| 摘要 |
PURPOSE:To realize a small-sized, lightweight zoom lens system which has high performance from a wide to a telephoto range and also has high zoom magnification, by shortening the overall length when the focal length is shortened by establishing specific relations among the focal lengths, etc., of respective lens groups. CONSTITUTION:In zooming from a wide terminal to a telephoto terminal, the 1st and 4th positive lens groups are moved linearly to an object side, and the 2nd negative lens group is moved linearly in the opposite direction; and the movement of an in-focus position caused resultingly is compensated by the curved-line movement of the 3rd positive lens group. In addition, 0.6fM<=f4<=1.35fM, 0.4fM<=f3 <=0.9fM, and 0.2y'Z<=LT-LW<=0.4y'Z, where f3 and f4 are the focal lengths of the 3rd and 4th lens groups, fM=(fW.fT)<1/2>, and fW and fT are the focal lengths of the whole lens system at the wide terminal and telephoto terminal; and Z is zoom ratio, (y') is the half length of the diagonal of an image plane, and LW and LT are the overall lengths of the lens system at the wide and telephoto terminals. |
