I plan on 3D printing a box shape host for a fresnel lens thrower. Will it improve throw if I put a reflector on the LED, so the light going into the fresnel lens is more concentrated to begin with?
Interesting question…I don’t have a solid answer. Generally a reflector is going to rob +/- 15% of the light, so consider at least that much of the equation.
You want to come as close as possible to a point source, not light coming from the surface of a reflector besides what comes directly from the LED.
What you could try is use a pre-collimator lens to get more of the emittted light directed to the fresnel lens, but it will not increase throw but give you a larger hotspot (wider beam).
Another option is the “wavien collar” but they’re hard to come by and expensive.
Yes. A reflector does nothing to increase intensity; all it does it collect stray light, and the end result would be a very ugly, messy beam.
A pre-collimator lens does better: it collects the stray light into a more coherent beam in the shape of the emitter, rather than a donut shaped beam. Compared to a bare emitter into the Fresnel lens, a pre-collimator gives you a fatter, more useful beam.
Ideally a wavien collar is best--it is the only option out of 3 that increases intensity.
Anyone know where I can find a pre collimator for sale? I've never heard of one before. I tried looking on AliExpress...
Pre-collimator describes the function of the object, not the name of the object. Depends on what LED you are using, but usually the convex lens from a cheap zoomie would do. Just any small convex lens with a short focal length.
I've built a Fresnel thrower myself using a lens salvaged from a $1 zoomie. Have a Osram WF1 putting out only 400 OTF lumens due to inefficiencies of the optical setup (probably less than 50% transmission), but it throws over 2 miles.
Here's the build log with pictures, in case you find it useful.