The purpose of the present invention is to sufficiently correct chromatic aberration of magnification through a common optical element in the later stage while aligning the direction of an image of all fields of view. A wide angle optical system (3) comprises a first group (6) having negative and positive lenses (4, 5) with negative refractive power, a second group (7) having a reflective-refractive optical element (14), and a third group (8). The reflective-refractive optical element (14) includes a first surface (11) on the object side, having a first transmitting surface (11a) and a first reflecting surface (11b) disposed surrounding the first transmitting surface, a second surface (12) on the image side, having a second transmitting surface (12a) and a second reflecting surface (12b) disposed surrounding the second transmitting surface, and a third surface (13) that is a conical transmitting surface disposed between the first surface (11) and the second surface (12) and having an apex angle toward the object. The wide angle optical system (3) satisfies the following expression:νn > νpα/2 > 90° − θkWhere νn represents the Abbe number of the negative lens (4), νp represents the Abbe number of the positive lens (5), α represents the angle of the apex angle on the third surface (13), and θk represents a half field angle (0 < θk < 90°) of principal ray in the minimum angle of view within the lateral field of view.La présente invention vise à corriger de manière suffisante une aberration chromatique de grossissement à travers un élément optique commun dans létage postérieur tout en alignant la direction dune image de tous les champs de vision. À cet effet, un système optique grand angle (3) comprend un premier groupe (6) ayant des lentilles positive et négative (4, 5) dune puissance de réfraction négative, un deuxième groupe (7) ayant un élément optique à réflexion-réfraction (14), et un troisième groupe (8). Lélément optique à réflexion-réfraction (14) comprend une p
