U.S. patent application number 11/254982 was filed with the patent office on 2007-04-26 for method and system for detecting defects during the fabrication of a printing cylinder.
This patent application is currently assigned to Elbit Vision Systems Ltd.. Invention is credited to Omri Govrin, Tsafrir Grinberg, Gadi Harpaz, Yoram Hasidi, Arkadi Machtei.
Application Number | 20070089625 11/254982 |
Document ID | / |
Family ID | 37895873 |
Filed Date | 2007-04-26 |
United States Patent
Application |
20070089625 |
Kind Code |
A1 |
Grinberg; Tsafrir ; et
al. |
April 26, 2007 |
Method and system for detecting defects during the fabrication of a
printing cylinder
Abstract
The invention relates generally to the field of printing. More
specifically, the invention relates to a method and system for
automatically detecting defects in a printing cylinder during its
fabrication process. The invention further relates to a process for
fabricating a printing cylinder.
Inventors: |
Grinberg; Tsafrir; (Ramat
Hasharon, IL) ; Harpaz; Gadi; (Hod Hasharon, IL)
; Govrin; Omri; (Eshar, IL) ; Hasidi; Yoram;
(Beit Arieh, IL) ; Machtei; Arkadi; (Kfar Saba,
IL) |
Correspondence
Address: |
Eitan Law Group;C/O LandonIP Inc.
1700 Diagonal Road
Suite 450
Alexandria
VA
22314
US
|
Assignee: |
Elbit Vision Systems Ltd.
Yoqneam
IL
|
Family ID: |
37895873 |
Appl. No.: |
11/254982 |
Filed: |
October 20, 2005 |
Current U.S.
Class: |
101/484 |
Current CPC
Class: |
B41F 33/0027 20130101;
B41F 13/10 20130101 |
Class at
Publication: |
101/484 |
International
Class: |
B41F 33/00 20060101
B41F033/00 |
Claims
1. A method for detecting defects on an engravable material, the
material being the peripheral surface of a printing cylinder, the
method comprises: acquiring an image of an engravable material,
wherein said material is the peripheral surface of a printing
cylinder; and performing a morphological analysis of said image
thereby detecting defects on said engravable material.
2. The method according to claim 1, wherein said engravable
material comprises a metal.
3. The method according to claim 2, wherein said metal comprises
copper, aluminum, zinc or a combination thereof.
4. The method according to claim 1, wherein said engravable
material comprises a polymer.
5. The method according to claim 4, wherein said polymer comprises
rubber.
6. The method according to claim 2, wherein said material is
processed to increase the level of smoothness.
7. The method according to claim 1, wherein said engravable
material comprises a plurality of cells engraved on said engravable
material according to a predetermined patterning scheme and wherein
the image of said engravable material comprises the image of said
cells.
8. The method according to claim 1, wherein said engravable
material further comprising a wear-proof layer.
9. The method according to claim 8, wherein said wear-proof layer
comprises metal.
10. The method according to claim 1, wherein said engravable
material comprises a pattern-generating layer.
11. The method according to claim 1, wherein said engravable
material comprises a transfer layer.
12. The method according to claim 7, wherein the step of performing
said morphological analysis comprises use of a predefined set of
characteristics to identify defective cells and the position
thereof.
13. The method according to claim 12, wherein said predefined set
of characteristics comprises: pattern regularity, dimensions of
cells, shape of cells, cross-sectional area of cells, bridges
between adjacent cells, distance between adjacent cells, depth of
cells or any combination thereof.
14. The method according to claim 7, wherein the step of performing
the morphological analysis comprises the step of comparing said
image to a reference image, wherein said reference image is
obtained from said patterning scheme.
15. The method according to claim 10, wherein the step of
performing said morphological analysis comprises the step of
detecting defects related to non-uniformity of the thickness and/or
surface of said pattern-generating layer.
16. Use of the method according to claim 1 in a process for
fabricating a printing cylinder.
17. A system for detecting defects on an engravable material, the
material being the peripheral surface of a printing cylinder, the
system comprises: a moveable image acquiring apparatus for
outputting, at different stages of the fabrication process, data
related to an image of an engravable material, wherein said
material is the peripheral surface of a printing cylinder, the
apparatus is capable of moving forwards and backwards along an
imaginary line that is essentially parallel to the rotation axis of
said cylinder; a controllable mechanism, for rotating said cylinder
and operating the image acquiring apparatus; and a controller,
functionally coupled to said controllable mechanism for causing it
to rotate the cylinder and move said image acquiring apparatus in
synchronization, wherein said controller is configured to receive
the data related to said image and to output data related to the
detection of defects on said engravable material.
18. The system according to claim 17, wherein said engravable
material comprises a metal.
19. The system according to claim 19, wherein said metal comprises
copper, aluminum, zinc or a combination thereof.
20. The system according to claim 17, wherein said engravable
material comprises a polymer.
21. The system according to claim 20, wherein said polymer
comprises rubber.
22. The system according to claim 18, wherein said material is
processed to increase the level of smoothness.
23. The system according to claim 17, wherein said engravable
material comprises a plurality of cells engraved on said material
according to a predetermined patterning scheme and wherein the
image of said engravable material comprises the image of said
cells.
24. The system according to claim 17, wherein said engravable
material further comprising a wear-proof layer.
25. The system according to claim 24, wherein said wear-proof layer
comprises a metal.
26. The system according to claim 17, wherein said engravable
material comprises a pattern-generating layer.
27. The system according to claim 17, wherein said engravable
material comprises a transfer layer.
28. The system according to claim 23, wherein said controller uses
a predefined set of characteristics to identify defective cells and
the position thereof.
29. The system according to claim 28, wherein said predefined set
of characteristics comprises: pattern regularity, dimensions of
cells, shape of cells, cross-sectional area of cells, bridges
between adjacent cells, distance between adjacent cells, depth of
cells or any combination thereof.
30. The system according to claim 23, wherein said controller is
configured to locate the position of the defective cells on said
engravable material by comparing data representative of said image
of said engravable material to data representative of a reference
image, wherein said reference image is obtained from said
patterning scheme.
31. The system according to claim 26, wherein said controller is
configured to detect defects related to non-uniformity of the
thickness and/or surface of said pattern-generating layer.
32. The system according to claim 17, further comprising a GUI to
display a picture of said defects.
33. The system according to claim 32, wherein said GUI further
provides processed data related to said defects.
34. The system according to claim 33, wherein said processed data
related to said defects comprises a list of said defects, size of
said defects, distribution of said sizes of said defects, shapes of
said defects, the influence of said defects on the quality of the
printing picture or any combination thereof.
35. A printing cylinder fabrication process designed to enable the
detection of defects on an engravable material, the material being
the peripheral surface of a printing cylinder, the process
comprises: acquiring an image of an engravable material, wherein
said material is the peripheral surface of a printing cylinder; and
performing a morphological analysis of said image thereby detecting
defects on said engravable material.
36. The process according to claim 35, wherein said engravable
material comprises a metal.
37. The process according to claim 36, wherein said metal comprises
copper, aluminum, zinc or a combination thereof.
38. The process according to claim 35, wherein said engravable
material comprises a polymer.
39. The process according to claim 38, wherein said polymer
comprises rubber.
40. The process according to claim 36, wherein said material is
processed to increase the level of smoothness.
41. The process according to claim 35, wherein said engravable
material comprises a plurality of cells engraved on said material
according to a predetermined patterning scheme and wherein the
image of said engravable material comprises the image of said
cells.
42. The process according to claim 35, wherein said engravable
material further comprising a wear-proof layer.
43. The process according to claim 42, wherein said wear-proof
layer comprises a metal.
44. The process according to claim 35, wherein said engravable
material comprises a pattern-generating layer.
45. The process according to claim 35, wherein said engravable
material comprises a transfer layer.
46. The process according to claim 41, wherein the step of
performing said morphological analysis comprises use of a
predefined set of characteristics to identify defective cells and
the position thereof.
47. The process according to claim 46, wherein said predefined set
of characteristics comprises: pattern regularity, dimensions of
cells, shape of cells, cross-sectional area of cells, bridges
between adjacent cells, distance between adjacent cells, depth of
cells or any combination thereof.
48. The process according to claim 41, wherein the step of
performing said morphological analysis comprises the step of
comparing said image to a reference image, wherein said reference
image is obtained from said patterning scheme, thereby locating the
position of defective cells on said engravable material.
49. The process according to claim 44, wherein the step of
performing the morphological analysis comprises the step detecting
defects related to non-uniformity of the thickness and/or surface
of said pattern-generating layer.
Description
FIELD OF THE INVENTION
[0001] The invention generally relates to the field of printing.
More specifically, the invention relates to a method and system for
automatically detecting defects in a printing cylinder during its
fabrication process. The invention further relates to a process for
fabricating a printing cylinder.
BACKGROUND
[0002] Several printing techniques are widely used in the printing
industry, among which is a printing technique known in the printing
field as "Gravure press" and "rotogravure printing".
[0003] Typically, the manufacturing of a gravure printing cylinder
involves coating a cylindrical metal base (e.g., steel) with an
`image carrier` (e.g., copper); polishing the surface of the image
carrier; engraving (such as by etching) the image on the image
carrier; coating the image carrier with wear-proof layer (e.g.,
Chrome plating) to increase the print durability of the printing
cylinder; and polishing the wear-proof layer.
[0004] During printing, the printing cylinder is immersed in a bath
of fluid ink and as it rotates in the bath, ink fills the tiny
cells and covers the surface of the cylinder. At a certain point,
while the cylinder keeps on turning, the excess ink is wiped off
the cylinder by a flexible steel doctor blade which leaves the
non-image area clean while the ink remains in the recessed cells.
The ink remaining in the recessed cells forms the image by direct
transfer to the substrate (paper or other material) as it passes
between the plate cylinder and the impression cylinder. The ink is
drawn out of the cells onto the substrate by capillary action at
the point of contact. In many cases, gravure printing is done using
engraved copper cylinders protected from wear by the application of
a thin electroplate of chromium. Gravure printing generally
consists of a printing cylinder, a rubber covered impression roll,
an ink fountain, a doctor blade, and a means of drying the ink. The
major unit operations in a gravure printing operation are (i) Image
preparation; (ii) Cylinder preparation; (iii) Printing, and (iv)
Finishing.
[0005] Gravure press offers an outstanding print quality, output
consistency, high versatility and printing speed. Gravure press
also allows producing excellent and constant reproductions
throughout each print run. Gravure press is a relatively simple
printing process that can produce millions of high quality copies
at high speed. Nevertheless, defects may occur at any fabrication
step of the printing cylinder, and thus, it would be advantageous
to visually inspect the printing cylinder throughout its
fabrication process. In order to significantly reduce costs
involved in the fabrication of defective printing cylinders, the
printing cylinders -require a careful scrutiny throughout their
fabrication process. In cases where defects are minor or located in
non-critical positions (i.e., depending on the patterning scheme),
the printing cylinder may be used after removing, or fixing, the
defects, or with the defects. In cases of major or critically
located defects, it may be decided that the printing cylinder will
not be used.
SUMMARY OF THE INVENTION
[0006] In one embodiment, the invention provides a method for
detecting defects on an engravable material, the material being the
peripheral surface of a printing cylinder, the method may include,
inter alia, acquiring an image of an engravable material, wherein
the engravable material is the peripheral surface of a printing
cylinder; and performing a morphological analysis of the image
thereby detecting defects on the engravable material.
[0007] In another embodiment, the invention provides a use of the
method according to the invention in the fabrication process of a
printing cylinder.
[0008] The invention further provides, according to another
embodiment, a system for detecting defects on an engravable
material, the material being the peripheral surface of a printing
cylinder, the system may include, inter alia, a moveable image
acquiring apparatus for outputting, at different stages of the
fabrication process, data related to an image of an engravable
material, the apparatus is capable of moving forwards and backwards
along an imaginary line that is essentially parallel to the
rotation axis of the cylinder, a controllable mechanism, for
rotating the cylinder and operating the image acquiring apparatus,
and a controller, functionally coupled to the controllable
mechanism, for causing the controllable mechanism to rotate the
cylinder and move the image acquiring apparatus in synchronization,
wherein the controller is configured to receive the data related to
the image and to output data related to defects detected on the
engravable material.
[0009] The invention further provides, according to another
embodiment, a printing cylinder fabrication process designed to
enable detection of defects associated with various steps of the
fabrication process, the process may include, inter alia, acquiring
an image of the periphery of the printing cylinder after each
fabrication step and performing a morphological analysis of each
image, thereby detecting defects on the engravable material.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The subject matter regarded as the disclosure is
particularly pointed out and distinctly claimed in the concluding
portion of the specification. The disclosure, however, both as to
organization and method of operation, together with objects,
features, and advantages thereof, may best be understood by
reference to the following detailed description when read with the
accompanying drawings in which:
[0011] FIG. 1 (prior art) shows different types of cells;
[0012] FIG. 2 (prior art) shows different shapes of cells;
[0013] FIG. 3 shows exemplary pinholes-like defects between
cells;
[0014] FIG. 4 shows an exemplary scratch-like defect traversing
several cells;
[0015] FIG. 5 schematically illustrates the defects detection
system in accordance with some embodiments of the present
invention;
[0016] FIG. 6 shows a group of cells and good and poor quality
walls therebetween, the poor quality walls being surrounded by an
ellipse-shaped line (for illustration purpose only);
[0017] FIG. 7 shows a processed image of the acquired image of FIG.
6, which was obtained by employing morphology analysis on the image
in accordance with some embodiments of the invention;
[0018] FIG. 8 shows an exemplary group of cells that corresponds to
the digit `4` (on the left-hand side of the display screen) and a
processed image thereof (on the right-hand side of the display
screen), according to embodiments of the invention;
[0019] FIG. 9 shows an exemplary defect in a group of cells,
according to embodiments of the invention;
[0020] FIG. 10 shows a processed image of the image of FIG. 9, in
accordance with some embodiments of the invention; and
[0021] FIG. 11 shows an exemplary graphical user interface ("GUI")
in accordance with some embodiments of the invention.
[0022] It will be appreciated that for simplicity and clarity of
illustration, elements shown in the figures have not necessarily
been drawn to scale. For example, the dimensions of some of the
elements may be exaggerated relative to other elements for clarity.
Further, where considered appropriate, reference numerals may be
repeated among the figures to indicate corresponding or analogous
elements.
DETAILED DESCRIPTION
[0023] In the following detailed description, numerous specific
details are set forth in order to provide a thorough understanding
of the disclosure. However, it will be understood by those skilled
in the art that the invention may be practiced without these
specific details. In other instances, well-known methods,
procedures, components and circuits have not been described in
detail so as not to obscure the invention.
[0024] Unless specifically stated otherwise, as apparent from the
following discussions, it is appreciated that throughout the
specification discussions utilizing terms such as "processing",
"computing", "calculating", "determining", or the like, refer to
the action and/or processes of a computer or computing system, or
similar electronic computing device, that manipulate and/or
transform data represented as physical, such as electronic,
quantities within the computing system's registers and/or memories
into other data similarly represented as physical quantities within
the computing system's memories, registers or other such
information storage, transmission or display devices.
[0025] The disclosure may take the form of an entirely hardware
embodiment, an entirely software embodiment or an embodiment
containing both hardware and software elements. In a preferred
embodiment, the disclosure is implemented in software, which
includes but is not limited to firmware, resident software,
microcode, etc.
[0026] Embodiments of the invention may include apparatuses for
performing the operations described herein. This apparatus may be
specially constructed for the desired purposes, or it may include a
general purpose computer selectively activated or reconfigured by a
computer program stored in the computer.
[0027] Furthermore, the disclosure may take the form of a computer
program product accessible from a computer-usable or
computer-readable medium providing program code for use by or in
connection with a computer or any instruction execution system. For
the purposes of this description, a computer-usable or computer
readable medium can be any apparatus that can contain, store,
communicate, propagate, or transport the program for use by or in
connection with the instruction execution system, apparatus, or
device.
[0028] The medium may be an electronic, magnetic, optical,
electromagnetic, infrared, or semiconductor system (or apparatus or
device) or a propagation medium. Examples of a computer-readable
medium include a semiconductor or solid state memory, magnetic
tape, magnetic-optical disks, a removable computer diskette, a
random access memory (RAM), a read-only memory (ROM), a rigid
magnetic disk, an optical disk, electrically programmable read-only
memories (EPROMs), electrically erasable and programmable read only
memories (EEPROMs), magnetic or optical cards, or any other type of
media suitable for storing electronic instructions, and capable of
being coupled to a computer system bus. Current examples of optical
disks include compact disk--read only memory (CD-ROM), compact
disk--read/write (CD-R/W) and DVD.
[0029] A data processing system suitable for storing and/or
executing program code may include at least one processor coupled
directly or indirectly to memory elements through a system bus. The
memory elements may include local memory employed during actual
execution of the program code, bulk storage, and cache memories
which provide temporary storage of at least some program code in
order to reduce the number of times code has to be retrieved from
bulk storage during execution.
[0030] Input/output or I/O devices (including but not limited to
keyboards, displays, pointing devices, etc.) can be coupled to the
system either directly or through intervening I/O controllers.
[0031] Network adapters may also be coupled to the system to enable
the data processing system to become coupled to other data
processing systems or remote printers or storage devices through
intervening private or public networks. Modems, cable modem and
Ethernet cards are just a few of the currently available types of
network adapters.
[0032] The processes and displays presented herein are not
inherently related to any particular computer or other apparatus.
Various general purpose systems may be used with programs in
accordance with the teachings herein, or it may prove convenient to
construct a more specialized apparatus to perform the desired
method. The desired structure for a variety of these systems will
appear from the description below. In addition, embodiments of the
invention are not described with reference to any particular
programming language. It will be appreciated that a variety of
programming languages may be used to implement the teachings of the
disclosures as described herein.
[0033] In one embodiment, the invention provides a method for
detecting defects on an engravable material, the material being the
peripheral surface of a printing cylinder, the method may include,
inter alia, acquiring an image of an engravable material, wherein
the material is the peripheral surface of a printing cylinder and
performing a morphological analysis of the image thereby detecting
defects on the engravable material.
[0034] In one embodiment of the invention, the term "engravable
material" may refer to an "image carrier". In another embodiment
the term "engravable material" may refer to an "engravable
coating". In another embodiment, the term "image carrier" may refer
to any substance upon which cells are, or may be, located. In
another embodiment, the cells are designed to be filled with
ink.
[0035] In one embodiment of the invention, the term "defect" may
refer to an imperfect cell. In another embodiment, the term
"defect" may refer to an imperfect wall between cells. In another
embodiment, the term "defect" may refer to any form, shape or
change in the inspected surface that is not related to a known
patterning scheme. In another embodiment, the term "defect" may
refer to any imperfection in the inspected surface. In another
embodiment, the term "defect" may refer to an artifact suspected to
be a defect.
[0036] In one embodiment of the invention, the term "patterning
scheme" may refer to a printing scheme. In another embodiment, the
term "patterning scheme" may refer to a coating scheme. In another
embodiment, the term "patterning scheme" may refer to an
ink-layering scheme.
[0037] In one embodiment of the invention, the engravable material
may include, inter alia, a metal. In another embodiment, the metal
may include, inter alia, copper, aluminum, zinc or a combination
thereof. In another embodiment, the material may be processed to
increase the level of smoothness. In another embodiment, the
material may be finished to form a high quality surface. In another
embodiment, the material may be polished. In one embodiment of the
invention, the engravable material may further include, inter alia,
a polymer. In another embodiment, the polymer may further include,
inter alia, rubber.
[0038] In one embodiment of the invention, the engravable material
may include, inter alia, a plurality of cells engraved on the
material according to a predetermined patterning scheme. In another
embodiment, the cells are engraved into the material using
mechanical, electromechanical or laser techniques, or any
combination thereof. In another embodiment, the cells are engraved
into the material by means of etching into the material using a
pattern-generating layer, or transfer layer. In one embodiment of
the invention, the terms `pattern-generating layer` and `transfer
layer` may both refer to a processable layer of substance that is
applied to a surface of an object for creating in the layer a
latent graphical image of interest, or a 'negative, or
complimentary, image thereof. Once processed, for example by being
exposed to a source of energy, the graphical image of interest is
rendered visible on the surface of the object. Photo resist,
lacquer and "black varnish" are exemplary materials useable as
transfer layer. In one embodiment of the invention, the term
"image" may refer to a digital image.
[0039] In one embodiment of the invention, the engravable material
may include, inter alia, a wear-proof layer. In another embodiment,
the wear-proof layer may include, inter alia, a metal. In another
embodiment, the metal may include, inter alia, chromium or any
other appropriate substance that may be used to form a wear-proof
layer.
[0040] In one embodiment of the invention, the engravable material
may include, inter alia, a pattern-generating layer. In another
embodiment, the pattern-generating layer may include, inter alia, a
photoresist layer. In another embodiment, the engravable material
may include, inter alia, a transfer layer.
[0041] According to some embodiments of the invention, detecting
defects in respect of the plurality of cells may include, inter
alia, analyzing the pattern of the cells by, e.g., comparing the
actual pattern of the cells to a known, or expected, pattern. The
expected, or known, pattern of cells may be known from the
patterning scheme, which defines the characteristics and pattern of
cells based on the intended printing results.
[0042] In one embodiment of the invention, the step of performing
the morphological analysis may include use of a predefined set of
characteristics, or characteristics, to identify defective cells
and the position thereof. In another embodiment, the predefined set
of characteristics may include: pattern regularity, dimensions of
cells, shape of cells, cross-sectional area of cells, bridges
between adjacent cells, distance between adjacent cells, depth of
cells or any combination thereof. In another embodiment, the step
of performing the morphological analysis may include the step of
comparing the image to a reference image, wherein the reference
image is obtained from the patterning scheme, thereby locating the
position of defective cells on the engravable material. In another
embodiment, the step of performing the morphological analysis may
include the step detecting defects on the surface of the metal. In
another embodiment, the step of performing the morphological
analysis may include the step detecting defects related to
non-uniformity of the thickness and/or surface of the
pattern-generating layer.
[0043] According to one embodiment of the invention, a first image
of the peripheral surface of the image carrier may be acquired
after polishing the image carrier, to detect defects such as
scratches. According to another embodiment, a second image may also
be acquired, of the surface of the image carrier after a plurality
of cells are engraved into the material according to a patterning
scheme of interest. According to another embodiment, a morphology
analysis may be performed by a software-driven application, in
respect of the acquired first and second images, to detect defects
in the peripheral surface and in the plurality of cells,
respectively. According to another embodiment, digital signal
processing tools may be utilized for this purpose.
[0044] A cylinder fabrication process may include a step of coating
the plurality of cells and `bridges` therebetween with a wear-proof
layer, such as chromium. According to one embodiment, the method of
the invention may further include acquiring a third image of the
wear-proof layer and detecting defects in respect of the wear-proof
layer by analyzing the third image.
[0045] The cells may be engraved into the material by being etched
into the material while using a layer of photoresist substance for
this purpose, or any other appropriate pattern-generating
substance. In the latter case, according to embodiments of the
invention, the method may further include acquiring a forth image
of the photoresist layer and detecting defects in respect of the
thickness non-uniformity and surface unity of the layer by
analyzing the forth image.
[0046] According to some embodiments of the invention, detecting
defects in respect of the plurality of cells may include use of a
predefined set of characteristics to identify imperfect cells, and
indication of the positions of the imperfect cells on the material.
The predefined set of characteristics may refer; e.g., to pattern
regularity; desired dimensions of cells; desired shape of cells;
desired cross-sectional area of cells; `bridges` between adjacent
cells; desired distance between adjacent cells and desired depth of
cells.
[0047] According to other embodiments of the invention, detecting
defective cells may include comparing data derived from the second
image to a reference image data that is derived from the patterning
scheme.
[0048] According to other embodiments of the invention, detecting
defects in respect of the plurality of cells may include both use
of a predefined set of characteristics to identify imperfect cells
and verifying suspected defective cells by comparing data that is
derived from the second image to a reference image data that is
derived from the patterning scheme.
[0049] The invention also provides, in accordance with some
embodiments, a process for fabricating a printing cylinder that
utilizes the defects detection method described herein.
[0050] In one embodiment, the invention provides a printing
cylinder fabrication process designed to enable the detection of
defects on an engravable material, the material being the
peripheral surface of a printing cylinder, the process may include,
inter alia, acquiring an image of an engravable material, wherein
the material is the peripheral surface of a printing cylinder and
performing a morphological analysis of the image thereby detecting
defects on the engravable material.
[0051] In one embodiment of the invention, the engravable material
may include, inter alia, a metal. In another embodiment, the metal
may include, inter alia, copper, aluminum, zinc or a combination
thereof. In another embodiment, the material may be processed to
increase the level of smoothness. In another embodiment, the
material may be polished. In one embodiment of the invention, the
engravable material may further include, inter alia, a polymer. In
another embodiment, the polymer may further include, inter alia,
rubber.
[0052] In one embodiment of the invention, the engravable material
may include, inter alia, a plurality of cells engraved on the
material according to a predetermined patterning scheme. In another
embodiment, the cells are engraved into the material using
mechanical, electromechanical or laser techniques, or any
combination thereof. In another embodiment, the cells are engraved
into the material by means of etching into the material using a
pattern-generating layer.
[0053] In one embodiment of the invention, the engravable material
may include, inter alia, a wear-proof layer. In another embodiment,
the wear-proof layer may include, inter alia, a metal. In another
embodiment, the metal may include, inter alia, chromium or any
other appropriate substance that may be used to form a wear-proof
layer. In one embodiment of the invention, the engravable material
may include, inter alia, pattern-generating layer. In another
embodiment, the pattern-generating layer may include, inter alia, a
photoresist layer. In another embodiment, the engravable material
may include, inter alia, a transfer layer.
[0054] According to some embodiments of the invention, detecting
defects in respect of the plurality of cells may include, inter
alia, analyzing the pattern of the cells by, e.g., comparing the
pattern to a known, or expected, pattern. The expected, or known,
pattern of cells may be known from the patterning scheme, which
defines the characteristics and pattern of cells based on the
intended printing results.
[0055] In one embodiment of the invention, the step of performing
the morphological analysis may include a use of a predefined set of
characteristics to identify defective cells and the position
thereof. In another embodiment, the predefined set of
characteristics may include, inter alia, pattern regularity,
dimensions of cells, shape of cells, cross-sectional area of cells,
bridges between adjacent cells, distance between adjacent cells,
depth of cells or any combination thereof. In another embodiment,
the step of performing the morphological analysis may include,
inter alia, the step of comparing the image to a reference image,
wherein the reference image is obtained from the patterning scheme,
thereby locating the position of defective cells on the engravable
material. In another embodiment, the step of performing the
morphological analysis may include, inter alia, the step detecting
defects on the surface of the metal. In another embodiment, the
step of performing the morphological analysis may include, inter
alia, the step detecting defects related to non-uniformity of the
thickness and/or surface of the pattern-generating layer.
[0056] In one embodiment of the invention, the process according to
the invention may further include, inter alia, the step of coating
the engravable material on the peripheral surface of the printing
cylinder prior to the step of acquiring the image.
[0057] In one embodiment of the invention, the process according to
the invention, may further include, inter alia, the step of
engraving into the engravable material a plurality of cells
according to a predefined patterning scheme.
[0058] In one embodiment, the invention provides a cylinder
fabrication process, the process is designed to enable the
detection of defects on an engravable material, the material being
the peripheral surface of a printing cylinder, the process may
include, inter alia, coating the engravable material on the
peripheral surface of the printing cylinder, polishing the material
and acquiring a first image thereof, analyzing the first image to
detect defects in the polished material, engraving into the
polished material a plurality of cells according to a patterning
scheme of interest and acquiring a second image of the plurality of
cells, and analyzing the second image to detect defects in the
plurality of cells. In another embodiment the fabrication process
may further include, inter alia, coating the image carrier with a
wear-proof layer, acquiring a third image of the wear-proof layer
and detecting defects thereon by analyzing the third image.
[0059] In one embodiment, the cylinders according to the invention
may be from 1 cm to 10 m in diameter. In another embodiment, the
cylinders according to the invention may be from 2 cm to 5 m in
diameter. In another embodiment, the cylinders according to the
invention may be from 5 cm to 1 m in diameter. In another
embodiment on, the cylinders according to the invention may be from
7.5 cm to 1 m in diameter. In another embodiment, the cylinders
according to the invention may be between 1-10 cm in diameter. In
another embodiment, the cylinders according to the invention may be
between 10-100 cm in diameter. In another embodiment, the cylinders
according to the invention may be between 1-3 m in diameter.
[0060] In one embodiment, the cylinders according to the invention
may have a diameter within the range of 1 cm to 10 meter. In
another embodiment, the cylinders according to the invention may be
from 5 cm to 7 m wide. In another embodiment, the cylinders
according to the invention may be from 10 cm to 5 m wide. In
another embodiment, the cylinders according to the invention may be
from 20 cm to 3 m wide. In another embodiment, the cylinders
according to the invention may be from 50 cm to 1 m wide.
[0061] In one embodiment, the cylinders according to the invention
may be from 7.5 cm in diameter by 5 cm wide to 0.9 m in diameter by
6 m wide.
[0062] In one embodiment of the invention, the rotogravure presses
for publication gravure may run at least at 15 meters per second.
In another embodiment, the width of the paper used for printing may
be 3.5 m or more.
[0063] Each cell engraved in the engravable material (e.g., in
copper) is intended to have specific characteristics such as depth,
cross-sectional area and shape, as exemplified by FIGS. 1a to 1c
and in FIG. 2, which are dictated by the patterning scheme of
interest. That is, the characteristics of the cells and the pattern
of group(s) of cells correspond to the wanted print out and colors'
tone thereof. In one embodiment of the invention, the printing
cylinder may be fabricated in several fabrication steps, and
various types of defects may occur at any one of the fabrication
steps. Exemplary defects are holes in the copper coating, known as
`pinholes` (FIG. 3), scratches (FIG. 4), variations in the cylinder
circumference, non-uniformity of the cylinder's peripheral surface,
dust particles in the air that impair the development process of
the photoresist layer, streak stains, grinding marks, air bubbles,
cracks in the photoresist layer, etc.
[0064] Defects may be caused by dust or gas bubbles that may reside
in the copper plating and by small particles in the photo-resist
coating. The size of defects may vary. In one embodiment, the size
of defects that can be detected according to the invention ranges
between 0.1-1 microns. In another embodiment, the size of defects
that can be detected according to the invention ranges between 1-5
microns. In another embodiment, the size of defects that can be
detected according to the invention ranges between 3-10 microns. In
another embodiment, the size of defects that can be detected
according to the invention ranges between 5-20 microns. In another
embodiment, the size of defects that can be detected according to
the invention ranges between 10-50 microns. In another embodiment,
the size of defects that can be detected according to the invention
is 50 microns or more. Defects of relatively large sizes may
detrimentally affect the resulting printing results, whereas
defects of relatively smaller sizes (e.g., 1-2 microns) may have
little or no detrimental effects. Unwanted changes in the
characteristics of the cells may degrade the quality of the
resulting prints up to the extent that it may be decided not to use
the defective printing cylinder. In other cases, and where
applicable, defects may be removed, or fixed, after performing
time-consuming and costly correction measures.
[0065] If the engraving may be done by using a photoresist layer to
etch the cells, and the fabrication process may further include,
according to some embodiments of the invention, acquiring a forth
image of the photoresist layer and detecting defects thereon by
analyzing the forth image.
[0066] Of course, an image analysis step may be conveniently
performed at any desired stage; i.e., it may be performed either
immediately after acquiring an individual corresponding image or at
a later stage, for example after acquiring all the images of
interest.
[0067] In one embodiment, the invention provides a system for
detecting defects associated with the fabrication process of a
printing cylinder. The invention provides, according to one
embodiment, a system for detecting defects on an engravable
material, the material being the peripheral surface of a printing
cylinder, the system may include, inter alia, a moveable image
acquiring apparatus for outputting, at different stages of the
fabrication process, data related to an image of an engravable
material, the material being the peripheral surface of a printing
cylinder, the apparatus is capable of moving forwards and backwards
along an imaginary line that is essentially parallel to the
rotation axis of the cylinder, a controllable mechanism, for
rotating the cylinder and operating the image acquiring apparatus,
and a controller, functionally coupled to the controllable
mechanism for causing it to rotate the cylinder and move the image
acquiring apparatus in synchronization, wherein the controller is
configured to receive the data related to the image and to output
data related to the detection of defects on the engravable
material.
[0068] In one embodiment of the invention, the engravable material
may include, inter alia, a metal. In another embodiment, the metal
may include, inter alia, copper, aluminum, zinc or a combination
thereof In another embodiment, the metal may polished. In one
embodiment of the invention, the engravable material may further
include, inter alia, a polymer. In another embodiment, the polymer
may further include, inter alia, rubber.
[0069] In one embodiment of the invention, the engravable material
may include, inter alia, a plurality of cells engraved on the
material according to a predetermined patterning scheme. In another
embodiment, the cells are engraved into the material using
mechanical, electromechanical or laser techniques, or any
combination thereof. In another embodiment, the cells are engraved
into the material by means of etching into the material using a
pattern-generating layer.
[0070] In one embodiment of the invention, the engravable material
may include, inter alia, a wear-proof layer. In another embodiment,
the wear-proof layer may include, inter alia, a metal. In another
embodiment, the metal may include, inter alia, chromium or any
other appropriate substance that may be used to form a wear-proof
layer. In one embodiment of the invention, the engravable material
may include, inter alia, pattern-generating layer. In another
embodiment, the pattern-generating layer may include, inter alia, a
photoresist layer. In another embodiment, the engravable material
may include, inter alia, a transfer layer.
[0071] In one embodiment of the invention, the controller uses a
predefined set of characteristics to identify defective cells and
the position thereof. In another embodiment, the the predefined set
of characteristics may include, inter alia, attern regularity,
dimensions of cells, shape of cells, cross-sectional area of cells,
bridges between adjacent cells, distance between adjacent cells,
depth of cells or any combination thereof. In another embodiment,
the controller is configured to locate the position of defective
cells on the engravable material by comparing data representative
of the image of the engravable material to data representative of a
reference image, wherein the reference image is obtained from the
patterning scheme. In another embodiment, the controller is
configured to detect defects on the surface of the metal. In
another embodiment, the controller is configured to detect defects
related to non-uniformity of the thickness and/or surface of the
pattern-generating layer.
[0072] Referring now to FIG. 5, in accordance to embodiments of the
invention, the system may include a moveable image acquiring
apparatus ("IAA") 505 that may be moveably and closely positioned
opposite the printing cylinder 501 for outputting, at different
stages of the fabrication process, signals representative of a
first, second, third and fourth images. The first, second, third
and fourth images may be acquired from the image carrier after it
is polished, from the image carrier after cells are engraved in it,
from wear-proof layer and from the photoresist layer (i.e., if the
engraving is done using etching). The image acquiring apparatus 505
may move forwards and backwards along a line 513 that is
essentially parallel to the rotation axis of the printing
cylinder.
[0073] The system may further include, in accordance to embodiments
of the invention, a controllable mechanism 508 for rotating the
printing cylinder 501 and for operating the image acquiring
apparatus 505.
[0074] The system may further include, in accordance to embodiments
of the invention, a computer 509 that may be functionally coupled
to the controllable mechanism 508 for causing it to rotate the
cylinder 501and move the image acquiring apparatus 505 in
synchronization. The computer 509 may cause the image acquiring
apparatus 505 to forward to it the signals in synchronization with
the positions of the image acquiring apparatus 505 relative to the
printing cylinder 501. The computer 509 may then analyze the
signals to detect defects in the polished image carrier, engraved
image carrier, wear-proof layer and photo-resist layer.
[0075] Cylinder 501 may typically consist of a base metal (e.g.,
steel) coated with an image carrier (e.g., copper layer, not
shown). Cylinder 501 is rotateable about longitudinal axis 502.
Cylinder 501 may be mechanically supported so as to allow cylinder
501 to rotate about axis 502. Servomotor 503 may provide the
mechanical power required for rotating cylinder 501. Rotary encoder
504 outputs a series of electrical pulses that linearly depend on
the angular displacement of cylinder 501 about the rotation axis
502. That is, the more pulses there are, the more the cylinder 101
is displaced.
[0076] IAA 505 is positioned opposite a portion of the envelope of
cylinder 501, to acquire an image thereof. IAA 505 is moveable in
the `X-Z` plane by servomotors 506 and 507, respectively.
Servomotors 504, 506 and 507 are controlled by three-dimension
("3D") motion controller 508. Controller 508 may be, for example, a
Fanuc, Mitsubishi, ASC or Mega--F motion controller, which is
functionally coupled to Computer 509. IAA 505 may be moved in the
`Z` direction for accommodating for changes in the diameter of
printing cylinders and, in one embodiment of the invention, for
optimizing the `depth of field` of the image acquiring system
substantially through out the image acquiring stage(s).
[0077] Computer 509 controls 3D controller 508 to cause controller
508 to rotate cylinder 501 and LAA 505 to required positions,
depending on the actual stage of the visual inspection of cylinder
501. Computer 509 receives feedback signals, 510 and 511, to
confirm to computer 509 that cylinder 501 and the IAA 505,
respectively, are in the designated position and ready for the next
image pickup by IAA 505. Computer 109 translates the series of
pulses (510) into corresponding relative `Y` coordinate, and the
signal 511 into corresponding `X` coordinate.
[0078] In order to acquire an image of a specific portion of
cylinder 501 (i.e., a portion of interest), computer 509 instructs
controller 509 to rotate cylinder 501 and to move IAA 505
essentially to the same X-Y coordinates and, if required, to move
IAA 505 in the Z direction to get an optimal spacing, in the
optical sense, between IAA 505 and the portion of interest. By
`optimal spacing` is meant the spacing most suitable for acquiring
an image of the portion of interest. IAA 505 may `zoom-in` or
`zoom-out` to obtain the best possible image.
[0079] LAA 505 may transfer images to computer 509 of portions
along a strip on the envelope of cylinder 505, which strip may be
parallel to the rotation axis 502, or it may not be parallel to
axis 502. Then, computer 509 causes controller 108 to rotate
cylinder 501 further, to the next image pickup position, and causes
IAA 505 to transfer to computer 509 images of the consecutive
strip. The latter process may be repeated as many times as required
to obtain images of the printing areas on cylinder 501. The
picked-up, or acquired, images are transferred to computer 509,
which seamlessly combines the individual images to one image.
Cylinder 501 may include fiducial indicia, the image of which may
be forwarded by IAA 505 to computer 509 for calibrating the defects
detection system.
[0080] Image sensor controller ("ISC") 512 may interface between
computer 509 and IAA 505. Computer 509 may instruct IAA 505, via
ISC 512, to acquire an image at the correct timing, after which IAA
505 may transfer the acquired image to computer 509, via ISC 512.
ISC 512 may instruct a lighting source (not shown), which may be
carried by, and moved with, IAA 505, to provide the proper lighting
conditions required when specific images are acquired. That is, the
system may adapt the lighting conditions to the expected type of
defects.
[0081] Computer 509 may have, as input, a data file that relates to
various cylinder information and parameters, such as physical
dimensions and fabrication step (relevant; e.g., to the lighting
conditions and type of image analysis). Computer 509 may also have
as input a data file of the patterning scheme of interest, which
will serve as a reference data against which acquired images may be
compared to detect thereby defects. Computer 509 may also have as
input a data relating to fiducial indicia, such as an initial
position on the tested cylinder, and a source file (bitmap). The
source file is a computer's data file generated by the cylinder
manufacturer and used inter alia for the generation of the printing
pattern. The source file may contain binary data of the pattern to
be printed and alignment fiducial indicia. Computer 509 may output
data relating to: substantially full image of the entire peripheral
surface of cylinder 501, at the different fabrication stages;
defects map; defects list and details thereof, defects images;
marking (option) and circumference measurements of the cylinder 501
under test. By `marking` refers to use of information for the
identification of the pattern, cylinder, shape or dimension
(circumference) of the cylinder. Computer 509 may output the
above-described information as data file. Alternatively, or
additionally, computer 509 may use a graphical user interface
("GUI") to display the data on a display screen. An exemplary GUI
is described in connection with FIG. 11.
[0082] As known in the printing industry, a multi-color print is
made by using different printing cylinders, such as cylinder 501,
each of which is used for printing a different color. Accordingly,
every cylinder involved in a specific print job must meet strict
quality requirements, as explained hereinbefore. Therefore,
computer 509 may be configured to simulate a printing job based on
the association between defects of the involved printing cylinders
and the print job. For this purpose, computer 509 may have as input
the color intended for each printing cylinder. For example,
computer 509 may be advised that the color of cylinder 501 is
blue.
[0083] The simulation process may include, inter alia,
superimposing the differently `colored` cells and defects of the
different printing cylinders, and printing a test colorful printout
based on the superimposed cells. If no defects were detected in any
of the printing cylinders, the colorful printout will highly
resemble the patterning scheme. If, however, one or more major
defects were detected, the colorful printout may not be satisfying
and a decision may be reached regarding whether to fix the
defective cylinder(s) or to fabricate a new cylinder(s).
[0084] FIGS. 7, 8 and 10 show, according to some embodiments of the
invention, processed images of exemplary group of cells for
detecting defects in these cells, the images of which are shown in
FIGS. 6, 8 and 9, respectively.
[0085] Turning now to FIG. 6, it shows, in accordance with some
embodiments of the invention, a group of defective cells
(surrounded by ellipse line 601, for convenience). As shown in FIG.
6, there are walls between cells that are very thin, which means
that the related cells do not conform to the required cells'
characteristics. Therefore, these cells may degrade the quality of
the printing cylinder if located in critical areas in respect of
the patterning scheme. For example, the wall between cells 602 and
603 is very thin, whereas the wall between cells 604 and 605 is
nearly perfect. The wall between cells 604 and 606 is also
defective.
[0086] Turning now to FIG. 7, it shows, in accordance to
embodiments of the invention, a processed image of the group of
cells shown in FIG. 6. The processed image of FIG. 7 was obtained
by employing morphology analysis on the acquired image of the cells
shown in FIG. 6. Cells 603, 604 and 606 do not conform to the
expected cells' characteristics (i.e., in this case in terms of
wall thickness) and, therefore, they are shown in FIG. 7
(circumvented by ellipse 601') `connected` to one another; that is,
after performing the morphology analysis.
[0087] Turning now to FIG. 8, it shows, in accordance with
embodiments of the invention, an exemplary group of cells that
corresponds to the digit `4` (on the left-hand side of the display
screen) and a processed image thereof (on the right-hand side of
the display screen).
[0088] Turning now to FIG. 9, it shows, in accordance with
embodiments of the invention, an exemplary portion of the image
carrier 901, which includes two groups of cells, 902 and 903. Group
of cells 903 is shown including a defect (circumvented by circle
904, for convenience). Referring to FIG. 10, it shows, in
accordance with embodiments of the invention, a processed image of
the portion of image carrier 901 of FIG. 9. Defect 904 (FIG. 9) has
been detected (circumvented by circle 904') in the processed image
shown in FIG. 10, in accordance with embodiments of the
invention,.
[0089] Turning now to FIG. 11, it shows, in accordance with
embodiments of the invention, an exemplary graphical user interface
("GUI") for allowing an operator/viewer to operate the system of
FIG. 5 and for displaying to the viewer a map (e.g., map 1103) of
the defects detected in the polished image carrier, photoresist
layer (wherever applicable), cells, and the wear-proof layer that
protects the image carrier from abrasion.
[0090] In one embodiment, the system according the invention may
further include, inter alia, a GUI to display a picture of the
defects. In another embodiment, the GUI may provide processed data
related to the defects. In another embodiment, the processed data
related to the defects may include, inter alia, a list of the
defects, size of the defects, distribution of the sizes of the
defects, shapes of the defects, the influence of the defects on the
quality of the printing picture or any combination thereof.
[0091] In one embodiment of the invention, the GUI may display to
the viewer a picture of an inspected surface, or portions thereof,
with defects thereon, including a list (e.g., 1101) that specifies
their positions and associated data (e.g., defect type and size,
defects' `X-Y` coordinates, etc.). List 1101 may also include a
factor for indicating the relevancy of each one of the defects. The
GUI may allow the viewer to perform `zoom-in` and `zoom-out` and
see the results in a screen such as screen 1102. The GUI may also
allow the viewer to navigate from one area to another area on the
surface of cylinder 501. The navigation operation may be carried
out by dragging the picture (1103), and the dragging may be
implemented; e.g., by use of a computer mouse or arrows/buttons on
a `touch screen` type display.
[0092] The viewer may choose to zoom into defect 1104, by clicking
on the vicinity of the defect 1104, after which the defected 1104
will be displayed `magnified` in screen 1102. The viewer may select
from list 1101 a defect which is suspected as a major defect, after
which the defect of interest will be shown `magnified` in screen
1101.
[0093] The viewer may select one of several options associated with
the types and characteristics of the detected defects. For example,
the viewer may cause the GUI to show him every defect; i.e.,
regardless of its location, type and/or size, or defects having
specified characteristics. For example, the viewer may instruct the
GUI to display only defects having a size between 5 and 20 microns.
According to another example, the viewer may instruct the GUI to
display only defects having at least length, diameter or
circumference greater than 20 microns. According to another
example, the viewer may instruct the GUI to display only defects
residing within the intended printing area, or outside the intended
printing area. In addition, the viewer may instruct the GUI to
display defects associated with the polished surface of the image
carrier, and/or with the cells, and/or with the wear-proof layer
and/or with the pattern-generating layer.
[0094] Every defect occurred during the fabrication process of the
printing cylinder 501 may be recorded and analyzed, and the defects
displayed to the viewer may be selected from the recorded/analyzed
defects based on the viewer selections, or preferences.
Alternatively, only defects of interest may be recorded and
analyzed, from which defects may be displayed to the viewer based
on his selections, or preferences.
[0095] While certain features of the disclosure have been
illustrated and described herein, many modifications,
substitutions, changes, and equivalents will now occur to those
skilled in the art. It is, therefore, to be understood that the
appended claims are intended to cover all such modifications and
changes as fall within the true spirit of the disclosure.
* * * * *