Back to the topic of moving the precollimator:
If you defocus the usual way, by moving the (precollimator) lens closer to the LED, you end up with light hitting the body. You can try to fix it by turning the body to a mirror. In my ray-traces it didnāt work - I ended up with a high internal reflection in the main lens.
If you defocus by moving the lens farther from the LED, itās about the same, the light hits the body again, this time by passing on the lens sides. You can make the precollimator larger, but it quickly gets counterproductive. But it can be fixed differently - by making a reflective precollimator assembly.
It will surely produce ring artefacts thoughā¦
Some traces:
Done optically right, it will make thermal path much longer as it needs the LED to stay on a long post. But the reflector doesnāt really need to have cover 360 degrees around the LED. We can make a couple of cut-outs that will transfer heat as well as reinforce the body.