The invention relates to a transmitting optical element that is capable of taking images having a wide angle-of-view in general, and an image coming primarily from a vertical direction to a center axis in particular in simplified construction, is of small-format size and well corrected for aberrations, and an optical system using the same. The optical system is an imaging system that is adapted to form an object (6) around the center axis (1) on an image plane (7) orthogonal to the center axis (1). That imaging system comprises a front unit (3) rotationally symmetric about the center axis (1) and a rear unit (4) that is rotationally symmetric about the center axis (1) and has positive power. The front unit (3) comprises at least one transmitting optical element (2) formed of a transparent medium comprising two transmitting surfaces (21, 22) rotationally symmetric about the center axis (1) and having a refractive index of greater than 1. At least one transmitting surface (21, 22) of the transmitting optical element (2) is configured such that a normal thereto makes an angle with the center axis (1) near where the center axis (1) intersects the transmitting surface (21, 22).
