Imaging through Atmospheric Turbulence

Overview

Imaging through atmospheric turbulence is a fundamental problem for long-range imaging systems. Purdue i2Lab has specialities in several aspects of the subject:

  • Wave optics theory

  • Turbulence simulators

  • Forward imaging models that can be used for deep neural networks

  • Image reconstruction algorithms

  • Object recognition

Tutorial

Recordings



Purdue Atmospheric Turbulence Simulator

Phase-over-aperture model (Version 1)

 

Key Concept: Collapse screens and sample in the Zernike space. 20x speed up compared to split-step.

Publication:

Code:

  • MATLAB download: (URL)

  • Python download: (URL)

  • Licence: Copyright is granted for educational and research purposes. Please contact Prof Chan for licensing.

Project Page: project_turbulence_TurbSim_v1.html

Phase-to-space transform (Version 2)

 

Key Concept: Transform Zernike representation to PSF representation. 1000x speed up compared to split-step.

Publication:

Code:

  • Python download: (URL)

  • Licence: Copyright is granted for educational and research purposes. Please contact Prof Chan for licensing.

Project Page: project_turbulence_TurbSim_v2.html

Dense field phase-to-space transform (Version 3)

 

Key concept: Quantize and decouple Zernike mode and spatial mode to preserve wide sense stationarity. Enables full HD without interpolation.

Publication:

Code:

  • Proprietary. Contact Stanley Chan for license.

Turbulence Reconstruction

Classical optimization-based approach

 

Key concept: Lucky imaging + blind deconvolution

Publication:

Code:

  • MATLAB download: (URL)

  • Licence: Copyright is granted for educational and research purposes. Please contact Prof Chan for licensing.

Project Page: project_turbulence_Recon_v1.html

Single-Frame Turbulence Mitigation

 

Key concept: Re-blur the reconstructed image using a turbulence simulator

Publication:

Code:

Turbulence Mitigation Transformer

 

Key concept: Two-stage mitigation, transformer, temporal attention

Publication:

Theoretical Analysis

Tilt-then-Blur or Blur-then-Tilt

 

Key conclusion: Tilt + blur is the correct model

Publication:

Arbitrary Cn2 Profile

 

Key concept: Integrate Cn2 along the path instead of evaluating individual turbulence segments

Publication:

  • Nicholas Chimitt and Stanley Chan, ‘‘Anisoplanatic Optical Turbulence Simulation for Near-Continuous Cn2 Profiles without Wave Propagation’’, submitted.