Profile-Aided Subaperture Stitching Algorithm for the Measurement of Microlens Array Optics by Coherence Scanning Interferometry

Microlens array (MLA) optics play a crucial role in imaging systems. Its surface topography substantially influences its functional properties, e.g., uniformity of light field intensity distribution. Subaperture stitching (SAS) is a widely-used method for measuring the overall surface topography of optics. However, stitched surfaces of the classical and state-of-the-art (SOTA) instrument’s algorithm deviate substantially from the real surface due to accumulated errors when stitching numerous subapertures. Achieving accurate areal surface topography measurement of MLAs thus remains a considerable challenge. This study proposes a profile-aided stitching algorithm that eliminates accumulated errors by incorporating data from an ultraprecision 3-D profilometer. An error function is designed to integrate additional profile information, which comprises the weighted sum of errors between adjacent subapertures and the profile-derived errors. Determining matching point pairs and minimizing the error function are iteratively performed to improve the stitching accuracy. Both simulation and real experiment support that the error of the stitched surface of proposed method reaches the same level as the instrument’s error, and stitching accuracy of the proposed method reaches nanometric level, satisfying the nanometric measurement accuracy requirements of MLA optics.