JPH11105307A - System for measuring ejection characteristic of liquid drop - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately measure an ejection characteristic by a method wherein positions from a reference point in a picture image of liquid drops imaged from two directions after a predetermined time period has elapsed from the ejection from a nozzle are determined by each of the directions, then the ejection characteristics of the liquid drops are calculated based on the positional relationship of the nozzle and reference position in the picture image. SOLUTION: When an ejection characteristic of a printer head 1 is measured, the printer head 1 is firstly set to a head grasping member 4. A distance from a center to a nozzle face in an imaged screen of each of CCD cameras 12x, 12y is measured and the distance is inputted to an arithmetic logic unit 14. Next, the printer head 1 is driven to start the ejection of ink drops. When the ejection becomes stable, illuminating lamps 11x, 11y are driven such that stroboscopic illuminating is executed at a timing when the ink drop reaches the center in the imaged screen by delaying a predetermined time from the ejection. It is confirmed that the ink drop 5 is a target for measuring, then a volume, an ejection speed and an ejection direction of the ink drop 5 are calculated so that the ejection characteristic is measured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a droplet ejection characteristic measuring system for measuring the velocity of a droplet ejected from a nozzle hole, and relates to an ejection characteristic such as a droplet speed (moving speed and moving direction). The present invention relates to a device capable of measuring with high accuracy with a simple configuration.

[0002]

2. Description of the Related Art Conventionally, an ink jet printer which forms an image by flying ink droplets (droplets) has been known. In this ink jet printer, ink droplets ejected from nozzle holes of a printer head land on paper. An image is formed by causing the image quality to be evaluated. The evaluation items of the image quality include dot density, dot position accuracy, density unevenness, and sharpness.

[0003] One of the quality items, dot density,
At present, about 300 DPI is generally used. However, in order to increase the resolution and form a high-quality image, the dot pitch and the dot diameter are set small and the dot density is set to 400.
DPI, 600 DPI, etc. are performed. The dot diameter is proportional to the volume of the ink droplet ejected from the printer head, and the dot diameter increases as the ejection speed of the ink droplet increases.

Further, as shown in FIG. 16, the dot position accuracy is such that the printer head 1 moves in the main scanning direction with respect to the paper surface and moves the paper surface in the sub-scanning direction to form an image. Can be divided into two components (Ax, Ay) for evaluation. This dot position accuracy is
Due to both components of the mechanical accuracy of the printer body (not shown) and the printer head 1 and the accuracy of the ejection speed of the ink droplet 5 ejected from the nozzle hole 2 of the printer head 1, the mechanical accuracy has a relatively small error. On the other hand, the accuracy of the ejection speed of the ink droplet 5 has a great effect. The accuracy of the ejection speed of the ink droplet 5 is large due to the contribution ratio of the ink dropletization characteristics. Among the ejection direction and the ejection speed of the ink droplet 5, the error due to the ejection speed is almost the same as that of the nozzle except for disturbance such as dust. It depends on the processing accuracy and quality of the hole 2 and appears only in the main scanning direction (Ay). The permissible value of the dot position deviation in the dot position accuracy is usually about ４ to ド ッ ト of the pitch between dots, so that this permissible value is a very strict value. For example, when the dot position accuracy is 1/3 of the dot pitch under the condition that the dot density is 300 DPI, the driving frequency for ejecting the ink droplet 5 is 5 KHz, and the distance from the lower surface of the printer head 1 to the paper surface is 1 mm, the ejection speed is The allowable width is 50 mm / sec.

As described above, in order to obtain a high-resolution image, it is necessary to measure and control the accuracy of the volume and ejection speed (direction / speed) of the ejected ink droplet 5 with high accuracy.

[0006]

However, in such conventional evaluation of image quality, printing is performed by assembling the printer head 1 with the printer body and then ejecting ink droplets 5 onto the paper surface. By measuring the dot density and dot position accuracy of the ink droplet 5, the speed and direction of the ink droplet 5 ejected in a set volume have been indirectly evaluated.

However, in this method, errors due to paper surface properties, bleeding, paper skew, and the like when printing on the paper surface are greatly affected. It is not possible to perform performance evaluation by itself. Further, in this method, since the volume, the ejection direction, and the ejection speed of the ink droplet 5 cannot be measured separately, the mechanical accuracy of the printer body and the ink droplet 5 cannot be measured.
There was no other choice but to adjust the accuracy of the volume and the injection speed by trial and error.

As a method for solving this problem, there is provided an apparatus for directly measuring the ink droplets 5 flying in the air instead of evaluating the performance of the printer head 1 based on an image printed by jetting the ink droplets 5 onto the paper surface. It can be used. As a method for measuring the speed of a droplet (ink droplet) flying in the air, a laser beam is applied to the flying ink droplet 5 and the Doppler effect of the laser beam is used to measure the speed of the ink droplet 5. So-called measuring the speed of movement,
There is a laser Doppler system, and it is conceivable to use a current meter that employs this system for performance evaluation of the printer head 1 alone.

However, the current meter using the laser Doppler is expensive, and can measure only the speed of the ejected ink droplet 5 and cannot measure the ejection direction. Further, even if the ejection speed of the ink droplet 5 is measured by a laser Doppler method, the allowable width of the ejection speed required for forming an image with a dot density of 300 DPI as described above is 50 mm / sec. On the other hand, the measurement accuracy is about ± 100 mm / sec, and cannot be measured with high accuracy.

The present invention has been made in view of the above problems, and has as its object to directly measure the ejection characteristics such as the speed (direction and speed) of a droplet ejected from a nozzle hole and flying in the air. Measurement system that enables performance evaluation of a single nozzle head (for example, a printer head of an ink jet printer) having a nozzle hole formed therein, thereby enabling easy adjustment work. Is to provide a system. Another object of the present invention is to provide a low-cost and general-purpose droplet ejection characteristic measuring system by easily measuring the ejection characteristics such as the flying speed of the droplet with a simple configuration.

[0011]

According to one aspect of the present invention, there is provided a droplet ejection characteristic measuring system for measuring an ejection characteristic of a droplet ejected from a nozzle hole. Imaging means for illuminating the droplet ejected from the hole by the illuminating means to image the droplet, and a position for specifying the position of the droplet from a reference position in a video image taken after a lapse of a predetermined time from the ejection An imaging unit comprising: an identification unit; and an arithmetic unit configured to calculate, based on the positional relationship between the position of the nozzle hole and the reference position in the image, the ejection characteristic of a droplet whose position has been identified from the reference position. Is configured to image droplets ejected from the nozzle holes from two directions. In the droplet ejection characteristic measuring system according to the first aspect, when a predetermined time has elapsed from the ejection of the nozzle hole, the position of the droplet imaged from two directions from the reference position in the image is specified for each direction, The ejection characteristics of the droplet are calculated based on the positional relationship between the nozzle hole and the reference position in the image. Therefore, the ejection characteristics of the droplet ejected from the nozzle hole can be directly measured with high accuracy without being affected by other factors.

According to a second aspect of the present invention, in the liquid droplet ejection characteristic measuring system according to the first aspect, the arithmetic means is configured to detect the position of the droplet specified from the reference position in the image for each imaging direction by the position specifying means. The apparatus is characterized in that the speed and the ejection direction of the droplet are calculated using the position. In the droplet ejection characteristic measuring system according to the second aspect,
The position of the droplet imaged in two directions from the reference position in the image when a certain time has elapsed from the ejection of the nozzle hole is specified for each direction, and based on the positional relationship between the nozzle hole and the reference position in the image. The speed and ejection direction of the droplet are calculated. Therefore, the direction and speed of the droplet ejected from the nozzle hole can be directly measured with high accuracy without being affected by other factors.

According to a third aspect of the present invention, in the droplet ejection characteristic measuring system of the second aspect, the arithmetic means calculates the volume of the droplet from the image of the droplet imaged by the imaging means. It is characterized by having comprised in.
In the droplet ejection characteristic measuring system according to the third aspect, the volume of the droplet is calculated from the image of the droplet in addition to the speed and the ejection direction of the droplet. Therefore, the ejection characteristics of the droplet can be measured with high accuracy.

According to a fourth aspect of the present invention, in the droplet ejection characteristic measuring system according to any one of the first to third aspects, the image pickup means is configured to simultaneously image the nozzle hole and the droplet from the droplet ejection direction side. The imaging direction is set diagonally with respect to the position, and the position specifying means is configured to specify the position in the image of the droplet ejected from the nozzle hole and imaged and to specify the position in the image of the nozzle hole. Comprising:
The ejection characteristic of the droplet is calculated based on the positional relationship between the nozzle hole and the droplet in the specified image. In the droplet ejection characteristic measuring system according to the fourth aspect, the nozzle hole and the droplet are simultaneously imaged by being imaged obliquely with respect to the ejection direction, and the positions of the nozzle hole and the droplet in the specified image are determined. The ejection characteristics such as the speed (speed and ejection direction) of the droplet are calculated based on the relationship. Therefore, it is possible to omit positioning or measuring the position of the nozzle hole with respect to the reference position in the video with high accuracy.

According to a fifth aspect of the present invention, in the droplet ejection characteristic measuring system according to any one of the first to fourth aspects, the nozzle hole is located between the image pickup means and the illumination means, and the image pickup means is connected to the nozzle hole. The liquid droplets ejected from the liquid crystal are directly taken in, and the liquid droplets are configured to capture an image of shielding the illumination light. In the droplet ejection characteristic measuring system according to the fifth aspect, the droplet ejected from the nozzle hole flies between the imaging means and the illumination means, and the imaging means emits light from the illumination means partially shielded by the droplet. The illumination light is taken in and an image of the droplet is captured. Therefore, the droplet can be imaged regardless of its color.

According to a sixth aspect of the present invention, in the droplet ejection characteristic measuring system of the fourth aspect, the periphery of the nozzle hole is a reflecting surface for reflecting light, and the nozzle is located between the imaging means and the illumination means. The imaging unit and the illumination unit are set obliquely so that the hole is located and the included angle between the imaging direction and the reflection surface in the illumination direction is the same, and the imaging unit is reflected by the reflection surface. The liquid crystal display device is characterized in that reflected light for illuminating a droplet ejected from the nozzle hole is taken in, and an image in which the droplet blocks the reflected light is captured. In the droplet ejection characteristic measuring system according to the sixth aspect, the droplet ejected from the nozzle hole flies between the imaging means and the illuminating means, and the imaging means is reflected by the reflection surface around the nozzle hole and reflected by the droplet. The reflected light (illumination light) from the illumination means, part of which is shielded, is taken in, and an image of the droplet is captured. Therefore, the nozzle hole and the droplet can be imaged simultaneously and regardless of their colors.

According to a seventh aspect of the present invention, in the droplet ejection characteristic measuring system according to the first aspect, based on the position of the droplet from a reference position in an image captured from one of the two directions, the other is used. In which the position of a droplet from a reference position in an image picked up from the direction is predicted.
In the droplet ejection characteristic measuring system according to the seventh aspect, based on a position of a droplet from a reference position in an image captured in one of the two directions, a reference in an image captured in the other direction is used. By estimating the position of the droplet from the position, it is possible to easily and quickly adjust the imaging conditions such as focusing of the imaging means for imaging from the other direction.

According to an eighth aspect of the present invention, in the droplet ejection characteristic measuring system according to the seventh aspect, the imaging range from the other direction is narrowed based on a prediction result of the position of the droplet. Is what you do. In the droplet ejection characteristic measuring system according to the eighth aspect, based on the prediction result of the position of the droplet, the imaging range for imaging from the other direction is narrowed, so that dust other than the droplet to be measured is reduced. Images such as dirt can be excluded from the imaging range, and the time for capturing data of the captured images and the time for image processing such as pattern matching can be shortened.

According to a ninth aspect of the present invention, in the droplet ejection characteristic measuring system of the eighth aspect, the position of the imaging range imaged from the other direction is adjustable. In the droplet ejection characteristic measuring system according to the ninth aspect, the speed of the droplet changes from the end of the imaging in the one direction to the start of the imaging in the other direction to reduce the speed. When the image of the droplet is out of the imaging range, the position of the imaging range to be imaged from the other direction may be adjusted so that the image of the droplet is included in the imaging range. it can.

According to a tenth aspect of the present invention, there is provided the droplet ejection characteristic measuring system according to the eighth aspect, wherein the illumination means intermittently illuminates and the imaging means performs strobe imaging based on the illumination timing. It is characterized in that the illumination timing of the illumination means at the time of imaging from another direction can be adjusted. In the droplet ejection characteristic measuring system according to the tenth aspect, the speed of the droplet changes from the end of the imaging in the one direction to the start of the imaging in the other direction to reduce the speed. When the image of the droplet is out of the imaging range, by adjusting the illumination timing of the illumination unit when imaging from the other direction, the image of the droplet is included in the imaging range. can do.

According to an eleventh aspect of the present invention, in the droplet ejection characteristic measuring system of the first to tenth aspects, the imaging means is configured to image the droplet ejected from the nozzle hole from two orthogonal directions. It is characterized by the following.
In the droplet ejection characteristic measuring system according to the eleventh aspect, the droplet is imaged from two orthogonal directions. Therefore, it is possible to accurately calculate even a liquid droplet ejected obliquely from the nozzle hole.

According to a twelfth aspect of the present invention, in the droplet ejection characteristic measuring system according to any of the first to eleventh aspects, two sets of the image pickup means are set to simultaneously image the droplets ejected from the nozzle holes from two directions. It is characterized by having such a configuration. In the droplet ejection characteristic measuring system according to the twelfth aspect, the droplets and the nozzle holes are imaged by two types of imaging means. Therefore, the same droplet can be imaged simultaneously from two directions.

According to a thirteenth aspect of the present invention, in the droplet ejection characteristic measuring system according to any one of the first to eleventh aspects, the imaging means is rotated so that the droplets ejected from the nozzle holes are sequentially reduced by two.
It is characterized in that imaging is performed from a direction. In the droplet ejection characteristic measuring system according to the thirteenth aspect, the droplets and the nozzle holes are sequentially imaged from two directions by the rotating imaging means. Therefore, a droplet can be imaged by effectively using one set of imaging means and illumination means.

[0024]

Embodiments of the present invention will be described below with reference to the drawings. FIGS. 1 to 7 are diagrams showing a first embodiment of a droplet ejection characteristic measuring system according to the present invention, and this embodiment is the invention described in claims 1, 2, 3, 5, 11, and 12. Corresponding to First, the overall configuration will be described. (Hereinafter, margin)

In FIGS. 1 and 2, a system for measuring the ejection characteristics of a liquid droplet is used to form an ink droplet 5 when an ink jet printer as an image forming apparatus forms an image.
Of the printer head 1 as a nozzle head that ejects the nozzles from the nozzle holes 2.
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. 12
And 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 droplets 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 orthogonal to the longitudinal direction (see FIG. 16).

In the ink jet printer, the printer head 1 is attached to 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.
Therefore, as shown in FIG. 3, the image screen W captured by the CCD cameras 12x and 12y is positioned such that the position of the paper surface separated from the nozzle surface 3 of the printer head 1 by the distance h is 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, and the CCD cameras 12x and 12y are provided with ink droplets ejected from the nozzle hole 2. 5 are arranged so as to directly take in the light from the illumination lamps 11x and 11y. 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 processing apparatus 13 has a drive 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 imaging screen W shown in FIG. ), The illumination lamps 11x and 11y emit strobe light. Then, the images of the CCD cameras 12x and 12y captured at the above timing are image-processed, and the position coordinates ((Δx,
Δy), Δz) and the diameter D of the ink droplet 5
Is to be specified. That is, the image processing device 13 constitutes 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 5. The illumination lamps 11x and 11y emit strobe light at a specific frequency such as 1 kHz, for example, and the CCD cameras 12x and 12y capture images at the timing when the ink droplets 5 reach the center of the imaging screen W shown in FIG. A video may be used. The driving frequency is 1 kHz or 12 k
The frequency may be set to another frequency such as Hz.

The arithmetic unit 14 as arithmetic means for calculating the ejection characteristic of the ink droplet 5 whose position has been specified from the reference position based on the positional relationship between the position of the nozzle hole 2 and the reference position in the image, The position coordinates ((Δx, Δx) of the ink droplet 5 from the image processing device 13 with respect to the center C in the video screen.
y), Δz) and the diameter D of the ink droplet 5, and calculates the ejection characteristics of the volume, ejection speed, and ejection direction of the ink droplet 5 by an arithmetic expression described later. By attaching a 4 × lens to a lens having a pixel length of about 10 μm at a normal imaging magnification as 12y and making a pixel length, which is a measurement resolution, about 3 μm, the measurement accuracy of the injection speed is ± 20 mm / sec. It is set to be. 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. The distance h is measured by lowering the magnification so that the nozzle surface 3 of the printer head 1 enters the image screen W captured by the CCD cameras 12x and 12y. Alternatively, the scale may be brought into contact with the nozzle surface 3 to measure the distance h to the center C in the imaging screen W,
Similarly, the measurement may be performed by a non-contact type 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 C in the image pickup screen W shown in FIG. CCD camera 12x, 1
There is a possibility that the image may deviate from the imaging screen W of 2y, or an erroneous measurement may occur due to the image of the ink droplet 5 that is not a measurement target. For this reason, before observing the image screen W before starting the measurement, the timing (delay time from the ejection) of the strobe light emission of the illumination lamps 11x and 11y is changed, and the change time of the timing and the ink droplet to be imaged are changed. 5
The erroneous measurement is prevented by temporarily calculating the velocity of the ink droplet 5 from the displacement amount of the position. Also, it is possible to prevent dust that does not change the imaging position from being erroneously identified as the ink droplet 5 even when the timing at which the illumination lamps 11x and 11y emit strobe light is changed.

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 cameras 12x and 12y are set such that the distance h from the nozzle surface 3 to the center of the imaging screen W is approximately 1 mm when the printer head 1 is mounted on the head holding member 4. 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 imaging screen 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 imaging screen W shown in FIG.
By driving x and 11y, it is confirmed whether the ink droplet 5 is a measurement target (whether ejection of the ink droplet 5 and 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 imaging screens Wx and W specified by the image processing device 13 performing image processing from the image processing device 13.
position coordinates ((Δx, Δy), Δ
z) is calculated. Note that the measurement accuracy at this time depends on the measurement accuracy of the device, and is about ± 3 μm, ± 20 μm.
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 imaging screen W of the CCD camera 12x or 12y shown in FIG.

[Number 1] V = πD ^3/6

The ejection speed S of the ink droplet 5 is determined by the imaging screens Wx and Wx of the CCD cameras 12x and 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)

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

(Equation 3)

At this time, the ink droplets 5
When the nozzles 2 are vertically ejected from the nozzle holes 2, the imaging screens Wx and Wy of the CCD cameras 12x and 12y become images shown in FIG. 15 injection speed S is calculated (the injection direction θ is 0 degree). Note that the ejection direction θ indicates the included angle that forms the vertical direction with respect to the nozzle surface 3 of the printer head 1, but it goes without saying that the included angle that forms the X axis or the Y axis may be calculated.

Therefore, the volume V of the ink droplet 5 and the ejection direction θ 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.

As described above, in the present embodiment, the ink droplets 5 ejected from the nozzle holes 2 of the printer head 1 are imaged from two directions at the timing when they reach the position on the paper surface, and image processing is performed. By specifying the position coordinates from the center C in the imaging screens Wx and Wy in each direction together with D, the volume V is calculated from the diameter D of the ink droplet 5 using the image processing result obtained by imaging from each direction. In addition to the calculation, the ejection speed S and the ejection direction θ can be calculated from the positional relationship between the ink droplets 5, the centers C of the imaging screens Wx and Wy, and the nozzle holes 2, and the ejection characteristics of the printer head can be calculated for each element. Can be measured with high accuracy. At this time, since the ink droplet 5 is imaged simultaneously from two orthogonal directions of the X axis and the Y axis corresponding to the main and sub scanning directions,
Injection characteristics can be calculated easily and quickly without being affected by fluctuations for each injection.

Also, the illumination lamp 1 that blocks the ink droplets 5
Illumination light from 1x, 11y is taken in and the ink droplet 5
, The ink droplet 5 is not indistinguishable from the surrounding color, and the image can be picked up regardless of the color of the ink. Therefore, a system for checking the ejection characteristics of the printer head 1 can be constructed at low cost by using the illumination lamps 11x and 11y, the CCD cameras 12x and 12y, the image processing device 13, and the arithmetic device 14, and the production line for the inkjet printer can be manufactured. It can be used for inspections inside.

FIGS. 8 to 13 are diagrams showing a second embodiment of the droplet ejection characteristic measuring system according to the present invention. This embodiment is the invention according to claims 1 to 6, 11 and 12. Corresponding to Note that the present embodiment is configured substantially in the same manner as the above-described first embodiment, and therefore, the same configurations will be described with the same reference numerals.

In this embodiment, the illumination lamps 11x and 11y and the CCD cameras 12x and 12x
y, an image processing device 13, and an arithmetic device 14, but as shown in FIG.
11y and the CCD cameras 12x and 12y can capture 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 in the imaging screens Wx and Wy. In addition, a narrow angle (elevation angle) of the illumination direction and the imaging direction with respect to the nozzle surface 3 is set to 10 degrees and 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 imaging screen 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 imaging screens 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. Further, when the nozzle surface 3 has been subjected to the water-repellent treatment, it is not preferable to directly contact the surface to measure the position of the nozzle hole 2,
High accuracy measurement is difficult with non-contact type laser displacement meter and ± 1
The limit is about 0 μm, and it takes time to actually measure each set of the printer head 1. However, in the present embodiment, the nozzle hole 2 can 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. If the error in the position measurement is ± 1 μm, the injection speed measurement error 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 on the imaging screen Wy of the CCD camera 12y as the displacement in the X-axis direction as the displacement in the Z-axis direction, 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. Needless to say, in order to measure more accurately, the injection distance L2 in the Z-axis direction may be corrected to obtain an accurate injection distance L.

Then, in the measurement of the injection characteristics in step P6 shown in FIG.
When Δx and Δy are obtained from the imaging screens Wx and Wy for each of 2x and 12y, the part imaged as the ink drop 5 indicated by the broken line in FIG. 11B is measured as the ink drop 5 indicated by the 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 drops 5 and the nozzle holes 2 specified from the imaging screens 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. (Hereinafter, margin)

(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 drops 5 are
When the nozzles 2 are vertically ejected from the nozzle holes 2, the imaging screen W for each of the CCD cameras 12x and 12y becomes an image shown in FIG. 5 is calculated (the injection direction θ is 0 degree).

As described above, in the present embodiment, in addition to the effects of the first embodiment, the nozzle holes 2
And the ink droplet 5 at the same time, and the ejection speed and the ejection direction can be calculated from the position coordinates of the ink droplet 5 with respect to the nozzle hole 2 specified in the imaging screen W. Positioning and measurement of the position 2 with high accuracy can be omitted. Therefore,
The ejection characteristics of the printer head 1 can be measured more easily and easily.

The imaging of the ink droplets in each of the above-described embodiments is based on the position (Y coordinate, Z coordinate) of the ink droplet 5 from the reference position in the image captured from the X direction of the above two directions. Alternatively, the position (Y coordinate, Z coordinate) of the ink liquid 5 from the reference position in the video imaged from the other Y direction may be predicted. In this way, by predicting the position (Y coordinate, Z coordinate) of the ink liquid 5 from the reference position in the image captured in the Y direction, the focus (focusing) of the CCD camera 12y in the Y direction and the Z direction are adjusted. It is possible to easily and quickly adjust the image pickup position, and it is possible to speed up and stabilize the measurement of the ejection characteristics of the ink droplet 5.

Further, based on the position (Y coordinate, Z coordinate) of the ink droplet 5 from the reference position in the image shown in FIG. 14A imaged in the X direction as described above, an image imaged in the Y direction. Position of the ink liquid 5 from the middle reference position (Y coordinate,
When predicting (Z coordinate), Y is calculated based on the prediction result.
It is preferable that the imaging range for imaging from the direction is narrowed as indicated by reference numeral Wy in FIG. A reference symbol Wy ′ in FIG. 14B indicates an imaging range in the Y direction when the process for reducing the imaging range is not performed. When such a process of changing the imaging range is performed, the image 20 such as dust and dirt other than the ink droplet 5 to be measured can be excluded from the imaging range, so that the ejection characteristic measurement of the ink droplet 5 can be performed more stably. It can be carried out. In addition, the time required for capturing data of a captured image and the time for image processing such as pattern matching can be shortened, so that the ejection characteristics of the ink droplets 5 can be measured at a higher speed. Further, even in a case where the speed of the ink droplet 5 is high and the image of the ink droplet is relatively close in the up-down direction, the image pickup range in the Y direction is narrowed so that only the ink droplet 5 to be measured is within the image pickup range. Can be entered, so that it is not necessary to determine which ink droplet is to be measured. (Hereinafter, margin)

In the case where the imaging range is narrowed as described above, when the imaging from the X direction ends, the Y
If the speed of the ink droplets 5 changes until the image pickup from the direction is started, the ink droplets 5 deviate from the narrowed imaging range Wy as shown in FIG. In the illustrated example, it is out of the range of the imaging range Wy. Therefore, FIG.
As shown in FIG. 5B, an imaging range Wy for imaging from the Y direction
Is adjusted so that the image of the ink droplet 5 is included in the imaging range Wy by shifting the position downward as indicated by the reference symbol Wy ". When the imaging range is adjusted in this manner, Since the image of the ink droplets 5 can be reliably included in the imaging range, the ejection characteristics of the ink droplets 5 can be measured more stably. Instead of adjusting the position of the imaging range in which the image was captured, as shown in FIG.
The illumination timing of y, that is, the timing of strobe light emission may be adjusted so as to be within the imaging range Wy from the position of reference numeral 5c in the drawing.

In each of the above embodiments, the illumination lamps 11x and 11y and the CCD cameras 12x and 12x are used.
Although two sets of y are provided, one set of illumination lamps and a CCD camera may be rotated to sequentially image the ink droplets 5 ejected from the nozzle holes 2 from two directions. (Claim 13). With such a configuration, the emission characteristics of the printer head 1 can be similarly measured with high accuracy even with a single set of illumination lamp and CCD camera, and the cost can be further reduced.

[0056]

According to the first to thirteenth aspects of the present invention, a droplet (for example, an ink droplet) ejected from a nozzle hole (for example, a nozzle hole of a printer head) and taken after a certain period of time has been imaged from two directions, is used as a reference. Since the position from the position is specified and the ejection characteristic of the droplet is calculated from the positional relationship of the nozzle hole and the droplet with respect to the reference position, the ejection speed of the droplet ejected from the nozzle hole is determined by other factors. Direct measurement with high accuracy without being affected. Therefore, it is possible to easily measure the ejection characteristics of the droplets ejected from the nozzle holes and to adjust the dot position accuracy with high accuracy. Moreover, since the imaging of the droplets and the calculation of the ejection characteristics thereof can be performed with a simple configuration, for example, a system with low cost and excellent versatility that can be used for inspection during a production line is provided. There is an effect that can be.

In particular, according to the second aspect of the invention, the ejection speed (speed and ejection direction) of the droplet (eg, ink droplet) ejected from the nozzle hole (eg, the nozzle hole of the printer head).
, It is possible to easily perform particularly high-precision adjustment work of the dot position accuracy. In addition, since imaging of a droplet and calculation of its speed are possible with a simple configuration, for example,
There is an effect that the system can be made low in cost and versatile and can be used for inspection in a manufacturing line.

In particular, according to the third aspect of the present invention, since the volume of the droplet is also calculated from the image of the captured droplet, the ejection characteristics of the droplet ejected from the nozzle hole are not affected by other factors. It can measure directly with high accuracy without receiving it.
Therefore, for example, by measuring the ejection characteristics to which the volume of the ink droplet ejected from the printer head of the ink jet printer is added, it is possible to perform a more accurate adjustment operation and the performance evaluation of the printer head. In addition, since the calculation of the volume of the droplet can be performed with a simple configuration, it can be optimally used for the inspection in the production line, and has an effect that the system can be more excellent in low cost and versatility. .

In particular, according to the fourth aspect of the present invention, since the nozzle hole and the droplet can be simultaneously imaged from oblique directions, positioning and measurement of the nozzle hole with respect to the reference position in the image are omitted, and the nozzle hole and the droplet are omitted. The speed of the droplet can be easily calculated from the positional relationship. Therefore, the accuracy of the ejection speed of the droplet ejected from the nozzle hole can be more easily and easily measured, and the cost can be further reduced and the versatility can be further improved. .

In particular, according to the fifth aspect of the present invention, since the image of the droplet ejected from the nozzle hole is captured by the illumination light that blocks the droplet, the droplet can be captured regardless of the background color. Can be. Therefore, there is an effect that versatility can be further improved.

In particular, according to the sixth aspect of the present invention, the reflected light (illumination light) that is reflected by the reflective surface around the nozzle hole and that is ejected from the nozzle hole blocks the droplet and the nozzle hole. Since the image is taken, both the nozzle hole and the droplet can be taken at the same time, regardless of the respective colors.
Therefore, there is an effect that cost can be further reduced and versatility can be further improved.

In particular, according to the seventh aspect of the present invention, it is possible to easily and quickly adjust the imaging conditions such as focusing of the imaging means for imaging from the other direction, so that the measurement of the droplet ejection characteristics can be performed. There is an effect that the speeding up and stabilization can be achieved.

In particular, according to the invention of claim 8, since the image of dust, dirt, etc. other than the droplet to be measured can be excluded from the imaging range, the measurement of the ejection characteristics of the droplet can be further stabilized. Can be. In addition, the time required for capturing data of a captured image and the time for image processing such as pattern matching can be shortened, so that the effect of measuring the ejection characteristics of the droplet can be further increased.

In particular, according to the ninth and tenth aspects of the present invention,
Since it is possible to ensure that the image of the droplet is included in the imaging range, there is an effect that the measurement of the ejection characteristic of the droplet can be further stabilized.

In particular, according to the eleventh aspect of the present invention, since the droplet is imaged from two orthogonal directions, the speed and the ejection direction of the droplet can be determined from the positional relationship of the droplet with respect to the nozzle hole in each direction. It can be easily calculated. Therefore, there is an effect that the calculation means can be easily configured, and the cost can be further reduced.

In particular, according to the twelfth aspect of the present invention, since the droplets and the nozzle holes are imaged by the two types of image pickup means, the measurement can be performed quickly without being affected by the fluctuation at each injection. Therefore, there is an effect that the versatility can be further improved and the accuracy of the measurement result can be improved.

In particular, according to the thirteenth aspect of the present invention, it is not necessary to prepare two sets of similar devices because the image pickup means is rotated to image the liquid droplets and nozzle holes sequentially from two directions. Therefore, there is an effect that the cost can be further reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a schematic overall configuration of a droplet ejection characteristic measuring system according to a first embodiment of the present invention.

FIG. 2 is a side view for explaining imaging of a droplet in the ejection characteristic measurement system.

FIG. 3 is an explanatory diagram illustrating a positional relationship of an imaging screen in the injection characteristic measurement system.

FIG. 4 is an explanatory diagram illustrating adjustment before the start of measurement in the injection characteristic measurement system.

FIG. 5 is a flowchart illustrating measurement in the injection characteristic measurement system.

FIG. 6 is an explanatory diagram for explaining arithmetic processing in the injection characteristic measurement system.

FIG. 7 is an explanatory diagram showing an imaging screen different from FIG. 6;

FIG. 8 is a side view showing a configuration of a main part of a droplet ejection characteristic measuring system according to a second embodiment of the present invention.

FIG. 9 is a side view illustrating imaging of a droplet in the ejection characteristic measurement system.

FIG. 10 is an explanatory diagram for explaining features of the ejection characteristic measurement system based on imaging of droplets.

FIG. 11 is an explanatory diagram for explaining the characteristics of arithmetic processing by imaging a droplet in the ejection characteristic measurement system.

FIG. 12 is an explanatory diagram for explaining arithmetic processing in the injection characteristic measurement system.

FIG. 13 is an explanatory diagram showing an imaging screen different from FIG. 12;

14A and 14B are side views illustrating imaging of a droplet according to a modification.

FIGS. 15A to 15C are side views illustrating imaging of a droplet according to another modification.

FIG. 16 is a perspective view illustrating a printer head that ejects droplets.

[Explanation of symbols]

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

Claims (13)

[Claims] 1. A droplet ejection characteristic measuring system for measuring an ejection characteristic of a droplet ejected from a nozzle hole, wherein the droplet ejected from the nozzle hole is illuminated by illumination means to image the droplet. Imaging means for performing, a position specifying means for specifying a position of a droplet from a reference position in a video image taken after a certain period of time from the ejection, and a positional relationship between the position of the nozzle hole and the reference position in the video image Calculating means for calculating the ejection characteristics of the droplet whose position has been specified from the reference position, based on the image data, so that the imaging unit images the droplet ejected from the nozzle hole from two directions. A liquid droplet ejection characteristic measuring system characterized by comprising: 2. The droplet ejection characteristic measuring system according to claim 1, wherein the calculating means uses a position from a reference position in an image of the droplet specified for each imaging direction by the position specifying means. A droplet ejection characteristic measurement system configured to calculate a droplet speed and an ejection direction. 3. The droplet ejection characteristic measuring system according to claim 2, wherein said arithmetic means is configured to calculate the volume of the droplet from an image of the droplet imaged by the imaging means. Characteristic droplet ejection characteristics measurement system. 4. A droplet ejection characteristic measuring system according to claim 1, wherein said imaging means is capable of simultaneously imaging the nozzle hole and the droplet from the droplet ejection direction side with respect to the ejection direction. Is set obliquely, and the position specifying means is configured to specify the position in the image of the droplet ejected and imaged from the nozzle hole and to specify the position in the image of the nozzle hole, A droplet ejection characteristic measuring system configured to calculate the ejection characteristic of the droplet based on the positional relationship between the nozzle hole and the droplet in the specified image. 5. The droplet ejection characteristic measuring system according to claim 1, wherein said nozzle hole is located between said image pickup means and said illumination means, and said image pickup means is provided with a liquid ejected from said nozzle hole. A droplet ejection characteristic measurement system configured to directly capture light for illuminating a droplet and capture an image in which the droplet blocks illumination light. 6. A droplet ejection characteristic measuring system according to claim 4, wherein a periphery of said nozzle hole is a reflection surface for reflecting light, and said nozzle hole is located between said image pickup means and said illumination means. The imaging unit and the illumination unit are set obliquely so that the included angle between the imaging direction and the reflection surface in the illumination direction is the same, and the imaging unit is reflected by the reflection surface and ejected from the nozzle hole. A liquid droplet ejection characteristic measuring system configured to take in reflected light for illuminating a droplet, and capture an image in which the droplet blocks the reflected light. 7. The droplet ejection characteristic measuring system according to claim 1, wherein an image is taken from the other direction based on the position of the droplet from a reference position in an image taken from one of the two directions. A droplet ejection characteristic measuring system for predicting a position of a droplet from a reference position in an image. 8. The droplet ejection characteristic measuring system according to claim 7, wherein an imaging range for imaging from the other direction is narrowed based on a result of the prediction of the position of the droplet. Injection characteristics measurement system. 9. The droplet ejection characteristic measuring system according to claim 8, wherein the position of the imaging range imaged from the other direction is adjustable. 10. A droplet ejection characteristic measuring system according to claim 8, wherein the illumination means intermittently illuminates, and the imaging means performs stroboscopic imaging based on the illumination timing. Wherein the illumination timing of the illumination means at the time can be adjusted. 11. The droplet ejection characteristic measuring system according to claim 1, wherein said imaging means is configured to image droplets ejected from a nozzle hole from two orthogonal directions. Droplet ejection characteristics measurement system. 12. The droplet ejection characteristic measuring system according to claim 1, wherein two sets of said image pickup means are set so as to simultaneously image droplets ejected from said nozzle hole from two directions. A droplet ejection characteristic measuring system characterized by the following. 13. The droplet ejection characteristic measuring system according to claim 1, wherein said imaging means is rotated to sequentially image droplets ejected from said nozzle hole from two directions. A droplet ejection characteristic measuring system characterized by the following.