An infrared optical sensor for quantitative inline inspection of nanocoatings on plastic products

We developed a fast infrared sensor to quantify the film thickness of industrially applied SiOx or AlOx plasma coatings on non-flat polymer substrates at production speed. Its underlying physical principle is comparable to infrared reflection absorption spectroscopy (IRRAS) at selected, fixed wavelengths. The coating materials can be measured via their specific phononic absorption bands in the infrared spectral range. In this paper, we demonstrate the functionality of our sensor on actual packaging materials to showcase its aptitude for industrial inline inspection. Furthermore, we discuss a possible extension of our sensor to enable spectroscopic measurements using a tunable Fabry-Pérot filter.