ATHERMALISED LENS FOR INFRARED SPECTRUM Russian patent published in 2017 - IPC G02B13/14 G02B9/38 G02B9/56 

FIELD: electronics.

SUBSTANCE: lens can be used in thermal imagers for spectral region of 8–12 µm. Lens has four components, first of which is a positive meniscus made of oxygen-free glass IKS-25, second one is a negative meniscus made of zinc selenide, third one is a negative meniscus made of germanium. Menisci concave surfaces face the image plane. Concave surface of the third meniscus is aspherical with a conic constant within the range of 0.32 to 0.46. Fourth component is a positive lens made of germanium with a convex first surface, facing an object plane, and with a flat or concave second surface. Ratios are met: ϕ₁:ϕ₂:ϕ₃:ϕ₄=(1.44÷1.80):-(0.8÷1.18):-(0.62÷1.00):(1.38÷1.56), D4/f'=0.16÷0.31, D6/f'=0.22÷0.40, where ϕ₁, ϕ₂, ϕ₃, ϕ₄ – relative optical power of the first, second, third and fourth components, respectively, D4, D6 – air gaps between the second and third and between the third and fourth components, respectively; f' – equivalent focal distance of the lens.

EFFECT: technical result – increased field of vision and aperture ratio, reduced length of the lens.

1 cl, 4 tbl, 3 dwg