A thin layer of NLC applied on the surface of a material as a free film can visualize through a polarizing microscope different types of surface defects. We developed a new modification of this LC vision based on phase transitions in NLC, which increase the contrast or the size of defect’s images. The behavior of nematic phase is explained using a simplified Landau approach. For the first time the film thickness, varying because of the molecules reorientation, is taken into account.