Accuracy and linearity of time-domain THz paint thickness measurements

An analysis of the single point reproducibility of TD-THz based paint thickness measurements demonstrated a precision of 130 nm, corresponding to 0.1% of the measured thickness. A detailed model of the anticipated TD-THz waveforms from samples of varying thickness indicates that an intrinsic uncertainty of 0.09% is anticipated in the absence of environmental fluctuations. Therefore, the influence of oscillations in the THz field associated with the initial reflection does not adversely impact the ability to extract accurate paint thickness information, and the noise associated with these oscillations could limit the measurement uncertainty of a calibrated instrument under optimum laboratory conditions. In the case of a deployed sensor, we anticipate that the accuracy will be degraded by environmental fluctuations.