Turbulence simulation for anisoplanatic imaging based on phase screens with experimental validation of differential tilt variances

Daniel Wegner

doi:10.1117/12.2600330

12 September 2021 Turbulence simulation for anisoplanatic imaging based on phase screens with experimental validation of differential tilt variances

Daniel Wegner

Author Affiliations +

Proceedings Volume 11866, Electro-Optical and Infrared Systems: Technology and Applications XVIII and Electro-Optical Remote Sensing XV; 118660H (2021) https://doi.org/10.1117/12.2600330
Event: SPIE Security + Defence, 2021, Online Only

Abstract

Air turbulence can be a major impairment source for long-range imaging applications. There is great interest in the assessment of turbulence mitigation techniques based on machine learning models. In general such models require lots of image data for robust training and validation. Experimental acquisition of image data in field trials is time-consuming and environmental conditions such as daytime and weather cannot be specifically controlled. Several methods for turbulence simulation have been proposed in recent years. Many of these are based on phase screens or models turbulent point spread functions (PSFs). Often simple turbulence models such as the Kolmogorov or Von Karman spectrum are used. Therefore these methods cannot provide insight in the influence and relevance of other turbulence parameters such as inner scale and (non-)Kolmogorov power slope. In this work a data fitting procedure for the determination of turbulence model parameters based on experimental data is shown. Hereby the Generalized modified Von Karman spectrum (GMVKS) is used. Differential tilt variances (DTV) are calculated from centroid displacements in video sequences of a recorded LED grid. Then the experimental data is fitted to theoretical expressions of DTV by numerical integration over the turbulence model. Image data was acquired in field trials on several days at the same location. Then a beam propagation method using Markov GMVKS phase screens with determined model parameters is used to generate a grid of PSF images which represent degradation for different viewing angles. For validation, DTVs based on centroid displacements of the simulated PSFs are calculated and compared with the corresponding measured data of LED centroid displacements and theoretical data. Cumulative distribution functions of the model parameters for all recording dates are provided to show the diversity of turbulence conditions. These can be used as prior knowledge for future turbulence simulations to include various model parameters and hence different conditions of image degradation. Finally the extensibility of the data fitting approach to other turbulence spectra, e.g. anisotropic spectra, is discussed.

Conference Presentation

Citation Download Citation

Daniel Wegner "Turbulence simulation for anisoplanatic imaging based on phase screens with experimental validation of differential tilt variances", Proc. SPIE 11866, Electro-Optical and Infrared Systems: Technology and Applications XVIII and Electro-Optical Remote Sensing XV, 118660H (12 September 2021); https://doi.org/10.1117/12.2600330

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