| 摘要 |
PURPOSE: A telescopic lens system is provided to offer an inner focus type wide-angle structure. CONSTITUTION: A first lens group(G1) has positive refraction and includes at least three pieces of positive lenses and one piece of negative lens. A second lens group(G2) has negative refraction and makes focusing while moving along the optical axis. A third lens group(G3) is arranged in order from the object side to the image side and includes a doublet lens where a negative lens concave at the object side and a positive lens convex at the image side are bonded together, a positive lens convex at both sides, and a negative lens concave at the object side.
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