PROBLEM TO BE SOLVED: To provide an objective lens for an endoscope, which may be focused using a simple and cost-effective method, an actuator for focusing the objective lens, and an endoscope system including the objective lens.SOLUTION: The objective lens for an endoscope includes a plurality of lenses and a stop ST, and an optical element OE disposed adjacent to the stop ST. A focal length may be varied by moving the optical element OE in a direction different from an optical axis O. The plurality of lenses comprise a front lens group G1 having a negative refractive power which is arranged in front of the stop and a rear lens group G2 having a positive refractive power which is arranged in rear of the stop, and the optical element is disposed between the front lens group and the stop or between the stop and the rear lens group.COPYRIGHT: (C)2013,JPO&INPIT【課題】簡単かつ低コストの方法でフォーカシングの可能な内視鏡用対物レンズ、フォーカシングのためのアクチュエータ及び内視鏡システムを提供する。【解決手段】複数のレンズ及び絞りSTを備え、絞りに隣接して光学素子OEが配され、光学素子を光軸Oと異なる方向に動かして焦点距離を変化させる。複数のレンズが、絞りの前方に配された負の屈折力を持つフロントレンズ群G1と、絞りの後方に配された正の屈折力を持つリアレンズ群G2とで構成され、光学素子が、フロントレンズ群と絞りとの間、または絞りとリアレンズ群との間に配される。【選択図】図1
