| 摘要 |
816,898. Lens systems. ISCO OPTISCHE WERKE G.m.b.H. Sept. 17, 1957 [Nov. 10, 1956], No. 29206/57. Class 97(1) An asymmetrical wide-angle objective of back focal length greater than the equivalent focal length f comprises a rear system II of positive power separated by an air gap greater than f from a front system I consisting of two negative components of which the front one is a simple lens and the rear one a doublet made up of a front positive lens and a rear negative lens, the cemented surface of the doublet being concave to the front and the refractive index difference across this surface being more than 0.15. The air gap d between the components of system I lies between 0.6f and 0.75f and the air gap d, between the simple front lens and the following negative doublet of system II lies between 0.14f and 0.18f. The refractive index difference across the cemented surface r 9 of this doublet is preferably more than 0.25. The drawing shows one example for which optical data are given in the Specification.
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