| 摘要 |
PROBLEM TO BE SOLVED: To provide a small high-powered macro lens having superior optical performance, well correcting aberration caused in the case of focusing from an infinity object to a point-blank range object, and having a four group structure comprising four lens groups with an inner focusing type up to an 1/2 imaging magnifications. SOLUTION: In focusing from infinity to a close-range, among the first to the fourth lens group G1-G4, the second lens group G2 and the third lens group G3 are moved along the optical axis direction independently from each other, wherein the third lens group G3 is moved greater to the object side than the second lens group G2. In this case, conditional expressions (1)β≥-0.5, (2) 0.5>BF/f and (3)-1.7<f1/f<-1.0 are satisfied, whereβis the maximum imaging magnification at the time of close-up state, f is the focal distance of the entire lens system at infinity, BF is back focus, f1 is the focal distance of the first lens group, and f again is the focal distance of the entire lens system. COPYRIGHT: (C)2011,JPO&INPIT |
