A hot mirror is a heat filter that is used to remove undesired infrared energy from a light source. It reflects infrared wavelengths while it is transparent in the visible spectrum, which is the opposite way a cold mirror works. Our SIR heat filter shows a decisive advantage over ordinary hot mirror coatings or heat absorbing filters. The transmission of visible light is higher and more neutral in color, while the thermal radiation up to 1100nm (near infrared light) is reflected significantly more efficiently. Because of its 100% dielectric construction and the temperature-resistant quality BOROFLOAT® substrate, the SIR hot mirror can withstand a high thermal load. The filter can be used at operating temperatures of up to 400°C.
Furthermore, our heat reflecting hot mirror does not warm up as strong as heat absorbing filters do, because the warm infrared radiation is deflected instead of being absorbed. But there are also applications for our SIR filters that don't have much thermal energy to be removed. For example our SIR filters are often used in front of digital camera chips to prevent image sensor saturation caused by the near infrared light for which many digital camera sensors are very sensitive.
The non-metallic filter coating design makes the SIR hot mirror resistant to humidity and many other environmental conditions. The SIR filters are designed for maximum transmission of visible light at an angle of incidence of 0°. Nevertheless, if a shifting of the cut-off is acceptable, even our standard SIR mirrors can be used at incidence angles of 45° while still transmitting most of the visible light spectrum. Hence the SIR hot mirrors can often be used in eye-tracking applications without a modification. If you want to use our SIR filters at other angles than 0°, please ask us for support, further information or typical transmittance curves.
All of our heat reflecting mirror coatings can be modified in regards to transmittance and reflection wavelength ranges, as well as to the cut-on and cut-off filter wavelength and angles of incidences. Please use our custom optics RFQ for to conveniently inquire your customized hot mirror or just contact us for further information and details.
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