Ultrawide angle flat field eyepiece

A wide angle eyepiece comprising four lenses, I, II, III, and IV, and a field stop D located between lens III and lens IV, wherein lens II is a bi-convex lens, lenses I and III are meniscus lenses with the strongest curve of each adjacent lens II, and lens IV is a bi-concave lens, said lenses having parameters substantially as set forth in the following table wherein lens curvature, lens thicknesses, and lens separation distances are given in millimeters, n is the refractive index of a lens element, and v is the Abbe number for a lens element:

• __________________________________________________________________________ Axial Lens Thickness Separation Lens Radii "d" "l" n v __________________________________________________________________________ R1 = -45.7 d1 = 7.6 n1 = 1.6204 v1 = 60.3 LI R2 = -12.1 d2 = 0.9 n2 = 1.7174 v2 = 29.5 R3 = -23.7 l1 = 0.4 R4 = +64.6 d3 = 10.1 n3 = 1.6204 v3 = 60.3 LII R5 = -24.9 d4 = 0.9 n4 = 1.7174 v4 = 29.5 R6 = -43.4 l2 = 0.4 R7 = +26.1 d5 = 0.9 n5 = 1.7174 v5 = 29.5 LIII R8 = + 19.0 d6 = 10.9 n6 = 1.6204 v6 = 60.3 R9 = +82.3 l3 = 10.8 D l4 = 26.9 R10 = -20.8 d7 = 0.9 n7 = 1.6204 v7 = 60.3 LIV R11 = +16.4 d8 = 3.0 n8 = 1.6727 v8 = 32.2 R12 = +65.2 __________________________________________________________________________