JP2010139357A - Device and method for inspecting nozzle plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for inspecting a nozzle plate capable of focusing a CCD camera in a short time, and a method therefor. <P>SOLUTION: The device for inspecting a nozzle plate includes a set stage 12 with a mother plate 1 set thereto, a moving table 13 to move the mother plate 1 through the set stage 12, a CCD camera 14 to focus on a meniscus formation portion 8 of each nozzle hole 3 to recognize an image, transillumination 17 to illuminate the inside of each nozzle hole 3, a laser displacement meter 15 to measure the distance between the CCD camera 14 and the mother plate 1, and a controller 18 to control these devices, in which the controller 18 includes the steps of acquiring the location information of focusing in each nozzle hole 3 and the distance information to focus on each nozzle hole 3 from the distance and the movement quantity of the mother plate 1 near each nozzle hole 3, and image-recognizing an inside of each nozzle hole 3 continuously from information obtained to inspect the presence of a foreign material 43. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a nozzle plate inspection apparatus and a nozzle plate inspection method for continuously inspecting a plurality of nozzle holes of a nozzle plate incorporated in an inkjet head in the nozzle row direction.

Conventionally, this type of supply plate (plate) appearance inspection device (inspection device) inspects the presence of burrs (foreign matter) inside the communication port based on the imaging result of the communication port (nozzle hole). (See Patent Document 1).
This visual inspection apparatus includes a scanning drive unit that moves a set supply plate in the X, Y, and Z axis directions, a camera that recognizes an image of a communication port formed in the supply plate from above the supply plate, a supply plate And a transmission illumination unit that illuminates the inside of the communication port from below.
In this visual inspection device, the camera recognizes the image by focusing on the communication port to be inspected, and compares it with the image of the communication port without burrs. Inspect all formed communication ports in sequence.
JP 2008-111695 A

  However, in such an appearance inspection apparatus, the camera is focused for each communication port that recognizes an image. In particular, when the supply plate to be inspected is largely distorted, the distance of each communication port to the camera. However, there is a problem that focusing takes time and inspection time becomes long to inspect all the supply plate openings.

  An object of the present invention is to provide a nozzle plate inspection apparatus and a nozzle plate inspection method capable of focusing an image recognition means in a short time.

  The nozzle plate inspection apparatus of the present invention is a nozzle plate inspection apparatus that continuously inspects a plurality of nozzle holes of a nozzle plate incorporated in an inkjet head in the nozzle row direction, and is a set in which the nozzle plate is set A stage, a moving table for moving the nozzle plate in the nozzle row direction via the set stage, and focusing on each nozzle hole at a predetermined depth position from the surface of the nozzle plate, an image of the interior of each nozzle hole An image recognition means for recognizing, a transmitted illumination for illuminating the inside of each nozzle hole from the back surface of the nozzle plate, a laser displacement meter for measuring the distance between the image recognition means and the surface of the nozzle plate, a moving table, an image recognition means, Control means for controlling the transmitted illumination and the laser displacement meter, and the control means moves in the nozzle row direction. Measure the distance in the vicinity of each nozzle hole of the nozzle plate, and acquire the position information of each nozzle hole and the focusing distance information for each nozzle hole based on this measurement result and the amount of movement of the nozzle plate. Based on the information and the distance information, the inside of each nozzle hole in the nozzle plate moving in the nozzle row direction is continuously image-recognized to check for the presence or absence of foreign matter.

  The nozzle plate inspection method of the present invention is a nozzle plate inspection method for continuously recognizing and inspecting the inside of a plurality of nozzle holes of a nozzle plate incorporated in an ink jet head in the nozzle row direction by an image recognition means. Then, while moving the nozzle plate in the nozzle row direction, a measurement process for measuring the distance between the image recognition means and the surface of the nozzle plate in the vicinity of each nozzle hole, and the measurement result and the movement amount of the nozzle plate Based on the position information of each nozzle hole and the distance information of the focusing position of the image recognition means with respect to the inside of each nozzle hole, the nozzle that moves in the nozzle row direction based on the position information and the distance information Image recognition for continuously recognizing predetermined depth positions inside each nozzle hole on the plate And extent, from the recognition result of the image recognition, characterized by comprising a inspection step of inspecting each the presence of foreign matter in the nozzle holes.

  According to these configurations, the position information of each nozzle hole is based on the distance between the image recognition means in the vicinity of each nozzle hole of the nozzle plate moving in the nozzle row direction and the surface of the nozzle plate and the movement amount of the nozzle plate. And focusing distance information for each nozzle hole, and based on the acquired position information and distance information, the predetermined depth position inside each nozzle hole is continuously recognized. The time for focusing on the position can be shortened. As a result, the inspection time for the presence or absence of foreign matter inside all the nozzle holes formed in the nozzle plate can be shortened. In addition, although measurement and image recognition may be performed for every nozzle hole, after measuring for nozzle rows, image recognition for nozzle rows may be performed. Further, the nozzle plate to be inspected may be a single product corresponding to one inkjet head, or a mother plate for taking a plurality of single products.

  The above-described nozzle plate inspection apparatus further includes a Z table for moving the image recognition unit up and down relative to the set stage, and the control unit recognizes each nozzle hole by image recognition and the nozzle holes stored in advance. When the template does not match, it is preferable to execute the image recognition again and the inspection for the presence or absence of foreign matter after controlling the Z table to match the recognition result with the template.

  In the nozzle plate inspection method described above, in the image recognition step, when the recognition result of each nozzle hole by image recognition does not match the template of the nozzle hole stored in advance, the recognition result is moved up and down the image recognition means. It is preferable to perform the image recognition process again after matching the template with the template.

  According to these configurations, even if the nozzle plate is greatly distorted between the measurement position and the nozzle hole and the recognition result does not match the template, the vertical displacement of the image recognition means can be adjusted. Since the recognition result and the template can be matched, the focusing time by the image recognition means can be shortened.

  In this case, it is preferable that the laser displacement meter is composed of a line type arranged in parallel with the nozzle row.

  According to this configuration, since the distance in the vicinity of the image recognition means and the plurality of nozzle holes can be measured at a time, the acquisition time of focusing position information can be shortened, and the inspection time can be shortened.

  In this case, it is preferable that the predetermined depth position is a position corresponding to the meniscus forming portion of each nozzle hole.

  According to this configuration, when the nozzle plate is mounted on the ink jet head, the presence or absence of foreign matter in the meniscus forming portion that causes flight bending or the like can be reliably inspected.

  In this case, it is preferable that the laser displacement meter is attached to the Z table.

  According to this configuration, since the image recognition unit and the laser displacement meter are fixed to the Z table, the distance in the vicinity of the image recognition unit and the nozzle hole is continuously and accurately determined using the above moving table. It can be measured.

  Hereinafter, a nozzle plate inspection apparatus and a nozzle plate inspection method using the same will be described with reference to the accompanying drawings. This inspection device targets a large mother plate (nozzle plate) on which a plurality of nozzle plates adhered to the ejection surface side of the inkjet head are taken, and foreign matter remaining or adhering during the processing of nozzle holes, etc. Inspects for the presence of (mainly metal pieces). Accordingly, first, a mother plate to be inspected and a nozzle plate taken from the mother plate will be briefly described.

  As shown in FIG. 1, the mother plate 1 is formed in a large plate shape in which a plurality of nozzle plates 2 can be taken, and a large number of nozzle holes 3 serving as ejection nozzles of an inkjet head that ejects functional liquid (ink). A plurality of nozzle plate forming portions 4 having the above are arranged and arranged (see FIG. 1A). The mother plate 1 is subjected to press punching after a later-described inspection, and a plurality of nozzle plates 2 are taken.

  Each nozzle plate forming portion 4 is formed with three sets of two nozzle rows 5 in parallel, and each nozzle row 5 is composed of 90 nozzle holes 3 arranged at equal pitches (FIG. 1). (See (b)). In the inspection, the mother plate 1 is set so that the discharge side is the back surface (lower surface) 6, but the opening end on the back surface 6 side of the nozzle hole 3 is perforated at a right angle to the back surface 6, The opening end is perforated in a tapered shape. In the inspection method described later, the presence or absence of the foreign matter 43 is inspected in the meniscus formation portion 8 that has entered about 70 μm from the surface 7 of the nozzle plate 2 (see FIG. 1C). Thereby, when the nozzle plate 2 is mounted on the ink jet head, the presence or absence of the foreign matter 43 of the meniscus forming portion 8 that causes flight bending or the like can be reliably inspected.

  Next, the inspection apparatus 11 will be described with reference to FIG. The inspection apparatus 11 includes a set stage 12 on which the mother plate 1 is set, a moving table 13 that moves the mother plate 1 in the direction of the nozzle row 5 and in a direction perpendicular thereto via the set stage 12, and each nozzle hole 3. On the other hand, the CCD camera (image recognition means) 14 for recognizing the inside of each nozzle hole 3 by focusing to a predetermined depth position from the surface 7 of the mother plate 1 and the surface 7 of the CCD camera 14 and the mother plate 1. The interior of each nozzle hole 3 is illuminated from the back surface 6 of the mother plate 1 and a laser displacement meter 15 that measures the distance to the Z stage 16 that moves the CCD camera 14 and the laser displacement meter 15 up and down relative to the set stage 12. Transmitting illumination 17, a frame (not shown) for supporting these devices, a housing case (not shown) for housing the whole, It is configured. Further, the inspection device 11 includes a control device 18, and the control device 18 comprehensively controls the moving table 13, the Z table 16, the CCD camera 14, and the laser displacement meter 15.

  In this inspection apparatus 11, a set stage 12 having a setting jig 19 is disposed on a moving table 13, and a CCD camera 14, an epi-illumination 20 and a laser displacement meter 15 attached to the Z table 16 face from above. It is like that. In addition, an X-axis transmission opening 23 and a Y-axis transmission opening 24 are formed in the moving table 13, and a stage opening 25 is formed in the set stage 12, and the transmitted illumination 17 faces from below the opening. . The mother plate 1 is positioned and set on the set stage 12 by the setting jig 19, and moves mainly in the nozzle row 5 direction by the moving table 13. Then, the CCD camera 14, the epi-illumination 20 and the laser displacement meter 15 face the moving mother plate 1 from above, while the transmitted illumination 17 faces from below and the inspection is performed.

  The moving table 13 includes an X-axis table 21 for moving the mother plate 1 placed on the set stage 12 in the X-axis direction, which is the direction of the nozzle row 5, and the mother plate 1 placed on the set stage 12 in the Y-axis direction. And a Y-axis table 22 to be moved to each other, and each is connected to the control device 18. An X-axis transmission opening 23 formed slightly smaller than the set stage 12 is formed at the center of the X-axis table 21, and is formed larger than the X-axis transmission opening 23 at the center of the Y-axis table 22. A Y-axis transmission opening 24 is formed. The X-axis transmission opening 23 and the Y-axis transmission opening 24 are located immediately above the transmission illumination 17 so that the inside of each nozzle hole 3 is illuminated via the X-axis transmission opening 23 and the Y-axis transmission opening 24. It has become.

  The transmitted illumination 17 is disposed at a position facing the CCD camera 14 across the moving table 13, that is, directly below the CCD camera 14, and irradiates light from below to the nozzle hole 3 to be inspected. That is, when the image of the nozzle hole 3 is recognized, the inside of the nozzle hole 3 is illuminated by the transmissive illumination 17 through the X-axis transmissive opening 23 and the Y-axis transmissive opening 24. For this reason, when the image of the nozzle hole 3 is recognized by the CCD camera 14, the inside of the nozzle hole 3 through which the light of the transmission illumination 17 is transmitted is imaged as a bright circle (see FIG. 6A).

  Although not shown in particular, the setting jig 19 is formed in a lattice shape so as to correspond to a portion of the mother plate 1 other than the nozzle plate forming portion 4 and presses the mother plate 1 against the set stage 12 in a positioned state. Fix it. Thereby, since distortion of the mother plate 1 can be corrected as much as possible, focusing time by the CCD camera 14 can be shortened, and inspection accuracy can be improved.

  The Z table 16 is disposed directly above the center of the moving table 13 at the home position by a frame, and supports the CCD camera 14 with the epi-illumination 20 and the laser displacement meter 15 so as to be movable up and down. The Z table 16 moves the CCD camera 14, the epi-illumination 20 and the laser displacement meter 15 up and down in the Z-axis direction based on the acquisition results of the measurement process and focusing coordinate acquisition process described later. Thereby, the distance in the vicinity of the CCD camera 14 and the nozzle hole 3 can be continuously and accurately measured using the moving table 13.

  The laser displacement meter 15 employs a so-called two-dimensional laser displacement meter (a so-called line type), and is disposed in the vicinity of the CCD camera 14 in the Y-axis direction. The reference position for distance measurement in the laser displacement meter 15 is set so as to match the reference position for focusing in the CCD camera 14, and the target height of the CCD camera 14 is determined based on the distance measured by the laser displacement meter 15. It has come to be required. In this case, the mother plate 1 of the laser displacement meter 15 (CCD camera 14) is irradiated with the epi-illumination 20 at a position slightly displaced in parallel with the nozzle row 5 from the nozzle row 5 including the nozzle hole 3 to be inspected. The distance to the surface 7 is measured. In this measurement, since the line type laser displacement meter 15 is used, the distances of the positions corresponding to the plurality of nozzle holes 3 are measured in a batch process.

  As shown in FIG. 3, the control device 18 includes a drive unit 31 having various drivers, and a control unit 32 that is connected to each unit and controls the entire inspection apparatus 11. The drive unit 31 includes a movement driver 33 that controls the movement table 13 and a Z driver 34 that controls the Z table 16.

  The control unit 32 includes an interface 35 for connecting each means, a storage area that can be temporarily stored, a RAM 36 that is used as a work area for control processing, and various storage areas. A ROM 37 for storing a control program, a template 42 in which a reference shape of the nozzle hole 3 in an inspection process to be described later is recorded, position information of each nozzle hole 3, focusing distance information by the CCD camera 14 with respect to each nozzle hole 3, and the like; An HDD 38 that stores programs for processing various data, a CPU 39 that performs arithmetic processing on various data according to programs stored in the ROM 37 and the HDD 38, and a bus 40 that connects these to each other are provided.

  The control unit 32 inputs various data from each unit through the interface 35 and causes the CPU 39 to perform arithmetic processing according to a program stored in the HDD 38 (or sequentially read by a CD-ROM drive or the like). The processing result is output to each unit via the drive unit 31. Thereby, the whole inspection apparatus 11 is controlled and various processes are performed.

  Next, an inspection method for the mother plate 1 will be described with reference to FIGS. In this inspection method, the presence or absence of the foreign matter 43 in the part of the nozzle plate 3 that forms the meniscus forming portion 8 of the nozzle plate 3 is sequentially examined, and the mother plate 1 is orthogonal to the nozzle row 5 direction. Based on the measurement process of measuring the distance between the CCD camera 14 and the surface 7 of the mother plate 1 in the vicinity of each nozzle hole 3 while moving in the direction, the nozzles based on the measurement result and the amount of movement of the mother plate 1. A focusing coordinate acquisition step for acquiring position information of the holes 3 and distance information of the focusing position of the CCD camera 14 with respect to the inside of each nozzle hole 3, and a mother plate 1 that moves in the direction of the nozzle row 5 based on the position information and distance information An image recognition process for continuously recognizing a predetermined depth position inside each nozzle hole 3 and a recognition result of image recognition 1, is made whether the foreign object 43 in each nozzle hole 3 from an inspection step of inspecting each.

  As described above, since the mother plate 1 is configured so that a plurality of nozzle plates 2 can be obtained, first, a measurement method when a two-dimensional laser displacement meter is used in the nozzle plate 2 will be described. As shown in FIG. 5A, in the measurement process, the distance between the CCD camera 14 and the surface 7 of the nozzle plate 2 in the vicinity of each nozzle hole 3 on the upper side in the drawing is measured for each nozzle row 5. Then, the measurement is performed in the same manner by moving one row downward in the figure. By repeating this three times, the distance in the vicinity of the CCD camera 14 and the nozzle hole 3 in the nozzle plate 2 is measured. Further, as shown in FIG. 5B, in the mother plate 1, measurement is performed while moving downward from the nozzle plate 2 located at the upper right in the drawing to the lower right in the drawing. After moving all the way to the lower right in the figure, move to the center in the figure, and measure in the same manner while moving up to the upper center in the figure. After moving all the way to the upper center in the figure, move to the left side in the figure and measure in the same way while moving to the lower left side in the figure. Thereby, the distance in the vicinity of all the nozzle holes 3 formed in the mother plate 1 is measured (S1). When the two-dimensional laser displacement meter is not used, the distance between the CCD camera 14 and the surface 7 of the mother plate 1 in the vicinity of each nozzle hole 3 is continuously changed while moving the mother plate 1 in the nozzle row 5 direction. (Not shown).

  In the focusing coordinate acquisition step, the position information of each nozzle hole 3 and the distance information of the focusing position of the CCD camera 14 with respect to the inside of each nozzle hole 3 are acquired from the measurement result and the amount of movement of the mother plate 1 (S2). Specifically, the position information is calculated from the moving speed and time of the mother plate 1 by the moving table 13. The distance information includes the distance from the surface 7 of the nozzle plate 2 to the meniscus forming portion 8 (in this embodiment, the nozzle plate 2 in the measurement result of the laser displacement meter 15 at each nozzle hole 3 position (near position). The position of about 70 μm from the surface 7) is added.

  In the image recognition step, based on the acquired position information and distance information, the position of the meniscus forming portion 8 inside each nozzle hole 3 is continuously recognized while moving the CCD camera 14 up and down as appropriate (S3). Specifically, the nozzle hole 3 to be inspected is moved directly below the CCD camera 14 by moving the set stage 12 by the movement table 13 based on the acquired position information. At the same time, the height of the CCD camera 14 in the Z-axis direction is adjusted based on the distance information.

  Then, the image of the meniscus forming portion 8 of the nozzle hole 3 is recognized by the CCD camera 14 (S4). When the recognition result 41 obtained by the image recognition is compared with the template 42 of the nozzle hole 3 stored in advance and the diameters thereof are substantially matched (when they are within a predetermined range), the CCD camera 14 recognizes them. Focusing is performed so that the result 41 matches the template 42, and the meniscus forming portion 8 of the nozzle hole 3 is recognized (S6). On the other hand, if the recognition result 41 and the diameter of the template 42 do not substantially match (if they are not within the predetermined range), the CCD camera 14 is moved up and down by the Z table 16 (S5), and the recognition result 41 and the template are detected. The image of the meniscus forming portion 8 inside the nozzle hole 3 is recognized in a state in which 42 is matched (S6).

  That is, the latter is performed only when the recognition result 41 is significantly larger or smaller than the template 42. When the CCD camera 14 is moved up and down by the Z table 16, the CCD camera 14 is moved by the Z table 16 so as to be within a predetermined range, and then the focusing (autofocus) is performed by the CCD camera 14. The image 41 may be recognized by matching the result 41 with the template 42.

  In the inspection step, the presence / absence of the foreign matter 43 in each nozzle hole 3 is inspected from the recognition result 41 of the image recognition (S7). Specifically, the recognition result 41 and the template 42 are matched and the recognition result 41 obtained by image recognition (see FIG. 6A) is binarized, whereby the contour of the meniscus forming portion 8 of the imaged nozzle hole 3 is obtained. Clarify (see FIG. 6B). Then, by superimposing the binarized processing image and the template 42 of the nozzle hole 3 stored in advance, the difference between the recognition result 41 and the template 42 is recognized as the foreign matter 43 and the position and area of the foreign matter 43 are obtained. (Refer to Drawing 6 (c) and (d)). Here, if the area of the foreign matter 43 is equal to or greater than a predetermined value, it is determined that the meniscus forming portion 8 of the nozzle hole 3 has “foreign matter 43 (defect)”. It is determined that the meniscus forming portion 8 is “no foreign matter 43 (good)”. In the actual recognition image, the outline of the upper end opening is thinly projected outside the meniscus forming portion 8 because of the depth of field of the CCD camera 14. For this reason, the position of the foreign matter 43 in the depth direction can also be estimated.

  When all the nozzle holes 3 formed in the nozzle plate 2 are sequentially inspected (S8), the inspection is completed from the upper left nozzle hole 3 to the upper right nozzle hole 3 as shown in FIG. Then, one row is moved to the lower side in the figure, and the inspection is performed from the nozzle hole 3 on the upper right side to the nozzle hole 3 on the upper left side in the figure. Then, the inspection is performed in the same manner by moving one row downward in the figure. By repeating this three times, all nozzle holes 3 in the nozzle plate 2 are inspected. Further, when moving to the next nozzle hole 3, the position information and distance information of the inspected nozzle hole 3 are compared with the position information and distance information of the next nozzle hole 3, and the positions of both image recognition positions are compared. The set stage 12 is moved by the movement table 13 by the difference and moved up and down by the Z table 16. As a result, the image of the meniscus forming portion 8 of the next nozzle hole 3 can be recognized only by focusing the CCD camera 14 after the mother plate 1 is moved.

  According to the above configuration, since the meniscus forming portion 8 of each nozzle hole 3 is continuously image-recognized based on the acquired position information of each nozzle hole 3 and distance information of focusing with respect to each nozzle hole 3, a CCD camera is used. It is possible to reduce the time required for focusing 14 to the focusing position. As a result, the inspection time for the presence or absence of the foreign matter 43 in all the nozzle holes 3 formed in the mother plate 1 can be shortened.

(A) is a top view of a mother plate, (b) is a top view of a nozzle plate, (c) is a sectional view of a nozzle hole. It is a schematic diagram of an inspection apparatus. It is a block diagram of the main control system of a test | inspection apparatus. It is a flowchart of an inspection method. (A) in the measurement shows the order of the nozzle rows to be measured, and (b) shows the order of the nozzle plates to be measured. It is explanatory drawing for demonstrating an inspection process. It is the figure which showed the order of the nozzle hole which performs an inspection process.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Mother plate 2 ... Nozzle plate 3 ... Nozzle hole 5 ... Nozzle row 6 ... Back surface 7 ... Front surface 8 ... Meniscus formation part 11 ... Inspection apparatus 12 ... Set stage 13 ... Moving table 14 ... CCD camera 15 ... Laser displacement meter 16 ... Z table 17 ... Transmitted illumination 18 ... Control device 21 ... X-axis table 22 ... Y-axis table 41 ... Recognition result 42 ... Template 43 ... Foreign matter

Claims (7)

A nozzle plate inspection apparatus for continuously inspecting a plurality of nozzle holes of a nozzle plate incorporated in an inkjet head in the nozzle row direction,
A set stage on which the nozzle plate is set;
A moving table for moving the nozzle plate in the nozzle row direction via the set stage;
Image recognition means for recognizing the inside of each nozzle hole by focusing on each nozzle hole at a predetermined depth position from the surface of the nozzle plate;
Transmitted illumination that illuminates the inside of each nozzle hole from the back surface of the nozzle plate;
A laser displacement meter for measuring the distance between the image recognition means and the surface of the nozzle plate;
Control means for controlling the moving table, the image recognition means, the transmitted illumination, and the laser displacement meter,
The control means measures the distance in the vicinity of each nozzle hole of the nozzle plate moving in the nozzle row direction, and based on the measurement result and the movement amount of the nozzle plate, position information of each nozzle hole And the distance information of the focusing for each nozzle hole, and based on the position information and the distance information, the inside of each nozzle hole in the nozzle plate moving in the nozzle row direction is continuously recognized. Then, a nozzle plate inspection device that inspects for the presence or absence of foreign matter. A Z table for moving the image recognition means up and down with respect to the set stage;
The control means controls the Z table to match the recognition result with the template when the recognition result of each nozzle hole by the image recognition does not match the previously stored nozzle hole template. 2. The nozzle plate inspection apparatus according to claim 1, wherein after that, the image recognition is performed again and the inspection for the presence or absence of the foreign matter is performed.   3. The nozzle plate inspection apparatus according to claim 1, wherein the laser displacement meter is formed of a line type arranged in parallel with the nozzle row. 4.   4. The nozzle plate inspection apparatus according to claim 1, wherein the predetermined depth position is a position corresponding to a meniscus forming portion of each nozzle hole. 5.   5. The nozzle plate inspection apparatus according to claim 2, wherein the laser displacement meter is attached to the Z table. A nozzle plate inspection method in which the inside of a plurality of nozzle holes of a nozzle plate incorporated in an ink jet head is image-recognized and inspected continuously in the nozzle row direction by an image recognition means,
A measurement step of measuring a distance between the image recognition means and the surface of the nozzle plate in the vicinity of each nozzle hole while moving the nozzle plate in the nozzle row direction;
Based on this measurement result and the amount of movement of the nozzle plate, a focusing coordinate acquisition step of acquiring position information of each nozzle hole and distance information of the focusing position of the image recognition means with respect to the inside of each nozzle hole;
An image recognition step for continuously recognizing a predetermined depth position inside each nozzle hole in the nozzle plate moving in the nozzle row direction based on the position information and the distance information;
A nozzle plate inspection method comprising: an inspection step of inspecting each nozzle hole for the presence or absence of foreign matter from the recognition result of the image recognition.   In the image recognition step, when the recognition result of each nozzle hole by the image recognition and the template of the nozzle hole stored in advance do not match, the image recognition means is moved up and down to obtain the recognition result and the template. The method for inspecting a nozzle plate according to claim 6, wherein the image recognition process is performed again after matching.

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