% This is for Project 2.
% Spatial filtering

% Model the spatial filter as a Gaussian wave multiplied by 
% 3 rect functions to model the spatial noise

x=linspace(-2e-3,2e-3,6001);
W=1e-3;   %diameter of 1 mm
F=0.49;
period=500e-6;
f=16e-3;
l=670e-9;

slit=zeros(size(x));
for m=-20:20
    I=find(abs(x-m*period)<F*period)
    slit(I)=ones(size(I));
end

subplot(2,1,1)
G=exp(-(x/W).^2);
plot(x*1e3,(slit.*G).^2)
ylabel('Irraddiance at lens')
xlabel('position, x (mm)')

x=linspace(-1e-4,1e-4,6001);
subplot(2,1,2)
E=0;
for n=-20:20
    E=E+sinc(F*n)*exp(-(W*pi/(l*f)*(x-n*l*f/period)).^2);
end
plot(x*1e6,E.^2)
ylabel('Irraddiance at focus')
xlabel('position, x (\mum)')