U.S. patent application number 14/063351 was filed with the patent office on 2015-04-30 for color-to-color correction in a printing system.
The applicant listed for this patent is Eastman Kodak Company. Invention is credited to Randy Eugene Armbruster, James Alan Katerberg, Christopher M. Muir.
Application Number | 20150116408 14/063351 |
Document ID | / |
Family ID | 51845515 |
Filed Date | 2015-04-30 |
United States Patent
Application |
20150116408 |
Kind Code |
A1 |
Armbruster; Randy Eugene ;
et al. |
April 30, 2015 |
COLOR-TO-COLOR CORRECTION IN A PRINTING SYSTEM
Abstract
A method for performing color-to-color correction for printing
multiple copies of a print job having one or more documents is
disclosed. A first copy of the print job is printed using a
plurality of color planes. A first plurality of color registration
errors produced during the printing of the first copy of the print
job is determined. For each document in the print job, a processor
is used to determine a first plurality of local color plane
correction values for each color registration error produced during
the printing of the first copy of the print job. Each of the first
plurality of local color plane correction values corresponds to one
of the first plurality of color registration errors. A second copy
of the print job is printed using the local color plane correction
values for each document in the print job.
Inventors: |
Armbruster; Randy Eugene;
(Rochester, NY) ; Muir; Christopher M.;
(Rochester, NY) ; Katerberg; James Alan;
(Kettering, OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Eastman Kodak Company |
Rochester |
NY |
US |
|
|
Family ID: |
51845515 |
Appl. No.: |
14/063351 |
Filed: |
October 25, 2013 |
Current U.S.
Class: |
347/15 |
Current CPC
Class: |
G03G 2215/00021
20130101; B41J 2/2135 20130101; G03G 15/5062 20130101; B41J 2/2132
20130101; G03G 15/0194 20130101; H04N 1/506 20130101 |
Class at
Publication: |
347/15 |
International
Class: |
B41J 2/21 20060101
B41J002/21 |
Claims
1. A method for performing color-to-color correction for printing
multiple copies of a print job having one or more documents,
comprising: printing a first copy of the print job using a
plurality of color planes; determining a first plurality of color
registration errors produced during the printing of the first copy
of the print job; for each document in the print job, using a
processor to determine a first plurality of local color plane
correction values for each color registration error produced during
the printing of the first copy of the print job, wherein each of
the first plurality of local color plane correction values
corresponds to one of the first plurality of color registration
errors; and printing a second copy of the print job using the local
color plane correction values for each document in the print
job.
2. The method as in claim 1, further comprising storing the
plurality of local color plane correction values in processor
accessible memory for printing subsequent print jobs.
3. The method as in claim 2, further comprising: determining a
second plurality of color registration errors produced during the
printing of the second copy of the print job; for each document in
the second copy of the print job, using the processor to determine
a second plurality of local color plane correction values for each
second color registration error produced during the printing of the
second copy of the print job, wherein each of the second plurality
of local color plane correction values corresponds to one of the
second plurality of color registration errors; using the processor
to update each stored local color plane correction value using the
respective second local color plane correction value associated
with the printing of the second copy of the print job; and printing
a subsequent copy of the print job using the updated local color
plane correction values for each document in the print job.
4. The method as in claim 3, further comprising storing the updated
local color plane correction values in processor accessible memory
for printing subsequent print jobs.
5. The method as in claim 3, wherein using the processor to update
each stored local color plane correction value further comprises:
using the processor to periodically or non-periodically update each
of the stored local color plane correction values using the
respective local color plane correction values associated with the
printing of two or more subsequent copies of the print job.
6. The method as in claim 3, wherein using the processor to update
each stored local color plane correction value further comprises:
using the processor to update each of the stored local color plane
correction values after each subsequent print job using the
respective local color plane correction values associated with the
printing of the subsequent copy of the print job.
7. The method as in claim 3, using the processor to update each
stored local color plane correction value further comprises
determining an average of the local color plane correction values
associated with the first and second copies of the print job.
8. The method as in claim 5, wherein using the processor to
periodically update each of the stored local color plane correction
values further comprises: for each document in the print job and
for each type of color plane correction value, using the processor
to determine an average of the local color plane correction values
using respective local color plane correction values associated
with a predetermined number of subsequent copies of the print
job.
9. The method as in claim 5, wherein using the processor to update
each of the stored local color plane correction values further
comprises: for each document in the print job and for each type of
color plane correction value, using the processor to compute a
rolling average of the local color plane correction values using
the respective local color plane correction values associated with
the subsequent copies of the print job.
10. The method as in claim 1, wherein the color registration errors
include at least one of the following types: translation of the
color planes, skew of the color planes, rotation of the color
planes, or magnification of the color planes, or combinations
thereof, further comprising determining the first plurality of
color registration errors produced during the printing of the first
copy of the print job using a processor to determine a plurality of
color registration errors for each of the at least one type of
color registration errors with respect to a reference color
plane.
11. The method as in claim 3, wherein color registration errors
include at least one of the following types: translation of the
color planes, skew of the color planes, magnification of the color
planes, or combinations thereof, further including determining the
second plurality of color registration errors produced during the
printing of the second copy of the print job using a processor to
determine a plurality of color registration errors for each of the
at least one type of color registration errors with respect to a
reference color plane.
12. The method as in claim 1, wherein determining the first
plurality of color registration errors further includes: defining
local segments for the documents in the print job in an in-track or
a cross-track direction; printing a plurality of registration marks
corresponding to the defined local segments for each color plane;
and using the processor to measure the color registration errors
based on the corresponding each of the plurality of registration
marks for each color plane.
13. The method as in claim 12, further including printing the
plurality of registration marks in a margin area of the print
medium such that the printed registration marks lie outside a
printed document portion of the print job.
14. The method as in claim 12, wherein defining local segments
further comprises; determining regions of high ink laydown and low
ink laydown; and defining more local segments in high ink laydown
regions than in low ink laydown regions.
15. The method as in claim 1, further including using the processor
to smooth the local color correction values to provide smoothly
varying corrections for adjacent locations in the print job.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] Reference is made to commonly-assigned, U.S. patent
applications Ser. No. ______ (Docket K001471), entitled
"COLOR-TO-COLOR CORRECTION IN A PRINTING SYSTEM", Ser. No. ______
(Docket K001656), entitled "COLOR-TO-COLOR CORRECTION IN A PRINTING
SYSTEM", Ser. No. ______ (Docket K001658), entitled "COLOR-TO-COLOR
CORRECTION IN A PRINTING SYSTEM", Ser. No. ______ (Docket K001659),
entitled "COLOR-TO-COLOR CORRECTION IN A PRINTING SYSTEM", all
filed concurrently herewith.
TECHNICAL FIELD
[0002] The present invention generally relates to inkjet printing
systems and more particularly to performing color-to-color
registration correction in an inkjet printing system.
BACKGROUND
[0003] In a digitally controlled printing system, a print medium is
directed through a series of components. The print medium can be
cut sheet or a continuous web. As the print medium moves through
the printing system, liquid, for example, ink, is applied to the
print medium by one or more lineheads. This is commonly referred to
as jetting of the ink.
[0004] In commercial inkjet printing systems, the print medium is
physically transported through the printing system at a high rate
of speed. For example, the print medium can travel 650 to 1000 feet
per minute. The lineheads in commercial inkjet printing systems
typically include multiple printheads that jet ink onto the print
medium as the print medium is being physically moved through the
printing system. A reservoir containing ink or some other material
is usually behind each nozzle plate in a linehead. The ink streams
through the nozzles in the nozzle plates when the reservoirs are
pressurized.
[0005] The printheads in each linehead in commercial printing
systems typically jet only one color. Thus, there is a linehead for
each colored ink when different colored inks are used to print
content. For example, there are four lineheads in printing systems
using cyan, magenta, yellow and black colored inks. The content is
printed by jetting the colored inks sequentially, and each colored
ink deposited on the print medium is known as a color plane. The
color planes need to be aligned, or registered with each other so
that the overlapping ink colors produce a quality single image.
[0006] Color registration errors can be partitioned into different
types. Examples of color registration errors include, but are not
limited to, a color plane having a linear translation with respect
to another color plane, a color plane being rotated with respect to
another color plane, and a color plane being stretched, contracted,
or both stretched and contracted in different regions or in
different directions with respect to another color plane.
[0007] There are several variables that contribute to the
registration errors in color plane alignment including physical
properties of the print medium, conveyance of print medium, ink
application system, ink coverage, and drying of ink. Color
registration errors are typically managed by controlling these
variables. However, controlling these variables can often restrict
the range of desired print applications. For example, color plane
to color plane registration errors will typically become larger
than desired as paper weight for the print application is reduced,
when ink coverage is increased, or when the amount of ink coverage
becomes more variable between printed documents. These limitations
compromise the range of suitable applications for ink jet printing
systems.
SUMMARY
[0008] A method for performing color-to-color correction for
printing multiple copies of a print job having one or more
documents comprises printing a first copy of the print job using a
plurality of color planes, determining a first plurality of color
registration errors produced during the printing of the first copy
of the print job, for each document in the print job, using a
processor to determine a first plurality of local color plane
correction values for each color registration error produced during
the printing of the first copy of the print job, wherein each of
the first plurality of local color plane correction values
corresponds to one of the first plurality of color registration
errors, and printing a second copy of the print job using the local
color plane correction values for each document in the print
job.
[0009] (DOCKET 4) A printing system for printing multiple copies of
a print job having one or more documents comprises a plurality of
printheads adapted to print on a print medium, wherein each of the
plurality of printheads prints each of a plurality of color planes
of a first copy of the print job, a processor to determine a first
plurality of color registration errors produced during the printing
of the first copy of the print job, and to determine a first
plurality of local color plane correction values for each document
of the print job, wherein each of the first plurality of local
color plane correction values corresponds to one of the first
plurality of color registration errors, and the plurality of
printheads printing a second copy of the print job using the local
color plane correction values for each document in the print
job.
[0010] Advantages of the present invention include reducing
color-to-color registration errors when printing multiple copies of
a print job. Local adjustments to the global color plane correction
values permit finer corrections to be made to the documents, which
is especially advantageous when the document contains a mix of
information types such as text and images.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] Embodiments of the invention are better understood with
reference to the following drawings. The elements of the drawings
are not necessarily to scale relative to each other.
[0012] FIG. 1 is a schematic of a continuous web inkjet printing
system;
[0013] FIG. 2 is a schematic of a portion of printing system 100 in
more detail;
[0014] FIG. 3 illustrates a print job including a number of
documents according to an aspect of the invention;
[0015] FIG. 4 illustrates one example of a color registration error
produced by the translation of one color plane relative to another
color plane;
[0016] FIG. 5 illustrates one example of a color registration error
produced by the rotation of one color plane relative to another
color plane;
[0017] FIG. 6 illustrates one example of a color registration error
produced by the contraction of one color plane relative to another
color plane;
[0018] FIG. 7 depicts one example of plots of the repeatability of
color-to-color registration errors in the cross-track
direction;
[0019] FIG. 8 depicts one example of plots of the repeatability of
color-to-color registration errors in the in-track direction;
[0020] FIG. 9 depicts one example of plots of the repeatability of
color-to-color registration errors in the cross-track
direction;
[0021] FIG. 10 depicts one example of plots of the repeatability of
color-to-color registration errors in the in-track direction;
[0022] FIG. 11 depicts one example of plots of globally corrected
color-to-color registration errors in the cross-track
direction;
[0023] FIG. 12 depicts one example of plots of globally corrected
color-to-color registration errors in the in-track direction;
[0024] FIG. 13 depicts one example of plots of globally corrected
color-to-color registration errors in the cross-track
direction;
[0025] FIG. 14 depicts one example of plots of globally corrected
color-to-color registration errors in the in-track direction;
[0026] FIG. 15 depicts one example of registration marks alongside
a document in the margins outside the boundaries of the
document;
[0027] FIG. 16 depicts one example of local cross-track
color-to-color registration errors for a print job including seven
documents each measured in ten segments;
[0028] FIG. 17 depicts one example of local in-track color-to-color
registration errors for a print job including seven documents each
measured in ten segments;
[0029] FIG. 18 depicts one example of local cross-track
color-to-color magnification registration errors for a print job
including seven documents each measured in ten segments;
[0030] FIG. 19 depicts one example of local in-track color-to-color
skew registration errors for a print job including seven documents
each measured in ten segments;
[0031] FIG. 20 depicts one example of registration marks alongside
a document in the margins outside the boundaries of the document,
as well as inside the boundaries of the document;
[0032] FIG. 21 is a flowchart for a method for printing multiple
copies of a print job according to aspects of the invention;
[0033] FIG. 22 is a flowchart for a method for determining
color-to-color registration errors; and
[0034] FIG. 23 is a flowchart for a method for printing multiple
print jobs according to an aspect of the invention.
DETAILED DESCRIPTION
[0035] Throughout the specification and claims, the following terms
take the meanings explicitly associated herein, unless the context
clearly dictates otherwise. The meaning of "a," "an," and "the"
includes plural reference, the meaning of "in" includes "in" and
"on."Additionally, directional terms such as "on", "over", "top",
"bottom", "left", "right" are used with reference to the
orientation of the Figure(s) being described. Because components of
aspects of the present invention can be positioned in a number of
different orientations, the directional terminology is used for
purposes of illustration only and is in no way limiting.
[0036] The present description will be directed in particular to
elements forming part of, or cooperating more directly with, a
system in accordance with the present invention. It is to be
understood that elements not specifically shown, labeled, or
described can take various forms well known to those skilled in the
art. In the following description and drawings, identical reference
numerals have been used, where possible, to designate identical
elements. It is to be understood that elements and components can
be referred to in singular or plural form, as appropriate, without
limiting the scope of the invention.
[0037] The example aspects of the present invention are illustrated
schematically and not to scale for the sake of clarity. One of
ordinary skill in the art will be able to readily determine the
specific size and interconnections of the elements of the example
aspects of the present invention.
[0038] As described herein, the example aspects of the present
invention are applied to color plane registration in inkjet
printing systems. However, many other applications are emerging
which use inkjet printheads or similar nozzle arrays to emit fluids
(other than inks) that need to be finely metered and deposited with
high spatial precision. Such liquids include inks, both water based
and solvent based, that include one or more dyes or pigments. These
liquids also include various substrate coatings and treatments,
various medicinal materials, and functional materials useful for
forming, for example, various circuitry components or structural
components. In addition, a nozzle array can jet out gaseous
material or other fluids. As such, as described herein, the terms
"liquid", "ink" and "inkjet" refer to any material that is ejected
by a nozzle array. For simplicity and clarity of description, the
invention will be described in terms of a multi-color printer. It
must be understood that the invention similarly applies to other
applications such as the printing of multiple layers of an
electronic circuit where the individual circuit layers would
correspond to an image plane in the color printer. In such
applications, registration of the individual layers must be
maintained for proper operation of the electronic circuit in a
similar manner to the registration of the color image planes in the
color prints. It is anticipated that many other applications may be
developed in which the invention may be employed to enhance the
registration of the image planes.
[0039] Inkjet printing is commonly used for printing on paper.
However, printing can occur on any substrate or receiving medium.
For example, vinyl sheets, plastic sheets, glass plates, textiles,
paperboard, and corrugated cardboard can comprise the print medium.
Additionally, although the term inkjet is often used to describe
the printing process, the term jetting is also appropriate wherever
ink or other fluid is applied in a consistent, metered fashion,
particularly if the desired result is a thin layer or coating.
[0040] Inkjet printing is a non-contact application of an ink to a
print medium. Typically, one of two types of ink jetting mechanisms
are used and are categorized by technology as either drop on demand
ink jet (DOD) or continuous ink jet (CIJ). The first technology,
"drop-on-demand" (DOD) ink jet printing, provides ink drops that
impact upon a recording surface using a pressurization actuator,
for example, a thermal, piezoelectric, or electrostatic actuator.
One commonly practiced drop-on-demand technology uses thermal
actuation to eject ink drops from a nozzle. A heater, located at or
near the nozzle, heats the ink sufficiently to boil, forming a
vapor bubble that creates enough internal pressure to eject an ink
drop. This form of inkjet is commonly termed "thermal ink jet
(TIJ)."
[0041] The second technology commonly referred to as "continuous"
ink jet (CIJ) printing, uses a pressurized ink source to produce a
continuous liquid jet stream of ink by forcing ink, under pressure,
through a nozzle. The stream of ink is perturbed using a drop
forming mechanism such that the liquid jet breaks up into drops of
ink in a predictable manner. One continuous printing technology
uses thermal stimulation of the liquid jet with a heater to form
drops that eventually become print drops and non-print drops.
Printing occurs by selectively deflecting drops so that print drops
reach the print medium and non-print drops are caught by a
collection mechanism. Various approaches for selectively deflecting
drops have been developed including electrostatic deflection, air
deflection, and thermal deflection.
[0042] Additionally, there are typically two types of print medium
used with inkjet printing systems. The first type is commonly
referred to as a continuous web while the second type is commonly
referred to as cut sheet(s). The continuous web of print medium
refers to a continuous strip of print medium, generally originating
from a source roll. The continuous web of print medium is moved
relative to the inkjet printing system components via a web
transport system, which typically includes drive rollers, web guide
rollers, and web tension sensors. Cut sheets refer to individual
sheets of print medium that are moved relative to the inkjet
printing system components via a support mechanism (e.g., rollers
and drive wheels or a conveyor belt system) that is routed through
the inkjet printing system.
[0043] The invention described herein is applicable to both types
of printing technologies. As such, the terms linehead and
printhead, as used herein, are intended to be generic and not
specific to either technology. Additionally, the invention
described herein is applicable to both types of print medium. As
such, the terms print medium, and web, as used herein, are intended
to be generic and not as specific to one type of print medium or
web or the way in which the print medium or web is moved through
the printing system. Additionally, the terms linehead, printhead,
print medium, and web can be applied to other nontraditional inkjet
applications, such as printing conductors on plastic sheets.
[0044] The terms "color plane" and "image plane" are used
generically and interchangeably herein to refer to a portion of the
data that is used to specify the location of features that are made
by a particular station of a digitally controlled printing system
on the print medium. Similarly, "color-to-color registration" is
used generically herein to refer to the registration of such
features that are made by different stations on the print medium.
For color printing of images, the patterns of dots printed by
different printheads in printing the same or different colors must
be registered with each other to provide a high quality image. An
example of a non-color printing application is functional printing
of a circuit. The patterns of dots printed by different printheads,
the image planes, form directly or serve as catalysts or masks for
the formation of different layers of deposited conductive
materials, semiconductor materials, resistive materials, insulating
materials of various dielectric constants, high permeability
magnetic materials, or other types of materials, must also be
registered to provide a properly functioning circuit. The terms
color plane and color-to-color registration can also be used herein
to refer to the mapping and registration of pre-print or finishing
operations, such as the mapping of where the folds or cutting or
slitting lines are, or the placement of vias in an electrical
circuit.
[0045] The terms "upstream" and "downstream" are terms of art
referring to relative positions along the transport path of the
print medium; points on the transport path move from upstream to
downstream. In FIGS. 1-6 the print medium moves in a direction
indicated by transport direction arrow 114. Where they are used,
terms such as "first", "second", and so on, do not necessarily
denote any ordinal or priority relation, but are simply used to
more clearly distinguish one element from another.
[0046] The schematic side view of FIG. 1 shows one example of a
continuous web inkjet printing system. Printing system 100 includes
a first tower 102 and a second tower 104, each of which includes
lineheads 106, dryers 108, and a quality control sensor 110. Each
linehead 106 typically includes multiple printheads (not shown)
that apply ink or another fluid (gas or liquid) to the surface of
the print medium 112 that is adjacent to the printheads. For
descriptive purposes only, the lineheads 106 are labeled a first
linehead 106-1, a second linehead 106-2, a third linehead 106-3,
and a fourth linehead 106-4. In the illustrated aspect, each
linehead 106-1, 106-2, 106-3, 106-4 applies a different colored ink
to the surface of the print medium 112 that is adjacent to the
lineheads. By way of example only, linehead 106-1 applies cyan
colored ink, linehead 106-2 magenta colored ink, linehead 106-3
yellow colored ink, and linehead 106-4 black colored ink.
[0047] The first tower 102 and the second tower 104 also include a
web tension system that serves to physically move the print medium
112 through the printing system 100 in the transport direction 114
(left to right as shown in the figure). The print medium 112 enters
the first tower 102 from a source roll (not shown) and the
linehead(s) 106 of the first tower applies ink to one side of the
print medium 112. As the print medium 112 feeds into the second
tower 104, a turnover module 116 is adapted to invert or turn over
the print medium 112 so that the linehead(s) 106 of the second
tower 104 can apply ink to the other side of theZ print medium 112.
The print medium 112 then exits the second tower 104 and is
collected by a print medium receiving unit (not shown).
[0048] Processor 118 can be connected to various components in the
web tension system and used to control the positions of the
components, such as gimbaled or caster rollers. Processor 118 can
be connected to the quality control sensor 110 and used to process
images or data received from the sensor 110. Processor 118 can be
connected to components in printing system 100 using any known
wired or wireless communication connection. Processor 118 can be a
separate from printing system 100 or integrated within printing
system 100 or within a component in printing system 100. Processor
118 can be a single processor or one or more processors. Each of
the one or more processors can be separate from the printing system
or integrated within the printing system.
[0049] One or more storage devices 120 are connected to the
processor 118. The storage device 120 can store color plane
correction values in an aspect of the invention. The storage device
120 can be implemented as one or more external storage devices; one
or more storage devices included within the processor 118; or a
combination thereof. The storage device can include its own
processor and can have memory accessible by the one or more
processors 118.
[0050] FIG. 2 illustrates a portion of printing system 100 in more
detail. As the print medium 112 is moved through printing system
100, the lineheads 106, which typically include a plurality of
printheads 200, apply ink or another fluid onto the print medium
112 via the nozzle arrays 202 of the printheads 200. The printheads
200 within each linehead 106 are located and aligned by a support
structure 204 in the illustrated aspect. After the ink is jetted
onto the print medium 112, the print medium 112 passes beneath the
one or more dryers 108 which apply heat or air 206 to the ink on
the print medium.
[0051] Referring now to FIG. 3, there is shown one example of a
print job 300 including a number of documents to be printed in
sequential order. As used herein, the term "print job" refers to
information to be printed more than once, the print job 300
includes one or more documents, and the content in the information
is substantially the same each time a copy of the information or a
document is printed. The information to be printed can have some
variations. For example, a report that is sent to multiple
recipients can vary the name and address of the recipient in each
printing of the report while maintaining the consistency of the
rest of the information to be printed. Examples of such information
include, but are not limited to, books, magazines, reports, and
transactions.
[0052] A print job includes a sequence of N number of documents,
where N is equal to or greater than one. In the illustrated aspect,
the print job 300 includes N documents with each document having
two pages, for example 302 and 304, 306 and 308, 310 and 312, and
314 and 316. A book is one example of a print job that is arranged
as the print job 300 depicted in FIG. 3.
[0053] A print job can have one document positioned across the
width of the print medium in an aspect of the invention. The print
job depicted in FIG. 3 illustrates one document positioned across
the width on the print medium. In other aspects, a print job can
have multiple documents positioned across the width of the print
medium. A document can include any printed output such as, for
example, text, graphics, or photos, individually or in various
combinations. The printed output can be disposed anywhere on the
print medium, and the printed output in each document can differ
from the printed content in the other documents in a print job.
[0054] When the print job is printed, the print medium can receive
varying amounts of ink during printing. In turn, the aqueous
component of the ink is absorbed into the print medium and can
cause the print medium to swell and stretch, especially with
water-based ink or in high ink laydown regions of the printed
content (e.g. an image with a lot of dense black background) and if
the print medium is under tension. Stretch can be higher in the
direction of movement (i.e., the in-track or transport direction)
than in the cross-track direction.
[0055] Additionally, drying of the print medium can cause the print
medium to shrink. When the print medium is heated in between
lineheads, regions of the print medium can be stretched and shrunk
one or more times as the print medium moves through the printing
system.
[0056] Printing with several color planes in which each color
record is printed sequentially requires color laydown registration.
Unanticipated or unaccounted for stretch or shrink in the print
medium can produce a loss of color registration and can lead to
blurry content or hue degradation. Additionally, printing on both
sides of the print medium usually requires front-to-back
registration, and the second side of the print medium is usually
printed significantly later than the first side.
[0057] FIG. 4 depicts one example of cross-track and in-track color
registration errors produced by the translation of a color plane
relative to another color plane. Relative translation is one type
of color registration error. Typically, one color plane is used as
a reference color plane 400. By way of example only, the reference
color plane can be black. Errors in registration for the remaining
color planes can be determined by comparing each color plane to the
reference color plane. Color plane 402 is shifted or translated
with respect to the reference color plane 400. Color plane 402 has
color registration errors in both the in-track direction 404 and
the cross-track direction 406 in the illustrated aspect.
[0058] FIG. 5 illustrates one example of cross-track and in-track
color registration errors caused by the rotation of a color plane
relative to another color plane. Relative rotation or skew is
another type of color registration error. Color plane 502 is
rotated with respect to a reference color plane 400. Color plane
502 has color registration errors with respect to the reference
color plane 400 in both the in-track direction 404 and the
cross-track direction 406.
[0059] FIG. 6 depicts one example of cross-track and in-track color
registration errors caused by the stretch or contraction of a color
plane relative to another color plane. Stretch and contraction are
another type of color registration error. The different color
planes can be stretched or contracted by different amounts in the
cross-track and in-track directions. Color plane 602 is contracted
in both the in-track and cross-track directions with respect to the
reference color plane 400. Color plane 602 has color registration
errors in both the in-track direction 404 and the cross-track
direction 406.
[0060] The stretching or shrinking can occur in the in-track
direction, the cross-track direction, or both the in-track and
cross-track directions. Alternatively, one color plane can contract
in one direction (e.g., cross-track direction) and stretch in the
other direction (e.g., in-track direction) in other aspects of the
invention. These shifts and distortions need not be uniform across
the document. As a result, certain regions of a document may
exhibit expansion while other regions may exhibit no expansion or
may even show contraction. And finally, other aspects of the
invention can have various combinations of the types of color
registration errors shown in FIGS. 4-6, or can have different types
of color registration errors.
[0061] The color registration errors can repeat each time a copy of
a sequence of documents in a print job is printed. Moreover, the
repeating color registration errors can be specific to each
document in the print job, and more specifically to particular
regions within the individual documents. For example, in a print
job having a sequence of three documents which are repeatedly
printed in sequential order, the color registration errors in the
second document can repeat each time the second document is
printed. The color registration errors for the third document can
be different from the color registration errors for the second
document. And the color registration errors in the third document
can repeat each time the third document is printed. Furthermore
within the second document, there can be regions of the document
which exhibit one level of particular type of registration error
that is consistently different than the corresponding registration
error in a different region in the same document for each copy of
the second document that is printed.
[0062] FIG. 7 illustrates one example of plots of the repeatability
of color-to-color registration errors in tower 102 in the
cross-track direction. A plot 700 shows the registration errors of
a first ink color relative to the reference color; plot 702 shows
the corresponding registration errors for a second ink color, and a
plot 704 shows the corresponding registration errors for a third
ink color. For example, the first ink color can be cyan, the second
ink color magenta, and the third ink color yellow, with the
reference color being black.
[0063] The color registration errors for the examples shown in
FIGS. 7-10 can be determined by comparing each color plane to a
reference color plane, and the color registration errors can be
produced by one or any combination of registration error types:
color plane translation, color plane rotation, and color plane
stretch or contraction in each of the in-track and cross-track
directions as depicted in FIGS. 4-6. These registration errors can
be measured by means of an image sensor, which captures an image of
test marks printed by the various lineheads, as described in U.S.
Pat. No. 8,104,861. By way of example only, the reference color can
be black. Additionally, the print job associated with the examples
shown in FIGS. 7-10 includes a sequence of seven documents which is
repeatedly printed in sequential order. Each plotted point on the
plots represents one of the seven documents in the repeated
sequence of the seven documents.
[0064] The variations in the color-to-color registrations for each
document are shown in each period of the waveform, and the
repeatability of the color-to-color registration errors is
identifiable from one copy of the sequence of seven documents to
another. By way of example only, document 2 repeatedly has a
registration error at the positive peak of each waveform while the
registration errors for documents 1 and 4 are less than the error
for document 2. The registration errors for documents 3 and 7 are
less than the errors for documents 1 and 4, and the registration
errors for documents 5 and 6 repeatedly fall at the bottom of the
waveforms. The repeatability of this pattern is a result of the
repeated sequential printing of the documents. The amount and type
of color registration error for a document is related to the
printing conditions for that document, such as the quantity and
location of ink laydown for that document. If the documents were
printed in a random order, then the registration errors for each
copy would not be repeatable.
[0065] FIG. 8 illustrates one example of plots of the repeatability
of color-to-color registration in tower 102 in the in-track
direction. A plot 800 for the first ink color, a plot 802 for the
second ink color, and a plot 804 for the third ink color are shown.
In the in-track direction, document 5 repeatedly has a registration
error at the positive peak of each waveform while the registration
errors for documents 1 and 4 are less than the error for document
5. The registration error for document 7 is less than the errors
for documents 1 and 4, and the registration errors for documents 2,
3, and 6 repeatedly lie at the bottom of the waveforms.
[0066] Referring now to FIG. 9, there is shown one example of plots
of the repeatability of color-to-color registration in tower 104 in
the cross-track direction. A plot 900 for a first ink color, a plot
902 for a second ink color, and a plot 904 for a third ink color
relative to the reference color are depicted. In this example, in
the cross-track direction in the second tower (tower 104), document
7 repeatedly has a registration error at the positive peak of each
waveform while the registration error for document 4 is less than
the error for document 7. The registration error for document 2 is
less than the registration error for document 4. The registration
error for document 1 is less than the registration error for
document 2. The registration error for document 3 is less than the
registration error for document 1. And the registration error for
document 5 is less than the registration error for document 6.
[0067] FIG. 10 illustrates one example of plots of the
repeatability of color-to-color registration in tower 104 in the
in-track direction. A plot 1000 for the first ink color, a plot
1002 for the second ink color, and a plot 1004 for the third ink
color are shown. In this example, in the in-track direction,
documents 3 and 5 repeatedly have registration errors at the
positive peak of each waveform while the registration error for
document 7 is less than the values for documents 3 and 5. The
registration errors for documents 1 and 2 are less than the error
for document 7, and the registration errors for documents 4 and 6
repeatedly fall at the bottom of the waveforms.
[0068] U.S. patent application Ser. No. 13/664,472 (filed Apr. 26,
2012), which is herein incorporated by reference in its entirety,
discloses a method for performing color-to-color correction while
printing multiple copies of a print job having one or more
documents where the method includes printing one or more copies of
the print job and determining at least one color registration error
for at least one type of color registration error produced during
the printing of the one or more copies of the print job. A color
plane correction value is then determined for each document in the
print job and for each color plane error produced during the
printing of the one or more copies of the print job. One or more
subsequent copies of the print job is printed using the color plane
correction values, where the color plane correction values used for
each document are the correction values determined for that
document. The color plane correction values can be updated
periodically, at select times, or after each copy is printed.
Herein, color plane corrections that are made on an entire document
(as disclosed in U.S. patent application Ser. No. 13/664,472) will
be referred to as global color plane corrections.
[0069] Improved color-to-color registration resulting from global
color plane corrections that are made as described in U.S. patent
application Ser. No. 13/664,472 are shown in FIGS. 11-14. Referring
now to FIG. 11, there is shown one example of plots of the globally
corrected color-to-color registration errors in tower 102 in the
cross-track direction, while FIG. 12 illustrates one example of
plots of the globally corrected color-to-color registration errors
in the in-track direction for tower 102. Plots 1100 and 1200
correspond respectively to plots 700 and 800 of the first ink color
shown in FIGS. 7 and S after the global color to color registration
corrections have been applied; plots 1102 and 1202 correspond
respectively to plots 702 and 802 of the second ink color
illustrated in FIGS. 7 and 8, and plots 1104 and 1204 correspond
respectively to plots 704 and 804 of the third ink color depicted
in FIGS. 7 and 8.
[0070] The registration errors for the examples shown in FIGS.
11-14 are determined by comparing each color plane to a reference
color plane. Additionally, the print job associated with the
examples shown in FIGS. 11-14 includes seven documents. Each
plotted point on the plots represents one of the seven
documents.
[0071] The variations in the color-to-color registrations for each
document are shown in each period of the waveform, and the
magnitude of the color-to-color registration errors shown in FIGS.
11-12 for tower 102 is significantly reduced compared to the
registration errors shown in FIGS. 7-8. Regions 1106 and 1206 of
the plots depict the color registration errors associated with the
beginning of the printing of the documents in the print job. As can
be seen, the color-to-color registration errors are larger compared
to the later or subsequent copies of the print job. This is mostly
due to the fact that the color plane correction values are not as
finely tuned or updated when the earlier copies are printed
compared to the later copies.
[0072] FIG. 13 depicts one example of plots of the globally
corrected color-to-color registration in tower 104 in the
cross-track direction, while FIG. 14 illustrates one example of
plots of the globally corrected color-to-color registration in
tower 104 in the in-track direction according to the method
disclosed in U.S. patent application Ser. No. 13/664,472. Plots
1300 and 1400 correspond respectively to plots 900 and 1000 of the
first ink color shown in FIGS. 9-10; plots 1302 and 1402 correspond
respectively to plots 902 and 1002 of the second ink color
illustrated in FIGS. 9-10, and plots 1304 and 1404 correspond
respectively to plots 904 and 1004 of the third ink color depicted
in FIGS. 9-10.
[0073] The magnitude of the color-to-color registration errors
shown in FIGS. 13-14 for tower 104 is significantly reduced
compared to the registration errors in FIGS. 9-10. Regions 1306 and
1406 of the plots depict the color registration errors associated
with the beginning of the printing of the documents in the print
job. As can be seen, the color-to-color registration errors are
larger compared to the later or subsequent copies of the print job.
This is mostly due to the fact that the color plane correction
values are not as finely tuned or updated when the earlier copies
are printed compared to the later copies.
[0074] As described above, the method described in U.S. patent
application Ser. No. 13/664,472 is very effective for providing
color-to-color correction on a document by document basis so that
there is little to no visible periodicity seen in the plots of
FIGS. 11-14. The method of U.S. patent application Ser. No.
13/664,472, however does not compensate for repeatable color
registration errors within each document. As discussed above,
shifts and distortions need not be uniform across a document. Due
to different ink laydown patterns within a document, for example,
different regions of a document can exhibit different amounts of
expansion and contraction. Color plane corrections that are made on
a region-by-region basis within a document according to aspects of
the present invention will be referred to herein as locally
adjusted color plane corrections.
[0075] Referring to FIG. 15, Document N is shown on web of print
medium 112. Registration marks 1504 can be located in margins 1502
outside the boundaries of Document N so that when the documents are
cut from the print medium 112 after printing, there are no
registration marks 1504 appearing within the documents. In other
aspects of the invention, the registration marks can be located in
other portions of the print medium 112. In the example shown in
FIG. 15, the registration marks 1504 include patterns of dots that
have been printed by different printheads. For example, element
1506 is a line of cyan dots, element 1508 is a line of magenta
dots, element 1510 is a line of yellow dots and element 1512 is a
line of black dots. Other registration mark configurations
(cross-hairs, etc.) could alternatively be used. A quality control
sensor 110 (FIG. 1) can be positioned relative to each of the two
margins 1502, such that as the print medium 112 is advanced along
the transport direction 114, each registration mark can be viewed
as it comes into the field of view of quality control sensor 110.
Signals are sent from quality control sensor 110 to processor 118
(FIG. 1) so that the actual printed positions of elements 1506,
1508, 1510, and 1512 can be obtained and compared to ideal relative
positions if there were no color-to-color registration error. The
difference is the color-to-color registration error, which can be
separated into different types of error including translation,
rotation, expansion and contraction. By having a plurality of
registration marks 1504 alongside or within each document, the
local color-to-color registration errors are determined for
corresponding regions within each document of a print job. In other
aspects of the invention, information printed within each document
can be used as registration marks for measuring color-to-color
registration errors.
[0076] Each time another copy of the print job is printed in the
same document sequential order, a plurality of local color-to-color
registration errors for one or more types of color registration
errors can be determined for each document in the print job and
stored in memory as a look-up table, as color registration errors,
or in the form of color plane correction values, determined from
the color registration errors, to be used for printing subsequent
copies of the print job. The plurality of color registration errors
for one of the types of color registration errors correspond to a
plurality of image regions with the documents. For example, a
document may comprise multiple segments in the in-track direction.
In the examples shown in FIGS. 16-19, each document in a print job
having seven documents has been segmented into 10 segments in the
in-track direction. The documents in FIGS. 16-19 have only a single
segment spanning the crosstrack direction of the document. This
number of segments is not restrictive; the documents can be
segmented into various numbers of segments in both the in-track and
cross-track directions.
[0077] FIG. 16 shows a plot 1602 of cross-track black to cyan
registration errors for each of the ten segments of each of the
seven documents for a single copy printed in the example print job.
The horizontal lines show the cross-track black to cyan
registration errors averaged over all ten segments (i.e. the global
color-to-color registration errors). Such averaging can include
providing a measure of central tendency such as a medium or a mean
of the errors, for example. For some documents, such as document 1,
there is significant variability of the cross-track black to cyan
registration error. For documents having significant variability,
it is clearly advantageous to apply local corrections within the
document, rather than a single average or global correction for the
entire document. For documents such as document 5, the cross-track
black to cyan registration error does not vary as much within the
document. FIG. 16 also shows plot 1604 of registration errors for
thirty copies of the print job. The curves drawn through plot 1604
indicate a central tendency, such as a medium or a mean of the
registration errors for the thirty copies as a function of segment
in each document. These curves for plot 1604 are smoother and less
noisy than the registration errors measured for a single copy and
shown in plot 1602. It can be advantageous to use local
color-to-color registration errors measured over a plurality of
copies (as shown in plot 1604) rather than local color-to-color
registration errors measured for a single copy of the print job (as
shown in plot 1602) in determining the local color plane correction
values. The color plane correction values can be updated using
different known techniques. For example, a running average of each
local color plane correction value can be determined.
Alternatively, a rolling window of local color plane correction
values can be determined. The rolling window can include a number
of local color registration values. For example, the correction
values for the last five copies of the print job can be used to
update the local color plane correction values. Alternatively, the
local color plane correction values associated with every nth copy
of the print job, such as for every third or fifth copy, can be
used to update the local color plane correction values.
Alternatively various algorithms can be used which update the local
color plane corrections values on a non-periodic basis. Prior to
updating of the local color plane correction values, various
statistical tests can be applied to the new data to confirm that
the printing process is stable and within normal control limits,
and to confirm that the new data doesn't represent outlier data
that could adversely shift the color plane correction values.
[0078] FIGS. 17-19 are similar to FIG. 16. FIG. 17 shows a plot
1702 of in-track black to cyan registration errors for each of ten
segments of each of seven documents for a single copy printed in
the example print job. FIG. 17 also shows a plot 1704 of in-track
black to cyan registration errors for thirty copies of the example
print job. FIG. 18 shows a plot 1802 of cross-track black to cyan
magnification (i.e. expansion or contraction) registration errors
for each of ten segments of each of seven documents for a single
copy printed in the example print job. FIG. 18 also shows a plot
1804 of cross-track black to cyan magnification registration errors
for thirty copies of the example print job. FIG. 19 shows a plot
1902 of in-track black to cyan skew (i.e. rotation) registration
errors for each of ten segments of each of seven documents for a
single copy printed in the example print job. FIG. 19 also shows a
plot 1904 of in-track black to cyan skew registration errors for
thirty copies of the example print job.
[0079] In FIGS. 16-19, the ten segments disposed along the in-track
direction are shown as each having the same size within a document
and from document to document. In alternate aspects, the number and
size of the segments can vary from document to document within the
repeated sequence of documents. In other aspects, the size of the
plurality of segments within a document can vary from segment to
segment. In some aspects, number and relative size of the segments
within a document is determined based on the image content within
the document. Referring again to FIG. 15, this can be accomplished
by varying the placement of registration marks 1504 as a function
of the printed image content in order to measure local color
registration errors where such errors are most likely to occur. For
example, for a document having a high print density color
photograph and regions of low print density text, registration
marks 1504 can be printed at locations corresponding to the top and
the bottom of the photograph, as well as a number of locations
between the top and the bottom. Registration marks 1504
corresponding to a high print density region can be spaced more
closely than registration marks 1504 corresponding to a low print
density text region. Varying the number and size of the segments
permits finer segments in regions of a document having either a
high density of ink coverage, or a large gradient in ink coverage,
areas in which one might expect more distortion in the printed
image, without requiring the same gradation of segments in regions
have little or no ink coverage.
[0080] Other aspects of the invention can determine the color
registration errors differently. By way of example only, a target
location on the web is identified and the color registration error
of each color plane is measured from the target.
[0081] Local color plane correction values for each document in the
print job, for the types of color registration errors, and for each
color plane are determined and stored in memory. For example, the
global and local color plane correction values can be stored in a
look-up table in storage device 120 (FIG. 1). In a particular
example, local color correction values are determined for three
different types of color registration errors, translation,
rotation, and stretch or contraction. The local color registration
errors are also determined for the in-track and cross-track
directions. So for each document printed using four color planes,
eighteen local color correction values are determined and stored in
for each segment in the respective locations in the look-up table.
The color correction values can be any value, including zero.
[0082] Four different ink colors are used in the example. The four
ink colors can be black, magenta, cyan, and yellow, with black
serving as the reference color. Thus, the color correction values
are determined for black-to-cyan (B-C), black-to-magenta (B-M), and
black-to-yellow (B-Y) for one or more of the types of registration
errors.
[0083] As described earlier, local color correction values are
determined for each segment of each document in a print job, for
each type of color registration error, and for each color plane in
a document. Thus, the color correction values are specific to each
segment of each document. For example, the color correction value
determined for segment 5 of document 1 regarding translation in the
cross-track direction for black-to-cyan (B-C) can be different from
the color correction /value determined for segment 2 of document 7
for the same type of color registration error (i.e., translation in
the cross-track direction for black-to-cyan (B-C)).
[0084] Local color-to-color registration corrections within each
document should be sufficiently smoothly varying and at a small
enough rate of change so that image artifacts are not introduced
for neighboring segments. Methods for providing smoothly varying
corrections can include using linear interpolation to adjust local
corrections for adjacent segments. Interpolation with curvature can
be used if needed. A smooth curve, such as a spline function
(piecewise defined polynomial functions having matching values and
matching slopes at segment boundaries), can be used to provide
gradually varying local color correction values. Smoothly varying
functions can be particularly useful when correcting the first few
copies of the print job, before the natural smoothing caused by
averaging (as discussed above) occurs. If there is minimal
variation in the local registration errors of a particular document
in a print job, such is in document 5 of FIG. 17 or document 6 of
FIG. 18, some aspects of the invention can forego making local
color plane corrections for those documents, but rather use a
global color plane correction for all segments of such pages.
[0085] In order to obtain better registration across the width of
the document it can be useful to have multiple segments in the
cross-track direction as well. Referring to FIG. 20, Document N is
shown on web of print medium 112. Registration marks 2004 are
located in margins 1502 outside the boundaries of Document N. In
addition, registration marks 2006 are located within the boundaries
of the printed document. Registration marks 2006 would typically be
placed inside the printed document only for a few copies (the first
copy plus a few successive copies or a few periodic copies) for
improving the registration in the print job. Such documents with
registration marks on them could subsequently be discarded. In
addition, several quality control sensors 110 (FIG. 1) would need
to be positioned to view the registration marks as they pass while
print medium 112 is being advanced.
[0086] In some aspects of the invention, global color plane
corrections are not used, but rather the local color plane
corrections are applied directly. Such a method for performing
color-to-color correction for printing multiple copies of a print
job having one or more documents can be described as follows:
Receive a print job including one or more documents and a plurality
of color planes. Define a plurality of segments for at least one
document of the print job. Print a first copy of the print job
using a plurality of printheads to print the plurality of color
planes. Determine a first plurality of color registration errors
produced during the printing of the first copy of the at least one
document of the print job on a segment by segment basis. For each
segment of the at least one document in the print job, use a
processor to determine a local color plane correction value for at
least one color plane error produced during the printing of the
first copy of the print job based on the first plurality of color
registration errors. Print a second copy of the print job using the
local color plane correction values for the at least one document
in the print job.
[0087] In other aspects of the invention, global color plane
corrections are made first, and then local color plane corrections
are implemented as an adjustment to the global color plane
corrections. Such a method for performing color-to-color correction
for printing multiple copies of a print job having one or more
documents can be described as follows: Print a first copy of the
print job having a plurality of color planes. Determine a first
plurality of color registration errors produced during the printing
of the first copy of the print job. For each document in the print
job, use a processor to determine a global color plane correction
value for each color plane error produced during the printing of
the first copy of the print job based on the first plurality of
color registration errors. For each document in the print job, use
the processor to determine a first plurality of local color plane
correction values for each color registration error produced during
the printing of the first copy of the print job, where each of the
first plurality of local color plane correction values corresponds
to one of the first plurality of color registration errors. For
each document in the print job, use the processor to locally adjust
the global color plane correction value for each of the plurality
of color planes based on the first plurality of local color plane
correction values. Print a second copy of the print job using the
locally adjusted global color plane correction values for each
document in the print job. This "second copy" does not necessarily
have to be the copy printed after the first copy of the print job.
For example, for the copy printed immediately following the first
copy of the print job the global color plane corrections can be
used, and for a copy printed subsequent to that copy, the locally
adjusted global color plane corrections can be used.
[0088] FIG. 21 is a flowchart for a method for correction
color-to-color registration errors according to an aspect of the
invention. At step 2100 local segments are defined within the
documents of the print job. At step 2102 the first copy of the
print job is printed. Steps 2104, 2106 and 2108 on global color
plane registration errors can be optional in some aspects of the
invention. At step 2104 global color plane registration errors are
determined. At step 2106 global color plane correction values for
each document are determined. At step 2108 a copy of the print job
can be printed using the global color plane correction values. At
step 2110 local color plane registration errors are determined. At
step 2112 local color plane registration corrections are
determined. If global color plane correction values have been
determined, the local color plane correction values can be
determined as an adjustment to the global color plane correction
values for each local segment. In this aspect of the invention, the
local color plane correction values are called locally adjusted
global color plane correction values. In other aspects of the
invention, steps 2104, 2106, and 2108 are optional. In these
aspects of the invention, local color plane registration errors are
determined and local color plane correction values produced for
each local segment in the documents of the print job with no global
color plane correction values being used. At step 2114 the local
color plane correction values or the locally adjusted global color
plane correction values are stored in the storage device. At step
2116 a subsequent copy of the print job is printed using the local
color plane correction values or the locally adjusted global color
plane correction values. At step 2118, the local color plane
correction values or the locally adjusted global color plane
correction values are updated using the local color plane
registration errors for the printing of the subsequent copy. The
steps of the method shown in FIG. 21 can be performed by one or
more processors. The steps can be performed by the same processor
or by different processors.
[0089] FIG. 22 shows a flowchart for a method for determining color
plane registration errors. At Step 2200, local segments are defined
for each document in the print job in the in-track direction. At
Step 2202, local segments are defined for each document in the
print job in the cross track direction. At Step 2204, a plurality
of registration marks, at least one for each local segment, is
printed on the print medium. As discussed earlier, the registration
marks can be printed in the margin area of the print medium or in
the printed document area. At Step 2206, the color registration
errors are determined using the printed registration marks. Each of
the local registration marks, corresponding to each of the local
segments, produces a local color registration error. The local
color plane registration errors for all the local segments of a
document can be combined to produce global color plane registration
errors. The steps of the method shown in FIG. 22 can be performed
by one or more processors. The steps can be performed by the same
processor or by different processors.
[0090] In some aspects of the invention, the local color plane
correction values determined during the printing of a print job are
saved in the storage device for use at a later time. This can be
useful, for example, to a book printer. The local color plane
correction values determined during the printing of a batch of a
certain book are stored. When a second print job comprising an
additional batch of the same book is ordered at a later date, the
stored set of local color plane correction values can be retrieved
from memory and can be used during the printing of the additional
batch. The retrieved local color plane correction values can even
be used for the printing of the first copy of the book in this
additional batch so that the color to color registration of even
the first copy of the book is enhanced through the use of the local
color plane correction values. After the printing of the second
print job, the local color plane correction values can be updated
and refined for subsequent use.
[0091] The local color plane correction values are effective in
improving the color to color registration because the documents are
printed in the same sequence each time. In the first print job,
comprised of printing multiple copies of a book, the first document
of a copy of the book would be printed following the last document
of the previous copy of the book. The local color plane correction
values for the first document in the book, therefore, are
appropriate when the first document of the book follows the
printing of the last several documents of the book. In some aspects
of the invention, when a second print job calls for printing
additional copies of the book, the printer controller will not only
retrieve the local color plane correction values from memory, but
will also begin the printing process by preceding the printing of
the first document of the book with printing a sequence of the last
several documents in the book. In this way, the first document of
the book is printed in the same sequence as it was when the local
color plane correction values were determined. The result is
enhanced color to color registration for the first page of the
book. The documents which the controller caused to be printed prior
to the first document of the second print job can then be diverted
by the controller or other means to waste after they are
printed.
[0092] In a similar manner, the local color plane correction values
determined for improving the color to color registration when
printing multiple copies of one print job can be useful for
improving the color-to-color registration printing of multiple
copies of a second print job in which the information content is
not identical but is substantially similar to image content in the
first print job. For example, the first print job and the second
print job may be different versions of a physics textbook in which
there are some notation changes for some of the parameters used in
the textbook. Another example could be two print jobs for printing
copies of an illustrated children's book in two different languages
in which none of the illustrations were changed between the two
versions. The text changes between the two print jobs might be
expected to result in little change of the color-to-color
registration as such text changes have small effect on the overall
ink coverage levels in one or more of the color or image planes
that can alter the local expansion or shrinkage of the print
medium. The effectiveness of the invention in using the local color
plane correction values determined in a first print job in reducing
color-to-color registration errors of a second print job is
dependent on how significant the content changes are from the first
print job to the second print job in terms of their propensity to
cause a particular type of color registration error. In particular,
the overall ink coverage levels in one or more of the color or
image planes that can alter the local expansion or shrinkage of the
print medium is dependent on information content changes; the
effectiveness of the method being degraded if significant local
regions of the print medium undergo changes in the expansion or
shrinkage of the print medium from one print job to another.
[0093] In some aspects of the invention, when a second print job is
received that is similar but not identical to a first print job,
the processor is used to evaluate or compute an amount of
difference between the corresponding documents in the first print
job and second print job. If the amount of difference is less than
a predetermined threshold amount, the local color plane correction
values determined during the printing of the first print job are
used to enhance the color to color registration during the printing
of the second print job. If the identified difference between the
first print job and the second print job exceeds the predetermined
threshold, the second print job is printed without using the local
color plane correction values of the first print job. In some
aspects of the invention, the evaluation of the differences between
the corresponding documents in the first print job and second print
job can include identifying a sub-sequence from the sequence of
documents in the print jobs that is the same in both the first and
the second print jobs, while another sub-sequence from the sequence
of documents in the print jobs that differs significantly between
the first and the second print jobs. In such aspects, the processor
can use the local color plane correction values determined during
the first print job, for the sub-sequence from the sequence of
documents in the print jobs that is the same in both the first and
the second print jobs, for the printing of the same sub-sequence in
the second print job. For the identified sub sequence of the second
print job that differed significantly from the sub-sequence of the
first print job, the local color plane correction values determined
from the first print job are not used. FIG. 23 shows a flowchart
for a method for printing multiple print jobs. The print jobs can
have some matching documents and some differing documents. The
differences can be within portions of one or more documents of the
print job. At Step 2300, a first print job is received and printed
using no color corrections at Step 2302. The color plane
registration errors for the first print job are determined at Step
2304, and local color plane correction values are produced at Step
2306. At Step 2308, a second print job is received. At Step 2310,
differences between the first and second print job are computed. At
Step 2312, the difference is compared to a predetermined threshold.
If the difference is less than the threshold, control flows to Step
2314 where the second job is printed using the local color plane
correction values produced in Step 2306 or stored in storage
device. If the difference is greater than the threshold, the second
print job can be printed without using the local color plane
correction values, or control can flow to Step 2316 where matching
and non-matching portions of the first and second print jobs are
determined. At Step 2318, matching portions of the second print job
can be printed using the local color plane correction values from
the first print job. At Step 2320, the non-matching portions are
printed without using the color plane correction values from the
first print job. The steps of the method shown in FIG. 23 can be
performed by one or more processors. The steps can be performed by
the same processor or by different processors.
[0094] The invention is useful not only for print jobs in which
multiple copies of a sequence of one or more documents are printed
where the content of each copy is identical to the content of each
other copy. It is also useful for print jobs in which at least a
portion of the information content differs from copy to copy, or
version to version. For example, a report that is sent to multiple
recipients can vary the name and address of the recipient in each
printing of the report while maintaining the consistency of the
rest of the information to be printed. Examples of such information
include, but are not limited to, books, magazines, reports, and
transactions. For such print jobs, the effectiveness of the
invention in reducing color to color registration errors is
dependent on how significant the content changes are from version
to version. In particular, the overall ink coverage levels in one
or more of the color or image planes that can alter the local
expansion or shrinkage of the print medium is dependent on
information content changes; the effectiveness of the method being
degraded if significant local regions of the print medium undergo
changes in the expansion or shrinkage of the print medium from one
version to another. Some aspects of the invention use a processor
is used to evaluate or compute an amount of version to version
differences between the corresponding documents of the different
copies. If the amount of difference is less than a predetermined
threshold amount, the local color plane correction values
determined during the printing of the initial versions are used to
enhance the color to color registration during the printing of the
later versions. If the identified difference between the versions
exceeds the predetermined threshold, the later versions are printed
without using the local color plane correction values of the
initial versions.
[0095] The predetermined thresholds can be a numerical measure of
difference in content, such as 5% or 10%, determined empirically or
set by a user for a particular print job. In another aspect of the
invention, only information in regions with high laydown of ink is
used to determine whether the threshold is exceeded.
[0096] A method for performing color-to-color correction for
printing multiple copies of a print job having one or more
documents, comprises printing a first copy of the print job using a
plurality of color planes, determining a first plurality of color
registration errors produced during the printing of the first copy
of the print job, for each document in the print job, using one or
more processors to: i) determine a global color plane correction
value for each color plane error produced during the printing of
the first copy of the print job based on the first plurality of
color registration errors; ii) determine a first plurality of local
color plane correction values for each color registration error
produced during the printing of the first copy of the print job,
wherein each of the first plurality of local color plane correction
values corresponds to one of the first plurality of color
registration errors; and iii) locally adjust the global color plane
correction value for each of the plurality of color planes based on
the first plurality of local color plane correction values; and
printing a second copy of the print job using the locally adjusted
global color plane correction values for each document in the print
job.
[0097] The method can further comprise storing the plurality of
locally adjusted color plane correction values in processor
accessible memory for printing subsequent copies of the print job;
determining a second plurality of color registration errors
produced during the printing of the second copy of the print job;
for each document in the second copy of the print job, using a
processor to determine a second plurality of local color plane
correction values for each second color registration error produced
during the printing of the second copy of the print job, wherein
each of the second plurality of local color plane correction values
corresponds to one of the second plurality of color registration
errors; using a processor to update each stored locally adjusted
global color plane correction value using the respective second
local color plane correction value associated with the printing of
the second copy of the print job; and printing a subsequent copy of
the print job using the updated locally adjusted global color plane
correction values for each document in the print job.
[0098] The method can further comprise storing the updated locally
adjusted global color plane correction values in processor
accessible memory for printing subsequent print jobs. Using a
processor to update each stored locally adjusted global color plane
correction value can further comprise periodically or
non-periodically updating each of the stored locally adjusted
global color plane correction values using the respective local
color plane correction values associated with the printing of two
or more subsequent copies of the print job or updating each of the
stored locally adjusted global color plane correction values after
each subsequent print job using the respective local color plane
correction values associated with the printing of the subsequent
copy of the print job.
[0099] Using a processor to update each stored locally adjusted
global color plane correction value can further comprise
determining an average of the local color plane correction values
associated with the first and second copies of the print job.
Periodically updating each of the stored locally adjusted global
color plane correction values can further comprise, for each
document in the print job and for each type of color plane
correction value, using a processor to determine an average of the
local color plane correction values using respective local color
plane correction values associated with a predetermined number of
subsequent copies of the print job.
[0100] Updating each of the stored locally adjusted global color
plane correction values can further comprise, for each document in
the print job and for each type of color plane correction value,
using a processor to compute a rolling average of the local color
plane correction values using the respective local color plane
correction values associated with the subsequent copies of the
print job.
[0101] The color registration errors can include at least one of
the following types: translation of the color planes, skew of the
color planes, rotation of the color planes, or magnification of the
color planes, or combinations thereof. A first plurality of color
registration errors produced during the printing of the first copy
of the print job is used to determine a plurality of color
registration errors for each of the at least one type of color
registration errors with respect to a reference color plane.
Determining a first plurality of registrations errors can further
include defining local segments for the documents in the print job
in the in-track or the cross-track direction, printing a plurality
of registration marks corresponding to the defined local segments
for each color plane, and using a processor to measure the
registration errors based on the corresponding each of the
plurality of registration marks for each color plane.
[0102] The plurality of registration marks can be printed in a
margin area of the print medium such that the printed registration
marks lay outside the printed document portion of the print job.
Defining local segments can comprise determining regions of high
ink laydown and low ink laydown and defining more local segments in
high ink laydown regions than in low ink laydown regions. Locally
adjusting the global color plane correction values can further
includes smoothing the local adjustments to provide smoothly
varying locally adjusted global color correction values.
[0103] A printing system for printing multiple copies of a print
job having one or more documents can comprise a plurality of
printheads adapted to print on a print medium, wherein each of the
plurality of printheads prints each of a plurality of color planes
of a first copy of the print job; one or more processors to:
[0104] i) determine a first plurality of color registration errors
produced during the printing of the first copy of the print
job;
[0105] ii) determine global color plane correction values for each
document of the first copy of the print job based on the first
plurality of color registration errors;
[0106] iii) determine a first plurality of local color plane
correction values for each color registration error produced during
the printing of the first copy of the print job, wherein each of
the first plurality of local color plane correction values
corresponds to one of the first plurality of color registration
errors; and
[0107] iv) locally adjust the global color plane correction values
for each document based on the first plurality of local color plane
correction values.
[0108] The plurality of printheads prints a second copy of the
print job using the locally adjusted global color plane correction
values for each document in the print job. The printing system can
further comprise a storage device to store the plurality of locally
adjusted global color plane correction values for printing
subsequent copies of the print job.
[0109] A processor can be used to determine a second plurality of
color registration errors produced during the printing of the
second copy of the print job, determine a second plurality of local
color plane correction values for each second color registration
error produced during the printing of the second copy of the print
job, wherein each of the second plurality of local color plane
correction values corresponds to one of the second plurality of
color registration errors, and update each stored locally adjusted
global color plane correction value using the respective second
local color plane correction value associated with the printing of
the second copy of the print job. The plurality of printheads
prints a subsequent copy of the print job using the updated locally
adjusted global color plane correction values for each document in
the print job.
[0110] The storage device stores the updated locally adjusted
global color plane correction values in processor accessible memory
for printing subsequent print jobs. A processor can periodically or
non-periodically update each of the stored locally adjusted global
color plane correction values using the respective local color
plane correction values associated with the printing of two or more
subsequent copies of the print job. A processor can update each of
the stored locally adjusted global color plane correction values
after each subsequent print job using the respective local color
plane correction values associated with the printing of the
subsequent copy of the print job. The stored locally adjusted
global color plane correction values can be updated using an
average of the local color plane correction values associated with
the first and second copies of the print job. The average of the
local color plane correction values can be computed using
respective local color plane correction values associated with a
predetermined number of subsequent copies of the print job. A
rolling average of the local color plane correction values using
the respective local color plane correction values associated with
the subsequent copies of the print job can also be computed.
[0111] The types of color registration errors can include
translation of the color planes, skew of the color planes, rotation
of color planes, or magnification of the color planes, or
combinations thereof. A processor can be used to determine a
plurality of color registration errors for each of the at least one
type of color registration errors with respect to a reference color
plane.
[0112] The plurality of printheads can print a plurality of
registration marks in a margin area of the print medium such that
the printed registration marks lie outside the printed document
portion of the print job.
[0113] A processor can be used to smooth the local adjustments to
the global color correction values to provide smoothly varying
locally adjusted global color correction values.
[0114] In another aspect of the invention, a method for performing
color-to-color correction for printing multiple copies of a print
job having one or more documents can comprise printing a first copy
of the print job using a plurality of color planes, determining a
first plurality of color registration errors produced during the
printing of the first copy of the print job, for each document in
the print job, using a processor to determine a first plurality of
local color plane correction values for each color registration
error produced during the printing of the first copy of the print
job, wherein each of the first plurality of local color plane
correction values corresponds to one of the first plurality of
color registration errors, and printing a second copy of the print
job using the local color plane correction values for each document
in the print job.
[0115] The method can include storing the plurality of local color
plane correction values in processor accessible memory for printing
subsequent print jobs. A second plurality of color registration
errors produced during the printing of the second copy of the print
job can be determined. For each document in the second copy of the
print job, the processor can be used to determine a second
plurality of local color plane correction values for each second
color registration error produced during the printing of the second
copy of the print job, wherein each of the second plurality of
local color plane correction values corresponds to one of the
second plurality of color registration errors. Each stored local
color plane correction value can be updated using the respective
second local color plane correction value associated with the
printing of the second copy of the print job. A subsequent copy of
the print job can be printed using the updated local color plane
correction values for each document in the print job. The updated
local color plane correction values can also be stored in processor
accessible memory for printing subsequent print jobs.
[0116] Updating each stored local color plane correction value can
comprise using the processor to periodically or non-periodically
update each of the stored local color plane correction values using
the respective local color plane correction values associated with
the printing of two or more subsequent copies of the print job.
Update each stored local color plane correction value can comprise
using the processor to update each of the stored local color plane
correction values after each subsequent print job using the
respective local color plane correction values associated with the
printing of the subsequent copy of the print job. Updating each
stored local color plane correction value can be performed by
determining an average of the local color plane correction values
associated with the first and second copies of the print job. The
processor can be used to periodically update each of the stored
local color plane correction values. For each document in the print
job and for each type of color plane correction value, an average
of the local color plane correction values is determined using
respective local color plane correction values associated with a
predetermined number of subsequent copies of the print job. In
another aspect of the invention, for each document in the print job
and for each type of color plane correction value, a rolling
average of the local color plane correction values is computed
using the respective local color plane correction values associated
with the subsequent copies of the print job.
[0117] In another aspect of the invention, a printing system for
printing multiple copies of a print job having one or more
documents can comprise a plurality of printheads adapted to print
on a print medium, wherein each of the plurality of printheads
prints each of a plurality of color planes of a first copy of the
print job, a processor to determine a first plurality of color
registration errors produced during the printing of the first copy
of the print job; and to determine a first plurality of local color
plane correction values for each document of the print job, wherein
each of the first plurality of local color plane correction values
corresponds to one of the first plurality of color registration
errors, and the plurality of printheads printing a second copy of
the print job using the local color plane correction values for
each document in the print job. A storage device can be used to
store the plurality of local color plane correction values for
printing subsequent copies of the print job.
[0118] The processor can be used to determine a second plurality of
color registration errors produced during the printing of the
second copy of the print job; determine a second plurality of local
color plane correction values for each second color registration
error produced during the printing of the second copy of the print
job, wherein each of the second plurality of local color plane
correction values corresponds to one of the second plurality of
color registration errors; and update each stored local color plane
correction value using the respective second local color plane
correction value associated with the printing of the second copy of
the print job. The plurality of printheads prints a subsequent copy
of the print job using the updated local color plane correction
values for each document in the print job. The storage device can
be used to store the updated local color plane correction values in
processor accessible memory for printing subsequent print jobs.
[0119] The processor can be used to periodically or
non-periodically update each of the stored local color plane
correction values using the respective local color plane correction
values associated with the printing of two or more subsequent
copies of the print job. The processor can update each of the
stored local color plane correction values after each subsequent
print job using the respective local color plane correction values
associated with the printing of the subsequent copy of the print
job. The stored local color plane correction values can be updated
using an average of the local color plane correction values
associated with the first and second copies of the print job. The
average of the local color plane correction values can be
determined using respective local color plane correction values
associated with a predetermined number of subsequent copies of the
print job. A rolling average of the local color plane correction
values can also be computed using the respective local color plane
correction values associated with the subsequent copies of the
print job.
[0120] In another aspect of the invention, a method for performing
color-to-color correction for printing multiple print jobs can
comprise receiving a first print job, wherein the first print job
has one or more documents, receiving a second print job, wherein at
least a portion of one of the documents in the second print job is
different from a corresponding document in the first print job, and
printing a copy of the first print job. One or more processors can
be used to:
[0121] i) determine a plurality of color plane registration errors
produced during the printing of the copy of the first print
job;
[0122] ii) to determine local color plane correction values based
on the plurality of color registration errors; and
[0123] iii) to compute a difference between the corresponding
documents in the first print job and second print job.
[0124] When the amount of difference is less than a predetermined
threshold, the local color plane correction values can be used to
print the second print job. The local color plane correction values
can be stored in processor accessible memory for printing
subsequent print jobs. When the difference is more than the
predetermined threshold, the method can further include determining
matching portions of the first and second print job, printing the
matching portions of the second print job using the local color
plane correction values for the corresponding portion of the first
print job, and printing the non-matching portions of the second
print job without using the local color plane correction values of
the first print job. The difference between the first and second
print job can be determined based on image content of the first and
second print job or using the high ink laydown regions of the first
and second print jobs.
[0125] A printing system for printing a second print job using
color plane correction values determined from printing a first
print job can comprise a plurality of printheads adapted to print
on a print medium, wherein each of the plurality of printheads
prints each of a plurality of color planes of a first print
job.
[0126] One or more processors can be used to:
[0127] i) determine a plurality of color plane registration errors
produced during the printing of the first print job;
[0128] ii) determine a plurality of local color plane correction
values for each color registration error produced during the
printing of the first print job, wherein each of the plurality of
local color plane correction values corresponds to one of the
plurality of color registration errors; and
[0129] iii) wherein at least a portion of one of the documents in
the second print job is different from a corresponding document in
the first print job, to compute a difference between the
corresponding documents in the first print job and second print
job.
[0130] When the difference is less than a predetermined threshold,
the plurality of printheads can print the second print job using
the local color plane correction values from the first print
job.
[0131] A processor accessible storage device can be used to store
the local color plane correction values for printing subsequent
print jobs. When the difference is more than the predetermined
threshold, a processor can be used to determine matching portions
of the first and second print job. The plurality of printheads
prints the matching portions of the second print job using the
local color plane correction values for the corresponding portion
of the first print job and the non-matching portions of the second
print job without using the local color plane correction values of
the first print job.
[0132] The invention has been described in detail with particular
reference to certain aspects thereof, but it will be understood
that variations and modifications can be effected within the spirit
and scope of the invention. And even though specific aspects of the
invention have been described herein, it should be noted that the
application is not limited to these aspects. In particular, any
features described with respect to one aspect of the invention may
also be used in other aspects, where compatible. And the features
of the different aspects of the invention may be exchanged, where
compatible.
PARTS LIST
[0133] 100 printing system [0134] 102 first tower [0135] 104 second
tower [0136] 106 linehead [0137] 108 dryer [0138] 110 quality
control sensor [0139] 112 print medium [0140] 114 transport
direction [0141] 116 turnover module [0142] 118 processor [0143]
120 storage device [0144] 200 printhead [0145] 202 nozzle array
[0146] 204 support structure [0147] 206 heat [0148] 300 print job
[0149] 302 page of document 1 [0150] 304 page of document 1 [0151]
306 page of document 2 [0152] 308 page of document 2 [0153] 310
page of document 3 [0154] 312 page of document 3 [0155] 314 page of
document N [0156] 316 page of document N [0157] 400 reference color
plane [0158] 402 color plane [0159] 404 in-track direction [0160]
406 cross-track direction [0161] 502 color plane [0162] 602 color
plane [0163] 700 plot of color registration errors in cross track
direction for first color for first tower [0164] 702 plot of color
registration errors in cross track direction for second color for
first tower [0165] 704 plot of color registration errors in cross
track direction for third color for first tower [0166] 800 plot of
color registration errors in in-track direction for first color for
first tower [0167] 802 plot of color registration errors in
in-track direction for second color for first tower [0168] 804 plot
of color registration errors in in-track direction for third color
for first tower [0169] 900 plot of color registration errors in
cross track direction for first color for second tower [0170] 902
plot of color registration errors in cross track direction for
second color for second tower [0171] 904 plot of color registration
errors in cross track direction for third color for second tower
[0172] 1000 plot of color registration errors in in-track direction
for first color for second tower [0173] 1002 plot of color
registration errors in in-track direction for second color for
second tower [0174] 1004 plot of color registration errors in
in-track direction for third color for second tower [0175] 1100
plot of color registration errors in cross track direction for
first color for first tower after global corrections [0176] 1102
plot of color registration errors in cross track direction for
second color for first tower after global corrections [0177] 1104
plot of color registration errors in cross track direction for
third color for first tower after global corrections [0178] 1106
points for starting documents in print job [0179] 1200 plot of
color registration errors in in-track direction for first color for
first tower after global corrections [0180] 1202 plot of color
registration errors in in-track direction for second color for
first tower after global corrections [0181] 1204 plot of color
registration errors in in-track direction for third color for first
tower after global corrections [0182] 1206 points for starting
documents in print job [0183] 1300 plot of color registration
errors in cross track direction for first color for second tower
after global corrections [0184] 1302 plot of color registration
errors in cross track direction for second color for second tower
after global corrections [0185] 1304 plot of color registration
errors in cross track direction for third color for second tower
after global corrections [0186] 1306 points for starting documents
in print job [0187] 1400 plot of color registration errors in
in-track direction for first color for second tower after global
corrections [0188] 1402 plot of color registration errors in
in-track direction for second color for second tower after global
corrections [0189] 1404 plot of color registration errors in
in-track direction for third color for second tower after global
corrections [0190] 1400 plot for first color [0191] 1402 plot for
second color [0192] 1404 plot for third color [0193] 1406 points
for starting documents in print job [0194] 1502 margin area [0195]
1504 registration mark [0196] 1506 registration element of first
color [0197] 1508 registration element of second color [0198] 1510
registration element of third color [0199] 1512 registration
element of fourth color [0200] 1602 plot of variability in local
color registration errors in cross track direction for one copy of
print job [0201] 1604 plot of variability in local color
registration errors in cross track direction for multiple copies of
print job [0202] 1702 plot of variability in local color
registration errors in in-track direction for one copy of print job
[0203] 1704 plot of variability in local color registration errors
in in-track direction for multiple copies of print job [0204] 1802
plot of variability in local color registration errors in cross
track direction for one copy of print job [0205] 1804 plot of
variability in local color registration errors in cross track
direction for multiple copies of print job [0206] 1902 plot of
variability in local color registration errors in cross track
direction for one copy of print job [0207] 1904 plot of variability
in local color registration errors in cross track direction for
multiple copies of print job [0208] 2004 registration mark outside
printed document area [0209] 2006 registration mark inside printing
document area [0210] 2100 Step of defining segments [0211] 2102
Step of printing first copy [0212] 2104 Step of determining global
color plane registration errors [0213] 2106 Step of determining
global color plane correction values [0214] 2108 Step of printing
using global color plane correction values [0215] 2110 Step of
determining local color plane registration errors [0216] 2112 Step
of determining locally adjusted global color plane correction
values [0217] 2114 Step of storing locally adjusted global color
plane correction values [0218] 2116 Step of printing subsequent
copies using locally adjusted global color plane correction values
[0219] 2118 Step of updating stored locally adjusted global color
plane correction values [0220] 2200 Step of defining local segments
in the in-track direction [0221] 2202 Step of defining local
segments in the in-track direction [0222] 2204 Step of printing a
plurality of registration marks [0223] 2206 Step of determining
color plane registration errors [0224] 2300 Step of receiving a
first print job [0225] 2302 Step of printing a first print job
[0226] 2304 Step of determining color registration errors [0227]
2306 Step of determining local color plane correction values [0228]
2308 Step receiving a second print job [0229] 2310 Step of
determining difference between first and second print job [0230]
2312 Step of determining if difference is less than threshold
[0231] 2314 Step of printing second print job [0232] 2316 Step of
determining matching portions of first and second print jobs [0233]
2318 Step of printing matching portions [0234] 2320 Step of
printing non-matching portions [0235] 2322 Step of storing local
color plane correction values
* * * * *