WIDE-ANGLE OCULAR Russian patent published in 1998 - IPC

FIELD: night-viewing devices. SUBSTANCE: ocular has two similar bi- convex lenses; first surface of first lens and second one of second lens are non-spherical while spherical surfaces of lenses are facing each other. Desired surfaces are calculated from following equations: , where R₁,R₄ are curvature radii at tops of non-spherical surfaces found from equation y²+z²+A₁x+A₂x²+A₃x³+A₄x⁴+A₅x⁵= 0; A₁,A₂,A₃,A₄,A₅ are factors used in non-spherical surface equation; R₂.R₃ are curvature radii of spherical surfaces (second surface of first lens and first surface of second lens); Δx_max1, Δx_max2 are maximal deviations of spheres of larger radius along axis X for first surface of first lens and for second surface of second lens; fТ is focal distance of ocular; n₁,n₂ are refractive indices of first and second lenses; t is exit pupil drift. Lenses may be made of polymeric material. Exit pupil drift tТ > fТ and angular field in space is larger than 50 deg. EFFECT: improved exit pupil drift with good characteristics of image over field; enlarged angular field in space. 2 cl, 3 dwg