Abstract: Device and method for three-dimensional measurements and observation of a surface layer of a thin-film structure, comprising a monitoring unit 4 which includes a video camera 12, a wide-beam illumination source 14, a narrow-beam illumination source, 20, an operation and control unit and a table for horizontal movement. The device comprises a Wollaston prism 24 arranged on the optical path of the narrow light beam, in order to obtain two narrow light beams whose polarization states are linear and mutually orthogonal, a polarizer 27 arranged on the optical axis of the Wollaston prism 24 so that the reflected narrow light beam passes through it after its travel through the Wollaston prism 24, and a detection cell 28.