Abstract: A transmitting antenna radiates a micro-wave field through an opening in the form of a rectangular wave-guide applied against the separation surface between a first medium, in which it is located, and a second medium, in which an object is buried. The micro-wave radiation reflected by the object is collected through the opening of a receiving antenna, also in the form of a rectangular wave-guide, applied against the radiating opening of the transmitting antenna. The collected radiation is measured at a series of points by means of pinpoint antennae located in the collecting opening. Thanks to the antennae arrangement, the collected radiation can be used as such, without having to subtract therefrom the result of a reference measurement. The invention can be used particularly to obtain, non destructively, images of metal bars buried in reinforced concrete.