Fig. 10

Linear relations can be found between thickness and certain spectrum characteristics. This holds for thickness plotted against average slope in the 560–580 nm range (a), against the wavelength where a peak in slope occurs (b) and the value of this peak in slope (c). In order to extend the dynamic range of thickness measurement, plots b and c can be divided to obtain (d), where the maximum thickness that can be measured is larger than 250 μm