1. US20130016278 - Imaging lens, imaging optical device, and digital equipment

An imaging lens system has, from an object side, at least one positive lens element convex to the object side, a negative lens element, and at least one lens element having an aspherical surface. The positive and negative lens elements are arranged next to each other. The formulae 0.1<Ton/Dopn<7, 0.1<(Rona−Ronb)/(Rona+Ronb)<1.5, and 0.3<Y′/TL<0.9 are fulfilled, where Ton represents the axial thickness of the most object-side negative lens element, Dopn represents the axial distance between the most object-side negative lens element and the positive lens element located to the object side of and next to that negative lens element, Rona represents the paraxial radius of curvature of the object-side surface of the most object-side negative lens element, Ronb represents the paraxial radius of curvature of the image-side surface of the most object-side negative lens element, Y′ represents the maximum image height, and TL represents the axial distance from the vertex of the most object-side lens surface to the image surface (in a case where a parallel-plane plate is included, the air equivalent length).