| 摘要 |
PURPOSE:To provide enough back focus to set a rear converter and make a lens system small-sized and high-capacity, by constituting a relay lens group with two groups and dividing its rear group to two groups and satisfying specific conditions. CONSTITUTION:A relay lens group G4 of a zoom lens is constituted with two groups G41 and G42 having positive focal lengths F1 and F2 which are arranged in order from the object side. The rear group G42 is divided to a lens group G2N having a negative focal length F2N and a lens group G2P having a positive focal length F2P, and conditions of inequalities 1-4 are satisfied when the vertex interval and the shape factor are denoted as D and SF respectively. [When radiuses of curvature of object-side and image-side lens faces are ra and rb respectively, SF=(rb+ra)/(rb-ra) is true.] Thus, the exit pupil is placed in the infinity to secure enough back focus to set the rear converter, and a small-sized and high-capacity zoom lens is attained. |
