function [Eout] = NumLens (Ein,deltax,deltay,lambda,Rc)

[N,M]=size(Ein);
p=[(0:(M/2)-1) (-M/2:-1)];
q=[(0:(N/2)-1) (-N/2:-1)]';
[pp,qq]=meshgrid(p,q);
xx=pp*deltax;
yy=qq*deltay;
Eout=Ein.*exp(-1i*pi/(lambda*Rc)*(xx.^2+yy.^2));