WIDE APERTURE LENS FOR NEAR INFRARED LIGHT Russian patent published in 1997 - IPC

FIELD: lenses for night vision spyglass. SUBSTANCE: lens have four components. First component is convexo-convex lens, second component is concavo-concave lens, third and fourth components are convexo-convex lenses, which conform to conditions , where n1 and n3 are refraction indices of first and third components, f′ is focal length of lens, are focal lengths of first and second components, r₁, r₂, r₃, r₄, r₅, r₆, r₇ are curvatures of first, second, third and fourth components. EFFECT: increased functional capabilities. 2 dwg , 1 tbl