Optics help, please.

I've had a project running through my head that would require a good hotspot with little or no sidespill. I'd like maybe a 2 inch hotspot at a 17-21 inch working distance. I haven't decided yet what I will use as a light source but either a high power 5mm like the MJLED or an underdriven Lux3. What kind of optics are available (if any) that can produce a beam with these characteristics? I have read that a high dome led with a fraen optic can produce a pretty tight beam but I have no personal experience with it. Is a fraen equally compatible with a 5mm or lux3? Also I would need it to be fairly small in diameter. Not much larger around than a solitaire if possible but up to the diameter of a 2AA minimag would be ok. I have seen fraen optics cut down for use in a firefly listed at the sandwich shoppe. Could that be a possibility?

The most important of my criteria are that it have an intense hotspot with little or no sidespill. No sidespill would be best. It will be led based. If anyone has any suggestions I'd really appreciate it. I'm still learning.

Have you thought about an Inova X1?

I have read about the tight beam an X1 produces but I am trying to build something myslef to keep it very small. I basically want to build my own headlamp for use in dentistry. I need the small size so it can attach to my loupes without adding too much extra weight. I want it to run off a remote battery pack that could either be attached to my belt or in a pocket. I need a focused beam that will illuminate the mouth but not the patient's eyes. I know I could just buy a production headlamp but I don't know of any that have such a focused beam and they are all more bulky than I want. I would also like to stay away from a headband if possible. An example of what I want to build can be seen at www.surgitel.com under products and then illumination.

What is described in your first post is very complicated to accomplish. If you have more space, you can use a 30mm optic which is so far, the farthest throwing optic that I know. (Besides Carclo's 2 degree optic, which is about 2 inches. Review is found here ) It depends on how much throw you really need. Can you tell us more about how much throw and brightness you need?

Fraen does offer a variety of optics with varying degrees of dispursion. I believe that they offer a model with a 10 degree beam dispursion. It might be what you're looking for.

Just today I talked with the sales rep for the company listed at the hyperlink above. He had the portable mini halogen light with him and I was able to look at it. It is made to fit their loupes and it's nice but it also costs $600. So I got to thinking about what I could make myself for much less money. It doesn't need to be exceptionally bright. If it's too bright it will wash out colors for shade matching or transilluminate teeth. I have a couple MJLEDs and I think they would be bright enough if they could be focused properly. They would also solve any heatsinking issues with a larger led since I want it small. The sample I looked at got hot very quickly when you turned it on and in the picture you can see that it has vents all along the barrel. The optics used looked like a marble cut in half. It bulged out the end of the barrel. The focus is somewhat adjustable it seems from when I took it apart. I don't know it that is a feature they intended. At the tightest focus it put a perfectly round spot on the floor. Although the spot on the floor was much larger than the spot that would appear at the working distance I'd be using it at. There was ambient light though so it is hard to say how much sidespill there was. I assume very little but I could be wrong. Possibly my main criteria for this light is based on an observational error. I'd like to figure something out that would work but if not....oh well. Thanks for any suggestions though.

If you placed a translucent plastic in place of the normal lens, if the proper material, would illuminate fairly evenly. It would then be a matter of obtaining a convex lens of proper focal length, to project an image of that illuminated disc at the desired size/distance. Maybe also possible to simply project an image of a lit LED. I was playing with this the other day with someone's computer that had one of those USB-powered LED flexi-lights. They also had a magnifying glass nearby. By placing the LED at the focal point, a very tight image of the lit die was projected on the ceiling. It was tighter than you'd want though, maybe 1 inch at several feet. But I guess that's dependent on the focal length. The illuminated disc would probably give a more even light across the target than simply projecting the die.

The easiest way to do this would be to image a 5mm LED using an off the shelf lens. Provided I have done the math correctly, you'll need a lens with a focal length of 45 mm. The closest match available from Edmund industrial optics is a 25mm x 40mm lens which costs around $30 USD. The part number is "LENS PCX 25 x 40 MgF2 TS". Just mount the lens 40 mm in front of the LED die and you're all set.

Thanks for the tips, everyone. I'll see what I can do.

Well the most amazing mindblowing optic that produces the tightest hot spot is the Carclo 2 degree narrow beam.... Like a light saber. But it has a 50mm diameter.