SMALL AND LIGHTWEIGHT ZOOM LENS

• Main Author: NODA TAKAYUKI
• Format: Patent
• Language: English
• Published: 18.11.2004
• Edition: 7
• Subjects: OPTICAL ELEMENTS, SYSTEMS, OR APPARATUS; OPTICS; PHYSICS

PROBLEM TO BE SOLVED: To well correct various aberrations of a zoom lens of three-element configuration in three groups, positive-negative-positive while reducing the size, weight and cost of the zoom lens. SOLUTION: The small and lightweight zoom lens is formed by disposing, successively from an object side, a positive first lens group (L1), a negative second lens group (L2and diaphragm 3), and a positive third lens group (L3), changes the focal length of the entire system by moving the first lens group and the second lens group along the optical axis at the time of zooming and satisfies conditional expressions (1) to (3). Focusing is performed by the first lens group. Plastic lenses are employed for the lenses constituting at least the first lens group and the second lens group. The conditional expression (1): LTL<3.3, the conditional expression (2): 2.2<f1/f3<3.0, and the conditional expression (3): 0.55< ¾f2/f3¾<0.85, where LTL: the value obtained by dividing the maximum conjugation distance in the entire zoom region by the focal length at a wide angle end, fl: the focal length of the first lens group, f2: the focal length of the second lens group, and f3: the focal length of the third lens group. COPYRIGHT: (C)2005,JPO&NCIPI