UV cameras are a style of video camera that have been optimized for capturing light from the ultraviolet spectrum. This is accomplished by using a UV-pass filter, which will only allow light below the visible spectrum (wavelengths less than 400 nm). UV-A light, also called near ultraviolet, has a wavelength between 320—400 nm and is most relevant to UV photography. UV wavelengths let surfaces appear in greater clarity, and often depict features which are otherwise not apparent.
UV cameras operate in a fashion similar to CCD video cameras, with the main difference being that they record UV-A light. Regular CCD sensors are capable of recording UV light. UV-B light is absorbed by most lens materials, and UV-C light is absorbed by oxygen, making them mostly unimportant. While some video cameras may utilize a UV-cut filter to remove UV light from their recording, these types of cameras employ a UV-pass filter, isolating UV from other light spectrums. These filters are always made of glass, but also tend to allows large amounts of infrared light. Special filters and techniques (e.g. lighting, hot mirror filter) can be used to limit the IR contamination of UV images.
UV recording takes place via either reflected UV photography, or UV fluorescence photography. Reflected UV photography involves the direct illumination of subjects by UV sources, such as the sun. UV fluorescence technology involves the removal of visible light by filtering the light source. This ‘exciter’ filter should be used in conjunction with another UV-pass camera filter, and recording must be done in very dark environment.
The camera lens is one of the most critical factors in capturing UV light. To create a better illuminated subject by also capturing UV-B light, a special and expensive type of camera lens made of quartz or quartz-fluoride allows for the transmission of UV light in the 180—200 nm wavelengths. A less-expensive, but viable option would be to use older (pre-WWII), uncoated or single-coated camera lenses. These thinner lenses without optical polymers can satisfactorily transmit some low-wave UV light.
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