ATHERMALISED LENS FOR INFRARED SPECTRUM Russian patent published in 2016 - IPC G02B13/14 G02B9/34 

FIELD: optics.

SUBSTANCE: invention relates to infrared optics and can be used in thermal imagers with matrix photodetectors, which do not require cooling to cryogenic temperatures which are sensitive in spectral range of 8-12 mcm. Lens comprises a first negative meniscus, whose concave surface faces image plane, made of germanium, a second positive meniscus whose concave surface faces image plane, made from oxygen-free glass IKS-25, a third negative meniscus, whose concave surface faces image plane, made from zinc selenide or zinc sulphate, and a fourth positive meniscus whose concave surface faces image plane, made of germanium. First surface of first meniscus is coated with diamond-like antireflection coating. Following relationships are satisfied: φ₁:φ₂:φ₃:φ₄=-(0.11÷0.23):(1.44÷1.70):-(0.68÷0.92):(1.04÷1.21), where φ₁, φ₂, φ₃, φ₄ denote relative optical power of first, second, third and fourth menisci.

EFFECT: technical result is providing resistance of lens to effect of external conditions (temperature, humidity), which enables to use lens without additional protective glass.

1 cl, 3 dwg, 3 tbl