Journal ArticleDOI
Turbulence-degraded beam quality: improvement obtained with a tilt-correcting aperture
Reads0
Chats0
TLDR
The degradation in the focal-plane irradiance distribution due to atmospheric turbulence and the potential improvement realizable by employing a wavefront filt-correcting aperture are calculated and it is shown that the effective coherence length of the compensated aperture due to the residual amplitude fluctuations is greater than the long-term coherencelength.Abstract:
In this paper, we have calculated the degradation in the focal-plane irradiance distribution due to atmospheric turbulence and the potential improvement realizable by employing a wavefront filt-correcting aperture. It has been shown that, when the aperture diameter is of the order of the outer scale of turbulence, virtually no improvement is realized relative to the uncompensated case. For the case when the long-term coherence length is small compared with the diameter, there is a several-decibel improvement over the longterm case; however, for a full phase-compensating aperture (e.g., COAT), peak intensity can be increased an additional several decibels. When the coherence length is not much smaller than the diameter, close to diffraction- limited performance can be expected. Comparisons are also made of the reduction of on-axis intensity with no compensation, tilt-correction, and a full phase-compensating aperture. It is shown that the effective coherence length of the compensated aperture due to the residual amplitude fluctuations is greater than the long-term coherence length by a factor proportional to the square root of the Fresnel number of the aperture. Approximate formulas are also presented for the tilt-corrected MTF for arbitrary aperture irradiance distributions.read more
Citations
More filters
Journal ArticleDOI
Electromagnetic beam propagation in turbulent media: An update
TL;DR: In this article, the authors reviewed the recent developments on wave propagation in turbulent media, including adaptive optics, intensity scintillations, pulse propagation, atmospheric measurements at visible, IR, and millimeter wave frequencies, speckle interferometry, and other related topics.
Book ChapterDOI
VI Wave Propagation in Random Media: A System Approach
TL;DR: In this article, a review of the properties of electromagnetic wave propagation in a random medium in the limit when the random spatial inhomogeneities in the medium are large in comparison with the wavelength of the radiation and the magnitude of the index of refraction fluctuations (produced by these random inhomogenities) is small in comparison to unity.
Atmospheric propagation effects relevant to optical communications
TL;DR: In this paper, the effects of clear-air turbulence as well as atmospheric turbidity on optical communications are reviewed. But, the authors do not consider the effect of opaque clouds on the propagation of light.
Journal ArticleDOI
Long- and short-term Strehl ratios for turbulence with finite inner and outer scales
TL;DR: Corrections to the long- and short-term (tilt removed) Strehl ratios of a laser beam propagating through atmospheric turbulence are given for turbulence with finite inner and outer scales.
Journal ArticleDOI
Anisoplanatic short-exposure imaging in turbulence
TL;DR: In this paper, a new approximate formula for a short-exposure modulation transfer function is obtained, based on the path-integral representation of the field in a random medium, free of some of the drawbacks of previous approximations and describing the influence of diffraction effects and medium fluctuation distribution along the propagation path.
References
More filters
Journal ArticleDOI
Optical Resolution Through a Randomly Inhomogeneous Medium for Very Long and Very Short Exposures
TL;DR: In this article, the average resolution of very-long and very-short-exposure images is studied in terms of the phase and log-amplitude structure functions, whose sum is called the wave-structure function.
Journal ArticleDOI
Propagation of a Finite Optical Beam in an Inhomogeneous Medium
R. F. Lutomirski,H. T. Yura +1 more
TL;DR: The Huygens-Fresnel principle is extended to a medium that exhibits a spatial (but not temporal) variation in index of refraction, and the formula used is used to calculate the mean intensity distribution for a plane wave diffracting from a circular aperture and to give approximate expressions for the beam spreading at various ranges.
Journal ArticleDOI
Coherent Optical Adaptive Techniques
William B. Bridges,P. T. Brunner,S. P. Lazzara,T. A. Nussmeier,T. R. O’Meara,J. A. Sanguinet,W. P. Brown +6 more
TL;DR: The theory of multidither adaptive optical radar phased arrays is briefly reviewed as an introduction to the experimental results obtained with seven-element linear and three-element triangular array systems operating at 0.6328 microm.
Journal ArticleDOI
Physical model for strong optical-amplitude fluctuations in a turbulent medium
TL;DR: In this article, an estimate of the amplitude fluctuations that agree with the results of perturbation theory for σϒ2⪡1 and saturates to a constant value of the order unity for ϋT2⫢1 ( σT2 is the amplitude variance calculated on the basis of perturbing theory).
Journal ArticleDOI
Compensation for Atmospheric Phase Effects at 10.6 micro.
TL;DR: It is shown that the power delivered onto a target and thus the return signal can be significantly increased by the principle of adaptive phase-distortion compensation, and that large arrays can be utilized in spite of the distorting effects of the atmosphere.
Related Papers (5)
Short-term average irradiance profile of an optical beam in a turbulent medium
M. T. Tavis,Harold T. Yura +1 more