Optics and Optical Design - Why Does a Michelson Interferometer have a Bull's-Eye Interference Pattern (sometimes)?

Finding only hand-wavy explanations, I needed to figure out my own answer to this question. Using ray trace software, I simulate what it is about a Michelson interferometer that can give a Bull's-eye pattern, and why you can also get parallel (a.k.a Fizeau) fringes. There is nothing new about this and I'm sure that there are other resources providing their own illustrative explanations. Here, you will get my explanation, along with a demonstration using Zemax OpticStudio in nonsequential mode. Please remember to click "Like" so that I know what sort of content is being appreciated. I don't ask for support for developing this content, just the satisfaction of knowing that it is appreciated. More interferometer fringe curiosity: https://www.youtube.com/watch?v=RRi4dv9KgCg OpticStudio is a product of Zemax (www.zemax.com) #Michelson #MichelsonInterferometer