WIDE-APERTURE LENS FOR NEAR INFRARED LIGHT Russian patent published in 1998 - IPC

FIELD: night-vision equipment. SUBSTANCE: device has four members. First member is designed as convex-flat lens. Second member is designed as positive meniscus which convexity is directed to article. Third member is designed as flat-concave lens. Fourth member is designed as biconvex lens. Device conforms to conditions $$$, where $$$ is focal length of first and second members, $$$ is focal length of first, second and third members, $$$ are thickness values and air gaps in device, $$$ are curvature radiuses of second member, $$$ is focal length of fourth , $$$ is refraction index of lens of fourth member, $$$ is device focal length. EFFECT: increased functional capabilities. 3 dwg, 1 tbl