ATHERMALISED LENS FOR INFRARED SPECTRAL REGION Russian patent published in 2015 - IPC G02B9/38 G02B11/22 G02B13/14 

FIELD: physics.

SUBSTANCE: lens comprises a first positive meniscus made of oxygen-free glass IKS-25, whose concave surface faces the image plane, a second negative meniscus made of zinc selenide, whose concave surface faces the image plane, a third negative and a fourth positive menisci made of germanium, whose concave surfaces face the image plane. The following relationships are satisfied: φ₁:φ₂:φ₃:φ₄=(0.72-0.85):-(1.28-1.76):-(3.00-6.00):(0.79-0.92), where φ₁, φ₂, φ₃, φ₄ denote relative optical power of the first, second, third and fourth menisci, respectively.

EFFECT: high image contrast on the entire field of vision in a wide temperature range.

2 cl, 3 dwg, 3 tbl