Non-ideal equivalent model-based terahertz nondestructive measurement for double-layer polymer films.

A terahertz nondestructive testing technique for bilayer films based on a non-ideal equivalent model is presented, capable of simultaneously and online measuring the thickness, refractive index, and extinction coefficient of each layer in a bilayer film sample. This method overcomes the limitations of existing testing approaches based on ideal models by fully accounting for errors arising from the manufacturing process and instrument deviations. By utilizing a neural network-based measurement algorithm for bilayer films, it enables more precise measurement of sample information. Experimental results demonstrate that this method can accurately measure the thickness, refractive index, and extinction coefficient of double-layer film samples. These findings provide a model for high-precision terahertz nondestructive testing of double-layer film samples and offer a new approach to online inspection.