In-flight measurement of atmospheric-imposed tilt: experimental results and analysis

Kalensky, Matthew; Jumper, Eric J.; Kemnetz, Matthew R.; Gordeyev, Stanislav

doi:10.1364/ao.460717

Cited by 11 publications

(8 citation statements)

References 18 publications

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“…* Similar phenomena was observed in Refs [40,42]. for the case of shock-induced-phase aberrations across the SHWFS's lenslet pupils.Proc.…”

supporting

confidence: 73%

Branch-point detection using a Shack-Hartmann wavefront sensor

Kalensky,

Oesch,

Bukowski

et al. 2023

Unconventional Imaging, Sensing, and Adaptive Optics 2023

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In this paper, two methods for identifying branch points from Shack–Hartmann wavefront sensor (SHWFS) measurements were studied; the circulation of phase gradients approach and the beam-spread approach. These approaches were tested using a simple optical-vortex model, wave-optics simulations, and with experimental data. It was found that these two approaches are synergistic regarding their abilities to detect branch points. Specifically, the beam-spread approach works best when the branch point is located towards the center of the SHWFS’s lenslet pupil, while the circulation of phase gradients approach works best when the branch point is located towards the edge of the SHWFS’s lenslet pupil. These behavior were observed studying the simple optical-vortex model; however, they were further corroborated with the wave-optics and experimental results. The developments presented within support researchers looking to study high scintillation optical-turbulence environments as well as will inform efforts looking to develop branch-point tolerant reconstruction algorithms.

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“…* Similar phenomena was observed in Refs [40,42]. for the case of shock-induced-phase aberrations across the SHWFS's lenslet pupils.Proc.…”

supporting

confidence: 73%

Branch-point detection using a Shack-Hartmann wavefront sensor

Kalensky,

Oesch,

Bukowski

et al. 2023

Unconventional Imaging, Sensing, and Adaptive Optics 2023

Self Cite

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“…where ẑ is the propagation path direction. 12,40 The OPD is the result of removing the spatial mean (or piston) from the OPL, given by E Q -T A R G E T ; t e m p : i n t r a l i n k -; e 0 0 3 ; 1 1 7 ; 3 6 7 OPDðx; y; tÞ ¼ OPLðx; y; tÞ − OPLðx; y; tÞ:…”

Section: Optical Propagation Through a Shear Layermentioning

confidence: 99%

Experimental and computational investigation of Shack–Hartmann wavefront sensor measurements through a free shear layer

Wells,

Kalensky,

Rennie

et al. 2024

Opt. Eng.

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Experimental Shack-Hartmann wavefront sensor (SHWFS) measurements were collected for a laser beam that propagated through a weakly compressible shear layer. Complementary computational fluid dynamics (CFD) was also conducted to match the experiment. The path-integrated CFD results were then applied to a SHWFS model such that the experimental and CFD results could be compared. Using both the experimental and CFD wavefront results, it was found that, although the CFD results slightly overestimated the resultant wavefront error, the CFD and experimental results revealed extremely similar wavefront topology. In order to further examine the aberrations imposed onto the laser beam in both datasets, the SHWFS image-plane irradiance patterns and circulation of phase gradients were studied. Similar to the overall wavefront topology, these data reduction approaches revealed similar phenomena in both the experimental and CFD-modeled results. Specifically, appreciable circulation and beam spread of the SHWFS image-plane irradiance patterns were exhibited throughout the shear layer's braid region. Both of these findings suggest that sharp phase gradients exist in the weakly compressible shear layer and both (1) the SHWFS resolution and (2) the continuous nature of the phase estimate obtained using SHWFS data in a least-squares reconstruction algorithm make these phase gradients challenging to resolve. The findings presented here inform efforts looking to experimentally or computationally study aero-optical environments.

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“…However, for experimental SHWFS measurements, we recognize that turbulence-induced tip, tilt, and piston are always corrupted with mechanical contamination. [25][26][27] As such, it is customary to remove tip, tilt, and piston from the reconstructed OP D(x, y, t) field altogether. For this reason, we opt to use the tilt-removed phase variance given in Eq.…”

Section: Phase Variancementioning

confidence: 99%

Optical-turbulence characterization of a littoral test environment using a Shack-Hartmann wavefront sensor

Bukowski,

O'Sullivan,

Kalensky

et al. 2023

Unconventional Imaging, Sensing, and Adaptive Optics 2023

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Beam propagation systems are often used in a wide range of atmospheric environments. Therefore, it is important to be able to characterize those environments in order to appropriately assess performance and inform design decisions. In this paper, a variety of methods for measuring atmospheric coherence length, r0, were analyzed including a Shack–Hartmann-based differential image motion monitor (DIMM), gradient-tilt variance, slope discrepancy variance, and phase variance methods, as well as using the modulation transfer function (MTF). These methods were tested on varying turbulence strength environments with known atmospheric coherence lengths, first using a single modified von Kármán phase screen, then using full wave-optics simulations with 20 phase screens. The Shack–Hartmann based approaches were shown to greatly increase in error for d/r0> 1 due to discrepancies between gradient tilt and the centroid tilt measured from the SHWFS’ image-plane irradiance patterns. An atmospheric data collection system was built and experimental results were taken for a beam propagating 2.4 km through a littoral environment over a 24 hour period.

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In-flight measurement of atmospheric-imposed tilt: experimental results and analysis

Cited by 11 publications

References 18 publications

Branch-point detection using a Shack-Hartmann wavefront sensor

Branch-point detection using a Shack-Hartmann wavefront sensor

Experimental and computational investigation of Shack–Hartmann wavefront sensor measurements through a free shear layer

Optical-turbulence characterization of a littoral test environment using a Shack-Hartmann wavefront sensor

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