The shift from monochrome to color displays in handheld and portable equipment has opened the market for white LEDs as small, affordable, broad-spectrum illumination sources. The affordability is a recent phenomenon, which, along with improved driver ICs and waveguide designs, has fueled the uptake rate of white LEDs, particularly in cell phones and PDAs, as recent sales trends in Japan and Europe show. Battery-operated equipment that incorporates an LCD must provide an illumination source for good readability under most operating conditions. A color LCD requires a broad-spectrum illumination source. Candidates include CCFLs (cold-cathode fluorescent lamps), ELs (electroluminescent lamps), and white LEDs (see sidebar "Illuminating alternatives").
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