Thermal wavefront sensing fundamentals and applications

Abstract

Thermal wavefront sensing combines the essences of two legendary sensing technologies: infrared imaging and the Shack-Hartmann wavefront sensor. First applied to visible metrology, the Shack-Hartmann wavefront sensor is now adapted into infrared thermography, opening up an unchartered territory of science and technology. In its conception, the Shack-Hartmann extension is used to furnish extra spatial information: the propagating phase of thermal radiation, which enhanced the sensitivity in thermogram inspections. In this project, we investigated the fundamentals of thermal wavefront sensing to determine its analogy with visible wavefront sensing. Most of the results show inherent differences arising from the nature of thermal radiation which is broadband and diffuse. Some of the most prominent deviations from classical theories include diffraction effects from circular apertures and distortion of wavefronts due to diffusion and reflection effects. Nonetheless, in application thermal wavefront sensing shows promising results in its role of increasing the sensitivity of traditional thermographic defect inspection.