ATHERMALISED LENS FOR IR SPECTRUM AREA Russian patent published in 2017 - IPC G02B13/14 G02B9/34 

FIELD: physics.

SUBSTANCE: lens contains four components: three menisci and a biconvex lens. The first meniscus is positive, is made of germanium and faces the image plane with its concave surface, its second surface is made aspherical with an asphericity coefficient of K=0.2÷0.4. The second meniscus is positive and faces the image plane with its concave surface. The third meniscus is negative, made of zinc selenide and faces the image plane with its concave surface. The second meniscus and the lens are made of oxygen-free glass IRS-25 or chalcogenide glass IRG-26. The following relations are performed: ϕ₁:ϕ₂:ϕ₃:ϕ₄=(0.005÷0.06):(1.2÷2.0):-(1,2÷2.2):(0.9÷1.7), where ϕ₁, ϕ₂, ϕ₃, ϕ₄ - the relative optical forces of the first, the second, the third and the fourth components, respectively.

EFFECT: increasing the field of view, increasing transmission, simplifying the design, expanding the operation temperature range.

2 cl, 3 dwg, 5 tbl