1. Field of the Invention
The invention is directed to an apparatus and method for generating visible light and, more particularly, to an apparatus and method for generating visible light using an ultraviolet laser, or similar UV light source.
2. Related Art
Light generating sources today, such as flashlights or general light bulbs, for example, use traditional techniques for generating light that might involve an incandescent bulb or in newer versions, compact fluorescents, light emitting diodes (LEDs) and the like. These approaches have several limitations. For example, the power requirement may be relatively high and the bulbs or diodes may have a relatively short life expectation due to being damaged in normal use, or by burn-out. Furthermore, some may have complicated structures and use dangerous chemicals such as compact fluorescents. Moreover, the amount of lumens produced may be relatively limited.
By far the most common application of fluorescence in daily life is in the fluorescent light bulb, of which there are more than 1.5 billion operating in the United States. Fluorescent light stands in contrast to incandescent, or heat-producing, electrical light. First developed successfully by Thomas Edison (1847-1931) in 1879, the incandescent lamp quite literally transformed human life, making possible a degree of activity after dark that would have been impractical in the age of gas lamps. Yet, incandescent lighting is highly inefficient compared to fluorescent light: in an incandescent bulb, fully 90% of the energy output is wasted on heat, which comes through the infrared region.
A fluorescent bulb consuming the same amount of power as an incandescent bulb will produce about three to five times more light, and it does this by using a phosphor, a chemical that glows when exposed to electromagnetic energy. (The term “phosphor” should not be confused with phosphorescence: phosphors are used in both fluorescent and phosphorescent applications.) The phosphor, which typically coats the inside surface of a fluorescent lamp, absorbs ultraviolet light emitted by excited mercury atoms. It then re-emits the ultraviolet light, but at longer wave-lengths, as visible light. Thanks to the phosphor, a fluorescent lamp gives off much more light than an incandescent one, and does so without producing much heat.
Accordingly, alternative techniques for efficiently producing reliable, safe and bright visible light cost effectively would be a welcomed advancement in the light producing industry.