Generally, the side-emitting Luxeons are used in reflector-based systems, since they work fairly easily as bulb replacements, sending out a 'disc' of light which is reflected by a relatively small part of the reflector. A side-emitting star might be usable in a headset conversion, but would require shaving the back off a reflector to the point where the LED could be properly positioned. I suspect there may be problems with then permanently mounting the star onto the reflector - gluing onto the smooth surface of the reflector could be problematical.
In commercial torches, it's presumably easy to design the reflector and LED-mounting system to make alignment a non-problem.
It's just a thought, but having seen a screw-in bulb which used a chunk of aluminium inside the bulb base to improve conductivity, I'd have thought that for a homebuild Oldham/Ceag conversion with a side-emitter, it might be easier to use a regular (non-star) side-emitter, and mount it on the end of a bit of aluminium bar that fits through the bulb mounting hole, and then work on aligning the bar/bulb assembly and aralditing it in place. Once the bar is permanently mounted, spreading the heat from it more widely may not be too hard, if it seemed uncomforably warm in use.
For a one-off personal unit, the only obvious advantage in fiddling to mount and align the LED in a bulb base and then mounting the bulb base in a reflector would seem to be the ease of remounting in another reflector if the first one is damaged. For a custom unit where you don't see the likelihood of changing reflectors, the bulb route may complicate things more than necessary.
I don't use the side-emitters. I use a Lambertian (wide-angle) Luxeon III star for a spot beam, and a plain Lambertian for a wide-angle beam. With my design, using the star actually makes mounting in the reflector easier rather than harder, and doesn't do any harm when it comes to dispersing heat into the aluminium sheet I use as a main heatsink. For my wide-angle beam, I don't have enough space to use a star, but direct gluing onto the aluminium seems to have been OK so far.
Even though I'm not exactly mega-commercial, I am selling some units (~15 so far, mainly to mates), so I'm wary of posting a direct link to my website. However, from my handle here, it shouldn't be too hard to guess what domain name I'm using, and there is a page in the root of the site (which isn't linked to from the rest of the site) called lamp_pics.htm which I've just uploaded with a couple of images to show the basic arrangement of LEDs in my design for anyone interested.
Possibly the major weakness of my approach is having everything mounted on the reflector - if someone has a leaking headset and repeatedly fails to dry it out after wet trips, and/or scratches the laquer on the reflector during heavy-handed cleaning, then corrosion of the silvering can impair the spot beam performance over time.
For me, it isn't a problem, since I'm careful with my reflector, and I can always dismantle a unit and rebuild it on a new reflector, but the effort involved is more than building a unit up in the first place, except for not having to build new controller electronics.
While there are obvious issues with multi-level lights in terms of simplicity of operation, they do open up the possibility of giving serious runtime off head-mounted batteries, yet providing quality illumination on the few times when you actually need it.
The bike light presumably uses a metal halide bulb. While something like 3x-4x the efficiency of present LEDs, they aren't currently scaleable down to cave-light power levels, and are already running at something near their theoretical maximum efficiency. LEDs still have some way to go before hitting their limits, since I understand that devices roughly twice the current commercial efficiency can already be made in test labs.
With the bike light, I suspect that there may be a reflector inside the unit as well as the lens. One particular reason for a bike light using lens-style beam formation is to enable an unusual beam pattern to be produced (spot in front, throwing other light down but not much light up, etc.
When you say 'magnify', do you mean you can see the bulb through the lens as being larger (when it isn't running), or that the lens concentrates the light?
:wink:
