One actual and promising method of researching optically inhomogeneous media is the method of the laser refractography. It is based on the phenomenon of refraction of structured laser radiation in optically inhomogeneous media and registration of its form deviations with the digital camera. Two types of optical inhomogeneities are researched in this work: a diffusion layer of liquids and temperature fields near heated or cooled objects. It was considered conditions for the occurrence of caustics in longitudinal probing of optical stratified inhomogeneous media by plane and cylindrical laser beams in this paper. Experimental setup for 3D-visualization of laser beams’ refraction was created. 3D-refractograms of cylindrical laser beam propagation in the diffusion layer of liquid were obtained.