Light focusing through scattering media via linear fluorescence variance maximization, and its application for fluorescence imaging

We demonstrate focusing and imaging through a scattering medium without access to the fluorescent object by using wavefront shaping. Our concept is based on utilizing the spatial fluorescence contrast which naturally exists in the hidden target object. By scanning the angle of incidence of the illuminating laser beam and maximizing the variation of the detected fluorescence signal from the object, as measured by a bucket detector at the front of the scattering medium, we are able to generate a tightly focused excitation spot. Thereafter, an image is obtained by scanning the focus over the object within the memory effect range. The requirements for applicability of the method and the comparison with speckle-correlation based focusing methods are discussed.