OPTICAL SYSTEM FOR IMAGING

摘要

PURPOSE: A photographing optical system is provided to reduce weight and lower costs as well as improve resolution. CONSTITUTION: A first lens(L1) has positive refractive power and is made of a plastic material. A second lens(L2) has negative refractive power and is made of the plastic material. A third lens(L3) has the positive refractive power and is made of the plastic material. A focal distance and a refractive index of an entire optical system satisfy a following conditional expression; 1.47<TL/f<1.71, Nd1-Nd2<0.08, and Nd1-Nd2<0.08(TL is a distance from an object side to an upper side of the first lens, F is a focal distance of an entire optical system, Nd1 is a refractive index at a d line of the first optic, and Nd2 is the refractive index at the d line of the second lens.).