Multi-dimensional spatial-temporal projection ultrafast compressed imaging.

Studying various non-repeatable transient phenomena such as the transfer of photosynthetic energy and protein folding is crucial for gaining in-depth insights into multiple disciplines, while single-shot ultrafast compressed imaging provides a potent method for revealing the ultrafast dynamic process. The principle of this technology involves projecting encoded transient phenomena along a one-dimensional spatial axis onto the focal plane array and reconstructing the transient data via compressed sensing, enabling an extremely high imaging sequence depth at THz frame rates. However, this imaging method relying on single-dimensional spatial-temporal projection (SSP) suffers from severe directional constraints on reconstruction resolution, due to the suppressing of spatial features along non-projection direction. Consequently, this bottleneck seriously restricts the observation of complex transient features, hindering this technology to balance both high sequence depth and ultra-high spatial resolution. In this paper, we propose a multi-dimensional spatial-temporal projection ultrafast compressed imaging technique (MSP), which integrates multi-angle spatial-temporal data projection module into traditional SSP system. By computationally coupling projection images from both systems, MSP effectively restores omnidirectional frequency information, significantly enhancing spatial resolution. Static experiments demonstrate that both the lateral resolution and longitudinal resolution of MSP have reached 813 lp mm-1 (620 nm spatial resolution). Using MSP, we have successfully observed the transient process of femtosecond laser-material interaction with sub-micron all-directional accuracy under a 60-frame acquisition in a single-shot. MSP provides a new method for observing complex and changeable transient processes, and shows important potential in promoting the basic research of transient phenomena.