  In this work, we present a novel approach to photothermal super resolution
based thermographic resolution of internal defects using two-dimensional pixel
pattern-based active photothermal laser heating in conjunction with subsequent
numerical reconstruction to achieve a high-resolution reconstruction of
internal defect structures. With the proposed adoption of pixelated patterns
generated using laser coupled high-power DLP projector technology the
complexity for achieving true two-dimensional super resolution can be
dramatically reduced taking a crucial step forward towards widespread practical
viability. Furthermore, based on the latest developments in high-power DLP
projectors, we present their first application for structured pulsed
thermographic inspection of macroscopic metal samples. In addition, a forward
solution to the underlying inverse problem is proposed along with an
appropriate heuristic to find the regularization parameters necessary for the
numerical inversion in a laboratory setting. This allows the generation of
synthetic measurement data, opening the door for the application of machine
learning based methods for future improvements towards full automation of the
method. Finally, the proposed method is experimentally validated and shown to
outperform several established conventional thermographic testing techniques
while conservatively improving the required measurement times by a factor of 8
compared to currently available photothermal super resolution techniques.
