HIGH-APERTURE LENS Russian patent published in 2016 - IPC G02B9/16 G02B11/08 

FIELD: physics.

SUBSTANCE: lens comprises three lenses. The first lens is a positive meniscus lens whose concave side faces the image. The second lens is negative, and the curvature radius of its first surface r₃ satisfies the relationship . The third lens is a positive meniscus whose concave side faces the image, for which the relationship is satisfied, where: f' is the focal distance of the lens, n is the refraction index of the material of the third lens, r₅ is the curvature radius of the first surface of the third lens, r₆ is the curvature radius of the second surface of the third lens, d₅ is thickness on the axis of the third lens. The distance between the first and second lenses is greater than 0.15f'.

EFFECT: high image quality for the middle and far infrared ranges.

7 cl, 1 dwg, 16 tbl