Accession Number : ADA018045

Title :   Power Spectra Requirements for Wavefront-Compensative Systems.

Descriptive Note : Final rept. 1 Jun 73-1 Jun 75,


Personal Author(s) : Fried,David L. ; Greenwood,Darryl P.

Report Date : SEP 1975

Pagination or Media Count : 132

Abstract : The phase degradation of an optical wavefront distorted by turbulence in the propagation medium may be corrected in a piece-wise-linear fashion by using an array of small circular mirrors. An option in the correction scheme is to compensate for overall tilt separately. The authors have evaluated power spectra and variances of the piston and tilt motions of the mirror segments as well as the motion of the overall tilt corrector. The form of the spectra for any propagation medium is an aperture integral of the product of the phase-difference power spectrum, describing the medium, and a generalized transfer function, representing the aperture and its segments. A set of standard curves is found to represent a generalized slice, and the differential contributions may be summed to represent any propagation path. The standard curves, further modeled in terms of power law dependencies, are programmed for use on a desk calculator. For a generalized turbulence and velocity model representing the ARPA Maui Optical Station, power spectra and variances are evaluated using both exact numerical integration and power law modeling.

Descriptors :   *Laser beams, Atmospheric motion, Turbulence, Power spectra, Wavefronts, Mirrors, Phase, Transfer functions, Integral equations, Numerical integration, Computations, Distortion, Fourier transformation, Adaptive systems

Subject Categories : Atmospheric Physics

Distribution Statement : APPROVED FOR PUBLIC RELEASE