  Imaging at depth in opaque materials has long been a challenge. Recently,
wavefront shaping has enabled significant advance for deep imaging.
Nevertheless, most non-invasive wavefront shaping methods require cameras, lack
the sensitivity for deep imaging under weak optical signals, or can only focus
on a single "guidestar". Here, we retrieve the transmission matrix (TM)
non-invasively using two-photon fluorescence exploiting a general single-pixel
detection framework, allowing to achieve single-target focus on multiple
guidestars spread beyond the memory effect range. In addition, if we assume
memory effect correlations exist in the transmission matrix, we are able to
significantly reduce the number of measurements needed.
