Direct modal wavefront estimation from speckle images

This article presents a method for direct estimation of modal wavefront coefficients from speckle images obtained using a thin diffuser. Zernike coefficients are recovered from intensity differences between reference and distorted speckle patterns using a least-squares formulation derived from a first-order Taylor expansion. Simulations demonstrate accurate reconstruction across a range of aberrations and detector noise levels. Compared to the Demon algorithm, the proposed method shows improved performance for small aberrations and under noisy conditions, while Demon performs better at large amplitudes. Experimental validation demonstrates good agreement with Shack-Hartmann measurements, with residual RMS errors consistent with experimental uncertainty.