Fiber Optic Backlighting

Membrane switch keys and nomenclature can be backlit using a fibre optic layer driven with an LED. The fibre optic backlighting panel is fabricated from .010 optical fibres applied to a reflective backing with a ferrule end tip where the LED is inserted. A single led is generally sufficient to illuminate up to 40 square inches. Two or more fibre optic layers, and high power leds can be included to increase illumination intensity as appropriate. Fibre optics are typically applied on top of the metal domes, and directly below the overlay or silicone rubber key pad to achieve maximum illumination. The increase in force needed to close a membrane switch is minimal (5 to 25 grams), and the life of the membrane switch is not affected for most applications. (rated life to one million cycles in most circumstances).