Hot mirror
Encyclopedia
A hot mirror is a specialized dielectric mirror
, a dichroic filter
, often employed to protect optical systems by reflecting infrared light back into a light source, while allowing visible light to pass. Hot mirrors can be designed to be inserted into the optical system at an incidence angle varying between zero and 45 degrees, and are useful in a variety of applications where heat build-up can damage components or adversely affect spectral characteristics of the illumination source. Wavelength
s reflected by an infrared hot mirror range from about 750 to 1250 nanometers. By transmitting visible light wavelengths while reflecting infrared, hot mirrors can also serve as dichromatic beam splitter
s for specialized applications in fluorescence microscopy.
Some early digital cameras designed for visible light capture, such as the Associated Press NC2000
and Nikon Coolpix 950
, were unusually sensitive to infrared radiation, and tended to produce colours 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. Conversely, these cameras could be used for infrared photography
by inserting a cold mirror
filter into the imaging pathway, most commonly by mounting the filter on the front of the lens.
New incandescent bulbs
incorporate hot mirrors, increasing efficiency by redirecting unwanted infrared
frequencies back to the filament.
Dielectric mirror
A dielectric mirror is a type of a mirror composed of multiple thin layers of dielectric material, typically deposited on a substrate of glass or some other optical material. By careful choice of the type and thickness of the dielectric layers, one can design an optical coating with specified...
, a dichroic filter
Dichroic filter
A dichroic filter, thin-film filter, or interference filter is a very accurate color filter used to selectively pass light of a small range of colors while reflecting other colors. By comparison, dichroic mirrors and dichroic reflectors tend to be characterized by the color of light that they...
, often employed to protect optical systems by reflecting infrared light back into a light source, while allowing visible light to pass. Hot mirrors can be designed to be inserted into the optical system at an incidence angle varying between zero and 45 degrees, and are useful in a variety of applications where heat build-up can damage components or adversely affect spectral characteristics of the illumination source. Wavelength
Wavelength
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...
s reflected by an infrared hot mirror range from about 750 to 1250 nanometers. By transmitting visible light wavelengths while reflecting infrared, hot mirrors can also serve as dichromatic beam splitter
Beam splitter
A beam splitter is an optical device that splits a beam of light in two. It is the crucial part of most interferometers.In its most common form, a rectangle, it is made from two triangular glass prisms which are glued together at their base using Canada balsam...
s for specialized applications in fluorescence microscopy.
Some early digital cameras designed for visible light capture, such as the Associated Press NC2000
Kodak DCS 400 series
The Kodak DCS 400 series was a series of Nikon based digital SLR cameras with sensor and added electronics produced by Eastman Kodak.The cameras in this series include the 1.5-megapixel DCS 420 , the 1.5-mpx DCS 410 , and the 6.2-mpx DCS 460...
and Nikon Coolpix 950
Nikon Coolpix 950
The Nikon Coolpix 950 was a digital camera released by Nikon in early 1999. The 950 model superseded the Coolpix 900 in the Nikon Coolpix series. The Coolpix 950 was a durable camera with swivel lens, magnesium body, a maximum resolution of 1600×1200 , 3× optical zoom and a minimum...
, were unusually sensitive to infrared radiation, and tended to produce colours 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. Conversely, these cameras could be used for infrared photography
Infrared photography
In infrared photography, the film or image sensor used is sensitive to infrared light. The part of the spectrum used is referred to as near-infrared to distinguish it from far-infrared, which is the domain of thermal imaging. Wavelengths used for photography range from about 700 nm to about...
by inserting a cold mirror
Cold mirror
A cold mirror is a specialized dielectric mirror, a dichroic filter, that reflects the entire visible light spectrum while very efficiently transmitting infrared wavelengths. Similar to hot mirrors, cold mirrors can be designed for an incidence angle ranging between zero and 45 degrees, and are...
filter into the imaging pathway, most commonly by mounting the filter on the front of the lens.
New incandescent bulbs
Incandescent light bulb
The incandescent light bulb, incandescent lamp or incandescent light globe makes light by heating a metal filament wire to a high temperature until it glows. The hot filament is protected from air by a glass bulb that is filled with inert gas or evacuated. In a halogen lamp, a chemical process...
incorporate hot mirrors, increasing efficiency by redirecting unwanted infrared
Waste heat
Waste heat sometimes called Secondary heat or Low-grade heat refers to heat produced by machines, electrical equipment and industrial processes for which no useful application is found. Energy is often produced by a heat engine, running on a source of high-temperature heat...
frequencies back to the filament.