function [img_cleaned,img_fourier]=stripeeraser(img,radius,threshold_power)
% Cleans an image from the stripes produced by interference fringes.
% Such parallel fringes appears like a strong peak in the Fourier transformed image.
% so it easy to clean them, especially if their spatial frequency is high.
%
% We will clean strong frequency components higher them max*10^(-threshold_power)
% by suppressing them with exponential factor which is increases with distance
% from the center i.e. zero spatial frequencies.

img_fourier=fftshift(fft2(img)); % move to Fourier space
max1=max(abs(img_fourier(:)));
[Ny, Nx] = size (img); % image size
for x=1:Nx
    for y=1:Ny
        d=sqrt((x-Nx/2)^2+(y-Ny/2)^2);
        if d>radius                                                        
		% for high enough frequency components
		%The filter works like a neutral density filter. 
            if abs(img_fourier(y,x))>max1*(10^(-threshold_power));                       
		    % Suppress this frequency components which are mostly stripes
		    % but leave untouched small sharp features of the beam 
		    % since they are spectrally weak
		    img_fourier(y,x)=img_fourier(y,x)*exp(-(d/radius)^2);
            end;
        end;
    end;
end;
img_cleaned = abs( ifft2(ifftshift(img_fourier)) );