Simulating a Fabry Perot Interferometer

[CasualDays]

I am making an attempt at simulating interference patterns of a Fabry Perot interferometer.

I have fully derived the transmission function and the coefficient of finesse.

T=\frac{I0 T^{2}}{(1-R)^2} + \frac{1}{1+FSin^2(\frac{\delta}{2})}

Where F=\frac{4R}{(1-R)^2} and \delta = \frac{2\pi}{\lambda} 2 n l Cos(\vartheta)

n=index of refraction of material between two half silvered mirrors
l=thickness of material between mirrors

I guess my question is..How does one draw an interferogram from the transmission equation?

For some reason, it just does not click with me on how you can see a circular ring from a difference in wavelength. I don't really understand which of the variables to assign arbitrary values too, and which to graph if you will.

I need help graphing the interferogram in Mathematica. I just want it to work!

 

[CasualDays]

I tried using Density Plot with this equation,letting theta approach zero, and tried varying t and I0 but still no luck.

For some reason, it doesn't seem very common to create fringe patterns digitally, or at least, I haven't really found any good info on it.

Probably help if I'd taken optics.. :D