Any such thing as a dispersion optic?

I might be able to make use of one if they exist.

All optics I've seen are designed to focus and direct light forward, but are there any that try to disperse light equally over a broad area? For example, to broaden the Cree's 75 degree beam angle?

I'd imagine they'd be useful for lanterns and area lighting.

Im sure just not really mas produced usually lanterns use multiple emitters or incand bulbs for full coverage. They cost mroe initially but the LED life and effieciency doesn't suffer.

Yes, there is such a thing.

Allthough I really like the tight hotspot of the HDS lights, some don't. Some CPFer had replacement lenses ground from optical quality polycarbonate which doubled the angle of the beam of HDS lights -- making the hotspot four times as big.

It was a very elegant solution as:

• Unlike an ordinary diffusion filter an actual lense that reshapes the beam will let more light through.

• An optical quality lense will change the tint of the beam less than many diffusion filters.

IMO if that's what you need to do an optic may be the best way to do it.

I stuck a piece of Scotch Matte finish Magic Tape over the lens of my P1. Drops the total light output only about 10% and gives a nice flood. And it's easily reversible.

c_c

The Cree XR-E has a 75 degree FWHM (full width half max), so it is 50% intensity at 75 degrees and about 15% at 100 degrees and about 10% at 170 degrees. That is what I call a wide beam!

The Seoul and Luxeon have the FWHM at about 125 degrees and they still have about 20% intensity at 160 degrees. Remember that the human eye can only detect about a +/- 25% difference in intensity.
-BH

Thanks for the info and suggestions! I'll have a chance to do some searching around tonight, and will post back if I dig up some kind of cool, manufactured solution.

Also trying to think up a slick homemade idea, if I can find anything good laying around the house to use.

Carclo and others have 6x25 (or whereabouts) degree optics.

Bimmerboy said:

Thanks for the info and suggestions! I'll have a chance to do some searching around tonight, and will post back if I dig up some kind of cool, manufactured solution.

Also trying to think up a slick homemade idea, if I can find anything good laying around the house to use.

Click to expand...

I just received some Carclo optics that are frosted--they might be what you are looking for, or not. Need to try for a beam shot tonight.

The frosting is vey faint, so I'm expecting a pretty diffused beam. Diameter is nominal 27mm.

Looking at Physical Optics now (very interesting stuff), and will check out Carlco next. Thanks, Green and McG.

Photon - Yes, beamshots!... or ambience shots rather... hehe. What are you using frosted Carlco's in?

BPH - Man, if the Seoul only had a hard shell, I wouldn't even be wondering about this. This thing I'm making (believe me, it qualifies as a "thing"... lol) will have the LED fully exposed in a dusty house... bad news for the SS.

Essentially, what I'm trying to do is simulate, as much as possible, the dispersion of an incan bulb in a lantern. It basically looks like a small table lamp, complete with lampshade. The lampshade will provide some of the effect, but a fair amount of the Cree's light will go straight up through the wide hole in the top of it. I'm hoping a diffuser will spread more light onto the shade's interior.

Placing the LED over an inverted cone will make a 360 degree light source. I have a lantern (and some night lights) that have a cone that looks like it has a parabolic curve to it. 360 degrees horizontally and wide angle (up/down) too.


Daniel

Inspiration and/or luck has not struck yet. Still searching. Neither the Physical Optics, nor the Carlco stuff really fit the imagined need ("imagined" being the key word here... lol).

Just remembered Cree makes optics. Will take a look, but not holding my breath for anything that completely disperses light all over the place.

I might have an idea or two that could work. Back to looking for random things around the house... heh.

Hmmm... I may have found the right optic for this application. Anyone have experience with these?

http://www.luxeonstar.com/l2-flare-optics.pdf

If this thing works the way I'm hoping, I'll have to get a Seoul to make the most of it, but this flare optic could be just the ticket!

Gadget Lover - The inverted cone idea is also a good one, but perhaps better for an outdoor lantern since upward facing light would be wasted. But for indoors, some light going up for ceiling bounce would probably be desireable. However, I'm not ruling out the cone yet. Thanks for the idea!

Edit: Nope. Never mind. Just realized exactly what a flare lens does. Back to the drawing board.

What is it that you want to do?

if used correctly, a magnifying glass or any convex lens can be used for light dispersion

enLIGHTenment said:

What is it that you want to do?

Click to expand...

To replicate, to whatever extent possible, the spherical dispersion of light of an incan bulb, from a Cree. That means light directed below the 180 degree plane of the LED itself.

I know the Cree is limiting the hell out out of this idea right off the bat, with it's 75 degree divergence. I keep going back to GL's inverted cone idea because it might really work well with the Cree, but only if I can scrounge one up from a donor light real cheap, and then try to make it fit in the lamp somehow. Otherwise, a Seoul P4 may be in order, so at least things are starting off with 180 degrees. How to keep the dust off it is another question.

What is all this nonsense about? I'm converting a 6V incan lamp to LED, and shooting for two goals... to make it super functional, and extremely ugly... lol. Should be a funny, but cool mod.

This probably isn't exactly what you're looking for, but my Petzl Tikka XP has a diffuser that slides over the lens to spread the beam out nicely - it has a bunch of little plastic hemispheres on one side that act like the convex lens Illum_the_nation mentioned. (It's talked about here: http://www.flashlightreviews.com/reviews/petzl_tikka_xp.htm)

I don't think this could get you > 180 degrees by itself, but if you used it in conjunction with a few LEDs facing away from each other...

What about 4 Crees mounted vertically in a square? Just drive them at a lower current to keep the power consumption down.

The multiple LED ideas would certainly help with throwing more light around, but unfortunately won't work with some of the parameters I'm limited to. One being the 6V power source. Not enough Vbatt to properly power more than one LED in series, and since a bFlex is being used, there's not a whole lot of margin to stay in regulation as is. Conversely, a parallel arrangement would destroy the runtime. Given this, a single LED seems to be the way to go.

The goal for this lamp, in terms of functionality at least, is the ability to be bright when needed, but also to crank down to lower levels for long runtime. And of course, to have it sort of disperse light like the original bulb.

Speaking of which, I came up with an idea last night. That is, to carefully cut the base off a small, frosted ican bulb (not sure how to do this yet), mount it to a thin, flat piece of plastic with a hole in it, and place this assembly directly over the LED. Not only could this potentially give me the closest imitation of a real bulb, but I could then use a Seoul with no worries of dust problems! If it works, it could be the ultimate dispersion optic. I'm totally psyched to try this out!

Now I just need to learn how to safely, and cleanly cut very thin glass. :thinking: Anyone know how this is accomplished?

Edit: Perhaps a thin wire saw?