U.S. patent application number 12/487173 was filed with the patent office on 2010-03-18 for method and system for nozzle compensation in non-contact material deposition.
Invention is credited to Ofir Baharav, Hanan Gothait, Ran Asher Peleg.
Application Number | 20100066779 12/487173 |
Document ID | / |
Family ID | 42006829 |
Filed Date | 2010-03-18 |
United States Patent
Application |
20100066779 |
Kind Code |
A1 |
Gothait; Hanan ; et
al. |
March 18, 2010 |
METHOD AND SYSTEM FOR NOZZLE COMPENSATION IN NON-CONTACT MATERIAL
DEPOSITION
Abstract
A method of printing is provided where printing is using a first
printing unit having redundant nozzles. Then, the method may
include stopping the printing with the first printing unit while
continuing the printing with active nozzles of a second printing
unit. The method may include inspecting the first printing unit and
identifying faulty nozzles, then designating the faulty nozzles as
inactive and designating inactive nozzles of the first printing
unit as a new active nozzle. According to some embodiments the
method may include moving the first printing unit to an inspection
zone prior to inspecting while continuing the printing with active
nozzles of a second printing unit and moving the first printing
unit back to the printing zone after inspection and continuing the
printing with the first printing unit.
Inventors: |
Gothait; Hanan; (Rehovot,
IL) ; Peleg; Ran Asher; (Kefar-Saba, IL) ;
Baharav; Ofir; (Los Altos Hills, CA) |
Correspondence
Address: |
Pearl Cohen Zedek Latzer, LLP
1500 Broadway, 12th Floor
New York
NY
10036
US
|
Family ID: |
42006829 |
Appl. No.: |
12/487173 |
Filed: |
June 18, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12134294 |
Jun 6, 2008 |
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12487173 |
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PCT/IL2007/001468 |
Nov 28, 2007 |
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12134294 |
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60867423 |
Nov 28, 2006 |
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61073889 |
Jun 19, 2008 |
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Current U.S.
Class: |
347/14 |
Current CPC
Class: |
B41J 2/16588 20130101;
B41J 25/001 20130101; H05K 3/46 20130101; B41J 2/2142 20130101;
B41J 2/2139 20130101; B41J 2/2146 20130101; B41J 2/515 20130101;
B41J 2/16579 20130101 |
Class at
Publication: |
347/14 |
International
Class: |
B41J 29/38 20060101
B41J029/38 |
Claims
1. A method of printing, the method comprising: printing in a
printing zone using a first printing unit having nozzles, a first
portion of the nozzles is designated as active nozzles and a second
portion of the nozzles is designated as inactive nozzles, wherein
the printing is done by selectively depositing material from the
active nozzles of the first printing unit; stopping the printing
with the first printing unit while continuing the printing with
active nozzles of a second printing unit; inspecting the nozzles of
the first printing unit; choosing a new set of active nozzles based
on inspection results; and continuing the printing using the first
printing unit with the new set of active nozzles.
2. The method of claim 1 comprising: moving the first printing unit
to an inspection zone prior to inspecting; and moving the first
printing unit back to the printing zone for continuing the
printing.
3. The method of claim 1, wherein the nozzles are arranged in a row
having a direction parallel to a scanning direction.
4. The method of claim 1, wherein printing comprises printing a
line in the scanning direction.
5. The method of claim 1 comprising: identifying one of the active
nozzles of the first printing unit as a faulty nozzle; designating
the faulty nozzle as inactive and designating one of the inactive
nozzles of the first printing unit as a new active nozzle, so as
the new active nozzle replaces the faulty nozzle.
6. The method of claim 1, wherein inspecting comprises: acquiring
images of ejections of droplets performed by the nozzles of the
first printing unit; and identifying the faulty nozzle based on an
analysis of the images.
7. The method of claim 6, wherein the analysis comprises
determining the size of droplets and the size of deviation of a
jetting direction from a predetermined direction.
8. The method of claim 1, wherein depositing is depositing an
electrically conductive material on one of a printed card board or
a semiconductor wafer to produce metallization conduction
lines.
9. The method of claim 1, wherein the new set of active nozzles is
chosen based on a required droplet size.
10. The method of claim 1, wherein the new set of active nozzles is
chosen based on the degree of stability of jetting from the
nozzles.
11. The method of claim 1, wherein the new set of active nozzles is
chosen based the jetting direction of the nozzles.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims benefit of U.S. provisional
patent application No. 61/073,889, filed on Jun. 19, 2008. The
present application is also a Continuation-in-part application of
U.S. patent application Ser. No. 12/134,294, filed on Jun. 6, 2008,
which is a Continuation-in-part patent application of PCT
International application No. PCT/IL2007/001468, entitled "Inkjet
Printing System With Movable Print Heads And Methods Thereof",
filed on Nov. 28, 2007, which in turn claims priority from U.S.
provisional application No. 60/867,423, entitled "Configurable
Drop-On-Demand Printing System", filed on Nov. 28, 2006, all of
which are incorporated herein by reference in their entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to printing generally and to
drop on demand (DOD) inkjet printing in particular.
BACKGROUND OF THE INVENTION
[0003] Deposition printing, such as for example Drop on demand
(DOD) inkjet printing or aerosol printing, is known in the art.
Such printing may be typically used for low speed, low volume print
jobs, such as, for example, large format digital printing for the
signage market, and low quantity printing of textiles.
[0004] Reference is now made to FIGS. 1 and 2 which together
illustrate a prior art one pass in-line printer system 100. System
100 comprises a conveyor 120 on which print media 10 is placed,
static jetting arrays 140 which drop ink onto print media 10 and a
jetting controller 150 which indicates to jetting arrays 140 when
and how to print to produce a printed image 115 as per input image
data 155.
[0005] One or more jetting arrays 140 may be used to print each
color that may be used by a print job. One or more additional
jetting arrays 140 may also be dedicated to the application of
additional coatings or varnishes as required. As illustrated in
FIG. 2, a jetting array 140 is organized into print units 160. The
print units are static with respect to each other. Each print unit
160 consists of one or more print heads 170, and each print head
170 may have several dozen or even hundreds of nozzles 180,
although for the sake of clarity, only a few are shown in FIG. 2.
Multiple print heads 170 may be used together to speed up the print
process and/or to print images of varying degrees of
resolution.
[0006] Jetting controller 150 (FIG. 1) transmits a stream of
commands to jetting arrays 140 that control the jetting of nozzles
180 in order to translate image data 155 to printed image 115. As
print media 10 passes underneath jetting arrays 140, jetting arrays
140 may remain in a static position and nozzles 180 can then jet
onto print media 10. Each nozzle 180 may jet thousands of drops per
second during the printing process.
[0007] Nozzles 180 may suffer defects that may partially or wholly
impair their effectiveness. Such nozzles may stop jetting or may
jet poorly. Such defects may be of either a temporary, or a
permanent nature.
[0008] DOD inkjet systems and other deposition printing systems,
such as aerosol jetting printing system or a dispenser, may
therefore require frequent maintenance to prevent or repair such
defects, and to ensure the ongoing reliability of the dispensing
heads. Such maintenance may include, for example, in the case of
inkjet, purging the nozzles with liquid or air, wiping and/or
brushing the nozzles and/or the orifice plate, fire jetting with
the entire group of nozzles or part of them, heating or cooling the
nozzles, or washing the heads with liquids. Nozzles with permanent
defects may be replaced.
[0009] Typically, such maintenance may be performed several times
during a printing hour. Repeated stoppage of the printing process
to perform maintenance may slow down the printing process and
consequently raise the cost of printing. Conversely, failure to
perform timely maintenance of the nozzles may result in poorer
print quality and higher equipment costs as a higher percentage of
nozzles may be permanently damaged and may need to be replaced.
[0010] The most common implementation of DOD inkjets for printing
applications, such as graphic arts and others, entails multiple
passes over the same area. The jetting heads pass over the same
area a number of times, each time with a small shift so that each
nozzle jets in several slightly different locations. The resulting
print area for a given nozzle may therefore be overlapped by the
print area for one or more other nozzles. Since the same area is
printed by more than one nozzle, these overlapping print areas may
serve to mitigate the effects of a defective nozzle that jets
poorly or not at all. Accordingly, the use of such multiple pass
jetting with overlapping print areas may enable a system to create
quality prints even with several defective nozzles. It is highly
desired to have a one pass jetting system capable of compensating
for defective nozzles to enable creating quality prints.
[0011] Non-contact material deposition printing is an appealing
method for patterning and depositing materials in the printed
electronics and solar cell industries. For example, forming
conductive lines by directly depositing conductive materials on the
back or front surface of the solar cell to provide a conduction
path for the charge generated by the cell may increase the
efficiency of the solar cell as well as the productivity of
mass-manufacturing.
[0012] Deposition printing techniques, such as ink jet printing or
aerosol printing involves depositing droplets of print material
from nozzles by moving a print head and a substrate relative to one
another along a printing direction. One of the problems associated
with deposition printing is faulty nozzles that may stop jetting or
may jet poorly. Accordingly, a faulty nozzle may result in uneven
conductive lines which may lead to inefficient or inoperative solar
cells.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] 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 accompanying
drawings in which:
[0014] FIGS. 1 and 2 together are a schematic illustration of a
prior art one pass in-line printer system 100;
[0015] FIGS. 3 and 4 together are a schematic illustration of an
exemplary printing system according to embodiments of the present
invention;
[0016] FIG. 5 is a flow chart illustration of an operating method
according to embodiments of the present invention;
[0017] FIG. 6A is a cross-sectional view of movable print unit
according to exemplary embodiments the present invention;
[0018] FIG. 6B is a schematic illustration of a close-up view of a
portion of an exemplary printing system according to embodiments of
the present invention;
[0019] FIGS. 7, 9A, 10A, and 11A are schematic illustrations of
different states of movable print units according to embodiments of
the invention;
[0020] FIGS. 8, 9B, 10B, and 11B are magnified views of exemplary
printouts from the print units of FIGS. 7, 9A, 10A and 11A,
respectively;
[0021] FIGS. 12A and 12B together illustrate a method of printing
with variable widths during the course of a print job according to
embodiments of the invention;
[0022] FIG. 13 shows an exemplary printing system according to
embodiments of the invention;
[0023] FIG. 14 shows printing units having redundant nozzles and
positioned parallel to the print direction helpful in demonstrating
embodiments of the invention; and
[0024] FIG. 15 is a flowchart diagram illustrating a method for
printing according to some embodiments of the present
invention.
[0025] 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 THE PRESENT INVENTION
[0026] 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 skilled
in the art that the present invention may be practiced without
these specific details. In other instances, well-known methods,
procedures, and components have not been described in detail so as
not to obscure the present invention.
[0027] 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.
[0028] 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.
[0029] Some embodiments of the invention are directed to a
deposition printing system that includes two or more print units
capable of moving with respect to each other during printing. In
the description below a demonstrative embodiment of an inkjet
printing system is illustrated. It should be, however, understood
to a person skill in the art that embodiments of the invention are
not limited in this respect and other suitable deposition printing
systems may be used, such as, an aerosol printing system, a
dispenser and others.
[0030] Reference is now made to FIGS. 3 and 4, which together
illustrate an exemplary inkjet printing system 200 according to
embodiments of the invention. System 200 is capable of executing
continuous high speed, high volume print jobs without frequently
stopping for maintenance. Similar reference numerals refer to
similar units.
[0031] Printing system 200 may include conveyor 120, defining the
width of a print area, on which print media 10 is placed, one or
more jetting array housings 250 laterally positioned in fixed
positions facing conveyor 120, a controller 270 to control the
printing process and one or more maintenance stations 255. Each
housing 250 may have a designated maintenance station 255 that may
be set in close proximity to its associated jetting array alongside
conveyer 120. Printing system 200 may further include a visual
detector 256, such as camera or charge coupled device (CCD) coupled
to controller 270 and positioned in proximity to maintenance
station 255 to inspect the status and condition of nozzles of print
units located at the maintenance area. Any other suitable visual
detector capable of inspecting the nozzles may be used.
[0032] Printing system 200 may include, attached to each jetting
array housing, two or more movable print units 220 capable of
moving with respect to each other during printing. Print heads 220
may move in a direction substantially perpendicular to the print
direction represented by the direction of advance of conveyer 120.
Each of the print units may include one or more print heads located
in fixed positions within the movable print unit. The relative
positioning of the print units with respect to each other form
particular head arrangement capable of being dynamically changed
during printing (on the fly).
[0033] For a given head arrangement, the desired functionality of
each of print units 220 may be determined by controller 270. For
example, print unit 220A may be designated as an idle print unit to
indicate that the print unit temporarily does not actively jet
participate and can move to the maintenance area. The remaining
print units, 220B-220E may be designated as active print units to
indicate that they are currently involved in printing, namely, at
least one of their nozzles may jet according to the image data.
According to embodiments of the invention, one or more of print
units, for example unit 220D may be designated as compensating
print unit having the role of compensating for defect nozzles
belonging to at least another print unit, for example 220C.
Therefore, both print units 220D and 220C print wherein print unit
220C jets from its nozzles according to the image data excluding
the defective nozzles and print unit 220D jets only from nozzles
that may replace the defective nozzles of print unit 220D.
[0034] Although print units 220A-220D are described as associated
with an inkjet printing system, it should be, however, understood
to a person skilled in the art that embodiments of the invention
are not limited in this respect and the print units according to
other embodiments of the invention may be associated with other
suitable deposition printing systems, such as an aerosol printing
system or a dispenser.
[0035] It should be understood to a person skilled in the art that,
over time, each print unit 220 may be designated as either
"active", "idle" or "compensating", according to its current
functionality. According to embodiments of the invention, the
timing of the role changing of the print units is determined so as
to maintain substantially even distribution of workload between the
print units. Further, according to embodiments of the invention, in
order to maintain substantially even distribution of workload
between nozzles within one print unit, the print unit may be moved,
from time to time, with respect to other print units to enable
activation of previously inactive nozzles.
[0036] According to an exemplary embodiment of the invention, each
print unit 220 may include four print heads, each having 192
nozzles. It should be understood however to a person skilled in the
art that the invention is not limited to such an arrangement and
according to embodiments of the invention, any suitable numbers of
print heads and nozzles are applicable.
[0037] Controller 270 may dictate the movement of various movable
print units 220, with respect to each other, within and without the
print area, to their associated maintenance stations. Controller
270 may control movement of the print units to dynamically change
the head arrangement during the printing.
[0038] In accordance with embodiments of the present invention,
controller 270 may track the maintenance schedule of movable print
units 220. When a movable print unit, here labeled 220A, requires
maintenance, controller 270 may determine the current status
functionality of the unit to be idle and instruct a motor unit 230
coupled to print unit 220A to move to its maintenance station 255.
Since maintenance stations 255 are generally located alongside
conveyor 120, printing system 200 may continue to print while
movable print unit 220A undergoes maintenance.
[0039] As illustrated in FIG. 4, movable print units 220 are
located in jetting array housing 230 and may be moved along sliders
240. Such movement may extend most of each movable print unit 220
beyond the extent of jetting array housing 230 to maintenance
station 255. It will be appreciated that maintenance stations 255
are located outside of a print area as defined by the area
underneath "active" movable print units 220.
[0040] Reference is now made to FIG. 5 which illustrates a method
according to embodiments of the invention by which system 200 may
perform maintenance while continuing to print. As shown in FIG. 5,
when, for example, movable print unit 220B requires maintenance
(step 280), controller 270 may issue (step 282) a command to
another movable unit 220A, which may be idle at the time, to slide
back into jetting array housing 230. Controller 270 may then
designate movable print unit 220A as active (step 284) and movable
print unit 220B may then be designated the idle print unit (step
286) and may then adjust the jetting commands (step 288) based on
the change in status of movable print units 220A and 220B. The
jetting commands are adjusted due to the fact that the physical
location of movable print unit 220A differs from the physical
location occupied by movable print unit 220B. Controller 270 may
then wait for a cycle where movable print unit 220B may not be in
actual use before issuing (step 290) a command to movable print
unit 220B to move along slider 240B (arrow 260B) to maintenance
station 255.
[0041] While in maintenance station 255, print heads 210 in movable
print unit 220 may undergo various maintenance procedures
including, for example, purging the nozzles with liquid or air,
wiping and/or brushing the nozzles and/or the orifice plate, fire
jetting with the entire group of nozzles or part of them, heating
or cooling the nozzles, or washing the heads with liquids. Nozzles
with permanent defects may also be replaced. The print unit may be
inspected prior to performing the maintenance operations using
manual inspection or automatic inspection using detector 256.
According to embodiments of the invention, based on the inspection
result, it may be determined if the print unit require maintenance
and if so what maintenance operations to perform.
[0042] After maintenance is completed, movable print unit 220 may
be examined. This examination may be an automated procedure using
detector 256 and/or may employ a manual operator. The examination
may also include a visual inspection of the movable print unit 220
and print heads 210. A test print may be performed and the
measurement of the resulting drop shapes and weights may be checked
using either manual procedures or automated test equipment. Various
characteristics of movable print unit 220 may also be measured,
including, for example, temperature, electronic pulses and/or pulse
shapes. The registration and alignment of print heads 210 may also
be measured.
[0043] The examination results may then be analyzed to detect, for
example, missing nozzles, weak nozzles, crooked nozzles, a drop
volume that is not proper, and/or misalignment of print heads 210.
Depending on the errors detected, another maintenance session may
be required, one or more print heads 210 may be replaced, and/or
printing may continue with movable print unit 220. It may be
possible to compensate for some defects by using jetting controller
150 to adjust the printing parameters for the affected print head
210. Such parameters may include, for example, jetting pulse,
shape, amplitude and/or temperature.
[0044] After analysis of the examination results and adjustment of
any parameters as needed, the idle movable print unit 220 may then
be available to replace another movable print unit 220 due for
maintenance.
[0045] It will be appreciated that there may be more than one idle
movable print unit 220 in a given head arrangement. The number of
"idle" and "active" movable print units 220 may be configured in
accordance with an operator's requirements for speed, resolution,
and frequency of maintenance.
[0046] Reference is now made to FIG. 6A which is a cross-sectional
view of one movable print unit 220. Movable print unit 220 may
comprise print heads 210, a translation apparatus 215 and slider
240. Translation apparatus 215 may comprise connecting brackets
310, slider guide carriages 320, a lead screw driving nut 330, and
a lead screw 340.
[0047] Slider guide carriages 320 may straddle slider 240, and
movable print unit 220 may be connected to slider guide carriages
320 via connecting brackets 310. Lead screw driving nut 330 may
also be affixed to movable print unit 220 via connecting brackets
310. Lead screw 340 may run through lead screw driving nut 330 such
that, when lead screw 340 turns, movable print unit 220 may move
along slider 240.
[0048] Reference is now made to FIG. 6B, which illustrates a
close-up view of portion of a printing system, the "home position
area", according to embodiments of the present invention. The home
position area may include, for example, lead screws 340, home flags
350 (attached to movable print units 220), couplings 360, stepper
motors 370, home position sensors 380 and configurable jetting
array housing 230.
[0049] Home flags 350 may be used to determine whether or not
movable print units 220 may be in their home position. As such,
home position sensors 380 may be mounted on jetting array housing
230, opposite home flags 350 which are attached to the end of
movable print units 220. When, for example, system 200 is powered
up, movable print units 220 may be moved to a home position, such
that home flag 350 may be sensed by home position sensor 380. Home
position sensors 380 may be, for example, optical or electrical
proximity sensors.
[0050] Controller 270 may then register each movable print unit 220
as being in the home position. When movable print unit 220 may be
designated for movement, for example to the maintenance area,
stepper motor 370 may be used to turn lead screw 340. Controller
270 may then track the new position of print units 220 by
calculating the offset defined by the difference between the home
position and the movement generated by stepper motor 370.
[0051] According to embodiments of the invention, the positions of
the print unit, both the initial positions relative to each other
and the changes in the positions of the units in the print area
during printing may be determined by performing an optimization
calculation. The optimization calculation may be stochastic
calculation based on image data and/or nozzle status data. For
example, based on the knowledge that a particular nozzle of a
particular print unit is defective and that a potion of the image
is blank, the optimization calculation may assign the print head
having the most defective nozzles to be positioned above the area
that is not to be printed.
[0052] It will be appreciated that as described herein above,
printing system 200 may provide continuous DOD one pass printing
without frequent stoppages for maintenance.
[0053] In an alternate embodiment of the present invention,
printing system 200 may not be configured for one pass printing.
For example, printing system 200 may be configured for web printing
or multiple pass printing.
[0054] Applicants have realized that movable print units 220 may be
configured to increase the speed of a print job or alternatively to
increase the resolution by multiple-layer printing. Accordingly, in
some embodiments of the present invention, printing system 200 may
be configured to print with higher speeds.
[0055] Reference is now made to FIG. 7, which illustrates the
active movable print units 220 in an exemplary print head
arrangement. Each print head 210 may have several dozen or even
hundreds of nozzles 420, although for the sake of clarity, only a
few are shown in FIG. 7. Reference is also made to FIG. 8, which
illustrates a magnified view of an exemplary printout from such a
print head arrangement. FIG. 7 also shows stepper motors 370 and
lead screws 340 which may control the movement of movable print
units 220. As in the previous embodiments, similar reference
numerals refer to similar units.
[0056] It will be appreciated that all movable print units 220 in
FIG. 7 may be configured in precise alignment, such that they may
occupy parallel positions along the same print axis when printing
in a printing direction 410. In FIG. 8, output lines 460 represent
the combined print output from nozzles 420. Output from nozzles
420A is represented as "/"; output from nozzles 420B is represented
as "\"; and output from nozzles 420C is represented as "+".
[0057] Such an alignment may enable printing system 200 to print at
a higher speed. Since nozzles 420A, 420B and 420C may each
respectively jet over the same location, controller 270 may
instruct nozzles 420 to print simultaneously in mutually exclusive
contiguous print areas using interlacing printing.
[0058] FIG. 8 illustrates the results of such instruction. Each
print line 460 comprises a repeating pattern of output 451 from
nozzles 420A, 420B, and 420C. Each respective pattern of output 451
is comprised of three nozzle outputs 452, representing the output
from nozzles 420A, 420B and 420C. It will be appreciated that since
nozzles 420A, 420B and 420C may print simultaneously, the time
required to print each respective pattern of output 451 may be
equal to the time required for each respective nozzle 420.
Accordingly, it will be appreciated that in such a configuration
printing system 200 may print at a speed which is three times as
fast.
[0059] It will further be appreciated, that such an alignment where
each line is printed by several different nozzles, may improve
print quality and result in better image quality As each line of
output may be printed by a multiplicity of nozzles 420, the effect
of a given missing or defective nozzle 420 may be less noticeable
since other nozzles 420 may also be printing on the same line.
[0060] It will further be appreciated, that such an alignment where
each line is printed by several different nozzles may increase
print resolution and material per dot throughput and may enable
multiple-layer printing. According to some embodiments of the
invention, controller 270 may instruct nozzles 420A, 420B and 420C
to jet consecutively over the same location so as to increase the
amount of material per dot by three.
[0061] In a typical DOD printing system (such as in FIGS. 1 and 2),
it is not uncommon that the nozzles on a given print head may print
in slightly different strengths. This may be caused by a
combination of circumstances, including, for example, the distance
from the ink source to a nozzle; temperature variances within the
print head; dust and impurities in the print head; and defects
caused by extended use. It will be appreciated that such
differences may also exist when comparing the relative strength of
nozzle output from different print heads and movable print units
220.
[0062] It will therefore be appreciated that the exemplary print
out illustrated in FIG. 8 may not be of a uniform and consistent
strength. For many print jobs this level of print quality may be
acceptable. However, there may be print jobs, for example when
printing a uniform color background when a more homogeneous output
is required. According to embodiments of the present invention,
controller 270 may finely adjust the location of movable print
units 220 within jetting array housing 230 to enable a homogeneous
coverage of the print area for a desired resolution.
[0063] Reference is now made to FIGS. 9A which shows an exemplary
head arrangement configured according to embodiments of the
invention in such a manner as to provide a more complete and
homogeneous coverage of the print area. Movable print units 220A,
220B and 220C may each include three print heads 211, 212 and 213.
Reference is also made to FIG. 9B which represents an exemplary
printed output from such an head arrangement. Similar reference
numerals refer to similar units.
[0064] It may be unlikely that that all nozzles 420 have the same
jetting strength. For example, nozzles 420A on movable print unit
220A may generally jet more weakly than nozzles 420B on movable
print unit 220B, or print heads 212 may generally jet more weakly
than print heads 211 and 213. There may even be variances of
jetting strength among the different nozzles 420 in the same print
head 211, 212 or 213. Controller 270 may use data regarding the
relative strengths of nozzles 420 to determine a homogenized print
head arrangement for movable print units 220. The homogenized print
head arrangement may be determined by stochastic optimization
calculations. The data may be delivered to controller 270 from
visual detector 256 or from other sources.
[0065] Based on such homogenized print configuration, controller
270 may instruct stepper motors 370 to move print units 220 within
the print area. As in the previous embodiments, motors 370, for
example stepper motors, may move movable print units 220 by turning
lead screws 340. However, according to embodiments of the present
invention, such movement may be in very small increments. In such a
manner, the active movable print units 220 may be staggered
slightly in generally equidistant increments over the print area.
Accordingly, when printing in printing direction 410, the nozzles
420 for each print unit 220 may not be aligned along identical
print axes with the associated nozzles 420 of the other print units
220.
[0066] As shown in FIG. 9B, print lines 460A, 460B, 460C may now
each be located on slightly different print axes, such that there
may now be three times as many effective print lines 460 when
compared, for example, to the previous embodiment of FIG. 8. It
will be appreciated that, depending on the number and density of
nozzles 420, the effective print axes may now be contiguous or even
overlapping, such that a given print area will typically be covered
by multiple nozzles 420 from more than one movable unit 220.
Furthermore, such print areas may now be covered by nozzles 420
from multiple print heads 211, 212 and 213 with varying jetting
strengths. Accordingly, it will be appreciated that for a given
combination of print conditions, the overall coverage of the print
area may be more homogenous when movable print units are staggered
over the print area.
[0067] According to embodiments of the present invention, the print
head arrangement may be adjusted to compensate for missing or
defective nozzles 420.
[0068] As described hereinabove, after movable print units 220
undergo maintenance, they may then be examined and/or tested to
detect persistent defects that may not have been remedied by the
maintenance session. It is expected that some nozzles 420 may have
such persistent defects after maintenance is performed. In such
cases, movable print units 220 may be submitted for another
maintenance session, or may have some of its component parts
replaced. It is also possible that the entire movable print unit
may need to be replaced. According to embodiments of the invention,
detector may send an alert to controller 270 notifying that a
replacement of one or more print heads is needed. It may also be
expected that some movable print units 220, with relatively few
missing or defective nozzles 420, may be returned to "active"
status even though their use may affect the quality of the print
job.
[0069] According to embodiments of the present invention, one of
print units 220 may be designated as a replacement unit (RU) or
compensating unit for missing and/or defective nozzles 420 of
another print unit 220. If one or more nozzles 420 are detected as
missing or defective in a movable print unit 220, RU may be moved
and located in position to provide jetting action in place of the
missing and/or defective nozzles 420.
[0070] FIGS. 10A and 10B, to which reference is now made, together
illustrate possible effects of a given alignment of movable print
units 220 on the quality of output lines 460. Movable print units
220 may have a number of defective nozzles 421 that may have been
identified in a previous maintenance session. For example,
defective nozzle 421A may be located on movable print unit 220A,
and defective nozzle 421C may be located on movable print unit
220C. Print axes 430A and 430C may represent the print path of
nozzles 421A and 421 C when printing in a print direction 410.
Similar reference numerals refer to similar units.
[0071] As shown in FIG. 10A, the location of defective nozzle 421A
may dictate a print axis 430A, and the location of defective nozzle
421C may dictate a print axis 430C. Accordingly, while defective
nozzles 421A and 421C may be located on different movable print
units 220, they may be assigned to jet on contiguous or overlapping
print axes. FIG. 10B shows the results of such printing. A
noticeable gap 470 appears among the lines of printed output 460
where defective nozzles 421A and 421C were supposed to have
jetted.
[0072] Reference is now made to FIG. 11A which shows the print
units configured in a particular print head arrangement as to
compensate for the existence of defective nozzles 421A and 421C in
movable print units 220A and 220C, respectively. Reference is also
made to FIG. 11B which represents an exemplary printed output from
such a print head arrangement. Gaps 480A and 480C appear among
printed lines 460. Similar reference numerals refer to similar
units.
[0073] Controller 270 may instruct stepper motors 370 to move print
unit 220C slightly in order to provide distance between the print
axes 430 of defective nozzles 421A and 421C respectively. According
to embodiments of the invention, controller 270 may determine the
desired head arrangement based on stochastic optimization
calculations taking into consideration the nozzle status data.
According to some embodiments, the optimization calculation may
further be based on the specific image data. It will be appreciated
that other print units 220, for example unit 220A, may also be
moved as needed.
[0074] In the resulting exemplary print head arrangement, movable
print unit 220C has moved to a new position, thus creating distance
between the print axes 430C and 430A of defective nozzles 421C and
421A when printing along print direction 410. As shown in FIG. 11B,
two smaller gaps 480C and 480A are shown among printed lines
460.
[0075] It will be appreciated that smaller gaps 480C and 480A may
be less noticeable than gap 470 and may be invisible to the naked
eye. It will further be appreciated, that movable print units 220
may be configured in such a manner that printed characters 460 may
be on overlapping print axes. In such print head arrangements, gaps
480A and 480C may be eliminated in part or in entirety as other
nozzles 420 may jet on the print area nominally covered by
defective nozzles 421.
[0076] According to embodiments of the present invention, movable
print units 220 may also be configured in such a manner as to more
efficiently print a printed image with variable widths. This may be
facilitated by extending and/or retracting movable print units 220
over a wider print area before and/or during the course of a print
job.
[0077] Reference is now made to FIGS. 12A and 12B which together
illustrate how movable print units 220 may be moved to print with
variable widths during printing. As shown in FIG. 12A, printing
unit 200 may comprise a multiplicity of movable print units 220
configured in parallel to print in a narrow print area "N" in a
direction 410. It will be appreciated that, as described
hereinabove, such a configuration may be used, for example, to
increase the speed or resolution of a print job.
[0078] However, such a configuration may not be sufficiently wide
to print a wider print area. For such cases, it may be necessary to
move print units 220 into a new print head arrangement as shown in
FIG. 12B. Stepper motors 370 may extend lead screws 340, thus
moving movable print units 220B, as required, to provide coverage
for additional print area "W".
[0079] It will be appreciated that movable print units 220A may
remain in place and continue printing in print area N. However,
such printing may now be at a lower speed, or alternatively, the
resolution may be lower.
[0080] It will also be appreciated that movable print units 220B
may be retracted and returned to their original locations (as shown
in FIG. 12A) for subsequent ports of the print job that do not
require wider print coverage. The print speed and/or resolution may
then be adjusted accordingly.
[0081] It will further be appreciated that the configurations in
FIGS. 12A and 12B are exemplary. Other configurations may also be
used. For example, N and W may be of different widths. Furthermore,
non symmetric configurations may be used to print areas N and W
with different resolutions, and staggered non parallel movable
print units 220 may be used instead of the generally parallel units
220 shown in FIGS. 12A and 12B.
[0082] Embodiments of the invention may be applicable to a variety
of printing systems and methods. For the sake of clarity and
simplicity exemplary embodiments and references of non-contact
material deposition systems will mostly be for the application of
fabrication of conducting metal lines for solar cells using an
inkjet system. However, the scope of the invention is not limited
by such exemplary embodiments and may be applied to other
deposition systems, such an aerosol jet deposition system or a
dispenser and to other applications, such as graphics, press, mass
media, packaging, electronics and others.
[0083] Embodiments of the invention are directed to a system and
method for inspection of print nozzles while a print process or a
print job is in progress and replacing actively printing nozzles as
needed. According to embodiments, the system may comprise redundant
print heads or printing units such that the number of print heads
may be higher than the number of print head required to perform a
desired printing task. At any given time during printing a portion
of the heads may be active while the remaining print head may be
redundant heads.
[0084] According, while a print process is in progress, a first
subset selected from a plurality of print heads installed in a
system would be designated to deposit material on a substrate, a
second, different subset of print heads may be subjected to, or
undergo a maintenance procedure. For example, while a first print
head is actively depositing material on a substrate, a second print
head may be relocated from a printing area or zone to an
inspection, service or maintenance area. While the second print
head is being inspected, serviced, repaired or otherwise subjected
to a maintenance procedure, the first print head may continue to
print and/or deposit material.
[0085] In some embodiments, the method may include printing lines
on a substrate, for example printing contact lines on a
semiconductor wafer by depositing material from a printing unit
having nozzles arranged in one or more rows. According to
embodiments, the printing unit may comprise redundant nozzles. The
number of nozzles in a printing unit may be larger than the number
of nozzles needed to accomplish a desired printing task, for
example printing a line at a desired resolution. At any given time
during printing a portion of the nozzles within a printing unit may
be active while the remaining nozzles may be redundant or inactive.
The printing is done only by nozzles designated as active nozzles
while the remaining nozzles are designated as inactive nozzles.
Within a particular row, material may be selectively deposited
[0086] The method may further include moving the printing unit to
an inspection zone while continuing the printing with active
nozzles of another printing unit, which may perform the tasks of
the former printing unit. In the inspection zone the nozzles are
inspected and one of the active nozzles may be identified as a
faulty nozzle. According to some embodiments, the inspection may be
done at the printing zone without moving the printing unit to the
inspection zone.
[0087] Then, the identified faulty nozzle may be designated as
inactive and one of the previously designated as inactive nozzles
may become an active nozzle to replace the faulty nozzle. The
method may further include moving the printing unit back from the
inspection zone to the printing zone and continue printing with
that unit such that the new active nozzle would replace the faulty
nozzle.
[0088] According to embodiments of the invention, after all the
nozzles are inspected in the inspection zone or the printing zone,
the system may analyze the inspection data and may choose a best
set of nozzles to be the active nozzles based on predetermined
considerations. Then, the chosen nozzles may be designated or
specified as active nozzles while the remaining nozzles of the
printing unit would be designated as inactive. Determining the best
set of nozzles may be based on a required droplet size, stability
of jetting and/or choosing nozzles having substantially similar
deviation of their jetting direction from a normal to the nozzle
plate (orifice plate). Other parameters may be taken into
consideration for choosing the best set of nozzles without
departing from the scope of the invention.
[0089] Reference is made to FIG. 13 showing a high-level block
diagram of an exemplary printing system according to exemplary
embodiments of the invention. The exemplary system, denoted system
1000 may be capable of executing continuous high speed, high volume
print jobs without frequently stopping for maintenance or
inspection. It will be noted that system 1000 may be applicable to
a variety of printing systems, e.g., inkjet or aerosol dispensing
systems. System 1000 may include printing units or print heads
1050A-1050F, a printing zone 1100, such as a conveyor or platform
(not shown) defining the width of a print area, on which print
media, such as semiconductor wafers may be placed and a service
zone 1250, in which maintenance and inspection of the printing
units and their nozzles may take place.
[0090] Service zone 1250 may include one or more maintenance
stations to perform various maintenance operations to the printing
units. Although only six exemplary printing units are shown, any
applicable number of printing units may be used without departing
from the scope of the invention. The number of printing units is
determined such that at least one printing unit is redundant. The
redundancy enables the simultaneous inspection of non-active
nozzles when active nozzles continue with the printing process.
Accordingly, at least one printing unit from units 1050A-1050F may
be capable of independently moving between printing zone 1100 and
service zone 1250 while the other printing units remain at the
printing zone and continue with the printing process. Service zone
1250 may be near or in close proximity to printing zone 1100.
According to some embodiments of the invention, printing units
1050A-F may be mounted on rails such that they may be moved from
printing zone 1100 to service zone 1250. Any other transport units
or mechanisms may be used without departing from the scope of the
invention.
[0091] Each printing unit 1050A-F may comprise nozzles 1060
arranged in one or more rows. In the exemplary illustration of FIG.
13, each row has eight nozzles arranged in parallel to the printing
or scanning direction X. However, it will be appreciated by those
skilled in the art that each tow may include tens or hundreds of
nozzles. Each row may include redundant nozzles for substitution of
faulty nozzles upon detection. A faulty nozzle may be, for example,
a clogged nozzle that cannot jet any material, a weak or partially
clogged nozzle that can jet only a portion from the desired amount
of material or a nozzle that jet in a direction that strongly
deviates from the direction of jetting of the majority of the
nozzles.
[0092] Printing units 1050A-C may be positioned in proximity to
printing zone 1100 such that the rows would be parallel to the
print direction X. If the substrate in moved by a conveyor, the
printing direction may be represented by the direction of advance
of the substrate. In such a configuration, each row may print a
single metallization line in a direction parallel to the print
direction in one scan. Other setups or configurations of the
printing unit with respect to the print direction are possible
according to other embodiments of the invention.
[0093] System 1000 may further include a controller 1150 to control
the printing process and an image acquisition unit 1200 coupled to
controller 1150. According to embodiments of the invention,
controller 1150 may perform, or be involved in, tasks or functions
such as, but not limited to, coordination, configuration,
scheduling, arbitration, supervising, operation and/or management
of components of system 1000 and their operations. For example,
controller 1150 may control the movement of printing units 1050A-F
and the printed objects in printing zone 1100. Controller 1150 may
comprise any required or suitable hardware, software, firmware or a
combination thereof. For example, controller 1150 may be a
computing device comprising a controller and/or central processing
unit (CPU), a memory and input and output units.
[0094] Image acquisition unit 1200 may comprise a detector or
imaging device 1210, such as camera or charge coupled device (CCD)
to inspect the status and condition of the nozzles by acquiring,
for example, images of droplets of material that exits the nozzles.
Any other suitable visual detector or any other method of
identifying the status of the nozzles may be used. Image
acquisition unit 1200 may further comprise an image processing unit
1220 to analyze the images and determine the current status of the
inspected nozzles and storage 1230 to store data related to the
status of the nozzles.
[0095] According to embodiments of the invention, detector 1210 may
be coupled to a dedicated computing and storage device for
processing and storing the captured images or alternatively
controller 1150 may perform these operations. According to
embodiments of the invention, a pulsed light source, such as a
pulsed laser source or a pulsed light emitting diode (LED) may be
coupled to detector 1210 to enable imaging of droplets being
deposited from the nozzles. Controller 1150 may further control and
manage the inspection procedure, for example coordinating the
ejection of droplets, the light pulses and the operation of the
camera.
[0096] Reference is now made to FIG. 14, which illustrates an array
of printing units having redundant nozzles and positioned parallel
to the print direction to demonstrate embodiments of the invention.
Printing units 2100, 2200 and 2300 may be used to print conductive
lines on a semiconductor wafer in the production of solar cells.
According to embodiments of the invention, during printing, a first
subset of nozzles may be designated as active nozzles, for example,
nozzles 2240-2280 may be designated as active. A second subset of
nozzles within printing unit 2200, for example, nozzles 2210-2230
may be designated as inactive. Upon identifying that a nozzle, for
example, nozzle 2250 is defective, the defective nozzle may be
substituted by any one of the inactive nozzles 2210-2230. For
example, nozzle 2250 may be re-designated as inactive and nozzle
2220 may be re-designated as active.
[0097] According to embodiments of the invention, while a print
process is in progress and while one or more printing units
defining a first subset of printing units is actively depositing,
another one or more printing units defining a second subset of
printing units may move to service zone 1250 for maintenance and/or
inspection. Further, if desired, the status of at least one pair of
nozzles may be interchanged such that the previously active nozzle
would become inactive and the previously inactive nozzle would
become active.
[0098] The printing units relocated to service zone 1250 may be
inspected, serviced and configured. For example, nozzles may be
inspected by acquiring images of droplets dispensed or ejected by
nozzles of the inspected unit. The images may then be analyzed by
image processing unit 1220. Based on the analysis, faulty nozzles
may be identified and replaced by redundant nozzles. Further,
various working parameters may be modified or verified. For
example, based on the inspection of a nozzle, working parameters
such as pressure, temperature or voltage may be modified.
[0099] Referring back to FIG. 13, image processing unit 1220 may
receive images from detector 1210 and process such images by
applying any suitable image processing techniques. For example,
analysis of shape, trajectory and velocity of jetted droplets may
be performed by the image processing unit. For example, image
processing may be used to determine a condition of a nozzle based
on an image of droplets being ejected from the nozzle. Another
example may be comparing two or more images, possibly acquired over
a predefined period of time. By comparing or otherwise relating
images, various conditions, faults or other aspects of a nozzle may
be determined. For example, degradation in the performance of a
nozzle may be detected by comparing consecutive or successive
images.
[0100] While a video camera may provide images related to visible
light, other images may be produced. For example, detector 1210 may
be an infrared camera that may record temperatures, thus providing
a temperature distribution of ejected ink or aerosol. While as
described herein, imaging device or detector 1210 may be placed at
the service area, other configurations are possible. For example,
one or more cameras may be placed near, around or in proximity of a
printing area, e.g., area 1100. Such cameras may obtain images
during the printing process of nozzles depositing material onto a
test substrate.
[0101] Storage system or unit 1230 may receive and store images
acquired by detector 1210 and/or obtained from a different source,
e.g., a remote server or a removable storage media such as a
compact disk (CD) or memory chip. For example, reference images of
a desired ejection may be loaded into or otherwise stored in a
storage device and may be used for comparing with or otherwise
relating to images acquired by detector 1210. A reference image may
contain an image of an ideal, otherwise desirable ejection or
deposition and thus may be used, for example by comparing it to a
second image in order to determine if an injection imaged in the
second image is acceptable or otherwise determine a quality of the
ejection or other functional parameters related to the nozzle from
which the imaged droplet has jetted.
[0102] It should be appreciated by those skilled in the art that
the redundancy of the printing unit or print heads may enable
dynamically selecting the print heads that participate in a print
process. Accordingly, redundant, spare, unused or idle print heads
may exist and/or be available during a print process. Such
redundant print heads may enable dynamic replacement of print heads
while a print process is ongoing, active or in progress. For
example, if a first print head is active, e.g., actively
participating in a print process by depositing material on a media,
needs, or is selected to be serviced or inspected, a second,
inactive, idle or redundant print head may replace the first print
head by being made active. Accordingly, the first print head, now
being replaced, may be made inactive and may further be inspected,
serviced or be otherwise subjected to a maintenance procedure.
[0103] According to embodiments of the invention, the printing
units or print heads may be equipped with redundant nozzles. For
example, a print head that may require one hundred (100) nozzles in
order to perform its intended tasks may be equipped with five
hundred (500) nozzles. Accordingly, only a subset of nozzles
fitted, included or installed in a print head may actively
participate in a print process, e.g., actually eject material onto
a surface or media. According to embodiments of the invention,
redundancy of nozzles as described herein may enable dynamically
selecting or designating a subset of nozzles as active. Such
redundancy may further enable replacing active nozzles by inactive
ones. For example, upon determining that a first nozzle in a print
head needs to be replaced or serviced, e.g., due to a malfunction
or as part of a scheduled or periodic maintenance routine, a
second, inactive or redundant nozzle may be selected, made active,
and may replace the first nozzle by ejecting material onto a
surface or media.
[0104] Reference is made to FIG. 15 showing a flowchart diagram
illustrating a method for printing according to some embodiments of
the present invention. As shown by block 3100, the method may
include commencing a print process using a first printing unit or
print head. For example, information in a print file may be
provided to a printing system such as system 1000 described in FIG.
13. Provided with such information, controller 1150 may cause a
conveyor to locate wafers such that a subset of nozzles, designated
as active nozzles in both printing units 2300 and 2200 may deposit
conductive material on them. Based on information in such print
file, controller 1150 may control the nozzles and printing units
such that material is deposited according to specifications or
parameters in the print file.
[0105] As shown by block 3200, the method may include moving the
one or more printing units, for example printing unit 2200 to a
service zone. During the time that the printing unit is being
inspected and/or serviced at the service zone, another printing
unit, such as printing unit 210 that was previously redundant may
become active so that the printing process may continue with
printing units 2100 and 2300. As shown by block 3300, the method
may include inspecting the nozzles of printing unit 2000 and
identifying one or more nozzles, for example nozzle 2250 as faulty
or defective nozzle.
[0106] The method may include determining whether the fault can be
repaired. For example, if a total obstruction of a nozzle's orifice
is detected, a procedure may exist to remove the obstructions from
the orifice thus repairing the fault. Other detected faults may be
such that require a complex, possibly manual procedure in order to
be fixed. Classifying a fault as one that may be handled or
repaired immediately or while a print process is in progress may be
according to various parameters and/or configurations. If the fault
may be repaired, flow may include servicing the nozzle. For
example, the working parameters may be modified or an automated
purging procedure may be executed.
[0107] As shown by block 3350, the method may include choosing a
best set of nozzles as best nozzles based on the inspection.
Accordingly, the method may include designating a faulty nozzle as
inactive when repair is impossible or undesirable. Nozzles
identified as inactive may not participate in the printing process
until their status is changed to "active". As shown by block 3400,
the method may comprise designating the nozzles of the chosen set
as active and the faulty nozzles and remaining nozzles of the
printing unit as inactive. For example, the method may include
designating a nozzle, from the same row of the newly faulty nozzle
that was previously designated an inactive nozzle as active. For
example, after determining that nozzle 2250 is faulty, a redundant
nozzle that was previously inactive and did not participate in the
printing process, such as nozzle 2230 may be designated as an
active nozzle that would replace the faulty nozzle 2250.
[0108] While as described herein, a first, faulty nozzle may be
designated as inactive and a second, inactive nozzle may be
designated as active in order to compensate for the faulty nozzle,
other scenarios are possible. For example, nozzles with the same
printing unit and possibly the same row may be replaced based on a
predefined schedule. For example, in order to avoid drying of ink
in nozzles, nozzles may be designated as active or inactive
periodically. While in some embodiments a first nozzle may be
replaced by a second nozzle, other combinations are possible. For
example, a faulty nozzle may be replaced by two redundant nozzles.
For example, such two nozzles may be instructed such that their
combined operation is the same as an expected operation of the
faulty, replaced nozzle.
[0109] As shown by block 3450, the method may include after the
inspection is over, moving the first printing unit back to the
printing zone. As other print heads may be printing at such time,
printing unit 2200 may replace, for example, printing unit 2100 in
performing the ongoing print process and printing unit 2100 may be
moved to the service area for inspection. Alternatively, printing
unit 2200 may replace, for example, printing unit 2300 in
performing the ongoing print process and printing unit 2300 may be
moved to the service area for inspection. Accordingly, as shown by
block 3500, the method may comprise ceasing to print with a working
printing unit and continuing with the print process using the first
printing unit. The first printing unit may be for example, unit
2200 in which the newly active nozzle, nozzle 2210 replaces the
previously used and now faulty nozzle 2250.
[0110] Embodiments of the invention may include an article such as
a computer or processor readable medium, or a computer or processor
storage medium, such as for example a memory, a disk drive, or a
USB flash memory, encoding, including or storing instructions,
e.g., computer-executable instructions, which when executed by a
processor or controller, carry out methods disclosed herein.
[0111] While certain features of the invention have been
illustrated and described herein, many modifications,
substitutions, changes, and equivalents will now occur to those of
ordinary skill 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.
* * * * *