WO2010109457A1

WO2010109457A1 - Method and apparatus for print unit inspection and calibration

Info

Publication number: WO2010109457A1
Application number: PCT/IL2010/000240
Authority: WO
Inventors: Ran Asher Peleg; Hanan Gothait; Ofir Baharav
Original assignee: Xjet Ltd
Priority date: 2009-03-23
Filing date: 2010-03-23
Publication date: 2010-09-30
Also published as: TW201040029A

Abstract

A system and method for inspecting a printing system is provided. A first part of a pattern and a test pattern may be printed on a substrate. In some embodiments, the substrate may be rotated. An image of the test pattern may be acquired. An acquired image of the test pattern may be analyzed. An action may be performed based on an analysis of an image of the test pattern. A second part of a pattern may be deposited and may cover some or all of the test pattern.

Description

METHOD AND APPARATUS FOR PRINT UNIT INSPECTION AND

CALIBRATION

BACKGROUND OF THE INVENTION

[0001] Materials deposition systems such as inkjet or aerosol jet are considered one of the promising methods for selective fabrication of thin layers in the printable electronics industry and have a potential of becoming the technology of choice for fabricating front contacts in solar photovoltaic cells. This technology has several advantages over the traditional methods, for example, it does not require contact with the fragile surface of solar cells, has better resolution, and offers higher productivity.

[0002] A "drop on demand" inkjet technology works by selectively ejecting fine droplets of ink onto the printed media by a plurality of nozzles which can be turned on or off. The printed pattern is formed by scanning a printhead (a print unit containing several dispensing nozzles) relative to the substrate; a position of the dot on the substrate is controlled by controlling which nozzle is forced to eject droplets, and the timing of drop ejection. By controlling a timing of ejection and a selection of ejecting nozzles and by further synchronizing these parameters with a translation of a substrate, a desired pattern may be formed on the substrate. The preferred type of scan for inkjet systems for mass manufacturing of solar cells comprises conveyor processing, that is, a linear scan along a single axis, referred to as the "scan axis". In this type of scan the solar cell is scanned under the print unit (that may comprise one or more printheads) in a linear motion while the printheads remain stationary during the scan.

[0003] A difficulty that may be common to all deposition printers may be associated with faulty nozzles which, at the extreme cases, can be manifested by total occlusion of the orifice, thus completely blocking the ejection of droplets. More often however, faulty nozzles will be characterized by adverse printed features, e.g., wrong droplet size and/or location. Another problem may relate to a misalignment or generally a position of a printhead which may cause a pattern to be misplaced, distorted or otherwise incorrect. [0004] Although methods and systems known in the art may enable off line inspection and service of print units, such off line methods may only be performed when the system is not printing or is otherwise idle but may not be performed without impeding production.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with objects, features and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanied drawings in which:

[0006] Fig. 1 shows an exemplary pattern comprising narrow finger lines and wider bus bars according to embodiments of the invention;

[0007] Fig. 2 shows an exemplary printing system according to embodiments of the invention;

[0008] Fig. 3 shows exemplary pattern comprising test patterns according to embodiments of the invention shows exemplary pattern comprising test patterns according to embodiments of the invention;

[0009] Fig. 4 is a flowchart diagram illustrating a method for inspecting and servicing print units according to embodiments of the present invention; and

[0010] Fig. 5 shows an exemplary printing system according to embodiments of the invention.

[0011] It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements. DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0012] In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those of ordinary skill in the art that the invention may be practiced without these specific details. In other instances, well-known methods, procedures, components, modules, units and/or circuits have not been described in detail so as not to obscure the invention.

[0013] Embodiments of the invention are directed to a printing system having an inspection system where the inspection system may operate simultaneously with a printing process. Embodiments of the invention are further directed to a system and method for online or on-the-fly inspection of print units. According to embodiments, jetting nozzles or other dispensing units that participate in a current, ongoing print job may be inspected online, on-the-fly or otherwise at the same time a print job is in process. It will be understood that any applicable dispensing units, e.g., inkjets, aerosol jets or any other dispensing systems may be inspected and serviced as described herein. Likewise, embodiments of the invention are not limited by the type of the material dispensed, printed or deposited.

[0014] Although the discussion herein will mainly refer to printheads that comprise a plurality of jetting or other type of nozzles, it will be understood that any applicable arrangement or assembly may be used for positioning a plurality of print units and/or material deposition devices with respect to a substrate. Although the discussion herein will mainly refer to a deposition of metallization lines on photovoltaic solar cells, it will be understood that online or on-the-fly inspection of print units used for deposition of any applicable pattern and/or any suitable material on any applicable substrate may be performed as described herein.

[0015] According to embodiments of the invention one or more test patterns may be printed in reserved areas on the surface of the substrate in a first scan. In a particular case, reserved areas where a test pattern is printed may be areas where material is deposited in a subsequent or second scan. An image of the test patterns may be acquired, e.g., using a digital camera or any suitable imaging system. An analysis of the acquired image may be performed and used to determine faults, e.g., faulty nozzles or misaligned printheads. In some embodiments of the invention, depositing the test pattern and the first and second parts of the pattern, acquiring and analyzing the image may be performed during a continuous translation of the substrate in a single scan direction.

[0016] Reference is now made to Fig. 1 that shows an exemplary metallization pattern that may be deposited on a substrate 100. For example, the substrate may be a solar cell. As shown, the pattern may comprise a plurality of finger lines 101 and a plurality of bus bars 102. Typically, the finger lines 101 may be deposited first, e.g., by one or more nozzles in a first set of printheads positioned or arranged across a scan axis. A nozzle array comprising a finger printhead is typically arranged along the scan axis. After the finger lines 101 are printed or deposited, substrate 100 may be rotated by ninety degrees (90°) and, maintaining the scan direction, scanned by a second set of printheads that deposit bus bars 102. A nozzle array comprising a bus printhead is typically arranged at a small angle along the scan axis. For example, a linear scan, non-contact ^"material deposition system implementing embodiments of the invention may deposit the pattern shown in Fig. 1. In another embodiment, rotation of substrate 100 is not included. In that case, the bus heads with their nozzle arrays are positioned in a cross-scan orientation.

[0017] In another embodiment, instead of rotating a substrate, the substrate may be translated in a first direction when the finger lines are deposited, and in a second, orthogonal direction, when the bus bars are deposited.

[0018] The pattern 100 shown in Fig. 1 is an exemplary pattern that, for the sake of clarity and simplicity, will be referred to herein. However, it will be understood that embodiments of the invention may be applied to various other patterns, in particular, any pattern having intersecting lines or other shapes may be applicable.

[0019] Reference is now made to Fig. 2 that shows an exemplary printing system 200 according to embodiments of the invention. For example, system 200 may be an inkjet printing system used for fabrication of front contact metallization of photovoltaic (PV) solar cells. As shown, system 200 may comprise a processing unit 260, a control unit 270, printheads 210 and 250, a substrate mounting and translation unit 220, a rotational unit 223 and an image acquisition unit 240. As shown, system 200 may deposit patterns 222, 224 and 251 on a substrate 221. Control unit 270 may be operatively connected to printheads 210 and 250, processing unit 260, image acquisition system 240, rotational unit 223 and/or any other component of system 200.

[0020] Control unit 270 may be operatively connected to a conveyor (not shown) or other translation unit that translates substrate 221 (e.g., by translating unit 220) from printheads 210 through image acquisition unit 240 to printheads 250. Accordingly, any relevant data, information or parameters related to a printing on substrate 221 may be available to control unit 270. For example, a velocity, location, position or orientation of substrate 221 may be known to control unit 270.

[0021] Control unit 270 may control operation of nozzles in printheads 210 and 250. For example, control unit 270 may control the period during which a specific nozzle in a specific printhead will deposit material on substrate 221. Accordingly, control unit 270 may cause any pattern including a test pattern to be printed on substrate 221 by selected nozzles or units. Any selection of print units, printheads or specific nozzles may be made by control unit 270. for example, a first set of units or nozzles may be selected to print a first part of a pattern, a second and third sets may be selected and/or caused to print a second and third parts of a pattern and a fourth set (that may be the set to be inspected) may be selected and caused to print a test pattern.

[0022] For example, in some cases, idle nozzles may be inspected. Idle, redundant or backup nozzles (or other printing or dispensing components) may be any nozzles in a print unit that do not actively or currently participate in printing. Such idle, backup or redundant nozzles may be reserved as backup, and, according to embodiments of the invention, may be made or designated active on-the-fly or in realtime, while a print job is in progress. Likewise, a print unit such as a printhead may be Idle, redundant or backup, similarly, based on an inspection as described herein, an idle printhead may be made or designated active on-the-fly or in realtime, while a print job is in progress. In some embodiments, only idle nozzles may be selected to print a test pattern. In other cases, e.g., when inspecting aspects such as an orientation, position or velocity of a substrate, active nozzles may be selected to print test patterns. Control unit 270 may cause service actions to be performed. For example, control unit 270 may instruct actions such as priming a jet, setting parameters such as temperature, pressure level or setting particle size of a jet to be performed. In other cases, an action may comprise designating active nozzles as inactive and/or designating or making idle nozzles, printheads or print units active. Accordingly, embodiments of the invention may enable on-the-fly or realtime replacement of faulty nozzles by backup, redundant or idle nozzles.

[0023] As shown, a pattern comprising finger lines 222 and test patterns 224 may be deposited on a substrate 221. The pattern deposited on substrate 221 may further comprise bus bars 251 that may be printed by printheads 250. System 200 may be an inkjet system utilizing a linear scan technique. In this type of scan, the substrate is scanned under the printheads in a linear motion while ink is discharged from inkjet nozzles. The printheads (210 and 250) may remain stationary during the scan but may be provided with translation means for alignment or positioning. Translation unit 220 may be a moving table (e.g., connected to a conveyor) for transporting substrate 221 in a direction referred to as the scan axis, or the x axis as shown by 280. Translation unit 220 may be provided with a sensor, such as for example an optical encoder, which may track the motion of translation unit 220 with a high degree of precision and may provide feedback to control unit 270. The orientation of the substrate may be similarly tracked or determined by control of, and feedback from, rotational unit 223. Printheads 210 and 250 may each include a plurality of inkjet nozzles that may be arranged along these printheads. As shown, printheads 210 may be arranged or aligned along the scan direction such that each of thin finger lines 222 may be printed by one or more nozzles. To produce wider bus lines 251, printheads 250 may be position at a predefined angle with respect to the scan axis such that a number of nozzles may deposit a bus bar having a corresponding predefined width.

[0024] According to embodiments of the invention, a final pattern may be produced by combining a first and a second pattern. For example, a first pattern may comprise thin finger lines and a second pattern may comprise wider bus lines or bars which may be orthogonal to the finger lines. For example, the pattern shown in Fig. 1 may be thus produced. In some embodiments of the invention, a test pattern may be printed with the first pattern at areas or regions where the first and second patterns intersect. For example, finger lines 222 and test patterns 224 may be printed such that test patterns 224 are printed at locations where bus bars 251 are to be subsequently printed. Accordingly, test patterns 224 may become invisible or may be covered or hidden by bus bars 251. An advantage of the methods and systems described herein relates to printing test patterns on reserved areas, e.g., areas to be subsequently printed on. For example, printing the test pattern on areas reserved for bus bars is such that no shadow losses are added by covering the surface of a solar cell with non transparent test pattern lines. Yet another advantage is that many nozzles can be simultaneously tested and possibly serviced without impeding a current or on going printing process. For example, printing test patterns, analyzing such patterns and possibly correcting faults may be done simultaneously with a progress of a print job. Yet another advantage relates to inspecting print units during, while, or simultaneously with, conducting an actual printing job.

[0025] According to embodiments of the invention, control unit 270 may control printheads 210 to print test patterns 224. For example, by being connected to translation unit 220 (e.g., to a conveyor system), control unit 270 may determine that a specific nozzle in one of printheads 210 is positioned such that it may dispense material at a location where bus bars 251 are to be deposited. Accordingly, control unit 270 may cause such specific nozzle to dispense a test pattern in such location. For example, control unit 270 may control a nozzle to deposit a continuous line (or finger) in a first region or during a first period of time, and a series of dots or other test patterns in a second region, or during a second period of time. Control unit may cause any nozzle in any one of printheads 210 to print a test pattern. In one embodiment, an active nozzle, e.g., a nozzle participating in printing finger lines 222, may be caused to additionally print some of test patterns 224. In another embodiment, idle, backup or redundant nozzles, e.g., nozzles not participating in printing fingers 222, may be caused to print some of test patterns 224. Likewise, a combination of active and inactive nozzles may be caused to print test patterns.

[0026] Reference is additionally made to Fig. 3 that shows an exemplary pattern 300. As shown, pattern 300 may comprise finger lines deposited on a substrate (e.g., a photovoltaic solar cell). As shown, pattern 300 may comprise finger lines 310 and 311 and test patterns 350, 360, 370 and 380. To produce pattern 300, control unit 270 may cause nozzles in printheads 210 to deposit finger lines 310 and 31 1 during a first period of a scan. When determining that a region where bus bars (e.g., 102 in Fig. 1) are to be printed is located under nozzles to be inspected, control unit 270 may cause such nozzles to deposit test patterns 350, 360, 370 and 380. Accordingly, a pattern such as 300 may be produced in a first scan.

[0027] According to embodiments of the invention, any nozzle in a print unit may be caused to print a test pattern as described herein. For example, printheads 210 may be fitted with hundreds of nozzles where only some of the nozzles (also referred to as active nozzles herein) may actively participate in a print job. A printhead may comprise a large number of redundant nozzles that may be used for backup. Both active and redundant nozzles, e.g., on printheads 210, may be caused to print a test pattern. Accordingly, both active and redundant or inactive nozzles may be inspected and serviced online as described herein.

[0028] Referring back to Fig. 2 and as shown, substrate 221 may be rotated by ninety degrees (90°). For example, rotational unit 223 may rotate substrate 221 as shown. Next, substrate 221 may be translated to an area close to image acquisition unit 240 where an image of test patterns 224 may be acquired. For example, an image of test patterns may be acquired by a camera placed above or beside a conveyor (not shown) translating substrate 221 in a scan direction shown by 280. In one embodiment, rotating the substrate prior to acquiring an image may be in accordance with a best point or field of view provided to image acquisition unit 240. For example, rotating substrate 221 as shown may enable image acquisition unit 240 to acquire a large number of images along a test pattern. Rotating the substrate as shown may provide more time for acquiring images since in such orientation, the test patterns are translated along a stationary point rather than across. An additional advantage of the rotation is that if two bus bars are to be printed as shown by 251 then two cameras covering the width of bus bars 251 may suffice in order to acquire an image of test patterns 224. Without such rotation, a possible larger number of cameras would be required, e.g., in order to cover the entire width of substrate 221.

[0029] From image acquisition unit 240, substrate 221 may be translated under printheads 250 that may deposit bus bars 251. Deposition of bus bars 251 may be over test patterns 224 thus test patterns 224 may be covered by bus bars 251. Accordingly, test patterns 224 do not use any additional space on substrate 221, namely, material that may block sun light from reaching photoelectric cells is not deposited on substrate 221 at regions other than those regions already dedicated for deposition of material. In some embodiments, processing and/or analyzing acquired images by processing unit 260 may be done while the substrate is being printed on. For example, such analysis may be performed while printheads 250 deposit bus bars 251.

[0030] Reference is additionally made to Fig. 4 that shows an exemplary flowchart diagram illustrating a method for inspecting and servicing print units according to embodiments of the present invention. As shown by block 410, the method may include printing a first part of a pattern on a substrate. For example, the finger lines 222 printed on substrate 221 are a first part of a final pattern where the final pattern comprises finger lines 222 and bus bars 251. Any suitable pattern having intersecting sections may be divided into a first and second part and accordingly, a first part may be printed as shown by block 410. As shown by block 415, the method may include printing a test pattern on the substrate. For example, test patterns 224 may be printed in regions where bus bars 251 are to be subsequently printed. For example, an area reserved for bus bars 251 may have a width of 0.2 mm while a typical drop of ink may cover a spherical area having a diameter of 50 μm. Accordingly, five to seven evenly spaced dots may be deposited by selected nozzles in a test area across a width of a bus bar.

[0031] As shown by block 425, the method may include rotating the substrate. For example and as discussed herein, a substrate may be rotated by ninety degrees (90°) such that a small number of imaging devices (e.g., two) located above regions where bus bars are to be printed may acquire images of test patterns. Although an exemplary rotation of ninety degrees (90°) is shown and discussed herein, any rotation, orientation or positioning of a substrate may be performed or affected to best suit a position, point of views, capability or other relevant aspects of an imaging system used for acquiring images of test patterns printed as shown by block 415.

[0032] Reference is additionally made to Fig. 5 that shows an exemplary printing system 500 according to embodiments of the invention. System 500 may comprise components similar to those described herein with respect to system 200 shown in Fig. 2 and may be an inkjet or aerosol printing system used in the production of photovoltaic (PV) solar cells. Although not shown, system 500 may comprise a processing unit, a control unit and a substrate mounting unit similar to those of system 200. System 500 may comprise a first set of printheads 510, a second set of printheads 550 and one or more image acquisition units 540. System 500 may comprise two translation units positioned at a right angle, or ninety degrees (90°) with respect to each other. Accordingly, a substrate may be translated in a first direction during a first time period and in a second, e.g., orthogonal direction, during a second time period where the two time periods are related to the same print job or process. Accordingly, instead of, or in addition to, rotating a substrate as described herein, the substrate may be made to travel in two or more directions during a print process.

[0033] For example, in cases where a test pattern's image is best obtained in the scan axis used for printing the test pattern, a camera placed over a first conveyor that translates the substrate in that direction may be used. In other cases, a second or another camera may be placed over a second conveyor and may obtain an image of a test pattern during a scan in a second direction. As shown by 521 (and similarly to 222 and 224 in Fig. 2) a first part of a pattern and test patterns may be printed by printheads 510. Image acquisition units may acquire an image of the test patterns shown by 521 in one of two angles with respect to the patterns and translation, printheads 550 may print a second part of a pattern that may partly or completely cover the test patterns. Accordingly, a final pattern as shown by 560 may be produced.

[0034] As shown by block 430, the method may include acquiring an image of the test pattern. Any suitable imaging system and related optic systems known in the art may be used to acquire images of test patterns as described herein. In a particular arrangement, the number of cameras may be equal to the number of bus bars. Acquiring images as described herein may be performed while the substrate is scanned, namely, is translated or in motion as described herein. In other embodiments, the substrate may be held stationary under the imaging system while an image is acquired. Accordingly, parameters such as exposure time, amount of light and the like may be adjusted and or controlled, e.g., control unit 270, to ensure an optimal image.

[0035] As shown by block 435, the method may include analyzing an image of the test pattern. For example, an acquired image may be provided by image acquisition system 240 to processing unit 260. Various aspects may be analyzed and various faults may be identified based on an image of a test pattern. For example, an angular deviation of the direction of a set of dots printed by a set of nozzles may indicate a deviation of the nozzle array from the scanning direction that may result from a misalignment of the related printhead. Another aspect may relate to a specific nozzle, for example, absence of a dot in a specific location may indicate a clogged nozzle. A nozzle ejecting ink sideways may be identified by a dot which deviates from the line of dots belonging to other nozzles in the same printhead. Likewise, the shape of a dot, short line or other pattern may indicate whether the relevant nozzle is ejecting properly or not. In other cases, based on a set of test patterns, synchronization of firing between different printheads or different nozzles in a printhead may be determined. Relative distance or orientation of test lines printed by nozzles selected from two or more printheads may enable determining whether a set of printheads is properly aligned or positioned.

[0036] As shown by block 440, the method may include printing a second part of a pattern on a substrate. For example, bus bars 251 printed as shown by Fig. 2 may constitute a second part of pattern 100. As described herein, a second part of a pattern may be printed at the same locations test patterns were previously printed.

[0037] As shown by block 445, the method may include performing an action based on analysis of the test pattern. For example, based on a detected fault, parameters such as nozzle head temperature, parameters related to a pulse applied to inkjet elements may be modified, e.g., pulse rise, shape, or duration time. Other examples of service or maintenance actions may be running the head through purge and/or wipe procedures, priming components etc. Other actions may be adjustment of driving parameters of inkjet elements such as, the amplitude of current pulses. In the case of aerosol jet based printers driving parameters that may be controlled or changed based on an analysis of a test pattern may include a pressure in the atomizer chamber, temperature, particle size, or different regime of gas flow.

[0038] Any applicable parameters, configurations or other aspects that may be modified or controlled may be set or adjusted as part of an action as shown by block 440. Further actions may be a classification of nozzles, e.g., an active yet faulty nozzle may be classified as inactive and an inactive, redundant or backup nozzle may be set as active. Various alignments may be performed, e.g., repositioning a printhead based on analysis results etc. Parameters related to a rotation of a substrate may likewise be adjusted. For example, an analysis of test patterns may reveal that the rotation of a substrate is not by the desired angle, accordingly, parameters related to a unit such as rotational unit 223 may be adjusted. A data base or other storage may be updated based on the analysis. For example, an entry indicating the number of faulty nozzle for a given printhead may be update, consequently, based on such entry it may be determined if the printhead needs servicing or replacement.

[0039] Although embodiments of the invention are not limited in this regard, the terms "plurality" and "a plurality" as used herein may include, for example, "multiple" or "two or more". The terms "plurality" or "a plurality" may be used throughout the specification to describe two or more components, devices, elements, units, parameters, or the like.

[0040] Unless explicitly stated, the method embodiments described herein are not constrained to a particular order or sequence. Additionally, some of the described method embodiments or elements thereof can occur or be performed at the same point in time or overlapping points in time. As known in the art, an execution of an executable code segment such as a function, task, sub-task or program may be referred to as execution of the function, program or other component.

[0041] Although embodiments of the invention are not limited in this regard, discussions utilizing terms such as, for example, "processing," "computing," "calculating," "determining," "establishing", "analyzing", "checking", or the like, may refer to operation(s) and/or process(es) of a computer, a computing platform, a computing system, or other electronic computing device, that manipulate and/or transform data represented as physical (e.g., electronic) quantities within the computer's registers and/or memories into other data similarly represented as physical quantities within the computer's registers and/or memories or other information storage medium that may store instructions to perform operations and/or processes.

[0042] While certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes, and equivalents may occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.

Claims

CLAIMS What is claimed is:

1. A method of inspecting a print system comprising: dispensing on a substrate material from nozzles of print units to form in a single scan both a test pattern and a first part of a print pattern; acquiring image of the test pattern; analyzing the image; and dispensing on the substrate material from nozzles of another one or more print units to form a second part of the print pattern covering the test pattern.

2. The method of claim 1, wherein the material is an electrically conductive material and the substrate is a semiconductor wafer.

3. The method of claim 1, further comprising: moving the substrate in a single scan direction.

4. The method of claim 1 comprising: rotating the substrate by a predefined angle prior to acquiring the image.

5. The method of claim 2, wherein the first part of the pattern is a pattern of conductive finger lines deposited by a first group of print units and the second part of the pattern is a pattern of bus bars deposited by a second group of one or more print units.

6. The method of claim 5, wherein the test pattern is deposited by a third group of one or more print units intended to be used for depositing material on a subsequent substrate.

7. The method of claim 6, wherein the third group comprises idle print units not participating in forming the print pattern.

8. The method of claim 7 comprising: changing the status of the idle print units to active based on the analysis of the image; changing the status of the print units of the first group to idle based on the analysis of the image; and dispensing material on another substrate from one or more print units of the third group.

9. The method of claim 1 , wherein the test pattern is deposited by idle nozzles of the first group of print units intended to be used for depositing material on a subsequent substrate.

10. The method of claim 5, wherein at least part of the print units comprise a jetting nozzle array having redundant jetting nozzles.

11. The method of claim 10, wherein the orientation of said jetting nozzle array is parallel to a scan direction

12. The method of claim 1 , wherein nozzles forming the print pattern are assigned a status of active nozzles and nozzles not forming the print pattern are assigned a status of idle nozzles and the method further comprising changing the status of nozzles for depositing material on a subsequent substrate based on the analysis of the image.

13. The method of claim 1 , wherein after depositing the second part of the print pattern, the test pattern does not interfere with an attribute of interest of the print pattern.