ZOOM IMAGING OPTICAL SYSTEM

To provide a zoom optical system which features a fixed total length over entire zooming and focusing ranges, suppressed manufacturing error sensitivity, a small image height change rate while wobbling, good optical performance over entire zooming and focusing ranges, anti-shake functionality, and minimized weight of an anti-shake lens group and focusing lens group.SOLUTION: A zoom imaging optical system is provided, comprising a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group having positive refractive power, and a fifth lens group having negative refractive power in order from the object side to the image side. The first and fifth lens groups are stationary relative to the image plane while zooming. The fourth lens group moves toward the object side along an optical axis when shifting focus from an object at infinity to a nearby object.SELECTED DRAWING: Figure 1 【課題】変倍、フォーカス全域時に全長固定型であり、製造誤差敏感度を抑え、ウオブリング時の像高変化率が少なく、変倍、フォーカス全域にわたり、良好な光学性能を備え、防振機能を有し、防振レンズ群及びフォーカスレンズ群の重量を抑制した、変倍光学系を提供する。【解決手段】物体側から像側へ順に、正の屈折力の第１レンズ群、負の屈折力の第２レンズ群、正の屈折力の第３レンズ群、正の屈折力の第４レンズ群、負の屈折力の第５レンズ群からなり、変倍時に、前記第１レンズ群と前記第５レンズ群とが像面に対し固定であり、無限遠物体から近距離物体へのフォーカシングに際して、前記第４レンズ群が光軸に沿って物体側に移動することを特徴とする変倍結像光学系とした。【選択図】図１