I mean, I was planning to buy a 11” electroformed reflector that would collect nearly 100% of the light, but even though it would get almost all lumens, the distance the reflector surface is from the LED is between 3” and 6”.
At 45 degrees to the LED, where most light is emitted, is 3.5”.
So even though it would have a lot of lumens the spot size would be larger than even a 150mm lens that collects 60 degrees of light, since the surface of the lens would be at about 4-6” distance (compared to the reflector being at 3-6”)
It would still be a cool light to build since nobody’s really done it before, and lots of lumens is nice, but tbh this will not come close to breaking any throw records even if I did use a 11” reflector rather than 5” like you were planning. (and yes, the reflector I calculated this with had a longer focal length (smaller spot) and collected more lumens compared to a 5” reflector that did 120-140 degrees)
Generally the actual luminous intensity (throw) only depends on the diameter of the reflector and the luminance of the LED. A 11” reflector will easily break all “records”. 10Mcd (based on a luminance of 200cd/mm^2) should be doable without any problems.
That only applies if you compare one reflector to another.
If you compare a reflector to a lens, it’s a whole different story, because the intensity of light projected at a distance is relative to both the distance from the LED to the lens as well as the angle the LED face is at from a point on the reflector/lens.
Assuming the wavien collar recycles almost all light, and the reflector collects almost all light, the 150mm lens on average will have it’s surface farther from the LED than the reflector would.
This means the lens will be making a smaller spot, while the reflector makes a bigger spot, both with a similar amount of lumens.
Therefore, the lens would have higher intensity.
The focal length of a lens has no effect on center beam candela (throw). This has been proven (see Ras posts on CPF).
You can’t compare an LED with Wavien collar and a lens to an LED with a reflector. That’s comparing apples to oranges.
The Wavien collar increases the luminance of the LED.
It collects 75percen of the LEDs light and doubles the luminance (so you have 50 percent of initial light of the LED coming out of the collar).
A lens of the same diameter as a reflector only throws farther because it doesn’t have the hole in the center. So it has a bit more surface area, but it’s a small difference.
The focal length of the lens determines the size of the projected spot.
The longer it is, the smaller the spot is, and assuming constant F ratio, higher intensity.
Maybe you want to link that post you’re talking about?
The entire point of me comparing them is to point out that a smaller diameter lens+wavien collar will still get higher lux than a large recoil reflector.
Where did you get the 50% from? I was looking for tests that showed how many lumens you get when using a collar as compared to stock lumens.
If you can link a source that would be great.
This is based on the false assumption that all that matters is the front area of the optic.
I think you can see clearly that it is false by simply comparing an aspheric flashlight to a reflector flashlight with the same front area.
The throw will depend on the intensity, which is determined by a lot of factors such as LED spatial distribution, distance from the LED to the optic’s surface, angle between the LED and the optical surface (for a single ray) and also the reflection/refraction of the optic.
Jeroen, Just an idea to solve some of your heat related issues with the recoil setup. What if you use blue laser instead? So all you have to do is place tiny dot of whatever white emitting phosphor in the recoil - less heat to manage. Then shoot the phosphor dot with blue phosphor from some points (if you want more power with better efficiency) - easier heat management at laser diode(s). Cooling the phosphor alone is easier than cooling the phosphor PLUS the die. You can use any scrap LED to test as the phosphor point. Ideally the phosphor is deposited on reflective and high thermal conductive material such as polished AlN (found on LED chips) or silver.
Well, the “laser” they’re using is still a diode, I think (at least most “laser” products are). But ,the laser diode has a narrower beam than lighting class diodes, so less is wasted.
Yeah, it’s a nice idea, and it has been discusses several pages back.
We would need a ‘blue’ (often purple) laser
I don’t think it will have better efficiency than an LED though.
And frankly i don’t see any serious cooling issues when you put some flat heat pipes across the reflector with the LED soldered onto it.
It would be an XHP35 or an XP-L2 that i want to use, so maximum 20 Watts.
It would also be a lot simpler, which is a plus in my book.
…and a lot cheaper…
I imagine the phosphor would have a mirror behind it so that the light is all reflected towards the reflector.
But shouldn’t the phosphor be cooled too?
I think so, otherwise it will be burnt by the intense hot spot created by the laser. Anything opaque will absorbs most visible photon energy. But not as severe as if you place the LED in the recoil - this is my guessing so don’t take it too seriously. I often do some laser cutting jobs in my friend’s workshop, and cutting a clear PMMA required as much laser power as to cut thicker multiplex wood plate.
As for the heatpipe layout, in my opinion, since heatpipe is orientation sensitive, it’s better to use full bridge on top the parabolic mirror. This way you can get average heat shedding capabilities from each heatpipe bars. A cross mark design with smaller heatpipe is what I’m thinking.
Yeah, a bridge of heatpipes across the reflector is the eventual plan.
Perhaps even a cross or “Mercedes star”.
I’m not sure if the flat ones are also orientation sensitive though, i doubt it actually.
Any heatpipes with wick lining will be less sensitive to upside down orientations (hence they designed) but still perform somewhat better in normal orientation. The general rule is heat down, cool up. But the wicking technology should already improved by now.
I remember those older laptop manuals stated not to use the laptop other than in horizontal position, perhaps because of this heatpipe issue.
Ah… I see. you are keeping the F ratio constant. I always compare lenses of the same diameter with each other (precisely because the diameter determines the throw and size of the flashlight).
No, as far as I know, that has never been shown in practise. It also doesn not correspond to what the physics/optic experts (Ra, WalterK, sma, Dr. Jones etc.) say. Only get_lit writes some weird stuff which they, as far as I know, have not agreed to.
Some posts from Ra (professional optics guy): click, click (there used to be pics there, which showed the different lenses and the lux meter display), click
A detailed (German) thread from sma: click
A detailed from Dr-Jones: click
Depending on the exact diameters and using the same LED at the same current in both cases: yes. This is only the case though, when the diameters are rather similar since the Collar only doubles the luminance and the area of a circle increases with the square of its radius.
The assumption is not false. The calculation seems simple, but it makes sense when you think about it and we/I have tried it many times. It always seemingly works, when you have correct starting parameters and the optic/reflector is completely lit.
Imagine you are standing where the hotspot is (far enough away so that the beam is fully formed). You are looking straight at the flashlight. What do you see?
You see (with a reflector) the LED in the middle and the reflector, a big yellow circle with a hole in the middle around the LED.
Now consider this: when you have multiple identical flashlights and you hold them parallel so that the beams merge in the distance, you can multiply the candela value by the number of lights. It just adds up.
Now back to you standing there, looking at the light. The reflector is basically multiplying the LED. It’s basically increasing it’s area. So in effect it is multiplying the luminance of the LED, which is Candela per unit of area, usually mm^2. So when you multiply it with the apparent area of the reflecting part of the reflector as seen from your position (you are seeing what a lux meter would “see”), you are left with Candela.
This also shows why depth (focal length) doesn’t really matter for throw. Only the area of the optic (which is determined by its diameter) makes a real difference (and of course the luminance).
Here is a post from sma in the German forum where he thoroughly studied the Wavien collars (which is really great since no one else seems to have publicly done something similar). He went to a lot of effort to get a perfect focus for his measurements. Further down he calculated how much of an LEDs lumens they collect. He says it’s 75% (simply based on the angle). From this I deduced that the collar, after “amplifying” the remaining 25% by 2x (maximum: 2,2x) emits 50% of the original light of the LED.
BTW: he he even compared all three collar sizes to find the differences. As expected the large one is the best (he guesses that it has a bigger advantage when using larger emitters).
Blue Lasers are more efficient than blue (and white) LEDs at very high current densities. LEDs suffer from Droop, which is basically an “abnormal” reduction of efficiency at high current densities. Laser diodes don’t suffer from droop. They get linearly brighter with rising current.
The separation of laser and phosphor also means that the phosphor is cooler (because it is not heated by underlying blue LED) and that is can be cooled seperately (by putting it into glass substrate for example).
BTW: I find it great that you guys are planning to use heatpipes. They are cheap and very effective. In my eyes there are not enough lights using them.
I think a clever design would put the batteries in the middle of a light and the heatsink at the back connected with heatpipes. This way it would be easy to balance a light and one would be holding the light where the batteries are, which is usually not as as hot as the heatsink.