  Shack-Hartmann wavefront sensors (SHWS) are generally used to measure the
wavefront curvature of light beams. Measurement accuracy and the sensitivity of
these sensors are important factors for better wavefront sensing. In this
study, we demonstrate a new type of SHWS with better measurement accuracy than
the regular SHWS. The lenslet array in the regular SHWS is replaced with an
array of coded phase masks and the principle of coded aperture correlation
holography (COACH) is used for wavefront reconstruction. Sharper correlation
peaks achieved by COACH improve the accuracy of the estimated local slopes of
the measured wavefront and consequently improve the reconstruction accuracy of
the overall wavefront. Experimental results confirm that the proposed method
provides a lower mean square wavefront error by one order of magnitude in
comparison to the regular SHWS.
