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C. Li, N. Sredar, H. Queener, K. Ivers, J. Porter; Direct Slope Algorithm for Simultaneous Control of a Dual Deformable Mirror Adaptive Optics System. Invest. Ophthalmol. Vis. Sci. 2010;51(13):2309.
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© ARVO (1962-2015); The Authors (2016-present)
Many recent adaptive optics systems use two deformable mirrors (DMs) to correct the eye’s aberrations - a "woofer" DM to correct high amplitude, lower order aberrations and a "tweeter" DM to correct low amplitude, higher order aberrations. We developed and tested a direct slope reconstruction algorithm to simultaneously control two DMs in an adaptive optics scanning laser ophthalmoscope (AOSLO).
The dual DM direct slope algorithm uses the correlation matrix (obtained from both DM response matrices) to compute and remove the coupling modes from the tweeter’s original response matrix. This process results in a new tweeter response matrix that is orthogonal to that of the woofer and thereby prevents both DMs from correcting the same aberrations. Singular value decomposition of the global reconstruction matrix (consisting of the woofer and new tweeter response matrices, and a restriction matrix that minimizes piston, tip and tilt) yields the global control matrix used to calculate voltages for both DMs. This algorithm was implemented in an AOSLO consisting of a 140 actuator Boston Micromachines Corp. MEMS DM (tweeter) and an Imagine Eyes Mirao-52e DM (woofer). We compared the performance of the simultaneous dual DM direct slope algorithm with a 2-step sequential control algorithm (woofer correction first followed by separate tweeter correction) in 2 normal human subjects with pre-AO corrected total root-mean-square (RMS) wavefront errors of 1.55 µm and 5.58 µm (8-mm pupil) and spherical equivalent refractive errors of +0.35 D and -1.88 D.
The same mean residual RMS error (0.11 ± 0.02 µm) and similar convergence times were obtained with simultaneous and 2-step control. While simultaneous and 2-step control produced similar retinal image quality, mean retinal image intensity was slightly higher with 2-step control.
The dual DM direct slope algorithm provides simple and efficient correction of the eye’s aberrations that is nearly identical to that achieved with 2-step control. Simultaneous control may provide improved aberration correction when sectioning through the retina and reduce overall experiment time (compared with 2-step control).
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