Plot of wave interference from interferometry.

Hi All,

I am looking for a way to simulate an interference image from a Twyman-Green interferometer. In the interferometer there is a flat mirror and a slightly curved mirror. Therefore the interference fringes are tighter together the farther from the center you get. I have yet not been able to replicate that decrease in interference period. I think I would need a for loop that iterates through the phase differences caused by the path difference. Yet I am unsure where to start with that. Or possibly a way to mathematically express a spherical wavefront and have that interfere with the plane wavefront? Any suggestions? Here is what I have so far.

[X,Y] = meshgrid(x,y); % create rectangullar mesh
x=-30:0.5:100; %axis
y=-30:0.5:30; %axis
phi = 4; %phase
k = 1; % wave vector
R = sqrt(X.^2+Y.^2); %rasius
f1 = sin(k*R - phi)
f2 = sin(k + phi);
Z = f1 + f2;
surf(X,Y,Z);
axis equal;

Thanks for anyone's help.