| 摘要 |
PROBLEM TO BE SOLVED: To provide a zoom lens capable of achieving a high magnification ratio and having satisfactory optical performance over the whole scope of zooming from a wide angle end to a telephoto end. SOLUTION: The zoom lens has a first group of lenses having positive refractive power, a second group of lenses having negative refractive power, a third group of lenses having positive refractive power, and a fourth group of lenses having positive refractive power, in this order from an object side to an image side. An interval between the first group of lenses and the second group of lenses is larger and an interval between the second group of lenses and the third group of lenses is smaller at the telephoto end than the intervals at the wide angle end, and each group of lenses moves to enlarge an interval between the third group of lenses and the fourth group of lenses for zooming. The second group of lenses is composed of three lenses, namely, a negative lens, a negative lens, and a positive lens each having an aspherical face shape. Each of focal length f2 of the second group of lenses, focal lengths fw, ft at the wide angle end and the telephoto end of the zoom lens, and a shift amount M1 of the first group of lenses in the direction of optical axis at the telephoto end when compared with that at the wide angle end must be properly set. COPYRIGHT: (C)2010,JPO&INPIT |
