Zoom lens system having high zoom ratio ranging to wide field angle

US5105311A · kind A · utility

Assignee

• Minolta Camera Kabushiki Kaisha · JP

Inventors

• Hisashi Tokumaru · Osaka, JP
• Mitsuko Date · Sakai, JP

Key dates

• Filing date: Aug 28, 1990
• Grant date: Apr 14, 1992
• Expiry date: Aug 28, 2010

Classification

• Technology area (CPC G): Physics
• CPC primary: G02B15/144105
• WIPO field: Optics
• WIPO sector: Instruments

Abstract

A compact size zoom lens system ranging to a wide field angle and having a high zoom ratio of up to 10. The zone lens system is composed of, from the object to the image side, a positive first lens group, a negative second lens group, a positive third lens group and a negative fourth lens group, and fulfills the following conditions: EQU 0.15<f.sub.s /f.sub.1 <0.3 EQU 0.45<f.sub.L /f.sub.s .multidot..vertline.f.sub.2 .vertline.)<0.8 EQU 0.15<f.sub.3 /f.sub.1 <0.32 where f.sub.1, f.sub.2, and f.sub.3 are the focal lengths of the first, second and third lens groups respectively, and f.sub.s and f.sub.L are respectively the shortest and the longest focal lengths of the zoom lens system. When the zoom lens is zoomed from wide to tele, the first lens group moves toward the object side, the distance between the second and third lens groups is decreased, and both the second and third lens groups are moved toward the object side. The following conditions may be added: EQU 0.35<f.sub.1 /f.sub.L <0.4 EQU 1.2<.vertline.f.sub.4 .vertline./.vertline.f.sub.2 .vertline.<4.8 for defining the refractive power of the fourth lens group. The third lens group may be divided into two lens groups that fl…