| 摘要 |
PROBLEM TO BE SOLVED: To provide a large aperture zoom lens that ensures back focus optimum for a digital single lens reflex camera, has a zoom ratio of approximately three times, can fix an F value when zooming, is small in size, and has an anti-vibration function. SOLUTION: An optical system includes a first positive lens group L1, a second negative lens group L2, a third positive lens group L3, and a fourth positive lens group L4. In zooming from a wide angle end to the telephoto end, the optical system moves these lens groups so that the interval between the first and second lens groups L1 and L2 increases, the interval between the second and third lens groups L2 and L3 and the interval between the third and fourth lens groups L3 and L4 decrease. The third lens group L3 includes a 3a-th positive lens component L3a, 3b-th negative lens component L3b, and a 3c-th positive lens component L3c, the 3b-th lens component L3b serves as an anti-vibration lens group. When zooming from the wide angle end to the telephoto end, the diameter of an aperture increases to fix the F value, and predetermined conditional expressions are satisfied. COPYRIGHT: (C)2011,JPO&INPIT
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