Bandwidth specification for adaptive optics systems*

Greenwood, Darryl P.

doi:10.1364/josa.67.000390

Cited by 268 publications

(124 citation statements)

References 1 publication

Supporting

Mentioning

120

Contrasting

Unclassified

Order By: Relevance

“…The refractive index structure constant is used to describe the atmospheric turbulence profile with altitude. Generally, the value of 2 n C near the ground in warm climate 1 varies between 14 10 − and 12 2/3 10 − − m . Once Fried parameter is measured, 2 n C can also be estimated under the approximation of horizontal propagation using Eqn.…”

Section: Mathematical Formulationmentioning

confidence: 99%

“…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] . This has been employed to determine the bandwidth of an adaptive optics system 11 .…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

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

et al. 2018

View full text Add to dashboard Cite

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.

show abstract

Section: Mathematical Formulationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

et al. 2018

View full text Add to dashboard Cite

show abstract

“…The coherence time (Greenwood 1977), τ 0 (s), is roughly the time taken for the wind to move turbulence by r 0 . This is given by…”

Section: Turbulence Parametersmentioning

confidence: 99%

Characterisation of the Optical Turbulence at Siding Spring

Goodwin

Jenkins

Lambert

2013

Publ. Astron. Soc. Aust.

View full text Add to dashboard Cite

Measurements of the optical turbulence profile above Siding Spring Observatory were conducted during 2005 and 2006. This effort was largely motivated by the need to predict the statistical performance of adaptive optics at Siding Spring. The data were collected using a purpose-built instrument based on the slope detection and ranging (SLODAR) method where observations of a bright double star are imaged by Shack-Hartmann taken with the Australian National University 24-inch and 40-inch telescopes. The analysis of the data yielded a model consisting of a handful of statistically prominent thin layers that are statistically separated into the ground layer (37.5, 250 m) and the free atmosphere (1, 3, 6, 9, 13.5 km) for good (25%), typical (50%), and bad (25%) observing conditions. We found that ground-layer turbulence dominates the turbulence profile with up to 80% of the integrated turbulence below 500 m. The turbulence tends to be non-Kolmogorov, especially for the ground layer with a power-law index of β ß 10/3. The mirror/dome seeing can be a significant fraction of the ground-layer turbulence. The median atmospheric seeing is around 1.2 arcsec, in agreement with observational reports.

show abstract

“…The isoplanatic angle v 0 is the field angle over which phase fluctuations are coherent (Fried 1982). The Greenwood frequency is inversely proportional to the maximum temporal f G separation over which phase fluctuations are coherent (Greenwood 1977). However, hardware problems in PAODMS caused the isoplanatic angle data to be declared potentially invalid during this period.…”

Section: Correlationsmentioning

confidence: 99%

Scintillation Correlations in the Near‐Infrared

Ryan¹

2002

PUBL ASTRON SOC PAC

View full text Add to dashboard Cite

ABSTRACT. Stellar scintillation has been measured from 0.9 to 1.7 mm over a wide range of elevation angles. The pupil from a 3.5 m telescope was imaged onto a mask with four circular apertures of scaled diameters 0.1, 0.2, 0.75, and 1.5 m, which were, in turn, reimaged onto InGaAs photodiodes digitally sampled at 10 kHz. The entire 3.5 m pupil was also imaged onto a fifth photodiode. Since all five fluxes were recorded simultaneously, the influence of aperture diameter on scintillation statistics can be readily seen. Atmospheric phase aberrations did not affect the results because the detectors were located at pupil planes. Comparisons of a large number of fluctuation statistics have been made as functions of the aperture diameter, atmospheric parameters, and elevation angle. Experimental results and theoretical expectations reveal widespread agreement. Within experimental error, lognormal statistics are followed. Scintillation in the near-IR has been shown to produce consistent results with previous studies performed at visible wavelengths.

show abstract

Bandwidth specification for adaptive optics systems*

Cited by 268 publications

References 1 publication

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

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

Characterisation of the Optical Turbulence at Siding Spring

Scintillation Correlations in the Near‐Infrared

Contact Info

Product

Resources

About