| 摘要 |
PROBLEM TO BE SOLVED: To obtain a three-group zoom lens having bright aperture such as F2.8 and a variable power ratio equal to or above 2.5, realizing high speed focusing and miniaturization, achieving high resolving power and having good aberration by adopting a rear focus type while properly setting the position of an exit pupil from an image pickup surface and further satisfying specified lens shape and a conditional expression. SOLUTION: As for this lens, three lens groups G1, G2 and G3 which are negative, positive and positive are arrayed in order from an object side. In the case of varying power from a wide-angle end to a telephoto end, the lens group G1 is moved to relatively approach the lens group G2 and the lens groups G2 and G3 are moved to the object side. The lens group G2 is constituted by disposing a diaphragm 3, a 3rd lens L3 consisting of a biconvex lens whose surface having strong curvature faces to the object side, a 4th lens L4 consisting of a positive meniscus lens whose convex surface faces to the object side and a 5th lens L5 consisting of a negative meniscus lens whose concave surface faces to an image side in order from the object side. Especially, the lens satisfies the following conditional expression (5). In the expression (5)ν2P>68;ν2P is the mean value of the Abbe number of the positive lens of the 2nd lens group.
|
