| 摘要 |
PURPOSE:To obtain a zoom lens wide in power variation range and has various aberrations, specially, of distortion and coma are compensated excellently by composing the lens of four positive, negative, positive, and positive lens groups successively from the object side and setting specific conditions. CONSTITUTION:The 1st positive lens group G1, the 2nd negative lens group G2, the 3rd positive lens group G3, and the 4th positive lens group G4 are provided successively from the object side and air gaps among the respective lens groups are varied to constitute a zoom lens which varies in power. Then, the 2nd lens group G2 is composed of the 1st negative meniscus lens element having a convex surface on the object side, the 2nd negative lens element L22, the 3rd biconvex positive lens element L23, and the 4th negative lens element L24 having a large-curvature surface at the object side successively from the object side. Then, inequalities hold, where fw is the shortest focal length of the whole system, fT the longest focal length of the whole system, fn the focal length of each lens element, ra and rb the radii of curvature of the object-side and image-side surfaces of the 3rd element of the 2nd lens group, and DH the distance between the object-side and image-side principal points of the 2nd lens group. |
