ZOOM LENS

• Main Author: FUKAMI SEIJI
• Format: Patent
• Language: English
• Published: 26.01.2001
• Edition: 7
• Subjects: OPTICAL ELEMENTS, SYSTEMS, OR APPARATUS; OPTICS; PHYSICS

PROBLEM TO BE SOLVED: To realize a wider viewing angle, the shorter distance of a close range object and higher variable power and to miniaturize an entire lens system while adopting an inner focus by making a 1st group have specified constitution in a four-group zoom lens. SOLUTION: The 1st group F is a focus group having positive refractive power, and is provided with a 11th group F11 fixed at the time of focusing and having negative refractive power, a 12th group F12 having positive refractive power, provided with a positive lens and performing focusing by moving on an optical axis, and a 13th group F13 fixed at the time of focusing, having positive refractive power and provided with a negative lens in order from an object side. When the focal distances of the 11th to 13th groups are defined as f11 to f13, respectively, and the focal distance of the 1st group is defined as f1, they satisfy 1.2<=|f11/f1|<=1.7, 4.0<=f12/f15<=7.0 and 1.1<=f13/f15<=1.7. In a 2nd group V, image-formation magnification is changed in an area including -1 power in the case of variable power from a wide-angle end to a telephoto end. A 3rd group C corrects the fluctuation of an image surface associated with the variable power. A 4th group R is a relay group and has image- formation action.