| 摘要 |
PURPOSE:To shorten the overall length of a zoom lens and also decrease the diameter of a front lens although the zoom ratio and diameter ratio are large and an air converted back focus is long by providing there movable lens groups and specific conditions are satisfied. CONSTITUTION:The zoom lens consists of the 1st lens group G1 with negative refracting power, the 2nd lens group G2 with positive refracting power, the 3rd lens group G3 with negative refracting power, the 4th lens group G4 with negative refracting power, and the 5th lens group G5 with positive refracting power successively from the object side. When the power is varied from a wide-angle size to a telephoto side, the 2nd lens group G2 moves to the object side, the 3rd lens group G3 moves to the image size reversely, and the 4th lens group G4 moves to the object side to draw a convex locus while the 1st lens group G1 and the 5th lens group G5 are both fixed during the power variation. The respective lens groups which constitute the power variation system preferably satisfy inequalities.
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