Droplet property measurement

Abstract

An inkjet printing system having a droplet measurement device is described herein. The droplet measurement device has a light source with a collimating optical system, an imaging device disposed along an optical path of the collimating optical system, and a droplet illumination region on the optical path of the collimating optical system, the droplet illumination region having a variable droplet illumination position, wherein the light source, the imaging device, or both are adjustable to place a focal plane of the imaging device at the droplet illumination position. The droplet measurement device is configured to receive at least a portion of a dispenser of the printing system within the droplet illumination region.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This patent application claims priority to U.S. Provisional Patent Application Serial No. 62 / 783,767 filed on December 21, 2018, U.S. Provisional Patent Application Serial No. 62 / 810,481 filed on February 26, 2019, and U.S. Non-Provisional Patent Application No. 16 / 719,666 filed on December 18, 2019, which are incorporated herein by reference. Technical Field

[0003] Embodiments of the present invention generally relate to inkjet printers. Specifically, methods and apparatus for monitoring and controlling printed materials during a deposition process are disclosed. Background Art

[0004] Inkjet printing is common, both in office and home printers, and in industrial-scale printers for making displays, printing large-scale writing materials, adding materials to products such as PCBs, and building biological products such as tissues. Most commercial and industrial inkjet printers, as well as some consumer printers, use piezoelectric dispensers to apply printing materials to substrates. Piezoelectric materials are arranged adjacent to printing material reservoirs. Applying voltage to piezoelectric materials can cause them to deform, thereby applying compression to the printing material reservoir, which is then constructed to eject printing materials when compression is applied.

[0005] Some inkjet printing applications rely on extremely high precision in the positioning of the print nozzle, the amount and type of print material ejected, and the speed and trajectory of the droplet ejection. When the nozzle fails to eject the print material at the correct volume, speed, and trajectory as required, printing failure will result, and time and money must be spent to correct the failure. Optical systems are typically used to monitor the droplet size and flight from the print nozzle to the substrate. Such systems typically rely on illuminating the droplet of print material to determine the characteristics of the droplet. The droplets are typically small, such as 10-15 μm in diameter, and the sharp focus of the captured image helps to accurately determine the droplet characteristics. In addition, it is most useful to capture the image when the droplet is close to the ejection nozzle. These considerations can constrain the geometry of the lighting device. Flexible droplet lighting hardware is needed in the art. Summary of the invention

[0006] Embodiments described herein provide a droplet measurement device comprising a light source having a collimating optical system; an imaging device disposed along the optical path of the collimating optical system; and a droplet illumination region in the optical path of the collimating optical system, the droplet illumination region having a variable droplet illumination position, wherein the light source, the imaging device, or both are adjustable to place a focal plane of the imaging device at the droplet illumination position.

[0007] Other embodiments described herein provide a printing system comprising a substrate support; and a printing assembly operably connected to the substrate support, the printing assembly comprising a printing support; a dispenser assembly movably coupled to the printing support; a droplet measuring device coupled to the printing support, the droplet measuring device having a housing; a light source disposed in the housing, the light source comprising a collimating optical system; a droplet illumination area having a varying droplet illumination position; and an imaging device disposed in the housing to receive radiation from the droplet illumination area, the light source, the droplet illumination area, and the imaging device defining a focal plane adjustable to the droplet illumination position.

[0008] Other embodiments described herein provide a method comprising placing a dispenser of an inkjet printer near an illumination zone of a droplet measurement device; emitting a collimated light beam from a light source through the illumination zone; aligning a nozzle of the dispenser with an optical path of the collimated light beam; ejecting a droplet from the nozzle into the illumination zone; illuminating the droplet at the illumination location using the collimated light beam to form a radiation signature of the droplet; receiving the radiation signature at an imaging device; and adjusting a focal plane of the imaging device to the illumination location. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] In order that the above-mentioned features of the present disclosure can be understood in detail, the present disclosure briefly summarized above can be described in more detail by reference to embodiments, some of which are illustrated in the accompanying drawings. However, it should be noted that the accompanying drawings only show exemplary embodiments and therefore should not be considered as limiting the scope thereof, and other equivalent embodiments may be allowed.

[0010] Figure 1 is a top view of a printing system according to one embodiment.

[0011] Figure 2A is a cross-sectional view of a droplet measurement device according to another embodiment.

[0012] Figure 2B yes Figure 2A Close-up cross-sectional view of the droplet illumination area of ​​the droplet measurement device.

[0013] Figure 3 is a cross-sectional view of a droplet measurement device according to another embodiment.

[0014] Figure 4 is a flow chart outlining a method according to another embodiment.

[0015] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures, and it is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.

[0016] Detailed description

[0017] A printing system is described herein having a drop measurement device with a flexible geometry for capturing droplets at different focal planes for various print jet designs.

[0018] Figure 1 1 is a three-dimensional top view of a printing system 100 according to one embodiment. The printing system 100 has a substrate support 102 mounted on a base 104. The base 104 includes one or more solid blocks that provide a stable foundation for the printing system 100. In some cases, the base 104 is one or more granite blocks. Using a solid, large object as a base can minimize unwanted vibration or other movement of the printing system 100.

[0019] The substrate support 102 includes a working portion 106, a first table portion 108, and a second table portion 110. The working portion 106 is disposed between the first table portion 108 and the second table portion 110. The working portion 106 is supported directly on the base 104, while each table portion 108 and 110 is supported by a base extension 112 attached to and extending laterally from the base 104. The base extension 112 can be made of any structurally strong material, such as steel. The stability of the base 104 minimizes uncontrolled movement of the substrate and / or other printer components at the location where the material is dispensed onto the substrate.

[0020] The substrate support 102, and in particular the working portion 106, is a table that supports the substrate in a printing position in the printing system 100. The substrate support 102 has a support surface 103 that provides low friction or frictionless support to accurately move and position the substrate to be printed. The table is rectangular, having a long dimension in a first direction 114 and a short dimension in a second direction 116 that is perpendicular to the first direction 114. During printing, the substrate moves along the first direction 114. The short dimension is similar to the largest dimension of the substrate in the second direction 116, which is the cross-scan direction. The long dimension can be up to about 10m, while the short dimension is typically 2-3m. A third direction 118 is perpendicular to both the first direction 114 and the second direction 116.

[0021] The printing system 100 has a printing assembly 120 juxtaposed with the working portion 106. The printing assembly 120 includes a dispenser support 122 and a dispenser assembly 124. The dispenser support 122 includes two brackets 126, one on either side of the working portion 106 and aligned in a cross-scan direction. The brackets 126 rise from the base 104 and can be attached or integrally formed with the base 104. The brackets 126 support rails 117 that extend from one bracket 126 to another bracket 126 across the working portion 106 in a second direction 116. Multiple brackets can be used on each side of the working portion 106 to support the rails 117, and multiple rails 117 can be used to support devices that scan across the working portion 106, such as imaging devices and drying devices.

[0022] The distributor assembly 124 is connected to the track 117 by a carriage 128, and the carriage 128 includes an actuator that moves the carriage 128 along the track 117 to position the distributor assembly 124 at a desired position along the second direction 116. During a print job, the substrate is moved by the distributor assembly 124 in the first direction 114 (sometimes referred to as the scan direction), and the distributor assembly 124 is positioned in the second direction 116 (sometimes referred to as the cross-scan direction) by the operation of the carriage 128 to deposit the material at a desired position on the substrate. The distributor housing 130 is coupled to the carriage 128. One or more distributors (not shown) can be disposed in the distributor housing 130 to distribute printing material to the working portion 106. When the substrate is moved by the distributor assembly 124, the distributor distributes the printing material to the substrate. Each distributor generally has a plurality of jet nozzles (not shown) at the jetting surface of the distributor facing the working portion 106.

[0023] A print job may include depositing droplets of printing material on a substrate in an extremely precise manner. Droplets of 10-15 μm in size are deposited at a target location on the substrate. The target location may be 15-20 μm in size. The droplets are deposited by ejecting droplets of the desired size from a jet nozzle at a certain time, speed and trajectory towards a droplet deposition location, which is a predetermined location above the substrate support, and the target location of the substrate will be positioned at this predetermined location when the droplet reaches the droplet deposition location. The size, jetting time, speed and trajectory of the droplet are determined to place the droplet at the droplet deposition location when the movement of the substrate brings the target location to the droplet deposition location. The extremely high precision of this process requires excellent control of the droplet size, jetting time, speed and trajectory of the jet nozzle.

[0024] To achieve this control of droplet characteristics, the output of the jetting nozzle is measured. The printing system 100 includes a droplet measurement device 132 located near one of the brackets 126. The droplet measurement device 132 is an optical system that detects the interaction of a specific configuration of electromagnetic radiation with droplets ejected from the dispenser in the dispenser housing 130 to determine the jetting characteristics of the dispenser - the size, velocity and trajectory of the droplets - as a function of the pulse input to the dispenser and the characteristics of the printed material. The droplet measurement device 132 can be mounted on the bracket 126, or as shown, can be supported on the base 104 near the bracket 126. The droplet measurement device 132 is supported beside the working portion 106 of the substrate support 102 to allow the dispenser assembly 124 to enter the droplet measurement device 132. The dispenser assembly 124 moves along the track 117 to the bracket 126 or its vicinity to engage with the droplet measurement device 132. Typically, the controller controls the positioning of the dispenser assembly 124 based on predetermined position data of the droplet measurement device 132 stored in the controller or accessible to the controller. If the ability to raise and lower the drop measurement device 132 is desired, an optional actuation platform 134 is shown here. This capability may be useful for moving the drop measurement device 132 away from the dispenser housing 130 or other device when not in use. The actuation platform 134 can also be used to precisely position the drop measurement device 132 relative to the dispenser housing 130 to obtain the best effect in recording drop characteristics.

[0025] Figure 2A FIG. 2 is a cross-sectional view of a drop measurement device 200 according to one embodiment. The drop measurement device 200 may be used as the drop measurement device 132 in the printing system 100 . Figure 2A The cross-sectional plane is perpendicular to Figure 1 The first direction 1 14 of the embodiment. The frame 202 holds the light source 206, the droplet illumination area 208 and the imaging device 210 in optical engagement. The light source 206 is a collimated light source having a light source 207 and a collimating optical system 209 optically coupled to the light emitter. The light source 206 emits collimated light toward the droplet illumination area 208. The dispenser housing 130 having a dispenser 216 is shown mounted in a suitable position in the dispenser tray 218 to engage the droplet measurement device 200. Droplets are ejected from an ejection nozzle (not shown) of an ejection surface 217 (which may be a surface of an ejection plate) of the dispenser 216 toward the droplet illumination area 208 and enter the container 214.

[0026] Collimated light is directed by the first guiding optics 222 and the second guiding optics 224 through the droplet measurement region 212 of the droplet illumination region 208 to interact with the droplets passing through the droplet illumination region 208. The optional alignment optics 220 align the collimated light with the first guiding optics 222. In this case, each of the first guiding optics 222 and the second guiding optics 224 is a prism, but other optical devices or combinations can be used as guiding optics. In this case, the alignment optics 220 is also a prism. The guiding optics allow the light source 207 and the imaging device 210 to have non-parallel optical axes, thereby reducing the footprint of the droplet measurement device 200. The guiding optics optically couple the light source 207 and the imaging device 210 along an optical path passing through the droplet illumination region 208.

[0027] After interacting with the droplet, the light is directed to the imaging device 210. The imaging device 210 captures an image of the light from interacting with the droplet to record data about the droplet. The imaging device 210 can be a camera, a CCD array, a photodiode array, or other imaging device. The imaging device is supported in a working position by a bracket 226. The bracket 226 is coupled to a linear positioner 228, which is coupled to a base 230 within the frame 202.

[0028] Figure 2B 2 is a close-up view of the droplet illumination area 208 to illustrate the operation of the droplet measurement device 200. The light source 206, the droplet illumination area 208, and the imaging device 210 are positioned along an optical path 250 of collimated light. In this case, the optical path 250 is not straight to allow the light source 206 and the imaging device 210 to be accommodated in a small footprint. The jet nozzles of the dispenser 216 eject droplets along a path that intersects the optical path 250 at the droplet illumination position. Here, four droplet illumination positions 252A, 252B, 252C, and 252D are shown, which correspond to four ejection nozzles in the ejection surface 217 of the dispenser 216. The droplet illumination positions can correspond to the positions of the ejection nozzles in the ejection surface 217. If the ejection surface 217 has five ejection nozzles arranged to eject droplets into the optical path, there will be five droplet illumination positions. Typically, the illumination position of the droplet will be defined by the intersection of the travel path from each ejection nozzle with the optical path 250. At each droplet illumination position 252A-D, the droplet may be illuminated by collimated light, resulting in an illumination feature propagating along optical path 250 to imaging device 210. The light is collimated to a spot size variation of less than about 1% per meter. Here, optical path 250 is approximately 0.25 meters long.

[0029] In order to image the droplet illumination and recover usable data regarding the droplet size, velocity, and trajectory, the imaging device 210 focuses light received from the droplet illumination region 208 along the optical path 250. Focusing the light positions the focal plane of the imaging device 210 at the droplet illumination location 252A, 252B, 252C, or 252D, depending on the location at which the droplet is to be ejected. Thus, the droplet measurement device 200 has an adjustable focal plane. Because the optics of the imaging device 210 have high resolution and / or optical power, the depth of focus or working range of the imaging device 210 is small. Therefore, the imaging device 210 can be moved relative to the frame 202. In alternative embodiments, adjusting the focal plane of the imaging device can include adjusting a focusing component of the imaging device, such as a lens, a reflector, or a prism.

[0030] Reference again Figure 2A , the linear positioner 228 is actuated to extend or retract, thereby moving the imaging device 210 toward or away from the illumination area 208. Moving the imaging device 210 changes the length of the optical path 250 and the focal length limit of the imaging device 210 so that the working range of the imaging device 210 includes the droplet illumination position 252A, 252B, 252C, or 252D of interest. Therefore, if a droplet is to be ejected from a nozzle aligned with the droplet illumination area 252A, the linear positioner 228 is actuated to position the imaging device 210 so that the working range of the imaging device includes the droplet illumination position 252A, and also includes positions 252B, 252C, and 252D.

[0031] The prisms 222 and 224 are located on either side of the droplet illumination area 208, and the container 214 is located between them. Therefore, the prisms 222 and 224 are located on either side of the container 214. The prisms 222 and 224 protrude upward above the upper portion of the container 214 so as to direct the light from the light source 206 along the light path 250 through the droplet illumination area 208. Here, the prisms 222 and 224 are triangular, each prism having a right-angle edge, and the three faces are all rectangular. The orientation of the prisms 222 and 224 is such that the face 227 adjacent to the right-angle edge faces the droplet illumination area 208. In this orientation, the edge 229 adjacent to the surface 227 extends beyond the light path 250 toward the dispenser housing 130. The upward extension of the prisms 222 and 224 positions the optical pathway 250 in the illumination zone at a distance from the container 214, which allows the dispenser housing 130 and the optical pathway 250 to be positioned together to be close to the flex plate 260 of the dispenser housing 130, thereby enabling the droplet measurement device 200 to capture an image of the droplet before the droplet characteristics change as the droplet travels through the atmosphere.

[0032] The flexure plate 260 has a plurality of channels 262. In this view, the channels 262 extend to Figure 2B(and 2A). The channels 262 are generally located around the distributor 216 and are spaced apart by a certain distance D, which is generally similar to the distance E between the two prisms 222 and 224. Specifically, the distance E is the distance between the upper ends of the prisms 222 and 224. The channels 262 allow the distributor housing 130 to be properly positioned to align the upward protrusions of the prisms 222 and 224 with the channels 262, by providing additional space to accommodate the upward protrusions of the prisms 222 and 224 to more closely approach the optical path 250. The channels 262 are generally located between the distributors 216, so that a portion of any distributor 216 can be positioned between the prisms 222 and 224 by placing the upward protrusions of the prisms 222 and 224 in the channels 262 on either side of the desired distributor 216. In this way, the flexure plate 260 can be positioned as close to the optical path 250 as possible to obtain the best imaging effect.

[0033] In addition, the optical path 250 is configured so that the optical path is as close as possible to the dispenser 216 in the droplet illumination area 208. Therefore, the optical path 250 is as close as possible to the face 227 facing the entire droplet illumination area 208, so that the optical path through the prisms 222 and 224 is near the top of the upward projection of the prisms. This arrangement provides a tighter engagement of the ejection surface of the dispenser 216 and the optical path 250.

[0034] Figure 3 FIG. 3 is a cross-sectional view of a droplet measurement device 300 according to another embodiment. The droplet measurement device 300 is similar to the Figure 2A and 2B The droplet measurement device 300 is similar to the droplet measurement device 200, and like elements are marked with like reference numerals. The main difference between the droplet measurement device 300 and the droplet measurement device 200 is that the light source 206 and the imaging device 210 are aligned. The container 214 is disposed in a bracket 302, and the bracket 302 extends outward to support the light source 206 and the imaging device 210 in a lateral position relative to the droplet illumination area 208. The light source 206 is located on one side of the droplet illumination area 208, and the imaging device 210 is positioned opposite the light source 206, wherein the droplet illumination area 208 is located between the light source 206 and the imaging device 210. The optical axes of the light source 206 and the imaging device 210 are aligned here along an axis 310 extending directly from the light source 206 through the droplet illumination area 208 to the imaging device 210.

[0035] In this case, the imaging device 210 is coupled to a linear positioner 304 supported on a support 302. The linear positioner 304 moves the imaging device 210 in a lateral direction toward or away from the droplet illumination region 208, as indicated by arrow 308, thereby moving the focal plane of the imaging device to coincide with one of the droplet illumination locations 252 where a droplet is to be measured.

[0036] Aligning the light source 206 and the imaging device 210 may present challenges in obtaining high resolution images of some droplet locations. Figure 3 In the embodiment, the printing assembly 312 has three dispensers, a first dispenser 320, a second dispenser 322, and a third dispenser 324, connected to a frame 314, and the frame 314 can be similar to Figure 1 1 and 2. The dispenser housing 320, 322, and 324 are part of a dispenser housing of the housing 130 of the printing system. Three dispensers 320, 322, and 324 are aligned along the optical axis 310 at intervals set by the operating specifications of the printing system. The dispensers are shown located between the light source 206 and the imaging device 210 so that an image of the droplet 306 is obtained immediately upon exiting the dispenser before any characteristics of the droplet are significantly changed. Positioning the dispensers between the light source 206 and the imaging device 210 limits the degree to which the imaging device can be positioned close to some droplet illumination locations, such as those farthest from the imaging device 210 and closest to the light source 206. In some cases, it may be difficult to coordinate the desired image resolution and working range by simply moving the imaging device 210.

[0037] To expand the working range of the imaging device 210, an adjustable lens 330 may be coupled to the imaging device 210. The adjustable lens may extend the working range over which the imaging device 210 may deliver high-resolution images, so that the imaging device 210 may capture high-resolution images of the closest droplet illumination position of the first dispenser 320 and the farthest droplet illumination position of the third dispenser 324.

[0038] like Figure 3 As shown, in order to position the third dispenser 324 over the container 214 to deliver the droplets, the dispenser assembly must be moved to the right by a distance A that is greater than the gap B between the dispenser assembly 312 and the imaging device 210. Therefore, the imaging device 210 must increase the distance between the imaging device 210 and the droplet illumination area 208 by actuating the linear positioner 304 to move to the right. If the imaging device 210 does not have sufficient working range to deliver high resolution images at the increased distance without the enhancement of the adjustable lens, the adjustable lens 330 can be used to increase the working range of the imaging device 210. In this way, suitable images of the droplets ejected from all three dispensers 320, 322, and 324 can be captured. It should be noted that in any of the embodiments described herein, an adjustable lens such as the adjustable lens 330 can be used in conjunction with the linear positioner 304 or 228, or in place of the linear positioner.

[0039] In some ways, Figure 3 The droplet measuring device 300 has a Figure 2A and 2BThe drop measurement device 200 is a simpler configuration. However, the drop measurement device 200 engages the dispenser 216 and the optical path 250 in a manner that minimizes the insertion of the dispenser 216 into the imaging device. In the device 300, the entire dispenser housing 130 is inserted between the light source 206 and the imaging device 210. With the drop measurement device 200, only the end of one dispenser 216 is inserted between the upper tips of the prisms 222 and 224, where less vertical movement is required. The most useful design can be customized for each application.

[0040] Figure 4 4 is a flow chart outlining a method 400 according to another embodiment. Method 400 is a method for obtaining a measurement of a characteristic of a droplet ejected from a printing material dispenser of a printing system such as an inkjet printer. Method 400 may be practiced using the apparatus described herein. At 402, a printing material dispenser is positioned adjacent to a droplet measurement device of the printing system. If multiple dispensers are used, the dispensers may be housed in a dispenser assembly. The droplet measurement device is typically located outside of a substrate processing area of ​​the printing system so that operations for performing droplet measurement may be performed without affecting the substrate processing area or any substrate that may be located thereon.

[0041] The droplet measurement device generally has a light source for illuminating a droplet in a droplet illumination region and an imaging device for receiving light from the droplet illumination region after the light and the droplet interact. The light source includes a collimating optical device, and the droplet measurement device includes an optical assembly to direct light from the light source to the imaging device on an optical path through the droplet illumination region.

[0042] The imaging device has a variable focal plane. In one case, the imaging device is disposed on a linear positioner that can move the imaging device to position the focal plane of the imaging device at a droplet illumination position in the droplet illumination zone so that the image of the droplet is sharply focused. The focal plane of the imaging device is variable because droplets can be dispensed from the nozzle at various positions on the jetting face of the dispenser, and where multiple dispensers are used, the dispenser assembly may need to be moved to bring the target dispenser within the working range of the imaging device. In another case, the imaging device may have an adjustable lens that can dynamically adjust the focal length to position the focal plane of the imaging device at different droplet illumination positions within the droplet illumination zone. If desired, the linear positioner may also be combined with the adjustable lens to further expand the working range of the imaging device.

[0043] The droplet illumination area is defined by the jetting face of the dispenser and the droplet container located in the droplet measurement device. The jetting face of the dispenser can have a plurality of jetting nozzles distributed across the jetting face. The container is typically sized to accommodate the area coverage of all nozzles of the dispenser so that all nozzles of the dispenser can be fired to measure droplet characteristics without having to move the dispenser. If multiple dispensers are used in the dispenser assembly, the dispenser assembly can be moved to position each dispenser in turn in the droplet illumination area.

[0044] At 404, the printing material dispenser is positioned at a test position. The test position is typically a position in which the jetting surface of the dispenser is located at a minimum distance from the optical path of the light used to illuminate the droplets. In some cases, the minimum distance is less than 2 mm, for example, less than 1 mm. If optical components are used to allow light to enter the droplet illumination area, the jetting surface of the dispenser or the frame or jetting surface of the dispenser assembly can be shaped to adapt to positioning the dispenser or the dispenser assembly at the test position. For example, if prisms are used to guide light through the droplet illumination area, the dispenser can be partially located between the prisms in order to position the dispenser at the test position. In this case, if a portion of the prism extends above the boundary of the optical path, that is, beyond the spatial range of the light field used to illuminate the droplets, the jetting surface of the dispenser or the dispenser assembly can be provided with a structure to accommodate the prism so that the jetting surface can be positioned at the test position. In one example, the dispenser assembly has a flat nozzle plate, the jetting surfaces of a plurality of dispensers are arranged on the nozzle plate, and the nozzle plate has a recess to position the tops of two prisms, which are used to guide light through the droplet illumination area. To position the dispenser in the test position, the top of the prism is inserted into the notch so that the ejection surface of one dispenser is positioned at the minimum distance from the optical path.

[0045] At 406, one or more droplets are ejected from the dispenser into the droplet illumination area. The droplets enter the container through the droplet illumination area. If the size of the container is suitable for accommodating the entire area of ​​the injection nozzles in the injection surface of the dispenser, droplets can be ejected from each nozzle of the dispenser into the container without moving the dispenser. In this case, due to the area distribution of the injection nozzles across the injection surface of the dispenser, the droplets may arrive at the droplet illumination area at different droplet illumination positions. At this time, the position of the nozzle can be provided to a controller that is connected to the dispenser assembly and the imaging device to position the focal plane of the imaging device at the droplet illumination position for imaging the droplets. As the droplet illumination position changes due to the ejection of droplets from different nozzles, the focal plane of the imaging device moves to image each droplet.

[0046] At step 408, when the droplet passes through the droplet illumination zone, a light source is activated to provide illumination in the droplet illumination zone. The light and the droplet interact to generate a characteristic light field, which is propagated to the imaging device.

[0047] At 410, an imaging device captures an image of the characteristic light field, which can then be analyzed to determine droplet characteristics, such as volume. In some cases, a light source is pulsed to produce multiple images of a droplet as it passes through a droplet illumination zone. The multiple images can be analyzed to determine the velocity and trajectory of the droplet. The volume, jet velocity, and trajectory can be used to determine the performance of each nozzle of the dispenser. Because the focal plane of the imaging device can be changed to accommodate all nozzles of the dispenser, the entire dispenser can be tested without repositioning the dispenser.

[0048] While the foregoing is directed to embodiments of the present invention, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope of the disclosure is determined by the claims that follow.

Claims

1. A droplet measuring device for an inkjet printer, comprising: case; A light source disposed in the housing and having a collimating optical system; a high-resolution imaging device disposed in the housing and arranged along the optical path of the light beam from the collimating optical system; a droplet illumination region in the optical path from the collimating optical system to a high-resolution imaging device, the droplet illumination region having a varying droplet illumination position, wherein the high-resolution imaging device is adjustable or both the light source and the high-resolution imaging device are adjustable to place a focal plane of the high-resolution imaging device at the droplet illumination position; a linear positioner coupled to the high-resolution imaging device to move the high-resolution imaging device toward or away from the droplet illumination region to position a focal plane of the high-resolution imaging device at a droplet illumination position in the droplet illumination region; and a pair of prisms on opposite sides of the droplet illumination region, the pair of prisms defining a portion of the optical path extending through the droplet illumination region, the prisms optically coupling a light source and a high-resolution imaging device along the optical path through the droplet illumination region; The inkjet printer comprises a distributor assembly, the distributor assembly comprises one or more distributors, the distance between the prisms is greater than the size of the one or more distributors, the droplet illumination area is defined by a jetting surface of the distributor and a droplet container located in a droplet measurement device, the distributor comprises a plurality of jetting nozzles distributed on the jetting surface; and The droplet illumination position varies along the line between the prisms, and the droplet illumination position is defined by the intersection of the travel path from each ejection nozzle and the optical path. The droplet illumination position corresponds to the position of the ejection nozzle in the ejection surface, and as the droplet illumination position changes due to the ejection of droplets from different nozzles, the focal plane of the imaging device moves to image each droplet.

2. The droplet measurement device of claim 1, further comprising an adjustable lens optically coupled to the high-resolution imaging device.

3. The droplet measuring device according to claim 1, wherein: The optical path includes a first portion between the collimating optical system and the droplet illumination area, and a second portion between the droplet illumination area and the high-resolution imaging device, and the first portion is not parallel to the second portion.

4. A printing system, comprising: a substrate support; and A printing assembly operably coupled to the substrate support, the printing assembly comprising: Print support parts; a dispenser assembly movably coupled to the print support; and A droplet measurement device coupled to the print support, the droplet measurement device comprising: case; A light source disposed in the housing, the light source comprising a collimating optical system; a droplet illumination zone with varying droplet illumination positions; a high-resolution imaging device disposed in the housing to receive radiation from the droplet illumination region, the light source, the droplet illumination region, and the high-resolution imaging device defining a focal plane adjustable to the droplet illumination location; a linear positioner coupled to the high-resolution imaging device to move the high-resolution imaging device toward or away from the droplet illumination region to position a focal plane of the high-resolution imaging device at a droplet illumination position in the droplet illumination region; and a pair of prisms on opposite sides of the droplet illumination region, the pair of prisms defining a portion of an optical path extending through the droplet illumination region, the prisms optically coupling a light source and the high-resolution imaging device along the optical path through the droplet illumination region; wherein the distributor assembly includes one or more distributors, and the distance between the prisms is greater than the size of the one or more distributors, the droplet illumination area is defined by the jetting surface of the distributor and the droplet container located in the droplet measurement device, and the distributor includes a plurality of jetting nozzles distributed on the jetting surface; and The droplet illumination position varies along the line between the prisms, and the droplet illumination position is defined by the intersection of the travel path from each ejection nozzle and the optical path. The droplet illumination position corresponds to the position of the ejection nozzle in the ejection surface, and as the droplet illumination position changes due to the ejection of droplets from different nozzles, the focal plane of the imaging device moves to image each droplet.

5. The printing system according to claim 4, wherein: The light source, the droplet illumination area, and the high-resolution imaging device define an optical path, and the printing system further includes an adjustable lens disposed in the optical path between the droplet illumination area and the high-resolution imaging device.

6. The printing system according to claim 4, wherein: The dispenser assembly is movable to position the dispenser within the droplet illumination zone.

7. The printing system according to claim 4, wherein: The droplet measurement device also includes a container adjacent to the droplet illumination area.

8. The printing system according to claim 4, wherein: The distributor assembly also includes a nozzle plate, and the nozzle plate has recesses having a spacing that matches the spacing of the prisms.

9. A method for measuring droplets using the droplet measuring device of an inkjet printer according to any one of claims 1 to 3, comprising: positioning a dispenser of a dispenser assembly of an inkjet printer proximate a droplet illumination region of a droplet measurement device; A collimated light beam is emitted from a light source disposed in the housing to pass through the droplet illumination area; aligning a plurality of nozzles of a distributor of the distributor assembly with an optical path of the collimated light beam; ejecting droplets from a nozzle into a droplet illumination area; illuminating the droplet at a droplet illumination position using a collimated light beam to form a radiation signature of the droplet; receiving a radiation signature at a high-resolution imaging device disposed in the housing; and The focal plane of the high-resolution imaging device is adjusted to the droplet illumination position, wherein adjusting the focal plane of the high-resolution imaging device includes moving the high-resolution imaging device.

10. The method according to claim 9, wherein: Adjusting the focal plane of the high resolution imaging device further includes adjusting a focus component of the high resolution imaging device.

11. The method of claim 9, further comprising positioning at least a portion of the dispenser within the droplet illumination zone.

12. The method of claim 11, wherein positioning at least a portion of the dispenser within the droplet illumination zone comprises positioning the portion of the dispenser between a pair of prisms on opposite sides of the droplet illumination zone.

Images