The present invention relates to a scanning microscope using a heterodyne interferometer, which can be used for mapping or imaging complex optical parameters such as physical structures and material properties of a sample under test. The heterodyne interferometer is designed to provide in- and quadrature-phase interference signal which can be used for extracting the phase and amplitude change induced on the probe beam. The phase and the amplitude of the probe beam, which is reflected from or transmitted through the sample, are modified by the physical structures and material properties of the sample. Therefore, by scanning the probe beam, local variations of the phase and amplitude can be mapped, and, thereby, three-dimensional microscopic physical structures and material properties can be imaged by processing the phase and amplitude values.