A hot mirror is a dichroic, heat-reflecting optic, which filters out the heat energy from a light source. This is done by reflecting back the infrared energy and by transmitting the visible spectrum at the same time. It is based on the opposite function principle of a cold-mirror. Since a hot mirror reflects infrared light and because it filters the infrared wavelengths out of the beam path like a filter, it can be referred to as "heat reflecting filter" as well as a "heat reflecting mirror". Both terms are correct.
Our SIR hot mirrors offer a decisive advantage over ordinary heat- reflecting coatings or absorbing filters. Their optical transmission of visible light is higher and more neutral in color, while the thermal radiation in the near infrared up to 1100 nm is reflected significantly more efficiently.
Because of its 100 % dielectric coating design and the use of temperature-resistant quality BOROFLOAT® substrates, the SIR hot mirror withstands a high thermal load. The filters can be used at operating temperatures of up to 400 °C, which allows the use in lighting systems. Furthermore, the SIR hot mirror does not get as hot as absorbing filters, because the warm infrared radiation is deflected back instead of being absorbed.
But there are also purely optical applications for our SIR mirrors. For example, the SIR can be used as a detector trimmer in front of a digital camera chip. This prevents the image sensor from saturation, caused by near infrared light, for which many CCD camera sensors are very sensitive.
The non-metallic coating design makes the SIR resistant to thermal load and humidity. The filter coating is optimized for maximum possible transmittance of visible light and at the same time for maximum achievable reflectivity in the NIR-range. The angle of incidence the SIR hot mirror was designed for is 0°. However, if a slight shifting of the cut-off wavelength is acceptable, already our standard SIR can also be used at 45°. Most of the visible spectrum is still transmitted at this angle and the reflected IR-image keeps a good imaging quality when the SIR hot mirror is used as a 45-IR-mirror. Hence, the SIR could often be used for eye-tracking systems or as IR-laser injection optics without modification. If you want to utilize our SIR filters at other incidence angles than 0°, please contact us by email or simply use our support form to get further information. Typical transmission curves of our hot mirror when operated at 45° or at other angles of incidences can be obtained on request.
All of our heat reflecting coatings can be modified in regards to transmittance and reflection wavelength ranges. Same applies to the cut-on and cut-off filter-wavelength and for the angles of incidences. Please use our custom optics inquiry form, to conveniently request for a quote for custom coated hot mirrors. You are invited to contact us by email for help, further information and details.
To receive a quotation for our SIR hot mirrors with individual dimensions, please click the button below:
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View spectral transmission curve of our SIR hot mirror
Note: If you are looking for a coating with reverse functional characteristic, please take look at our cold mirror web site.
All given details and specifications are mean reference values and are not guaranteed. In addition, please consider our "Notes on technical specifications"