Flexible fiber optic illuminator and method

A flexible fiber optic illuminator 10 for inspecting an interior space, comprises a thin fiber optic element 12 composed of a plurality of optic fibers 20 arranged in at least one substantially planar layer having front and back sides 32,34. Thin stiffner members 24,26 are arranged adjacent to the optic fibers 20 to provide reinforcement. First and second layers 28,30 of adhesive material having adhering means on one side only, are fixedly adhered to the back and front sides of the planar layer 22. A protective jacket 36 for optic fibers 20 and stiffner members 24,26 is therefore defined by first and second adhesive layers 28,30. A light source 14 coupled to the fiber optic element 12 is provided for illuminating the optic fibers 20. In another embodiment of the invention, a method of inspecting an interior space is provided which comprises providing the fiber optic slot illuminator 10 of the invention and, inserting and positioning the illuminator 10 in the interior space for effective illumination of the interior space.

FIELD OF THE INVENTION 
The invention relates to illuminators, and more particularly, to an 
apparatus and method for illuminating a coating hopper to improve 
inspection thereof. 
BACKGROUND OF THE INVENTION 
Various techniques have been devised to inspect the inside of an interior 
space, such as a coating hopper used in the application of aqueous or 
solvent solutions to a moving substrate. Coating hoppers used in the 
manufacture of sensitized products, such as photographic film and 
photographic paper, generally have narrow slots through which solution 
passes prior to being applied to a web or roll. A typical coating hopper 
(FIG. 1), such as described in U.S. Pat. No. 4,287,240, assigned to 
Eastman Kodak Co., comprises a substantially rectangular body portion 1 
having a slot 2 formed between two substantially rectangular bars 3,4. The 
slot length (L) is defined as the distance from the cavity (C) to the 
slide surface (S). The width of the hopper slot is the distance from one 
end of the hopper to the other or the length of the bars 3,4. In 
operation, the solution contained in the hopper (FIG. 1) is distributed 
through the hopper slot 2, onto the hopper slide subface (S) and, onto the 
web or roll to be coated. Obstructions in the slot of the hopper can 
result in localized widthwise nonuniformities in the delivery of the 
solution to the web or roll. The localized widthwise nonuniformity can be 
of great enough magnitude that it would be considered a defect in the web 
coating and the web would have to be scrapped. Thus, the cleanliness of 
the slots of the "coating hoppers" is critical in the manufacture of 
defect free web coatings. 
One such method of inspecting a coating hopper environment involves the use 
of a hand held light source and a thin piece of transparent plastic 
material. In this method, the inspector holds the plastic material over a 
hopper slot while water is delivered through the hopper slot. The 
inspector then positions the light source over the hopper slot. The 
transparent material together with the running water enables light to be 
directed into the slot. The inspector then peers through the transparent 
material to examine the slot for particulate or foreign objects. Another 
technique also involves the use of a hand held light source and a 
transparent plastic material. In this technique, the inspector inserts the 
plastic material into the hopper slot (with or without water running 
through the hopper slot) and again positions the light source and his or 
her eyes over the slot. The light source illuminates the edge of the 
plastic material to provide a glowing surface which acts as a light source 
to illuminate the hopper slot. The inspector must position the light 
source at the correct angle to assure proper illumination of the slot. The 
inspector must then position his/her eye over the hopper slot to peer into 
the slot. 
The problem with the prior art techniques and apparatus for inspecting a 
slot is the inherent difficulty in performing the inspection. Prior art 
techniques require that the inspector hold, angle, or position a plastic 
material and a light source while simultaneously orienting his/her eye 
over the hopper slot. Thus, the result of having any one of these items 
out of alignment creates a potential for not identifying particulate 
matter that may be present in the slot of the hopper. Other shortcomings 
of the prior art techniques include the presence of reflections and the 
inability to distinguish between the reflections and the actual slot. 
Moreover, the task of inspecting using existing devices is also quite time 
consuming because of the complexity of aligning the various elements of 
the inspection as indicated above, i.e., the plastic, light source, and 
inspector's eye. Consequently, the foregoing shortcomings of prior art 
inspection methods invariably result in residual particulates or 
contaminants in the hopper slot that result in a localized widthwise 
nonuniformity in the web coating. 
The device of Van Slyke, U.S. Pat. No. 3,718,814, is one such attempt to 
provide a fiber optic illuminator for remote inspection. Van Slyke depends 
on the illuminator emitting light laterally of the axis of the bundle 
where the illuminator is desired. This arrangement, however, does not 
permit illumination of the entire work area because there is no axial 
transmission of light. 
Accordingly, there persists a need for an inspection method and apparatus 
therefor that obviates the shortcomings of the prior art techniques, and 
in particular, one that enables the inspector to fully inspect all regions 
of the hopper environment. 
SUMMARY OF THE INVENTION 
It is, therefore, the object of the invention to overcome the shortcomings 
of the prior art. Accordingly, for accomplishing these and other objects 
of the invention, there is provided a fiber optic illuminator comprised of 
a thin fiber optic element. The fiber optic element is comprised of a 
plurality of optic fibers arranged in at least one substantially planar 
layer having front and back sides. Thin stiffner members, preferably 
stainless steel strips, coplanar with the optic fibers, are arranged 
adjacent to the optic fibers. First and second layers of adhesive 
material, having adhering means on one side only, is fixedly adhered to 
the back side and front side, respectively, of the planar layer containing 
the optic fibers and stiffner member. The fixedly adhered adhesive 
material, therefore, defines a protective jacket for the optic fibers and 
stiffner members. The protective jacket has at least one opening through 
its thickness to define the active area of the element. In addition to the 
fiber optic element, the illuminator includes a light source for 
illuminating the fiber optic element and means for attaching the light 
source to the fiber optic element.

DETAILED DESCRIPTION OF THE INVENTION 
Turning now to the drawings, and more particularly to FIG. 2, there is 
shown fiber optic illuminator 10 constructed in accordance with the 
principles of the invention. Fiber optic illuminator 10 is comprised 
generally of a thin fiber optic element 12, a light source 14 for 
illuminating the fiber optic element 12, a fiber optic cable 16 for 
transmitting light from the light source 14 to the fiber optic element 12, 
and a means 18 for attaching the fiber optic cable 16 to the fiber optic 
element 12. 
FIGS. 3 & 4 show the fiber optic element 12 composed of a plurality of 
optic fibers 20 arranged in at least one substantially planar layer 22. 
Spaced stiffner members 24, 26 are shown arranged adjacent to optic fibers 
20 and substantially coplanar therewith. First and second layers 28,30 
comprising an adhesive material having adhering means on one side only is 
fixedly adhered to the front and back sides 32,34 (only one side shown) 
respectively, of the planar layer 22 comprising the stiffner members 24,26 
and optic fibers 20. Layers 28,30, therefore, define a protective jacket 
36 for the coplanar optic fibers 20 and stiffner members 24,26. Protective 
jacket 36 has at least one opening 38 (FIGS. 6-8) through its thickness to 
define the active area of element 12. Layers 28,30 hold the fiber optic 
element 12 together, and are a protective barrier to prevent scratching of 
the hopper interior surfaces or work environment. Stiffner members 24,26 
prevent the fiber optic element 12 from easily being damaged, i.e. bent or 
torn. Optic fibers 20 transmit light from the light source 14 through 
fiber optic cable 16 to the interior of the hopper. Just about any light 
source 14 within the definition of the invention may be used to illuminate 
the optic fibers 20. In one embodiment, a flash light having a handle is 
rigidly attached to the fiber optic element 12. The handle enables the 
user to maneuver the illuminator to various locations in the interior 
space. Also, at one end 40 of the fiber optic element 12, the optic fibers 
20 are arranged together to form a fiber optic bundle 42 and the bundle 42 
is inserted through a stainless steel ferrule 44 (FIG. 3). Ferrule 44 
holds the optic fibers 20 in a bundled arrangement for efficient transfer 
of light from the fiber optic cable 16. Plastic clamping blocks 46,48, in 
the preferred embodiment, position ferrule 44 in relation to the rest of 
the fiber optic element 12, including first and second adhesive layers 
28,30, stiffner members 24,26, and optic fibers 20. Plastic blocks 46,48 
are preferred because they resist damaging the hopper slide surface (S) 
and they slide easily along surface (S). Those skilled in the art will 
appreciate that other means to secure the fiber optic element 12 within 
the requirements of the invention may be used. 
In the preferred embodiment, tape in first and second adhesive layers 28,30 
comprises a non-photoactive, single-sided polyimide adhesive tape 
manufactured by Permacel located New Brunswick, N.J., although other 
adhesive materials within the definition of the invention can be used. 
Non-photoactive tape material is preferred because it use reduces the risk 
of contaminating the emulsion flowing through the coating hopper due to 
residue resulting from ordinary tape wear. The thickness of the adhesive 
material in the preferred embodiment is approximately 0.002 inches. Tape 
having a thickness of about 0.0025 inches or less is acceptable and within 
the contemplation of the invention. 
In the preferred embodiment, stiffner members 24,26 are stainless steel. 
Because the fiber optic element 12 is used in a water environment, the 
stainless steel material prevents the fiber optic element 12 from rusting. 
Stainless steel stiffner members 24,26 also provide excellent resistance 
to tearing or shearing because of the materials strength. The thickness of 
the stainless steel strips 24,26 in the preferred embodiment, is about 
0.002 inches or less. Those skilled in the art will appreciate that other 
materials and means of providing reinforcement for the optic fibers may be 
used, such as, heat sealing the tape along the periphery of the optic 
fibers. 
Optic fibers 20 in the preferred embodiment are manufactured by General 
Fiber Optics, Co. of Cedar Groove, N.J., although other optic fibers 
within the requirements of the invention may be used. In the preferred 
embodiment, the optic fibers 20 in the fiber optic element 12 are arranged 
in a substantially planar layer and the optic fibers within the planar 
layer are substantially parallel (FIG. 6). In this arrangement, light is 
directed substantially parallel to the hopper slide surface (S), as shown 
more clearly in FIGS. 9 & 10. This creates a "headlight effect" in the 
hopper slot, i.e., the light is directed from the fiber optic element 12 
to along the longitudinal axis of the hopper slot. Any particulate matter 
in the hopper slot will block the light being directed along the hopper 
slot resulting in a localized highlight/shadow effect which can be 
detected by the inspector. In another embodiment (FIG. 7), the optic 
fibers 20 are arranged such that the light is directed upwardly toward the 
hopper slide surface (S), as shown more clearly in FIG. 11 & 12. This 
creates a "backlighting" effect in the hopper slot. Any particulate matter 
in the hopper slot will block light being directed across the slot 
resulting in an area of lower light intensity which can be detected by the 
inspector. Finally, in yet another embodiment (FIG. 8), the optic fibers 
20 are arranged both upwardly toward and parallel to the hopper slide 
surface (S), as shown more clearly in FIGS. 13 & 14. In this arrangement, 
light from the element 12 is directed partially in a "headlighting" and a 
"backlighting" manner, as described above. 
Further, according to the requirements of the invention, optic fibers 20 
may have a thickness of less than about 0.0035 inches, although less than 
about 0.003 inches is preferred. The determining factor for the thickness 
selection of the polyimide adhesive tape, stiffner members 24,26, and 
optic fibers 20 is that the total thickness of the fiber optic element 12 
must be less than 0.008 inches. Those skilled in the art will appreciate 
that for larger hopper slot sizes, the overall dimensions of the apparatus 
of the invention may be larger than 0.008 inches. According to experiments 
conducted by the inventors, the apparatus of the invention is sized 
approximated 0.002 inches less than the hopper slot size. Thus, a 0.008 
inch thick apparatus would be used to inspect a 0.010 inches hopper slot. 
While there are many means of attaching the fiber optic element 12 to the 
cable 16, FIG. 5 shows the preferred means used in the invention. The 
fiber optic element 12 and fiber optic cable 16 are joined together using 
a common fitting and secured set screws 50. 
In operation, the flexible fiber optic illuminator 10 of the invention is 
used to inspect an interior space, such as a coating hopper slot, for 
particulate matter that was not completely removed by the cleaning 
procedure or residual air that was not completely removed by the 
production preparation procedure. The inspection for remaining 
particulates in the hopper slot is performed in the following manner. 
First, the light source 14 of the flexible fiber optic slot illuminator 10 
is turned on and the fiber optic element 12 is inserted into the hopper 
slot. FIG. 9 shows the preferred embodiment of the fiber optic element 12 
positioned in a hopper slot. The arrows indicate the direction of light 
emitted from the fiber optic element 12 into the hopper slot. In FIG. 10, 
the fiber optic element 12 of FIG. 9 is shown as positioned in the hopper 
slot. FIG. 11 depicts an alternative embodiment of the fiber optic element 
12 positioned in a hopper slot, with arrows indicating the direction of 
light directed from the fiber optic element 12 into the hopper slot, the 
depth penetration being limited by blocks 46,48. In FIG. 12, the fiber 
optic element 12 of FIG. 11 is shown as positioned in the hopper slot, the 
depth of penetration being limited by blocks 46,48. The operator positions 
his/her eye above the hopper slot enabling himself/herself to see directly 
into the hopper slot. The operator then adjusts the light source 14 to the 
correct intensity for optimum viewing efficiency in the hopper slot. The 
operator then scans the entire hopper slot using the device. The operator 
looks for obstructions in the light path to his/her eye or for localized 
highlights or shadows which would indicate an obstruction in the hopper 
slot, i.e., a particle or contaminant. The angle of the light emitted by 
the fiber optic element 12 can be changed by holding the means for 
attaching 18 or handle at a different angle to the surface of the hopper. 
By doing this, the operator can change the direction of the light from out 
of the slot toward the operators eye to along the slot toward the end of 
the hopper. 
Thus, in another embodiment of the invention, a method of inspecting a 
coating hopper comprises providing a fiber optic illuminator 10, as 
described above; inserting the illuminator 10 into the slot of the hopper 
slot such that the fiber optic element 12 extends into the region of 
inspection; maneuvering the light source 14 of illuminator 10 for 
effective illumination of the slot. Moreover, the light intensity and 
light angle can be adjusted to accommodate the viewing requirements of the 
operator. 
The inspection method of the invention can be performed with or without 
water running through the hopper slot, as described above. Operator 
discretion is employed to determined whether or not running water is 
necessary for optimum viewing of the hopper environment. Thus, the present 
inspection method provides a novel technique for observing latent hardened 
particles, and the like, on hopper slot walls as well as detecting air 
bubbles in the hopper slot and cavity. 
Accordingly, an important advantage of the present invention is that it 
provides an effective apparatus and method for fully inspecting all 
regions of a hopper, particularly a coating hopper, despite obstructions 
that may exist in the hopper. 
The invention has therefore been described with reference to certain 
embodiments thereof, but it will be understood that variations and 
modifications can be effected within the scope of the invention.