LENS FOR INFRARED SPECTRAL AREA Russian patent published in 2017 - IPC G02B13/14 G02B9/16 G02B13/18 

FIELD: physics.

SUBSTANCE: lens comprises 3 menisci. The first and the third menisci - positive, made of germanium. The second meniscus - negative, made of zinc selenide. All menisci face the image plane with their concave surfaces. The second surface of the first meniscus is an aspherical surface of the second order with a conic constant in the range of 0,2÷0,5. The second meniscus is moveable along the optical axis. The relations are performed:ϕ₁:ϕ₂:ϕ₃=(0,70÷0,90):-(0,10÷0,60):(1,0÷1,80), where ϕ₁:ϕ₂:ϕ₃ - the relative optical powers of, respectively, the first, the second and the third menisci; D2/f'=0,3÷0,7; D4/f'=0,2÷0,6, where D2 - the air gap between the first and the second menisci; f'- the focal length of the lens, D4 - the air gap between the second and the third menisci.

EFFECT: increasing the image quality in normal climatic conditions and ensuring the lens operation in the temperature range from minus 40 to 50 degrees without compromising the image quality.

3 dwg, 2 tbl