Non-Invasively Tracking an Arbitrary Deformable Object Through Scattering Media and Around Corners via Speckle Correlations.

Tracking a hidden object is of great significance across various fields. Although several methods have attempted to track an object behind scattering media, they either only work by assuming the object's shape is invariant, or require prior information. Here, we propose a speckle correlation centroid localization method (SCCLM) for non-invasively tracking a moving deformable object behind or inside scattering media and around corners, without any prior information. After capturing speckle patterns of the object at different moments, the relative centroid displacements can be determined by locating the centroids of speckle auto-correlation (SAC) and speckle cross-correlation (SCC) at the adjacent moments, rather than conventionally locating the peak positions of SAC and SCC. The trajectory of the object is then reconstructed by sequentially superimposing the relative centroid displacements. Experimental results validate that the SCCLM can track a hidden object moving beyond the memory effect region, which is not only scaling, rotating, and stretching, but also completely changing into different shapes. Furthermore, its effectiveness is verified for tracking a moving deformable object through dynamic scattering media, such as chicken breast tissue, and around corners. Even when the scene grows more complex with many objects, the SCCLM remains valid.