Imaging through Atmospheric Turbulence

Simulating atmospheric turbulence is an essential task for evaluating turbulence mitigation algorithms and training learning-based methods. Advanced numerical simulators for atmospheric turbulence are available, but they require evaluating wave propagation which is computationally expensive. In this paper, we present a propagation-free method for simulating imaging through turbulence. The key idea behind our work is a new method to draw inter-modal and spatially correlated Zernike coefficients. By establishing the equivalence between the angle-of-arrival correlation by Basu, McCrae and Fiorino (2015) and the multi-aperture correlation by Chanan (1992), we show that the Zernike coefficients can be drawn according to a covariance matrix defining the correlations. We propose fast and scalable sampling strategies to draw these samples. The new method allows us to compress the wave propagation problem into a sampling problem, hence making the new simulator significantly faster than existing ones. Experimental results show that the simulator has an excellent match with the theory and real turbulence data.

Publication

Nicholas Chimitt and Stanley H. Chan, ‘‘Simulating Anisoplanatic Turbulence by Sampling Correlated Zernike Coefficients’’, Optical Engineering, 59(8), 083101, July 2020.

Code

% Turbulence Parameters
D      = 0.2034;        % aperture diameter [m]
lambda = 0.525e-6;      % wavelength [m]
L      = 7000;          % propagation distance [m]
Cn2    = 1e-15;         % refractive index structure constant [m^{-2/3}]
d      = 1.2;           % focal length [m]
k      = 2*pi/lambda;   % wave number [m^{-1}]

Imaging through Atmospheric Turbulence

TurbSim v1: Multi-Aperture Simulator

Publication

Code

Demonstration