Optical Fiber Fabric Displays

40 Optics & Photonics News ■ April 2005

Optical FiberFabric Displays Vladan Koncar

1047-6938/05/04/0040/5-$0015.00 © Optical Society of America

April 2005 ■ Optics & Photonics News 41

Imagine donning a jacket

that can play a video or

display various images that

have been downloaded

from the Internet. A group

of French researchers have

developed optical fiber

fabric displays that could

make such “communica-

tive clothing” possible.

In this article, Vladan

Koncar describes a new

approach to flexible textile

display with potential

applications that extend

far beyond fashion. F lexible displays can be created on textiles by producing ascreen matrix using the texture of the fabric during theweaving process. A small electronic device that is integrated

into the system controls the Light Emitting Diodes (LEDs) thatilluminate groups of fibers. Each group provides light to onepixel on the matrix.

These displays are very thin and ultra lightweight—two characteristics that could enable many innovative applications.Although initially developed for clothing, the displays could beused to exhibit information or designs in cars, portable elec-tronic devices and even houses and buildings. Indeed, researchon the design and development of flexible displays based on processed optical fibers has opened up new frontiers in fashion,public safety, automotive equipment and home decoration.

Weaving optical fibersPoly(methyl methacrylate) (PMMA) optical fibers possess arigidity and fragility that make them different from most tradi-tional textile fiber threads and filaments. With regard to sectiondiameter, a good compromise must be reached: A diameter thatis too large can cause inflexibility, while a too-small diameterinduces a low shear resistance and loss of light intensity.

We used fibers with a diameter of0.5 mm to make the first prototypes. Wehave also conducted tests on fibers with adiameter of 0.25 mm, but further devel-opments in the process of weaving arestill required to ensure sufficient fabricresistance in bending.

Weaving takes place on a traditionaltwo-dimensional loom. The optical fibers can be woven or placed in a chain,in addition to other kinds of yarns.Therefore, it is theoretically possible toobtain an optical fiber X-Y network.However, this would present several disadvantages:

• The grid (and, hence, the resolution)would not be very dense and the fabricwould be extremely rigid because ofthe relatively high radius of curvatureof optical fibers.

• Constituting an optical fiber chain is very long and very expensive.

• The resolution would be tiny.

It is also possible that a three-dimen-sional structure in weaving would notbring any significant advantages.

Thus, our initial plan was to develop afabric comprising optical fibers for weftsand silk in chain. Other natural, artificialor synthetic yarns could also have beenused to constitute the chain. Yarns werechosen for the chain with the aim ofachieving good flexibility in the fabric,fine titration and an improved capacityto diffuse and reflect the light emitted byoptical fibers for better legibility of infor-mation. An example of an optical fiberfabric display (OFFD) weaved structure isshown in Fig. 1. Different textile finishingmethods are being tested—either in past-ing or in coating—to guarantee grid sta-bility and flame resistance and to enableoptimal light emission intensity and con-trast.

Display matrix designThe screen for fabric displays comprises anumber of surface units, or pixels; eachone can be illuminated by a light sourceemitted from one side of the fabric byone or several PMMA optical fibers withdiscrete index variation. The pixels aredirectly formed on optical fibers while


OPTICAL FIBER FABRIC DISPLAYS

Figure 1. Scanningelectron microscopepicture of OFFDstructure (a two-layer basic-velourfabric).

Figure 2. Principle of lateral light emission. (a) Original optical fiber; (b) processed optical fiber.

Original optical fiber

Emitted lightMicro perforation

Light rays(a)

(b)

Cladding

Core(PMMA)

Processed optical fiber

Figure 3. Micro perforation obtained by mechanical treatment (particle projected on thecladding of optical fiber). Picture obtained by nanoscope.

Micro perforation

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x 2.000 �m/divy 533.972 nm/div

�m8

64

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April 2005 ■ Optics & Photonics News 43

transversely forming a spout of light on the fabric. The process consists ofgenerating micro-perforations that reachinto the core of the fiber (Fig. 2). Theremainder of the optical fiber, which didnot receive any specific processing, con-veys the light without being visible on the surface.

Two processing techniques have beendeveloped for optical fibers. The first is amechanical treatment by the projectionof micro particles with different veloci-ties on the optical fiber’s cladding. Theresult is presented in Fig. 3. The secondtechnique uses different chemical sol-vents to make these micro perforations;this method seems to produce a betterfinal result. (A chemically processedcladding surface is shown in Fig. 4.)Finally, Fig. 5 shows the chemically processed fiber obtained by a scanningelectron microscope.

There are three methods that are usedto light ON and OFF static patterns onthe fabric (texts, logos and scanned pic-tures), which we adapted to develop ourown technique. A basic fabric is used inthe first method. The lighting zone to beprocessed, which is composed of opticalfibers, is delimited by a stencil key. Thepicture remains static—with eventualcolor changes—but can offer quite a highresolution.

In the second method, the zone to belit is formed during weaving on aJacquard loom before being processed.The remaining, inactive fabric is com-posed of the floating fibers on the back of the fabric.

A third method uses a two-layeradapted basic-velour fabric that makesoptical fibers as visible as possible, butwith sufficient consistency of fabricstructure. Prior to the weaving process,the optical fibers are chemically treated,enabling the specific dynamic lightingzones to be created.

We modified these techniques by cre-ating specific weaving armor and anadapted lighting control in order to gen-erate variable information on the samefabric zone. We developed a matrix thatmakes it possible to display a great deal ofbasic information, such as texts, logos orother patterns, in a static or dynamic way.

Because a fabric display can only beproduced by columns made of a single


Figure 4. Micro perforations obtained by chemical treatment (solvent action on thecladding of optical fiber). Picture obtained by nanoscope.

Figure 5. Microperforationobtained bychemical treat-ment (solventaction on thecladding of opti-cal fiber). Pictureobtained by scan-ning electronmicroscope.

optical fiber or group of fibers, we had tocreate lines artificially. Similar to the pro-cess that would be used with two super-imposed patterns to be lightened on thesame column, this involves alternatingtwo consecutive weft fibers—one for thefirst pattern, and the other for the second.Each is processed on a precise section inorder to re-emit light at a specific place.

The principle is the same for threesuperimposed patterns, except that onefiber is taken out of three for each pat-

tern. When the weaving is sufficientlytight, a visual impression is given of full,enlightened zones. Chain wires will beable to help diffuse the light toward thedark zones between lightened segments.The number of rows to be producedseems limited by the technique, insofaras, on the same unit zone, more darkzones are produced than lightened ones.The appreciation of the definitionwill then be based on the size of the pixels and the screen, in addition to the

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x 2.000 �m/divz 3959.939 nm/div

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distance from which people watch thescreen.

Various light sources can be used tofeed the matrix. The choice mainlydepends on the number of fibers con-nected to each source and the level ofpower consumption. For the first proto-types, we used high luminous LEDs thatare 3 mm in diameter. LED technologyhas many advantages, as diodes can beeasily driven by electronics under lowvoltages (2V to 4V, depending on thecolor). Therefore, many “light effects”can be generated on the display, such asflashing or varying the intensity of thelight, providing all kinds of animatedmovies.

The very first OFFD was displayed ona jacket (pictured on p. 41). It comprisesa screen matrix specially designed to dis-play on one line three 60 mm � 60 mmalphanumeric characters, each made upof three rows and three columns using0.5 mm diameter optical fibers and a 7fibers/cm width density. Each pixel iscomposed of four fiber segments and is



controlled by one LED located in the lin-ing of the cloth, on one side of the OFFD.The color of the pixels is determined bythe corresponding LEDs.

OFFDs offer another possibility:Although the definition is limited by thenumber of rows, it is possible to repeaton fabric the same line of characters orpatterns in the direction imposed byoptical fibers. The fixed or animated pat-tern reproduction can be used for purelydecorative applications; for example, tocreate a mural tapestry adapting its colorsto the clothes worn by the occupants ofa room.

Implications and applicationsOptical fiber screens provide access tosimple and animated visual information,such as texts or pictograms. It is possibleto download, create or exchange visualsvia the appropriate Internet gateway.Conceivably, images or text could be sentusing wireless technology from a com-puter or a mobile Internet terminal to anarticle of clothing.

The main functions of the new proto-types are:

• To “be seen,” for security, publicity,recreational or aesthetic purposes

• To show one’s affiliation or supportfor a group

• To personalize one’s clothing accord-ing to the latest fashions

• To communicate or exchange infor-mation or to signpost advice.

Fabrics based on flexible display tech-nology have the obvious potential toinfluence fashion designers, but they havea variety of other useful applications aswell. OFFDs can be used as displays formobile phones, PDAs (personal digitalassistants), wearable computers and otherportable electronic devices.

There is also enormous potential forfirefighting and police applications. Forexample, information and warningscould be displayed on clothes—whichcould both increase public safety andhelp officers and firefighters to operate in remote and challenging conditions.

The interior of cars contain manyflexible elements that could be used todisplay relevant information that mighthelp drivers navigate or avoid accidents.Finally, houses and buildings could useOFFD technology to display or enhancedrawings, pictures and lighting.

In this digital age, information is vir-tually everywhere and a multitude ofscreen and display technologies will benecessary to keep up with the demand.OFFDs have shown great promise as anew and interesting way to presentimages and information.

Vladan Koncar ([email protected]) is profes-sor at ENSAIT textile engineering institute (EcoleNationale Supérieure des Arts et Industries Textiles),Roubaix Cedex, France.

Further Reading

1. V. Koncar, Textiles à Usage Techniques, 47, 22-7(2003).

2. V. Koncar et al., Wearable Photonics and Electronics,Woodhead Publishing Limited, Cambridge, U.K.,2005, 155-74.

3. E. Deflin et al., Proc. 2001 The 6th Asian TextileConference (ATC-6) (Hong Kong PolytechnicUniversity, Hong Kong, 2001), 211-9.

4. E. Deflin et al., Proc. 2001 Avantex Conference,(Frankfurt, Germany, 2002), 1, 222-35.

5. A. Bernasson and H. Vergne, Optical Fiber withMultiple Point Latéral Illumination, International Patentno. PCT/FR94/01475 (1998).

Optical fiber screens provide access to simple and animated visual information, such as texts or pictograms.

Optical Fiber Fabric Displays

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