Don't know about where to find fresnel lenses but this is one great modding job! Well done (sofar, more to come apparently :-) ).
I agree about large elements and short focal length, but I don’t know much about where to get them.
I don’t know if small segments have advantages or if they are just easier to make with modern methods. I think the best would be to wrap around the source, like a lighthouse lens. The center focal length could then be as long as there was room for, and it would still catch all the light, though it would not all focus to the central spot. That would be harder to make than a flat sheet but maybe no harder than a conventional lens.
That’s an interesting idea. And if it wrapped all the way around the lens and further down the bezel it might work somewhat like an LED Lenser lens. So you wouldn’t lose half the lumens swapping to spot mode. Would have to be custom made though and probably very expensive.
I found a supplier who can manufacture custom glass fresnel lenses, that in the pictures have much larger lines than the plastic ones. The glass would probably be ideal, but unfortunately I think that would be far too expensive.
I’ve ordered a different fresnel lens from another supplier. If all goes well, it should arrive next Wednesday. However, it’s made of the same stuff and also has lots of very finely spaced lines. I suspect it will be no better than the current fresnel. I like the smaller size I can get with the fresnel lens, but it’s probably not worth losing 1/3 of the throw just to shave 3mm off the length.
I’ve also got a lux meter coming. Should arrive today or Monday. The plan is to use the meter to measure the throw with each of the 3 lenses. Until then, I’m holding off on making any more permanent modifications to the light.
My luxmeter arrived and I took some measurements.
With the stock lens I measured 22k lux.
With the fresnel factory fresnel lens I measured 18k lux.
This was using a protected 18650 cell. Interestingly, swapping in a Samsung 25r INR cell didn’t seem to increase output at all, though the light got noticeably hotter faster.
At this point I’m leaning towards going with the fresnel. It gives less throw, but will allow a more compact light. With the stock lens I have to use the original umodified lens ring and the light is 97mm long. If I go with the fresnel, I should be able to get the light to around 91 or 92mm long.
I also kinda like that the fresnel lens has a much softer edge at the sides of the beam.
The current emitter is a dedomed XML2 T6 3C from Illumination Supply. When I dedomed it, I slid the dome off in one move with a toothpick after 8 hours of soaking in Coleman fuel. This worked fairly well. A very thin layer of the dome remained on top of the LED, but I decided to leave it as the tint is a very pleasant warm white with no hint of green.
I currently have an alternate emitter soaking. It’s a 6500k cool white XML2 U2 from Mouser. I think I’ll let this one soak for 24 hours in the hope the entire dome will fall off on its own.
I installed an alternate emitter today. Here’s the measurements at turn-on with a Zebralight 3100 mAh protected 18650:
XML2 T6 3C from Illumination Supply dedomed, but with a very thin layer of dome left on top of the emitter (I think this thin layer reduces the tint shift, but also reduces the throw):
- with Fresnel Factory 21 mm Fresnel lens: 18k lux
- with stock aspheric lens: 22k lux
XML2 U2 cool white 6500k from Mouser dedomed (XMLBWT-00-0000-0000U20E1). Phosphor completely bare. I scraped the thin layer off the top of the emitter.
- with Fresnel Factory 21 mm Fresnel lens: 28k lux
- with stock aspheric lens: 34k lux
The T6 3C has a very pleasant orangish warm-white tint with no hint of green. The 6500k cool white from Mouser is a greenish white… definitely a worse tint, but much more throw.
I filed down the inside of a spare bezel tonight and fitted in a wider aspheric lens than the stock one. The stock one had an effective diameter of 18mm. The new one I swapped in was from an MXDL SA-811 and has an effective diameter of 20mm. It’s also a shorter focal length than stock.
At turn-on (with distance to meter double-checked):
18mm Fresnel lens: 27k lux
20mm Aspheric 48k lux
I might end up sticking with this lens since it’s far better the fresnel. 77% more throw!
I wonder how well the new fresnels I have coming on Wednesday will compare. I’ll file one to 20mm instead of 18mm to get more surface area.
Here are some pics of the light with the 20mm aspheric installed
In its current form with this aspheric the entire light is 97mm long. However, I shrunk the pill a little bit which opened up the battery compartment more. I can recover that space and shrink the light approximately 2mm by filing off the top of the body threads where the pill screws in.
The thicker aspheric lens is very close in height to the top of the lens ring. It does not protrude from the bezel though, so if the light is placed on a flat surface, the top of the lens will not touch.
Using a thicker aspheric lens limits the beam angle in flood mode, because the bezel must be left deep enough to protect the lens. This reduces the beam angle to 82 degrees…. definitely narrower than the 89.5 degrees I got with the stock 18mm aspheric and 92 degrees I got with my first fresnel.
I suspect that with a fresnel lens and a bezel modified to put the fresnel near the edge of the lens I could get the beam angle to approach 95 degrees or more in flood mode.
This has become an unusually useful light.
Thanks.
It’s my current EDC and by far my brightest and throwiest zoomie. I’m quite pleased with it. 
> more tiny screws
Tell all your friends to test their old backup hard drives. (Turns out that magnetization on hard drives slowly fades out; who knew? Remind them to be prepared to copy anything the first time they spin an old drive up, in case that’s the last time it’s going to spin up …)
When they give you their failures, take’em apart. Screws, magnets, thin metal shims sometimes, useful wires; swivels and rings, oh my. Drive cases are nice heatsinks for fixed lighting. And toss the leftovers into computer/electronics recycling.
I have an old computer in my closet that I think I’ll try to salvage for screws.
This light uses 6 tiny screws: 4 for the switch cover and 2 for the star. All were salvaged from other mods or unused clip mounts. I quite like how the screws turned out, but definitely could use more.
My new fresnel lens arrived today.
My previous fresnel was one from Fresnel Factory. Cost around $6.
The new fresnel is from Edmund Optics and it cost $25. However, comparing the two I see some obvious differences:
- Things look much sharper through the Edmund Optics lens.
- The image of the die seems brighter and is sharp enough to see details on the surface of the die. In contrast, the image from the Fresnel Factory lens is so fuzzy you can barely see the cutouts for the die wires.
- The circular lines of the new lens seem smaller and closer together than with the cheaper lens.
My initial impression is that this new more expensive lens is much superior to the previous fresnel lens. Tonight I’ll file it down and test it with my meter. If its within 20% of the lux of the aspheric I’ll probably switch to this new fresnel. I can still swap back to the aspheric later if I wish, but might need to make a new bezel. Fortunately, I received a fresh unmodded Aleto N8 today for use as spare parts.
Another thing I need to consider is how durable the new fresnel looks. If it’s not tough enough for pocket carry, I may need to consider putting an AR coated glass lens on top. That would cost some light output and make the light a couple mm longer.
I’ve never worked with Norland before, but looks like tonight I might give it a shot. I’ve got Norland NOA61 and a 365 nm UV flashlight to cure it on hand, purchased just for this use.
One issue with the new fresnel is that unlike the old ones, the Edmund optics one is a square piece of clear plastic with the round lens moulded in the center. The Fresnel Factory ones came round so there wasn’t much to file off. Because of this square area that’s a HUGE area to try to file. I wonder if it would be better to cut it. And if so, should I use a saw or a scissors. I don’t really want to risk destroying a $25 lens just because I was impatient…
Did you drill the pill through the star and use screws that tapped their own threads?
Would it have worked better to use a brass strip instead of a tin strip?
Part of this depends on the design, but there is an unavoidable scattering at any edge due to the wave nature of light, diffraction.
Actually I chose the Illumination Supply Star instead of a Noctigon because the Illumination Supply star already had slots for screws. I positioned the star, marked where I needed the screws, then drilled into the copper heatsink below the star with a pin-vise drill. Then I just screwed in. The screws self-tapped. I used the same technique for the 4 screws holding in the switch cover.
Brass might work too. Main reason I chose tin is it doesn’t conduct heat well so it solders easily. It’s actually sold in sheets at the hobby shop as “Easy Solder tin sheet”. Solder bonds almost instantly to it… even easier than soldering to the small wire.
The main current to the emitter doesn’t flow through the tin strip. So a low-power connection with very thin wire and tin works fine.
Here’s a pic of the light in it’s current form with 20mm aspheric lens installed at 97mm standing next to an unmodified Aleto N8 at 108mm.
Last night I filed and cut down the Edmund Optics Aspheric lens. Took much more effort than the Fresnel Factory lens, but this new lens is definitely higher quality. The lines are so fine that you can’t see them unless you look very closely. And they’re lacking the distinct white edges that the Fresnel Factory lens had.
The new fresnel seems to only reduce the throw by 10-15% compared to the 20mm aspheric. It’s sufficiently close that I’m going to modify the light to optimize for this new lens.
A few observations:
1. The Edmund Optics fresnel lens has a noticeably shorter focal length than any of the previous lenses and as such, produces a noticeably larger image of the die. I modified a lens ring to be thinner and mounted the new fresnel in it. This ring raised the position of the lens by approximately 2mm, with the intent that I’d then file down the top of the bezel until the lens is at the right height. This higher lens combined with the shorter focal length means I’d need to file down the bezel by 5mm. Unfortunately, I can’t file it down this far without filing off all the threads on the inside of the bezel leaving nothing for the lens ring to screw onto.
I have a couple options to address this:
Option 1: file it off anyways then use some other means to hold the lens ring on. A very fat o-ring might provide a tight enough fit even without threads. I’d like to avoid glue as I want to have access to the emitter for emitter swaps or other future mods or fixes.
Option 2: Add a C-ring behind the pill made from a strip of bent aluminum. This C-ring would stop the bezel from sliding once it has hit the proper focus.
Regardless of which option I choose, going with the fresnel means the light should be reduced in length to around 92mm…. 5mm shorter than with the 20mm aspheric.
I’m leaning towards option 2 because I know it works and I already have the C-ring. It’s also quite reversible if I decide to change my mind and go for option 1. Regardless which option I take I’ll file off the top 2mm of the bezel. It will still have threads to screw into at 2mm, and 2mm is what I need to bring the back of the lens into contact with the top of the pill for maximum possible floodbeam width.
If I go with option 1, then the back of knurled bezel will sit quite far forward of the heatsink fins. I could use this additional space to move the switch about a half cm forward, which might make it more comfortable to use.
2. The ridges on the lens are so small I’m a little concerned they might scratch too easily, or pickup dirt and be hard to clean. There’s room to stick a 20mm glass lens on top of the fresnel. This would provide protection and be easy to clean, but when I tried out my stock of 20mm AR coated lenses each seemed to reduce the throw by about 10%. This might be too much loss, especially when added to the loss from going fresnel over aspheric.
3. The new fresnel lens is press-fit into the bezel with some Norland NOA61. Currently it’s outside in the sun hopefully curing. My UV light has seven 5mm 365nm LEDs and wasn’t curing it fast. Perhaps I should’ve purchased or made a more powerful UV lamp. I’ve never used Norland before so am not quite sure how long it will take to cure. If I decide to stick a glass lens on the front of the aspheric, I’d have to attach it at the edges with Norland. Without the Norland its too loose. Unless I can somehow fit in a rubber gasket instead of the Norland it won’t be reversible.
4. If I find I really don’t like the fresnel, I can always go back to the 20mm aspheric, as long as I don’t move the switch. I’d need to file down a new bezel, but I have 2 spares in hand.
I installed the new fresnel and shortened the light.
- The light is now 92mm long… the exact same length as a Sipik 68. It also feels better in the hand and in the pocket than a Sipik 68 due to its cleaner shape, but it’s also heavier because of the weight of the much larger battery.
- Beam angle in flood mode in the modded Aleto N8 is now 93 degrees. For reference the unmodded Aleto N8 has a 57 degree beam angle in flood.
- I currently don’t have a glass lens on the front. Hoping the fresnel doesn’t get scratched and if it gets dirty it can get cleaned off. I have AR coated glass lenses on hand that fit, but will need to be glued in with Norland. The glass lens reduces lux by about 10%, but should make the lens more durable and easier to clean.
- The sideswitch is stiff enough there’s pretty much no chance it will accidentally turn on in the pocket. This was by design. I tried making the switch more sensitive, but decided I didn’t want the risk of accidents.
- The focal length on the new fresnel is very short, while the stock Aleto N8 came with an aspheric lens with a very long focal length. The result is that the image of the die in spot mode between the modded and unmodded light is about the same size…. even though the modded light is using a dedomed emitter while the stock still has the dome. Of course, the modded light’s die image is much more intense.
Here are some pictures:
Your work is inspiring. What a great achievement. A 18650 zoomie the size of a 14500 light. You ROCK!