US Patent 7178926 Illumination device for use in daylight conditions

An illumination device for use in daylight conditions includes a light-diffusing member provided with one or more dyes and a light source extending along and positioned adjacent a light-receiving surface of the light-diffusing member, with the light source emitting light that is substantially unabsorbed by the dyes as it passes through the light-diffusing member. Accordingly, in daylight conditions, the dyes are activated by sunlight to emit light such that light perceived along a light-emitting surface of the light-diffusing member is a combination of light from said light source and light from the dyes, thus increasing the output of the illumination device in daylight conditions.