U.S. patent application number 12/145950 was filed with the patent office on 2008-12-25 for improved print control strip for color measurement on printing material, measuring method and method of metering ink.
This patent application is currently assigned to HEIDELBERGER DRUCKMASCHINEN AG. Invention is credited to Stefan Billmaier, Bernd Wenzel.
Application Number | 20080314268 12/145950 |
Document ID | / |
Family ID | 39854352 |
Filed Date | 2008-12-25 |
United States Patent
Application |
20080314268 |
Kind Code |
A1 |
Billmaier; Stefan ; et
al. |
December 25, 2008 |
Improved Print Control Strip for Color Measurement on Printing
Material, Measuring Method and Method of Metering Ink
Abstract
A print control strip to be applied to printing material during
a multicolor printing process, includes multiple measuring fields
associated with one ink zone on the printing material. The
measuring fields, which are associated with one ink zone, include
at least two gray measuring fields. A method of measuring fields in
print control strips on printing material with a measuring device
and a control unit connected thereto, and a method of controlling
metering of ink in offset printing presses including at least one
ink metering device in each printing unit and a control unit, are
also provided.
Inventors: |
Billmaier; Stefan;
(Walldorf, DE) ; Wenzel; Bernd; (Dielheim,
DE) |
Correspondence
Address: |
LERNER GREENBERG STEMER LLP
P O BOX 2480
HOLLYWOOD
FL
33022-2480
US
|
Assignee: |
HEIDELBERGER DRUCKMASCHINEN
AG
Heidelberg
DE
|
Family ID: |
39854352 |
Appl. No.: |
12/145950 |
Filed: |
June 25, 2008 |
Current U.S.
Class: |
101/211 ;
101/484 |
Current CPC
Class: |
B41F 33/0036 20130101;
B41F 33/0045 20130101; B41P 2233/51 20130101; G01J 3/52
20130101 |
Class at
Publication: |
101/211 ;
101/484 |
International
Class: |
B41M 1/14 20060101
B41M001/14; B41F 33/00 20060101 B41F033/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 25, 2007 |
DE |
10 2007 029 211.4 |
Claims
1. A print control strip to be applied during a multicolor printing
operation to printing material having ink zones, the print control
strip comprising: multiple measuring fields associated with an ink
zone on the printing material; said measuring fields associated
with one ink zone including at least two gray measuring fields.
2. The print control strip according to claim 1, wherein said
measuring fields associated with one ink zone include three gray
measuring fields.
3. The print control strip according to claim 2, wherein said gray
measuring fields represent a 25% continuous tone, 50% continuous
tone, and 75% continuous tone formed of three basic process colors
cyan, magenta and yellow.
4. The print control strip according to claim 1, which further
comprises at least one measuring field for spot colors.
5. The print control strip according to claim 1, wherein said
measuring fields are disposed in at least two parallel rows.
6. The print control strip according to claim 5, wherein each
measuring field in one row is present at least once in each other
row.
7. The print control strip according to claim 5, wherein said
measuring fields are disposed in different orders in said rows.
8. The print control strip according to claim 5, wherein said
measuring fields are provided only once in said rows.
9. A method of controlling metering of ink in offset printing
presses having printing units, at least one ink metering device in
each printing unit, and a control unit, the method comprising the
following steps: measuring a measuring strip including a plurality
of gray measuring fields within an ink zone on a printed product,
with a color measuring device; feeding measured gray values to the
control unit for controlling the metering of the ink in the
printing units; and calculating nominal values for controlling the
metering of the ink in the printing units with the control unit and
transmitting the nominal values to the printing units.
10. The method according to claim 9, which further comprises
influencing an evaluation of the gray measuring fields with the
control unit through an input device, prior to the step of
measuring the gray measuring fields with the color measuring
device.
11. The method according to claim 10, which further comprises
controlling the ink metering devices in the printing units of the
printing press with the control unit in dependence on selected gray
measuring fields.
12. The method according to claim 9, which further comprises
introducing the measured gray values as average values in the
control of the metering of the ink in the printing units, for ink
control by the control unit.
13. A method of measuring fields in print control strips on
printing material, the method comprising the following steps:
providing the measuring fields in at least two rows in the print
control strips; providing each measuring field at least once in
each row of the print control strips; measuring the measuring
fields with a measuring device to provide measured values; and
subjecting the measured values, during the measuring step, to a
plausibility check in a control unit connected to the measuring
device.
14. The method according to claim 13, which further comprises, upon
an occurrence of implausible measured values in one ink zone, using
measured values of a neighboring ink zone in the control unit for
controlling ink metering devices in printing units of a printing
press.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the priority, under 35 U.S.C. .sctn.
119, of German Patent Application DE 10 2007 029 211.4, filed Jun.
25, 2007; the prior application is herewith incorporated by
reference in its entirety.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] The present invention relates to a print control strip to be
applied to printing material during a multicolor printing
operation. The print control strip includes multiple measuring
fields which are associated with an ink zone on the printing
material. The present invention also relates to a method of
measuring the print control strip and to a method of controlling
the metering of ink in offset printing presses based on color
measurements on the print control strip.
[0003] The quality of a printing operation is measured by
evaluating to what extent the printed products conform to the
original. A high degree of conformity between the colors of the
printed product and the original is an important aspect of print
quality. The operator may evaluate the quality of the printed
products by visual inspection. In that case, the inspection is
subjective and depends on the person who makes the inspection. In
order to provide a more objective approach to quality control,
color measuring devices have been developed, which measure the
printed products in colorimetric or densitometric terms. In most
cases, however, it is not the entire printed image that is being
measured, because that would require a plurality of measuring
locations and would thus be a very time-consuming process. Instead,
it is common to use the color measuring devices to measure what are
known as print control strips. Those print control strips are
located outside the printed image in the lateral region of the
printing material. They may even be measured in the printing press
through the use of integrated color measuring devices because only
a limited number of color measurements need to be taken on the
print control strips, making precise measurements possible even at
the high printing speeds of approximately 18,000 sheets per hour,
which are common in modern offset printing presses. Such a print
control strip is known from German Published, Non-Prosecuted Patent
Application DE 36 43 721 A1, corresponding to U.S. Pat. No.
4,947,746. Such a print control strip for controlling the printing
process includes several color fields of different color and
structure disposed in a row and distributed in a manner
corresponding to the ink zones of the ink fountain in an offset
printing press. The printing colors that are used in the printing
process are in general included as solid-tone and halftone fields
in the print control strip. The print control strip described in
German Published, Non-Prosecuted Patent Application DE 36 43 721
A1, corresponding to U.S. Pat. No. 4,947,746, has alternating
solid-tone fields and continuous-tone fields for each color and
single-color screen fields for each color. The print control strip
described in German Published, Non-Prosecuted Patent Application DE
36 43 721 A1, corresponding to U.S. Pat. No. 4,947,746, includes a
gray measuring field on each border between two ink zones. However,
an optimum control of the color according to those few gray
measuring fields is impossible.
SUMMARY OF THE INVENTION
[0004] It is accordingly an object of the present invention to
provide a print control strip, a measuring method and a method of
metering ink, which overcome the hereinafore-mentioned
disadvantages of the heretofore-known devices and methods of this
general type and which provide improved ink control on the basis of
gray measuring fields.
[0005] With the foregoing and other objects in view there is
provided, in accordance with the invention, a print control strip
to be applied during a multicolor printing operation to printing
material having ink zones. The print control strip comprises
multiple measuring fields associated with an ink zone on the
printing material. The measuring fields associated with one ink
zone include at least two gray measuring fields.
[0006] With the objects of the invention in view, there is also
provided a method of controlling metering of ink in offset printing
presses having printing units, at least one ink metering device in
each printing unit, and a control unit. The method comprises
measuring a measuring strip including a plurality of gray measuring
fields within an ink zone on a printed product, with a color
measuring device, feeding measured gray values to the control unit
for controlling the metering of the ink in the printing units, and
calculating nominal values for controlling the metering of the ink
in the printing units with the control unit and transmitting the
nominal values to the printing units.
[0007] With the objects of the invention in view, there is
furthermore provided a method of measuring fields in print control
strips on printing material. The method comprises providing the
measuring fields in at least two rows in the print control strips,
providing each measuring field at least once in each row of the
print control strips, measuring the measuring fields with a
measuring device to provide measured values, and subjecting the
measured values, during the measuring step, to a plausibility check
in a control unit connected to the measuring device.
[0008] In accordance with the present invention, print control
strips which contain several measuring fields associated with an
ink zone on the printing material are printed onto the printing
material in the printing press. In order to improve the control
based on gray measuring fields, the measuring fields associated
with one ink zone include at least two gray measuring fields. Thus,
it is possible to obtain multiple measured gray values for each ink
zone, with each gray measuring field being composed of the colors
cyan, magenta, and yellow. Multiple gray levels can be determined
in each ink zone by providing several gray measuring fields per ink
zone. The gray values which have been measured in densitometric or
calorimetric terms by the color measuring device may then be fed to
the control unit of the printing press. The control unit may then
compare the measured gray values to measured color values of the
original. If there are unacceptable deviations, the control unit
may calculate a correcting variable to control the ink metering
device in the printing units of the printing press. If the printing
units include zonal ink metering devices, the present invention
provides multiple measured gray values for control purposes. This
increases the accuracy of the ink metering in the ink zones. In
addition to the gray measuring fields, the print control strip may
include the usual color measuring fields such as the solid tones of
cyan, magenta and yellow, as well as black and potential special or
spot colors. Furthermore, the individual colors may also be
available as halftone fields between zero and 100 percent.
[0009] In accordance with another particularly advantageous feature
of the invention, the measuring fields associated with one ink zone
may include three gray measuring fields. The more gray measuring
fields that are present, the more accurately the ink may be metered
in each ink zone. In particular, due to the provision of three gray
measuring fields in 25% continuous tone, 50% continuous tone, and
75% continuous tone for the three basic process colors cyan,
magenta and yellow, particularly accurate color measurement and ink
control are possible. Thus, it is possible to provide accurate ink
control even for highly complicated print jobs.
[0010] In accordance with a further feature of the invention, the
measuring fields may be disposed in at least two parallel rows. The
print control strips that have been known heretofore are formed of
one row of measuring fields, which are repeated to match the number
of ink zones. Due to the configuration of the color measuring
fields in two or more rows, the color measuring fields are
redundant in each ink zone. Thus, the operator receives more
information for the color measurement and ink control in each ink
zone. The redundant information in each ink zone also provides a
possibility to realize the presence of measuring errors resulting
from printing problems such as ghosting, hickeys, or the
accumulation of powder during the printing process in the printing
press. Thus, color measurement and ink control or metering become
more reliable.
[0011] In accordance with an added feature of the invention, each
measuring field of the first row is present at least once in each
of the other rows. In this case, the color measuring device
measures two measuring fields of the same type in each ink zone.
Thus, a twofold color measurement for each measuring field in each
ink zone is possible. The control unit of the printing press may
then evaluate the measured values which have been obtained in this
way in terms of plausibility. If the measured values of identical
measuring fields in one ink zone differ beyond an acceptable
tolerance, the assumption is that there are printing problems in
that particular ink zone which make the measured values
inconclusive. In this case, the control unit assumes that the
values are implausible, and the ink metering device for the
relevant ink zone may instead be controlled on the basis of the
measured values of an adjacent ink zone. The measured values of the
adjacent zones may at least be used to determine to what extent the
measured values in the ink zone which have been established as
erroneous need to be corrected.
[0012] In accordance with an additional feature of the invention,
which improves the conclusiveness of the measured values, the order
of the measuring fields in the rows is different. This avoids local
printing problems such as hickeys or powder accumulation in locally
limited specific areas on a measuring field affecting all measuring
fields of the same type in an ink zone. Due to the different order
of the measuring fields, measuring fields of the same type in one
ink zone are disposed at different locations, a fact which means
that printing problems which are locally limited do not cause all
measuring fields of the same type to be considered useless. Through
the use of the measured values for the adjacent measuring fields,
the control unit of the printing press may be able to decide which
of the measuring fields of the same type in the ink zone in
question most probably is the correct measuring field. In this
context, it is sufficient for measuring fields of the same type to
be present only once in each ink zone. Due to the configuration in
two or more rows, the redundancy required for reliable color
measurement is ensured without requiring the multiple-row print
control strip to have too many measuring fields per ink zone. Since
the width of the ink zone is given and invariable, an unnecessarily
high number of measuring fields per ink zone leads to
correspondingly small measuring fields which make an accurate color
measurement more difficult.
[0013] In accordance with yet another feature of the invention,
only one gray measuring field is present in each ink zone, but the
advantages of a print control strip which has two or more rows is
still exploited. In this case, the gray measurements will be less
accurate than if several gray measuring fields were present, but
the improvement of the reliability of the measurement due to the
redundancy of the measuring fields in the multi-row print control
strip is advantageous even if the multi-row print control strip
does not have more than one gray measuring field.
[0014] In accordance with a concomitant feature of the invention,
the evaluation of the gray measuring fields through the use of the
computer may be influenced through an input device before the
measurement of the gray measuring fields is taken through the use
of a color measuring device. If more gray measuring fields are
provided in each ink zone, the evaluation thereof may be adapted to
the specific conditions of the print job. Thus, knowing the
specific conditions of the print job, the operator may select gray
measuring fields in a job-specific way on the control unit of the
printing press through the use of a user interface and input
devices such as a keyboard, mouse, or touch screen. For example,
the operator may select to control the ink only based on the 25%
continuous tone or based on the 50% continuous tones and 75%
continuous tones of the gray measuring fields. If mostly 25%
continuous tones are present in a gray area in a printed image, the
best possible control result for the metering of the ink is
achieved if the individual ink zones are controlled on the basis of
the measured gray values of the 25% continuous-tone gray measuring
field. In this case the control suggestions for 50% continuous tone
and 75% continuous tone gray measuring fields should be suppressed.
Thus, measuring all gray measuring fields with the same weighting,
the control quality compared to a control based on average color
values would be considerably improved. However, the default
settings for the ink control in the computer may be that the
measured gray values are introduced in the control of the
ink-metering printing units as an average value. A job-specific ink
control based on the selected gray measuring fields is only
implemented when the operator expresses his or her wish to do so by
the appropriate inputs on the control computer through a suitable
input menu. This provides more options to the operator to adapt ink
control to the specific conditions of a print job without losing
the advantages of a default control based on averaging the measured
gray values.
[0015] Other features which are considered as characteristic for
the invention are set forth in the appended claims.
[0016] Although the invention is illustrated and described herein
as embodied in an improved print control strip for color
measurement on printing material, a measuring method and a method
of metering ink, it is nevertheless not intended to be limited to
the details shown, since various modifications and structural
changes may be made therein without departing from the spirit of
the invention and within the scope and range of equivalents of the
claims.
[0017] The construction and method of operation of the invention,
however, together with additional objects and advantages thereof
will be best understood from the following description of specific
embodiments when read in connection with the accompanying
drawings.
BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWING
[0018] FIG. 1 is a diagrammatic, partly perspective and partly
elevational view of a closed ink control loop formed of a color
measuring device, a control unit and an ink metering device in a
printing press;
[0019] FIG. 2 is a top-plan view of a double-row ink control strip
including multiple gray measuring fields in one ink zone; and
[0020] FIG. 3 is a top-plan view of a double-row ink control strip
with redundant measuring fields in one ink zone.
DETAILED DESCRIPTION OF THE INVENTION
[0021] Referring now to the figures of the drawings in detail and
first, particularly, to FIG. 1 thereof, there is seen an ink
control loop which includes a color measuring device 1, a control
unit 4 and an ink metering device in printing units 10 of a
printing press 7. The aforementioned devices 1, 4, 7 are connected
to each other through electronic communication lines. The color
measuring device 1 shown in FIG. 1 is a standalone color measuring
device which includes a measurement table 2 for receiving printed
products 3. Instead of such a standalone ink measuring device 1, an
inline ink measuring device, which is integrated into the printing
press 7, may be used to measure the printed products 3 in the
printing press 7, preferably at the outlet of the last printing
unit 10. The standalone ink measuring device 1 shown in FIG. 1
includes a measuring bar which is movable across the printed
product 3 in the longitudinal direction, and an ink measuring head
8 which is movable across the printed product 3 in the transverse
direction to measure each point on the printed product 3 in
colorimetric terms. As can be seen in FIG. 1, a print control strip
13 is present next to the printed image on the printed product 3.
This print control strip 13 is located in the lateral region of the
printed product 3. In order to shorten the measuring process, only
the measuring fields of the print control strip 13 need to be
scanned by the color measuring device 1. Measured values
established by the color measuring device 1 are then fed to the
control unit 4, which may be a standalone computer or an integral
part of a control unit of the printing press 7. The control unit 4
compares the measured color values to predetermined measured values
of the original. For this purpose, the original may have been
stored in the control unit 4 in digitized form, or the control unit
4 may be given the opportunity to access relevant data in a
prepress department. If the control unit 4 realizes deviations
beyond a certain tolerance between the data of the original and the
measured values, the established deviations are converted into
control values for the metering device in the printing units 10 of
the offset printing press 7. The control values which have been
calculated in this way are then transmitted to the printing press
7, where they are translated into corresponding modifications, for
example, of an ink zone opening in ink-zone inking units in the
printing units 10. In this way, the control loop between the color
measuring device 1 and the printing press 7 is closed. For display
and input purposes, the control unit 4 includes a screen 5 and
input devices such as a mouse 11 and a keyboard 6 for the operator
to influence the control loop of the ink metering device. Thus, the
operator may use the mouse 11 or keyboard 6 to select the way to
evaluate the print control strip 13 in the control unit 4. For
example, the operator may decide whether to evaluate all measuring
fields of the print control strip or to evaluate only specific
measuring fields which are relevant for the current print job.
[0022] FIGS. 2 and 3 illustrate an enlarged view of the print
control strip 13 provided on the printed product 3. What is shown
is a section of the lateral region of the printed product 3. The
print control strip 13 is shown in FIGS. 2 and 3 for one ink zone
9. This ink zone 9 repeats itself in a direction transversal to a
direction of transport BT of the printed product across the entire
width of the printed product 3. In the 102 sheet format, 32 ink
zones 9 are usually present adjacent each other in one row. There
may be gaps or additional measuring fields for register control,
for example, between the individual ink zones 9. Thus, the print
control strip 13 is not exclusively limited to color measurement,
but may be used for other control loops as well. The print control
strip 13 shown in FIG. 2 has several gray measuring fields CMY in
each ink zone 9. These gray measuring fields CMY are in different
tones. The gray measuring fields CMY in FIG. 2 are embodied as 25%
continuous tone, 50% continuous tone, and 75% continuous tone in
each ink zone 9. The gray measuring fields CMY are only present in
the upper row, which also includes the color black B and special or
spot colors X, Z, U, V. The lower row likewise includes the special
or spot colors X, Z, U, V and the color black B as well as the
colors cyan C, magenta M and yellow Y instead of the gray measuring
fields CMY. All of the measuring fields can be scanned by the color
measuring device 1, which can then transmit the measured values to
the control unit 4 for ink control purposes. The color values that
have been measured in this way will then be used to control the ink
metering devices in the printing units 10 of the offset printing
press 7.
[0023] The print control strip 13 shown in FIG. 3 likewise includes
two rows. Each measuring field present in one ink zone 9 is
provided twice. Thus, the color black B, the colors cyan C, magenta
M and yellow Y as well as the spot colors X, Z, U, V are present
both in the upper row and in the lower row of the print control
strip 13. Furthermore, the order of the measuring fields of one ink
zone 9 in the upper row and in the lower row is different so that
measuring fields of the same type are not directly above each
other. If a measuring field is not to be evaluated due to printing
problems, the redundant measuring field can be evaluated correctly
in the case of locally limited printing errors by carrying out a
plausibility check in the control unit 4 for the different color
values which have been measured for the same measuring field.
Measured values of neighboring ink zones 9 may be considered in the
plausibility check. Of course, it is possible to integrate the gray
measuring fields CMY which are known from FIG. 2 in the print
control strip of FIG. 3, for example by replacing the spot colors
X, Z, U, V by gray measuring fields CMY if no spot colors are being
used. However, if spot colors are used nevertheless, the number of
the measuring fields for one ink zone needs to be increased in a
corresponding way. This, however, would reduce the size of the
measuring fields due to the predetermined width of the ink zone 9.
Since the measuring fields in FIG. 3 are redundant due to the
two-row configuration, the reduction in size of the measuring
fields does not cause the same deteriorations as in the known
one-row structure of a print control strip 13. Moreover, in the
case of only slight deviations between measuring fields of the same
type in the top and lower row of the print control strip 13, the
measured values can be averaged in the control unit 4 and the
average value may be used to calculate the control values in the
ink metering devices of the printing units 10 of the offset
printing press. Thus, it is possible to avoid slight differences
caused, for example, by ghosting.
* * * * *