| 摘要 |
An image forming device is provided with: a zoom lens system TL that performs magnification varying by changing the distance between the lens units; and an image sensor SR that converts an optical image formed by the zoom lens system TL into an electric signal. The zoom lens system TL includes at least a negative first lens unit GR 1 and a positive second lens unit GR 2 , and at least the first lens unit GR 1 and the second lens unit GR 2 move in zooming from the wide angle end (W) to the telephoto end (T). The second lens unit GR 2 includes three lens elements of, from the object side, a positive meniscus lens element L 21 convex to the object side, a negative lens element L 22 and a positive lens element L 23 , and the following condition is satisfied: <?in-line-formulae description="In-line Formulae" end="lead"?>-1.0<(CR 1 -CR 2 )/(CR 1 +CR 2 )<0.0<?in-line-formulae description="In-line Formulae" end="tail"?> (CR 1 is the front radius of curvature of the most object side lens element L 21 in the second lens unit GR 2 , and CR 2 is the rear radius of curvature of the most object side lens element L 21 in the second lens unit GR 2 ).
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