  The possibility of using Infrared Lock-In Thermography (LIT) to estimate the
thickness of a sample was assessed and shown to be accurate up to 1.8mm. LIT is
a technique involving heating samples with halogen lamps with varying intensity
over time. The intensity is defined by sinusoidal functions. LIT was conducted
on samples of varying thickness, gradient, and shape. The Lock-In phase signals
were calculated, and a database was then created with the data obtained and was
used to estimate the thickness based on the original phase signal. A
relationship between gradient and phase signal was also shown based on our
data, contrary to current findings in existing literature.

Applied Physics