System and method of generating atmospheric turbulence for testing adaptive optical systems
Inventors
Wilcox, Christopher C. • Restaino, Sergio R • Martinez, Ty • Teare, Scott W
Assignees
US GOVERNMENT IN NAME OF SECRETARY OF NAVY • US Department of Navy
Publication Number
US-8452574-B2
Publication Date
2013-05-28
Expiration Date
2030-02-02
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Abstract
A system and method for simulating atmospheric turbulence for testing optical components. A time varying phase screen representing atmospheric turbulence is generated using Karhunen-Loeve polynomials and a splining technique for generating temporal functions of the noise factor for each Zernike mode. The phase screen is input to a liquid crystal spatial light modulator. A computer display allows the user to set geometric characteristics, and select between methods for generating atmospheric turbulence including Karhunen-Loeve polynomials, Zernike polynomials, and Frozen Seeing.
Core Innovation
The invention provides a system and method for simulating atmospheric turbulence for testing optical components and systems by generating a time-varying phase screen representing atmospheric turbulence using Karhunen-Loeve polynomials combined with a splining technique to generate temporal functions of the noise factor for each mode. This phase screen is then input to a liquid crystal spatial light modulator, dynamically modulating the phase of an incoming wavefront to simulate atmospheric aberrations.
The system includes a computer processor with instructions to generate the time-varying wavefront as a weighted sum of Karhunen-Loeve polynomials and temporal noise functions generated by spline curve fits to sequences of random numbers, weighted with aberration amplitudes determined based on Zernike-Kolmogorov residual errors for each mode. Users can select geometrical parameters and between different turbulence simulation methods including Karhunen-Loeve, Zernike polynomials, and Frozen Seeing, through a graphical interface.
The problem addressed by the invention is the difficulty, computational intensity, and expense associated with creating realistic laboratory atmospheric turbulence simulations for calibrating and characterizing adaptive optics systems. Existing methods using static holographic phase screens or rotating aberrators are costly and inflexible, and atmospheric turbulence is inherently dynamic and random, making accurate simulation challenging.
Claims Coverage
The patent includes a total of 15 claims with independent claims focusing on a computer implemented method, an optical testbed system, and a non-transitory machine readable storage medium. Three primary independent claims define the invention's scope by detailing the generation and application of time-varying wavefronts representing atmospheric turbulence using Karhunen-Loeve polynomials, spline-generated temporal noise functions, and aberration amplitudes based on Zernike-Kolmogorov residual errors.
Generating time-varying wavefront using Karhunen-Loeve polynomials and spline-generated temporal noise
A computer implemented method generating a time-varying wavefront representing atmospheric turbulence as input for a liquid crystal spatial light modulator. The wavefront is calculated at each location and time as a summation over modes of a product of Karhunen-Loeve polynomials, a temporal noise factor derived from a spline curve fit to random numbers, and aberration amplitudes determined from Zernike-Kolmogorov residual errors. The method outputs the wavefront as a sequence of phase screens.
Optical testbed system for evaluating optical components with user-selectable turbulence methods
A system comprising a computer processor with instructions to generate time varying wavefronts as weighted sums of Karhunen-Loeve polynomials and spline-fitted temporal noise functions, weighted by aberration amplitudes from Zernike-Kolmogorov residual errors. The system includes a user input device for selecting variables and methods of turbulence generation (Zernike, Karhunen-Loeve, Frozen Seeing), a liquid crystal spatial light modulator for phase modulation, optionally a Fourier filter, wavefront sensors, and a display for output visualization.
Machine readable storage medium with instructions for turbulence simulation
A non-transitory machine readable medium storing instructions to receive user input and calculate time varying wavefronts representing atmospheric turbulence as weighted sums of Karhunen-Loeve polynomials with spline-generated temporal noise functions, weighted by Zernike-Kolmogorov residual error-based aberration amplitudes, then outputting the wavefront to a liquid crystal spatial light modulator. It includes user options for method selection and simulation parameter input, including secondary obscuration addition.
The claims collectively cover computer-implemented methods, an optical testbed system, and software media for simulating atmospheric turbulence by generating time-varying phase screens using Karhunen-Loeve polynomials combined with spline-interpolated temporal noise and Zernike-Kolmogorov aberration amplitudes, providing user control over simulation methods and parameters, and applying the phase screens via liquid crystal spatial light modulators for optical testing purposes.
Stated Advantages
Simulates atmospheric turbulence more inexpensively and with greater fidelity than prior methods.
Allows dynamic generation and quick modification of atmospheric turbulence simulations.
Supports multiple simulation algorithms for comparison, including Karhunen-Loeve, Zernike polynomials, and Frozen Seeing.
Provides realistic temporal wavefront transitions using spline curve fitting for smooth continuous changes, improving accuracy over discontinuous phase screen changes.
Enables user control over geometric characteristics, aberration modes, and obscurations for customizable and comprehensive simulations.
Documented Applications
Testing and calibration of adaptive optics systems, including phase correction for telescopes and free space laser communication systems.
Evaluation of optical components under simulated turbulent atmospheric conditions in optical testbeds.
Simulation and generation of atmospheric seeing conditions to test imaging systems.
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