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+%---------------------------------------------------------------
+% PROGRAM: AiryI_Fraunhofer
+% AUTHOR:  Andri M. Gretarsson
+% DATE:    1/30/06
+%
+%
+% SYNTAX: I=AiryI([a,L,lambda],r);
+%               <,...> indicates optional argument
+%
+% Returns the intensity of an Airy disk as a function of radius
+% in the Fraunhofer (small aperture) and paraxial (small angle)
+% limits.
+%
+% a      = radius of aperture
+% L      = propagation distance (axially) from aperture
+% lambda = wavelength
+%
+% Last updated: 1/30/06 by AMG
+%---------------------------------------------------------------
+%% SYNTAX: I=AiryI_Fraunhofer([a,L,lambda],r);
+%---------------------------------------------------------------
+
+function I=AiryI(params,r);
+
+a=params(1);
+L=params(2);
+lambda=params(3);
+k=2*pi/lambda;
+
+r=(r==0)*lambda/1000+r;  %Gives the limit of Bessel(1,r)/r as r->0  (can't evaluate BesselJ(1,0)/0).
+I=(2*BesselJ(1,k*a*r/L)./(k*a*r./L)).^2;
+
+%I is normalized to the intensity in the center.
+\ No newline at end of file