Let's talk aspherics in a proposed monster light

I have a project in mind. It’s not gonna be cheap, but I’m unsure about some things. If I were to take multiple aspherics in a single head side by side, I realize that up close they would all project independently of one another. But, at a distance, the beams should merge together. With throw and kcd in mind, would it be more beneficial of having multiple emitters with multiple aspherics like above, or just one huge aspheric lens? Say 3-4 50-70mm aspheric lens vs one 100-150mm lens. No zoom on any of these, just straight up zoomed out to focus the emitter. I want 1000kcd. Just trying to figure out how to get there.

I have nothing of value to add to this conversation, but if you make it, I want one!

Ha, you want one and I haven’t even built it yet! This thing will be a beast if I do build it. Heavy and ginormous. I’m thinking 6x 26650 3S3P or running them all parallel if I can figure out a way to do it.

Unfortunately, that’s not quite how it works.

I take it you are thinking of a big head with several aspherics side-by-side in an array. Below the lenses would be a single emitter in the center of the light.

Few problems with this design:

  • Except for the Lens in the center directly over the LED, all the other lenses are offset from the LED. The beams projected from them wouldn’t be centered. Only the center beam would go straight. All the other beams would go at an angle from the center. The individual beams out of each lens would never converge. This is also why people don’t make triples into zoomies… the offset emitters project their images at an angle instead of straight. Result is you get 3 separate die images off in the distance rather than 1 combined spot.
  • Focusing all the separate lenses would be quite difficult because the ones to the sides would be further from the LED. If you used identical lenses you’d have to mount them in a convex shaped lens holder so each lens would be at the correct distance from the emitter. Alternatively, you could use different focal length, lenses, but doing so still sounds quite difficult.
  • If you want the beams from the offset lenses to converge, you’d have to tilt all the outer lenses inward to adjust the beam angle. You couldn’t mount them all flat facing straight up. This might work, but sounds like a colossal amount of effort for probably little reward. If you have to tilt the lenses too much, you might end up losing output anyways.
  • For maximum possible throw stick to one emitter and one lens. It’s a lot easier. Yes, this might result in you needing a gigantic lens, but it’s the most effective way to do it.
  • If you want a giant lens that is thin, instead of trying to make an array of small aspherics, just get a big fresnel lens. A fresnel gives all the benefits of an aspheric but is completely flat. Fresnels aren’t perfect though. Typically you’ll lose 20-30% of the throw compared to a same size aspheric due to scatter at each ridge. Still, I’d recommend a fresnel as your best option. You can buy fresnel lenses that are as big as 1 meter across… big enough to melt concrete just from focused sunlight. I imagine you could get a lot of throw with one in your flashlight.
  • There are some other weird ideas to get lots of throw. I recall one post a couple years ago. Someone built a light that shined backwards into one of those cheap maginifying mirrors used to apply makeup. The reflection off the mirror came out focused and was enough to project around 1 million lux.

My take on it was that the OP wanted to use several lenses with several leds and focus all of them into one converging spot, at a distance.

While it would be hard, one could actually make a light with several separate "heads" combined. The center head facing straight out and the other heads around it, aimed to bring the beams together. Of course, a problem with that is you will only have one exact spot where the beams all cross and after than they start separating again. It might be very hard to get them converged at a distance, like a mile or so and it would also be hard to measure the output.

Actually having several lenses each with their own LED works. Basically just like duct-taping a bunch of SK68s all together. The beams will converge off in the distance and you’ll get one bright hot spot, like in the LED Lenser X21. Would be an interesting project.

Sounds interesting. Just design a 3d printed screw adjustable jig to hold and aim whatever flashlight you want to use. Then custom wire all the tail caps together to a master switch. You could work on each light separately to make focusing easier.

You wouldn’t necessarily have to have all the beams focused into one spot. If they were all aimed directly forward, say in a 3x3 array, as the beams spread over distance the outer beans would enter into the center’s space and vice versa leaving you with a more intense center spot and a less intense ring around the outside. I think doing so wouldn’t be the most efficient way to get more throw since some of light in the out ring is “wasted” by not reaching your target. However the slightly wider and higher total lumen beam would be more impressive to look at and it may be much cheaper to get more surface area worth of lenses by using multiple smaller lenses rather than one large one. I can think of one extreme example of this in a custom build I saw a while back on the “other site” called the Databank 70, which used tons of small lenses in a massive parallel array. I don’t recall seeing any long range throw tests though and I don’t know if they were all focused perfectly.

Yes, there would be an emitter for each lens. I would have to use bigger die emitters for this. Basically figure with imaginary numbers that a XM-L2 has an 12” hot spot at 10 yards. At 100 yards it would be say 10 feet. If I may a head with multiple lens, would they stay independent at 100 yards and further or would the die image start to overlap? If they overlap the it would amount to spill on the outer edges of the outside lens with a super bright middle lens from the overlap. If I didn’t do lenses it would be multiple deep reflectors. I’m talking about multiple 70mm aspherical lenses or 60-70mm reflectors. Basically the light will have a head probably 6-8” across. I’m going to try to strap multiple aspherical lights together to see what the beam will look like.

Basically, if I ran a bunch of LEDs under aspheric lenses would it look like the picture below with the overlapping

As long as you have a separate lens for each emitter and all are aimed straight forward you won’t have an issue. Even with an aspheric the beams widen. At 100 feet, the beam might be 5 feet wide. Meanwhile the separation between the hot spots is governed by their location in the light…. probably less than an inch between each spot. Get further than a few feet from a white wall and you should just see one single hot spot.

I think you may even be able to trim aspheric lenses to make them square to match the die shape and projected beam. This way you can get them closer together, this of course would be tricky with glass lenses but could use acrylic.

Hi,

i have a similar project running for some month. I had some driver issues with too long cables. I will try to solve these with some power caps between the 4S LiPo and the drivers (3x LCK 5A Driver). My setup will run on three XP-G2 S2 1D dedomed, 75mm aspherics from LCK and a massive heatsink (~900g) in a Thor Colossus X Host.

Some impressions

As mentioned above i think placing the lenses to get a common spot is the most difficult part.

Greetings

Kenjii

For generating throw (spot brightness), using multiple lenses+emitters will not generate as much throw as one single lens with one emitter covering the same area of the multiple-lens-array. The spot area will increase, but not the brightness. Of course you will not find a lens as big as Kenji's head, so in that case going multiple lenses is the way to go.

But perhaps you use a fresnel lens, like this 31cm one (but I'm sure it can be had cheaper than here, and round):

I recall there being a thread from several years ago where a user posted a pic of a triple(?) aspheric thrower he had built and had commented on the alignment issue. A quick search didn't turn that up though. Anybody else recall?

Kenjii. That looks like an amazing light. Have you thought of doing a build thread for it?

For a given size, you can get more throw with multiple emitters, if the same optics is scaled and replicated and they are Siamesed to fill up the whole head area (as with SRK and the like). The reason is that you can use smaller LEDs with greater luminance but still get the same beam size. Except for some loss, from a distance, the front of the light all looks as bright as the surface of the LED. Smaller LEDs cool better, so they can be brighter in the sense of more light per area. You could use a small LED with huge optics to get the same throw, but the spot size would be like a laser pointer.

I’m working up some ideas for the homemade flashlight contest. Should be interesting

My only scratch built idea is a feather weight thrower with my stage lighting Fresnel lens and model airplane materials. But the light I have it in now, with only the head home built, is just as good with much less work.