Phase-stepped deflectometry as a powerful tool to determine the appear of paints and coatings

 
Phase-stepped deflectometry (PSD) is a relatively new, powerful and yet very affordable optical technique that can be used for the quantitative determination of the surface profile (appearance) of paints and coatings. With PSD several phase-stepped sinusoidal patterns are displayed on a computer screen which illuminates the surface under study and a camera is used to capture images of the reflected patterns. Analysis of these images allows quantitative determination of the surface profile. It will be shown that the correlation between PSD results and other methods used in the coating industry to evaluate appearance is generally very good. As PSD is a contactless and fast technique, it also allows determination of the appearance of wet layers and it can thus be used for the quantitative determination of sag and levelling phenomena in paints during drying and/or curing.