Measurements of image quality and surface shape of microlens arrays for Shack-Hartmann wavefront sensors

We present the results of the evaluation of the ensquared energy of eight commercially available and custom made Microlens arrays (MLAs) with different focal length Plano-Convex microlens. The highest efficiency is observed with a 300 μm pitch MLA with no AR-coating and square apertures, which show 79% light ensquared within the first dark ring compared to the uniform illumination of the sub-aperture. To quantitatively explain the observed difference in the ensquared energy, we measured the surface shape of these MLAs using a laser interferometer. The comparison between the ensquared energy and the surface shape inferred that the lower ensquared energy of a MLA than the other MLAs with same 300 μm pitch can be explained with the deviation of the ideal shape at the outer part of the each lens.