Sensors are necessary for the security management, function and quality controls and environmental management. Generally infrared LEDs more than 750nm wavelength are used for such sensing purpose. They are also employed in the ordinary use such as remote controls for home appliance. As well as infrared light, invisible UV light is used for sensing applications such as the detection of the invisible material.
By Illuminating UV light on banknotes, the reflection from the banknotes and the ink used can tell if they are counterfeit or not. UV lamps are conventionally used for the detection of counterfeit banknotes. However since compact and high efficiency UV LEDs are introduced to the market, it is rapidly proceed to replace UV lamps to UV LEDs. UV LEDs are also used as light source for other sensing applications such as image processing and chemical sensing in the biological and medical fields.