Re: Focusing flashlights need a second look
The LED Lenser Police-Tech focus (also known as Hokus Fokus) apprantly has a very good flood/spot transition.
Yes. Known in the USA as the Coast LED Lenser Focusing (aka Coast Focusing Lenser) model # 7438. FlashCrazy does a pretty brisk business modding them with Seoul Semiconductor P4's. It uses an optic which combines a focusing lens with a TIR (total internal reflection) reflector and it changes focus by moving this optic relative to the emitter.
In "throw" mode, you don't really get the traditional tight center hotspot with a lighter ring of spill like you do with a normal reflector. Instead you get a medium-wide hotspot with little sidespill. It takes all those "lost" lumens normally in the large-area sidespill, and pulls them back toward the center thus increasing brightness. Most people who have seen a Focusing Lenser are pretty impressed.
In "wide" mode, the center hotspot disappears literally to the point where there is a small center dark spot instead, and the sidespill area widens. Whitewall hunters are critical of the appearance of the dark spot but in real-world use it's simply not an issue. I use my Focusing Lenser as a bicycle light, in wide-focus mode, and it does a fantastic job.
Now, to make a "perfect" focusing system, what you really need is a pliable reflector or optic, that can be stretched or morphed or whatever you want to call it so it achieves the optimum geometry for both tight and wide focus and presumably everywhere in between (or, maybe, the transistion zone is actually a separate issue). That's pretty tricky; making a reflector out of Silly Putty. Got some room here for a very clever and patentable invention. Another approach is simply to optimize the reflector/optic for the throw pattern, then just diffuse it for flood-mode. FASTCAR claims to have done a bunch of legwork to locate an optimum diffuser material, but he seems to be keeping the identity a secret (at least as far as I understand). Separate issue - I wonder out loud whether there's some sort of liquid-crystal approach to diffusion, so it can be turned on and off electrically vs. having a separate removable diffuser part.
