Virtual wave concept with prior information for high-resolution 3D thermographic image reconstruction (Conference Presentation)

In active thermography, the structure below the surface can be reconstructed from measured surface temperature signals. The main drawback in active thermographic is the degradation of the spatial resolution with imaging depth. Recently, we used a mathematical compensation method to transform each measured surface temperature signal into a virtual acoustic wave, which is the solution of the wave equation and therefore ultrasound image reconstruction methods can be used. This allows a 3D thermo-tomography, which combines the advantages of thermographic and ultrasonic imaging, but the degradation of spatial resolution for deeper lying structures is still significant. A possibility to overcome this degradation is to incorporate prior information such as positivity and sparsity in the reconstruction process. Based on pulsed thermography data we show that the thermographic detection limit is extendible by a factor of four.