Interesting, I've used something quite similar to the scanning-through-prism technology a few years ago, though with an 8-sided polygon for the application of exposing PCB masks. We were looking at 3D printing too IIRC.

To get to the desired ~80x80cm PCB size and the accuracy needed, we had to achieve super high throughput and super low timing jitter on the UV-LEDs. Very interesting technology, unfortunately we took too long to get a smaller scale proto working and funding was cut right after we delivered that proto :-(. Calibrating the whole machine from scratch was clever too.

Learned a lot there.