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W. Zou, X. Qi, S. A. Burns; Wavefront Control of Dual-Deformable-Mirror Adaptive Optics for Scanning Laser Ophthalmoscope. Invest. Ophthalmol. Vis. Sci. 2008;49(13):1848.
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© ARVO (1962-2015); The Authors (2016-present)
To develop a wavefront control algorithm for dual-deformable-mirror (DDM, including woofer-tweeter) adaptive optics. This research tests the algorithm for implementation in a new DDM adaptive optics scanning laser ophthalmoscope (AOSLO) under development.
The next generation AOSLO will have two (or more) deformable mirrors (DMs) instead of one DM. Typically, one DM will be a low order, high-stroke mirror (the woofer), and the other one will be a high-order, low-stroke mirror (the tweeter). An AOSLO system with the woofer-tweeter DMs is expected to have a better wavefront correction performance for high-resolution retinal imaging. Specifically, the experimental system under development is composed of a superlum diodes (SLD) point light source with central wavelength of 676.6nm, a Boston Micro DM (maximum stroke 2.5 µm), a Mirao-52d magnetic DM (maximum stroke 50µm), and a lenslet array directly coupled onto a digital CCD camera.We developed a new wavefront control algorithm, which is based on applying the slope measurements from one wavefront sensor to command two DMs to work together for correcting wavefront distortions in real time. The algorithm acts to decompose the estimated wavefront shape into two parts: one part is the low order aberrations which will be corrected by the Mirao-52d DM, and the other part is the high order aberrations to be corrected by the Boston Micro DM. Instead of separating the woofer and tweeter correction into two independent control processes as adopted in previous algorithms, we couple the dual-DM corrections together as a whole in a single control process, while the Mirao-52d DM still contributes to the low-spatial-frequency correction and the Boston Micro DM contributes to the high-spatial-frequency correction. The stroke amplitude of the low-frequency aberrations under control, such as wavefront defocus, is determined by a combination of a manual control (to set the plane of focus within the retina) and from slope measurements (to correct the ammetropia of the eye). In practice, a weighting factor is chosen to balance the wavefront corrections between the two DMs.
The mathematical framework of the proposed algorithm is simple. Theoretical analysis and simulations shows that this dual-process control is stable and efficient.
A real-time wavefront control algorithm for DDM adaptive optics for SLO is proposed. By combining the control of two mirrors and a single wavefront sensor into a single control system we will be able to obtain real time control of both low order and high order aberrations over a wide dynamic range.
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