Hot and cold mirrors, also known as "heat control filters," are a type of dichroic filter designed to filter out excess energy emitted from a light source.

Notch Optics offers these heat control filters in thicknesses of 1.1 mm, 1.7 mm, and 3.3 mm, with sizes available up to 24 inches in diameter.

Hot Mirror

A hot mirror is a type of dichroic filter designed to reflect around 90% of near-infrared (NIR) and infrared (IR) light while allowing up to 80% of visible light to pass through.

It works by transmitting shorter wavelengths in the visible spectrum while reflecting the longer infrared wavelengths, helping control heat in optical systems. Hot mirrors are often engineered for specific angles of incidence, ranging from zero to 45 degrees.

They are manufactured by applying a multi-layer dielectric coating onto substrates like Borofloat® borosilicate glass, creating an effective and durable filter for high-performance optical applications.

Hot Mirror spectrum curve from Notch Optics

Cold Mirror

A cold mirror is a dichroic filter designed to reflect up to 90% of visible light while allowing up to 80% transmission of infrared (IR) and near-infrared (NIR) wavelengths.

This filter reflects shorter wavelengths in the visible spectrum while transmitting longer infrared wavelengths, effectively removing heat from the optical system. Cold mirrors can be specified for a range of incidence angles, typically from zero to 45 degrees.

They are produced by applying a multi-layer dielectric coating to substrates like Borofloat® borosilicate glass, ensuring durability and high optical performance.

Cold mirror spectrum curve from Notch Optics

Check out our article comparing hot mirrors and cold mirrors to learn more.