Right, ring is the right word :) (well, in the more perfect setup, I'd love to have more complex but based on the ring shapes, but ring would be a good a start)

Right, ring is the right word :) (well, in the more perfect setup, I'd love to have more complex but based on the ring shapes, but ring would be a good a start). LED+collimated lens and a mask sounds OK, but two questions: a) probably also need mirror, right? the device should be small and placed on the floor itself (you can't leave it or mount). b) mask is for, well, masking out the light from the center of the circle? Part of the challenge here is to make the ring as bright as possible (could be used in pretty bright environments), so ideally no light coming out from the optic system should be wasted (masked). Again, not sure it's even possible.