Should I aim for straight or circular fringes in a Michelson interferometer?
I’m building a Michelson interferometer with a HeNe laser to measure the interferogram on a single Si photodiode. The only lens in the setup is placed after the beam splitter, in the detection arm. With my current alignment, the interference pattern on a screen is a set of straight, parallel fringes, and the photodiode sits in that field to record intensity as I scan one arm.
For a quantitative measurement (i.e., determining the laser wavelength), is there any advantage to having a circular fringe pattern instead of straight fringes?
My understanding is that, as long as the photodiode is small compared to the local fringe spacing and sees a clean modulation from bright to dark as I scan the path length, the global shape of the fringes (circular vs straight) shouldn’t matter.