Who said it should be aspheric?
If you wanted to use multiple LEP emitters and reflectors to increase lumens, you would be better of with a typical led+reflector setup, really.
LEP has double luminance of LED (as long as the LED doesn’t have a collar - and that’s the case with reflector lights).
This means double beam intensity.
…That’s assuming you can run them all to the max. Which should be doable as long as the host is properly sized.
LEP produce very few lumens. You really need to make use of every single one of those lumens and focus it without any spill to take advantage of the main feature of LEP: A very small die size.
A reflector won’t be able to do this as well as a properly focused lens.
If you want a similar throw, with more lumens (larger beam size at target distance), and are willing to increase bezel size to get there, an XHP-35 HI light with a reflector can easily get you there.
If you want double the throw, and are OK with the small beam size, you want a single LEP in a larger lens. http://www.acebeam.com/wl20-throw-2000m
It’s not hard to do what the W10 does with common leds if you don’t mind increasing bezel size. The entire point of the W10 is that the bezel is, for it’s throw, incredibly small.
Using 4 LEP is not the answer to increase throw. Using multiple emitters is never the answer for longest throw/bezel mm, because it increases die size. No dedicated thrower uses multiple emitters for this very reason.
1. Reflector vs lens:
Properly focused reflector will capture more light than a properly focused lens. (Well, it’s actually independent from whether they are focused properly or not).
According to Enderman’s calculators deep reflector can capture about 60% of light. The rest is spill.
With a lens even 40% is a huge stretch. With a F# if 1 you’re capturing under 17%. The rest is lost.
2. XHP35 HI vs LEP
XHP35 HI gets 170 cd/mm² at the max. LEP does 400. You need to increase head diameter by 50% for the LED to compete.
3. Single vs. multi-emitter
In theory, using multiple emitters is often the best answer for the longest throw / size. But I define size as overall light volume, which boils down to head volume.
Why? As you noted, if you compare a single-emitter light to a multi-emitter and keep emitters constant, light emitting surface gets bigger which may cause thermal and electrical hardness.
Also, multi-emitter lights also have lower effective reflector area for the given head diameter.
The latter can be somehow countered by using configurations that maximize head usage. Like 7-up. Then you get a fair use of frontal area. Then you scale the diameter up to have the same effective area as with a single-emitter. You end up with smaller head volume yet the same throw.
The former can be countered in theory by using smaller emitters. LEPs are small. The smallest LED that we know to be good is a little over 1 mm². Quite big already, so in practice it’s not so great as in theory….because it adds up to 100 W near-peak with a 7-up. Needs a hefty host.
Also, focusing multi-emitter light might be harder. How precisely can we solder emitter to MCPCB? I have a hunch that the error margin may be comparable to light emission surface diameter….
Given that I currently have a standard BLF GT, and a second one with exactly the same driver and led, but using a 120mm aspheric lens, and getting more throw out of it (1.3 vs 1.5mcd), I think there is more to it than “reflectors are better than lenses”. No wavien collar installed (yet).
Enderman himself has used lenses for a lot of his lights, and has had to stop because getting bigger lenses was getting impossible.
Adding more emitters to increase throw forces you to have a bigger head regardless. If you try to cram more emitters in the same space, you have to get by with smaller reflectors/lenses for each emitter, which will decrease the focus/increase the spill/increase the angle of the beam.
“In theory, using multiple emitters is often the best answer for the longest throw / size.” No it isn’t. It literally isn’t.
Just look at the list of the best throwers Most Powerful Flashlights in the World (by throw distance)
Or even direct examples. The TN42 uses a single led+reflector on a 100mm bezel, 2000 lumens, and claims 1550 meters of throw. The TN40S uses 4 leds, the same 100mm bezel, 4450 lumens, and claims 1150 meters of throw. The XP-L HI emitters used on the TN40S even have higher cd/mm die than the XHP35 HI used on the TN42.
If you increase the throw by adding multiple emitters and running them all hard and increasing reflector size, you are not getting more throw because multiple emitters are better for throw. You are getting more throw because you have a using more power on a bigger light.
There are many factors that affect throw and optics quality is among them. A shallow reflector (like GT) has a smaller working area than a lens. A deep one has larger. Quality also matters, a lot.
With collar. Which is really a game changer.
Yes, you lose some area by having more emitter openings as well as some around the edges. In case of a siamesed 7-up it’s like what - 10% loss? Let’s make it 20% to have a good margin. You make up for it with 10% larger diameter. But your reflector is 6.3 times shorter. This won’t make your head 6 times shorter but 20%? Way more than that.
XHP35 HI at 2200 lumens does ~130 cd/mm². XP-L HI at 1200 lm does ~100 cd/mm².
I don’t really advocate quads as a quad is less efficient (when it comes to head use) than a 7-up.
And as I said, if you define size as diameter - single emitter wins. If you define it as volume - these 2 lights aren’t really comparable.
As long as you reduce die size proportionally to the number of emitters - no, at the given luminance you use the same power. But as I said it works better in theory than it does in practice.
Everything else you said is right, but if you simply add more emitters without changing the area of the optic all you’re doing is creating more lumens, not more throw.
The intensity would not change, the light output increases and you would get a larger spot (or multiple spots in this case, since the LES is so small)
Actually, since I said about making emitters smaller, I don’t gain lumens either. I just reduce head volume at the cost of having flowery beam and higher price. In some cases reducing cooling and worsening ergonomics as well, though in others either may be improved.
If we move out of the theoretical case of using 7-times smaller emitter then yes, multi-emitter thrower uses more power and gives more lumens without improving lux.
The whole discussion started with complaints that W10 does only 200 lm. I chimed in because I share that concern, I like certain cd/lm range and W10 is way out of it. A 7-up reflector would put at the very least 1500 in the beam and likely 2000+. It couldn’t be W10 sized though due to heat….
Oh you mean increasing the number of emitter but with their own optic each, then yeah that would increase intensity.
The reason the intensity increases is because of the more area, not more emitters.
If they used a more powerful but less concentrated laser they could achieve similar intensity but a larger spot and more lumens.
If they used a crystal they could get more lumens without increasing spot size, so both more lumens and more intensity.
But then it wouldn’t be a $200 flashlight it would be $1000.
It seems I fail badly at speaking clearly today. This is not the only discussion where it shows…
I was debating 2 cases:
- theoretical advantage of multi-emitter throwers (the sole advantage being smaller head volume for the given throw)
- getting more lumens out of LEP lights to make the beam wider
On the first topic I meant only diameter increase that would keep reflector area constant.
On the second one I meant to keep head size constant by having more emitters and smaller per-emitter optics. The purpose would be to have the advantage of superb throw that LEP offers while widening the beam (so I can see the target without binoculars). Though I mentioned a larger head because of thermals - this would again narrow the beam down. So keeping the as-much-throw-as-size-allows that LEP offers together with beam that’s wide enough for me doesn’t seem possible with W10 tech. I suppose that to widen the beam one would have to either reduce thermal issues by underdriving the LEP or by purposefully defocusing the optics. At that point indeed LEDs look more attractive.
But you mentioned another topic that I haven’t seen before - “crystal”. Quick search - you mean single-crystal phosphors, right? I wonder what’s the source of your price quote, I see some company claiming them to be as cost-effective as mixed phosphors.
Do you know of anyone who tried transplanting such phosphor on a LED emitter? Seems like something that saabluster would do.
See here (in German). There’s a lot of additional information regarding laser phosphor systems in general in the first post of that thread.
I don’t think I understand what you’re saying then, because no matter how many emitters you use the throw does not change if you keep a constant head diameter.
And yes I was talking about phosphor crystals.
The crystals are several hundred dollars, then a more powerful laser will also be several hundred dollars.
AFAIK there are only two companies that provide commercial phosphor crystals.
Thank you The_Driver!
Volume, not diameter. Multi-emitter reflectors are much shallower than single emitter ones of the same diameter.
Could you please name that companies?
Multi-emitter reflectors also have a lot of wasted area, which is why they are usually bad at throw.
One of the companies is cryphosphor, the other I cant remember but was way more expensive, you can find it by reading the research papers on single crystal phosphors, the universities state where they got their samples from.
Siamesed 7-ups don’t have that much wasted area. You can make up for the area loss by increasing diameter.
After you do so you end up with exactly the same throw, a bit larger diameter, but smaller overall volume.
Cryphosphor is the company I found, they claim that cost is comparable to phosphor powders. Hmmmm….
Please give us an example of a very throwy multi emitter light.
Tough call. Manufacturers don’t really attempt making such lights. Which doesn’t make the concept wrong.
I believe Emisar D4Vn with Oslon Black Flat is the throwiest light for the size despite using poor optics.
I don’t think that light exists . Please give me a light with a throw figure so I can compare it to other real lights.
It seems to have been removed.
It did exist:
I don’t remember throw though and I can’t find it, even web archive doesn’t help (because it doesn’t have D4vn page in the cache at all).
Dedomed XP-G2 does 40 kcd
It is still challenging to find something to beat 40K at that size though.