Randunu-Pathirannehelage, Nishantha

We are currently investigating a novel method, known as time-average Fourier telescopy
TAFT, for high-resolution imaging through the turbulent atmosphere. This method, which can be
applied to long-horizontal-path terrestrial imaging, addresses a need that is not solved by the
adaptive optics methods being used in astronomical imaging. Because experimental verification
of the method is quite complicated and requiring of considerable instrumentation, we are
developing a set of computer simulation tools that will allow us to establish the validity of the
underlying concept and to assess its limitations in ground-level imaging over distances of
kilometers to tens of kilometers.
The simulation tools, to be described in this poster presentation, allow us to model with high
accuracy the passage of light waves through typical ground-level turbulence and for large
distances. Preliminary results suggest that, at a minimum, TAFT will allow diffraction-limited
imaging with meter-scale optical apertures operating at distances exceeding a kilometer, a
capability that improves on that of conventional imaging by orders of magnitude.
In this poster we describe the basic scheme of simulation tools, atmospheric turbulence
modeling, split-steps Gaussian beam propagation, phase screen modeling, recent progress and
remaining challenges.

Fourier telescopy imaging is a recently-developed imaging method that relies on active
structured-light illumination of the object. Reflected/scattered light is measured by a large
“light bucket” detector; processing of the detected signal yields the magnitude and phase
of spatial frequency components of the object reflectance or transmittance function. An
inverse Fourier transform results in the image.
In 2012 a novel method, known as time-average Fourier telescopy (TAFT), was
introduced by William T. Rhodes as a means for diffraction-limited imaging through
ground-level atmospheric turbulence. This method, which can be applied to long
horizontal-path terrestrial imaging, addresses a need that is not solved by the adaptive
optics methods being used in astronomical imaging.
Field-experiment verification of the TAFT concept requires instrumentation that is not
available at Florida Atlantic University. The objective of this doctoral research program is thus to demonstrate, in the absence of full-scale experimentation, the feasibility of
time-average Fourier telescopy through (a) the design, construction, and testing of smallscale
laboratory instrumentation capable of exploring basic Fourier telescopy datagathering
operations, and (b) the development of MATLAB-based software capable of
demonstrating the effect of kilometer-scale passage of laser beams through ground-level
turbulence in a numerical simulation of TAFT.