Characterization of a MEMs deformable mirror by far field intensity evaluation

Abstract

The performance of an adaptive optics (AO) system is typically measured using the wavefront sensor (WFS). However, another method is to use the point spread function (PSF), which is sensitive to scatter, does not act as a low pass filter and is not dependent on the WFS calibration. We decided to examine the performance of an AO system built for vision science that employed a micromechanical systems (MEMS) based deformable mirror (DM). Specifically, the MEMS DM consists of 489 actuators, resulting in 163 segments each with individual piston/tip/tilt control. Initial evaluation of the DM with a model eye included determining the ability of the DM to generate individual Zernike polynomials and evaluating the far field PSF to measure wavefront correction performance. For individual Zernike polynomial terms, the DM was found to be capable of correcting the aberration magnitudes expected from previously published human population studies.^{1, 2} Finally, the DM was used in an AO fundus camera to successfully acquire images of cone photoreceptors in a living human eye. This is part of ongoing work which will incorporate the MEMS DM into both an AO scanning laser ophthalmoscope (SLO) and an AO optical coherence tomography (OCT) system where the form of the PSF at the confocal pinhole/optical fiber is important for optimal imaging.