Fresnel-style collar?

Can’t sleep this night. Thinking about stuff I came up with an idea. It may not be new. It may be fundamentally flawed. I should think it through while being less tired before posting. But I’ll write it now anyway….
If I understand it correctly, with reflective collars, size matters. The larger the collar, the more effective it is at pointing the light back towards the die.
But, obviously, head’s internal diameter is a limitation. You can’t put a hemisphere larger than inside.
But you can put a fragment of it.
The idea is to have a reflector consisting of sections of spheres. At the bottom of the head, the section would have the (external) diameter of the head’s IR. Closer to the front you could put a section of a larger one. And another. And so on.

Would it work? Would it work better than a plain hemisphere?

You’re talking about making a fresnel style waiven collar.

Im not sure that would work. A waiven collar is a perfect hemisphere. All the light that hits the inside of the collar reflects back to the die, except for the portion that exits the hole in the top of the collar to hit the lens. I’m not sure it actually matters how big the collar is … the amount of light reflected back ought to be the same.

The advantage of using fresnel-like steps would be to get the effect of a sphere on a flat surface.

I suppose you could make an interesting zoomie this way: Build a zoomie with aspheric lens and sliding bezel. instead of having a waiven collar over the LED, have the collar built in stair-steps along the sides of the inside of the sliding bezel. Sounds like a lot of effort though.

No, light would be reflected back if the LED was a single point. Since its size is finite, some light is reflected non-perpendicularly. Furthermore, the cutoff at the edge of opening is not sharp.
Increasing size reduces both effects.

Thinking about zoomie is actually the source of the idea, though I contemplated a conventional collar combined with an auxiliary bezel-mounted one to slightly improve collection efficiency while maintaining small height….

Not really, with collars size doesn’t make much of a difference, just a few percent.
The larger the collar is, the less significant effect that surface imperfections make.

With something like a wavien collar made out of precision cold mirror glass, there are very few imperfections and the small collar performs very close to the large collar.

Yes your idea would work, however making that type of optic would be extremely complex, and just like a fresnel lens, would perform much worse than an optic made with a single curved surface.

OK, thanks for the assessment. I hoped you would comment. :slight_smile:

I’m glad there’s still people thinking of creative ideas like this :slight_smile: That’s how innovation happens.