U.S. patent application number 09/490513 was filed with the patent office on 2002-04-25 for apparatus for laser marking indicia on a photosensitive web.
Invention is credited to Press, David C., Shaffer, Wayne K., Smith, Gregory A..
Application Number | 20020047890 09/490513 |
Document ID | / |
Family ID | 23948379 |
Filed Date | 2002-04-25 |
United States Patent
Application |
20020047890 |
Kind Code |
A1 |
Shaffer, Wayne K. ; et
al. |
April 25, 2002 |
APPARATUS FOR LASER MARKING INDICIA ON A PHOTOSENSITIVE WEB
Abstract
An apparatus for laser marking indicia on a moving
photosensitive web substantially reduces fog spots on the web
caused by impinging laser energy. A nozzle element configured to
conform to the outlet end of the laser beam tube enables reduction
of fog spots on photosensitive web.
Inventors: |
Shaffer, Wayne K.;
(Penfield, NY) ; Press, David C.; (Webster,
NY) ; Smith, Gregory A.; (Fort Collins, CO) |
Correspondence
Address: |
PATENT LEGAL STAFF
EASTMAN KODAK COMPANY
343 STATE STREET
ROCHESTER
NY
14650-2201
US
|
Family ID: |
23948379 |
Appl. No.: |
09/490513 |
Filed: |
January 25, 2000 |
Current U.S.
Class: |
347/241 |
Current CPC
Class: |
G03B 27/521 20130101;
G03B 17/245 20130101 |
Class at
Publication: |
347/241 |
International
Class: |
G01D 015/14 |
Claims
What is claimed is:
1. Apparatus for marking indicia on a moving photosensitive web,
comprising: a source of laser energy; laser printer means operably
connected to said source of laser energy, said laser printer means
being provided with: a laser head; a laser beam tube connected to
said laser head, said laser beam tube having an active end; and, a
nozzle element structurally associated with said active end of said
laser beam tube, said nozzle element comprising a chamber having a
laser energy inlet end and a laser energy outlet end; an air jet
member arranged in said chamber for directing a burst of air onto a
laser beam impingeable surface; at least one lens arranged in said
chamber for focusing each one of a plurality of laser beams passing
through said chamber; a lens cleaning member arranged in said
chamber proximate to said at least one lens; and, a vacuum port
extending from said chamber, said vacuum port providing means for
evacuating said chamber of smoke and debris generated during laser
marking; and wherein said laser head has a plurality of lasers
disposed therein for generating a plurality of laser beams, a lens
arranged in said laser beam tube for focusing said each one of a
plurality of laser beams along a predetermined optical path through
said laser beam tube and into impinging contact with said moving
photosensitive web thereby producing said indicia thereon.
2. The apparatus recited in claim 1 wherein a laser beam
attenuating member is disposed in said optical path for attenuating
said each one of a plurality of laser beams.
3. The apparatus recited in claim 2 wherein said laser beam
attenuating member comprises a metallic mesh screen.
4. The apparatus recited in claim 3 wherein said metallic mesh
screen is made from materials selected from the group consisting of
brass, steel, copper, and metal alloys.
5. The apparatus recited in claim 3 wherein said mesh screen has a
plurality of openings each one of said plurality of openings having
a wire diameter in the range of from about 0.00025 inches (0.000635
cm) to about 0.025 inches (0.0625 cm) and a clear opening having a
dimension in the range from about 0.001 inches (0.00254 cm) to
about 0.100 inches (0.254 cm).
6. The apparatus recited in claim 3 wherein said mesh screen has a
plurality of openings each one of said plurality of openings having
clear opening dimension of 0.055 inches (0.140 cm), and a wire
diameter of 0.016 inches (0.041 cm).
7. The apparatus recited in claim 1 wherein said laser energy
outlet end has a generally conical shape.
Description
FIELD OF THE INVENTION
[0001] The invention relates generally to the field of laser
marking systems. More particularly, the invention concerns an
apparatus that uses laser energy for marking indicia on
photosensitive web with a dramatic reduction in the occurrence of
fog on the photosensitive web.
BACKGROUND OF THE INVENTION
[0002] Conventional edge marking in photographic film manufacturing
involves printing some sort of identification indicia along the
edge of film rolls during the finishing operation. Edge marked film
has direct verification of roll identity, sheet identity and waste
identity during all stages of the manufacturing process.
Importantly, edge marked film provides accurate footage
identification that enables operators to quickly identify, trace
and remove film imperfections, thereby minimizing the amount of
product waste. More generally, edge marked film increases process
understanding by allowing process interactions to be more closely
identified with their corresponding effect on the product.
Traditional embossing marking techniques are being replaced by
laser edge marking. Current mechanical embossing techniques
(embossing wheels) are not programmable, generate poor quality
marks and require excessive maintenance. Laser edge marking, on the
other hand, is particularly advantageous in the industry because it
provides a permanent record and can be read before and after film
processing.
[0003] Advances in laser technology enabled the use of a dot matrix
CO.sub.2 laser marking system to be used to replace existing
embossing technology. Off the shelf laser marking equipment will
mark the film at required throughput rate, however, an unacceptable
level of fog spots occurred.
[0004] Thus, a particular shortcoming of these advanced high
powered laser systems used for edge marking photosensitive film is
that they produce a by-product that impinges on the film surface.
Laser energy by-products in the form of a plume of energized smoke
and irradiated debris on the film surface is known to cause the
localized fogging on the film. Experience has shown that localized
fogging is not easily eliminated even when the film is immersed in
a 99.8% nitrogen atmosphere.
[0005] More recent developments in laser technology enabled the
development of high speed marking systems using short pulse lasers.
Short pulse laser exposure on photosensitive film shows some
promise in reducing the occurrences of fog spots. Our experience
also indicates that an air jet directed at the laser impingement
point on the film surface further reduce the occurrence of fog.
Statistical methods have been employed to gain information on fog
incidence reduction when laser marking photosensitive film. It has
been experimentally proven that laser pulse width does not have a
significant effect on fog. Importantly, however, our experience
does suggest that laser peak power has a dramatic effect on the
reduction of occurrences of fog spots by a factor of about 30. In
addition, significant statistical benefits can be derived from an
air jet that we believe can further reduce the incidences of fog
spots by a factor of about 10.
[0006] Hence, laser marking without controlling peak power will
result in 14% to 50% of the laser-generated dots of dot matrix
characters to have fog spots around the dots. There are no present
attempts known to the inventors to control peak power in laser edge
marking devices because embossing techniques still remain prevalent
in the industry and, more importantly, the fog spots remain a
significant quality issue during the finishing process.
[0007] Therefore, a need persists for variable information to be
permanently marked on the edge of each sheet of photosensitive web,
such as photographic film, without significant incidences of fog
spots on the surface of the film.
SUMMARY OF THE INVENTION
[0008] It is, therefore, an object of the invention to provide an
apparatus for laser marking indicia on a moving photosensitive web
while substantially reducing the occurrence of deleterious fog
spots on the photosensitive web.
[0009] It is another object of the invention to provide an
apparatus for exposing a moving photosensitive web to laser energy
while controlling the peak power of the laser energy.
[0010] Yet another object of the invention is to provide an
apparatus for laser printing indicia on a photosensitive web by
further directing a jet of air onto the laser energy impinged
surface of the photosensitive web.
[0011] It is a feature of the invention that the apparatus for
laser marking indicia on a moving photosensitive web has a nozzle
element for reducing the incident of fog spots on the laser
impinged photosensitive web.
[0012] To accomplish these and other objects and features and
advantages of the invention, there is provided, in one aspect of
the invention, an apparatus for marking indicia on a moving
photosensitive web, comprising:
[0013] a source of laser energy;
[0014] laser printer means operably connected to said source of
laser energy, said laser printer means being provided with:
[0015] a laser head;
[0016] a laser beam tube connected to said laser head, said laser
beam tube having an active end; and,
[0017] a nozzle element structurally associated with said active
end of said laser beam tube, said nozzle element comprising a
chamber having a laser energy inlet end and a laser energy outlet
end; an air jet member arranged in said chamber for directing a
burst of air onto a laser beam impingeable surface; at least one
lens arranged in said chamber for focusing each one of a plurality
of laser beams passing through said chamber; a lens cleaning member
arranged in said chamber proximate to said at least one lens; and,
a vacuum port extending from said chamber, said vacuum port
providing means for evacuating said chamber of smoke and debris
generated during laser marking; and wherein said laser head has a
plurality of lasers disposed therein for generating a plurality of
laser beams, a lens arranged in said laser beam tube for focusing
said each one of a plurality of laser beams along a predetermined
optical path through said laser beam tube and into impinging
contact with said moving photosensitive web thereby producing said
indicia thereon.
[0018] It is, therefore, an advantageous effect of the present
invention that laser edge markings on photosensitive web can be
accomplished with an apparatus that is easy to operate, simple and
cost effective to produce and that substantially reduces the
occurrence of fog spots on the photosensitive web.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The above and other objects, features, and advantages of the
present invention will become more apparent when taken in
conjunction with the following description and drawings wherein
identical reference numerals have been used, where possible, to
designate identical features that are common to the figures, and
wherein:
[0020] FIG. 1 is a schematic diagram of a laser edge marking system
of the invention;
[0021] FIG. 2a is a front elevational view of the laser head
showing an attenuating member therein;
[0022] FIG. 2b is a top elevational view of the mesh screen;
[0023] FIG. 2c is an isometric view of the beam splitter;
[0024] FIG. 3 is a graph of the relationship between focus position
effect (inversely proportional to peak power) on fog spots formed
on the photosensitive film;
[0025] FIGS. 4 and 5 show the effects of an attenuating screen of
the invention on incidents of fog spots; and, FIG. 6 is an
isometric view of the nozzle element used in the apparatus of the
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0026] Turning now to the drawings, and in particular to FIG. 1,
the apparatus 10 according to the principles of the invention for
printing indicia on an moving laser impingeable surface, such as a
moving photosensitive web 1, is illustrated. According to FIG. 1,
apparatus 10 has a source 12 of laser energy for producing a range
of laser power. A laser printer means 14 is operably connected to
the source 12 of laser energy.
[0027] Referring to FIG. 1, laser printer means 14, preferably a
Domino DDC2 Digital Laser Coder, manufactured by Domino Lasers,
Inc. of Gurnee, Ill., is provided with laser head 16 and a laser
beam tube 18 structurally associated with the laser head 16. Laser
beam tube 18 has an active end 20 positioned proximate to the
moving photosensitive web 1 and a plurality of lasers 22 disposed
in the laser beam tube 18 for generating a plurality of laser
beams. Importantly, a nozzle element 40, described more fully
below, is structurally associated with the active end of the beam
tube 18, as shown in FIGS. 1 and 2a.
[0028] According to FIG. 2a, in the preferred apparatus 10, seven
lasers 22 are employed, each being a medium power CO.sub.2 laser
that operates at about 30 watts maximum power. Each laser 22
corresponds to a row of dots in a dot matrix character. This type
of laser 22 has enough power to mark small characters or indicia
into photosensitive materials, for example emulsion coated film. At
least one lens 49 is arranged in the laser beam tube 18 for
focusing each one of the plurality of laser beams along a
predetermined optical path 23 and into impinging contact with the
laser impingeable material, such as photosensitive web 1 thereby
producing indicia thereon.
[0029] Referring to FIGS. 2a-2c, means for controlling peak power,
preferably a laser beam attenuating member 26 (FIG. 2a), is
disposed in the optical path 23 for attenuating the laser beams
passing through the laser beam tube 18. In the preferred
embodiment, attenuating member 26 is a metallic mesh screen 30
(FIG. 2b) arranged in the laser beam tube 18. Preferably, metallic
mesh screen 30 is made of materials selected from the group
consisting of brass, steel, copper and metal alloys. We consider
copper to be most preferred because it has more suitable thermal
conductivity and reflective characteristics of the wavelengths
contemplated by the invention. Moreover, the mesh screen 30 has a
plurality of openings 32. Openings 32 each have a wire diameter in
the range of from about 0.00025 inches (0.000635 cm) to about 0.025
inches (0.0635 cm) and a clear opening having a dimension in the
range from about 0.001 inches (0.00254 cm) to about 0.100 inches
(0.254 cm). In the preferred embodiment, mesh screen 30 has clear
opening dimension of 0.055 inches (0.140 cm), and a wire diameter
of 0.016 inches (0.041 cm).
[0030] As shown in FIG. 2c, alternatively, attenuating member 26
may include at least one beam splitter 27 arranged along the
optical path in the beam tube 18. Moreover, attenuating member 26
may include a neutral density filter (not shown).
[0031] Referring to FIGS. 2a and 6, nozzle element 40 has a
preferably generally cylindrical shaped chamber 42 with a laser
energy inlet end 44 and a laser energy outlet end 46. Inlet end 44
is adaptable to any laser energy output device, such as a laser
marking system for marking indicia on photosensitive web. Laser
energy outlet end 46 is configured to focus beams of radiation onto
a moving photosensitive web material 1 and to be spaced proximate
to the moving photosensitive web material 1. Preferably, laser
energy outlet end 46 has a generally conical shape for
concentrating the vacuum nearest the photosensitive web material 1
and, a generally conical lip 47 for concentrating the air
surrounding lens 49.
[0032] Referring to FIGS. 2a and 6, an air jet member 48 is
arranged in the chamber 42 near the outlet end 46. Air to air jet
member 48 may be supplied by any general source (not shown). Air
jet member 48 is configured for directing a burst of air onto a
laser beam impingeable surface, such as a photosensitive web
material 1 positioned proximate to the air jet member 48.
[0033] Referring to FIG. 2a, chamber 42 may have at least one lens
49 arranged therein for focusing each one of a plurality of laser
beams passing through the chamber 42. Lens 49 is preferably a short
focal length zinc selenide lens. Lens 49 may be mounted in any one
of a variety of ways in chamber 42, for instance using a typical
lens mount (not shown).
[0034] Referring to FIGS. 2a and 6, a lens cleaning member 50 is
arranged in the chamber 42 proximate the lens 49. Nozzle element 40
was developed to keep the lens 49 clean, prevent plume and draw
away vapors associated with impinging laser energy. In the
preferred embodiment, lens cleaning member 50 is a positive air
flow pattern surrounding the lens 49 that shields the lens 49 from
particulate matter. Alternatively, lens cleaning member 50 may be a
burst of air directed at the lens 49 (not shown).
[0035] Turning again to FIGS. 2a and 6, chamber 42 further has a
vacuum inlet port 52 and a vacuum outlet port 54 in fluid
communication with the chamber 42. Vacuum outlet port 54 provides
means for evacuating the chamber 42 of smoke and debris generated
during laser marking. To concentrate vacuum at a predetermined
location, vacuum outlet port 54 preferably has a generally conical
shape. Affluence generated by the marking process without vacuum
resulted in no detection of cyanide, sulfur dioxide, hydrochloric
acid, or carbon monoxide. Carbon dioxide could be detected but the
level was below exposure limits. Mercury, silver and aldehydes
vapors were adequately removed by the Fumex FA2 fume extraction
machine.
[0036] Vacuum inlet port 52, connected to a source of vacuum (not
shown), provides a means for receiving such particulates that are
ejected through vacuum outlet port 54.
[0037] FIG. 2a illustrates nozzle element 40 adapted to a laser
beam tube 18 having a plurality of lasers 22 therein. Laser beam
tube 18 is preferably the output end of a laser marking system 10
(only partially shown).
[0038] Preferably, nozzle element 40 is made from any structurally
rigid material such as any metallic material. We prefer using
aluminum because it is light-weight and can be easily formed.
[0039] Referring to FIG. 3, peak power of each of the plurality of
lasers 22 was determined to be a primary factor controlling the
incidences of fog spots occurring on the photosensitive web
material 1 after impingement by laser energy. According to FIG. 3,
we observed that the incidences of fog spots decreased as the focus
position of the lens 49 moved further out of focus. This
corresponded to an effective reduction in peak power that enabled
the inventors to select controlling peak power for minimizing the
incidences of fog spots.
[0040] Referring to FIGS. 4 and 5, performance of mesh screens 30
used as laser beam attenuating member 26 in the apparatus 10 of the
invention are illustrated. According to both FIGS. 4 and 5, the
incidences of fog spots are well below expected levels generally
experienced in the industry.
[0041] In another embodiment of the invention, a method of
controlling peak power of a laser marking apparatus 10 (FIG. 1)
adapted for marking predetermined indicia 2 on a moving
photosensitive web material 1 comprises the steps of providing a
source 12 of laser energy. A laser printing means 14 (described
above) is structurally connected to the source 12 of laser energy
which has a laser head 16, a laser beam tube 18 connected to the
laser head 16. As indicated above, the laser beam tube 18 has an
active end 20 and a nozzle element 40 arranged on the active end 20
positioned proximate to the moving photosensitive web material 1. A
plurality of lasers 22 is disposed in the laser head 16 for
generating a plurality of laser beams. A lens 49 is arranged in the
laser beam tube 18, preferably near the active end 20, for focusing
each one of the plurality of laser beams along a predetermined
optical path 23 (FIG. 2a) and into impinging contact with the
moving photosensitive web material 1 thereby producing indicia 2
thereon.
[0042] Further, the source 12 of laser energy is activated so as to
energize each one of the plurality of lasers 22 for impinging laser
beams forming predetermined indicia 2 on the moving photosensitive
web material 1. Importantly, the peak power to each one of the
plurality of lasers 22 is controlled, as described above, for
minimizing fog spots on the photosensitive web material 1.
[0043] The invention has been described with reference to a
preferred embodiment. However, it will be appreciated that
variations and modifications can be effected by a person of
ordinary skill in the art without departing from the scope of the
invention.
Parts List
[0044] 1 photosensitive web material
[0045] 2 indicia
[0046] 10 apparatus of the invention
[0047] 12 source of laser energy
[0048] 14 printer means
[0049] 16 laser head
[0050] 18 laser beam tube
[0051] 20 active end of laser beam tube 18
[0052] 22 lasers
[0053] 23 optical path
[0054] 26 means for controlling peak power or laser beam
attenuating member
[0055] 27 beam splitter
[0056] 30 metallic mesh screen
[0057] 32 openings in metallic mesh screen 30
[0058] 40 nozzle element
[0059] 42 chamber
[0060] 44 laser energy inlet end
[0061] 46 laser energy outlet end
[0062] 47 lip
[0063] 48 air jet member
[0064] 49 lens
[0065] 50 lens cleaning member
[0066] 52 vacuum inlet port
[0067] 54 vacuum outlet port
* * * * *