I recently watched the video https://www.youtube.com/watch?v=l32_QbcdUiw on optical interferometry. It had an ‘easy exercise for the careful listener’.

Below my simulation of the 4 cases: The yellow line is the lens. The blue pattern is the simulated interference pattern

Option A & B are the concave lenses. Options C & D the convex lenses. In figure A we see the fast phase trend in front of the bulge, with a low phase trend behind it. These are not visible in the three other options. However: the difference between A & C (concave vs convex) is not necessarily easy to spot in this simulation. To figure that out very likely the 2D interferogram has to be looked at to figure out which lines are ‘pulled straight’

All in all: great video which inspired me to write some code.

The source code can be downloaded: PhaseOptics