Hot mirrors, which reflect heat energy, are quite effective in space-limited applications. Because the hot mirror is a short wavepass filter, attempts to extend the width of the reflecting band beyond about 1.2 µm usually result in a loss of visible transmission caused by high order interference effects. Although the heat rejection characteristics of a hot mirror are less than those of a cold mirror, hot mirrors may prove to be equally effective when they are matched properly to the spectral response of both the energy source and the optical system.
A hot mirror typically removes about 25% of the heat energy from a tungsten source operating at 3200 K, and a wide band hot mirror removes about 45%. The removal efficiency decreases for both of these coatings at the temperature of the light source is decreased.
Cold Mirror |
R > 94% average, 0.45 µm - 0.65 µm |
Hot Mirror |
T > 85% average, 0.45 µm - 0.65 µm |
Wide Band Hot Mirror |
T > 85% average, 0.45 µm - 0.675 µm |
Wide Band Cold Mirror |
R > 90% average, 0.35 µm - 0.65 µm |
When you need to separate heat from visual light, JDS Unniphase wide band hot mirrors are the industry standard in achieving maximum separation of the heat content (IR) from visual light.
Wide Band Hot Mirrors are used in systems where it is desirable to transmit a cool beam of visible light and remove heat (infrared light) by reflection rather than absorption.
Hot mirrors are typically used at normal angle of incidence to the light source. Separating the heat by reflection allows the thermal energy to be removed from the system and simplifies thermal design requirements.
This hard, all dielectric mirror is durable and stable when exposed to moderate temperatures, thermal shock, aging, repetitive handling, and cleaning.