Performance of 97-elements ALPAO membrane magnetic deformable mirror in Adaptive Optics - Optical Coherence Tomography system for in vivo imaging of human retina

Abstract

Abstract-We present an evaluation of two different configurations of the ALPAO 97-actuator membrane magnetic deformable mirror for wavefront correction, using either 7 or 9 actuators across the eye pupil. These tests included monitoring of aberration correction for a human subject. This AO-sub system is part of the UC Davis high-resolution human retinal imaging adaptive optics -optical coherence tomography (AO-OCT) instrument. AO-OCT allows the three-dimensional (3D) visualization of different retinal structures in vivo with high volumetric resolution (3x3x3μm 3 ).The combination of adaptive optics (AO) with any retinal imaging technique allows for improved lateral, and in the case of the confocal scanning laser ophthalmoscope (cSLO) and fundus camera, also axial resolution. The AO-OCT instrument at UC Davis has been under development for several years, and has demonstrated the utility of this technology for microscopic, volumetric, in vivo retinal imaging [1]-[3]. In our adaptive optics system a Hartmann-Shack wavefront sensor and a deformable mirror operate in a closed loop. This approach, to improve the transverse resolution for retinal imaging by correction of the eye's static and dynamic aberrations, has been demonstrated first in standard AO-fundus cameras [4] followed by AO-SLO [5]. The latter modality allows realtime observation of microscopic retinal structures in human eyes, including the photoreceptor cone mosaic, nerve fiber layer and microscopic blood flow in capillaries. Due to the limited axial resolution of these systems, however, they cannot be used to image other retinal layers or to create detailed 3D reconstructions of retinal volumes, a key advantage associated with OCT imaging [6]- [8].As previously reported, the initial configuration of the UC Davis AO sub-system used a 35-actuator AOptix bimorph deformable mirror (DM) for low-order, high-* E-mail: rjzawadzki@ucdavis.edu stroke correction [9] and a 140-actuator Boston Micromachines MEMS DM for high-order correction. The performance of the AO-subsystem of this instrument was previously evaluated and the results were presented by Evans et al. [10]. Later we replaced this configuration with a single novel membrane magnetic deformable mirror with increased stroke and actuator count. Initially, we implemented a configuration that used only the center 10.5 mm diameter of the DM for wavefront correction, equivalent to 69-actuators of the ALPAO membrane magnetic deformable mirror [3] (7 actuators across the eye pupil). In that configuration both the AOptix and MEMS DM's were removed from the system. A flat mirror was placed at the MEMS DM position and the ALPAO DM was placed at the AOptix position. Figure 1 shows the schematic of our AO system using two vs. one deformable mirror. Note that all the other components remained the same.This simple swap of the deformable mirrors, without changes in any other optical components, as shown in Fig. 1, resulted in non-optimal use of that DM. Recently, we have upgraded elements of our sample arm optics to a...

Adaptive shaping of laser beams for high-harmonic generation applications

“…These systems have been used to remove wavefront aberrations in applications such as STORM microscopy and in-vivo biomedical imaging [106,142]. Lei et al used a Woofer-Tweeter system controlled by a gradient descent algorithm which used the Strehl ratio, S r , as a cost function [143].…”