VARIABLE POWER OPTICAL SYSTEM, IMAGING APPARATUS AND DIGITAL EQUIPMENT

摘要

PROBLEM TO BE SOLVED: To provide a variable power optical system capable of suppressing required accuracy of aspherical shape to be low while securing a large aperture ratio, optical performance and compactness equal to or above the conventional one, and an imaging apparatus and digital equipment. SOLUTION: The variable power optical system is equipped with a first lens group 11 having negative optical power, a diaphragm 13 and a second lens group 12 having positive optical power in order from an object side. When varying power from a wide angle end to a telephoto end, the first lens group 11 and the second lens group 12 move so that space between them may be narrow, and the diaphragm 13 is fixed. The second lens group 12 is equipped with a first positive lens 121, a second negative lens 122, a third positive lens 123 and a fourth lens 124 having at least one aspherical surface in order from the object side. The variable power ratio Z, an F-number Fnw at the wide angle end, the focal length ft of the entire system at the telephoto and the focal length fL24 of the fourth lens 124 satisfy respective conditions 0.62)<4.0 and -0.4