Abstract: An optical assembly comprising a microscope (1) including a binocular (3) with a pair of oculars (4, 5), an optical body (8) and an objective lens (9) and an optical path; and an endoscope (2) provided with an extension (10), an outlet ocular (16) and an optical path. A commutating modulus (12, 13, 14; 18, 19, 14) is disposed between the binocular (3) and the optical body (8) of the microscope, and the outlet ocular (16) of the endoscope (2) as to enable an observer whose eyes are located at each ocular (4, 5) of the microscope (1) to observe selectively either: (a) the optical path of the microscope (1), or (b) the optical (or electronic) path of the endoscope (2), or (c) both optical paths simultaneously to scan an object to be investigated.