FOUR-ELEMENT LENS Russian patent published in 2015 - IPC G02B9/12 G02B11/06 

FIELD: physics.

SUBSTANCE: lens consists of two components separated by an air gap. The first component on the beam path is glued from a biconvex and a biconcave lens, the second component consists, on the beam path, of a separate biconcave lens and a separate biconvex lens. The radii of the optical surfaces of the biconvex lens of the second component are equal in magnitude and the following relationships hold: 1.63<n₁=n₄<1.7; 1.7<n₂<1.9; where n₁, n₂, n₄ are refraction indices of the material on the beam path of the first, second and fourth lenses for the spectral line D.

EFFECT: high aperture ratio, larger field angle in the object space and high technological effectiveness.

1 dwg, 2 tbl