Does an infrared camera lens have a low emissivity?

• A. Yes
• B. No
• C. Sometimes
• D. Unknown

Answer: (A)

Emissivity describes how much infrared energy a surface emits relative to a perfect blackbody, and in infrared thermography you don’t want the optics to contribute their own radiation to the image. An IR camera lens is made from materials and coatings that are highly transparent in the infrared while itself radiating very little, so its emissivity is kept low. This minimizes self-emission from the lens and reduces stray radiation that could bias the detected signal, helping the camera accurately capture the scene’s true thermal content. If the lens emitted a lot of infrared, especially as it warmed, it would add noise and skew measurements. So the statement is true: the infrared camera lens has a low emissivity. The other options aren’t as accurate because lens designers strive for minimal self-emission, and the property isn’t something you’d typically describe as variable or unknown under normal operation.