OBJECTIVE LENS FOR NIGHT VISION DEVICE Russian patent published in 2014 - IPC G02B9/60 G02B13/16 

FIELD: physics.

SUBSTANCE: objective lens has a first positive meniscus whose concave surface faces the second component, a second negative component consisting of a biconvex lens and concave lens glued to each other, a fourth biconvex lens, third and fifth negative menisci whose concave surfaces face the fourth lens. The distance between the first lens and the second component is not less than 0.3 times the focal length of the objective lens. All lenses are made of glass with coefficients of linear expansion in the range of (5-10)·10^-6 deg^-1. The operating temperature range ΔT average temperature change of the refraction index of the glass of the first lens and the biconvex lens of the second component is in the range of (-2-0)·10^-6 deg^-1 and in the range of (0-4)·10^-6 deg^-1 for the other lenses. Optical power ratios satisfy relationships given in the claim.

EFFECT: high aperture ratio and field angle, reduced weight while maintaining the diameter of the entrance pupil, providing thermal adjustability and high image quality in a wide operating temperature range without additional movements of the objective lens, components thereof or electro-optical converter.

5 dwg, 4 tbl