JP3703418B2 - Method and apparatus for measuring flying object position - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for measuring the flying position of a flying object such as a micro liquid or a micro solid, and more particularly to a flying object position measuring method and apparatus suitable for inspecting a liquid ejection recording head used in a liquid ejection recording apparatus. It is.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, there is known a liquid discharge recording apparatus that forms an image by discharging droplets from a discharge port of a liquid discharge recording head (hereinafter referred to as a recording head) and landing on a recording medium such as paper or an OHP sheet. In liquid discharge recording devices, high definition and high image quality are required, and variations in the landing position of the ejected droplets may affect density unevenness and color tone deviation in color images, resulting in high definition and high image quality. It will be a hindrance. In order to prevent the occurrence of such a problem, the landing position measurement of the ejected droplets is performed as one of the inspection items of the droplet ejection characteristics of the manufactured recording head.
[0003]
As such a landing position measuring method, for example, as described in JP-A-7-329302, a predetermined inspection pattern is printed on a recording medium, and the printed pattern is visually observed or imaging and image processing are performed. A method for inspecting droplet landing by performing the method is known. In addition, as described in JP-A-2000-62158, at least one droplet is ejected from the ejection port of the recording head, and landed on a recording medium such as paper that is spaced apart from the ejection port surface, and the ejection port In addition, the droplets landed on the recording medium are recognized by an image processing camera arranged below the recording medium and image-processed to measure the respective coordinates, and the droplet landing position and the ejection port position are measured. There is a way to do it.
[0004]
Further, as proposed in Japanese Patent Laid-Open No. 2000-280461, laser light is emitted to the light receiving element, liquid droplets are ejected toward the optical axis of the laser light, and landing is performed by optically detecting the liquid droplets. A method for obtaining the position is also known.
[0005]
[Problems to be solved by the invention]
However, as described in JP-A-7-329302 and JP-A-2000-62158, in the method of observing and measuring the landing position by actually landing the droplet on the recording medium, the droplet at the time of landing There is a limit to the accuracy with which the droplet landing position can be measured by repelling, spreading, or bleeding.
[0006]
In the method proposed in Japanese Patent Laid-Open No. 2000-280461, the droplet flying position is detected while the droplet is flying, and there are no problems such as droplet repelling, spreading, and bleeding due to droplet landing. It is possible to determine whether or not a droplet has landed at a desired landing position. However, how much the landing position of the liquid droplet deviates from the desired landing position cannot be measured with an accuracy less than the size of the light receiving element. Further, in the method disclosed in Japanese Patent Laid-Open No. 2000-280461, only the landing position in one direction is known.
[0007]
The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide a flying object position measuring method and apparatus that can more accurately measure the arrival position of a flying object.
[0008]
[Means for Solving the Problems]
The purpose of the present invention is to A light beam shaped in a sheet shape on a known plane corresponding to the arrival position of the flying object to be measured is emitted, The flying object is discharged from the discharge port so as to cross the light beam, and the light generated when the flying object hits the light beam The plane including the traveling vector of the light beam at the position where the flying object intersects the light beam and the incident optical axis of the imaging unit is arranged to be perpendicular to the known plane. Images taken by the imaging unit and taken images From A flying object position measuring method comprising: measuring a reaching position of a flying object on a reaching surface by calculating a coordinate component in a direction perpendicular to a plane including a traveling vector of the light flux and an incident optical axis of an imaging unit. Achieved by:
[0009]
The object of the present invention is to The sheet was shaped into a known plane corresponding to the arrival position of the flying object to be measured Means for emitting the luminous flux, and ejecting the flying object from the ejection port so as to cross the emitted luminous flux, A plane including the traveling vector of the light beam at the position where the flying object intersects the light beam and the incident optical axis of the imaging unit is arranged to be perpendicular to the known plane, Means for imaging light generated when the flying object hits the luminous flux, and the captured image From And means for measuring the arrival position of the flying object on the arrival surface by calculating a coordinate component in a direction perpendicular to a plane including the traveling vector of the light flux and the incident optical axis of the imaging means. Achieved by a flying object position measuring device.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. First, the principle of the present invention will be described. In the following description, droplets ejected from the liquid ejection recording head will be described as an example of flying objects.
[0011]
According to the research by the inventors of the present application, when the light emitted when the horizontally positioned light beam intersects the flying droplet is imaged from obliquely below the light beam, the light incident on the imaging unit shows the shape of the entire droplet. Rather, it was found that only the light emitted from a part of the droplet was captured. FIGS. 1A to 1C are diagrams for explaining this. FIGS. 1A and 1B are diagrams illustrating an example of a positional relationship when the imaging unit 4a captures light emitted when the droplet 2 crosses the light beam 3a. FIG. 1A is a view from the side, and FIG. 1B is a view from the top. The light beam 3a is horizontal (parallel to the xy plane), the droplets fly parallel to the z axis, and a plane including the optical axis of the imaging unit 4a and the optical axis of the light beam 3a is positioned parallel to the yz plane. The imaging unit 4a is located obliquely below the light beam 3a. FIG. 1C schematically shows an image captured when the droplet 2 is present in the light beam in this positional relationship.
[0012]
In FIG. 1C, the outer shape of the droplet 2 is drawn. This outer shape of the droplet is an image that can be seen when it is assumed that the illumination is performed from all directions. However, since it is assumed here that the light beam is applied only from one direction, the outer shape of the central section of the droplet as shown in FIG. Only the incident light image 15 emitted from a part of the droplet is photographed. The incident light image 15 and the droplet outer shape are symmetric with respect to an axis parallel to the Y axis, and the symmetry axes coincide with each other.
[0013]
Therefore, by processing the incident light image 15 to be imaged and calculating the X direction component of the symmetry axis, the position of the droplet center in the x direction at the position where the droplet intersects the light beam can be determined. Although this position accuracy depends on the resolution of the acquired image, if the incident light image 15 is enlarged using an image pickup unit with a high lens magnification and subjected to image processing such as centroid calculation to determine the position in the x direction, It is possible to measure to the accuracy below the size of the light receiving element, which was impossible, and the position accuracy below 1/10 of the outer diameter of the droplet.
[0014]
As described above, in the present invention, the component in the direction perpendicular to the plane including the traveling vector of the light beam and the incident optical axis of the image pickup unit at the position where the liquid droplet intersects the light beam can be measured with high accuracy below the droplet diameter. In addition, unlike the conventional example, measurement is performed while the droplets are flying, so that the droplets shed and spread when landing on the recording medium, which occurred in the conventional example. High-precision measurement is possible without causing errors such as bleeding.
[0015]
Next, an embodiment of the present invention will be described based on such a principle.
[0016]
(First embodiment)
FIG. 2 is a diagram showing a first embodiment of the flying object position measuring apparatus of the present invention. In FIG. 1, reference numeral 1 denotes a liquid discharge recording head (hereinafter referred to as a recording head) that forms an image by discharging droplets. In the present embodiment, a case where the arrival position of the droplets ejected from the recording head 1 on the arrival surface is measured will be described as an example. The recording head 1 is installed on the stage component so as to eject the droplet 2 downward in the vertical direction, and can be adjusted to a desired position.
[0017]
Specifically, the recording head 1 can be moved three-dimensionally by an xy stage 10 and a z stage 11. The xy stage 10 moves the recording head 1 in the lateral direction and the depth direction with respect to the paper surface of FIG. 1 to adjust the position of the xy plane. The z stage 11 adjusts the position in the z direction by moving the recording head 1 in the z direction (up and down in the drawing). The position resolution of the xy stage 10 and the z stage 11 is 0.1 μm. In addition, the recording head 1 can be positioned with a degree of parallelism in the rotational direction and height of 0.1 μm by the rotation mechanism 13 and the tilting mechanism 12. That is, the tilt mechanism unit 12 adjusts the level of the xy plane of the recording head 1, and the rotation mechanism unit 13 adjusts the angle of the recording head 1 on the xy plane. All the operating components such as these stages have electric motors (not shown), and operate by external control.
[0018]
Next, a method for positioning the recording head 1 will be described. In order to position the recording head 1, first, the parallelism in the z direction is adjusted. At that time, a laser displacement meter 9 with an accuracy of 0.1 μm or less arranged at the lower part of the measurement area is used. This laser displacement meter 9 measures the distance between three predetermined points on the lower surface of the recording head 1 and the three points to the laser displacement meter 9, and uses a tilting mechanism unit 12 so that the lengths coincide with each other. Adjust the parallelism. Next, the z stage 11 is operated so that the z-direction position of the lower surface of the ejection port of the recording head 1 is located at the z origin. The z origin is the position where the output of the laser displacement meter 9 is zero. Therefore, the distance between the lower surface of the discharge port of the recording head 1 and the laser displacement meter 9 is measured by the laser displacement meter 9, and the z stage 11 is operated so that the output of the laser displacement meter 9 becomes zero. Thus, the adjustment of the parallelism in the z direction of the recording head 1 is completed.
[0019]
Next, the discharge ports of the recording head 1 are imaged by the CCD cameras 6a and 6b, and the xy stage 10 is manually operated so that the discharge port is positioned at the origin position on any predetermined monitor. The imaging units 4a and 4b and the CCD cameras 6a and 6b are aligned so that the focal point is at the z origin. Here, a plurality of ejection openings of the recording head 1 are formed side by side, and the arrangement direction of the ejection openings is set to one of the feeding directions of the xy stage 10 (lateral direction or depth direction with respect to the paper surface of FIG. 1), or It is made to correspond to the advancing direction of sheet light 3a, 3b. Then, the positions of the ejection ports are confirmed on the monitor while moving the recording head 1 in any of the above directions on the xy stage 10, and the positions of the plurality of ejection ports are shifted in a direction perpendicular to the feeding direction of the xy stage 10. The θ direction of the recording head 1 (rotation direction of the recording head on the xy plane) is adjusted by using the rotation mechanism unit 13 so as not to be present.
[0020]
Next, when the discharge port to be measured is brought close to the origin on the monitor, the origin and the center of the discharge port are aligned with an accuracy of 0.1 μm or less by origin alignment control by image processing. With the above operation, the position of the ejection port of the recording head 1 can be positioned with an accuracy of 0.1 μm or less in the x, y, z, and θ directions. Further, the z stage 11 is operated to raise the recording head 1 in the z direction by a specified length. This length corresponds to the length of the ejection surface and the measurement surface (droplet arrival surface) of the recording head 1, and is 1.2 mm in this embodiment. Here, in the present embodiment, the apparatus is a device that measures the flying position of the droplet, but the plane that forms the central axis of the sheet light 3a and 3b is regarded as the arrival plane, and the arrival position of the droplet is measured. Therefore, the measurement value according to the present embodiment indicates the amount of deviation of the arrival position of the droplet with respect to the ejection port center of the recording head 1, and the distance between the arrival surface and the ejection port surface of the recording head 1 is also known. The direction can also be calculated.
[0021]
In this embodiment, two sheet-like light beams 3a and 3b are used. That is, on the horizontal plane at z = 0, two sheet-like laser beams 3a and 3b having a width of 4 mm and a minimum thickness of 10 μm are laid out so as to be orthogonal to each other. The position of the sheet light 3a, 3b is adjusted during assembly so that the center of the intersection of the central axes of the traveling directions coincides with the position of the origin on the monitor. The laser 7 which is the light source of the sheet light 3a, 3b has a good compatibility with the CCD cameras 6a, 6b and is a short wavelength, so it is a continuous YAG second harmonic with a wavelength of 532 nm, which is advantageous in terms of position measurement. A light emitting green laser is used. The output of the laser 7 is 500 mW.
[0022]
The laser light of the laser 7 is branched in two directions by the fiber cable 22, and the branched light is shaped into sheet-like light beams 3a and 3b by the sheet light shaping optical system 8 and emitted so as to be orthogonal to each other. When the luminous flux is shaped into a sheet, the thinner the luminous flux in the z direction, the easier it is to align the central axis of the luminous flux at the position of z = 0. Since the light that hits the light beam and is emitted therefrom becomes strong, there is an advantage that an image with good contrast can be acquired.
[0023]
In this way, the droplets are ejected toward the center of the intersection of the sheet light 3a and 3b, and the scattered light generated when the sheet light passes through is imaged by the CCD cameras 6a and 6b of the two imaging units 4a and 4b. Imaging optical systems 5a and 5b are attached to the CCD cameras 6a and 6b, respectively, and the imaging target is enlarged 10 times and taken. Further, the projection axis of the optical axis of the imaging unit 4a onto the xy plane coincides with the central axis of the sheet light 3a, and the angle formed by the optical axis of the imaging unit 4a and the central axis of the sheet light 3a is 45 degrees. In addition, the projection axis of the optical axis of the imaging unit 4b onto the xy plane coincides with the central axis of the sheet light 3b, and the angle formed by the optical axis of the imaging unit 4b and the central axis of the sheet light 3b is 45 degrees. The two imaging units 4a and 4b are arranged.
[0024]
It should be noted that the measurement can be sufficiently performed if there is a travel vector 3a (3b (corresponding to 4b)) on the projection axis of the imaging unit 4a (4b) on the xy plane of the optical axis. However, the energy density is higher as the luminous flux is closer to the center. Therefore, if it carries out as mentioned above, the light quantity radiate | emitted from liquid suit can be increased more.
[0025]
Polarizers 14a and 14b are attached to the imaging units 4a and 4b, and a half-wave plate is provided in the sheet light shaping optical system 8. While the discharged liquid droplets are imaged by the CCD cameras 6a and 6b, the rotation direction positions of the polarizing plates 14a and 14b and the half-wave plate are adjusted, and the light from the sheet light 3a is transmitted to the CCD camera 6a and from the sheet light 3b. The light from the sheet light 3a is cut by the polarizing plate 3b, and the light from the sheet light 3b is cut by the polarizing plate 3a. If the transmission axes of the polarizing plates 14a and 14b are appropriately adjusted without a half-wave plate, the light from the sheet light 3a out of the light incident on the CCD camera 6a is more than the light from the sheet light 3b. In many cases, the light from the sheet light 3b out of the light incident on the CCD camera 6b can be made larger than the light from the sheet light 3a. In this case, two incident lights can be separated by a process in image processing, for example, a difference in luminance values of both incident lights. A polarizing beam splitter may be used instead of the polarizing plate.
[0026]
Here, when one light beam having a specific traveling direction hits the droplet, the direction of the light emitted from the droplet covers various directions because the droplet surface is a curved surface. Therefore, when a plurality of light beams strike one droplet, light emitted from the droplets may enter the same single imaging unit even if the traveling directions of the light beams are different from each other. Then, one image can be obtained without distinguishing incident light resulting from the plurality of light beams.
[0027]
On the other hand, in order to specify the position of the droplet by the above method, it is necessary to recognize that the progress of the light beam is known and to distinguish the light emitted from the droplet when the light beam hits the droplet from the light emitted from others. Therefore, if the incident light image obtained from the acquired image is formed by incident light from a plurality of light beams, and it is difficult to separate and determine for each incident light from each light beam, the droplet coordinates are obtained from the image. Large errors may occur. Therefore, if an optical element that transmits light only in a specific polarization direction, such as a polarizing plate, is disposed on the optical axis of the imaging unit, unnecessary light can be cut due to the difference in the polarization state of incident light.
[0028]
In the present embodiment, the ejection frequency of the recording head 1 is driven at 100 Hz, and the capture frequencies of the CCD cameras 6a and 6b are driven at 10 Hz. The exposure time and the start timing of the CCD cameras 6a and 6b are controlled by the signal ON time of the signal input from the outside and the timing at which the signal is turned ON. In the present embodiment, the exposure time in one photographing is set to 100 μs, and the drive signal of the recording head 1 is input to the CCD cameras 6a and 6b via a thinning circuit and a delay unit (not shown). The signal of 10 Hz is extracted from the signal of frequency 100 Hz by the thinning circuit, and the timing of the signal input to the CCD cameras 6 a and 6 b is adjusted by the delay device so that one droplet is photographed by one photographing. .
[0029]
Further, cyan ink used as ink for the printer is used as the droplet, and the outer diameter of the discharged droplet is about 20 μm. In this manner, the droplets ejected from the recording head 1 are imaged by the CCD cameras 6a and 6b. FIG. 3 shows an image of a droplet imaged by the CCD camera 6a. FIG. 4 is a schematic view seen from the z direction for explaining the obtained droplet coordinates.
[0030]
Here, in FIG. 3, the droplet is symmetric with respect to an axis parallel to the Z axis. This is because the plane including the optical axis of the imaging unit 4a and the central axis of the sheet light 3a is substantially parallel to the z-axis direction in which the droplets fly. Further, the light incident on the CCD camera 6a is from the sheet light 3a, and the light from the sheet light 3b is cut by the polarizing plate 14a. Therefore, since the position in the X direction of the symmetry axis of the droplet photographed as described above coincides with the position in the x direction of the droplet that is the object to be photographed in FIG. 4, the center of gravity of the droplet image with respect to the monitor origin is calculated. Then, the X coordinate value of the gravity center position is set as the x-direction position of the droplet 2. Similarly, the y-direction position of the droplet 2 is determined from the image photographed by the CCD camera 6b.
[0031]
These calculation processes are performed by an arithmetic processing unit (microcomputer) (not shown). In the present embodiment, the resolution of the captured image is 0.6 μm, and since the center of gravity is calculated, the measurement error may be considered to be one pixel or less. That is, the position of the droplet can be measured with an accuracy of 1/10 or less of the outer diameter of the droplet. Note that the two-dimensional coordinates on the image are converted into the position coordinates in the real space, and the position of the droplet 2 on the arrival surface is determined. In the present embodiment, as described above, the ejection port center point of the recording head 1 is set as the origin on the xy plane, and the positioning accuracy is set to 0.1 μm. Therefore, the landing position of the droplet with respect to the ejection port can be measured with an accuracy of 0.1 μm. Further, since the distance between the measurement xy surface and the ejection port surface of the recording head 1 is also known, not only the landing position but also the droplet flight direction can be known.
[0032]
When the droplets fly obliquely with respect to the xy plane, the acquired incident light image is also inclined by the thickness of the sheet light, but the X and Y coordinates of the gravity center coordinates of the droplets are z Since it corresponds to the center position x, y of the flying droplet on the xy plane of = 0, the measured value can be calculated without any problem in terms of accuracy if it is processed by the above method. Further, in the present embodiment, the droplet coordinates are obtained by the combination of the sheet light 3a and the imaging unit 4a, and the sheet light 3b and the imaging unit 4b. However, even in the case of one sheet light and one imaging unit, the coordinates of the droplet are obtained. It is possible to get. In this case, since there is one sheet light, it is not necessary to cut the light emitted when another sheet light hits the droplet. Therefore, a polarizing plate and a half-wave plate are not necessary. Also, the coordinate values in the direction perpendicular to the height direction z, the traveling vector of the sheet light, and the optical axis of the imaging unit can be determined by the method described so far.
[0033]
Furthermore, when it is desired to determine the remaining one axis (the Y axis in FIG. 1C), the calculation is made from the Z direction position of the incident light image in FIG. That is, as shown in FIG. 1 (c), the center of gravity of the incident light image 15 and the center of gravity of the liquid droplet outline image (not visible in FIG. 4) seen when illuminated from all directions are the Z-direction coordinates of both. Is different. But measurement Target If the external shape of the droplet is known, it is possible to calculate from which position of the droplet the light of the incident light image 15 is derived. Therefore, from the Z coordinate value of the center of gravity of the incident light image 15, the droplet It is possible to specify the position of the sheet light in the traveling direction.
[0034]
Further, in the apparatus configuration of the present embodiment, the sheet light hits the droplet and the light that has been transmitted and refracted enters the imaging unit, but the traveling directions of the sheet light 3a and 3b are reversed. Arrangement may be taken. In this case, the light reflected by the sheet light on the droplet is imaged. In particular, when the droplet is a pigment ink, light does not pass therethrough, so the reflected light must be imaged.
[0035]
(Second Embodiment)
FIG. 5 is a view showing a second embodiment of the flying object position measuring apparatus of the present invention. The difference from the first embodiment is that the lasers 7a and 7b having two different wavelengths are used, and the laser light emitted from the lasers 7a and 7b is directly used for the sheet light shaping optical system 8 without using a fiber cable. The incident point is that bandpass filters 16a and 16b are used instead of the polarizing plates 14a and 14b. Other configurations are the same as those in FIG.
[0036]
The laser 7a is a YAG second harmonic CW green laser with a wavelength of 532 nm and the output is 200 mW. The laser 7b is a CW air-cooled Ar laser with a wavelength of 488 nm and the output is 100 mW. The laser beams output from both lasers enter the sheet light shaping optical system 8 and are shaped into sheet-like laser beams 3a and 3b having a width of 4 mm and a minimum thickness of 10 μm, as in the first embodiment, and orthogonal to each other. Is emitted. Unlike the first embodiment, the sheet light shaping optical system 8 does not necessarily include a half-wave plate.
[0037]
Band-pass filters 16a and 16b are installed in the imaging units 4a and 4b, respectively. The bandpass filter 16a transmits light having a wavelength of 532 nm and does not transmit light having a wavelength of 488 nm. The band pass filter 16b transmits light having a wavelength of 488 nm and does not transmit light having a wavelength of 532 nm. Thereby, only the light from the sheet light 3b is incident on the imaging unit 4a, and the light from the sheet light 3b is incident on the imaging unit 4b.
[0038]
The ejected droplets were cyan ink used as printer ink. When droplets were ejected with this apparatus configuration, the captured image was the same as in FIG. Accordingly, as in the first embodiment, the droplet position coordinates in the direction perpendicular to the plane including the optical axis of the imaging unit and the central axis of the sheet light can be calculated from the images captured by both CCD cameras, and the landing of the droplet The position can be measured.
[0039]
(Third embodiment)
FIG. 6 is a diagram showing a third embodiment of the present invention. The difference from the second embodiment is that the two optical axes of the imaging unit are bent by a mirror 18 and a triangular prism 19 so that an image is formed on the imaging surface of the same CCD camera 6. With this configuration, since only one CCD camera is used, there is an advantage that the number of images to be acquired and the data capacity are halved. Also, the cost can be reduced.
[0040]
The imaging unit 5 has a structure including a 10 × microscope lens 17, bandpass filters 16 a and 16 b, a mirror 18, and a triangular prism 19. In FIG. 6, the optical axis on the left side of the imaging unit 5 is at a position that is inward from the left end surface of the imaging surface of the CCD camera 6 by a length that is ¼ of the size of the light receiving unit. The position of the CCD camera 6 is adjusted so as to form an image at a position that is inward from the right end surface of the imaging surface by a quarter of the light receiving portion size. The image origin described in the first embodiment is also determined as a position on the monitor corresponding to the imaging position.
[0041]
The bandpass filter 16a transmits light having a wavelength of 532 nm and does not transmit light having a wavelength of 488 nm, as in the second embodiment. The band pass filter 16b has a function of transmitting light having a wavelength of 488 nm and not transmitting light having a wavelength of 532 nm. Other configurations are the same as those in FIG.
[0042]
Here, a glass substrate on which a square lattice pattern is drawn with chrome is placed on a plane of z = 0 including the traveling central axes of the sheet lights 3a and 3b, and an image taken by the imaging unit 5 is shown in FIG. In FIG. 7, it is installed so that the diagonal direction of the grating coincides with the traveling direction of the sheet lights 3a and 3b, and the distance between the gratings is 20 μm. Calibration is performed using the acquired image. That is, the calculation algorithm for converting the two-dimensional coordinates on the image into the position coordinates on the real space is determined by the acquired image.
[0043]
Further, FIG. 8 shows an example of imaging a droplet imaged by this apparatus configuration. The imaged droplet is cyan ink used as ink for the printer. The same applies to the case of FIG. 7, but the flight direction is inclined obliquely due to the structure of the imaging unit. 9 shows an enlarged image of the left side acquired image of FIG. 7, and FIG. 10 shows an enlarged image of the incident light image on the left side of FIG. The spatial axis directions x and z correspond to the diagonal directions X and Z of the lattice in the acquired image. Since the X coordinate value of the center position of the incident light image coincides with the x coordinate value of the droplet center, the x coordinate of the droplet center can be calculated by calculating the center of gravity of the captured incident light image. The y coordinate of the droplet center can be calculated from the image. Note that the two-dimensional coordinates on the image are converted into position coordinates in the real space using a calculation algorithm, and the position of the droplet on the arrival surface is determined.
[0044]
(Fourth embodiment)
FIG. 11 is a diagram showing a fourth embodiment of the present invention. The difference from the third embodiment is that a color CCD camera 6 ′ is used as an imaging device and that bandpass filters 16 a and 16 b are not installed.
[0045]
In this apparatus configuration, both the sheet lights 3a and 3b pass through both optical axes of the image pickup unit 5 and enter the color CCD camera 6 '. An image obtained by the camera is subjected to image processing, and an image having only G (green) and B (blue) color components is obtained. Only the image by the light from the sheet light 3a which is green is transferred to the G (green) color component image. Therefore, the liquid appropriate image on the left side of the image is the same as in FIG. By processing this left liquid appropriate image in the same manner as in the third embodiment, the x coordinate on the liquid appropriate arrival surface is determined. Moreover, only the image by the light from the sheet light 3b which is blue is transferred to the image of the B (blue) color component. Therefore, the y coordinate on the liquid appropriate arrival surface is determined by processing the right liquid appropriate image in the same manner as in the third embodiment.
[0046]
(Fifth embodiment)
FIG. 12 is a diagram showing a fifth embodiment of the present invention. The difference from the second embodiment is that line sensor cameras 20a and 20b are used as imaging devices, and cylindrical lenses 21a and 21b are installed on the optical axes of the imaging units 5a and 5b. The line sensor cameras 20a and 20b are installed so that the element arrangement direction is parallel to the xy plane and the element surface faces upward 45 degrees. The cylindrical lenses 21a and 21b are arranged so as to collect incident light in a direction perpendicular to the element arrangement direction of the line sensor camera and the optical axis of the imaging unit. Other configurations are the same as those in FIG.
[0047]
The line sensor cameras 20a and 20b used in this embodiment have a maximum line rate of 64 kHz. In the operation mode in this embodiment, the exposure time and the start timing thereof are the signal ON time of the signal input from the outside and the signal ON. It is controlled at the timing of switching to.
[0048]
The drive signal of the recording head 1 is inputted to the line sensor cameras 20a and 20b via a delay device, and the CCD camera is used by the delay device so that one droplet is photographed by one photographing. The timing of the input signal is adjusted. In the first embodiment, a thinning circuit is provided between the recording head 1 and the delay unit, and the frequency of the signal input to the CCD camera is reduced to 10 Hz. However, the line sensor cameras 20a and 20b used in this embodiment are not limited to the above. Since the maximum line rate is faster than the maximum drive frequency of the recording head currently conceivable, 30 kHz, the line rates of the line sensor cameras 20 a and 20 b are the same as the ejection frequency of the recording head 1.
[0049]
The droplets to be ejected are cyan ink used as printer ink, and the droplets are ejected with the drive frequency of the recording head 1 set to 10 KHz. FIG. Shown in In this case, since the cylindrical lens is inserted on the optical axis, unlike the first and second embodiments, the light on the same vertical line of the two-dimensional CCD is condensed on one element. Therefore, an image with higher contrast can be obtained. The center of the incident light image of the acquired image is calculated by image processing. From the acquired image of the line sensor camera 20a, the x-direction coordinate of the droplet center is calculated from the acquired image of the line sensor camera 20b. Is obtained. By using a line sensor camera in this way, even when droplets are ejected at a high ejection frequency, the landing position is measured for all droplets for a certain period of time without thinning out the droplets to be measured. Is possible.
[0050]
By inspecting the recording head using the method and apparatus according to the present invention described in the above embodiments, the quality of the recording head to be shipped can be guaranteed at a high level. At this time, if the measured data is fed back to the manufacturing process, a more reliable recording head can be produced efficiently and the manufacturing cost can be reduced. Furthermore, it is also possible to provide a recording head inspection function by providing an apparatus according to the present invention in a drawing apparatus such as a printer. By doing so, it is possible to realize a drawing apparatus with higher accuracy and higher reliability.
[0051]
In the above embodiment, the case where the droplet flying position of the liquid discharge recording head is measured has been described as an example. However, the present invention is not limited to this, and the invention is not limited to this. Can also be used. For example, it can be used for measuring the flying position of spherical powder or spray droplets.
[0052]
【The invention's effect】
As described above, the present invention has the following effects.
(1) Since the position of the flying object is measured by calculating the coordinate component in the direction perpendicular to the plane including the traveling vector of the light beam at the position where the flying object intersects the light beam and the incident optical axis of the imaging unit, The position of the flying object can be measured with an accuracy less than the size of the light receiving element. In addition, since errors such as repelling, spreading, or bleeding on the arrival surface of the flying object do not occur, the position of the flying object on the arrival surface can be measured more accurately than in the past.
(2) By emitting a plurality of light beams so that they intersect at least at one location and ejecting the flying object so that it crosses the crossing area, the position of the flying object can be determined two-dimensionally or three-dimensionally. The position of the flying object can be measured.
(3) By shaping the light beam into a sheet shape, the alignment of the light beam is easy, the energy density of the light beam increases, the flying object hits the light beam, and the light emitted from it becomes stronger, so that an image with good contrast can be obtained, etc. There are advantages.
(4) Only one imaging unit is required by forming images on different regions of one imaging unit by using a plurality of imaging lenses that capture light generated when a flying object hits a plurality of light beams from different directions. In addition, there is an advantage that the amount of operation control such as exposure timing control can be reduced and the number of acquired images is reduced.
(5) By using a line sensor camera for the imaging unit, the amount of captured data is small, and imaging can be performed at high speed.
(6) In addition, by using a lens that collects incident light when using a line sensor camera, it is possible to take an image even when the light incident on the imaging unit is weak, and it can also be used with an imaging device with low sensitivity. is there.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining the principle of the present invention.
FIG. 2 is a diagram showing a first embodiment of a flying object position measuring apparatus of the present invention.
FIG. 3 is a diagram showing an image of a droplet imaged by the CCD camera of FIG. 2;
FIG. 4 is a diagram illustrating droplet coordinates according to the embodiment of FIG.
FIG. 5 is a diagram showing a second embodiment of the present invention.
FIG. 6 is a diagram showing a third embodiment of the present invention.
7 is a diagram illustrating an example of an image of a calibration grid pattern imaged by the imaging unit of the embodiment of FIG. 6;
FIG. 8 is a diagram illustrating an example of a droplet image captured in the embodiment of FIG.
9 is an enlarged view of the image of FIG.
10 is an enlarged view of the droplet image of FIG. 8. FIG.
FIG. 11 is a diagram showing a fourth embodiment of the present invention.
FIG. 12 is a diagram showing a fifth embodiment of the present invention.
13 is a diagram illustrating an example of a droplet image captured in the embodiment of FIG.
[Explanation of symbols]
1 Liquid discharge recording head
2 droplets
3a, 3b sheet light
4a, 4b Imaging unit
5, 5a, 5b Imaging optical system
6,6a, 6b CCD camera
6 'color CCD camera
7 Laser
7a Green laser
7b Blue Laser
8 Optical system for sheet light shaping
9 Laser displacement meter
10 xy stage
11z stage
12 tilt mechanism
13 Mechanism for rotation
14a, 14b Polarizing plate
15 Incident light image
16a, 16b Band pass filter
17 Lens
18 Mirror
19 Triangular prism
20a, 20b Line sensor camera
21a, 21b Cylindrical lens
22 Fiber cable

Claims (11)

The light beam is shaped into a sheet to a known plane corresponding to the arrival position of the flying object to be measured emits ejects flying object from the discharge port across the beam, wherein the flying object is generated when striking the light beam The light is imaged by an imaging unit arranged such that a plane including a traveling vector of the light beam at a position where the flying object intersects the light beam and an incident optical axis of the imaging unit is perpendicular to the known plane. The arrival position on the arrival surface of the flying object is measured by calculating a coordinate component in a direction perpendicular to a plane including the traveling vector of the light flux and the incident optical axis of the imaging unit from the captured image. A flying object position measurement method.   2. The flying object position measuring method according to claim 1, wherein the light beam includes a plurality of light beams, the plurality of light beams are emitted so as to intersect at least at one place, and the flying object is discharged so as to cross the crossing region. . The flying object position measuring method according to claim 2 , wherein an optical element that transmits a light beam having only a corresponding polarization direction among a plurality of light beams is disposed on an optical axis of the imaging unit. 4. The flying object position measuring method according to claim 3 , wherein the transmission axis of the optical element is adjusted so that the luminous flux incident on each imaging unit has a maximum corresponding luminous flux among the plurality of luminous fluxes. . Wherein the plurality of light beams are different wavelengths from each other, according to claim 2, characterized in that the wavelength selective element which transmits only the wavelength of the corresponding light beams of the plurality of light beams on the optical axis of the imaging unit is arranged The flying object position measuring method described in 1. The flying object position measuring method according to claim 2 , wherein the plurality of light beams have different wavelengths, and the imaging unit includes a color CCD camera. By including a plurality of imaging lenses for imaging light generated when the flying object hits a plurality of light beams from different directions, and forming images from the plurality of imaging lenses at different positions of one imaging unit The flying object position measuring method according to claim 1 , wherein images from the plurality of light beams are picked up by a single image pickup unit. The imaging unit includes a one-dimensional light receiving element in which a plurality of light receiving elements are arranged one-dimensionally, and the light receiving elements are arranged in a direction orthogonal to a traveling vector of a light beam and an incident optical axis of the imaging unit. The flying object position measuring method according to any one of claims 1 to 7 . According to claim 8, wherein the alignment direction and the lens for condensing light incident on the imaging unit in a direction perpendicular to the plane including the incident optical axis of the imaging unit of the light receiving element is arranged A flying object position measurement method. The flying object position measuring method according to claim 1 , wherein the flying object is a droplet discharged from a liquid discharge recording head. Means for emitting a light beam shaped into a sheet shape in a known plane corresponding to the arrival position of the flying object to be measured, and ejecting the flying object from an ejection port so as to cross the emitted light beam, and the flying object is the light beam The plane including the traveling vector of the light beam at the position intersecting with the incident light axis and the incident optical axis of the imaging unit is arranged to be perpendicular to the known plane, and images the light generated when the flying object hits the light beam And means for measuring the arrival position of the flying object on the arrival surface by calculating a travel vector of the luminous flux and a coordinate component in a direction perpendicular to a plane including the incident optical axis of the imaging means from the captured image. And a flying object position measuring device.

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