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A hot mirror is a dichroic, heat-reflection optic, which filters out the heat energy from a light beam. This is done by reflecting infrared light and simultaneously transmitting the visible spectrum. A hot mirror is based on the opposite function principle of a cold-mirror. Since it 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 reflection filter" as well as to "heat reflection mirror". Both terms are correct.
Our SIR hot mirrors offer a decisive advantage over ordinary heat-reflection 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 design and the use of temperature-resistant quality BOROFLOAT® substrates, the SIR hot mirror withstands a high thermal load. The filters can be operated at temperatures of up to 400 °C, which allows the use in lighting systems. Furthermore, the SIR hot mirror does not get as hot as heat absorbing filters, because the warm infrared radiation is reflected back instead of being absorbed.
But there are also purely optical applications for our SIR hot mirror. For example, the SIR can work as a detector trimmer in front of a digital camera chip. This prevents the optical 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 mirror resistant to thermal load and humidity. The optical 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 mirror can also be used at 45°. With this angle most of the visible spectrum is still transmitted and the reflected IR-image keeps a good optical imaging quality. Hence, the SIR mirror is often found in eye-tracking-systems or as IR-laser injection optics without modification and it should be taken into account that this can reduce cost compared to a customized optical coating drastically, especially if only small quantities are needed. If you want to utilize our SIR filters at other incidence angles than 0°, please contact us by email or simply open our support form to ask for further information. Typical optical 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 mirror coatings can be modified regarding transmittance and reflection wavelength ranges. Same applies to the optical 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:
View optical transmission curve of our SIR hot mirror
Note: If you are looking for an optical mirrors 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"