HIGH-APERTURE LENS WITH ANGULAR FIELD OF NOT LESS THAN 25 DEGREES FOR THERMAL IMAGER (VERSIONS) Russian patent published in 2013 - IPC G02B9/38 G02B11/22 G02B13/14 

FIELD: physics.

SUBSTANCE: lens can be used in thermal imagers based on non-cooled matrix photodetector devices in the spectral range from 8 mcm to 12 mcm. The lens has four menisci, the first being a positive meniscus whose concave surface faces the image plane, the second being a negative meniscus, the third being a negative meniscus and the fourth being a positive meniscus whose concave surface faces the image plane. Optical power values of the menisci satisfy relationships given in the claim. In the lens according to the first version, the second meniscus faces the image plane by its concave surface and the third meniscus faces the image plane with its convex surface. The first and fourth menisci are made from germanium and the second and third menisci are made from material with refraction index of at least 2.2. In the lens according to the second version, the second meniscus faces the object space by its concave surface and the third meniscus faces the image plane by its concave surface. The first, second and fourth menisci are made from material with refraction index of 4.0. The refraction index of the material of the third meniscus is not greater than 2.5.

EFFECT: wider operating spectral range, reduced lens diameter, axial length and weight, high thermal stability of the focal distance while maintaining an aperture ratio of 1:1 and an angular field of not less than 25 degrees, ensuring high energy concentration in the aberration image with size of 0,025 mm or less in the entire field.

4 cl, 19 dwg, 2 tbl