  We present the optimal convergence and shear estimators for lensing
reconstruction from the cosmic microwave background temperature field. This
generalizes the deflection estimator, is sensitive to non-lensing modes,
provides internal consistency checks, and is always at least as optimal.
Previously, these estimators were only known in the squeezed limit. This paper
decomposes convergence and shear fields into cosine and sine waves and the
lensed correlation function is then Taylor expanded in the wave amplitudes.
Maximizing the likelihood function gives the optimal estimators for the
convergence and shear fields.
  This method has the potential to improve the lensing reconstruction of the
cosmic microwave background polarization field: the shear and convergence can
be optimally combined to form a deflection estimator, or used separately to
separate non-lensing modes, or utilize lensing of non-Gaussian secondary
foregrounds.
