LARGE-APERTURE LENS Russian patent published in 2011 - IPC G02B9/16 G02B13/14 

FIELD: physics.

SUBSTANCE: lens consists of three components lying on the beam path. The first component is a positive meniscus made from germanium and the second is a negative meniscus made from zinc selenide, whose concave surface faces the image. The third component is a positive meniscus whose convex surface faces the object. The concave surface of the first component is aspherical. The third component is made from zinc selenide and has refraction index greater than 2.3 and less than 4.1 for wavelength of 10 mcm. Radii of the curvature of the first, third, fourth, fifth and sixth surfaces and the focal distance of the lens are linked by expressions given in the claim.

EFFECT: higher aperture ratio with high image quality.

3 cl, 2 dwg, 3 tbl