Cool, thank you! Yes, I know that light may leak / scatter and that I’m giving up about half the signal. I’m hoping that that isn’t too bad for a bit better than a “hobby” microscope, but in any case it’s good to hear that it’s not a complete dealbreaker.
Pi GPIO pins are 16 mA source/sink, so that’s not going to be great for illumination, but I’ll figure something out-- probably just a mechanical switch to keep things simple.
Thanks again!