Diffraction errors in micromirror-array based wavefront generation

Using Laser-based Speckle-Interferometers, the shape of optically rough surfaces can be measured precisely and contactlessly from variable measuring distances even in regions of difficult access. This work is concerned with the integration of a micromirror array (MMA) into an electronic Speckle-Pattern-Interferometer. With the adaptive optics, it is intended to adapt the phasefront of a reference wave to critical surface areas of the measurement object. Yet, due to the topography of the MMA, diffraction effects occur which affect the phase and intensity of the generated wavefront. We demonstrate how these diffraction effects can be efficiently modelled by a Fraunhofer diffraction method. We compare the results of this model to theoretical data obtained by a numerical Fresnel diffraction model and to measurement data obtained from a measurement setup incorporating a multi mirror array.

Research Highlights► Diffraction errors in Micro-Mirror-Array adaptive-optics obstruct efficient usage. ► We develop a modelling method to simulate the MMA diffraction errors. ► We demonstrate the accuracy of the model by comparing the model to experiments. ► We employ a high pixel count MMA device and a laser source for the experiments. ► We find an excellent agreement between model and experiments.