PROBLEM TO BE SOLVED: To prevent an image of a foreign object such as a flaw, a dust, and a defect of an optical element from being superimposed on an intermediate image and acquire a clear final image even if the intermediate image is formed at a position coincident with a position of the optical element.SOLUTION: Provided is an imaging optical system 3 comprising: a plurality of imaging lenses 11, 12, 13, and 16 forming a final image IF and at least one intermediate image II； a first phase modulation element 10 disposed to be closer to an object than the intermediate image II formed by any one of the imaging lenses, and applying a spatial disarray to a wavefront of light from the object； and a second phase modulation element 15 disposed at a position at which the at least one intermediate image II is held between the first phase modulation element 10 and the second phase modulation element 15, and cancelling the spatial disarray applied to the wavefront of the light from the object by the first phase modulation element 10, the second phase modulation element 15 including a plurality of cylindrical lenses 15a, 15b disposed to be apart from each other in an optical axis direction, and a principal point HC formed by the entire system is disposed to be located near a pupil position POB of the imaging lens.SELECTED DRAWING: Figure 1【課題】中間像が光学素子に一致する位置で結像されても、中間像に光学素子の傷、異物および欠陥等が重なることを防止して鮮明な最終像を取得する。【解決手段】最終像ＩＦおよび少なくとも１つの中間像ＩＩを形成する複数の結像レンズ１１，１２，１３，１６と、結像レンズにより形成されるいずれかの中間像ＩＩよりも物体側に配置され、物体からの光の波面に空間的な乱れを付与する第１の位相変調素子１０と、第１の位相変調素子１０との間に少なくとも１つの中間像ＩＩを挟む位置に配置され、前記第１の位相変調素子１０により物体からの光の波面に付与された空間的な乱れを打ち消す第２の位相変調素子１５とを備え、第２の位相変調素子１５が、光軸方向に間隔をあけて配置された複数のシリンドリカルレンズ１５ａ，１５ｂを備え、全系のなす主点ＨＣが結像レンズの瞳位置ＰＯＢの近傍に位置するように配置されている結像光学系３を提供する。【選択図】図１
