Note: Descriptions are shown in the official language in which they were submitted.
CA 02592528 2007-07-19
Description:
The invention provides a methodology for digitally displaying a representation
of a printed
sheet versus a digitally displayed soft proof.
Back Ground of the Invention:
Traditionally hard copy proofs and soft proofs that are intended to represent
the final
printed colour, are supplied locally at press side or remotely to print
buyers. These are
intended to provide a visual guide for the printing press operator. These
visual aids provide
guidance for manual press adjustments, designed to get a more accurate colour
match to
the supplied proofing media; be it hard copy or soft proof.
Historically once a print job is started, the press operator must maintain
control over the
colour accuracy through constant measurement of the colour bar elements using
some
form of colour measurement instrumentation. Additionally he will use visual
comparison
between the printed materials and the provided pre press colour proof media.
In assessing the visual colour differences between the printed materials and
the supplied
pre press proof colour media, the press operator must attempt to interpret the
colour
differences, reflective properties of the hard copy proof, what remedial
corrections to apply,
while ignoring the mitigating differences between the subtractive reflective
colour of the
printed copy and the additive transmissive colour if a soft proof is used.
The above scenario often results in the need to extend a press run or reprint
a job due to
colour variations at the start and throughout the press run. This results in
needless waste in
materials, time and additional expense to the press owner.
The proposed invention eliminates the currently required interpretation
between subtractive
colour and/or variation in additive colour media, thus providing faster and
more accurate
colour difference assessment.
Summary:
To overcome the disadvantages, the invention displays a colour correct primary
image
adjacent to a secondary image modified with colour spectrophotometric data
obtained by
measuring a color bar printed onto the press sheets obtained from the press.
The primary
image data for individual print jobs are stored as files and transferred over
a network
connection to the file storage of the invention. The image data file matching
a job to be
printed is identified by it's file name and manually selected by the press
operator. At this
time the image colour data is transferred from the file storage to the memory
of the
computer, and may undergo a series of initial modifications to more accurately
represent
the expected colour to be printed on the press. The primary image data is
displayed, and
duplicated in memory to serve as the baseline for the secondary image to be
modified
using spectral colour data from the press sheet.
During the press run, a colour bar scanning device is used to scan a plurality
of color
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CA 02592528 2007-07-19
patches printed onto a press sheet. These colour patches are arrayed in a line
oriented
perpendicular to the direction in which the sheets are delivered through the
press. The
color bar contains at least one solid patch for each ink, per ink key zone on
the press, and
may contain additional elements along its length of varying screen densities
for each ink.
The spectrophotometric data obtained from reading these elements are converted
to a
device independent colour space, such as CIELAB. The CIELAB color measurements
represent the colour of the inks printed in varying density by the press
printing units onto
the press sheet. The density of ink transferred to the printed sheet by the
plate on a press
printing unit is determined by the density of photopolymer emulsion per unit
area on the
plate, and the thickness of the ink film transferred to this emulsion. Each
inking unit is
divided into a plurality of ink key zones across the width of the inking unit.
An adjusting
servo for each ink key on a printing unit controls the amount of ink delivered
to the plate
under the corresponding ink key zone.
The colormetric data for each ink on each inking zone on the press is applied
to the
secondary image data, which is segmented into zones that match the ink zones
on the
press. The secondary image is displayed adjacent to the primary image. The act
of
scanning press sheet colour bars printed during the course of the press run,
permits the
invention to dynamically update the secondary image for comparison to the
ideal colour
corrected primary image.
In the drawings, which form a part of this specification;
Figure 1, is a schematic of the invention, including a press side computer
work station, a
soft proof display monitor, the scanning spectrophotometer, the press sheet,
and the
printing press.
Figure 2, is a schematic showing the press sheet and colour bar layout.
Figure 3, a detailed illustration of the soft proofer display.
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CA 02592528 2007-07-19
Detailed Description Of Preferred Embodiment:
Referring to Figure 1, which is a schematic of the invention, including a
press side
computer work station (101), an application software display monitor (Display
1) (102), the
soft proof display monitor (Display 2) (103), the primary image display area
(111), the
secondary image display area (112), the file storage location on hard drive
(108), line
memory location (114), the software for Process 1 (109), the software for
Process 2 (110),
the scanning spectrophotometer (104), the press sheet (105), the colour bar
location (113),
and the printing press (106); Figure 2, showing the press sheet and colour bar
layout; and
Figure 3, a detailed illustration of Display 2 (103).
The press side computer (101) automatically receives final imposition colour
data via a
network connection and allocates them to the storage location (108). The final
imposed file
can be in CIP/3 (.ppf), PDF, or other similar file formats.
Utilizing the Process 1 (109) User Interface which is located on Display 1
(102) the
operator initiates a New Job, and selects the appropriate file from the File
Storage Location
(108).
Process 1(109) transfers the file to Process 2(110).
Process 2 (110) transfers the file to Line Memory (114), separates the file
into colour
layers, applies a colour correction modification representative of the final
anticipated
printed image.
The modified colour corrected image is displayed on Display 2 (103) at
location (111).
The press operator initiates the press run using press (106).
A printed sheet (105) is retrieved from the press (106) and positioned into
the scanner
(104) with colour bar (113) properly oriented into the scanner (104).
The scan is initiated using Process 1(109) User Interface on Display 1 (102),
or manually
at the scanner (104).
The scanner (104) completes the scanning operation of each individual
measurement
element (116) comprising the colour bar (113), and transfer the
spectrophotometric data to
Process 1 (109).
Process 1(109) takes the data for the individual color bar elements (116) and
segments it
uniformly into a format that equates directly to the number of ink keys (117)
distributed
across the width of the press (106).
This operation is repeated for all of the printing units that were originally
designated in the
pre press file.
Process 1 (109) sends the data to Process 2 (110).
Process 2(110) loads a copy of the original pre press image file into line
memory. This file
is mathematically subdivided into segments that are representative of the ink
key widths.
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Process 2(110) applies the ink key zone spectrophotometric data to the
mathematically
subdivided segments.
Process 2 (110) subsequently displays the modified image on Display 2 (103) at
location
(112).
The resulting dual display (111, 112) allows the operator to objectively view
the anticipated
printed colour results (111) to a representation of what is actually being
printed (112),
without being hindered by the dissimilar media found in traditional proofing
methods,
whether they are printed hard copy or LCD displayed soft copy proofs.
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