Adaptive interferometric null testing for unknown freeform optics metrology

Abstract

We report an adaptive interferometric null testing method for overcoming the dynamic range limitations of conventional null testing approaches during unknown freeform optics metrology or optics manufacturing processes that require not-yet-completed surface measurements to guide the next fabrication process. In the presented adaptive method, a deformable mirror functions as an adaptable null component for an unknown optical surface. The optimal deformable mirror's shape is determined by the stochastic parallel gradient descent algorithm and controlled by a deflectometry system. An adaptive interferometric null testing setup was constructed, and its metrology data successfully demonstrated superb adaptive capability in measuring an unknown surface.

Measurement of Freeform Optical Surfaces: Trade‐Off between Accuracy and Dynamic Range

“…Huang et al. [ 116 ] proposed the DM‐based adaptive null interferometry in 2016 with in situ calibration of the DM by a deflectometry system. The principle is shown in Figure a.…”

“…a) Reproduced with permission. [ 116 ] Copyright 2016, Optical Society of America. b,c) Reproduced with permission.…”

Fabrication and Dynamic Deflectometry Testing Methods for Freeform and Deformable Optics

“…A newly developed adaptive metrology uses a deformable mirror (DM) as an adaptable null component for interferometric tests [7]. To determine the optimal null shape for the DM, we use a stochastic parallel gradient descent (SPGD) algorithm.…”

Freeform surface adaptive interferometry assisted with simulated annealing-hill climbing algorithm

“…Several dynamic compensators have been developed, in which adaptive optics, such as the deformable mirror (DM) and liquid crystal spatial light modulator (LC-SLM), have the most prominent performance. The freeform surface adaptive interferometer (FSAI) thus has been proposed [14][15][16][17][18][19][20][21][22][23] based on the DM and LC-SLM, aiming to perform adaptive aberration correction to realize the near null test in testing freeform surfaces with various shapes. The near null fringes would be acquired from the initial interferogram with the implementation of the adaptive compensation algorithm.…”