HI I was wondering if this lens would be usable for a thrower build
25 cm in diameter and 18.5 cm focal length
Can I somehow calculate max throw?
This lens won’t effectively collect all the light.
Given the domeless emitters radiate light in 120° beam, you’ll need either 30 cm lens with 8.5 cm focal length or a lens with a bigger curvature and thus shorter focal legth.
But that’s probably not a big loss.
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focal length is actually 18.5 cm i had an error in my post
The achievable throw can be upper-bounded by the diameter alone as the only relevant parameter. With current LED tech, a 40mm diameter optic can achieve around 1km of ANSI throw, so this optic can achieve up to 25/4=6.25km, in theory. Probably a decent bit less in practice as Fresnel lenses are less precise than other optics, which in turn may force you to use a larger and less intense emitter. around 5km would be a good estimate for what can be realistically achieved.
You might wanna take a look here: OLcontest, modified light: 20cm fresnel lens thrower
Fresnels don’t work exactly like standard collimating lenses…you probably want to “smush” out the light before passing it through the fresnel, or you’ll get some weird projected image.
Welcome to BLF! Keep us updated with your your build goes, good heatsinking will be important for maximum output!
I’d start with a temporary setup using PVC tube or wood, a big heatsink and a hard-driven 7070 size LED and go from there, you can change one parameter at a time and see how the beam looks. 3D print or machine the final housing to the specifications you need once you’re happy with the setup.
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Sure, if you can find an appropriate driver and have adequate heatsinking (PC heatsink with a fan?) then these will be BRIGHT.
whether they will throw far through the Fresnel, remains to be seen
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This is very good advice. A round-die 7070 LED throws well and at the same time has enough emitting area to offset the imprecisions in the large lens.
A lazy solution might be just to get a Convoy Z1 as the light engine and pre-collimator, and make the Fresnel lens some sort of attachment to the Z1. This way the problems of housing/power/driver/heatsink/focusing are solved at once. I’ve done something similar using a modified S2+ and a lens from a cheap zoomie as the light engine.
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