Precision position alignment, calibration, and measurement in printing and manufacturing systems

Abstract

To provide a high precision measurement system for rapid, accurate determination of height of a deposition source relative to a deposition target substrate.SOLUTION: In one embodiment, each of two transport paths of an industrial printer mounts respective cameras 253, 263 and a high precision sensor. The cameras are used to achieve registration between split transport axes, and the positions of the high precision sensors are each precisely determined in terms of xy position. One of the high precision sensors is used to measure height of the deposition source, while another measures height of a target substrate 239. A relative z position between these sensors is identified to provide for precise z-axis coordinate display of both the deposition source and the target substrate. Disclosed embodiments permit dynamic, real-time, high precision height measurement to micron or submicron accuracy.SELECTED DRAWING: Figure 2B

Description

[Technical Field]

[0001] This application claims priority to U.S. Patent Application No. 15 / 851,419, filed December 21, 2017, on behalf of David C. Darrow, first inventor, for "Precision Alignment, Calibration, and Measurement in Printing and Manufacturing Systems," and this application also claims priority to U.S. Provisional Patent Application No. 62 / 459,402, filed February 15, 2017, on behalf of David C. Darrow, first inventor, for "Precision Alignment, Calibration, and Measurement in Printing and Manufacturing Systems," as well as the previously referenced U.S. patent application. Both of these prior applications are incorporated herein by reference. This application also incorporates by reference the following documents: (1) U.S. Patent No. 9,352,561 (USSN 14 / 340403), filed July 24, 2014, on behalf of first inventor Nahid Harjee, for "Techniques for Measuring and Controlling Printed Ink Droplets to Deposit Fluids Within Precise Tolerances," (2) U.S. Patent Application Publication No. 20150298153 (USSN 14 / 788609), filed June 30, 2015, on behalf of first inventor Michael Baker, for "Techniques for Aligning and Printing Permanent Layers with Improved Speed ​​and Accuracy," and (3) U.S. Patent No. 8,995,022, filed August 12, 2014, on behalf of first inventor Eliyahu Vronsky, for "Production of Ink-Based Layers Using Halftoning to Control Thickness." [Background technology]

[0002] Printers can be used in a wide range of industrial manufacturing processes in which a liquid is printed onto a substrate and then cured, dried, or otherwise processed to convert this “ink” into a finished layer of a specifically intended thickness and further impart structural, electrical, optical, or other properties to the resulting product. Some of these manufacturing processes have very precise requirements, requiring, for example, micron-order or less precision in the location of the deposited material. As an example, a “room-sized” industrial inkjet printer can be used to print droplets of liquid over a meter in length and width onto a substrate, depositing a specific layer of millions of individual “pixels” that form part of a high-definition (HD) smartphone display. Each layer produced in this way can have strict volume specifications (e.g., 50 picoliters per pixel), and failure to adhere closely can result in defects in the finished product. This process can also be used to deposit encapsulation or other macroscale layers covering many such tiny electronic or optical elements, which also require highly consistent thickness (and control of volume per unit area). Depending on the particular product being manufactured, a single large substrate can be manufactured to form one or many products, for example, a single large substrate can be used to create one large electronic display (e.g., a giant HD television screen) or to create many smaller products (e.g., "100" smartphone HD displays) that are aligned and cut onto the substrate during manufacturing.

[0003] To provide the high accuracy required for many designs, printers and other types of precision manufacturing equipment are subject to rigorous calibration and alignment procedures designed to ensure that material deposition occurs as intended. As an example, a multi-axis printer typically features a “y-axis” transport system that moves the substrate and an “x-axis” transport system that moves the printer head (or other assemblies, e.g., one or more inspection tools, UV lamps used for curing, or other types of items). Typically, these various transport paths are carefully calibrated manually with respect to the printer's frame of reference, often based on the subjective interpretation of a human operator. As each substrate is loaded, it also typically must be individually aligned with the printer's positional frame of reference. Over time, the transport paths and positional frame of reference typically must be recalibrated and realigned, for example, due to various sources of drift. Typically, the manufacturing equipment must be taken off-line and physically invaded for this to occur, again requiring elaborate and typically sophisticated manual procedures. While the split-axis printer example is merely illustrative, it does demonstrate some of the difficulties involved in achieving precision in the manufacture of microstructured products. Downtime and required manual steps limit product throughput but are generally necessary; in other words, even a micron-order deviation from the intended position for manufacture can result in an inoperable or poor quality final product.

[0004] Depending on the application, accurately measuring and calibrating additional dimensions, such as the height of the deposition source above the substrate (e.g., typically the “z-axis”), can be very important. Manufacturing equipment of the type described above is operated to perform deposition as quickly as possible (while maintaining accuracy). In the case of a split-axis printer, deposition typically occurs “on the fly”—in other words, the printhead and substrate move relative to each other while ink droplets are being ejected—and height errors result in positional deviations in the droplet landing locations. Height errors are more than trivial; for example, some industrial printing systems can be characterized by a dozen or more printheads collectively supporting thousands of nozzles, each producing picoliter-scale droplets intended to have very precise landing locations. Considering that each printhead may have nozzle ejection plates at slightly different heights or plateau positions, variability in nozzle z-height can prevent precise control over droplet landing location; for example, in such systems, errors in the height distance of each nozzle often result in droplet landing location deviations that are 20% or more of the height distance of the droplets produced from that nozzle.

[0005] What is needed are techniques for improving the calibration capabilities of manufacturing systems. Ideally, such techniques would facilitate more accurate calibration, thereby providing these systems with extremely high accuracy. Ideally, these techniques would also be performed more quickly or fully automated, significantly reducing the time and effort required for calibration. In industrial printing systems, these types of improvements improve the uptime of the manufacturing system, thereby increasing throughput and reducing overall manufacturing costs. The present invention addresses these needs and provides further related advantages. [Brief explanation of the drawings]

[0006] [Figure 1A]1A illustrates an assembly-line style manufacturing process in which a series of substrates 105 have one or more layers of material deposited thereon by deposition equipment 103 to form precision electrical structures. While only one set of deposition equipment 103 is shown, in practice there may be many (e.g., to perform other processes or deposit other types of materials, structures, or films earlier or later in the process). Each completed substrate (such as substrate 107) can be used to form a portion of one or more electronic products (such as, by way of example and not limitation, a cell phone 109, an HDTV 111, a solar panel 113, or part of another structure). [Figure 1B] Figure 1B is a plan schematic diagram of one layout or configuration of a deposition apparatus that may be used as the deposition apparatus from Figure 1A. Printing module 125 is used to deposit a liquid (i.e., "ink") that, unlike graphics ink, is processed (e.g., by processing module 127) to form a thin film that becomes one of the layers that make up the precision electronic structure referenced with respect to Figure 1A. [Figure 1C] Figure 1C is a plan view illustrating the basic operation of printer 151 within the print module from Figure 1B. This printer is illustrative of a "split-axis" mechanical system. As shown, a first transport system (e.g., "gripper" system 159) transports substrate 157 in a "y-axis" direction indicated by a first double arrow 161, while a second transport system transports printhead 165 in an "x-axis" direction indicated by a second double arrow 169. [Figure 1D] 1D shows exemplary substrate 181 and the underlying fabrication of four electronic products 183 (not individually visible), each having micron or smaller scale electrical, optical, or other structures. The substrate is moved back and forth along its long axis while print head 191 is moved between such "scans" (i.e., as indicated by arrow 195) to print "swaths" of ink across the surface of exemplary substrate 181. [Figure 2A] FIG. 2A illustrates one embodiment of mechanisms and techniques used to provide precision positioning in a split-axis system, such as a split-axis printer. [Figure 2B] FIG. 2B shows another embodiment of the mechanisms and techniques used to provide precision positioning in a split axis system. [Figure 3A] FIG. 3A is a flow chart illustrating a technique for alignment and calibration in a manufacturing tool. [Figure 3B] FIG. 3B is a flow chart illustrating a technique for alignment and calibration in a split-axis printer. [Figure 4A] FIG. 4A is a flow chart 401 illustrating the operation of an inkjet printer to deposit materials that form layers of an electronic product. [Figure 4B] FIG. 4B illustrates one embodiment of mechanical and electromechanical elements used to provide improved precision position calibration and alignment in a split-axis system. [Figure 4C] FIG. 4C is a flow chart illustrating a technique that may be used in conjunction with the elements shown in FIG. 4B to provide automatic and / or dynamic positioning in a split shaft manufacturing and / or printing system. [Figure 5A] FIG. 5A is a perspective view of one embodiment of the gripper system and the support table (or chuck) on which the grippers rest. [Figure 5B] FIG. 5B is a perspective view of a camera assembly used in conjunction with a printhead assembly. [Figure 5C] FIG. 5C is an enlarged perspective view of a reticle used by the camera of the assembly from FIGS. 5A and 5B. [Figure 5D] FIG. 5D is an enlarged perspective view of a calibration standard or "gauge block" used in laser height measurement in one embodiment. [Figure 5E] FIG. 5E is an enlarged perspective view of an alignment plate or target that is attached to the gripper system or printhead assembly.

[0007] The subject matter defined by the recited claims will be better understood by reference to the following detailed description, which should be read in conjunction with the accompanying drawings. The description of one or more specific embodiments set forth below to enable construction and use of various implementations of the claimed techniques is not intended to limit the recited claims, but rather to illustrate their application. Without limiting the foregoing, this disclosure provides several different examples of techniques for determining the position, and for calibrating and aligning position sensing subsystems used in precision manufacturing. Such techniques can be employed in the automated production of thin films for one or more products on a substrate as part of an integrated, repeatable printing process. The various techniques can be embodied as software that executes these techniques; in the form of a computer, printer, or other device or element thereof that executes such software; in the form of a manufacturing apparatus; in the form of an industrial printing and / or manufacturing system (or element of such a system); or in the form of an electronic or other device (e.g., having one or more layers produced according to the described techniques) that is manufactured as a result of using these techniques. While specific examples are presented, the principles described herein may also be applied to other methods, apparatus, and systems. DETAILED DESCRIPTION OF THE INVENTION

[0008] A. Introduction The present disclosure provides improved techniques for calibrating and aligning elements of manufacturing equipment and / or printers, for precise positional measurement of one or more dimensions in such equipment or printers, and for the associated manufacturing of one or more layers of electronic products. More specifically, the apparatus, methods, and systems disclosed herein provide improved accuracy and speed in calibrating and aligning positional systems in manufacturing systems and / or printers, thereby facilitating micron-scale or greater precision in the deposition or processing of structures in manufactured products. The techniques disclosed herein result in much faster, highly automated, and repeatable calibration and alignment processes, thereby reducing system downtime and significantly improving manufacturing throughput. In one embodiment, these techniques provide an improved, highly accurate, and dynamic means of measuring the exact height (e.g., "z-axis" height) of a deposition source above a substrate, thereby further improving the positional accuracy of deposited material. By providing such accuracy, the techniques disclosed herein enable smaller, denser, and more reliable equipment, thereby further promoting the trend toward smaller, more reliable, and more fully featured electronic products. The techniques of this disclosure also provide further related advantages.

[0009] In one embodiment, the disclosed techniques are presented as an improved method for aligning a split-axis transport system. Imaging systems or other sensors mounted on each transport path are aligned with one another (and / or with a common reference frame, such as a fabrication chuck), and a position feedback system is used for each transport path to provide precise positional accuracy when driving the system, enabling micron or finer positional discrimination. The disclosed techniques also have the advantage of additionally facilitating micron or finer height determination (e.g., z-axis determination) between the deposition substrate and the deposition material source, further improving positional accuracy.

[0010] In a second embodiment, the disclosed techniques provide an accurate "z-axis" height calibration and / or position determination system that can be used without requiring manual intervention in a manufacturing apparatus. Such a system additionally uses "z-axis" sensors above and below the deposition plate to identify a common frame of reference and accurately measure the absolute position of the deposition source above the substrate. In one embodiment, a first sensor above the substrate measures the absolute height of the sensor relative to the substrate, and a second sensor below the substrate is used to measure the difference in height between the first sensor and the deposition source (e.g., one or more printheads in a printer). These techniques can be automated and can be used for a wide variety of purposes, such as adjusting printhead level and / or height to eliminate potential sources of error or otherwise adjusting printing or system parameters.

[0011] Elements of these various techniques can be combined or permuted as desired.

[0012] It should be noted that in printing systems, especially those featuring interchangeable printheads and / or multiple printheads, determining height can be non-trivial. That is, in precision manufacturing systems, the height between the nozzle orifice (e.g., printhead ejection plate) and the substrate surface can vary by tens of microns or potentially more due to a variety of factors. Because droplet ejection is typically performed using relative motion between the printhead and the substrate, this variation can cause errors in droplet landing locations of tens of microns or more, undermining desired positional accuracy. One notable advantage of some of the techniques provided herein is that they enable much more accurate and rapid determination of nozzle height relative to the substrate surface, thereby correcting this error and enabling much more accurate droplet placement (thereby enhancing the manufacturing advantages discussed above). It should be noted that in such systems, understanding height and its variations allows a number of techniques to mitigate the error, such as manually or automatically adjusting or leveling the printhead height. Additionally, in some embodiments, errors can be compensated for in software by adjusting pre-planned printing parameters such as nozzle timing, drop velocity, drop waveform, and which of the many nozzles on the printhead is used to print each drop. Disclosed herein are techniques for mitigating nozzle position relative to the substrate, nozzle height error, substrate position error, scale error, product distortion error (shear), and the like, based on height and / or position understanding provided using the disclosed alignment, calibration, and height measurement techniques. The disclosed techniques are particularly useful in industrial manufacturing and / or printing applications where having fine particle positional accuracy at the microscopic level (e.g., down to 10 micron or finer resolution) is important to enable precise shaping and / or deposition of deposited material.

[0013] In one embodiment, at least one optical means is used to align and calibrate at least two different transport path directions to provide micron- or near-resolution x,y positional accuracy relative to the substrate and / or fabrication chuck. Such means may include, for example, one or more cameras that generate high-resolution digital images that are used to calibrate each transport path to a common reference point. Additionally, a position feedback system (imaging or non-imaging) is also used to enable transport path drive corrections in each transport axis direction to provide micron- or near-resolution positional accuracy across each transport path direction. (For example, in a split-axis system such as the exemplary printing system described below, the two transport paths are optically aligned relative to an origin, and a position feedback system is used for each transport path to ensure accurate transport path advancement.) A second means is then additionally used for z-axis calibration and position detection to determine any positional offsets relative to the x,y position after calibration of the second such means, allowing for determination of the z-height at any point relative to the fabrication chuck for the substrate. In one embodiment, because the deposition source may be at a different height (or misaligned) relative to the second means, the height is obtained by appropriate processing, such as (a) measuring the height difference with a first z-axis measurement system above the manufacturing surface, (b) using a second z-axis measurement system below the manufacturing surface to measure any height difference between the first z-axis measurement system and the source of deposition material (e.g., a print head or a specific print head nozzle), and (c) calibrating the first z-axis height-determining system to a known reference coordinate system, i.e., “zeroing.” As implied, this functionality, and the ability to remeasure height non-invasively during system operation, can be useful for providing dynamic height measurement with far-reaching benefits. For example, when replacing a print head or other manufacturing tool, the deposition source height can be immediately, automatically, and dynamically remeasured, thereby substantially improving system uptime.The fact that these measurements can be automatically linked to an accurate coordinate system also reduces errors resulting from the subjectivity of human operation, thereby providing much more accurate results.

[0014] Accurate knowledge of the height between the deposition source and the substrate surface can be used to correct the deposition location with fine precision. As mentioned above, various error / variation mitigation strategies include changing the height, alignment, or level of the source (e.g., print head), changing the height or position of the substrate, changing the source drive signal (e.g., nozzle drive signal) to change the ejection rate (i.e., thereby correcting the landing location), changing the ejection time (i.e., thereby correcting the landing location to offset the error), changing which source is used for deposition (e.g., using a different nozzle to provide a displacement landing location closer to the desired location), and / or potentially changing other deposition and / or machine parameters, whether in software or otherwise.

[0015] One example of a manufacturing system that would benefit from the disclosed technology is an industrial manufacturing system that relies on inkjet printers to deposit droplets of liquid onto a substrate, for example, to deposit organic materials that cannot be easily deposited by other manufacturing processes. Droplets ejected in parallel from literally thousands of nozzles (from one of many printheads) land on the substrate and coalesce to form a continuous liquid coat or film. However, liquids have viscosities that can cause local variations in coating thickness depending on droplet density and / or other forms of volume control (see the patents and publications incorporated by reference above). Films can be large relative to electronic microstructures (e.g., can provide encapsulation, barrier, smoothing, dielectric, or other layers across multiple such microstructures) or can provide a "global" liquid coating of an area that may be included in a fluid dam, with the same layer of many such structures being fabricated simultaneously, such as to form the layers of a single pixel or light-emitting structure. For example, the manufacturing system described above can be used to print the same organic light-emitting layer for each of the millions of pixels that make up an HDTV in a single deposition process; in such a manufacturing process, there are millions of corresponding microscopic wells, and it is typically desired to deposit precise amounts of liquid that fit exactly into these wells. Whatever the layer being manufactured, the successive liquid coats are printed and stabilized, then cured, dried, hardened, solidified, stabilized, or otherwise processed to convert the deposited liquid coat into a permanent or semi-permanent form (e.g., a processed layer). Given the precision required to deposit precise amounts of ink on a microscopic scale, or otherwise achieve a uniform layer or specific edge shape, the disclosed alignment, calibration, and measurement techniques provide powerful tools for facilitating very precise droplet placement and otherwise providing extremely fine deposition control. These and other examples are further described below.

[0016] Before proceeding further, it is useful to first introduce some terminology used herein.

[0017] Specifically, various references are made in this disclosure to “ink.” Unlike colored liquids used in graphics applications, which are generally absorbed into a support medium and convey images through color (hue) and brightness, the “ink” generally deposited by printers described in this disclosure typically does not possess any significant color or image properties of its own. Instead, the liquid, once deposited and processed, carries a material that provides an intended layer thickness and structural elements that provide desired structural, optical, electrical, and / or other properties. While theoretically, many materials can be deposited using this process, in some anticipated applications, the “ink” is essentially a liquid monomer that is converted into a polymer (i.e., a plastic with desired conductance, optical, or other properties) after deposition. In one particular application, where the deposited layer forms part of an organic light-emitting diode (OLED) display, the deposited layer can contribute color and image through electromagnetic actuation, but it is important to note that the liquid itself is not deposited for the purpose of transferring the liquid's inherent color to a substrate as part of a defined image, but rather is used to build a structure. In typical applications, the liquid is deposited in the form of individual droplets that spread over a limited area and coalesce to provide a "total" coverage (i.e., the coverage is typically free of holes or gaps) at least within the boundaries of the fluid well.

[0018] Specifically, contemplated implementations include devices having instructions stored on a non-transitory, machine-readable medium. Such instruction logic is written or designed in a manner that, when ultimately executed, causes one or more general-purpose machines (e.g., processors, computers, or other machines) to have a particular structure (architectural features) that necessarily performs the stated tasks of input terms in accordance with the instructions to perform particular operations or otherwise behave as special-purpose machines configured to generate particular outputs. For example, the techniques described herein may be embodied as control software stored on a non-transitory, machine-readable medium that, when executed, causes one or more processors and / or other equipment to perform the calibration, alignment, and position-determination functions described herein. As used herein, "non-transitory" machine-readable or processor-accessible "medium" or "storage" means any tangible (i.e., physical) storage medium, regardless of the technology used to store data on the medium, including, without limitation, random access memory, hard disk memory, optical memory, floppy disks or CDs, server storage, volatile memory, nonvolatile memory, internal computer memory, removable storage, and other tangible mechanisms from which instructions can be subsequently retrieved by a machine. The medium or storage can be in a stand-alone form (e.g., a program disk or solid-state device) or can be embodied as part of a larger mechanism, such as a laptop computer, portable device, server, network, printer, or other set of one or more devices. The instructions can be implemented in different formats, such as metadata that effectively triggers a particular action when invoked, as Java code or script, as code written in a particular programming language (e.g., as C++ code), as a processor-specific instruction set, or in some other manner. The instructions may be executed by the same processor or by different processors or processor cores, depending on the implementation.Throughout this disclosure, various processes are described, any of which may generally be implemented as instructions stored on a non-transitory, machine-readable medium, and any of which may be used to manufacture a product. Depending on the product design, such products may be manufactured for sale or may be created as preparatory steps for other printing, curing, manufacturing, or other processing steps that ultimately result in a final product for sale, distribution, export, or import, incorporating the post-manufacturing layers. Again, by way of example, it has already been mentioned that one contemplated implementation may be used to create layers of an electronic display. Other layers may be added incrementally through other processes without damaging (substantially altering) the layers created by the precision processes described herein. The resulting display may also be combined with other elements (e.g., to form a functional television or other electronic device) without substantially altering the layers created by the precision processes described herein. Depending on the implementation, the instructions or methods described herein may be performed by a single computer or may be stored and / or executed in a distributed manner, e.g., using one or more servers, web clients, or application-specific devices. Each function referred to herein with reference to the various figures may be implemented as part of a combined program or as a stand-alone module, and may be stored together on a single media representation (e.g., a single floppy disk) or on multiple individual storage devices. The same is true for error correction information generated according to the processes described herein; i.e., templates or "recipe" representing predetermined printing operations may be modified to incorporate positional errors or feedback and may be stored on a non-transitory machine-readable medium, either for current or future use on the same machine or for use on one or more other machines.For example, such data can be generated using a first machine and then stored for transmission to a printer or manufacturing device, e.g., for download via the Internet (or other network), or for manual transport (e.g., via a portable medium such as a portable drive) for use by another machine. As used herein, "raster" or "scan path" refers to the progression of movement of a print head or camera relative to a substrate, which need not be linear or continuous in all embodiments. "Curing," "solidifying," "processing," and / or "rendering" a layer, as those terms are used herein, refer to processes applied to deposited ink to transform the ink from a liquid state into a permanent or semi-permanent structure of an object being created (e.g., as opposed to a temporary structure such as a temporary mask). Various processes are described throughout this disclosure, any of which may generally be implemented as instruction logic (e.g., as instructions or other software logic stored on a non-transitory machine-readable medium), hardware logic, or a combination thereof, depending on the specific implementation or particular design. As used herein, "module" refers to a structure dedicated to a particular function, e.g., a "first module" refers to a structure that performs a first particular function, a "second module" refers to a structure that performs a second particular function, and when used in the context of instructions (e.g., computer code), refers to a mutually exclusive set of code. When used in the context of a mechanical or electromechanical structure (e.g., a cryptographic module), the term module refers to a dedicated combination of elements that may include hardware and / or software.In all cases, the term "module" is used to refer to a structure dedicated to performing a function or operation that would be understood by one of ordinary skill in the art to which the subject matter pertains as a general structure (e.g., a software module or a hardware module) used in a particular technology, rather than as a generic placeholder or "means" for "any structure" (e.g., a "horse cart") to perform the recited function.

[0019] Similarly, reference is made herein to detection mechanisms as well as alignment marks or fiducials recognized on each substrate, or recognized as part of the printer platen or transport path, or as part of the printhead. In many embodiments, the detection mechanism is an optical detection mechanism using a sensor array (e.g., a camera) to detect recognizable shapes or patterns on the substrate (and / or on physical structures within the printer). In other embodiments, a sensor “array” is not assumed; for example, a line sensor is used to detect fiducials as the substrate is loaded into or advanced through the printer. It should be noted that some embodiments rely on patterns (e.g., simple alignment guides, lines, or marks) while others rely on more complex, recognizable features (including the geometry of some previously deposited layer on the substrate or physical features in the printer, printhead), each of which serves as a “fiducial.” In addition to using visible light, other embodiments could rely on ultraviolet or other invisible light, magnetic, radio frequency, or other forms of detection of substrate features relative to the expected printing location. Additionally, while various embodiments herein refer to a printhead(s) or printhead assembly, it should be understood that the printing systems described herein can generally be used with one or more printheads, whether modularly mounted or not. In one possible application, for example, an industrial printer is characterized by three printhead assemblies (each sometimes referred to as an "ink stick" mount), with each such assembly or mount comprising three separate printheads having a mechanical mounting system that allows positional and / or rotational adjustment such that the printheads (e.g., of the printhead assembly) and / or printhead assemblies and / or their nozzles can be precisely aligned to a desired grid system. Other configurations with one or more printheads are also possible.Generally speaking, "film" or "coat" is used herein to refer to the raw deposited material (e.g., liquid), while "layer" is generally used to refer to the processed structure, e.g., after solidification, curing, polymerization, or other conversion into a permanent or semi-permanent form. Generally speaking, the "x-axis" and "y-axis" are used to refer to the plane of deposition, while the "z-axis" is used to refer to the direction perpendicular to this surface, although it should be understood that these references may indicate any respective degree of freedom of movement. Various other terms are defined below or used as apparent from the context.

[0020] In the following description, the basic configuration of a split-axis industrial printer is first described with reference to FIGS. 1A-1D, followed by a description of some of the challenges associated with precise drop placement and how the novel architecture employed by such split-axis industrial printers addresses these challenges. FIGS. 2A-2B are described as illustrating the architecture of first and second embodiments, and FIGS. 3A-3B are described as illustrating exemplary steps or methods for operating these embodiments, respectively. Generally speaking, the embodiments in which x,y position calibration and alignment are performed are first described, followed by further incremental z-axis measurements. FIGS. 4A-4C are used to describe an embodiment providing high-resolution measurement of absolute z-axis (i.e., height) measurements and alignment relative to a manufacturing tool coordinate system. Subsequent figures are used to describe additional, more specific embodiments. Such designs can be embodied, for example, in printing systems designed to deposit the organic materials used to create layers of light-emitting products, including "active layers" that contribute to the generation of light, as well as passive layers that encapsulate sensitive electronic elements; such manufacturing equipment can be used in the production of "OLED" televisions and other display screens.

[0021] B. Exemplary Environment—Split-Axis System with Printer FIG. 1A provides an overview of a manufacturing process generally designated by reference numeral 101, and also displays many possible individual embodiments of the techniques introduced herein. As seen on the left side of the figure, a series of substrates 105 are processed, each having a layer deposited thereon. Here, the deposition process is aided by the techniques described herein, making the process more accurate and / or faster for each successive substrate than would be possible without those techniques. On the right side of FIG. 1A, one of the series of substrates (107) is shown in its completed form, ready for cutting into multiple products (as indicated by the dotted line portion of substrate 107); for example, the completed substrate 107 can be used to form one or more mobile phone displays 109, HDTV displays 111, or solar panels 113.

[0022] To form the layer of interest, a manufacturing tool 103 is used to deposit, process, and / or treat the material. As described further below, in one embodiment, the manufacturing tool can include a printer (119) that prints the material in discrete droplets, which spread over a limited area to form a continuous (at least locally) liquid coat, and the manufacturing tool or other device then processes the liquid coat to convert the material into a permanent or semi-permanent form. In one embodiment, the liquid is an organic material (e.g., a monomer) that is cured, dried, baked, or otherwise treated to change the form and / or physical properties of the organic material into a form that persists as a layer in the final device. A possible manufacturing process could use ultraviolet (UV) lamps to convert the monomer into a polymer, essentially converting the monomer into a conductive, electrically active, luminescent, or other form of plastic. The techniques described herein are not limited to these types of materials. It should be noted that there may be prior processing steps (e.g., there is a current, underlying surface geometry comprised of microstructures already on the substrate 105) and / or subsequent processing steps (e.g., other layers and / or processes are applied after the completion of a layer and / or film produced by the fabrication tool 103). FIG. 1A also displays a first computer icon 115 and associated non-transitory machine-readable medium icon 117, indicating that the fabrication tool may be controllable by one or more processors operating under the control of instruction logic; for example, such software and / or processors may control or direct the calibration, alignment, and measurement techniques described herein. FIG. 1A also displays a second non-transitory machine-readable medium icon 118, indicating that deposition on each subsequent substrate 105 may be performed according to instructions for a predetermined printing process, or “recipe,” e.g., a common design intended to be applied to each subsequent substrate 105.The techniques described herein can be used to adjust printer elements and / or printing process parameters to more accurately print according to a common recipe, or can be used to transform or adjust the recipe itself (e.g., potentially on a substrate-by-substrate basis) so that individual printing operations (e.g., firing signals applied to nozzles, etc.) are adjusted according to the calibrations, alignments, and measurements described herein. The latter process effectively adjusts the design to reduce errors / variations and achieve the desired printing results despite such errors or variations.

[0023] Thus, the technologies introduced in this disclosure can optionally be in the form of instructions, e.g., control software, stored on a non-transitory machine-readable medium 117. Per computer icon 115, these technologies can also be implemented as part of a computer or network, e.g., as part of a computer system used by a company that manufactures products. Third, as illustrated using reference numeral 103, the technologies introduced above can also take the form of manufacturing equipment or components thereof, e.g., a manufacturing equipment position measurement system or a printer controlled according to position signals and / or calibrations generated using the technologies described herein. Fourth, the technologies described herein can also take the form of modified “recipe” (e.g., printer control instructions modified to mitigate alignment, ratio, skew, or other errors). Finally, the technologies introduced above can also be embodied as manufactured products or things themselves. For example, in FIG. 1A, several such elements are shown in the form of an array 107 of semi-finished flat panel devices, separated and sold for incorporation into end-consumer products. The illustrated devices may comprise, for example, one or more emissive, encapsulating, or other layers fabricated according to the methods introduced above. For example, the techniques described herein may be implemented in the form of improved digital devices 109 / 111 / 113 (e.g., electronic pads or mobile phones, television display screens, solar panels, etc.) or other types of devices.

[0024] FIG. 1B illustrates one possible multi-chamber manufacturing tool 121 that can be used to apply the techniques disclosed herein. Generally, the illustrated tool 121 includes several common modules or subsystems, including a transfer module 123, a printing module 125, and a processing module 127. Each module in this example maintains a controlled environment relative to the ambient air. The controlled environment may be the same throughout the manufacturing tool 121 or may be different for each chamber. The transfer module 123 is used to load and unload substrates or otherwise transfer substrates to other manufacturing tools. Each received substrate can be printed in a first controlled atmosphere by the printing module 125, and (if desired) can undergo other processing, such as other deposition processes or curing, drying, or baking processes (e.g., for printed materials), in the first or second controlled atmosphere by the processing module 127. The fabrication tool 121 may use one or more mechanical handlers to move substrates between modules without exposing the substrates to an uncontrolled atmosphere (i.e., ambient air, which may contain particulates, moisture, and other foreign matter). Within any given module, other substrate processing systems and / or specific equipment and control systems may be used that are tailored to the processes performed for that module. Within the printing module 125, mechanical processing may include the use of levitation tables, grippers, and alignment / micro-error correction mechanisms (in a controlled atmosphere), as described above and below. In some embodiments, other types of deposition equipment (besides printers) may be used.

[0025] The transfer module 123, according to various embodiments, can include an input load lock 129 (i.e., a chamber that provides buffering between different environments while maintaining a controlled atmosphere), a transfer chamber 131 (which also includes a handler for transporting substrates), and an atmospheric buffer chamber 133. As previously mentioned, the print module 125 can use a levitation table for stable support of the substrate during printing. Additionally, an x-y-z motion system, such as a split-axis or gantry motion system, can be used for precise alignment of at least one print head relative to the substrate, as well as providing motorized y-axis transport of the substrate and motorized x- and z-axis transport of one or more print heads through the print module 125. The print chamber can also use multiple inks for printing, e.g., using separate print heads or print head assemblies, so that, for example, two different types of deposition processes can be performed within the print module in a controlled atmosphere. The printing module 125 can include a gas enclosure 135 that houses the inkjet printing system along with means for introducing an inert atmosphere (e.g., nitrogen or a noble gas) or otherwise controlling the atmosphere for environmental conditioning (e.g., temperature and pressure), gas composition, and the presence of particulates.

[0026] The processing module 127 according to various embodiments can include, for example, a transfer chamber 136, which also includes a handler for transporting substrates. Additionally, the processing module can include an output load lock 137 for transferring or otherwise unloading substrates to and from other manufacturing equipment, a nitrogen stack buffer 139, and a curing chamber 141. In some applications, the curing chamber can be used to cure the monomer film and convert it into a uniform polymer film. In other applications, the curing chamber can be replaced by a drying oven or other processing chamber. For example, two particular processes include a heat treatment and a UV radiation curing treatment.

[0027] In one application, the apparatus 121 is adapted for mass production of liquid crystal display screens or OLED display screens, for example, fabricating an array of eight screens at a time on a single large substrate. These screens can be used as display screens for televisions and other forms of electronic devices. In a second application, the apparatus is used in much the same way for mass production of solar panels or other electronic devices. In an exemplary assembly-line process, each substrate in a series of substrates is fed through input load lock 129 and mechanically entered into transfer chamber 131. If necessary, the substrate is then transferred to a printing module, where a liquid coat is deposited in a previously implemented manner according to highly detailed positional parameters. Following a settling period to allow the droplets to melt and establish a locally uniform liquid coat, the substrate is fed into processing module 127, where it is variously transferred to an appropriate chamber (e.g., curing chamber 141) for appropriate curing or other processing to complete the layer, and the layer is then fed out via output load lock 137. It should be noted that various of these modules can be interchanged, omitted, or modified depending on the configuration; in other words, in any process, a minimum of manufacturing equipment deposits some material used to "build" the desired layer of the final product. As previously mentioned, in a typical process, deposition parameters are strict and may require each "picoliter"-scale droplet to be placed at a specific location on the substrate with accuracy down to one or a few microns, sometimes deliberately varying droplet size and / or placement for a particular desired purpose. See the previously mentioned patents and patent applications incorporated by reference.

[0028] By repeated deposition of subsequent layers at controlled thicknesses, the light-generating structure's emissive layer, electronic microstructure element layer, or bracketing layer (e.g., encapsulation) can be constructed to suit any desired application. In one embodiment, one or more of the layers can be different, but it is also possible to fabricate a series of microlayers (e.g., each less than 20 microns thick) to collectively build a thicker layer. The modular nature of the illustrated manufacturing equipment can be used to specialize the manufacturing equipment for a variety of different applications; for example, as mentioned above, one application may employ a bake chamber, where a "printed" liquid coat is processed by baking the layer into a permanent or semi-permanent structure. In different embodiments, it may be desirable to use UV light to cure the deposited layers and perform similar processes. Thus, it will be apparent that the configuration of apparatus 121 can be varied to place the various modules 123, 125, and 127 in different sequences, or to use additional, fewer, or different modules, many of which will depend upon the type and design of the product being manufactured, the desired deposition materials, the particular types of layers being formed, the end product application, and potentially other factors. As each substrate in the series is completed, the next in the series is introduced and processed in much the same manner.

[0029] While Figure 1B provides one example of a set of related chambers or manufacturing elements, clearly many other possibilities exist. The techniques introduced above can be used with the apparatus shown in Figure 1B or to control manufacturing processes performed by any other type of deposition equipment.

[0030] FIG. 1C is a schematic overhead view of a split-axis printer 151. This printer can be used as one non-limiting example of a manufacturing device. It should be noted that the figure is drawn out of scale using generalized partial representations to help explain the basic mechanisms and concepts. For example, the printhead 165 typically has many more than the five depicted nozzles 167, potentially thousands or tens of thousands of nozzles, to print as wide a swath as practically possible onto the underlying substrate 157 as accurately and quickly as possible. Similarly, only general details and elements are presented to explain the principles of operation. In the context of assembly-line manufacturing, it is generally desired that printing be accomplished in less than 60 to 90 seconds for panels that may be meter-long and meter-wide, i.e., that the manufacturing process be as inexpensive as possible without sacrificing quality.

[0031] The printer includes a printhead assembly 165 that is used to deposit ink onto a substrate 157. As previously mentioned, in manufacturing processes, inks typically have a viscosity that spreads only over a limited range and retains a thickness that will become the thickness of the layer when some processing is performed to convert the liquid coat into a permanent or semi-permanent structure. The thickness of the layer formed by depositing liquid ink depends on the volume of ink applied, e.g., the density of the droplets deposited in a given location and / or the volume of the droplets. Inks are typically characterized by one or more materials that will form part of the final layer, formed as a monomer, polymer, or material carried by a solvent or other transport medium. In one embodiment, these materials are organic. Following ink deposition, the ink is dried, cured, solidified, or otherwise processed to form a permanent or semi-permanent layer. For example, in some applications, an ultraviolet (UV) curing process is used to convert a liquid monomer into a solid polymer, while other processes dry the ink to remove the solvent and leave the transported material in the desired location. Other processes are also possible. It should be noted that there are many other features that make the illustrated printing process different from typical graphics or text applications. For example, as described elsewhere herein, in one embodiment, manufacturing equipment is used that encloses the printer 151 in a gas chamber so that printing can be performed in the presence of a controlled atmosphere to exclude moisture and other undesirable particulates.

[0032] As further seen in FIG. 1C , print head 165 moves back and forth in the “x-axis” dimension on support bars or guides 155 relative to support table or chuck 153 in a manner indicated generally by double-headed arrow 169. A dimension legend 163 has been placed in the figure to aid in interpretation of the axes. Note also that print head 165 in this figure is depicted with dashed lines to indicate that it is hidden by support bar 155, i.e., pointing downward toward substrate 157, ejecting ink droplets that fall by gravity from individual nozzles 167 and land in predetermined, planned locations on the top surface of substrate 157. While only a single print head 165 and a single row of nozzles 167 are shown, it should be understood that typically there will be multiple print heads, each with hundreds of nozzles, and possibly thousands of nozzles in total. The printheads are typically staggered with respect to their "x-axis" positions to provide an effective pitch between nozzles on the order of tens of microns, with the printheads in some embodiments mounted on a motion assembly that allows one or more of: (a) powered printhead rotation to change the effective "cross-scan" pitch; (b) powered printhead height adjustment above the substrate (or, more precisely, relative to the supporting printhead carriage or "ink stick" mount for cluster printheads); (c) powered or manual printhead leveling, i.e., leveling so that the nozzle orifice plate is parallel to the received substrate, and / or (d) modular exchange with other printheads or "ink stick" mounts, as well as possibly other motions. It should be noted that unlike a typical graphics printer in which the substrate (e.g., paper) is slowly advanced along the "y-axis" as the printhead is moved back and forth as indicated by reference numeral 169, in an industrial printer, substrate transport along the "y-axis" is typically the fast-moving axis, while the printhead is typically only changed position in the direction indicated by double arrow 161 during a scan (relative motion between the substrate and printhead).Thus, in this example, the "y-axis" is referred to as the fast-axis or "in-scan" dimension, while the "x-axis" is referred to as the "slow-axis" or "cross-scan" dimension. In this example, each printhead typically deposits the same ink at any one time (even if there are multiple printheads), with the simultaneous objective of covering as wide a swath as practical at one time while providing a microscopic cross-scan pitch of the deposited droplets so that the number of scans for each product layer can be reduced, increasing production / printing speed. The substrate is typically an ultra-thin glass sheet, and the support table or chuck 153 is typically a levitation table that supports each substrate on a cushion of air (or other atmospheric gas). In the illustrated system, when the substrate is introduced, a vacuum gripper 159 engages the substrate along one edge and moves it back and forth along the y-axis during printing. The gripper follows a track or path (not shown in FIG. 1C ) and provides one axis of transport in the split-axis system shown, while bar or guide 155 provides the other. As is clear from this example, any desired print location on substrate 157 can be achieved by carefully controlled movement of the substrate along the y-axis in the cross-scan dimension using gripper 159, and printhead 165 in the cross-scan dimension (i.e., along the x-axis).

[0033] As is evident when cross-scan nozzle pitch is on the micron scale, even slight calibration errors could theoretically result in ink droplets being placed in the wrong location on the substrate. Thus, for precise control of droplet placement in such systems, calibration techniques such as those described herein are employed to ensure droplets are placed at their expected precise locations, i.e., with an error of a few microns or less, and ideally, much smaller. As with many other descriptions herein, this type of system (printer / segmentation axis) is merely representative, and the details described should be considered an optional implementation example presented to provide an understanding of one possible embodiment.

[0034] FIG. 1D shows one substrate (181) in a series as it passes through the printer. As with any particular design, several dashed boxes indicate individual panel products 183. The diagram in this example shows just four such panel products. Each substrate (in a series), such as substrate 181 shown in FIG. 1D, in one embodiment, has multiple alignment marks. In the illustrated embodiment, three (or more) such marks 187 are used across the entire substrate, allowing measurement of positional offset and / or rotational errors of the substrate relative to the manufacturing equipment (e.g., relative to a chuck, parting axis transport path, or other reference frame). Other errors, such as distortion errors (e.g., the bottom surface of the product has a nonlinear major axis relative to the printer axes) and / or scale errors between the substrate and the printed image (i.e., in the x-dimension, y-dimension, or both), can also be detected. To detect these various errors, one or more camera assemblies 185 are used to image the alignment marks. In one contemplated embodiment, a single camera assembly (e.g., attached to the printhead assembly) is used. As noted above, the split-axis system allows the printhead to be positioned above any location on the substrate through coordinated operation of two transport systems, and the interrelationship of the camera assembly in this embodiment is not different. That is, the printer's transport mechanism (e.g., a handler and / or air levitation mechanism) moves the substrate and camera to sequentially position each alignment mark in the camera assembly's field of view. In one embodiment, the assembly includes both high-resolution and low-resolution cameras, while in other embodiments, a single camera or a different type of sensor (such as a stationary, optical line sensor) can be used to detect the actual position of the substrate relative to the printer's reference axis. As implied, the camera assembly in this example could be attached to the printhead carriage or the printhead assembly, i.e., a second assembly, depending on the embodiment, or it could be attached to a different carriage (or bridge or guide).The two-camera system captures low and high magnification images: a low-magnification image to roughly position fiducials for high-resolution magnification, and a high-magnification image to identify precise fiducial locations according to the printer coordinate system. With reference to Figure 1D, these various structures are used to detect the relationship between each substrate and the coordinate system of the manufacturing equipment so that substrate alignment, orientation, placement, twist, and scale can be normalized and factored into the deposition, allowing manufacturing to deposit material in exactly the same location (i.e., relative to the alignment marks) for each substrate.

[0035] Mirroring the previously described structure, in one possible embodiment, a camera assembly can be fabricated integrally with the printhead assembly (i.e., the printhead carriage described above) to align each substrate with the printer coordinate system or calibrate the positional reference system of the manufacturing apparatus (i.e., positional calibration and effective alignment of the two transport paths prior to introduction of a substrate) to match printing parameters to the actual position / orientation / skew and / or scale of each substrate, and further, detect the fiducial position of each substrate, as shown in connection with FIG. 1D . Like the other described elements, the camera assembly can be a modular unit that is interchangeable with other modules in the printer's maintenance station, as is the case with the ink stick mount described above. However, in one embodiment, the camera used by the printhead transport path is fabricated as an integral and permanent part of the printer head assembly.

[0036] In a typical embodiment, printing is performed to deposit a given layer of material across the entire substrate at once (i.e., by a single printing process that provides a layer in each scan or set of scans for the substrate for multiple products). Note that such deposition can be performed within individual pixel wells (not shown in FIG. 1D; there are typically millions of such wells), depositing a light-generating layer within such wells, or generally depositing a barrier or protective layer, such as a barrier or encapsulation layer. Regardless of the deposition process in question, FIG. 1D shows two exemplary scans 189 and 191 of the print head along the long axis of the substrate; in a split-axis printer, the substrate is typically moved back and forth (e.g., in the direction of the arrows shown in FIG. 1D and the double arrow 161 from FIG. 1C) while the printer advances the print head positionally (i.e., in the "x-axis" direction or perpendicular to the plane of the figure) between scans. Note that while the scan paths are shown linearly, this is not required for all embodiments. While the scan paths (i.e., 189 and 191) are shown adjacent and mutually exclusive in terms of coverage, this is also not required for all embodiments (e.g., the printhead can be applied fractionally in terms of print swaths, if desired). Finally, note that any given scan path typically traverses the entire printable length of the substrate, printing layers for (potentially) multiple products in a single pass. Each pass uses nozzle firing decisions according to a “print image” or nozzle bitmap to ensure that each drop in each scan is deposited exactly where it should be relative to the substrate and / or product / panel boundaries. As shown, during a first scan 189, in which the substrate 181 is moved along the “fast axis” or “in-scan” direction (i.e., the y-axis in FIG. 1C ) relative to the printer, the printhead assembly is positioned at a first position 193.On the other hand, during a second scan 191 in which the substrate is moved in the opposite direction along the "fast axis" or "scan" direction, the print head assembly is repositioned along the "slow axis" or "cross-scan" direction (as indicated by arrow 195) to position 194 instead of position 193, thereby forming the swath indicated by reference numeral 191.

[0037] Once all printing is complete for a given layer or film, the substrate and wet ink (i.e., the deposited liquid stabilized to a wet coat) can then be transported for curing or processing into a permanent or semi-permanent layer of deposited liquid. For example, briefly returning to the discussion of FIG. 1B , a substrate can be “inked” in print module 125 and then transported to curing chamber 141 without any disruption of the controlled atmosphere (i.e., this process is advantageously used to prevent moisture, oxygen, or particulate contamination) until the processed layer is formed. In different embodiments, a UV scanner or other processing mechanism can be used in situ, for example, with a split-axis traveler, in much the same manner as the printhead / camera assembly described above.

[0038] C. First Embodiment—Calibration, Alignment, and Position Sensing in a Split-Axis System 2A is an illustration of a split-axis system 201 utilizing precision calibration, alignment, and / or detection, as introduced above. Note that implementations may differ slightly from those shown (e.g., printhead 223 typically faces "down" toward the drawing page so that it fires droplets toward the drawing page instead of as shown; further, the height shown extends into and out of the drawing page rather than as shown, and sensor 229 faces up, toward the screen page). Nevertheless, to aid in explanation and reader understanding, the illustrated example is relied upon in this figure.

[0039] The split-axis system features a first transport path 203 (e.g., used to transport printhead assembly 205 in the direction indicated by double arrow 207) and a second transport path 209 (e.g., used to transport gripper 211 in the direction indicated by double arrow 213). Note that double arrows 207 and 213 represent reciprocating motion (e.g., reversing scan path direction, as indicated by reciprocating swaths 189 and 191 in FIG. 1D ), and these types of systems typically feature substantial translational inertia as their elements are moved. For this and other reasons, a position feedback system is also used for each transport path, as indicated by reference numerals 215 and 219. That is, the bridges or guides used to support the printhead assembly feature position marks to aid in accurate position determination. These marks are typically in the form of adhesive tape (i.e., as indicated by “ruler” symbol 215) with marks spaced every micron or a few microns. Sensor 217 of printhead assembly 205 images, optically detects, or otherwise senses these marks to provide feedback based on the actual printhead assembly position. This allows an electronic control and drive system (not shown in FIG. 2A ) to accurately position the printhead carriage despite the effects of inertia, jitter, and other error sources. Similarly, the second transport path (e.g., the printer support table or guide provided by chuck 231) is also typically equipped with a similar set of position marks, such as marked adhesive tape 219, again indicated by ruler marks to indicate that the marks provide position information. These marks are similarly imaged and / or detected or sensed by sensor 221 of gripper 211. This feedback system, in turn, allows an electronic control or drive system (not shown in FIG. 2A ) to accurately position the gripper despite translational inertia, jitter, and other potential error sources affecting positioning.

[0040] Such a system presents challenges in coordinating and aligning these two paths and their associated systems: the first and second transport paths must be related to each other, for example, so that a coordinate system can be defined and directly related to printable locations.

[0041] To this end, some kind of fiducial is provided that each of the printhead assembly 205 and gripper 211 can reach and detect. This fiducial is illustrated by fiducial 235. A first sensor 227 associated with the first transport path and a second sensor 229 associated with the second transport path are used to find this fiducial and establish a common coordinate point for each transport path. Positioning of the printhead 223 at any particular coordinate location relative to the printer's printable area can be based on the location of each position feedback system for each transport path (e.g., as indicated by alignment tape or "ruler" indicators 215 and 219). Note again that FIG. 2A is drawn for ease of explanation and understanding; that is, the printhead 223 and sensor 227 typically face downward toward the drawing page so as to image the fiducial 235. In contrast, sensor 229 typically faces upward, away from the drawing page, so as to image this fiducial 235 from below. To this effect, gripper 211 is capable of moving only vertically ("y-axis") in this embodiment, while printhead assembly 205 moves only horizontally. To allow for rapid location and identification of fiducial 235, in one embodiment, fiducial 235 is attached directly to either gripper 211 or printhead assembly 205. This allows fiducial 235 to be in a known position relative to either sensor 227 or sensor 229. In this example, fiducial 235 is coupled to printhead assembly 205, as indicated by dotted line 237. For example, as described in the following embodiment, fiducial 235 could take the form of an optical reticle if sensors 227 and 229 are both cameras. In such a system, the carriage or assembly moved by each transport path is adjusted until the superimposed images of each transport path feature a reticle registration, and then a position feedback system is used to normalize the position of each transport path. Such position identification identifies a common coordinate point (eg, the origin of a coordinate system) relative to which the x,y transport system is calibrated.The position feedback thereby provides a unit advance relative to the origin. The reticle may be an optical attachment that is optically removed after this calibration. Note that there are many alternatives for finding the common reference point (e.g., sensors 227 and 229 can be configured as cooperating elements of a sensing system that allows precise alignment between them, and, as this description implies, many different types of sensors and / or positioning methods can be used to achieve this collocation). With the described collocation, it is possible to establish a complete x,y coordinate reference system for the printer / manufacturing device.

[0042] When printing begins, a substrate 239 is introduced into the system 201 and engaged by the vacuum elements 225 of the gripper 211. As shown, the substrate 239 may have unintended translational offset and / or rotational errors, as well as potential other errors, such as skew and / or scale errors. It is therefore generally desirable to correct this error or at least reduce it so that droplets from the print head are placed precisely in their intended locations relative to the substrate and / or any product being fabricated thereon. It should be noted that many mechanisms exist for correcting this error. For example, a mechanical handler could be used to reposition the substrate. Alternatively, as described in patents and publications incorporated by reference (see, e.g., U.S. Patent Publication No. 20150298153), printing parameters could be adjusted such that nozzle assignments, firing times, print grid definitions, scan path positions, and / or other parameters are adjusted in software to match substrate errors, essentially enabling virtual correction of minute substrate alignment, orientation, skew, and / or scale errors. Regardless of the mechanism, errors in the position, scale, and / or distortion of the substrate are first identified, in this case using alignment marks 243 (i.e., other fiducials), to make corrections. Recall that in a typical application, the substrate is generally transparent glass, and detection of this error can be performed by controlling the two transport paths to find and image fiducials 243 using sensors 227. Now that the position of fiducials 243 in the printer's coordinate system can be measured, image processing techniques (recognition of fiducials 243) associated with positions known from the position feedback system for each transport path can be used to accurately determine the coordinates of the substrate (i.e., fiducials) relative to the printer. As mentioned above, using complex fiducials or multiple fiducials, the image processing system can also identify other inconsistencies, such as errors in the rotational orientation of the substrate.By performing layer deposition (of all layers of the desired device) relative to a substrate fiducial (e.g., 243), layer alignment can be achieved despite substrate position and / or orientation as well as other errors such as substrate edge nonlinearity, distortion and / or scale errors.

[0043] Each of these various disclosed processes can be performed with operator intervention or fully automated under processor control (especially with the aid of the techniques introduced herein). For example, in one embodiment, a common coordinate point is established by an operator who manually engages each transport system to view images provided by each camera and manually align the reticle imaged by each camera. Alternatively, in one embodiment, this alignment operation is performed entirely by an image processor, which uses, for example, image processing, search algorithms, and associated electronic control for each transport path. Image processing software causes one or more processors to detect alignment and / or misalignment of the reticle between images generated by the cameras, drive the transport motion system to reduce or eliminate this misalignment, read position data from feedback system 215 / 219, and "zero" the system to a common reference point. Image data from each camera is stored in frame readout circuitry for each camera. Definition of the common coordinate point is then stored in processor-accessible non-transitory memory for use in position detection.

[0044] Once the substrate position and / or printing parameters have been corrected in response to measured position and / or orientation errors that deviate from one or more substrate datums 243, the substrate can, in one embodiment, be advanced by a gripper as required for printing, for example by being transported back and forth in the scanning direction as indicated by double arrow 241.

[0045] However, the system shown in FIG. 2A also potentially introduces errors if the height of the printhead 223 (and each nozzle of the printhead) above the substrate is not carefully controlled. This is explained with respect to the printhead 223, the associated ejected droplets, and the height indicators "h0," "h1," and "h2" shown next to the associated droplet apparent velocity indicator "v." Note again that this is for illustrative purposes only; with the substrate moving along the "fast axis" in the direction of double arrow 241, the droplets and substrate move relative to one another as the droplets are ejected downwards toward the substrate and the drawing page. During scanning, the continuous motion of the substrate as the ejected droplets fall means that the droplets land on the substrate at a location that depends on (a) the velocity of the substrate, (b) the droplet ejection velocity, and (c) the distance or height between the printhead and the substrate; variations in height at a constant velocity translate directly into variations in the droplet landing location on the substrate. In practice, landing location variations are typically on the order of one-fifth of the height variation; for example, if a printhead nozzle has a typical height above a substrate of 2 millimeters and the height error and / or variation is on the order of 100 microns, this variation translates to about a 20 micron difference in the intended drop landing location. Note that the error can be more significant if the height is not understood or the effective height variation is larger.

[0046] To account for this potential source of error, in one embodiment, the height of the deposition source above the substrate is also calibrated, measured, and controlled during deposition. In one embodiment, this calibration is performed using sensors 227 and 229, as well as an alignment system fiducial (e.g., reticle 235). In other embodiments (introduced below in connection with FIGS. 4A-4C), other sensor systems (i.e., absolute position sensors) can be used to measure the height. For the illustrated system, the difference in printhead height relative to the cameras on the printhead assembly may not be precisely known, and as a result, it is advantageous to measure both heights "h0" and "h1" so that height "h2" can be inferred from height "h0" measured using sensor 227 (i.e., by h2 = h0 - h1). While in some printer embodiments it may be sufficient to simply "know" one height for the printhead (e.g., if level control over the printer head nozzle plate allows for reasonable accuracy), in other embodiments it may be desirable to measure the absolute height of each nozzle orifice of each printhead, thereby allowing differences in apparent droplet velocity from nozzle to nozzle to be accurately understood and otherwise mitigated. It should also be noted that, as described in the patents and published patent applications incorporated by reference, e.g., U.S. Pat. No. 9,352,561 in particular, each nozzle may have errors in nozzle position ("nozzle deflection"), droplet ejection volume, droplet trajectory, and / or droplet velocity due to manufacturing process corners, and that these errors may exhibit statistical variation. Thus, in one possible embodiment, a statistical model can be developed for each nozzle (i.e., as described in U.S. Pat. No. 9,352,561) where the measured height for each nozzle is incorporated into a calculation of the expected droplet landing location, developing an accurate prediction of where droplets from each nozzle will land relative to the nozzle height and process corners that affect that particular nozzle.As introduced earlier, such information can be used to correct deviations from the desired height depending on the implementation, for example, by adjusting the printhead height (in one embodiment, the printhead, printhead carriage or "ink stick" has an electronically actuated z-axis motor). ), which can be used to correct for by adjusting the droplet velocity, ejection time, substrate position, nozzle used for deposition, droplet timing, cross-scan pitch and / or other printing parameters.

[0047] FIG. 2B provides further details regarding height calibration and related measurements in one embodiment. More specifically, FIG. 2B illustrates system 251, again showing printhead carriage 205 and gripper 211. In this illustration, the gripper advances in and out of the drawing page (i.e., moves supported by support guides 261, as indicated by the dimension legend), while printhead carriage 205 advances back and forth parallel to the x-axis, as indicated by reference numeral 207. As previously mentioned, the printhead carriage uses position reference frame 215 (shown as ruler marks), and the gripper uses position reference frame 219 (which extends in and out of the drawing page and is detected by sensor 221 as the gripper moves). The reticle (i.e., the datum to which coordinate references for the division axes are related) is shown as lying in the x-y plane and is referenced by reference numeral 255. The reticle is held in place by a mechanical mount (i.e., an "L-bar" or equivalent) 257 so that it resides directly in the optical path 251 of the camera 253. In one embodiment, the mount can be a dynamic mount, adjusted once (or aperiodically) to allow manual or automatic docking and undocking on demand while repeatedly and accurately adopting a consistent position relative to the field of view of the camera 253. The camera includes an electronic autofocus system that allows the camera to focus (indicated by the conical optical path 259) and is adjusted to accurately image the reticle. In this case, the reticle can be a set of crosshairs on a transparent plate. Note again that while items are shown in this figure to aid in illustration and description, details in implementation may vary.

[0048] The distance between the camera and the reticle is calculated by adjusting the focus of the camera to obtain precise focus, thereby giving the camera focus a particular associated focal length (i.e., "depth of focus"), where the height (h4) is calculated directly from this focal length or depth of focus by a processor (operating under the direction of image processing software).

[0049] Like the printhead assembly, the gripper 211 also carries a camera 263 (facing upward) to locate and image the reticle from below. Again, the image produced by the camera is focused (per the cone of light 265 shown) and used to derive the height of the reticle from this second camera, again based on the focal length and a processor calculation of a height "h5" from this second focal length. The distance between the cameras (in the absence of a substrate, i.e., during calibration) is then given by the sum of these two heights, which is also calculated by a software-controlled processor.

[0050] Prior to introduction of the substrate, the printhead carriage is moved so that the printhead 223 (i.e., alignment marks or features on the bottom of the printhead) can be imaged by the lower camera 263, which is also focused and used to obtain a new focal length and associated height "h6," which indicates the height of the printhead above the upward-facing (second) camera. The height "h1" of the printhead (or a particular feature thereon) relative to the upper camera 253 can then be determined, i.e., this is by calculating the value h1 = (h4 + h5) - h6, and stored in processor-accessible memory for future use.

[0051] When printing is desired, the reticle 255 and associated mount are moved (either manually, mechanically, or robotically) and the substrate 239 is introduced into the system. Similar to the height determination process described above, the downward-facing printhead assembly's camera is used to detect the position, in this case by imaging a feature on the substrate (e.g., the substrate's alignment mark 243 in FIG. 2A), after which the proper focus of the camera is identified, allowing the processor to calculate the distance "h7" between the upper camera and the substrate directly from the new focal length. However, the deposition source (i.e., the printhead or any particular nozzle thereof) need not be at the same height as h7; it may differ from this value by tens of microns. To account for this, the stored height "h1" is retrieved from processor-accessible memory and subtracted from the newly calculated height "h7" to give the measured height "h2" to which the droplet is expected to fall before impacting the substrate.

[0052] It should be noted that this system and associated calculations can be performed with or without the involvement of a human operator. That is, in one embodiment, various camera focal points are displayed on a monitor, and an electronic focus system is controlled by a human operator until a clear image is displayed. Alternatively, the focus system can be automatically controlled by software using known image processing techniques to obtain accurate focus and generate focal lengths and associated heights. This may be preferable in some embodiments to speed up the process and eliminate potential human error.

[0053] It should be noted that many measurements can be made using the system just described. For example, a gripper-mounted, upward-facing camera can be used to measure the height of each printhead's nozzle orifice plate above the upward-facing camera to detect height misalignment between printheads and / or tilt / level of individual printheads. The upward-facing camera can also be used to identify (through image processing) the xy position of each nozzle and correct for errors in that position (see again, e.g., the techniques described in the patents and publications incorporated by reference).

[0054] While the illustrated embodiment is suitable for many calibration procedures, there are still many uncertainties that limit the achievable accuracy and resolution of the measured height. For example, temperature variations, the refractive index of the reticle 255, and the difficulty of objectively setting accurate camera focus are all potential sources of error, even when performed with the assistance of machine control. Furthermore, the required precise focusing can be time-consuming, especially when performed by a human operator. Finally, while the described system can easily measure a fiducial height of a purposefully provided substrate, dynamically measuring height at any position on the substrate (i.e., based on difficulty or relying on image processing and variable focusing for potentially unknown features) can be more challenging. For all these reasons, some possible embodiments advantageously employ the example described below in connection with FIGS. 4A through 4C. This example provides faster and more robust calibration, alignment, and measurement, particularly when applied to height measurements. Such a system separates the height measurement from the image focus method referenced above, but still employs a reciprocating height measurement system to obtain results with greater accuracy and speed. This is further explained below with reference to Figures 4A to 4C.

[0055] 3A and 3B provide flowcharts 301 and 341 of method steps associated with the exemplary operations described above with reference to FIGS. 2A and 2B.

[0056] As shown in FIG. 3A, a first method is presented as a flowchart generally designated by the numeral 301. A set of alignment processes can be first performed to correlate one or more axes of a manufacturing tool 302 used to deposit material from a deposition source, for example. For example, with respect to the split-axis system described above, calibration can be performed for one or more motion systems to correlate these systems in one or more of the "x-axis" dimension, the "y-axis" dimension, and the "z-axis" dimension. In one embodiment, it is assumed that the x and y transport mechanisms are to be corrected, but other dimensions can also be calibrated using the techniques described above. Each assembly in the two different transport paths is first moved to a predetermined position, e.g., a predicted origin where the two transport paths intersect (303). The post-transport assembly for each path includes an integrated sensor that is used to identify a common reference frame (304). If necessary, following the rough alignment, a search algorithm can be additionally performed, as indicated by the numeral S305, to precisely establish the reference point. Optionally, position feedback is obtained for each of the transport paths or axes at 309 to measure the trajectory or guide position at a common point. As indicated by 310, this feedback can additionally be provided by alignment marks associated with each transport path. Optionally, as indicated by 311, 312, and 313, the alignment process can feature independent alignment of each sensor to an intermediate point (e.g., a fixed reference associated with the fabrication table or a reticle as previously mentioned), alignment of one sensor to the other (e.g., a reticle is attached to one of the sensors, or vice versa, imaging techniques are used to detect the other sensor), or coaxial optical alignment (e.g., images generated by each of the two sensors are superimposed until they align to define a common optical axis). Other techniques are also possible. Once alignment is achieved, the positions of the assemblies on each transport path are used to establish a coordinate system for deposition / fabrication, i.e., the transport paths are aligned relative to the common axis at 315.This process can be performed to relate or align additional axes together or, if desired, to an existing coordinate system (e.g., z-axis height or other dimension or set of dimensions), as indicated by numeral 316. Once the desired or required number of alignment processes have been achieved, the system is calibrated (317).

[0057] Reference numeral 318 denotes an online / offline processing separation line; steps above this line are typically performed offline, while steps below this line are typically performed online during production. For example, as indicated by reference numeral 321, steps below the separation line may be performed online as part of an assembly-line process for each new substrate introduced into the manufacturing equipment. As each substrate is introduced (322), a transport mechanism is used to detect one of the substrate's fiducials (323), allowing alignment of that individual substrate (or product thereon) with respect to the printer's coordinate system and with respect to the intended recipe information. This allows for derivation of correction or offset information (325). For example, once errors in the substrate's position, orientation, scale, and / or skew are identified, the corrections and offsets can be stored and / or used to correct the substrate's position / orientation or otherwise adjust printing parameters (326). Finally, with the compensation strategy employed, fabrication (e.g., printing 327) occurs to precisely deposit material at the desired location associated with a precision fabrication process. The method can continue (e.g., applying post-printing processing steps to finish the deposited layer of material), as indicated by oval 328.

[0058] 3B shows the alignment process 341 in more detail. As indicated by numeral 343, in one embodiment, the print head (PH) camera is first parked in a maintenance bay or servicing location (e.g., a "second volume" or compartment adjacent to the first volume or compartment where printing will occur), and the reticle is loaded onto the PH camera, either manually or robotically. Note that this is not required for all embodiments; in different implementations, the reticle can be loaded into a predetermined location and then pivoted or engaged by a robot and moved into the correct position at any time in time. Regardless of the specific engagement mechanism, with the reticle in place, the PH camera is moved into position ready for coaxial optical alignment by the second (gripper) camera system. The PH camera is engaged to image / detect (345) the reticle by adjusting (347) the camera and / or reticle position to approximately center the reticle so that it is clearly within the PH camera's field of view and with the focus adjusted (351). As previously described, determining the focal length allows for measurement of the reticle's height relative to the PH camera (356). A second (gripper) camera system is then also moved (357) to this indicated position and used to image (359) the reticle from below. As previously described, the reticle can be a set of crosshairs on a transparent slide, preferably with a refractive index approximately the same as the atmosphere in which printing / fabrication will occur. The gripper camera system (i.e., the gripper position and / or the PH camera position) is then adjusted (361) so that the images generated by each camera system precisely overlap (e.g., as determined by an operator or by image processing software). At this position, the focus of the gripper camera system is adjusted per 361 to allow the height of the reticle relative to the gripper camera system to be derived from the depth of focus. As previously mentioned, this allows the vertical dimension (z-axis spacing) between the PH camera and the gripper camera system to be identified. Note that Figure 3B highlights some of the relevant options for these processes.For example, in one embodiment, this height determination process is coaxial for the PH camera and gripper camera systems (346). In one embodiment, the PH camera and gripper camera systems each include two cameras, e.g., a low-resolution camera that roughly detects the reticle and a high-resolution camera that improves alignment precision and focus determination (348 / 362). As previously mentioned, a human operator can provide control of the system for alignment and / or focus adjustments, for example, by viewing images on one or more monitors (352 / 364) or by responsively controlling the system and / or focus. In other embodiments, such adjustments can be automatically performed and controlled by software (353 / 365).

[0059] Once the distance between the cameras is identified (i.e., "h4" + "h5," as labeled in FIG. 2B), the gripper camera system is used to image a reference, such as the print head itself or a fiducial on the substrate, at 369. A focus adjustment is again performed at 371, or other techniques are used to measure the height from the gripper camera system to the print head reference (i.e., h6 in FIG. 2B) at 372. The processor / software calculates the height difference "h1" between the print head reference and the PH camera (i.e., takes the measured distance between the cameras, "h4" + "h5," subtracts this new value, "h6," and stores the result). If desired, such measurements can be employed, for example, to adjust multiple print heads to the same height, or to adjust each print head to have a lower-level plate (i.e., nozzle orifice plate). Other measurements using the gripper camera system can also be performed as needed, for example, to calibrate the position of each nozzle.

[0060] During printing, if a new substrate is introduced, the system proceeds to find a visual reference (substrate fiducial) with the PH camera for the new fiducial at 373, and the system then readjusts the focus (374), identifies the resulting focal distance, and uses this to derive the vertical spacing "h7" between the PH camera and the substrate at this position at 376. With this distance identified, the processor calculates the vertical spacing between the printhead and the substrate at 378 by subtracting the previously stored value "h1" from "h7" (where the previously stored value "h1" is equal to "h4" + "h5" - "h6"). As variously illustrated by a set of correction procedures 381, possible responses to the identified height include automatically or manually (a) adjusting the height or level of the printhead (383), (b) adjusting the drive voltages (384) to speed up or slow down the droplets, (c) adjusting the timing of the nozzle firing triggers (385) so that droplets are fired earlier or later on their original effective trajectory to reach the desired landing location, and (d) adjusting which nozzles are used to print (386), so that droplets from other nozzles are used to replicate the desired landing location. As previously indicated, other techniques may also be employed.

[0061] Reflecting the described operations, a set of alignment techniques can be employed to co-locate two or more transport systems relative to a common reference point. Position feedback systems can additionally be used to position the deposition material source and / or the substrate so that the manufacturing apparatus can deposit the desired material at any given location on the deposition substrate. A height calibration system can be used to calibrate the height of the deposition source relative to the deposition substrate, optionally relying on the same factors as used by the system for positioning the two transport systems. Finally, the substrate position, source height, and / or deposition details can be adjusted to provide more precise control over the exact deposition point of the material after deposition. In various embodiments, the systems for performing alignment between transport paths and the systems for performing source height calibration are independent and can be employed independently of each other, and each can also be used in conjunction with other types of calibration systems.

[0062] C. Second Embodiment - Accuracy and Dynamic Measurement of Source Height Determination As noted above, the embodiment described with reference to Figures 2A-3B, while suitable for many implementations, may still be a source of unintended error. Figures 4A-4C are employed to introduce other alternative embodiments that provide dynamic height measurements as well as more accurate and rapid height measurements.

[0063] The manufacturing equipment is first initialized at 403 prior to the introduction of a substrate. As part of this initialization process, an auto-calibration routine is executed (405) under the control of software and at least one processor, performing the calibration and alignment steps described above and below. These steps allow the system to relate its transport axis to a reference frame, thereby enabling the deposition source and substrate to be transported relative to each other so that material can be deposited at any desired location on the substrate. As noted above, in embodiments featuring the attachment and detachment of elements such as reticles or camera assemblies attached to and detached from the printhead cartridge, the system is additionally controlled to divert the printhead carriage to a maintenance bay where appropriate tools are automatically exchanged with various tool mounts under automated robotic control. The use of a maintenance bay, i.e., transport of the printhead carriage to the maintenance bay, is not required for all embodiments. In other embodiments, appropriate tools can be engaged in situ or permanently attached in a manner that does not interfere with online printing. Each tool (and printhead cartridge) is configured with electronic, magnetic, and / or mechanical interfaces that enable this, and the selection of the appropriate interface is an implementation change. To this end, in one embodiment, a dynamic mount is employed that provides reliable and repeatable magnetic engagement of a reticle or other suitable tool, e.g., to within a few microns. To engage the tool, the printhead carriage can additionally engage the tool (reticle) robotically or otherwise in precisely the right position, with the tool magnetically anchored in place with up to a micron-scale offset.Optical alignment between the transport axes is then performed using this tool as described in the previous embodiment, for example, by moving one or both transport paths to a position where the camera images feature aligned coaxial reticles, and using the position information / position feedback information for each transport axis to define a common coordinate point, thereby establishing an x-y coordinate system for printing / manufacturing / processing. As described below, this calibration process uses another set of laser sensors to very quickly measure the z-axis height of the print head and / or one or more features associated with the print head. Several processes are performed with these lasers / sensors, including (a) using a camera to identify approximate x-y laser measurement position coordinates for each laser / sensor, (b) using targets (e.g., bores or protrusions) to establish precise x-y coordinate positions for each laser / sensor, (c) measuring printhead height or levelness for each printhead (and, optionally, each nozzle), (d) measuring the height of printhead fiducials (described below), and (e) accounting for drift and periodically recalibrating the lasers / sensors relative to each other or to their x-y positions for accuracy. These various operations are described below. Optionally, as mentioned above, one or more of these processes can also use one or more tools that are robotically or otherwise engaged and disengaged as needed. Note again that many other system measurements can optionally be performed as part of the auto-calibration routine, such as measuring each nozzle position, measuring and / or comparing the height of a printhead relative to other printheads, etc. Note also that the auto-calibration routine 405 in one embodiment is run only once upon initial system installation. In other embodiments, this is performed intermittently (eg, periodically, such as daily or hourly).In yet another embodiment, the calibration routine is performed in response to a system event, e.g., in response to activation, a periodic quality test performed by software that returns deviations above a threshold from a fixed target each time a printhead or "ink stick" is changed, or on an ad-hoc basis (e.g., activated by an operator). It should also be noted that an exemplary system may be characterized by multiple different calibration routines that employ various combinations or subsets of the measurement processes described above in connection with a design or calibration event. Whatever calibration option is employed, an initial (offline) automatic calibration sequence is typically planned to allow the system to receive a series of substrates.

[0064] In assembly-line processing, each substrate in a series typically receives the exact same manufacturing design pattern or "recipe," and the system attempts to properly align / position it using fiducials present on each substrate. A given manufacturing process can be used to form a single layer, typically micron-thick (e.g., between 1 and 20 microns). In the case of an OLED display manufacturing process, for example, the materials can be used to construct layers that contribute to the operation of individual light-emitting elements, including, without limitation, an anode layer, a hole-injection layer (HIL), a hole-transport layer (HTL), an emissive layer (EML), an electron-transport layer (ETL), an electron-injection layer (EIL), and a cathode layer. Additional layers, such as hole-blocking layers, electron-blocking layers, polarizers, and barrier layers, can additionally or alternatively be fabricated and may also include primers or other materials. Light-emitting device designs can be such that one or more of these layers are deposited to establish a "bracket"-like compartment surrounding multiple such elements (e.g., providing a common barrier, encapsulation layer, electrode, or other type of layer), while one or more of these layers may be restricted in area to establish a single light-emitting area for a single pixel (e.g., a single red, green, or blue light-emitting element). In operation, application of a forward bias voltage (the anode is positive relative to the cathode) results in hole injection from the anode layer and electron injection from the cathode layer. Recombination of these electrons and holes creates an excited state in the light-emitting layer material, which then relaxes to the ground state with the emission of a photon of light. In "bottom-emission" structures, light exits through a transparent anode layer formed below the hole-injection layer. The common anode material can be formed, for example, from indium tin oxide (ITO). In bottom-emission structures, the cathode layer is typically reflective and opaque. Common bottom-emission cathode materials include Al and Ag, which are typically thicker than 100 nm. In top-emission structures, emitted light exits the device through the cathode layer, and for optimal performance, the anode layer is highly reflective and the cathode layer is highly transparent.Commonly used reflective anode structures have a layered structure in which a transparent conductive layer (e.g., ITO) is formed on a highly reflective metal (e.g., Ag or Al), providing effective hole injection. Commonly used transparent top-emission cathode layer materials that provide good electron injection include Mg:Ag (approximately 10-15 nm, atomic ratio of approximately 10:1), ITO, and Ag (approximately 10-15 nm). The HIL is typically a transparent, high-work-function material that readily accepts holes from the anode layer and injects them into the HTL layer. The HTL is another transparent layer that transfers the holes received from the HIL layer to the EML layer. Electrons are provided from the cathode layer to the electron injection layer (EIL). Electron injection into the electron transport layer is followed by injection from the EML into the EML, where recombination with holes occurs, resulting in light emission. The emission color depends on the EML layer material and is typically red, green, or blue for full-color displays. The emission intensity is controlled by the rate of electron-hole recombination, which depends on the driving voltage applied to the device.

[0065] To build up the desired layers during system runtime, substrates are sequentially introduced into the fabrication equipment. For organic material deposition, the fabrication equipment can include a printer that deposits liquid films in the presence of a controlled environment. In FIG. 4A , 407 indicates layer printing and / or fabrication in a first controlled environment, and 490 indicates subsequent processing in either the first or second controlled environment, both of which are maintained to protect the deposited photosensitive materials from degradation due to exposure to oxygen, moisture, and other contaminants until the materials are cured or otherwise processed to become permanent or semi-permanent. Upon introduction, the substrates are first aligned with the printer reference frame, as described elsewhere herein, and optionally, height measurements are taken to correct for substrate-to-substrate variations, 411. For example, out-of-alignment substrates can be repositioned by a mechanical handler, and precision position transducers can be used to adjust the substrate's position and / or orientation. Additionally, print recipes or print parameters can be adjusted in software to correct printing to accommodate x, y, and z misalignments. Optionally, height variations can be factored into deposition parameters (including substrate position and / or printhead height and / or software parameters and nozzle control), which can then be individually adjusted for specific substrates (at 413 / 414) to provide more precise control of printing. Similar to an online process, in one embodiment, this adjustment is automated before printing begins, as indicated by 415 and 416; in others, height is dynamically measured and used for dynamic correction. Printing then occurs according to the desired parameters, as indicated by 417. Following printing, the deposited film (e.g., a continuous liquid coat) is processed, such as by drying or curing, as indicated by 424. In one embodiment, this can be performed directly by a tool carried by the printhead transport mechanism, such as a carried ultraviolet light source.In other embodiments, such treatments are performed in different chambers (eg, containing the same or different atmospheric contents, as previously described).

[0066] As indicated by numerals 420 and 421, deposition of any of these layers can be performed in a controlled environment, i.e., an atmosphere controlled in some manner to exclude unwanted materials or particulates. In such circumstances, the printer can be controlled to completely enclose the gas chamber and perform printing under such control. In one embodiment, the atmospheric content differs from that of normal air, for example, containing increased amounts of nitrogen and noble gases relative to the atmosphere. The automated calibration, alignment, and measurement techniques described herein are additionally performed in such a controlled atmosphere (i.e., in an automated manner without the need for human operator involvement). Numerals 425, 426, 427, 428, and 429 indicate many additional process options, such as the use of two different controlled atmospheres (425) (e.g., one for printing and one for processing), the use of liquid ink in the deposition (printing) process (426), the fact that deposition can occur on a substrate with a basic geometry (e.g., deposition structure) or on a curved or otherwise contoured substrate (427), the fact that encapsulation and / or printing leaves selected layers exposed at specific locations on the substrate, e.g., electrodes (428), and additional process controls (429) for adjusting printing parameters in the region of layer boundaries, e.g., to print specific edge profiles (e.g., this is particularly advantageous for tailoring the edges of encapsulation or other "blanket" layers). Other additional techniques can also be combined with these.

[0067] Once the desired layers have been processed into a permanent or semi-permanent form, the particular substrate can be returned to the printer or connected manufacturing equipment to receive (or process) additional layers, or it can be removed from the controlled environment, as indicated by numeral 431, for further processing or finishing.

[0068] As mentioned above, in precision environments such as those just described, particularly for pixel fabrication (e.g., where picoliter-scale droplets are precisely placed into micron-scale (e.g., tens of microns in width and length) fluid “wells” and a planned volume of deposition fluid (e.g., 50 picoliters) must be delivered to the wells without significant variation), accurately calibrating height and measuring and correcting for height variations (either statically or dynamically) can be important. For example, in systems where nozzles or printheads vary in height relative to other nozzles or printheads by tens to hundreds of microns, position errors caused by height variations can be on the order of 20% or more of the height error or variation. This can be unacceptable for many applications. With this in mind, FIG. 4B illustrates an alternative height calibration and measurement system 441 based on the use of high-precision sensors. Such systems generally offer greater accuracy, are more amenable to fully automated control, and are capable of performing both high-speed and on-the-fly measurements to provide dynamic understanding of height variations. FIG. 4B shows several elements, including print head (PH) camera assembly 443, gripper camera assembly 445, print head 455, reference block 471 fixed to the print head assembly, print head laser sensor 461, gripper laser sensor 463, and gauge block 467 (used for calibration).

[0069] The operation of the various elements shown in FIG. 4B is as follows: First, the PH camera 443 and the gripper camera assembly 445 are each optically aligned in the manner previously described. That is, each camera is used to image a reticle (451 / 451′) along a respective optical path 449 and 450. Reference numerals 451 and 451′ can refer to the same common fiducial mark (e.g., relative to a common reticle) or to respective fiducial marks (e.g., having a known positional relationship). However, unlike some of the previously described embodiments, the exact focus and the exact focal lengths 449 / 450 of the optical paths are not closely related to the calibration results. That is, as mentioned above, the digital image output of each camera is fed to a frame grabber and compared, but the image processing software simply identifies the positional overlap of the reticle (e.g., crosshairs) from each image and adjusts the two transport paths until their respective positions are aligned (e.g., the reticle is fixed to the PH camera 443, and the gripper camera assembly 445 is moved to center the reticle in its field of view). Note that the illustrated cameras each include a coaxial light source 447 and a beam splitter 448 that directs light from the light source to illuminate the reticle and provide return light to the imaging sensors of cameras 443 / 445. As mentioned above, each camera assembly may also feature dual low- and high-resolution imaging capabilities and an electronically controlled autofocus mechanism 446 that is controlled by the image processing software (or other software) to acquire a clear image of the reticle. The image processing software detects the correct alignment of the camera, as described above, and the measurement system captures the exact position of each transport path that corresponds to this alignment and "zeroes" or otherwise defines the origin of the coordinate system.

[0070] Once alignment in the x- and y-directions is achieved, the transport system of the manufacturing equipment is controlled to move the PH camera 443 to roughly “detect” the gripper z-axis height high precision sensor 463 in the x- and y-coordinates, and conversely, the transport system is also moved to cause the gripper camera system 445 to “detect” the print head assembly z-axis height high precision sensor 461 in the x- and y-coordinates. As previously mentioned, in this embodiment, each high precision sensor may be a laser sensor oriented to measure distance, e.g., height. To perform the localization function, an alignment feature (a bore, protrusion, or other detectable height feature) exhibiting a detectable height profile is positioned relative to each camera so that it can be imaged by both the camera and the z-axis laser sensor. For example, in one embodiment, images from the low-resolution camera or gripper camera system 445 are used to search for or find a recognizable opening or protrusion (e.g., which may be attached to the print head assembly, but alternatively may be attached anywhere that can be imaged by both the gripper camera system and the gripper z-axis laser sensor 463) via automated image processing. Once the feature is found and centered, a high-resolution camera or image from the same camera system (e.g., the gripper camera system) is used to more precisely determine the location of the recognizable feature or protrusion, and image processing software then stores its x- and y-coordinates. With the coordinate system for the printer already established, the transport system roughly positions the gripper z-axis laser sensor 463 at a location where it can scan the recognizable opening or protrusion, which is used to establish the precise midpoint of the recognizable opening or protrusion. A precise x- and y-coordinate point is associated with this point, and based on the difference between the x- and y-coordinate point of the recognizable opening determined by the camera and the x- and y-coordinates of the center point of the recognizable opening or protrusion provided by the z-axis laser sensor, the precise x- and y-distance between the gripper z-axis laser sensor 463 and the gripper camera system 445 is derived and stored for use in various calibrations.Conversely, the same process is then performed using the PH camera 443 and print head z-axis laser sensor 461 to detect common features and protrusions and determine and store the precise relative x-y distance between the print head z-axis laser sensor 461 and the print head camera system 445. This distance calibration can be used to facilitate the dynamic and other measurements shown above. For example, to measure the height at any portion of a substrate during runtime, the transport system of the manufacturing equipment is simply driven to position the print head z-axis laser sensor 461 over any point on the substrate and take a height reading. Conversely, as desired (i.e., typically in offline processing or between substrates), the system can position the gripper z-axis laser sensor 463 to image any desired feature associated with the print head.

[0071] It should be noted that although a laser sensor has been described, any high precision sensor may be used, subject to appropriate application in relation to the sensing technology in question, within the ability of one skilled in the art. With regard to the example of a laser-based sensor referred to above, one sensor found to be suitable for the described purposes is a laser sensor available from MICRO-EPSILON, USA, with offices in Raleigh, North Carolina. A suitable sensor is one capable of measuring height variations within a range of 3 millimeters or less, with sub-micron measurement accuracy.

[0072] The right side of FIG. 4B shows that each laser sensor 461 / 463 measures the height ("h9" / "h9") using a beam directed at an angle 464 / 465. 10Note that the referenced sensors are shown to detect the surface roughness ("h") of the substrate. In this regard, the referenced sensors preferably operate using reflectometry. For example, since the deposition, in one embodiment, is performed on a glass or transparent substrate, a "head-on" measurement would potentially introduce unwanted reflection noise caused by the refractive index of the imaged material. To address this, each sensing laser is preferably of a type that directs light at an angle (e.g., "α") to minimize backscatter and unwanted reflections. The right side of FIG. 4B also shows a gauge block 467 used for calibration. The gauge block 467 typically features a protrusion 469 of precisely known thickness ("h") as well as a body 468 that can be attached to a system. In this regard, as mentioned earlier, specific tools can be selectively used for specific calibration purposes during offline calibration (e.g., engaged manually and / or by articulated and / or robotic engagement, or attached in a fixed position that does not interfere with online manufacturing). The gauge block 467 is one such tool. In one embodiment, the tool is mounted at a known location relative to the printer support table or chuck, either permanently outside the substrate transport path (e.g., at an xy location still reachable by either laser sensor 461 / 463), or at a location that can be selectively robotically engaged and disengaged, e.g., via another dynamic mount. In this regard, the exact thickness is a known value, such as "1.00 microns," and is located at a location that can be sensed by each laser sensor. Each laser is sequentially moved to the appropriate location by the software as part of a calibration routine to measure the height between the laser sensor and the corresponding side protrusion, e.g., heights "h9" and "h 10 Since the thickness of the protrusion, "h8", is precisely known, the calibration software calculates the distance between the two laser sensors, e.g., "h9" + "h 10" + 1.00 microns can be quickly calculated (this is similar to calculating "h4" + "h5" in FIG. 2B, except that it can be done almost instantly once the laser sensor is moved to the correct position. In fact, like the other measurements herein, these measurements are preferably taken in very close succession to minimize any measurements that may affect temperature or other driving forces). Note also that this measurement scheme is typically substantially more accurate than the previously described scheme because it does not depend on achieving "exact focus" (i.e., which is subjective, time-consuming, and otherwise potentially subject to error).

[0073] Many of the measurements that are then made are similar to those described above. For example, a gripper laser sensor is used to image the orifice plate 457 that rests on the bottom of the printhead 455, and a height measurement (e.g., "h6" in FIG. 2B, except that this measurement is obtained from the gripper laser sensor 463) is developed. However, since the distance between the laser sensors is precisely known, the calibration software can quickly calculate the difference in height of the printhead orifice plate 457 relative to the printhead laser sensor 461 by subtracting the height of the printhead orifice plate 457 from the distance between the sensors, i.e., "h9" + "h 10 " + 1.00 microns. This value is then stored and, again, used to enable accurate measurement at any time (e.g., dynamically, during printing, automatically) of the height of the printhead orifice plate 457 above the substrate 459, for example, by simply measuring the substrate with the printhead laser sensor 461 at the desired x, y coordinate point and subtracting the stored height difference of the printhead orifice plate 457 relative to the printhead laser sensor 461. Again, dynamic focusing is not used to measure the height, and further, the measurement is instantaneous because the sensors employed are precision devices and provide instantaneous readings.

[0074] FIG. 4B shows a fiducial block 471 and associated fiducials 472 fixed to the printhead assembly. Simply put, these items are additionally used to provide a fixed reference point for the printhead assembly. During initial and / or other orifice calibrations featuring the gauge block 467, the distance from the gripper laser sensor 463 to the fiducial 472 is also advantageously measured and saved by the gripper laser sensor 463 at this time. This measurement and stored value can be used to provide process shortcuts during subsequent measurements. For example, with respect to inkjet printer-based manufacturing equipment, printheads and / or ink sticks may be frequently replaced or changed, each potentially indicating new height differences and possible errors that should be measured and subsequently incorporated into printing, printer adjustments, and print process adjustments. The use of the fixed fiducial block 471 and associated fiducials allows, for example, the use of a second, shortened calibration process rather than repeating all of the steps just described. During swap, the gripper's laser sensor 463 can image both each new printhead orifice plate and the fiducial 472 and use it to derive the height difference. This height difference can then be used to immediately derive the new printhead height by referencing the difference against the fiducial (and the previous printhead height difference relative to the fiducial). Thus, the system can immediately derive a new printhead height value based on a shortened calibration sequence without the need for gauge blocks or other measurements, further improving device uptime. Note that not all embodiments require this additional technique.

[0075] FIG. 4C shows a method 471 featuring some of the measurement and other steps just described. First, as indicated at 473, the two transport paths are aligned relative to a common reference point, e.g., using the printhead and gripper cameras and reticles as previously described. This establishes a coordinate system at 475, and the system finds the x and y coordinates for a first high-precision sensor, e.g., a first laser. Once this information is known, that high-precision sensor is then precisely positioned relative to a fiducial (e.g., gauge block 467 in FIG. 4B) and used to obtain height measurements relative to that fiducial at 477. The system also finds the x and y coordinates for a second high-precision sensor, e.g., a second laser (e.g., mounted relative to a different transport path), at 478. Once this information is known, the second high-precision sensor is precisely positioned relative to a fiducial (e.g., gauge block 467 in FIG. 4B) and used to obtain height measurements relative to that fiducial at 480. Based on these measurements, a processor operating with the assistance of calibration software calculates (481) the height difference between the two high-precision sensors (e.g., from the first laser to the second laser), allowing the height measurements from the two high-precision sensors to be accurately related to each other. As previously mentioned, this is expressed in terms of the equation "h total " = "h8" + "h9" + "h 10" (483). As previously indicated, a fixed reference, such as reference 472, can be additionally provided and measured, and the resulting measured heights can be stored for future use, as indicated by reference numerals 485, 487, and 488. One of the high-precision sensors (e.g., associated with one transport axis, such as a gripper, or another sensor, such as a camera) is used to detect the deposition source, as indicated by reference numeral 491, and a second high-precision sensor is used to measure the distance between it and the deposition source (as indicated by reference numeral 492). The height difference exhibited by the deposition source is thereby determined (493), for example, relative to the distance between the two sensors or a fixed reference. Optionally, the first high-precision camera is now used (e.g., dynamically or otherwise) at reference numeral 495 to measure the height relative to a deposition target, such as a substrate. Finally, as indicated by reference numeral 497, the system measures and stores the height difference between the deposition source and the deposition target, and takes appropriate corrective / adjustment action, as indicated by reference numeral 498.

[0076] Reflecting some of the elements and structures just described, in one embodiment, z-axis measurements can be readily performed with greater precision and accuracy than with the previously described embodiment. Optionally, the manufacturing system is initially calibrated to identify an xy or similar coordinate system. A high-precision sensor associated with each transport path is then engaged and used to measure the height difference between two high-precision sensors. These two sensors, through a series of measurements and the additional use of certain features as described above, can both be used to provide a rapid, accurate measurement of the height difference between a deposition source and a target (e.g., between a tool and a target) in the manufacturing system. This process can be fully automated, avoiding potentially subjective and time-consuming processes and potential limitations on resolution based on determining precise focus. When combined with any xy calibration and alignment scheme and accurate identification of the sensor position relative to the xy coordinates, the disclosed technique enables automated, accurate z-axis measurements that are both instantaneous and dynamic, and can be used to measure any portion of a deposition target (or other element of manufacturing or production equipment).

[0077] 5A to 5E are used to provide some additional information regarding even more detailed embodiments.

[0078] First, Figure 5A shows a portion of a manufacturing apparatus 501 that includes a vacuum bar 503 (used to engage a substrate) and a printer support table or chuck 505. The vacuum bar forms part of a gripper, and both the gripper (e.g., gripper frame 506) and vacuum bar 503 move back and forth in the general direction of double arrow 507 to transport the substrate. The vacuum bar is coupled to the gripper frame 506 by a set of linear transducers (only one (509) is shown in the figure), which articulate the vacuum bar and substrate via linear drive in the direction of double arrow 510. Differential mode drive of these transducers can rotate the substrate about a levitation pivot point 511 (e.g., which is used to perform the selective substrate position corrections discussed above), while common mode drive of these transducers can linearly offset the substrate in the direction of double arrow 510. The illustrated manufacturing apparatus 501 also shows an upward-facing camera or gripper camera system comprising a camera 513, a light source 515, and an associated heat sink 517. The light source and previously mentioned beam splitter (not shown but located in the camera's optical path at approximately the optical axis 521) are used to direct light from the light source upward through an aperture 523 in the gripper frame to provide the previously mentioned optical measurements. The gripper frame 506 also mounts a high-precision sensor 525, such as the previously mentioned laser sensor by MICRO-EPSILON, which is oriented to point upward and measures the height of the object through an aperture block 527. This aperture block can be used for selective attachment (by a robot or otherwise) of a gauge block 528, such as a magnetic plate forming part of a dynamic mount for the previously referenced purposes. Among other things, gripper frame 506 is also shown to mount calibration block 529 that provides a recognizable aperture / protrusion 530 for imaging by the printhead camera (not shown in FIG. 5A) and by a high-precision camera (also not shown in FIG. 5A) attached to the printhead.This calibration block and associated reference structure (fiducials) described above are used to precisely identify the position, in xy coordinates, of the printhead-mounted high precision sensor relative to the printhead-mounted camera.

[0079] FIG. 5B shows a camera assembly 541 mounted by the printhead carriage (not shown). This assembly includes a downward-facing oriented camera 543, a light source 545, and an associated heat sink 547. As previously described, a beam splitter (roughly at 549) in the camera's optical path directs light from the light source downward through lens 551 and receives the returned image light that is detected by camera 543. Also shown is a dynamic mount 553 with a permanently attached "L-bar" 554 that provides a repeatable connection with a removable carrier 555. This removable carrier supports a lens-mounted reticle 556, as previously referenced. During calibration, the camera images the reticle (at the same time that the upward-facing camera 513 of the assembly in FIG. 5A images this same reticle 556 from below). As previously mentioned, the dynamic mount allows for repeatable installation and removal of the reticle lens assembly for purposes of defining an x-y coordinate system as well as other measurement tasks, as referenced above. In one embodiment, the dynamic mount can be recalibrated from time to time using adjustment screws 557, either by a human operator or (in one embodiment) electronically, during calibration of the reticle's position relative to the imaged target. Figure 5B also shows calibration block 558, which is used to provide another visible aperture / protrusion 559 for imaging by the gripper camera system (i.e., by camera 513 of Figure 5A) and the gripper-mounted precision sensor (i.e., the precision camera of Figure 5A). This calibration block and associated fiducials, as previously mentioned, are used to precisely identify the position of the gripper-mounted precision sensor relative to the gripper-mounted camera in terms of x-y coordinates.

[0080] 5C provides an enlarged perspective view of reticle lens assembly 561, also seen in FIG. 5B. This assembly includes carrier 555, as described above, which also provides part of a dynamic mount for providing rapid and precise (e.g., manual or robotic) installation and removal or other positioning / engagement of the reticle lens assembly. This assembly also includes optical lens 563 with reticle 556 mounted thereon, the precise positioning of which is infrequently fine-tuned by manual adjustment of alignment / mounting screws 567. As previously mentioned, the reticle (assembly) is advantageously designed for rapid (e.g., robotic) installation and removal or other automatic positioning / engagement to provide a fully automated calibration and measurement process.

[0081] FIG. 5D provides a close-up view of gauge block 581. This block consists of a body 583, which in turn provides one half of a dynamic mount adapted for easy, repeatable attachment and detachment and / or other selective engagement or use. More specifically, this assembly is selectively engaged to position protrusion 585 directly in the optical path of the gripper height sensor for selective attachment or detachment relative to the dynamic mount's reciprocal memory formed, for example, by aperture block 527 of FIG. 5A. Naturally, many alternative designs exist. FIG. 5D also shows two clamping screws 587 for the protrusion. Although not shown in FIG. 5D, the dynamic mount features adjustable side plates that can be used to provide infrequent manual fine adjustment of the precise protrusion position relative to the mounting of the gauge block by the gripper frame.

[0082] Finally, FIG. 5E shows an example of a reference block 591 used to provide an example calibration block for various cameras and high-precision sensors. In this particular example, the calibration block may be the device exactly as shown by reference numeral 529 in FIG. 5A. (The design of calibration block 472 in FIG. 4B is similar.) The calibration block is “L-shaped” and includes mounting plate and target plate portions 592, 593, the latter providing a calibration reference for the x-y distance between the camera and the associated high-precision sensor. A polished sheet steel plate (e.g., stainless steel or other surface) 594 is used to provide a highly reflective surface for imaging by the high-precision sensor. Briefly, as previously described, a protrusion / aperture (in this embodiment, an aperture) 595 is imaged first by a low-resolution camera, second by a high-resolution camera, and finally by a high-precision sensor associated with a given one of the transport axes. A position read from a position feedback system associated with the transport axis is taken at the location where the camera and its associated high-precision camera detect the center of this aperture 596. These positions are then used to calculate the x,y offset between the two measurement devices. Note that aperture 595 advantageously does not represent a complete bore through the target plate portion; a complete bore may give inconsistent (i.e., noisy) sensor readings. Rather, what is needed is for the target plate portion to provide a target that provides a clean, highly accurate sensor signal discrimination in a manner that allows for bore location and bore center identification. As indicated by numerals 597 and 598, the target plate portion can provide additional, variable-sized apertures for additional calibration functions.

[0083] By providing calibration and measurement standards in the manner described above, the elements shown in Figures 5A-5E provide an effective, highly accurate means of determining multi-axis (e.g., x, y, and z) position calibration and measurement in precision manufacturing systems. As previously indicated, this provides finer control over deposition parameters, such as the intended landing location of deposited material. In one embodiment, these techniques can be applied to facilitate accurate drop placement with industrial split-axis printing systems.

[0084] It should be noted that the disclosed technology offers many options. First, while some embodiments have been described based on a printer (e.g., an inkjet printer), the technology described herein is not so limited. To give one example, the described technology can be applied to manufacturing systems that do not include printers (e.g., that otherwise require precise position control). The teachings described herein can also be applied to any type of production or manufacturing equipment where high precision is desired or required, including equipment for positioning tools, processing equipment, deposition sources, inspection equipment, and similar devices. The technology described herein is also not limited to split-axis systems; for example, while some embodiments described above feature separate transport mechanisms for the x and y dimensions, the technology described herein can be applied to other types of position-articulated systems (e.g., via gimbals or other nonlinear transport paths, or systems providing transport across multiple dimensions) or where different degrees of freedom are at issue. Third, while the described technology has been presented in the context of an assembly-line process, the application of the described technology is not limited to this environment. For example, they may be implemented in any type of manufacturing system, positioning system, non-industrial printer, and potentially applied to other types of systems or devices.

[0085] Without limitation to the above, in one embodiment, adjustments are made offline, once to a production or manufacturing machine or printer. In other embodiments, adjustments can be made on a substrate-by-substrate or product-by-product basis to correct for misalignment or distortion. In yet other embodiments, measurements can be taken dynamically and used to make adjustments in real time. It will be apparent that many variations exist without departing from the inventive principles described herein.

[0086] In the foregoing description and accompanying drawings, specific terminology and drawing symbols have been set forth to provide a thorough understanding of the disclosed embodiments. In some instances, the terminology and symbols may imply specific details that are not necessary to practice those embodiments. The terms "exemplary" or "embodiment" are used to express an example, not a preference or requirement.

[0087] As noted above, various modifications and variations can be made to the embodiments presented herein without departing from the broader spirit and scope of the present disclosure. For example, a feature or aspect of any embodiment can be applied, if practicable, in combination with any other embodiment or in place of a corresponding feature or aspect thereof. Thus, for example, not all features are shown in each of the drawings, and a feature or technique shown according to an embodiment of one drawing should be assumed to be optionally employable as an element of or in combination with a feature of any other drawing or embodiment, even if not specifically mentioned in this specification. Thus, the present specification and drawings are to be understood in an illustrative, not a limiting sense.

Claims

1. A method comprising: providing a split-axis printer including a print head transport path that guides a print head, and a support guide that is disposed at a height apart from the print head transport path and that guides a gripper that can engage a substrate, the print head transport path and the support guide extending in directions that intersect with each other; aligning the print head transport path and the support guide to a common reference point by capturing an image of an alignment mark with at least one of a first camera coupled to the print head transport path and a second camera coupled to the support guide; using the second camera to acquire a first image of a first sensor, the first sensor being the printhead height sensor; using the first camera to acquire a second image of a second sensor, the second sensor being a height sensor of the gripper; determining a position of the first sensor based on the first image; determining a position of the second sensor based on the second image; and determining a distance from the print head to the substrate engaged in the support guide using the first sensor, the second sensor, or both.

2. Determining the distance from the print head to the substrate comprises: Detecting a first distance from the first sensor to a position reference using the first sensor; using the second sensor to detect a second distance from the second sensor to the position reference; The method of claim 1 , wherein determining the distance from the print head to the substrate is based on the first distance and the second distance.

3. The method of claim 2 , wherein at least one of the first sensor and the second sensor is a laser sensor.

4. The method of claim 3 , wherein the laser sensor is positioned at an angle relative to the position reference.

5. The method of claim 4 further comprising calculating a distance from the first sensor to the second sensor.

6. The method of claim 5 , further comprising storing the first distance and the second distance in a computer system.

7. the position reference is a gauge that is disposed between the first sensor and the second sensor and has a known thickness in the height direction; 6. The method of claim 5, wherein calculating the distance from the first sensor to the second sensor comprises adding the distance from the first sensor to the gauge, the distance from the second sensor to the gauge, and a known thickness of the gauge.

8. The method of claim 1 , wherein the alignment mark is a reticle coupled to the first camera.

9. Determining the position of the first sensor includes: focusing the second camera on a feature of the first sensor; calculating a distance from the second camera to the first sensor based on a focal length of the second camera; Determining the position of the second sensor includes: focusing the first camera on a feature of the second sensor; and calculating a distance from the first camera to the second sensor based on a focal length of the first camera.

10. 10. The method of claim 1, further comprising using the second sensor to measure a distance between the second sensor and a second position reference that provides a fixed reference point for the print head.

11. A method comprising: providing a split-axis printer including a print head transport path that guides a print head, and a support guide that is disposed at a height apart from the print head transport path and that guides a gripper that can engage a substrate, the print head transport path and the support guide extending in directions that intersect with each other; aligning the print head transport path and the support guide to a common reference point by photographing an alignment mark with at least one of a first camera coupled to the print head transport path and a second camera coupled to the support guide; using the second camera to determine the position of a first sensor, the first sensor being the printhead height sensor, relative to the common reference point; using the first camera to determine the position of a second sensor, the second sensor being a height sensor of the gripper, relative to the common reference point; determining a distance from the print head to the substrate engaged in the support guide using the first sensor, the second sensor, or both.

12. further comprising disposing a gauge having a known thickness in the height direction between the first sensor and the second sensor; Determining the distance from the print head to the substrate comprises: Detecting a first distance to the gauge using the first sensor; and detecting a second distance to the gauge using the second sensor; 12. The method of claim 11, wherein determining the distance from the print head to the substrate is based on the first distance, the second distance, and a known thickness of the gauge.

13. The method of claim 12 further comprising detecting a distance from the second sensor to a reference block that provides a fixed reference point for the printhead.

14. the alignment mark is a reticle coupled to the print head transport path; The method of claim 11 , wherein aligning the print head transport path and the support guide to the common reference point includes imaging the reticle using the second camera.

15. The method of claim 14 , wherein the support guide is a gripper transport path.

16. determining a position of the first sensor relative to the common reference point using the second camera includes imaging a first alignment feature of the first sensor using the second camera; 12. The method of claim 11, wherein determining the position of the second sensor relative to the common reference point using the first camera includes imaging a second alignment feature of the second sensor using the first camera.

17. aligning the first sensor with the second alignment feature to determine a distance between the first camera and the first sensor; and aligning the second sensor with the first alignment feature to determine a distance between the second camera and the second sensor.

18. A method comprising: providing a split-axis printer including a print head transport path that guides a print head, and a support guide that is disposed at a height apart from the print head transport path and that guides a gripper that can engage a substrate, the print head transport path and the support guide extending in directions that intersect with each other; aligning the print head transport path and the support guide to a common reference point by imaging a reticle using at least one of a first camera coupled to the print head transport path and a second camera coupled to the support guide; using the second camera to acquire a first image of a first sensor feature, the first sensor being a height sensor of the printhead; using the first camera to acquire a second image of a feature of a second sensor, the second sensor being a height sensor of the gripper; determining a position of the first sensor relative to the common reference point based on the first image; determining a position of the second sensor relative to the common reference point based on the second image; determining a height of the first sensor relative to a reference; determining a height of the second sensor relative to the reference; determining a height difference between the first and second sensors; and determining a distance from the print head to the substrate engaged in the support guide using the first sensor, the second sensor, or both.

19. Determining the distance from the print head to the substrate comprises: measuring a height from the second sensor to the print head; determining a height difference between the print head and a first sensor; measuring a height from the first sensor to the substrate; and calculating a distance from the print head to the substrate.

Images