Simulation of anisoplanatic imaging through optical turbulence using numerical wave propagation with new validation analysis

Abstract

, "Simulation of anisoplanatic imaging through optical turbulence using numerical wave propagation with new validation analysis," Opt. Eng. 56(7), 071502 (2017), doi: 10.1117/1.OE.56.7.071502. Abstract. We present a numerical wave propagation method for simulating imaging of an extended scene under anisoplanatic conditions. While isoplanatic simulation is relatively common, few tools are specifically designed for simulating the imaging of extended scenes under anisoplanatic conditions. We provide a complete description of the proposed simulation tool, including the wave propagation method used. Our approach computes an array of point spread functions (PSFs) for a two-dimensional grid on the object plane. The PSFs are then used in a spatially varying weighted sum operation, with an ideal image, to produce a simulated image with realistic optical turbulence degradation. The degradation includes spatially varying warping and blurring. To produce the PSF array, we generate a series of extended phase screens. Simulated point sources are numerically propagated from an array of positions on the object plane, through the phase screens, and ultimately to the focal plane of the simulated camera. Note that the optical path for each PSF will be different, and thus, pass through a different portion of the extended phase screens. These different paths give rise to a spatially varying PSF to produce anisoplanatic effects. We use a method for defining the individual phase screen statistics that we have not seen used in previous anisoplanatic simulations. We also present a validation analysis. In particular, we compare simulated outputs with the theoretical anisoplanatic tilt correlation and a derived differential tilt variance statistic. This is in addition to comparing the long-and short-exposure PSFs and isoplanatic angle. We believe this analysis represents the most thorough validation of an anisoplanatic simulation to date. The current work is also unique that we simulate and validate both constant and varying C 2 n ðzÞ profiles. Furthermore, we simulate sequences with both temporally independent and temporally correlated turbulence effects. Temporal correlation is introduced by generating even larger extended phase screens and translating this block of screens in front of the propagation area. Our validation analysis shows an excellent match between the simulation statistics and the theoretical predictions. Thus, we think this tool can be used effectively to study optical anisoplanatic turbulence and to aid in the development of image restoration methods. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

Synthesis of atmospheric turbulence point spread functions by sparse and redundant representations

“…Previous synthesis methods of PSFs for turbulent atmospheric conditions use a C 2 n profile and wave propagation software to propagate a random wavefront perturbation of Zernike polynomial coefficients. 3,12,14 This is computationally intense. The synthesis procedure presented in Fig.…”

“…1. Modeling and simulating the effects of turbulence on imagery is typically done with wave propagation approaches, such as in Hardie et al 3 Another approach is to use Zernike polynomials as basis functions 4 to model turbulence in the entrance pupil. Modeling approaches allow for a better understanding of how turbulence affects imagery and are an integral part of inverse modeling methods for mitigation.…”

Scalability conjecture for the Fried parameter in synthesis of turbulent atmosphere point spread functions

“…These statistical representations of turbulence effects are well established in modeling. 4 The short exposure can contain higher spatial frequency content, i.e., instantaneous amplitude and phase information, and is used in mitigation techniques such as the bispectral speckle technique 5 or the block-matching Wiener filter 6 to help estimate the spatially variant PSF used in the deconvolution step. These mitigation techniques, along with others, such as phase diversity and "lucky-look" imaging, all attempt to remove the effects of turbulence in imagery, which leads to stabilized imagery with improved resolution to see smaller details in imagery.…”

Year in Review

“…Four additional top-downloaded papers were review papers on laser feedback interferometry, 4 head-mounted displays for air transportation, 5 terahertz photoconductive antenna technology, 6 and conformal displays. 7 The final three in the top-ten download list included special section papers on white light interferometric microscopy 8 and anisoplanatic imaging through turbulence, 9 along with a regular paper on laser-induced damage of camera sensors. 10 All of these papers are available with open access, which is a likely factor in the high number of downloads.…”

“…According to the Web of Science, three were in the laser damage special section, describing laser damage tests for femtosecond laser coatings, 11 laser-induced damage by picosecond pulses on petawatt-class laser coatings, 12 and laser-based removal of space debris. 13 The active electro-optical sensing special section included top-cited papers on hyperentanglement 14 and deep turbulence wavefront sensing, 15 while papers on anisoplanatic imaging through turbulence 9 (the only top-ten downloaded and cited) and atmospheric turbulence mitigation algorithms 16 from the long-range imaging special section were part of the list. The remainder included a paper on extended wavelength infrared photodetectors 17 from the infrared detectors special section, along with regular papers on binary holograms for depth visualization 18 and channel capacity of optical data links.…”