Abstract — Optical thickness metrology techniques rely on illuminating the sample of interest with light and analyzing the reflections. These techniques work best on objects with smooth surfaces: glass lenses, windows, plastic webs, etc. However, measurement capabilities of such instruments deteriorate in situations where the reflected light is affected by imperfect surfaces, due to optical scattering or absorption. This application note describes a method of obtaining thickness information for such imperfect samples using its optical crosssectional view acquired in a non-destructive way. The method employs the commercially available instrument, OptiGauge II, which is based on time-domain lowcoherence interferometry.