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Ahot mirror is a specializeddielectric mirror, adichroic filter, often employed to protect optical systems by reflectinginfrared light back into a light source, while allowingvisible light to pass. Hot mirrors can be designed to be inserted into the optical system at anincidence angle varying between zero and 45 degrees, and are useful in a variety of applications where the buildup ofwaste heat can damage components or adversely affect spectral characteristics of the illumination source.Wavelengths reflected by an infrared hot mirror range from about 750 to 1250nanometers. By transmitting visible light wavelengths while reflecting infrared, hot mirrors can also serve as dichromaticbeam splitters for specialized applications influorescence microscopy or opticaleye tracking.
Some early digital cameras designed for visible light capture, such as theAssociated Press NC2000 andNikon Coolpix 950, were unusually sensitive to infrared radiation, and tended to produce colors that were contaminated with infrared. This was particularly problematic with scenes that contained strong sources of infrared, such as fires, although the effect could be moderated by inserting a photographic hot mirror filter into the imaging pathway.[1] Conversely, these cameras could be used forinfrared photography by inserting acold mirror filter, more commonly known as an infrared filter, into the imaging pathway, most commonly by mounting the filter on the front of the lens.[2]
Newincandescent bulbs incorporate hot mirrors,increasing efficiency by redirecting unwanted infrared frequencies back to the filament.[3][4][5]
