VARIABLE POWER OPTICAL SYSTEM, IMAGING LENS DEVICE AND DIGITAL APPARATUS

WIPO Patent Application WO/2007/049504

A2

A variable power optical system which keeps a lens production difficulty level at a conventional level while making it sufficiently compact. The variable power optical system comprises sequentially form an object side a first lens group having a negative optical power, and a second lens group having a positive optical power, the interval between the first and second lens groups being reduced at variable-powering from a wide-angle end to a telescopic end. The first lens group consists of a negative lens and a positive meniscus lens, and the second lens group consists of a biconvex positive lens and a negative meniscus lens. The following relations are satisfied when the thickness on the optical axis AX from the front-most surface of the first lens group to the rear-most surface of the first lens group is D1, a synthetic focal distance of the entire optical system at the wide-angle end of the variable power optical system is fw, and a synthetic focal distance of the second lens group is f2. 0.5