Fast aspherical lens system

Abstract

A fast aspherical lens system is provided which includes a front lens group having a negative power, a diaphragm, and a rear lens group having a positive power, arranged in this order from the side of an object to be photographed. The rear lens group is provided with at least one lens having a diverging aspherical surface and satisfies the following conditions: -0.6<f/f.sub.F,<-0.2;tm (1) 3.0<.SIGMA.d.sub.F+S /f<8.0; (2) 3.0<.SIGMA.d.sub.R /f<6.0; (3) -0.9<.DELTA.I.sub.ASP <-0.1; (4) where f represents a focal length of the entire lens system, f.sub.F represents a focal length of the front lens group, .SIGMA.d.sub.F+S represents a sum of the thickness of the front lens group and a distance between the front lens group and the rear lens group, and .SIGMA.d.sub.r represents a thickness of the rear lens group, and .DELTA.I.sub.ASP represents an aberration factor of the aspherical surface term of the third-order spherical aberration factor of the aspherical lens.

Dependencies are inferred from the claim text.