Principles of UV Detection

Apart from a few applications, such as UV disinfection and lacquer hardening, the intensity of UV radiation is well below that of visible light in ambient daylight or indoor lighting. A UV sensor must therefore be insensitive to visible light, otherwise the detection signal would easily be drowned out by the visible fraction of the radiation spectrum. Sensors that fulfill this requirement have a selective spectral sensitivity in the UV range. There are two important selectivities, known as visible-blindness and solar-blindness. 

A visible-blind UV sensor detects radiation only below A = 400 nm and thus is sensitive to the UV radiation of sunlight A solar-blind sensor does not react to sunlight and usually detects radiation below A = 300 nm. An outside fire alarm sensor imposes one of the most stringent requirements for solar-blindness. It must be sensitive to 100 pW/cm2 or less between 220 nm and 300 nm but should not react to direct sunlight that gives 100 mW/cm2 between 320 nm and 720 nm. 

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