Abstract: A transportable scanning microscope assembly operating in situ comprises a light microscope column (1) which may be directly disposed on the object to be examined (19) through a supporting structure (16) withstanding pressure and defining an internal chamber (4) the lower aperture of which is limited by peripheral resilient sealing (17) intended to be disposed in abutment on the surface (19'), the chamber (4) being connected (21) to a transportable pumping device (4). In order to allow an angular range (A) of the surface (19') to be covered by the optical axis (15), the column (1) is mounted on the support (16) by means of a knee-joint (22) sealed by a metallic diaphragm (23). The invention is particularly useful in the checking of aircraft wings and mirrors.