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Hot Mirrors

Dielectric heat-reflection filters


Special Properties

  • High visible transmission
  • Efficient thermal energy blocking
  • Designed for an angle of incidence of 0°
  • Excellent infrared reflectivity up to 1100 nm
  • High color neutrality
  • Metal-free layer design
  • High operating temperature of up to 350 °C
    (with uniform heating)
  • Borosilicate glass substrate
  • High optical quality
  • Reverse operating principle of dichroic cold mirrors

Typical Applications

  • IR cut filters for CCD camera chips
  • Heat protection filters for light sources
  • IR-reflective optics in lighting systems
  • Mirrors for IR-laser diodes
  • Measurement and Sensor Technology
  • Lighting applications in the automotive industry
  • Detector trimmers
  • IR-reflector optics for eye-tracking systems
  • Laser injectors
  • Heat control in projectors

Related filter optics

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Hot mirrors reflect a significant portion of unwanted infrared radiation (IR) while transmitting most of the visible light spectrum. This selective dichroic reflection and transmission capability is achieved through carefully tailored optical coatings deposited on a glass substrate. By effectively reflecting the IR wavelengths and allowing visible light to pass through, hot mirrors prevent the excessive heating of target objects or sensitive components within optical systems. Hot mirrors work based on the opposite optical function principle of cold mirrors. Since they reflect infrared light and filter it out of the beam path, they are called hot mirrors, heat-reflecting filters, or heat-reflection mirrors. All these designations are correct and customary.

CNC-shaped SIR hot mirror

Our SIR offers a decisive advantage over most standard hot mirrors and heat-absorbing filters. It provides a higher and more color-neutral optical transmittance of visible light while reflecting thermal radiation significantly more efficiently in the near-infrared up to 1100 nm. The all-dielectric optical coating design and the thermally resistant BOROFLOAT® substrate glass of our SIR hot mirror enable it to withstand a high temperature of up to 350 °C, allowing its operation in high-energy lighting systems.

SIR hot mirrors are ideal for heat management in optical systems. They do not get as hot as filters based on absorption because they reflect the warm infrared radiation to the light source instead of absorbing it. This way, the thermal energy is blocked and reflected before entering the optical system.

In addition to the applications described above, there are also purely optical tasks for our SIR. For example, it is often used as a detector trimmer optic in front of digital camera chips to prevent image sensor saturation caused by near-infrared light. Many CCD camera sensors have high sensitivity in this spectral range.

The non-metallic construction makes the SIR resistant to heat and humidity. We optimized the SIR's thin film for the maximum possible visible light transmission and maximum reflection in the NIR range. We conceptualized the SIR for a light incidence of 0°. However, when a slight shifting of the cut-off wavelength is acceptable, our standard SIR can also operate at an angle of 45°. It still transmits most of the visible spectrum at this incidence, and the reflected IR image maintains good optical imaging quality. Hence, many customers successfully utilize our SIR mirrors for eye-tracking or IR laser beam-injection applications without modification. Using our standard hot mirrors in such cases can drastically reduce costs, especially if only small quantities are needed because no expensive customized coating is required. If you want to operate our SIR mirrors at an angle deviating from 0°, please inquire by email or via our support form to obtain further information. We are happy to provide the typical curves of our hot mirrors when used at 45° or other angles.

We can adapt our optical hot mirror coatings regarding transmittance and reflection ranges by adding or modifying coating layers. The same applies to the optics' optical cut-on and cut-off filter wavelengths. Please use our inquiry form for custom optics to request your individually designed optics conveniently.


Please choose a thickness from the thickness table or click the button below to receive a quotation for our standard SIR-hot mirrors with individual dimensions.


Request for Quotation

48h-Express Service for customized optics, logo 48-hour express service


SIR hot mirrors
transmittance spectrum for i = 0°

SIR, transmittance
Enlarge the curve to show details

Standard Thicknesses

Please click on a glass thickness to request a quote:

Thickness (mm)


48h-Express Service
1,10 ±0,10
1,75 ±0,20
3,30 ±0,20
Custom thicknesses are available on request
The thicknesses marked with "" are also possible within 48–hour express service.

Coating Construction

  • All-dielectric, multilayer filter coating
  • Designed for an angle of incidence of 0°
  • Customized cut-on and cut-off wavelengths per inquiry

Glass Substrate

Operating Temperature

  • up to 350 °C (with uniform heating)

Optical Flatness

  • Depending on the glass thickness
  • Defined flatness per inquiry

Surface Quality

  • Typ. 80-50 scratch & dig (MIL-0-13830A)
  • Other on request

Other Properties

  • Adherence according to MIL-C-675 C (tape test)
  • Abrasion-resistant according to MIL-M-13508 C

Note: If you are looking for optical mirrors with the reverse functional characteristics of a hot mirror, please visit our cold mirror website. See our SEA-NIR, SEA-UV, and ITO-coatings datasheets if your application needs IR reflective mirrors. Please visit our cold mirror website for optical mirrors with reverse functional characteristics.

Please refer to our SEA-NIR, SEA-UV, and ITO-coatings datasheets if your application requires an IR mirror.


All given details and specifications are mean reference values and are not guaranteed. Also, please consider our "Notes on technical specifications".

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Last update: 28.09.2023