Lightweight large aperture objective - for cinematographic or TV cameras, has low aberations in visible and near IR and has seven lens elements

摘要

The lens of focal length F has a first group (R1-R5) including a converging plano-convex lens (R1-R2) and a convergent doublet lens (R3-R5) and the focal length of the group is between F and 1.25F. There is a biconcave divergent lens (R6, R7) whose focal length is between -0.75F and -0.9F, whose diameter is approx. equal to the mean of that of the first group of lense, at a distance between 0.3F and 0.4F from the first group. There is a biconvex converging lens (R8, R9) of focal length between 0.35F and 0.55F, whose diameter is less than the mean of that of the first group, and at a distance between 0.18F and 0.28F, from the divergent lens between -0.5F and -0.8F, at a distance between 0.15F and 0.25F from the converging lens.