DistortionNumber

MATLAB

[Nd,NdScreen,NdIpk,NdIpkScreen,NdPkShft,TransScaling] = ...
              DistortionNumber(lambda,Pwr,Focus,D,Type,S,Atm)
[Nd,NdScreen,NdIpk,NdIpkScreen,NdPkShft,TransScaling] = ...
              DistortionNumber(Laser,S,Atm)

Description

DistortionNumber calculates the thermal blooming distortion number (Nd) for a propagation path with specified absorption, scattering, and temperature models. If the input atmospheric model is continuous, Nd represents the integrated effect of thermal blooming, and NdScreen = []. If the input atmospheric model is discrete, Nd is computed by summing the distortion numbers for each phase screen slab as given in NdScreen. The calculation of Nd is well-documented in literature. NdIpk is a scaling parameter anchored to wave optics for estimation of peak irradiance due to thermal blooming. NdPkShft is a scaling parameter for estimation of the amount of peak shift observed in wave optics. Calculation of NdIpk and NdPkShft is based on empirical relations and may not hold in general. Relations for NdIpk and NdPkShft have not yet been developed for Type 'GAUSSIAN.' Function is valid for both collimated beams as well as focused beams. It uses the AtmStruct function to obtain the absorption and scattering coefficients (1/m), Temp (K) and Wind (meters/sec). Refractive index variation in altitude follows the expressions given by Paul J. Berger, "ABLE Code: Description and Anchoring to ABL WOPM Wave-Optics Code Results," Memorandum VVA-LL-016, Rev C, June 22, 2003

Parameters

Parameters	Description
Laser [struct]	Structure from LaserField or a comma-separated list of (lambda,Pwr,Focus,D,Type,...)
lambda [scalar]	Wavelength of laser (m)
Pwr [scalar]	Total power of laser through link (W)
Focus [scalar]	Range at which laser beam is focused (m)
D [scalar]	Starting diameter of laser (m)
Type [char]	Beam type, must be 'GAUSSIAN' or 'UNIFORM'
S [struct]	Structure of engagement geometry parameters as from EngagementStruct
Atm [struct]	Atmospheric modeling parameters from AtmStruct. Atm must have wind profile if calculation with wind is desired.

Return Values

Return Values	Description
Nd [scalar]	Integrated distortion number for the entire path
NdScreen [vector]	Distortion number for each phase screen
NdIpk [scalar]	Peak irradiance scaling parameter anchored to wave optics, used by ThermalBlooming
NdIpkScreen [vector]	Path weighted distortion number for each phase screen
NdPkShft [scalar]	Scaling parameter for estimating peak shift, anchored to wave optics, used by ThermalBlooming
TransScaling [vector]	Transmission weighting function used for calculation of NdIpk and NdIpkScreen

References

L. C. Bradley and J. Herrmann, Phase Compensation for Thermal Blooming, Appl. Opt., vol. 13, pp. 331-334, 1974.
A. M. Ngwele, "Scaling Law Modeling of Thermal Blooming in Wave Optics," MZA Technical Report, contract NGIT ABL A&AS, Nov 2010.