Accelerated Hadamard-Based Wavefront Shaping for Deep-Focusing in Scattering Media via Speckle Variance

Due to the light-scattering effect of inhomogeneous media, achieving non-invasive focusing within scattering media remains a challenge. Existing techniques suffer from poor noise resistance, slow optimization processes, and sometimes ineffective focusing. This paper presents a wavefront shaping technique that employs fluorescence speckle variance as feedback. A circular Hadamard mask is introduced to improve laser energy efficiency by mitigating beam clipping caused by conventional square masks. Combined with a four-step phase-shifting algorithm, this method iteratively adjusts the wavefront phase via a spatial light modulator, significantly accelerating the optimization process. Experimental results demonstrate that the proposed method can rapidly and precisely focus on a single particle within scattering media, featuring fast convergence and enhanced energy utilization. This approach opens new possibilities for applications in life sciences, such as cancer pre-diagnosis.