| 摘要 |
<P>PROBLEM TO BE SOLVED: To realize a compact high-resolution zoom lens having a four lens group structure in which a third lens group is composed of three lenses of a positive power, a positive power, and a negative power in order from an object side and the two positive lenses and one negative lens are devised such that a half-field angle at a wide angle end is 41 degrees or more and a magnification ratio is 10 times or more. <P>SOLUTION: In a zoom lens in which a first lens group GI having positive power, a second lens group G2 having negative power, a third lens group G3 having positive power, and a fourth lens group G4 having positive power are arranged in order from an object side, an aperture diaphragm S is arranged between the second and third lens groups, an interval between the first and second lens groups is increased and an interval between the second and third groups is reduced in response to the variable magnification from a wide angle end, and the first lens group and the third lens group are moved to be located on the object side at the telephoto end rather than the wide-angle end, the third lens group, in order from the object side, is composed of a biconvex positive lens, a positive lens having a convex at the object side, and a negative lens of a meniscus shape having a convex at the object side, and a lens material of the third lens group has an appropriate refractive index, dispersion, and a partial dispersion ratio. <P>COPYRIGHT: (C)2012,JPO&INPIT |
