I wanted to make a very basic proof of concept way to take both infrared and visible images with a single camera. The trick is that both images must be of the same thing, from the same angle. So I tried using a beamsplitter to split the image in two, and filter each half separately. It only kind of worked; I'll post what I got soon, but here is the setup:

The closeup above shows how the mirror and beamsplitter are set up to split the image in two and put the duplicates side by side.

I opened an old scanner to get some very nice first-surface mirrors (mirrors with a reflective surface in front of the glass), though really I'd have used any mirrors on hand: