# XM-L Color Separation



## edroedro (Feb 12, 2011)

Has anyone noticed the large amount of color separation on the XM-L?

The low angle light on my XM-Ls is very warm and the high level light is very blue.



I'm sure it mixes together to give the the nominal color temperature in a sphere.



I have noticed this on most other LEDs, but it seems much worse on the XM-L.

Has anyone noticed this phenomenon?


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## SlowPoke808 (Aug 4, 2011)

I've witnessed this first-hand and there are numerous posts in which people are reporting greenish or yellowish colors around the hotspot and purple in the spill area of the beam. We're probably just seeing the chromatic dispersion of the light as it exits the XM-L dome. The large surface area of the die relative to the dome guarantees that a lot of light will pass through the surface of dome at an angle and disperse (only light emitted from the very center of the die will pass through perfectly perpendicular to the dome's surface and thus not disperse).

I'm guessing that all XM-L emitters are doing this but some reflectors happen to focus in such a way that the separate colors are concentrated, making the colors very noticeable. Other reflectors probably focus differently and mix the light to make it appear white again.


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## qwertyydude (Aug 5, 2011)

Throwy SMO reflectors really amplify this with a hotspot that's noticeably yellower than the spill.


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## richpalm (Aug 5, 2011)

For me, orange peel reflectors or frosted optics reduce or eliminate the variation.

Rich


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## HooNz (Aug 6, 2011)

I just checked mine , its blue-ier on low and white-er on high , a T6


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## Mike S (Aug 6, 2011)

All the T6 bin XML's I've tested show the same green/yellow light at its edges.







SST-50/90 orange peel reflectors (12° and 28°) seem to reflect that light into the hotspot.


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## SlowPoke808 (Aug 10, 2011)

Now I'm irritated with this. I just finished my first Mag 3C mod with a 5000K XM-L T6 from Cutter. Check out the colors in this photo with the head removed:





The hotspot is VERY yellow/green!





These photos were taken with an old, low-end camera but they look fairly close to what I'm seeing in real life. The first photo was taken with the Mag almost on it's side with a piece of white paper underneath. In the second photo I'm just aiming the assembled light at the ceiling.

It looks to me like this reflector (stock plastic Mag incan) is concentrating the yellow/green light coming out the sides of the emitter right in the hotspot and the blue/purple light is mostly going out the front without being reflected. Since the blue/purple is not concentrated enough, especially where the yellow/green is, it can't recombine in equal proportions to make white light again.

I may have to add some texture to the reflector or something because I can't stand that color! It's too bad though, because I didn't want to give up any throw.


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## Harold_B (Aug 11, 2011)

I recall this coming up before the crash and there's an abreviated thread still out there. I have a model of an XM-L for lighting simulations although I haven't fine tuned the phosphor parameters to exactly match the manufacturer specs with regard to the spectrums. I ran some simulations anyway as part of the discussion as to why there is color seperation in this product. The reason the XM-L has color seperation isn't the dome and some kind of rainbow effect, it is the path length of the source light through the phosphor layer. There is a good reference to what I mean in this paper by Osram: http://www.osti.gov/bridge/servlets/purl/963890-7R3mLc/963890.pdf

The off-axis color seperation can be simulated in software that has volumetric fluorescing / down conversion capablity. In this image you can see the ray are rather squiggly at the emitter surface as they make their way through the phosphor particles but they do not deviate much if at all when exiting the dome: http://i1083.photobucket.com/albums/j390/Harold_LF/XM-L-RAY.jpg

These are some screen shots of the detector with the CCT measured at various angles off-axis:
http://i1083.photobucket.com/albums/j390/Harold_LF/XM-L-CENTER.jpg
http://i1083.photobucket.com/albums/j390/Harold_LF/XM-L-MID.jpg
http://i1083.photobucket.com/albums/j390/Harold_LF/XM-L-LOW.jpg

For kicks I stuck a Carlco optic in the path and ran a simulation and replicated the same basic patterns as shots above:
http://i1083.photobucket.com/albums/j390/Harold_LF/XM-L-WITHOPTIC.jpg

Doesn't fix the problem but now you know why it's there.


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## SlowPoke808 (Aug 11, 2011)

Now that is really interesting! Thanks for sharing that paper. I'm still reading through it. I'm hoping to see an emitter configured like the one on page 13 in production in the near future!

Are you able to run a simulation on the XM-L without the dome? How different does it look?

I don't see what makes the XM-L unique as far as color separation goes. Shouldn't we be seeing the same thing with the XP-G for instance? Maybe it's happening on a smaller scale so it's less noticeable?

I'm also curious about this picture: http://i1083.photobucket.com/albums/...F/XM-L-RAY.jpg
You are right when you say that the path does not deviate much when it exits the dome. What refractive index did you plug in for the dome material? Shouldn't we be seeing much more refraction (unless this is an underwater simulation  )? It's obvious that there's a lot of refraction going on when you look at an XM-L in real life because the die looks all distorted when viewed at an angle, mostly on the far side of the die as expected...


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## Harold_B (Aug 11, 2011)

The light entering the dome, reflecting from the die, exiting the dome and entering your eye will take a completely different path than the light being emitted from the die. The purpose of the dome and the reason it is effective and the shape of choice for most LEDs is that the interface surface between the air and the silicone encapsulant is near normal to the light emitted from the die. One thing to keep in mind about the screen shots is that they are CAD models and lighting simulations, not renderings. That is to say that they are dimensionally correct to the micron when possible, every surface and material is defined by optical parameters, but the distortion you would actually see is not represented correctly.

This is the RI I used for the dome. It is a silicone encapsulant specific for high temp / high power LEDs: http://i1083.photobucket.com/albums/j390/Harold_LF/SILICONERI.jpg
can't post the name due to NDA.

I haven't used the XP-G to any great extent so I can't say that I have or have not had the effect in our samples. The off-axis color seperation can be more pronounced depending on the size of the die, the thickness of the phosphor layer, and the layering method. I know there are ways to mitigate the problem (Rebels don't have an issue that I am aware of) but any source stuck in a parabolic reflector will suffer from some systematic chromic distortion.

I've read a lot of patents and papers about filters on or in LEDs like the one you mention on page 13 and they seem like they would be really expensive to produce, particularly on a dome.


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## SlowPoke808 (Aug 12, 2011)

Harold_B said:


> The light entering the dome, reflecting from the die, exiting the dome and entering your eye will take a completely different path than the light being emitted from the die.


This is true only up to the point where the light leaves the die. If the paths of the light entering your eye were different after that point then the die would appear to change shape when you turn the LED on.



Harold_B said:


> One thing to keep in mind about the screen shots is that they are CAD models and lighting simulations, not renderings. That is to say that they are dimensionally correct to the micron when possible, every surface and material is defined by optical parameters, but the distortion you would actually see is not represented correctly.


I think your representation should still be very accurate. I took another look at the picture and noticed that some paths do indeed refract significantly. These are the ones that are emitted from one edge or corner of the die and exit the dome on the extreme opposite side. I didn't didn't notice this at first, probably because the number of paths drawn are relatively sparse.

Do you still have easy access to the simulation software? It would be really interesting to run a simulation with light being emitted from only one point on the very corner of the die. I'm almost certain that we'd see a very distinct pattern appear. I would still like to see the simulation run without the dome as well.

In any case, I'm only brainstorming here to try to come up with a new way to mitigate the color separation when using XM-L emitters.:thinking: I'm just a consumer so I have to work with what I can afford to buy and the XM-L seems to be producing the most bang for the buck at the moment.

Thanks for sharing your research. Keep it coming!


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## SlowPoke808 (Aug 12, 2011)

Has anyone seen or used this multifaceted reflector? This might do the trick! Too bad they don't have Mag-sized ones...


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## Canuke (Aug 13, 2011)

If this phenomenon were a function of refractive index, wouldn't it be much less prominent with the XR-E package? I see just as much of this effect with those emitters. 

On the other hand, my USV0I Seoul emitters do not seem to show this issue much at all, despite having the same sort of dome.

I've always thought that this effect was due to phosphor having a thicker accumulation around the edge of the die than on its top face.

I seem to remember some folks around here removing domes from emitters; do bare dice show this pattern?


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## SlowPoke808 (Aug 15, 2011)

Harold's point about the particular path the light takes through the phosphor layer totally makes sense and it explains why you would get different colors before it even exits the dome. Assuming that your die is flat and the phosphor layer is uniform in thickness, you would expect a bluer color from the light that's passing through the phosphor layer perpendicular to the phosphor plane. Light exiting at high angles (more parallel) to the plane will have to pass through much more of the yellow phosphor material and result in a yellower tint (if I'm understanding things correctly).

Refraction from the dome would further enhance the color separation, but you would still expect this to be happening with the XP-E if the die/phosphor layer construction is similar to the XP-G and XM-L. The only way to really tell would be to run some tests without the domes. Has anyone out there been able to de-dome any of these LEDs without damaging the phosphor layers? If so, we need some side profile shots without reflectors!

I don't know how the dies are manufactured but if it were possible to create a die with a textured surface (dimpled perhaps) that might help to randomize the amount of phosphor the emitted light passes through at any angle to create a uniform color.


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## bshanahan14rulz (Aug 17, 2011)

SlowPoke808 said:


> I don't know how the dies are manufactured but if it were possible to create a die with a textured surface (dimpled perhaps) that might help to randomize the amount of phosphor the emitted light passes through at any angle to create a uniform color.


Good thinking! They do that. This is an old sample teardown, but still neat pics
http://www.yole-dev.com/pagesAn/products/Report_sample/mu4.pdf


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## saabluster (Aug 17, 2011)

SlowPoke808 said:


> Harold's point about the particular path the light takes through the phosphor layer totally makes sense and it explains why you would get different colors before it even exits the dome. Assuming that your die is flat and the phosphor layer is uniform in thickness, you would expect a bluer color from the light that's passing through the phosphor layer perpendicular to the phosphor plane. Light exiting at high angles (more parallel) to the plane will have to pass through much more of the yellow phosphor material and result in a yellower tint (if I'm understanding things correctly).
> 
> Refraction from the dome would further enhance the color separation, but you would still expect this to be happening with the XP-E if the die/phosphor layer construction is similar to the XP-G and XM-L. The only way to really tell would be to run some tests without the domes. Has anyone out there been able to de-dome any of these LEDs without damaging the phosphor layers? If so, we need some side profile shots without reflectors!
> 
> I don't know how the dies are manufactured but if it were possible to create a die with a textured surface (dimpled perhaps) that might help to randomize the amount of phosphor the emitted light passes through at any angle to create a uniform color.


 
Cree's HEW XP-E does essentially do this. Not via dimples but a raised structure. This effect of the changing color based on angle has been known and understood here on CPF for many many years. Sorry I didn't chime in any earlier but yes Harold got it right.


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## SlowPoke808 (Aug 18, 2011)

bshanahan14rulz said:


> Good thinking! They do that. This is an old sample teardown, but still neat pics
> http://www.yole-dev.com/pagesAn/products/Report_sample/mu4.pdf


 
This paper has some very good pictures. I didn't see any reference to a dimpled surface though. Figures 4.2 and 4.18 reveal some microscopic texture on the surface of the phosphor layer but it is flat in shape overall so you will still have yellower light being emitted at high angles. I was thinking larger dimples. Imagine that same picture of the die having a surface like a golf ball with deep dimples. This would cause the yellower light to be emitted at a wide range of angles relative to the overall die plane, not just very high angles. The same goes for the bluer light. It would be emitted at all sorts of angles, not just the low angles. The resulting mixing should produce a much more uniform, whiter light overall.


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## SlowPoke808 (Aug 18, 2011)

saabluster said:


> Cree's HEW XP-E does essentially do this. Not via dimples but a raised structure. This effect of the changing color based on angle has been known and understood here on CPF for many many years. Sorry I didn't chime in any earlier but yes Harold got it right.


 
I looked at the datasheet for the High Efficiency XP-E but I didn't notice anything different from the regular XP-E other than the diffused dome (that's definitely another way to reduce apparent color separation though!) Do you have any more info on this raised structure?


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## saabluster (Aug 18, 2011)

SlowPoke808 said:


> This paper has some very good pictures. I didn't see any reference to a dimpled surface though. Figures 4.2 and 4.18 reveal some microscopic texture on the surface of the phosphor layer but it is flat in shape overall so you will still have yellower light being emitted at high angles. I was thinking larger dimples. Imagine that same picture of the die having a surface like a golf ball with deep dimples. This would cause the yellower light to be emitted at a wide range of angles relative to the overall die plane, not just very high angles. The same goes for the bluer light. It would be emitted at all sorts of angles, not just the low angles. The resulting mixing should produce a much more uniform, whiter light overall.


You are correct. The rough texture on that LED is not to reduce the variance in color but to aid in light extraction. 



SlowPoke808 said:


> I looked at the datasheet for the High Efficiency XP-E but I didn't notice anything different from the regular XP-E other than the diffused dome (that's definitely another way to reduce apparent color separation though!) Do you have any more info on this raised structure?


I tore down a HEW the other day and was amazed at what I found. The structured is raised and has cut angles and is just beautiful to look at. It looks like a cut gem stone. I was going to post some pictures but then Cree released their royal blue version the other day and along with it was a nice picture that shows it well.


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## SlowPoke808 (Aug 18, 2011)

saabluster said:


> I tore down a HEW the other day and was amazed at what I found. The structured is raised and has cut angles and is just beautiful to look at. It looks like a cut gem stone. I was going to post some pictures but then Cree released their royal blue version the other day and along with it was a nice picture that shows it well.



Whoa, that looks cool!!! I hope they start making the XM-L emitters like that! That should fix the color problems!


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## bshanahan14rulz (Aug 19, 2011)

Is it just a slightly different encapsulant to ease the transition of refractive indices, I wonder? Very cool to look at. Is it made of approximately the same material as the dome?


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## Roger555 (Aug 31, 2011)

I just fired up my first XML and was surprised to find how pronounced the yellowish halo is around the beam  . Does the P7 do this too? Whats the next brightest LED with a smilier footprint to the XML that mixes the color better without extra optics? Efficiency is not too much of a concern here.


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## qwertyydude (Sep 1, 2011)

P7 does not have the annoying color separation, more efficient would be the MC-E, it being another 4 die it behaves pretty much like the P7 but projects a just slightly bigger hotspot.


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## easilyled (Sep 1, 2011)

Roger555 said:


> I just fired up my first XML and was surprised to find how pronounced the yellowish halo is around the beam  . Does the P7 do this too? Whats the next brightest LED with a smilier footprint to the XML that mixes the color better without extra optics? Efficiency is not too much of a concern here.



I would say the SST-50. I have noticed that the tint is much more even in the beam for my SST-50 lights although the output, whilst still very bright, is significantly less so in similar set-ups.

The SST-50 is a large, single-die emitter like the XML and therefore has a similar footprint with the same optics.


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## zzonbi (Sep 23, 2011)

bshanahan14rulz said:


> Very cool to look at.


 
It's a new die, without bond wires and officially over 0.5 efficient!


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## Roger555 (Dec 15, 2011)

Hey guys need some advise on XM-L's. I fired up my first pair U2 XML (2T) and they are bright as hell but they have the green halo like the pictures seen above. I'm a bit worried about trying another bin as I do not! want the green at all. 

I'm looking for a cool white 7000K and would prefer no tint at all. Will I have any halo problems with the T6 from Cutter (*Cutter-XML14RND-T6) Bin 1D ??
*


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## bshanahan14rulz (Dec 16, 2011)

Could it have anything to do with the sides of the dice not being covered by the conformal YAG coating?


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## Roger555 (Dec 16, 2011)

bshanahan14rulz said:


> Could it have anything to do with the sides of the dice not being covered by the conformal YAG coating?



Not sure what that is but after a google search its something that help blend or promote uniform color distribution? How can I tell if its gone? Is it fixable?


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## Roger555 (Dec 20, 2011)

Anyone? Maybe i'd have better luck with XP-G's?


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## Harold_B (Dec 20, 2011)

All of the XM-L samples I have tested have the color separation over the viewing axis. There's nothing "wrong" with your samples and it is likely that any new samples will have the same issue to a degree. The cooler the color the temperature the less noticeable the issue should be since the phosphor layer is less dense. Your level of tolerance will depend on the application. If it really bothers you you might contact a Cree rep and ask if they will provide the color separation over the viewing axis data. The Rebel ES data is available under a separate spec though I can't seem to lay my hands on it at the moment.

You might also try a textured surface on a parabolic reflector or a diffusing optic in the path (DLP projectors use a mixing rod or Fly eye lens for example). There's another thread about filters floating around and they would work as well although it would change the color temperature and drop the output.


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## fyrstormer (Dec 20, 2011)

Yep, seen it on multiple lights. Once again Cree sacrifices beam quality for maximum output. I suppose most people don't care, and compared to a Maglite beam, anything is better, including the old 5mm LEDs we used to use back at the turn of the century.

The Luminus SST-50 produces a much nicer beam -- it has to, because the same die is used to backlight TV screens, and people would lose their s**t if there were alternating blobs of blue and yellow in their TV screens.


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## Harold_B (Dec 20, 2011)

Depending on the supplier and the quantities ordered the XM-L can be had for 1/2 to 2/3 of the cost of the SST-50. Better performance costs more typically so it would seem like an unfair assertion that Cree is not taking quality into consideration. They make a high output, large die product for an excellent price. That's not to say that they are the only or best product on the market but the XM-L isn't intended for backlighting applications. I'm not looking looking to harass you, just my opinion.


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## easilyled (Dec 21, 2011)

fyrstormer said:


> Yep, seen it on multiple lights. Once again Cree sacrifices beam quality for maximum output. I suppose most people don't care, and compared to a Maglite beam, anything is better, including the old 5mm LEDs we used to use back at the turn of the century.
> 
> The Luminus SST-50 produces a much nicer beam -- it has to, because the same die is used to backlight TV screens, and people would lose their s**t if there were alternating blobs of blue and yellow in their TV screens.



I wouldn't say that the beam quality is terrible with the XM-L, particularly in outdoor flashlight applications where in fact its probably quite advantageous to have the central hotspot warmer than the periphery for throw lights picking out targets. 

In any case the price of the XM-L is much less than that of an SST-50 and the consumer has the choice of either option.

Personally, I know I am a heathen when it comes to beam quality, but I would choose the XM-L even if the prices were the other way around. I prefer the significantly higher output, greater efficiency and throw potential.
:fail:


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## BvanderG (Dec 21, 2011)

Have any of you tested or simulated the XM-L for the level of color separation when using any of these secondary optics:

Ledil IRIS-XM series (C4F12104)
Kathod PL136915 lens
Carclo #10025_1 50mm catadioptic
Carclo #10158_ref1 60mm catadioptic
Fraen "35mm narrow beam for Cree XM-L"
We're working on a narrow-beam spot, but excessive separation might be problematic. Thanks.


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## Roger555 (Dec 21, 2011)

Anyone recommend a good source for the SST-50 ?? For my application uniform beam trumps efficiently. I've tried all kinds of optics none of them help with the separation, just move it around.


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## Harold_B (Dec 21, 2011)

BvanderG - What is the timing for your project? I have a moderately accurate model of the XM-L including the color separation over the viewing axis (a bulk phosphor modeling software is required to this) and I could add the optics for a quick simulation if they are available as STEP or iges files. If you can post the links I can get it done in a couple hours but it would need to happen tomorrow as I'll be out of the office for a week. This would be SWAG relatively speaking since we haven't verified the XM-L on the Goniometer. 

Roger - can we post suggestions for vendors or will that get deleted? I did a quick Google and found pricing (just enter the country in after SST-50 in search field).


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## BvanderG (Dec 22, 2011)

Harold, thanks for the offer. For the Ledil, the details page is http://www.ledil.fi/node/2/p/2650. I asked for the photometric files and they sent me two IES files... Not sure whether you'll find what you need there.

The Kathod is at http://www.khatod.com/cms/pl1369_se...or_cree_xlamp_xm_l_leds-2678537-2678537.html# but no sign of those files either. 

The Carclo must be too new to be found on http://www.carclo-optics.com/opticselect/ I guess...

Fraen doesn't have the XM-L in its list at http://www.fraensrl.com/prodinfo.html#

Conclusion: these lenses are very new and not fully documented yet.  If we see any new data, I'll come back.


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## Harold_B (Dec 22, 2011)

Went to the Ledil page and requested the solid model. Now waiting for it to arrive.... I'll see what I can find on the Carlco over the next few days.


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## mpteach (Dec 22, 2011)

saabluster said:


> You are correct. The rough texture on that LED is not to reduce the variance in color but to aid in light extraction.
> 
> 
> I tore down a HEW the other day and was amazed at what I found. The structured is raised and has cut angles and is just beautiful to look at. It looks like a cut gem stone. I was going to post some pictures but then Cree released their royal blue version the other day and along with it was a nice picture that shows it well.



Well if it is moissanite (SiC) then it is a gem. Did you notice the gem having alot of brilliance or fire??


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## bshanahan14rulz (Dec 22, 2011)

Cree excels in SiC processing, but I do not believe they produce Moissanite. 

I still don't think that structure has anything to do with the die, but I'm just saying that because there's no easy way to photoetch a bunch of funky pyramids onto a wafer of LEDs and then shear them. I'm thinking it is something to ease the refractive transition from the active layer to air.

That, or it's a CWPS device.


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## Harold_B (Dec 23, 2011)

BvanderG - contacted Ledil and was informed that they do not supply 3D models (despite what the website says apparently). If you would like a ray trace of the Ledil optic you will need to have them run the trace and it will be in Zemax. Too bad, I would like to build a library of Ledil optics to recommend to our clients for illumination projects that don't require custom optics but I'm not about to out source our core business (photonics engineering) to a vendor.


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## mpteach (Dec 23, 2011)

http://www.cree.com/press/press_detail.asp?i=1292506660553 Direct attach is a flip chip technology. Maybe thats the substrate on top??


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## saabluster (Dec 25, 2011)

mpteach said:


> Well if it is moissanite (SiC) then it is a gem. Did you notice the gem having alot of brilliance or fire??


In fact it did. A blue fire.



bshanahan14rulz said:


> Cree excels in SiC processing, but I do not believe they produce Moissanite.
> 
> I still don't think that structure has anything to do with the die, but I'm just saying that because there's no easy way to photoetch a bunch of funky pyramids onto a wafer of LEDs and then shear them. I'm thinking it is something to ease the refractive transition from the active layer to air.
> 
> That, or it's a CWPS device.


Cree is the only one that I know of that produces it actually. They are the ones who figured out how to create synthetic moissanite. Not sure what that structure is made of but there certainly isn't any reason it couldn't be moissanite. And yes indeed it is part of the die structure as can be seen in the die's datasheet.


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## lilmarvin4064 (Jan 9, 2012)

Harold_B said:


> I haven't used the XP-G to any great extent so I can't say that I have or have not had the effect in our samples. The off-axis color seperation can be more pronounced depending on the size of the die, the thickness of the phosphor layer, and the layering method. I know there are ways to mitigate the problem (Rebels don't have an issue that I am aware of) but any source stuck in a parabolic reflector will suffer from some systematic chromic distortion.



I have a bunch of 3500K ANSI Rebels and I can assure you, they have the same problem; warmer on the edges. The 93 CRI Seoul P4s also have this issue as well. I think all the high dome emitters suffer this problem.

I'm glad I saw this thread to remind me of this issue. I'm going to have to redesign a fixed lighting project I'm working on, before I drop a bunch of $.


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## evgeniy (Feb 3, 2012)

CREE XP-G has same problem with different color temp ?


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## saabluster (Feb 3, 2012)

lilmarvin4064 said:


> I have a bunch of 3500K ANSI Rebels and I can assure you, they have the same problem; warmer on the edges. The 93 CRI Seoul P4s also have this issue as well. I think all the high dome emitters suffer this problem.
> 
> I'm glad I saw this thread to remind me of this issue. I'm going to have to redesign a fixed lighting project I'm working on, before I drop a bunch of $.



The issue is the large die allows for viewing at very oblique angles where the light is having to travel through a larger slice of phosphor. The 93 CRI Seoul's suffer from this as well even though they have a "small" die due to the phosphor deposition technique.


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## Hoop (Feb 7, 2012)

This is an unfortunate reality of XML's that people do not mention nearly enough in reviews and recommendations. It should be a mentioned caveat with most XML lights. I purchased an expensive ($350) triple xml only to be disappointed with the greenish multi color beam. I returned it. Lights with SST series leds are all I will buy at this point in time.


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## LowLumen (Aug 29, 2012)

I'm bumping this old thread as I have not seen this problem discussed elsewhere. 

I'm about ready to forget about using the XM-L for the problems with color separation. I was putting together a P60 dropin with an XM-L T5 3C, wanted to use OP reflector but Craig at Illumination Supply was out so I went ahead with the SMO reflector. Result: white spot, yellow corona, purple spill. I'm hoping an OP reflector will mix the colors enough to pass, but wondering how flashlight manufacturers deal with this issue

All my other lights are XP-G. (and Nichia 219's I've used are great) Don't suffer nearly so much from this problem.

I put together a bare XM-L 'mule light', same problem of purple center and yellow to green at the edge. Trying to come up with a diffuser to even out and mix the colors. 

The other 2 XM-L ended up behind amber filters in a security light in the driveway. ...that worked well!
If a P60 OP reflector can't put the colors back together again in an acceptable way, I think this will be my last XM-L.


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## RoGuE_StreaK (Aug 29, 2012)

You try stippling the SMO with clearcoat to simulate an OP?


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## fyrstormer (Aug 30, 2012)

Hoop said:


> This is an unfortunate reality of XML's that people do not mention nearly enough in reviews and recommendations. It should be a mentioned caveat with most XML lights. I purchased an expensive ($350) triple xml only to be disappointed with the greenish multi color beam. I returned it. Lights with SST series leds are all I will buy at this point in time.


It should be possible to retrofit any XM-L light with SST-50s at a reasonable cost.


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## fyrstormer (Aug 30, 2012)

LowLumen said:


> If a P60 OP reflector can't put the colors back together again in an acceptable way, I think this will be my last XM-L.


OP reflectors don't really blend the colors of the hotspot and the spill; their primary function is to blur small, localized beam artifacts caused by imperfect focus and poor emitter design.

The spill is light that emits nearly straight out the front of the emitter, and bypasses the reflector; the hotspot is light that emits at an oblique angle and bounces off the reflector. The spill and the hotspot are made from two separate "batches" of light rays, defined by the angle they're originally emitted. A reflector with enough texture to blend those two "batches" of light rays would also have too much texture to produce a distinct hotspot.


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## easilyled (Aug 30, 2012)

There are now high-CRI (90+) XM-Ls that Nailbender is offering in his P60 drop-ins.
Although the output bin is only S6 (one down from T2), he says that they still produce about 500 lumens which isn't bad for high-CRI leds.


They are apparently warm tinted - Nailbender describes them as "looking like Incans".
From my own observations, I find the separation less obvious in warmer (lower CCT) XM-Ls so I'm wondering if this holds true for these.


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## fyrstormer (Aug 30, 2012)

Well, the warmer versions have thicker phosphors, so that probably has something to do with it.


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## LowLumen (Aug 30, 2012)

I figured the OP reflector will not change the spill color (emits directly out the front without hitting the reflector) but was hoping the OP might blend the white hot spot with the yellow corona ring better. I have played with the focus adjustment on the SMO reflector; it changes the relative sizes of the spot and corona, but doesn't seem to do all that much with the color separation. I will go ahead and order some OP P60 reflectors. ...for both XM-L and XP-G. If it doesn't work out, I swap to XP-G or 219 and be done with XM-L. Thanks to all for your input on the issue.


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