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

FIELD: night-vision equipment. SUBSTANCE: device has two members. First member is designed as biconvex and biconcave lenses. Second member is designed as positive meniscus which convexity is directed to article, which first surface is non-spherical. Device conforms to conditions $$$, where $$$ are focal lengths of first and second lenses of first member, $$$ is focal length of device, $$$ is air gap between first and second members, $$$ is refraction index of lens of second member, $$$ are curvature radiuses of spherical surfaces of second lens of first member and second surface of lens of second member, $$$ is curvature radius at vertex of non-spherical lens of second member. EFFECT: increased functional capabilities. 3 dwg, 1 tbl