Dedoming XR-E R2 in aspheric Solarforce L2 for more throw?

[2xTrinity]

I am referring to hotspot lux only



Remember Ra & Dr. June's threads & experimental proof? In aspehrical set-up, Adding secondary lens infront of led does not change throw. Removing the dome, which is a secondary lens, does not change throw if the led remains unchanged. But in this case, after de-dome, the led lose about 30% brightness , thus lose throw.

What exactly do you mean by "brightness" -- total lumens out of the emitter (luminous flux) or peak lux on the target (related to luminance of your LED as seen by your reflector or aspheric lens)?


My expectation is that you'd lose about 30-40% of the lumens and gain ~10+% in lux. Removing the dome causes more light to totally interally reflect (TIR) and is therefore trapped inside the substrate. At the same time, some of this light which is trapped will make a second pass through the phosphor, get absorbed by the phosphor, and be re-emitted. This will result in the LED taking on a greenish hue.

Because the die is apparently smaller (no more magnification from the dome) the light generated by the second pass through the phosphor will result in a slight increase in the surface brightness (lumens/apparent die size) which will produce a modest gain in throw (peak lux incident on the target).

However, efficiency of the system (in lumens out of the light / watts from the battery) will drop significantly. Throw (peak lux on the target) will improve marginally.

RE: adding a secondary lens not affecting throw (lux on target)

This is true. Adding an additional lens has the effect of both increasing the acceptance angle of the aspheric lens and magnifying the image of the LED die.

This means lumens that would otherwise be absorbed by the bezel of the flashlight end up being collected by the lens. Peak lux at the center the target will be the same, but because this secondary lens will magnify the LED die, a larger area will be illuminated. Total efficiency of the system will be improved, but throw will be unchanged.

I have many dome , dedomed , reflector , aspheric lenses flashlights, and tested.

LED domes = narrow beam = good for aspheric lens.
LED dedomed = wide beam almost 180 degree = reflect to reflector, increase throw = good for Throwking Reflcetor.

The explanation I have for this is that for LEDs like the Cree XR-E in particular, the emission pattern with the dome is not intended to be lambertian (LED surface appears equally "bright" in all directions), but focused into a somwhat narrower range of angles. By removing the dome, the LED becomes is emitted into a greater angles. The problem is much of this light is emitted into an angle that is so great that is greater than the critical angle in the silicone medium, causing it to totally internally reflect.

A better way to achieve more throw from a reflector-based light is to use an emitter which is designed to be lambertian in the first place (like the XM-L or XP-E packages) -- this will give you the benefit of wider beam angle without the inefficiency/TIR-losses associated with de-doming.

 

[midget]

If I could hijack this thread (very briefly)... what does blacking out the reflector do to help promote throw?

I have two DX aspheric lenses mounted on some L2 bodies and solar force drop-ins. should I black out these reflectors? Right now I am shooting that square-image light beam with that kinda gross spillage around the edges. It didn't really bother me. Will blacking out the reflector increase the performance?

 

[2xTrinity]

If I could hijack this thread (very briefly)... what does blacking out the reflector do to help promote throw?

I have two DX aspheric lenses mounted on some L2 bodies and solar force drop-ins. should I black out these reflectors? Right now I am shooting that square-image light beam with that kinda gross spillage around the edges. It didn't really bother me. Will blacking out the reflector increase the performance?

It looks like many in this thread are defining throw to mean, strictly, peak lux on the target being illuminated. This will obviously not change. I'd consider "throw" to be a subjective term for a light that is relatively narrow (range of angles between peak intensity at dead center of the beam and say, 10% intensity is small).

If the spill lighting up the foreground enough to cause your pupil to constrict slightly, then that will make it harder to see your far away target, and in that circumstance, blacking it out may help performance. This is a pretty complex problem that will depend on the geography of where you're using the light and isn't a straightforward question to answer using simple measurements or to quantify with photometric units (lumens, lux, etc). If the spill isn't bothering you, I wouldn't bother blacking it out TBH.

 

[saabluster]

Remember Ra & Dr. June's threads & experimental proof? In aspehrical set-up, Adding secondary lens infront of led does not change throw. Removing the dome, which is a secondary lens, does not change throw if the led remains unchanged. But in this case, after de-dome, the led lose about 30% brightness , thus lose throw.

hubba hubba hubba who do you trust? I am telling you unequivocally that a dedomed LED helps an aspheric throw better.

You can take the following to the bank.

-A secondary "precollimator" lens can increase throw with certain lenses.
-Dedomed LEDs have better throw in both aspheric and reflector setups.

If anyone says this is wrong they are either lying or misinformed.

 

[seven11]

hubba hubba hubba who do you trust? I am telling you unequivocally that a dedomed LED helps an aspheric throw better.

You can take the following to the bank.

-A secondary "precollimator" lens can increase throw with certain lenses.
-Dedomed LEDs have better throw in both aspheric and reflector setups.

If anyone says this is wrong they are either lying or misinformed.

I'd go with that.

 

[ma_sha1]

hubba hubba hubba who do you trust? I am telling you unequivocally that a dedomed LED helps an aspheric throw better.

You can take the following to the bank.

-A secondary "precollimator" lens can increase throw with certain lenses.
-Dedomed LEDs have better throw in both aspheric and reflector setups.

If anyone says this is wrong they are either lying or misinformed.

I am scientist by trade, I trust no one but data. Thus Ra & Dr. Jones' data had my vote.

If you can provide data, I can be convinced if they are solid & test were done well controlled & can be reproduced by the peers .

 

[BLUE LED]

Agreed good science is reproducible. It is an interesting concept that may warrant further investigation.

 

[bshanahan14rulz]

I think part of SaabLuster's business is maximizing throw, so I don't imagine he'd publish his more recent findings or anything.

MaSha, take a laser and measure its divergence after focusing it as well as you can. Then, shine it through some binoculars focused to infinity, and focus the laser to minimize its divergence and record it. You will see that the divergence is measurably lower. The second (and third, and fourth, however many lenses your binoculars have) will have increased the throw of the light.

Take a blue LED of a given power output at a specific rated current and measure its "throw" with an aspheric lens Take a laser of same wavelength and power output, and measure its "throw" using no lens except the one aspheric (i.e. remove the tiny lens that comes with most lasers). You will see that the laser throws farther, only because it has a smaller apparent area.

These aren't scientific experiments, but I'm not a scientist, nor do I have any grants to pay for equipment. I just have what I can scavenge, it's my hobby to understand light.

 

[Walterk]

You will see that the divergence is measurably lower. The second (and third, and fourth, however many lenses your binoculars have) will have increased the throw of the light.

Yes you will have a more narrow beam.
But I don't see why it would result in higher candela.
Mentioned experiences tell otherwise then your binoculars suggestion, unless you found 100% optical efficiency, which would be a doubtful claim at least.

You would have higher 'perceived throw' only if you express throw as a ratio between candela and divergence.
With 'correcting for abberations by additional lenses' you can't get more efficiency from your your system as the weakest link.
Not from emperical, theoretical nor holistic point of view.

 

[Walterk]

Post deleted (off-topic)

 

[bshanahan14rulz]

Yes you will have a more narrow beam.
But I don't see why it would result in higher candela.

I meant widening the beam, which would reduce the lux but also reduce divergence, right?

Mentioned experiences tell otherwise then your binoculars suggestion, unless you found 100% optical efficiency, which would be a doubtful claim at least.

You would have higher 'perceived throw' only if you express throw as a ratio between candela and divergence.

This is why "throw" pisses me off. Nobody says what it is, it's some subjective term that can mean lots of different things to different people. To me, it is a laymans term for low divergence.

With 'correcting for abberations by additional lenses' you can't get more efficiency from your your system as the weakest link.
Not from emperical, theoretical nor holistic point of view.

Too many big words for me, but I think you are saying that adding lenses will reduce the efficiency of the overall system. Yep, I agree. I'm saying sacrifice some optical efficiency and beam diameter to decrease divergence. Also, binoculars aren't meant to be super efficient, just to be accurate, so the comment above about my owning some fancy 100+%

 

[Walterk]

binoculars aren't meant to be super efficient, just to be accurate

Binoculairs can only be as accurate as your eye can interpret what the lenses brings you.
Light gathering is the most important to deliver contrast, so you distinguish shapes and colours.
The bino's and telescopes with highest magnification ( read smallest beam angle) have the lowest lightgathering.
Just like flashlights, entry and exit apertures determine lightgathering / lux.
Bigger diameter exit lens give higher lightgather / lux, higher magnification / narrow beam comes from smaller oculair / led-die.

Huygens used only 2 lenses in some of his telescopes, and he got plenty magnification. So don't overdo with lenses.

I agree that efficiency is no argument as long as the beam is satisfying.

 

[fyrstormer]

How could removing the pre-collimator lense on an XR-E possibly improve throw? It will let more light go to waste. I understand that throw is affected by the size of the die image facing the outermost lense, and de-doming the XR-E will reduce the die image. However, throw is also affected by the amount of light exiting the flashlight, and de-doming the XR-E it will also cause more light to be lost against the inside walls of the focusing chamber. The size of the beam might be smaller without a dome, but it will also be dimmer, given the same power consumption. I don't see how there can be any significant improvement one way or the other. The only significant difference I can think of is the size of the beam, and I would think a wider beam from a dome-intact XR-E would be more useful for seeing distant objects, since distant objects tend to be kinda small due to perspective.

 

[bshanahan14rulz]

Walterk: Thanks for those examples of real-world multi-lens optics. I understand now why binoculars are summarized by their collecting lens size and magnification. So, to have a good contrast and high magnification, you'd need very unwieldy, large lenses at the end and big space between the large lens and the eye lens. So I guess the main reason they use more than two lenses is to sacrifice overall efficiency for a more compact handheld device, since with each added lens more losses are introduced into the system from absorption and reflection?

In the laser hobby, the most widely used lens system is a galilean beam expander, due to its simplicity. The main drawback to these are that to achieve lower and lower far field divergence, you have to use larger and larger lenses, and/or larger gap between the two lenses. I can barely ray-trace a single lens, not to even mention 3 or 4, but I would guess that if compactness were an issue, there should be ways to add lenses to reduce the length of the system while increasing losses in the lenses?

Thanks for the insight, trying to learn optics hands-on without having any known optics to play with, maybe my next project should be classifying and measuring my lenses.

fyrstormer:
I think that is the meat of the question here. Dedoming the LED will provide a smaller source, and we can better collimate it. However, the loss in lumens from both a more lossy light extraction from LED package AND a larger "cone" of light exiting from the LED would both contribute to a lower overall output has the potential to cancel out the benefits of dedoming for a smaller source.

 

[fyrstormer]

So I'm inclined to say, if de-doming lets you move the main lense closer to the emitter surface, then it might be an improvement; otherwise, it's not likely to make any difference.

 

[DIWdiver]

If you want to increase throw, dump that piece of c---- DX aspheric and put in an Ahorton. It will gather vastly more light. The focus is a few millimeters from the lens, instead of tens of millimeters. Having tried both personally, I can say the difference is stunning.

And before you ask, no, I didn't take beamshots. I took one look, dropped the DX in a box and haven't picked it up since. I dove my light with Ahorton aspheric and XML the last two weekends. Awesome!

 

[Walterk]

@bshananan: Well you brought the binos up . Have you tested it yet?
Google binoculars at laserpointerforum and you'll read some experiences: decreases throw, decreases divergence.

Awaiting my shipping from Trout for the Ahorton's lens but he must be busy cycling or something...