But then there’s the issue of how to mix the two inputs. And also that they are necessarily 180 degrees orthogonal.
I think I want to make one of these. I think it would be fun to see what comes forward. The first thing that has come to mind is to make the two directions of observation adjustable. Perhaps from 90 degrees out to 180? Or further?
I suppose you could make one for any camera. Also, it could be made of acrylic or makerbot-stuff.