The Largest Open Access Portal of Nondestructive Testing (NDT)

Energy transport in diffusion-wave fields is gradient driven and therefore diffuse, yielding depth-integrated responses with poor axial resolution. Traditional diffusion-wave techniques, limited by the physics of parabolic diffusion, can only produce depth-integrated planar images as they are unable to generate three-dimensional subsurface imaging. This talk will present two new imaging methods developed in the CADIFT for enabling parabolic thermal-wave fields to exhibit energy localization akin to propagating hyperbolic wave-fields. This approach when used with a mid-IR camera results in depth-selective (or depth-resolved) photothermal imaging which not only improves axial and depth resolution, but also allows for deconvolution of individual responses of superposed axially discrete sources, opening a new field of subsurface Photothermal Coherence Tomography (PCT) using thermal waves. In this talk I will present two novel thermal-wave imaging methodologies: Matched filter binary phase coded (BPC) PCT and truncated-correlation photothermal coherence tomography (TC-PCT). The physical principles of these methodologies and examples of imaging applications to engineering materials and biomaterials will be discussed.