 3, when the reference range is narrowed, the possibility of determining that the ink droplet 5 is not an object to be measured increases, and when the reference range is widened, stains other than the ink droplet 5 are determined to be an object to be measured. In addition to increasing the possibility of contamination, dirt such as dust 6 and ink 7 that approximates the ink droplet 5 is naturally determined to be a measurement target. In short, it is possible to determine that the stains other than the ink droplets 5 are not objects to be measured with a certain degree of accuracy in these Measurements 1 to 3, however, in consideration of use during mass production, it is necessary to check the captured image W. It is necessary to further improve the reliability of the judgment in order to automate without any problem.

When measuring the ejection characteristics of droplets (ink droplets) in a nozzle head having nozzle holes, such as the above-described printer head of an ink jet printer, the driving frequency of the nozzle head, the speed of the droplets, etc. In some cases, images of a plurality of droplets exist in the captured image. In order to accurately measure the ejection characteristics of the droplet ejected from the nozzle hole when an image of a plurality of droplets exists in the captured image as described above, a plurality of droplets in the captured image are required. , It is necessary to specify the droplet to be measured for the ejection characteristic.

FIGS. 22 (a) to 22 (d) exemplify captured images W when the driving frequency of the nozzle head and the speed (2 to 15 m / s) of the droplet 5 are changed. Reference numeral 2 in the drawing is a nozzle hole. FIG. 22A shows a captured image W when the nozzle head is driven at a relatively low frequency (for example, 1 kHz).
In the photographed image W, only an image of one droplet 5 exists. Therefore, it is not necessary to specify the droplet whose ejection characteristics are to be measured. FIGS. 22B to 22D show captured images W when the nozzle head is driven at a relatively high frequency (for example, 12 kHz). FIGS. 22B and 22C show the captured images W when the speed of the droplet 5 is low and medium, respectively. Exists. Therefore,
In order to accurately measure the ejection characteristics of the droplet 5, it is necessary to specify the droplet whose ejection characteristics are to be measured from a plurality of droplets in the captured image W. FIG. 22D shows a captured image W in the case where the speed of the droplet 5 is high, and only the image of one droplet 5 exists in the captured image W as in FIG. do not do. Therefore, it is not necessary to specify the droplet whose ejection characteristics are to be measured.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to reliably specify a droplet to be measured for an ejection characteristic from a captured image and to measure the ejection characteristic of the droplet with high accuracy. It is an object of the present invention to provide a method and a system for measuring the ejection characteristics of the obtained droplet.

[0012]

In order to achieve the above object, a first aspect of the present invention is to provide a method of measuring the ejection characteristics of a droplet by imaging a droplet ejected from a nozzle hole. A measurement method, comprising: performing image processing on an image captured at a delay reference time after a lapse of a certain time from the start of the injection operation and at a delay increase after a lapse of a certain time from the delay reference time; And determining, based on a relative positional relationship between the imaging target and the delay reference time and the delay increasing time, whether or not the imaging target is a droplet of an ejection characteristic measurement target. Is what you do.

In the method for measuring the ejection characteristics of a droplet according to the first aspect, imaging is performed at a delay reference when a predetermined time has elapsed after the start of the ejection operation, and imaging is performed again when the delay increases after a further predetermined time has elapsed. Is performed, the position of the object to be imaged is specified by image processing of both the captured images. Then, it is determined whether or not the imaging target is a droplet whose ejection characteristic is to be measured based on the relative positional relationship of the imaging target at the time of the delay reference and at the time of the delay increase. Therefore, since the ejected droplet moves between the delay reference time and the delay increase time, when the positions of both imaging objects do not coincide with each other and move by a certain amount, the imaging object moves through the nozzle hole. When the position of the object to be imaged is not moving in accordance with the position of the object to be imaged, it is determined that the object to be imaged is not the ejected droplet because the object to be imaged is dirt attached thereto. You. By the above determination, the droplet to be ejected and measured can be specified from the captured image.

According to a second aspect of the present invention, in the method of the first aspect, the position of the object to be imaged at the time of the delay reference and at the time of the delay increase is out of the range of the movement amount according to the ejection speed. Sometimes, it is determined that the object to be imaged is not a droplet whose ejection characteristics are to be measured. In the droplet ejection characteristic measuring method according to the second aspect, the positional relationship between the delay reference time and the delay increase of the imaging target object specified by the image processing of the captured image is out of the range of the movement amount according to the ejection speed. Sometimes, it is determined that the object to be imaged is not an ejected droplet. Therefore, for example, when only the lower limit value is set as the range of the movement amount according to the droplet ejection speed between the delay reference time and the delay increase time, when the imaging object does not move beyond the lower limit value ( In this case, it is determined that the imaging target is an attached dirt or the like that has moved due to vibration or the like and is not an ejected droplet. When an upper limit is also set as the range, for example, it is determined that the object is an image that happens to be taken across the imaging range and is not an ejected droplet.

According to a third aspect of the present invention, in the method of the first or second aspect of the present invention, the window for image processing and the delay increase time which elapses a predetermined time from the delay reference time are set by using the ejected droplet. Are set so that the positions of the delay reference time and the delay increase can be specified. In the method for measuring the ejection characteristic of a droplet according to the third aspect, a window for image processing and a delay increase time from the delay reference time can be specified so that the ejected droplet can be identified as a different position to which the ejected droplet has moved during the delay reference time and the delay increase. Is set. Therefore, the ejected droplet is specified at each position moved by a movement amount corresponding to the ejection speed, and it is not determined that the ejected droplet is not the droplet whose ejection characteristics are to be measured. In addition, these windows and the delay increase time may be set to necessary and sufficient conditions, and it may be set so that a part of the captured video is subjected to image processing.

According to a fourth aspect of the present invention, there is provided a droplet ejection characteristic measuring system for measuring droplet ejection characteristics by imaging droplets ejected from a nozzle hole. Imaging means for illuminating the liquid droplets by the illumination means to image the liquid droplets; and performing image processing on an image taken at a delay reference time after a certain time has elapsed from the start of the ejection operation and at a delay increase after a certain time from the delay reference time. Position specifying means for specifying the position of the imaging target at the time of the delay reference and at the time of increasing the delay; and measuring the ejection characteristics of the imaging object based on the relative positional relationship between the reference of the imaging and the time of the increase of the delay. Determining means for determining whether or not the target is a jetted liquid droplet. In the droplet ejection characteristic measuring system according to the fourth aspect, imaging is performed by the imaging means at a delay reference when a predetermined time has elapsed after the start of the ejection operation, and again when the delay has increased after a predetermined time has elapsed. After the imaging is performed, the position of the imaging target is specified by the position specifying means by image processing of both the captured images. Then, the determining means determines whether or not the imaging target is a droplet whose ejection characteristic is to be measured, based on the relative positional relationship between the imaging target at the time of the delay reference and the time of the delay increase. Therefore, since the ejected droplet moves between the delay reference time and the delay increase time, when the positions of both imaging objects do not coincide with each other and move by a certain amount, the imaging object moves through the nozzle hole. When the position of the object to be imaged is not moving in accordance with the position of the object to be imaged, it is determined that the object to be imaged is not the ejected droplet because the object to be imaged is dirt attached thereto. You. By the above determination, the droplet to be ejected and measured can be specified from the captured image.

A fifth aspect of the present invention is a method for measuring the ejection characteristics of a droplet by imaging a droplet ejected from a nozzle hole and measuring the ejection characteristics of the droplet, wherein a predetermined time has elapsed since the start of the ejection operation. The image taken at the time of the delay reference time and when the delay has increased by a certain time after the delay reference time is image-processed to specify the delay reference time and the position of the delay increase of the imaging target, and the delay reference of the imaging target is determined. Time and the speed of the imaging target is estimated based on the position at the time of the delay increase, and the droplet of the ejection characteristic measurement target in the captured image is specified based on the estimated value of the speed. is there. In the method of measuring the ejection characteristics of a droplet according to the fifth aspect, when a plurality of droplets, which are objects to be imaged, are present in a captured image, such as when the droplet is ejected by relatively high frequency driving, the imaging is performed. The speed of the imaging target is roughly estimated based on the position of the arbitrary imaging target in the video at the time of the delay reference and at the time of the delay increase. Based on the estimated value of the velocity, the position of the droplet whose ejection characteristic is to be measured at the time of the delay reference is calculated. The imaging target existing at the position of the droplet at the time of the calculated delay reference can be specified as the droplet of the ejection characteristic measurement target.

According to a sixth aspect of the present invention, there is provided a droplet ejection characteristic measuring system for imaging a droplet ejected from a nozzle hole and measuring the ejection characteristic of the droplet, wherein the droplet ejected from the nozzle hole is provided. Imaging means for illuminating the liquid droplets by the illumination means to image the liquid droplets; and performing image processing on an image taken at a delay reference time after a certain time has elapsed from the start of the ejection operation and at a delay increase after a certain time from the delay reference time. Position specifying means for specifying the position of the imaging object at the time of the delay reference and at the time of increasing the delay, and calculating means for roughly estimating the speed of the imaging object based on the position of the imaging object at the time of the delay reference and at the time of increasing the delay When,
Droplet specifying means for specifying a droplet to be measured for an ejection characteristic in a captured image based on the estimated value of the speed is provided. In the droplet ejection characteristic measuring system according to the sixth aspect, when a plurality of droplets to be imaged are present in a captured image, such as when droplets are ejected by relatively high-frequency driving, an imaging unit is provided. The position of an arbitrary object to be imaged in the image captured in the step (a) at the time of the delay reference and at the time of the delay increase is specified by the position specifying means. Based on the position of the imaging target at the reference time of the delay and at the time of the increase of the delay, the speed of the imaging target is roughly estimated by the calculating means.
Then, the droplet identifying means calculates the position of the droplet of the ejection characteristic measurement target at the time of the delay reference based on the approximate value of the velocity, and the imaging target imaged at this position is the liquid of the ejection characteristic measurement target. Can be identified as drops.

A seventh aspect of the present invention is a method for measuring the ejection characteristics of a droplet by imaging a droplet ejected from a nozzle hole and measuring the ejection characteristics of the droplet, wherein a predetermined time has elapsed since the start of the ejection operation. The image taken at the time of the delay reference is image-processed to identify the positions of two consecutive imaging objects in the imaged liquid image, and the positions of the two imaging objects at the time of the delay reference and the ejection period of the droplets , The speed of the object to be imaged is estimated based on the calculated value, and the droplet of the ejection characteristic measurement target in the captured image is specified based on the estimated value of the speed. According to the droplet ejection characteristic measuring method of claim 7, when a relatively large number of droplets to be imaged are present in the captured image, such as when droplets are ejected by higher-frequency driving, Identify the positions of any two consecutive droplets of the imaging target in the captured video, and determine the position of the two imaging targets based on the delay reference time and the ejection period of the droplet. Approximate speed. Based on the estimated value of the speed, the position of the droplet of the ejection characteristic measurement target at the time of the delay reference is calculated, and the imaging target imaged at this position can be specified as the droplet of the ejection characteristic measurement target. (Hereinafter, margin)

An eighth aspect of the present invention is a droplet ejection characteristic measuring system for imaging a droplet ejected from a nozzle hole and measuring the ejection characteristic of the droplet, wherein the droplet ejected from the nozzle hole is measured. Imaging means for illuminating the liquid droplets by the illuminating means to image the liquid droplets; and processing two images in the imaged liquid image by processing the image imaged at the time of the delay reference after a predetermined time has elapsed from the start of the ejection operation.
Position specifying means for specifying the positions of two imaging targets;
Calculating means for estimating the speed of the imaging object based on the position of the imaging object at the delay reference time and the ejection period of the droplet; and measuring the ejection characteristics in the imaged image based on the estimated value of the speed. And a droplet specifying means for specifying the liquid droplets. In the droplet ejection characteristic measuring system according to the eighth aspect, when a relatively large number of droplets to be imaged are present in a captured image, such as when droplets are ejected by higher frequency driving, imaging is performed. The position of the droplet, which is any two consecutive imaging targets, in the image captured by the means is specified by the position specifying means. Based on the positions of the two imaging targets at the reference time of the delay and the ejection period of the droplet, the speed of the imaging targets is roughly estimated by the calculating means. Then, the droplet identifying means calculates the position of the droplet of the ejection characteristic measurement target at the time of the delay reference based on the approximate value of the velocity, and the imaging target imaged at this position is the liquid of the ejection characteristic measurement target. Can be identified as drops.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 13 are diagrams showing an example of a droplet ejection characteristic (velocity) measuring system to which the present invention can be applied. FIGS. 1 to 7 show a first example, and FIGS. 8 to 13 show a second example. It is a figure showing an example.

First, the configuration of the droplet ejection characteristic measuring system according to the first example will be described with reference to FIGS. In FIGS. 1 and 2, a droplet ejection speed measuring system is a printer head as a nozzle head that ejects an ink droplet 5 as a droplet from a nozzle hole 2 when an inkjet printer as an image forming apparatus forms an image. 1 is evaluated. The ejection characteristic measuring system includes an illumination lamp 11 as an illumination unit for irradiating the ink droplets 5 ejected from the printer head 1 with light, and a CCD camera as an imaging unit for imaging the ink droplets 5 ejected from the printer head 1. The image processing apparatus includes an image processing device 13 that captures a captured video and performs image processing, and an arithmetic device 14 that calculates the ejection characteristics of the ink droplet 5 based on the result of the image processing. For example, 64 nozzle holes 2 of the printer head 1 are formed in the longitudinal direction of the head and two rows are formed in a direction perpendicular to the longitudinal direction (FIG. 1).
8).

In the ink jet printer, the printer head 1 is mounted on the head holding member 4 such that the nozzle surface 3 having the nozzle hole 2 formed above the paper surface to be conveyed faces at a height h of about 1 mm. Lighting lamp 11
The CCD camera 12 is positioned and fixed so as to image a position below the nozzle surface 3 which is a position on the paper by a distance h from the lateral direction. Further, in order to measure the dot position accuracy by the ink droplet 5 in accordance with the evaluation of the image quality, the same ink droplet 5 can be simultaneously imaged from two directions (two orthogonal directions) of main scanning and sub-scanning. FIG.
The illumination direction and the imaging direction are made coincident with the X-axis and Y-axis directions shown in FIG.
And CCD cameras 12x and 12y.
For this reason, as shown in FIG. 3, the image W captured by the CCD cameras 12x and 12y is such that the position of the paper surface separated by the distance h from the nozzle surface 3 of the printer head 1 is at the center C in the vertical direction, and the nozzle hole 2 The position is set to be the center C in the horizontal direction.

The illumination lamps 11x and 11y and the CCD cameras 12x and 12y are opposed to each other with the nozzle hole 2 positioned therebetween. The CCD cameras 12x and 12y are adapted to discharge the ink droplets 5 ejected from the nozzle hole 2. It is arranged so that light from the illumination lamps 11x and 11y to be illuminated is directly taken in. For this reason, the CCD cameras 12x and 12y
Captures an image in which the periphery of the ink droplet 5 is white with high luminance and the ink droplet 5 itself is black with low luminance in a light-shielded portion, regardless of the color of the ink droplet 5 and the background.

The image forming apparatus 13 has a driving frequency of 5 when forming an image with a dot density of 300 DPI, for example.
Since the printer head 1 is driven by the piazo driving waveform of kHz (voltage waveform for driving the pierzo element that ejects the ink droplet 5) to eject the ink droplet 5 from the nozzle hole 2, the ink at the position on the paper surface under the same conditions In order to measure the characteristics of the droplet 5, when the CCD cameras 12x and 12y are driven, the timing at which the ink droplet 5 reaches the center of the captured image W shown in FIG. Of the illumination lamps 11x, 1
1y is designed to emit strobe light. And
CCD cameras 12x, 12 imaged at the above timing
Image processing is performed on the image of each y to extract (identify) the image of the ink droplet 5 to be measured, specify the position coordinates of the center, and determine the center C in the image W as the origin (reference position). The position coordinates ((Δx, Δy), Δz) of the center of the ink droplet 5 are specified, and the diameter D of the ink droplet 5 is specified. That is, the image processing device 13 uses the ink droplet 5
And a position specifying unit that specifies the position of the ink droplet 5 from the reference position in the image captured when a predetermined time has elapsed from the ejection of the ink droplet. The driving frequency may be set to another frequency such as 1 kHz or 12 kHz.

The image processing device 13 is, specifically, a CC
When the ink droplet 5 is extracted (identified) from the images W captured by the D cameras 12x and 12y and used as a measurement target, the image W is determined in advance as described in Measurements 1 and 2 described above. The threshold value is binarized, and an image in the reference range in which the area takes into account the variation of the ink droplet 5 or an image in the reference range in which the variation in the circularity of the ink droplet 5 is considered as the ink droplet 5, Alternatively, as described in Measurement 3 described above, an image within a reference range in which the degree of pattern matching with the reference image in the window S set in advance is determined in consideration of the fluctuation of the ink droplet 5 is specified as the ink droplet 5. The reference range (reference value) deviates to some extent from the maximum and minimum of the ink droplet 5 ejected from the nozzle hole 2 around the value of the standard ink droplet 5. Even if the measurement target ink Set to so as to extract as 5.

The arithmetic unit 14 calculates the position coordinates ((Δ
x, Δy), Δz) and the diameter D of the ink droplet 5, and calculate the ejection characteristics of the ink droplet 5 in terms of a bond, an ejection speed, and an ejection direction by an arithmetic expression described below.
By attaching a four-fold lens to each of the CD cameras 12x and 12y having a normal imaging magnification and a pixel length of about 10 μm, and making one pixel length, which is the measurement resolution, about 3 μm, the injection speed measurement accuracy is ± It is set to be 20 mm / sec. The distance h (the distance h to the paper surface) from the nozzle surface 3 (nozzle hole 2) of the printer head 1 used in this arithmetic processing is measured and set in advance in advance. In addition,
The distance h may be measured by lowering the magnification so that the nozzle surface 3 of the printer head 1 is included in the image W captured by the CCD cameras 12x and 12y to perform image processing on the image captured and actually measure the distance h. Alternatively, the scale may be brought into contact with the nozzle surface 3 to actually measure the distance h to the center C in the captured image W, or similarly measured by a non-contact laser displacement meter.

The illumination lamps 11x and 11y emit strobe light in synchronization with the timing at which the ink droplet 5 reaches the center of the picked-up image W shown in FIG. 3, but the light emitted from the ink droplets 5a and 5b shown in FIG. CCD camera 12x, 1
There is a possibility that the measurement may deviate from the captured image W of 2y, or an erroneous measurement may occur due to the image of the ink droplet 5 that is not the object to be measured. Therefore, before the measurement is started, the timing (delay time from the ejection) at which the illumination lamps 11x and 11y emit strobe light is changed while observing the captured image W, and the change time of the timing is imaged. By tentatively calculating the speed of the ink droplet 5 from the displacement amount of the position of the ink droplet 5, erroneous measurement is prevented. Also, as described later, the illumination lamps 11x and 11y
It is possible to prevent erroneous identification of a dust or the like whose imaging position does not change even if the strobe light emission timing is changed as the ink droplet 5.

Next, the measurement of the ejection characteristics of the ink droplets 5 ejected by the printer head 1 will be described with reference to the flowchart shown in FIG. The illumination lamps 11x and 11y and the CCD power cameras 12x and 12y are set such that when the printer head 1 is mounted on the head holding member 4, the distance h from the nozzle surface 3 to the center C of the image W is approximately 1 mm. Have been.

First, the printer head 1 is set on the head holding member 4 (step P1), and the CCD which has started imaging
The distance h from the center C in the captured images W of the cameras 12x and 12y to the nozzle surface 3 is actually measured, and the distance h is set and input from an operation unit (not shown) of the arithmetic unit 14 (step P).
2). Next, the printer head 1 is driven to drive the ink droplets 5.
After a period of time from when the ejection of the ink droplet 5 is started to when the ejection is stabilized, a predetermined time is delayed from the ejection of the ink droplet 5 in FIG.
The illumination lamp 11 emits a strobe light at the timing when the ink droplet 5 reaches the center of the image W shown in FIG.
By driving x and 11y, it is confirmed whether or not the ink droplet 5 is an ink droplet whose ejection characteristics are to be measured (hereinafter, referred to as a “measurement object”) (whether the ejection of the ink droplet 5 and the strobe light emission are synchronized). (Step P3).

Next, the imaging of the ink droplet 5 is started (step P4), and after one or several images are captured, the ejection of the ink droplet 5 is stopped (step P5). It should be noted that the number of times of imaging of the ink droplet 5 may be plural in order to increase the measurement accuracy, for example, by averaging the image processing results.
Since the ejection of the ink droplets 5 from the printer head 1 does not vary greatly, it may be calculated only from one image processing result.

Thereafter, the volume of the ink droplet 5, the ejection speed,
Calculate the injection direction and measure the injection characteristics (Step P
6) After the arithmetic processing is completed and it is confirmed that no error has occurred in the imaging or the arithmetic processing, the printer head 1 is detached from the head gripping member 4 (step P7), and this processing ends. The measurement of the ejection characteristics in Step P6 is performed by calculating the diameter D of the ink droplet 5 and the position coordinates ((Δx, Δy), with respect to the center C in the captured images Wx and Wy) specified by the image processing device 13 performing image processing from the image processing device 13. Δz) is calculated. Since the measurement accuracy at this time depends on the measurement accuracy of the device, it is about ± 3 μm, ± 20 mm /
sec.

Specifically, the volume V of the ink droplet 5 is as shown in FIG.
Is calculated as follows using the diameter D of the ink droplet 5 specified from the image W captured by the CCD camera 12x or 12y.

[Number 1] V = πD ^3/6

Further, the ejection speed S of the ink droplet 5 is determined by the picked-up images Wx, Wx of the CCD cameras 12x, 12y shown in FIG.
y, the position coordinates ((Δx, Δ
y) and Δz), the actual injection distance L is obtained by calculating and combining the apparent injection distances Lx and Ly for each of the X-axis and Y-axis directions. Using the delay time T, it is calculated as follows.

(Equation 2)

Further, θ of the ejection direction of the ink droplet 5 shown in FIG. 6 is calculated as follows using the value used in the above calculation.

(Equation 3)

At this time, the ink droplets 5
When the nozzles 2 are vertically ejected from the nozzle holes 2, the images Wx and Wy captured by the CCD cameras 12x and 12y become the images shown in FIG. The ejection speed S of the droplet 5 is calculated (the ejection direction θ is 0 degree). In addition, the ejection direction θ indicates an included angle between the nozzle surface 3 of the printer head 1 and the vertical direction.
It goes without saying that the included angle between the X axis and the Y axis may be calculated.

Therefore, the volume V and the ejection direction θ of the ink droplet 5 are about ± 3 μm, and the ejection speed is ± 2 μm.
It can be measured with a measurement accuracy of 0 mm / sec. For example, the allowable width of the ejection speed required when forming an image with a dot density of 300 DPI (50 mm / sec)
Can be fully satisfied.

Next, a second example of a droplet ejection characteristic measuring system to which the present invention can be applied will be described with reference to FIGS. In addition, since this example is configured substantially in the same manner as the above-described first example, the same components are denoted by the same reference numerals and described.

In this embodiment, the illumination lamps 11x and 11y and the CCD cameras 12x and 12y
, An image processing device 13 and an arithmetic device 14, but as shown in FIG.
y and the CCD cameras 12x and 12y, the nozzle surface so that both the ink droplet 5 located at a distance h of about 1 mm from the nozzle surface 3 and the nozzle hole 2 of the nozzle surface 3 can be captured in the captured images Wx and Wy. An angle (elevation angle) between the illumination direction and the imaging direction with respect to 3 is set to 10 degrees and is fixed.

Here, the nozzle surface 3 of the printer head 1
Is generally water-repellent, and the illumination lamp 11
A reflection surface that efficiently reflects the illumination light of x and 11y is configured. For this reason, the CCD cameras 12x and 12y take in the illumination light from the illumination lamps 11x and 11y reflected by the nozzle surface 3 and are not reflected by the nozzle holes 2 and are shielded by the ink droplets 5. By taking in the illumination light from the illumination lamps 11x and 11y, it is possible to capture an image capturing both the ink droplet 5 and the nozzle hole 2 in the captured image W as shown in FIG.

Therefore, the image processing device 13 controls each of the CCD cameras 12x and 12y captured by the illumination lamps 11x and 11y emitting strobe light in synchronization with the timing at which the ink droplet 5 reaches the position (distance h) on the paper surface. While the position of the nozzle hole 2 and the position of the ink droplet 5 in the picked-up images Wx and Wy are specified from the image of the above, the arithmetic unit 14 receives the position coordinates and the like of the specified nozzle hole 2 and the ink droplet 5 and will be described later. It is possible to calculate the ejection characteristics of the volume, the ejection speed, and the ejection direction of the ink droplet 5 by the arithmetic expression. When the nozzle surface 3 has been subjected to the water-repellent treatment, it is not preferable to measure the position of the nozzle hole 2 by directly contacting the surface, and it is difficult to perform high-precision measurement with a non-contact laser displacement meter. ± 10
Although the limit is about μm, it takes time to actually measure each set of the printer head 1, but in this embodiment,
Since the nozzle hole 2 can also be imaged in the setting state in which the ink droplet 5 is imaged, the position coordinates can be specified in advance or simultaneously with the imaging of the ink droplet 5 and used for the calculation. The error in the position measurement is ± 1 μm
If so, the measurement error of the injection speed is ± 6.7 mm / sec.

However, the CCD cameras 12x and 12y are
Since the nozzle surface 3 is imaged at an elevation angle of 10 degrees, as shown in FIG.
Since the displacement in the axial direction appears as the displacement in the Z-axis direction in the image Wy captured by the CCD camera 12y, the positional relationship between the nozzle hole 2 and the ink droplet 5 needs to be corrected as described later. . The CCD camera 12x, 1
By setting 2y obliquely, the ejection distance L of the ink droplet 5 in the Z-axis direction is reduced and measured at the ejection distance L2 as shown in FIG. 11A. Illumination lamps 11x and 11y and CCD cameras 12x and 12y so as to fall within the range of measurement accuracy to be measured.
Is set to 10 degrees. It goes without saying that the injection distance L2 in the Z-axis direction may be corrected to obtain an accurate injection distance L for more accurate measurement.

Then, in the measurement of the injection characteristics in step P6 shown in FIG.
When Δx and Δy are obtained from the captured images Wx and Wy for each of 2x and 12y, a portion captured as an ink droplet 5 indicated by a broken line in FIG. 11B is measured as an ink droplet 5 indicated by a solid line. Since the injection distance L3 is required,
Lx2 and Ly2 used for calculating the injection distance L2 are Δ
It is necessary to correct using y and Δx.

Therefore, the ejection speed S of the ink droplet 5 is:
The ink droplet 5 and the nozzle hole 2 specified from the captured images Wx and Wy of the CCD cameras 12x and 12y shown in FIG.
Lx3, Ly3 and Δx, Δy obtained from the position coordinates of
Is used to calculate and combine Lx2 and Ly2 to calculate the injection distance L2, and then calculate as follows using the injection distance L2 and the delay time T from the injection.

(Equation 4)

The ejection direction θ of the ink droplet 5 shown in FIG. 12 is calculated as follows using the value used in the previous calculation.

(Equation 5)

At this time, the ink droplets 5
When the nozzles 2 are vertically ejected from the nozzle holes 2, the image W taken by each of the CCD cameras 12x and 12y becomes the image shown in FIG. 13, and the ink droplets 5 are ejected by substituting zero into Δx and Δy in each equation. The speed S is calculated (the injection direction θ is 0 degree).

Next, an embodiment of a method for determining an object to be imaged (ink droplet) according to the present invention will be described with reference to FIGS. The determination method of the present embodiment is applicable to the first and second examples of the droplet ejection velocity measuring system described above. 14 to 16 show an image W captured by the droplet ejection characteristic measuring system according to the present embodiment. First, as described above, the image processing device 13 extracts (specifies) the ink droplet 5 from the image W captured by the CCD cameras 12x and 12y and specifies the center position coordinate, and then, as shown in FIG. The same ink is used when the illumination lamps 11x and 11y are strobe-emitted from the timing at the time of the delay reference taken earlier based on the position coordinates and the device specifications to the timing at the time of the delay increase by, for example, 14 μsec. A window S is set so that the droplet 5 can be reliably caught, and image processing is performed in the window S. As a result, similarly to the ink droplet 5 at the timing of the delay reference shown by the broken line in FIG.
The image of the ink droplet 5 at the timing when the delay is increased as indicated by the solid line in FIG. 15 is extracted as a measurement target, and the center position coordinate is specified. As the delay increase time, one ink drop 5
Is set to a time at which the image can be reliably captured as different position coordinates at which the center of has moved. In the first and second examples of the injection velocity measuring system, the window S for performing image processing only on the image captured at the timing of the delay increase is set in the captured video W, but the window S is captured at the timing of the delay reference. Image processing may be performed on the video in the same window S. (Hereinafter, margin)

Next, the arithmetic unit 14 is the image processing unit 1
The difference (positional relationship) P is calculated by using the position coordinates of the ink droplet 5 captured and captured at the timing of the delay reference time and the delay increase received from the delay No. 3 as shown in FIG. Is an ink droplet 5 ejected from the nozzle hole 2
When the moving amount is within the reference range of the moving amount corresponding to the ejection speed, the image processing apparatus 13 determines that the measurement target is the ink droplet 5 ejected from the nozzle hole 2 and determines the ink droplet 5 described above.
Measurement of the injection characteristics is continued, as shown in FIG.
When the difference P is out of the reference range of the moving amount corresponding to the ejection speed of the ink droplet 5, the measurement object extracted by the image processing device 13 is extracted by a CCD camera 12 other than the ink droplet 5, for example.
It is determined that the dust 6 or the ink 7 has adhered to the lenses x and 12y, an error is reported, and the measurement of the next ink droplet 5 is started. The reference range (reference value) of this movement amount is the ink droplet 5
In other cases, the position coordinates almost coincide with each other. Even if the measurement system moves due to vibration or the like, the movement amount is small, so the upper reference value may be set. It is sufficient to set only the reference value on the side, and to determine that the ink droplet is larger than the ink droplet 5 if it exceeds the ink droplet 5 if it exceeds the reference value. When the upper limit value of the reference range of the movement amount is set, even if there is an object that happens to be imaged across the imaging range, it may be determined that the object is other than the ejected ink droplet 5. it can.

As described above, in the present embodiment, the same timing as the timing of the delay increase after the delay reference time has elapsed from the timing of the delay reference time when the ink droplet 5 has been imaged when a predetermined time has elapsed after the start of the ejection operation. Measurement is performed by imaging the ink droplet 5 and determining whether or not the difference P between the position coordinates of the ink droplet 5 specified by the image processing of both captured images W is within a reference range corresponding to the ejection speed of the ink full 5. Since it is determined whether or not the object is the ink droplet 5 ejected from the nozzle hole 2, only the image of the ink droplet 5 moving at the ejection speed can be set as the measurement object. Therefore, even if the image is identified as the ink droplet 5, the dust 6 and the ink 7 that are taken as if they happen to move due to the vibration of the measurement system or the like do not become a measurement target. 5 of the measurement accuracy and reliability of the injection characteristics can be improved. Further, the determination as to whether or not the ink droplet 5 is made can be performed in the same manner during the measurement of the ejection characteristics of the ink droplet 5, so that the processing amount and processing time increase, and the ejection of the ink droplet 5 is increased. There is no hindrance to automatic measurement of characteristics.

Further, the determination as to whether or not the ink droplet 5 is made can be made such that the same ejected ink droplet 5 can be imaged at the delay reference time and the delay increase time, and the difference P in the position coordinates can be calculated. In addition, since the window S of the image processing and the delay increase time from the delay reference time are set, it can be determined that the ejected ink droplet 5 is the measurement target. In addition, by setting these windows S and the delay increasing time to necessary and sufficient conditions, the ink droplet 5 can be easily and quickly measured during the measurement of the ejection characteristics of the ink droplet 5.
Only the measurement target can be reliably determined.

Next, an embodiment of a method for specifying a droplet of an ejection characteristic target from a plurality of imaging targets (ink droplets) according to the present invention will be described with reference to FIGS. 17 (a) to 17 (c). The method for specifying a droplet in the present embodiment is applicable to the first and second examples of the droplet ejection velocity measuring system described above, and particularly when the velocity of the ink droplet is in the range of 4 to 6 m / sec. This method is suitable for measuring the velocity of the ink droplet. FIGS. 17A to 17C show captured images W in the droplet ejection characteristic measurement system according to the present embodiment.

First, as shown in FIG. 17A, the image processing device 13 serving as the droplet specifying means
Any one of the plurality of ink droplets 5 in the captured image W based on x and 12y is extracted (identified) to specify the center position coordinate (this ink droplet is indicated by reference numeral 5A). And
As shown in FIG. 17 (b), the illumination lamps 11x and 11y are shifted from the timing at the delay reference time previously imaged based on the position coordinates and the device specifications to the timing at the time of the delay increase by, for example, 14 μsec. The window S is set so that the same ink droplet 5A can be reliably captured when the strobe light is emitted. By performing image processing in the window S, the image of the ink droplet 5A at the timing of the delay increase is extracted as an imaging target and the center position coordinate is specified, similarly to the ink droplet 5A at the timing of the delay reference. I do. The delay increase time is set to a time during which the image can be reliably captured as different position coordinates at which the center of the ink droplet 5A has moved. In the first and second examples of the injection velocity measuring system, the window S for performing image processing only on the image captured at the timing of the delay increase is set in the captured video W, but the window S is captured at the timing of the delay reference. Image processing may be performed on the video in the same window S.

Next, the image processing device 13 calculates the moving distance L1 of the ink droplet 5A based on the measurement results of the position coordinates of the ink droplet 5A at the time of the delay reference and at the time of the delay increase. Using the calculated value of the moving distance L1 and the shift (phase difference) of the timing of flash emission of the illumination lamps 11x and 11y, an approximate value V1 of the speed of the ink droplet 5A is obtained. Based on the estimated value V1 of the speed, the ink droplet of the ejection characteristic measurement target in the captured image W is specified. Specifically, the ink droplet 5A estimated using the approximate value V1
And the ink droplet 5 measured in FIG.
When the position coordinates of the ink droplet 5A substantially coincide with the position coordinates of the ink droplet 5A,
Are specified as ink droplets whose ejection characteristics are to be measured. Using the position coordinates of the ink droplet specified as the ejection characteristic measurement target (the value measured in FIG. 17A), the accurate speed of the ink droplet 5 can be calculated.

Here, when the speed of the ink droplet is low (for example, 4 m / sec or less), the following measurement is performed to specify the ink droplet of the ejection characteristic measurement for more accurate speed measurement. Is preferred. After measuring the position coordinates when the delay of the ink droplet 5A shown in FIG. 17B is increased, as shown in FIG.
The illumination lamps 11x and 11y are arranged so that the ink droplets before or after one cycle (in the example in the figure, the ink drops one cycle before and indicated by reference numeral 5B) can be captured within the window S of the measurement range. Set the flash emission timing (phase difference) for Then, the position coordinates of the ink droplet 5B are measured.

Next, the image processing apparatus 13 determines the position of the ink droplets 5A and 5B based on the measurement results of the position coordinates of the ink droplets 5A and 5B and the above-described approximate value of the ink droplet speed.
The distance L2 between the ink and the ink droplet 5B is calculated. Using the calculated value of the interval L2 and the difference (phase difference) in the timing of flash emission of the illumination lamps 11x and 11y, an approximate value V2 of the speed of the ink droplet 5 is obtained. Based on the estimated value V2 of the speed, the ink droplet of the ejection characteristic measurement target in the captured image W is specified. Specifically, the position coordinates of the ink droplet 5A estimated using the approximate value V2 and FIG.
When the position coordinates of the ink droplet 5A measured in (a) substantially coincide with each other, the ink droplet 5A is specified as an ink droplet whose ejection characteristic is to be measured. Using the position coordinates of the ink droplet specified as the ejection characteristic measurement target (the value measured in FIG. 17A), the accurate speed of the ink droplet 5 can be calculated.

The determination as to whether or not the ink droplet 5A is to be measured for the ejection characteristics may be performed as follows. That is, after calculating the approximate value V1 of the ink droplet speed in the measurement of FIG. 17A, the approximate value V2 of the ink droplet speed is calculated in the measurement of FIG. 17C. When the difference between the approximate values V1 and V2 of the speeds of the two ink droplets is small, it is determined that the ink droplet 5A is the ink droplet whose ejection characteristic is to be measured, and the ink droplet 5A specified as the ejection characteristic measurement object is determined. Using the position coordinates (the values measured in FIG. 17A), the accurate speed of the ink droplet 5 can be calculated.
On the other hand, when it is determined that the difference between the approximate values V1 and V2 of the ink droplet speed is large and the ink droplet 5A is not the ejection characteristic measurement target, the illumination lamp 11 in FIG.
The speed of the ink droplet is calculated using a value obtained by adding or subtracting the period of the flash emission from the timing shift (phase difference) of the flash emission of x and 11y, and calculating the calculated value with the final ink droplet speed. I do.

In each of the above embodiments, the illumination lamps 11x and 11y and the CCD cameras 12x and 12y
Is applied to the droplet ejection velocity measuring system in which two sets are arranged, respectively, and the one set of the illumination lamp and the CCD camera are rotated to sequentially eject the ink drops 5 ejected from the nozzle hole 2 into two sets. The present invention can also be applied to a system that performs imaging from a direction or a system that performs imaging only from one direction. Also,
Ink droplets 5 with lighting lamp and CCD camera facing each other
It is needless to say that the present invention can be applied not only to a system configured to be capable of performing image processing irrespective of the background color, but also to a system in which an illumination lamp and a CCD camera are arranged in the same direction to capture the ink droplets 5. .

In this embodiment, a case where the present invention is applied to a droplet ejection velocity measuring system will be described. However, the present invention is not limited to ejected droplets, and may be applied to a case where a moving object is specified by image processing. Can be.

[0059]

According to the first to fourth aspects of the present invention, the same droplet ejected is imaged at different timings, and based on each positional relationship identified by the image processing, the measurement target identified as the droplet is obtained. Since it is determined whether or not the object is a jetted droplet, the specified measurement target is a jetted droplet when moving by a fixed amount, and the specified measurement target is a droplet when not moving. It can be determined that the droplet is not an ejected droplet. Therefore, even if the image of the object to be measured is indistinguishable from the characteristics of the droplet in the image processing, it is possible to reliably determine whether or not the droplet is a droplet. Can be used for measurement. As a result, it is possible to prevent the measurement target from being erroneously measured, and it is possible to measure the ejection characteristics of the droplet with high accuracy and high reliability. Further, when image processing is used for measuring the ejection characteristics of droplets, the determination can be made during the measurement, so that the increase in the processing amount or processing time can be suppressed.

In particular, according to the second aspect of the present invention, the object to be imaged is determined based on whether or not the positional relationship between the droplets imaged and specified at different timings is within the range of the movement amount according to the ejection speed. It is determined whether or not the droplet is a droplet, and when the movement amount is within the range, the droplet is a droplet of the ejection characteristic ejected from the nozzle hole, and when the movement amount that does not move at all is out of the range. It can be determined that the droplet is not the target of the ejection characteristic. Therefore, although the relative positional relationship with respect to the nozzle hole and the measurement system has not moved,
Even when the image is taken as if it were moving in the video, it can be reliably determined that the droplet is not the target of the ejection characteristic, and the ejection characteristic of the droplet can be measured with higher accuracy and reliability. This has the effect.

In particular, according to the third aspect of the present invention, the ejected droplets to be imaged at different timings are specified at the moved position, for example, according to the pixels for image processing and the capability of the measurement system. Since the image processing window and the delay increase time from the delay reference time are set, as long as the ejected droplets can be imaged and specified at a position moved by a certain amount, these windows and delay increase time are necessary Since it is sufficient to set sufficient conditions, it is possible to easily and quickly determine whether or not the imaging target is a droplet of the ejection characteristic target by image processing of a part of the captured video.

According to the fifth and sixth aspects of the present invention, even when a plurality of droplets to be imaged are present in a captured image, such as when droplets are ejected by relatively high-frequency driving, the ejection characteristics can be improved. Since the droplet to be measured can be specified, there is an effect that the ejection characteristics of the droplet can be measured with high accuracy and high reliability.

According to the seventh and eighth aspects of the present invention, even when a relatively large number of droplets to be imaged are present in a captured image, such as when droplets are ejected by higher-frequency driving, ejection is performed. Since the droplet whose characteristics are to be measured can be specified, it is possible to measure the ejection characteristics of the droplet with high accuracy and high reliability.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a schematic overall configuration of a first example of an injection velocity measuring system to which an injection characteristic measuring method of the present invention can be applied.

FIG. 2 is a side view illustrating imaging of the droplet.

FIG. 3 is a conceptual diagram illustrating a positional relationship between the captured images.

FIG. 4 is a conceptual diagram illustrating adjustment before measurement is started in the injection speed measurement system.

FIG. 5 is a flowchart illustrating the measurement.

FIG. 6 is a conceptual diagram illustrating a calculation process in the measurement.

FIG. 7 is a conceptual diagram showing a captured image different from FIG. 6;

FIG. 8 is a side view showing a main configuration of a second example of an injection velocity measuring system to which the injection characteristic measuring method of the present invention can be applied.

FIG. 9 is a side view illustrating imaging of the droplet.

FIG. 10 is a conceptual diagram illustrating characteristics of the droplet by imaging.

FIGS. 11A and 11B are conceptual diagrams illustrating characteristics of arithmetic processing by imaging the same droplet.

FIG. 12 is a conceptual diagram illustrating the calculation processing.

FIG. 13 is a conceptual diagram showing a captured image different from that in FIG. 12;

FIG. 14 is a conceptual diagram showing a captured image in one embodiment of a method for determining a jet droplet according to the present invention.

FIG. 15 is a conceptual diagram showing the captured image following FIG. 14;

FIG. 16 is a conceptual diagram showing a captured image different from FIGS. 14 and 15;

FIGS. 17A to 17C are conceptual diagrams showing captured images in an injection velocity measuring system according to a third embodiment of the present invention.

FIG. 18 is a perspective view illustrating a printer head that ejects droplets.

FIG. 19 is a diagram for describing a problem of the droplet ejection velocity measuring system, and is a conceptual diagram showing an image captured by the system.

FIG. 20 is a conceptual diagram showing a captured image after processing different from that in FIG. 19;

FIG. 21 is a conceptual diagram showing a captured image after processing different from that in FIG. 20;

FIG. 22 is a conceptual diagram showing a captured image when the driving frequency of a nozzle head and the speed of a droplet change.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Printer head 2 Nozzle hole 3 Nozzle surface 5 Ink droplet (droplet) 11x, 11y Illumination lamp (illumination unit) 12x, 12y CCD camera (imaging unit) 13 Image processing device (position identification unit, determination unit, droplet identification unit) 14) Computing device (computing means)

Claims (8)

[Claims] 1. A method for measuring droplet ejection characteristics by imaging droplets ejected from a nozzle hole and measuring the ejection characteristics of the droplets, the method comprising the steps of: Image processing is performed on an image captured when a delay has increased by a fixed time after the delay reference time, and the position of the delay time of the imaging target and the position of the delay increase are specified. Based on the relative position,
A method for measuring the ejection characteristics of a droplet, comprising: determining whether the imaging target is a droplet whose ejection characteristics are to be measured. 2. The method according to claim 1, wherein the position of the object to be imaged at the time of the delay reference and at the time of the delay increase is out of the range of the movement amount according to the ejection speed. A method for measuring the ejection characteristics of a droplet, comprising determining that an object is not a droplet whose ejection characteristics are to be measured. 3. The method according to claim 1 or 2, wherein the window for image processing and the delay increase time after a lapse of a predetermined time from the delay reference time are determined by the delay reference time of the ejected droplet. A method for measuring droplet ejection characteristics, wherein a position at the time of delay increase is set so as to be specified. 4. A droplet ejection characteristic measuring system for imaging a droplet ejected from a nozzle hole and measuring the ejection characteristic of the droplet, wherein the droplet ejected from the nozzle hole is illuminated by illumination means. Imaging means for imaging the liquid droplets; and delaying the imaging target by processing an image captured at a delay reference time after a lapse of a certain time from the start of the ejection operation and at a delay increase after a certain time from the delay reference time. Position specifying means for specifying a position at the reference time and at the time of the delay increase, and the imaging object is ejected of the ejection characteristic measurement object based on the relative positional relationship at the delay reference time and the delay increase of the imaging object. A droplet ejection characteristic measuring system, comprising: a determination unit for determining whether the droplet is a droplet. 5. A method for measuring the ejection characteristics of a droplet by imaging a droplet ejected from a nozzle hole and measuring the ejection characteristics of the droplet, the method comprising the steps of: Image processing is performed on an image captured when a delay has increased by a fixed time after the delay reference time, and the position of the imaging target at the delay reference time and the delay increase is specified, and the imaging target object at the delay reference time and the delay increase. Wherein the velocity of the object to be imaged is estimated based on the position in the step (a), and the droplet of the object to be measured in the captured image is specified based on the estimated value of the velocity. 6. A droplet ejection characteristic measuring system for imaging a droplet ejected from a nozzle hole and measuring the ejection characteristic of the droplet, wherein the droplet ejected from the nozzle hole is illuminated by illumination means. Imaging means for imaging the liquid droplets; and delaying the imaging target by processing an image captured at a delay reference time after a lapse of a certain time from the start of the ejection operation and at a delay increase after a certain time from the delay reference time. Position specifying means for specifying a position at the time of reference and at the time of increase in delay; calculating means for roughly estimating the speed of the object to be imaged based on the position of the object to be imaged at the time of reference to the delay and at the time of increase in delay; A droplet specifying means for specifying a droplet to be measured for an ejection characteristic in a captured image based on an approximate value; and a droplet ejection characteristic measuring system. 7. A method for measuring the ejection characteristic of a droplet by imaging a droplet ejected from a nozzle hole and measuring an ejection characteristic of the droplet. Image processing of the captured image to specify the positions of two consecutive imaging targets in the imaging liquid image, and perform the imaging based on the positions of the two imaging targets at the delay reference time and the droplet ejection cycle. A droplet ejection characteristic measuring method comprising: estimating a velocity of an object; and identifying a droplet of an ejection characteristic measurement target in a captured image based on the estimated value of the velocity. 8. A droplet ejection characteristic measuring system for imaging a droplet ejected from a nozzle hole and measuring the ejection characteristic of the droplet, wherein the droplet ejected from the nozzle hole is illuminated by illumination means. Imaging means for imaging the liquid droplets, and a position for processing a video image taken at a delay reference after a lapse of a predetermined time from the start of the ejection operation to specify the positions of two consecutive imaging objects in the imaging liquid image Specifying means, calculating means for estimating the speed of the imaging object based on the position of the two imaging objects at the delay reference time and the ejection period of the droplet, and imaging video based on the estimated value of the speed A droplet specifying means for specifying a droplet to be measured for the inside of the droplet ejection characteristic.