ATHERMALIZED LENS FOR IR SPECTRUM Russian patent published in 2019 - IPC G02B13/14 G02B9/14 

FIELD: instrument making; optics.

SUBSTANCE: invention is designed to work with an uncooled matrix receiver and can be used as a lens for a thermal imager. Lens consists of a positive meniscus facing a concave surface towards the image plane, a negative meniscus facing a concave surface towards the plane of objects, positive meniscus facing a concave surface to the plane of objects, positive meniscus facing a convex surface to the plane of objects. First, third and fourth lenses are made of oxygen-free glass IKS-25, and the second lens is made of zinc selenide. Ratios are observed: φ1:φ2:φ3:φ4=(0.3÷0.7):-(1.3÷1.7):(0.80÷1.2):(0.80÷1.2), D2/f'=0.6÷0.8, where φ1, φ2, φ3, φ4 – relative optical powers of the first, second, third, and fourth components, respectively, D2 is the air gap between the first and second components; f' – equivalent focal length of the lens.

EFFECT: increasing the lens aperture and manufacturability, reducing the range of materials used while maintaining athermalization, the magnitude of the angular field and image quality.

1 cl, 2 dwg, 1 tbl