Compact zoom lens

Abstract

Abstract PURPOSE:To obtain a 3-4 time zoom lens having 1.6-1.8 F-number, which is small-sized, light and inexpensive, by satisfying the prescribed conditions, in a lens system cosisting of 4 groups and 13 pieces of positive, negative, positive; negative, negative, positive; negative; positive, positive, positive, negative, positive and positive, in order from an object side. CONSTITUTION:In a lens system consisting of 4 groups and 13 pieces of positive, negative, positive; negative, negative, positive; negative; positve, positive, positive, negative, positive and positive, in order from an object side, the first and the second lenses are combined lenses, refractive power of each group is positive, negative, negative and positive in order, the first - the third groups are movable, and the conditions of the inequalities (1)-(7) are satisfied. Provided that fW, fI and fII, nu7, N7, fP, f11, fB, and DS denote the shortest focal distance of the whole system, focal distances of the first and the second groups, Abbe number of the seventh group, a refractive index of the seventh lens, a composite focal distance of the eighth - the tenth lenses, a focal distance of the eleventh lens, a back focus, and the diameter of an image circle, respectively. In this way, it is possible to obtain a 3-4 time zoome lens having 1.6-1.8 F-number, which is small-sized, light and inexpensive.

Inventors

• 👤 Satoru Tachihara
• 👤 立原　悟

Bibliographic Details