A one-step method for direct measurement of refractive index field is proposed. The method consists in combination of the optical probing step, i.e. obtaining projection data, with the following step of tomogram reconstruction, which is done by analog processing in the tomographic interferometer. Holographic interferometry technique is used to visualize the optical wave field that carries refractive index tomogram information. The real-time interferometric visualization of refractive index spatial distribution in either longitudinal or cross section of the objects under investigation has become possible.