Heat control filters

From Andover

A combination of hot and cold mirrors can essentially eliminate 99% of the radiation generated by high-power illumination systems. The cold mirror, mounted at a 45° angle of incidence, transmits much of the heat while reflecting the visible light. The hot mirror, mounted perpendicular to the light beam, reflects the remaining heat while transmitting 90% of the visible light.

Cold mirrors transmit near-IR and reflect visible light
Hot mirrors reflect near-IR and transmit visible light
Together, they effectively cool high-power illumination systems
General Specification
Thickness3.0±0.5 mm (6.0±0.5 mm for IR Suppressing)
Size Tolerance+0.0/-0.5 mm
Min. Clear Aperture95% of outside dimension
Substrate MaterialBorosilicate glass
Flatness5-10 waves per 25 mm
Parallelism3 arc minutes or better
Surface Quality80/50 per MIL-O-13830
Humidity and AbrasionPer MIL-C-675A
Max. Operating Temperature+200 °C
(+100 °C for IR suppressing)
OptionalMounted in threaded ring - contact our expert on the right for thread sizes

All filters are available in 12.5, 25.0, 50.0 mm Ø and 50.0 mm SQ.

Filter TypePart NumberTransmission Curve
Hot Mirrors
Hot mirrors are heat-reflecting filters designed to transmit visible wavelengths and reflect near-infrared heat-generating wavelengths. Andover's hot mirrors have hard, first-surface dielectric coatings that meet or exceed the humidity and abrasion specifications listed above. The coatings are deposited onto a low-expansion material such as borosilicate glass to prevent cracking or crazing from high heat applications775FW82
Ultraviolet Cold Mirrors
Ultraviolet mirrors differ slightly from the standard cold mirror in that they reflect the ultraviolet and transmit the visible and infrared. They are excellent for applications that call for separating the ultraviolet from the visible and near infrared.375FV86
Cold Mirrors
Cold mirrors are heat-transmitting filters designed to reflect visible wavelengths and transmit near-infrared wavelengths. Andover’s cold mirrors have first-surface coatings that are deposited onto a low-expansion material such as borosilicate glass. 645FK84
850 nm Cold Mirrors
This version of the cold mirror is identical to the standard cold mirror, but with the reflection range extended to 850nm. It has excellent transmission throughout the NIR region.850FK84
Infrared Suppressing Filters
These filters extend the blocking of standard hot mirrors across the infrared range using a combination of reflection from the dielectric stack and absorption from an infrared-absorbing filter glass. Because of this absorption factor, these filters are suitable only in low-power applications with a maximum filter temperature of 100°C.800FB72
Surgical and dental
Scientific instruments

Film and photographic apparatus

Illumination systems
Projection Systems
Film and Photographic Apparatus


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