Power spectra requirements for wave-front-compensative systems*

Greenwood, Darryl P.; Fried, David L.

doi:10.1364/josa.66.000193

Cited by 101 publications

(25 citation statements)

References 13 publications

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“…In their joint paper on power spectra for corrective systems, Fried and Greenwood [29] found that the mean-squared phase variance over an aperture of diameter D with piston correction (or in an application where mean piston is irrelevant) would be…”

Section: Parameters Of Characterizationmentioning

confidence: 99%

“…In their paper on the spectral requirements of corrective systems, [29] Greenwood and Fried also considered the case of correcting piston and T/T over the entire aperture before providing localized correction in sub-sections of the aperture. In doing so they found that the average residual error, in the form of rms phase variance over the aperture after correction, (a^) would be after correction of both piston and T/T.…”

Section: Application Atmospheric Propagationmentioning

confidence: 99%

“…A developed shear layer is effectively a two-dimensional flow, and in such flows energy tends to transfer from small scales to large. [29] Shear layers do eventually become threedimensional, and thereafter quickly break down in the manner predicted by the Kolmogorov model. However, this may not occur until the structures are far downstream and out of the optical path.…”

mentioning

confidence: 99%

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Toward Adaptive Optic Mitigation of Aero-Optic Effects

Jumper¹

2009

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Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instrut maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate c suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information Operations Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be £ information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRL (From -To) When a laser beam propagates through a variable-index-of-refraction, turbulent fluid, its wavefront becomes aberrated, reducing associated optical-system performance. For flight Mach numbers as low as 0.3 Mach, turbulence in the flow past the aircraft become important in aberrating wavefronts (aero-optics). This report briefly reviews the mechanisms responsible for these aberrations in free-shear-layer flows. The report begins with describing an historic demonstration performed under this effort that combined the use of flow control and feed-forward adaptive optics to correct the aberrations imposed on an otherwise collimated laser beam projected through a heated jet and a Mach 0.8 free shear layer, respectively; this historic demonstration included a man in the loop. The report then describes the development of an automated control system that removes the man in the loop. Also described is some additional work performed under this grant that examined a spatial-filter approach to analyzing the effect of apertures on several aspects of laserbeam control. REPORT DATE (DD-MM-YYYY) 15-02-2009 REPORT TYPE FINAL REPORT DATES COVERED15 Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services. Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204. Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. REPORT DATE (DD-MM-YYYY) SPONSOR/MONITOR'S ACRONYM(S) SPONSOR/MONITOR'S REPORT NUMBER(S) DISTRIBUTION / AVAILABILITY STATEMENT UL SUPPLEMENTARY NOTES14. ABSTRACT This report describes aero-optic research at the University of Notre Dame. When a laser beam propagates through a variable-index-of-refraction, turbul...

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Section: Parameters Of Characterizationmentioning

confidence: 99%

Section: Application Atmospheric Propagationmentioning

confidence: 99%

mentioning

confidence: 99%

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Toward Adaptive Optic Mitigation of Aero-Optic Effects

Jumper¹

2009

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“…Various methods have been adopted to study the temporal spectra of phase-related quantities [11][12][13] . These include measurement of some relevant parameters such as angle-of arrival (AOA) fluctuations using image centroid motion 11,12 and variances of piston and tilt motions of the mirror segments of the corrector 13 . The temporal behaviour of turbulence has been extensively studied theoretically [14][15] .…”

Section: Introductionmentioning

confidence: 99%

Study of Wavefront Tilt Variance with Various Telescope Apertures in Indoor Convective Turbulence

et al. 2018

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Turbulent atmosphere produces random wavefront tilts in the propagating laser beam and the dynamics of turbulence largely depends on the receiving optics aperture size. In this paper, wavefront tilt variance is studied with various telescope aperture sizes in indoor convective turbulence. A simple experimental setup is described for simulating the near ground atmospheric turbulence by generating different strengths of convective turbulence in the laboratory. A laser beam is made to propagate through the turbulence subsequently induced wavefront tilt variances are experimentally measured and analysed statistically. The wavefront tilt variance is used to estimate the temporal characteristics using Fourier transform by varying aperture sizes and turbulence strengths (i.e. ambient, weak and moderate). The Hurst exponent, the Fried parameter and the wavefront tilt frequencies for the different turbulence strengths are calculated. The power dependence of the wavefront tilt variance on the telescope aperture size is studied and a deviation from the classical D -1/3 dependence is reported.

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“…This was more fully detailed in a technical report, which did not explicitly generalize the equation, but the authors clearly understood what the various terms signified [10].…”

Section: Introductionmentioning

confidence: 99%

Improved upper winds models for several astronomical observatories

Roberts¹,

Bradford²

2011

Opt. Express

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Abstract:An understanding of wind speed and direction as a function of height are critical to the proper modeling of atmospheric turbulence. We have used radiosonde data from launch sites near significant astronomical observatories and created mean profiles of wind speed and direction and have also computed Richardson number profiles. Using data from the last 30 years, we extend the 1977 Greenwood wind profile to include parameters that show seasonal variations and differences in location. The added information from our models is useful for the design of adaptive optics systems and other imaging systems. Our analysis of the Richardson number suggests that persistent turbulent layers may be inferred when low values are present in our long term averaged data. Knowledge of the presence of these layers may help with planning for adaptive optics and laser communications.

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Power spectra requirements for wave-front-compensative systems*

Cited by 101 publications

References 13 publications

Toward Adaptive Optic Mitigation of Aero-Optic Effects

Toward Adaptive Optic Mitigation of Aero-Optic Effects

Study of Wavefront Tilt Variance with Various Telescope Apertures in Indoor Convective Turbulence

Improved upper winds models for several astronomical observatories

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