LARGE-APERTURE LENS Russian patent published in 2017 - IPC G02B13/14 G02B9/34 

FIELD: physics.

SUBSTANCE: lens consists of four components along the ray path. The first component is a single positive meniscus which concave side faces the image, the second component is a single negative meniscus which convex side faces the image, the third component is a single positive meniscus which convex side faces the image, and the fourth component is a single positive meniscus which concave surface faces the image. The first and fourth components are made of germanium, while the second and third components are made of zinc selenide. All optical surfaces are spherical. The following ratios are fulfiled: |R₅|>|R₆|, |R₅|≤|R₂|, |R₃|≥|R₈|, where R₂, R₃, R₅, R₆, R₈ - radii of the second, third, fifth, sixth and eighth optical surfaces, respectively. |R₃| may be greater or less than |R₆|.

EFFECT: increased aperture ratio with high image quality.

3 cl, 1 dwg, 3 tbl