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1. (WO2014208367) ZOOM LENS SYSTEM

Pub. No.:    WO/2014/208367    International Application No.:    PCT/JP2014/065752
Publication Date: Thu Jan 01 00:59:59 CET 2015 International Filing Date: Sat Jun 14 01:59:59 CEST 2014
IPC: G02B 13/04
G02B 13/18
Applicants: RICOH IMAGING COMPANY, LTD.
リコーイメージング株式会社
Inventors: OHISHI, Takahiko
大石 崇彦
Title: ZOOM LENS SYSTEM
Abstract:
The present invention provides a lens system with two lens groups, negative and positive, which, while retaining the advantages of having a simple mechanical structure and being suited for cost reduction, is able to acquire sufficient brightness of a low F-number and also achieve superior optical performance by excellent correction for coma aberration, spherical aberration, astigmatism, distortion, and chromatic aberration. The zoom lens system is formed from, in order from the object side, a negative first lens group and a positive second lens group. When changing magnification from the wide angle end to the telephoto end, the gap between the first lens group and the second lens group is reduced. The second lens group is formed from, in order from the object side, a positive second A lens group, an aperture stop, and a positive second B lens group. The following conditional equation (1) is satisfied. (1) 0.65 < f2A/f2B < 1.0 Wherein, f2A: focal distance of second A lens group f2B: focal distance of second B lens group