Corrected three-group guide angle objective lens - has seven lens members, specified for compactness, F3.5 aperture and 76 deg. acceptance angle

摘要

The wide-angle objective lens is of a reverse teleobjective type and has a negative front lens group consisting of a positive lens (L1), with low refractive power, and a forward convex (r3) meniscus (L2), a thick positive intermediate group (L3,4), and a positive rear group of a forwardly convex (r9) meniscus (L5), a biconcave (L6) and a biconvex (L7) lens. The intermediate group consists of a thick (d3) biconvex (L3) and a forwards concave (r7) negative meniscus lens (L4) with negative air lens (t3) between them. Limits are specified for certain parameters, as are the curvature radii (r), lens thicknesses (d) and air gaps (t), refractive indices and Abbe-numbers for three examples referred to f=100 with f/3.5 aperture and 76 deg. acceptance angle, for which aberration curves are given. PS.