JP4032585B2 - Inkjet injection inspection device - Google Patents

Description

BACKGROUND OF THE INVENTION
The present invention relates to an ink jet injection inspection apparatus, and more particularly to an ink jet injection inspection apparatus capable of accurately detecting droplets.
As market demands for inkjet printers, higher resolution, higher printing speed, and lower price are required. For this reason, an increase in the number of channels, an improvement in landing accuracy, a decrease in the amount of droplets, an increase in ejection speed, and a reduction in manufacturing cost are mentioned in the multi-nozzle.
[Prior art]
[0001]
Conventionally, ink ejection inspection of an ink jet printer head has been performed using a medium printed on paper or the like. In the case of this method, there is a problem that the inspection work becomes complicated, and further, since a recording medium is necessary, the cost is generated and the manufacturing cost of the head itself is increased.
[0002]
For this reason, a droplet inspection apparatus that does not use a recording medium has been developed (for example, JP-A-11-227172).
FIG. 5 is a diagram showing a configuration example of a conventional apparatus. In the figure, 1 is a strobe light source, and 2 is a reflecting mirror arranged so as to surround the strobe light source 1. Reference numeral 3 denotes a secondary light source that receives strobe light, and for example, a white scatterer or a diffusion plate is used. The light from the secondary light source 3 enters the droplets A and B, and the transmitted light is imaged on the CCD 6 via the lens 4. A camera moving mechanism 7 moves the CCD.
[0003]
In the apparatus configured as described above, d is the distance between the droplets A and B, and the field of view is represented by 2d. θ is the spread angle of the luminous flux and is expressed as θ = D / L where L is the distance from the secondary light source 3 to the lens 4 and D is the aperture of the lens 4. Further, the incident angle φ of the light beam is represented by φ = d / L. The droplet image is formed on the CCD 6.
[Problems to be solved by the invention]
[0004]
It has become a well-known technique to capture the position and velocity of a droplet with a flash light source such as a strobe. For example, in the invention described in JP-A-5-149769, there is no description of illumination, and in the invention described in JP-A-11-227172, strobe illumination is measured a plurality of times, and there is no description of the illumination method. Further, in the invention described in Japanese Patent Laid-Open No. 11-227172, two point images of droplets are obtained as a result of a plurality of ejections, and an image of the same droplet cannot be obtained.
[0005]
The present invention has been made in view of such problems, and an inkjet ejection inspection apparatus capable of accurately detecting the same droplet by repeatedly measuring the state of the droplet discharged from the ink head. It is intended to provide.
[Means for Solving the Problems]
[0006]
(1) According to the first aspect of the present invention, a droplet to be measured is disposed between a light source and an image of an optical system composed of one or a plurality of lenses for forming an image of the light source. In an inkjet injection inspection apparatus for forming an image of the above on an image pickup device, two light sources having different polarization directions are prepared as the light sources, these light sources are made to emit light at different light emission timings, and the image of the droplets is polarized optical system The image is formed on the image pickup device via the image sensor, and at least two droplet images are obtained in the same frame.
[0007]
With this configuration, speed and angle are measured by using a configuration in which at least two droplet images can be obtained for the same droplet by emitting light at different timings of the two light sources. In this case, the same droplet can be measured, the influence of variations in droplet system or ejection timing variation from the nozzle can be eliminated, and a plurality of images of the same droplet can be formed in the same frame. Since the image is taken, data such as the velocity and outer diameter of the droplet can be measured.
[0008]
(2) According to the invention described in claim 2, a droplet to be measured is disposed between a light source and an image of an optical system composed of one or a plurality of lenses for forming an image of the light source. In an inkjet injection inspection apparatus that forms an image on an image sensor, one light source is prepared as the light source, and the light is emitted with different wavelengths in at least two light emission, and imaged through the respective wavelength pass filters. An image is formed on the element, and at least two droplet images are obtained in the same frame.
[0009]
With this configuration, it is possible to accurately obtain at least two images of the same droplet using a single light source, and to measure data such as the velocity and outer diameter of the droplet from these images. it can.
[0010]
(3) The invention described in claim 3 is characterized in that strobe light or laser pulse emission is used as the light source.
With this configuration, even a moving droplet can be detected in an accurate state.
[0011]
(4) The invention described in claim 4 is characterized in that a camera with a shutter is used as the imaging device.
With this configuration, at least two droplet images can be captured by causing the camera to perform at least two shutter operations on the same droplet at high speed.
[0012]
(5) The invention according to claim 5 is characterized in that a light shielding means is provided between the two light sources.
If comprised in this way, the influence of the surrounding interference light can be removed and the same droplet image can be imaged more correctly.
[0013]
(6) The invention according to claim 6 is characterized in that a bright portion at the center of the droplet is masked.
With this configuration, a preferable droplet image can be obtained by masking the center of the droplet, and the droplet can be accurately recognized.
[0014]
(7) The invention according to claim 7 is characterized in that the droplet outer diameter is measured from the density value of the droplet outer diameter portion output from the image sensor.
With this configuration, since the contrast of the outer diameter portion of the droplet is improved, the outer diameter of the droplet can be measured with the maximum resolution from the density value of the outer diameter portion of the droplet.
[0015]
(8) The invention according to claim 8 is characterized in that a colorless and transparent dummy ink is used instead of the ink.
According to this configuration, since dummy ink is used as the droplet, contamination is prevented after the inspection, so that there is no need for cleaning or refilling with ink.
[0016]
(9) According to the ninth aspect of the present invention, an image picked up in the absence of droplets is stored in advance, and an image picked up in the absence of droplets is subtracted from an image picked up in the presence of droplets. It is characterized by.
[0017]
If comprised in this way, the shading correction | amendment of the obtained droplet image can be performed.
DETAILED DESCRIPTION OF THE INVENTION
[0018]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram showing a first embodiment of the present invention. In the figure, 11 is a first light source and 12 is a second light source. The light sources 11 and 12 are different in polarization angle. The light source 11 is a light source a, and the light source 12 is a light source b. As the light sources a and b, a flash light source such as a strobe is used. Let p be the polarization angle of the light source a, and s be the polarization angle of the light source b. Reference numeral 13 denotes a light shielding plate disposed between the light sources a and b.
[0019]
Reference numeral 14 denotes a p-polarizing plate that transmits light from the light source a, and reference numeral 15 denotes an s-polarizing plate that transmits light from the light source b. Reference numeral 16 denotes a lens that collects light from the light sources a and b. A and B are droplets disposed between the polarizing plates 14 and 15 and the lens 16. These droplets are assumed to be the same droplet. That is, as time passes, it exists at the position shown in the figure. Reference numeral 17 denotes a slit having a hole through which only light from each light source passes. The slit 17 is disposed in the vicinity of the image forming points of the light sources a and b. By arranging the slit in the vicinity of the image formation point in this way, the surrounding scattered light is eliminated and only the light traveling straight is transmitted.
[0020]
Reference numeral 18 denotes an s polarizing plate that transmits light from the light source b entering through the slit 17, and 19 denotes a p polarizing plate that transmits light from the light source a that also enters through the slit 17. Reference numeral 20 denotes a photoelectric conversion element that forms a droplet image, and for example, a CCD is used. The operation of the apparatus configured as described above will be described as follows.
[0021]
First, the light source a emits light. This emitted light irradiates the droplet A discharged through the p-polarizing plate 14. In this case, since the p-polarizing plate 14 transmits only the light having the polarization angle p with respect to the light from the light source a, the other noise light is blocked by the p-polarizing plate 14.
[0022]
The light including the image information of the droplet A is collected by the subsequent lens 16. The light condensed by the lens 16 passes through the hole below the slit 17. By providing a hole in the vicinity of the image forming point of the light source, other scattered light can be excluded and only light traveling straight can pass. The light that has passed through this hole passes through the p-polarizing plate 19 and forms an image of the droplet A on the CCD 20. Since the noise light generated thereafter is blocked while passing through the p-polarizing plate 19, the light transmitted through the p-polarizing plate 19 has less noise. An accurate droplet image with less noise is formed on the CCD 20.
[0023]
Next, after a predetermined time has elapsed, the light source b emits light. The emitted light irradiates the droplet B ejected through the s polarizing plate 15. The droplet B exists at a position after the predetermined time has elapsed. In this case, since the s polarizing plate 15 transmits only the light having the polarization angle s with respect to the light from the light source b, other noise light is blocked by the s polarizing plate 15.
[0024]
The light including the image information of the droplet B is collected by the subsequent lens 16. The light condensed by the lens 16 passes through the hole above the slit 17. By providing a hole in the vicinity of the image forming point of the light source, other scattered light can be excluded and only light traveling straight can pass. The light that has passed through this hole passes through the s polarizing plate 18 and forms an image of the droplet B on the CCD 20. Since the noise light generated thereafter is cut off while passing through the s polarizing plate 18, the light passing through the s polarizing plate 18 has less noise.
[0025]
In this way, according to the present embodiment, the same droplet can be measured when measuring the speed and angle. Therefore, variation in droplet system or variation in ejection timing from the nozzles can be achieved. In addition, since a plurality of images of the same droplet are captured in the same frame, data such as the velocity and outer diameter of the droplet can be measured.
[0026]
In the above-described embodiment, the case where two identical droplet images are captured is taken as an example. However, the present invention is not limited to this, and three or more identical droplet images may be captured. Good.
Further, according to the present embodiment, as described above, two light sources having different polarization directions are prepared as light sources, these light sources are made to emit light at different times, and at least two droplets for the same droplet. An image can be obtained.
[0027]
Moreover, as the light sources 11 and 12, a strobe light or laser pulse emission is used, so that even a moving droplet can be detected in an accurate state.
In the above-described embodiment, the case where a droplet image is formed on the image sensor is taken as an example. However, the present invention is not limited to this, and for example, using a camera with a shutter, in synchronization with strobe light emission. Alternatively, a droplet image can be taken asynchronously. That is, at least two droplet images can be taken by performing at least two shutter operations on the same droplet at high speed.
[0028]
In this embodiment, a light shielding plate 13 is provided between the light source a and the light source b. By doing so, it is possible to remove the influence of the surrounding interference light and capture the same droplet image more accurately.
[0029]
FIG. 2 is a block diagram showing a second embodiment of the present invention. The same components as those in FIG. 1 are denoted by the same reference numerals. Compared with the embodiment of FIG. 1, the arrangement of the optical system is different. In the figure, 11 is a light source a, 12 is a light source b, and 13 is a light shielding plate disposed between the light sources a and b. 14 is a p-polarizing plate that transmits only p-polarized light, and 15 is an s-polarizing plate that transmits only s-polarized light.
[0030]
Reference numeral 21 denotes a lens for condensing light from each of the light sources 11 and 12, 22 denotes an ink discharge nozzle provided at a subsequent stage of the lens 21, and 23 denotes droplets discharged from the nozzle 22. The droplets shown here are the same droplets and have moved with the passage of time.
[0031]
Reference numeral 17 denotes a slit provided in the vicinity of the imaging of the light sources 11 and 12. The hole above the slit allows s-polarized light to pass, and the hole below allows p-polarized light to pass. Reference numeral 18 denotes an s polarizing plate that transmits s-polarized light, and reference numeral 19 denotes a p-polarizing plate that transmits p-polarized light. Reference numeral 24 denotes a lens for forming a droplet, which is arranged at the subsequent stage of the polarizing plates 18 and 19, and 20 denotes a CCD on which a droplet image is formed. The operation of the apparatus configured as described above will be described below with reference to the time chart of FIG.
[0032]
In FIG. 3, (a) is a vertical synchronization signal, (b) is a head drive signal, (c) is a light emission signal, (d) is a light emission, (e) is b light emission signal, and (f) is b light emission. is there.
When the vertical synchronizing signal (a) of the image display means (not shown) becomes “H”, the head driving signal (b) becomes “H” after a predetermined time has elapsed. The a emission signal (c) becomes “H” after a predetermined time t1 has elapsed since the head drive signal (b) became “H”. The light source a emits light after a slight time difference from when the a light emission signal (c) becomes “H”.
[0033]
When the light source a emits light, the emitted light passes through the p-polarizing plate 14, and the transmitted light is collected by the lens 21. The light condensed by the lens 21 irradiates the droplet 23. Light including the image information of the droplet 23 enters the slit 17 and reaches the p-polarizing plate 19. The light transmitted through the p polarizing plate 19 forms an image of a droplet on the CCD 20 by the lens 24.
[0034]
The b emission signal (e) becomes “H” after a predetermined time t2 has elapsed since the head drive signal (b) became “H”. The light source b emits light after a slight time difference from the b light emission signal (c) becoming “H”.
[0035]
When the light source b emits light, the emitted light is transmitted through the s polarizing plate 15, and the transmitted light is collected by the lens 21. The light condensed by the lens 21 irradiates the droplet 23. Light including the image information of the droplet 23 enters the slit 17 and reaches the p-polarizing plate 19. The light transmitted through the p polarizing plate 19 forms an image of a droplet on the CCD 20 by the lens 24.
[0036]
With the above sequence, at least two images of the same droplet are formed on the CCD 20. When this image is displayed on an image display means (not shown), various kinds of information about the droplet can be obtained.
[0037]
FIG. 4 is a diagram showing an example of a droplet image obtained in this way. In the figure, images of three droplets are displayed with time. From this figure, the time between two points of the same droplet is known, and the distance is also known. From this, the velocity of the droplet can be calculated. Furthermore, the diameter of the droplet can be calculated from the shape of the droplet in these images.
[0038]
With this configuration, when measuring speed and angle, the same droplet can be measured, so the influence of variations in the droplet system or ejection timing from the nozzle can be eliminated. In addition, since a plurality of images of the same droplet are captured in the same frame, data such as the velocity and outer diameter of the droplet can be measured.
[0039]
In the above-described embodiment, the case where two flash light sources are used in order to obtain two identical droplet images is taken as an example. However, the present invention does not necessarily use two light sources. A plurality of images of the same droplet can be obtained using one light source. For example, a laser beam is used as a flash light source, and measurement is performed by changing the laser wavelength between the first measurement and the second measurement.
[0040]
If two or more droplets are continuously imaged using the same wavelength, an image cannot be accurately captured. At the same wavelength, a dark place becomes brighter and an originally bright place becomes darker, and normal photographing cannot be performed. That is, light interference occurs.
[0041]
Therefore, light is emitted at different wavelengths, and a droplet image irradiated by the laser is formed on the image sensor after passing through the band-pass filter. In this way, since there is no interference between the first light emission and the second light emission, two images can be obtained for the same droplet. Note that the number of light emission is not limited to two, and it is also possible to obtain three or more droplet images by emitting light a plurality of times while changing the wavelength. In this way, it is possible to accurately obtain at least two images of the same droplet using one light source.
[0042]
In the embodiment described above, the optical system can be used in combination with the optical system in the main scanning direction of the ink jet printer. With this configuration, the configuration is simplified.
[0043]
Further, according to the present embodiment, by masking the bright portion at the center of the droplet, it is possible to obtain a preferable droplet image by masking the center of the droplet.
In addition, according to the present embodiment, the droplet outer diameter can be measured from the concentration value of the droplet outer diameter portion. With this configuration, since the contrast of the outer diameter portion of the droplet is improved, the outer diameter of the droplet can be measured with the maximum resolution from the density value of the outer diameter portion of the droplet.
[0044]
In addition, according to the present embodiment, by using a colorless and transparent dummy ink instead of the ink, the dummy ink is used to prevent contamination after inspection in order to prevent contamination or re-inking. There is no need for filling.
[0045]
In addition, according to the present embodiment, an image captured in the absence of droplets is stored in advance, and an image captured in the absence of droplets is subtracted from an image captured in the presence of droplets. The shading correction of the obtained droplet image can be performed. This utilizes the fact that the relationship between the illumination optical system and the light receiving optical system does not change except for the liquid droplet to be measured.
【The invention's effect】
[0046]
As described above, according to the present invention, the following effects can be obtained.
(1) According to the first aspect of the present invention, when measuring the speed and angle by adjusting the light emission timing of the light source so that at least two identical droplet images are included in one frame, the same droplet is used. Since it is possible to eliminate the effects of variations in droplet systems or variations in ejection timing from nozzles, multiple images of the same droplet can be captured in the same frame. Data such as the velocity and outer diameter of the droplet can be measured.
[0047]
(2) According to the second aspect of the invention, it is possible to accurately obtain at least two images of the same droplet by using one light source, and the velocity, outer diameter, etc. of the droplet can be obtained from these images. Data can be measured.
[0048]
(3) According to the invention described in claim 3, even a moving droplet can be detected in an accurate state.
(4) According to the invention described in claim 4, at least two droplet images can be taken by causing the camera to perform at least two shutter operations on the same droplet at high speed.
[0049]
(5) According to the invention described in claim 5, the same droplet image can be taken more accurately by removing the influence of surrounding interference light.
(6) According to the invention described in claim 6, a preferable droplet image can be obtained by masking the center of the droplet, and the droplet can be accurately recognized.
[0050]
(7) According to the seventh aspect of the invention, since the contrast of the droplet outer diameter portion is improved, the droplet outer diameter can be measured with the maximum resolution from the density value of the droplet outer diameter portion.
(8) According to the invention described in claim 8, since dummy ink is used as the droplet, contamination is prevented after the inspection, so that it is not necessary to clean or refill the ink.
[0051]
(9) According to the invention described in claim 9, shading correction of the obtained droplet image can be performed.
As described above, according to the present invention, it is possible to provide an ink jet ejection inspection apparatus that can measure the state of a droplet discharged from an ink head for the same droplet a plurality of times and accurately detect the state.
[Brief description of the drawings]
[0052]
FIG. 1 is a configuration diagram showing a first exemplary embodiment of the present invention.
FIG. 2 is a configuration diagram showing a second exemplary embodiment of the present invention.
FIG. 3 is a time chart showing the operation of the second exemplary embodiment.
FIG. 4 is a diagram showing an example of an obtained droplet image.
FIG. 5 is a diagram illustrating a configuration example of a conventional apparatus.
[Explanation of symbols]
[0053]
DESCRIPTION OF SYMBOLS 11, 12 Light source 13 Light-shielding plate 14 P polarizing plate 15 s polarizing plate 16 Lens 17 Slit 18 s polarizing plate 19 p polarizing plate 20 Light receiving element

Claims (9)

Inkjet ejection in which a droplet to be measured is placed between a light source and an image of an optical system composed of one or a plurality of lenses that form an image of the light source, and an image of the droplet is formed on the image sensor In inspection equipment,
Two light sources having different polarization directions are prepared as the light sources, these light sources are made to emit light at different light emission timings, and an image of the liquid droplet is formed on an image sensor via a polarization optical system, and within the same frame. An inkjet injection inspection apparatus configured to obtain at least two droplet images. Inkjet ejection in which a droplet to be measured is placed between a light source and an image of an optical system composed of one or a plurality of lenses that form an image of the light source, and an image of the droplet is formed on the image sensor In inspection equipment,
One light source is prepared as the light source, and at least two times of light emission, the light is emitted with different wavelengths, and images are formed on the image sensor through the respective wavelength pass filters, and at least two light sources are formed in the same frame. An ink jet injection inspection apparatus configured to obtain a droplet image.   The ink jet injection inspection apparatus according to claim 1 or 2, wherein a strobe light or pulsed light emission of a laser is used as the light source.   The inkjet ejection inspection apparatus according to claim 1, wherein a camera with a shutter is used as the imaging element.   The ink jet injection inspection apparatus according to claim 1, wherein a light shielding unit is provided between the two light sources.   6. The ink jet injection inspection apparatus according to claim 1, wherein a bright portion at the center of the droplet is masked.   The inkjet ejection inspection apparatus according to claim 1, wherein the outer diameter of the droplet is measured from the density value of the outer diameter portion of the droplet output from the imaging device.   8. An ink jet injection inspection apparatus according to claim 1, wherein a colorless and transparent dummy ink is used instead of the ink.   9. An image picked up in the absence of droplets is stored in advance, and an image picked up in the absence of droplets is subtracted from an image picked up in the presence of droplets. An ink jet injection inspection apparatus according to claim 1.

Images