| 摘要 |
PROBLEM TO BE SOLVED: To provide a variable-focal-length lens system in which the amount of movement is reduced at short-range focusing, and to provide an imaging unit using the variable-focal-length lens system. SOLUTION: The variable-focal-length lens system is constituted by arranging, in order from an object side, a first lens group G1 that is positive, a second lens group G2 that is negative, a third lens group G3 that is positive, a fourth lens group G4 that is negative, and a fifth lens group G5 that is positive. In the variable-focal-length lens system, when a lens position changes from a wide angle end to a telephoto end, the first lens group is fixed, the second lens group is moved towards an image side, the third lens group is fixed, the fourth lens group is moved for focusing and for compensating for variation in image face position resulting from the movement of the second lens group, the fifth lens group is fixed, and an aperture diaphragm S is disposed near the third lens group. In the case, where f1 is the focal length of the first lens group, fw is the focal length of the entire system at the wide angle end, ft is the focal length of the entire system, and f2 is the focal length of the second lens group, the following conditions are satisfied: (1) 2<f1/(fw×ft)<SP>1/2</SP><2.5 and (2) -1.6<f2/fw<-1.2. COPYRIGHT: (C)2006,JPO&NCIPI |
