Modal Fourier Wavefront Reconstruction Using FPGA Technology

Abstract

Atmospheric turbulence introduces optical aberration into wavefronts arriving at ground-based telescopes. The wavefront reconstruction using fast Fourier transforms (FFT) and spatial filtering is computationally tractable and sufficiently accurate in large Shack-Hartmann-based adaptive optics systems (up to 10,000 actuators). A first design has been developed using a Graphical Processing Units (GPU) platform. However, an increase in telescope size requires significant computational power. For this reason other hardware technologies must be taken into account during the development of a specific processor. In this paper, an improvement on the efficiency of the above methods is proposed based on Field Programmable Gate Array (FPGA) technology. To the best of our knowledge, there are not other wavefront reconstruction implementations based on FPGA technology. The basic advantages of this technology are its flexible architecture and extremely highperformance signal processing capability which are captured through parallelism. The implemented phase recoverer is, consequently, faster than the CPU or the GPU solution. Furthermore, the implemented design incorporating this technology meets current and future adaptive optics image processing frame rate requirements. Keywords: Adaptive optics, FPGA, Phase recovery, Fast fourier transform, DSP