Coatings thickness detection on anisotropic materials with sparse decomposition method

Sparse decomposition method is used to locate the layer interface pulse with terahertz transmission signal as prior knowledge. Then take advantage of time of flight (TOF) method to realize multi thin layer coating thickness detection on anisotropic substrates without considering the complex properties of the anisotropic materials. This method is validated on the coated carbon-fiber reinforced polymers (CFRP) samples with two coating layers successfully.