FIBEROPTIC ILLUMINATION: LED-lit woven optical fiber takes on innovative applications

While the usual purpose of optical fiber is to guide light along a longitudinal axis, Lumitex (Strongsville, OH) is exploiting advantages to be obtained by defeating that purpose, for instance in creating optically interactive apparel for people who play laser tag. The company’s laser-tag vest emits light of appropriate color (either blue or green) to designate the wearer’s team. The emitted color changes to red when the wearer is “tagged” by a laser beam, but only when the wavelength indicates that it came from a member of the opposite team. The vest is woven of plastic (acrylic) optical fibers that carry the incident laser light to a photodiode and controlling circuitry for a three-chip red/green/blue LED array.

The weaving method enables light to be transmitted not just along the axis of a fiber, but also through the sides of one fiber into adjacent fibers. Lumitex uses two techniques. One uses optical fiber woven into a cloth to create layers that can be built up into a panel or other lighting device. Another technique, dubbed “Uniglo,” uses optical fiber mounted on a back reflector to create lighting panels as thin as 0.013 in. In both cases a computer-controlled etching process ensures uniform light distribution; both methods are used in single or multiple layers along with laminates (such as back reflectors and diffusers) to produce lighting panels in custom shapes, sizes and configurations for many applications (see figure).

Product offerings at Lumitex, which has been launching light from LEDs into fiber since the early 1990s, are beginning to encompass lasers. “Lasers are emerging as a source, but we don’t know yet what the customer demands will be,” says Lumitex president Peter Broer.