# dedomed a xm-l with success



## ergotelis (Sep 2, 2011)

I don't have much time, i will write a few comments, later will post more details.
The led is a xm-l U2 2S from cutter, pure white color, was damaged during soldering, but dedomed with success. Can tell you how to do it with a good success rate. Same reflector, 7135 based driver same current, in a xeno F8V5 host:

Was a normal domed led in the flashlight,a xm-l U2 1A:
580 OTF and 9500 lux
now the dedomed xm-l,
488 OTF and 19450 lux!!!!!

Tint shift to ~4800K-5000K(!!!!) (as i said it is a U2 2S from cutter)
Looks slightly more yellow than 3S tint that i have, i think it is now in this category.

lost a 15% of light(assuming both were performing about the same,can't remember well, but i think they did perform the same in lumen testing before dedoming),got a neutral tint and got more than double increase in lux!

Now this is WOW!


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## Walterk (Sep 2, 2011)

Lame teaser, tell us more !

Did you remove the jelly dome in full?
Did you cut the dome off? How ?


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## qwertyydude (Sep 2, 2011)

How does this affect the color separation?


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## Morelite (Sep 2, 2011)

Please show and tell how you dedome it.


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## ergotelis (Sep 3, 2011)

I will try to dedome a third led in a while and i will give you all the info needed. The main idea of the method is with an oven or something to produce heat under the led. Not very high temperature, just the one needed to solder it to a pcb. Then the core becomes soft and delicate, with some press in specific points it is possible to dedome it with success. 
I removed the whole silicon core, it pops out like in sst50/sst90.
I don't know why the color changed, we will have to ask someone more expert or try to find some more information about it. Will post some photos too soon, sorry for not having the time currently to complete all the details.


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## richpalm (Sep 3, 2011)

Had a T6 that got dedomed when the GD file slipped. Still works but got horribly green hotspot.

No more filing stars!


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## Illum (Sep 4, 2011)

The dome of certain LEDs do assist in shifting the color a bit. I once sheared off the dome by accident on a CREE XRE CW and the output turned NW


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## bmmeadors (Sep 4, 2011)

Wow, with those lux numbers, this might be a candidate for a monster XM-L thrower! Cool find! :thumbsup:


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## Walterk (Sep 4, 2011)

Maybe you could measure the [email protected] meter of the led only (without reflector/lens) before and after?
Now that would give me a lot more insight...


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## Harold_B (Sep 4, 2011)

Pardon me for not knowing better but I don't quite understand the excitement over building a light with a de-domed XM-L. The issue for me is the ~ 20% drop in output as measured in lumens (OTF). The higher lux readings are likely because the light from the die will be more directional. The LED is reduced in output due the loss of out-coupling efficiency for the light emitted at a high viewing angle from the die.

I would be interested in measured spectral data gathered using a photogoniometer (as opposed to an integrating sphere) to understand the color shift. The XM-L has a lot of color separation over the viewing axis so it won't be a big surprise that the color temperature would shift with the dome removed.

We have de-domed a few LEDs ourselves including the XM-L except that we want everything off including the phosphor layer. Several hours soaking in IPA does the trick along with a couple of hours spent picking chunks of silicone off the die. The real challenge is not scratching the die surface or damaging the wire bonds.


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## MikeAusC (Sep 4, 2011)

Harold_B said:


> Pardon me for not knowing better but I don't quite understand the excitement over building a light with a de-domed XM-L. . . . . . The higher lux readings are likely because the light from the die will be more directional. . . . . .


 
I think you've answered your own question !

For some people the sole aim of building lights is to have the brightest spot, no matter how tiny it is.


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## Harold_B (Sep 4, 2011)

Well, perhaps so Mike. I understand the desire for a bright spot. That one is easy. Getting a brighter spot by making the LED more directional while making it less efficient (lowered output) might be more economical than capturing the low angle output and directing it to the spot using appropriate optics. It seems like a waste of potential output to me so I thought I'd ask in case I was missing something. Not that one approach would be absolutely right while the other is wrong, just asking a question.


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## RCantor (Sep 4, 2011)

Harold_B said:


> Pardon me for not knowing better but I don't quite understand the excitement over building a light with a de-domed XM-L. The issue for me is the ~ 20% drop in output as measured in lumens (OTF). The higher lux readings are likely because the light from the die will be more directional.


 
The excitement is about increasing the throw in a LED that's more floody most of the time.

(Oops - too late!) 

I have the need for both types of light. During the day I need to light up shadows 50 - 100 feet away so a small but very bright spot is exactly what I need for that light. It ends up being the single light I use most often but only because I can always choose from several lights for any night time task.


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## ergotelis (Sep 5, 2011)

Guys, the challenge is that you can get in a P60 host 20.000 lux with quite a good number of lumen. Ok, you get a loss, but still enough lumen out there. In these small tactical flashlight hotspot in needed to be bright. 
Harold, can you describe the procedure you did more analytically?
I will write about mine after i finish my third good success.( i have already 2 fails in the beginning, but i saw that heating the led to a high temperature helps the core to pop out)
My next step is to put the [email protected] in a 73mm reflector.


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## bmmeadors (Sep 5, 2011)

If we're looking for more lux in a P60 with little / no spill then maybe try an Ahorton's Aspheric.
If you are looking for less throw but with some spill then maybe try the Manafont (Ultrafire and sku: 6047) smooth parabolic reflector. There's a thread about it being used with an XP-E here. But I would think that it would give better throw than most P60 reflectors.
Whatever you decide to do with it, good luck, and please keep us updated. :thumbsup:


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## Walterk (Sep 5, 2011)

I was thinking of a dedomed led AND aspheric, the best purpose of a dedomed led.


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## easilyled (Sep 6, 2011)

Walterk said:


> I was thinking of a dedomed led AND aspheric, the best purpose of a dedomed led.


 
Now that's an interesting idea.


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## Al Combs (Sep 6, 2011)

ergotelis said:


> I don't know why the color changed, we will have to ask someone more expert or try to find some more information about it.


 
There was a thread a while back that touched on the subject of color shift and lumen loss in an LED with its dome removed. The dome of a white LED reflects some of the light back onto the surface of phosphor covering the blue emitter. This reflection causes a secondary yellow or orange fluorescence (cool or warm) that increases the lumen output. The secondary fluorescence has no blue component because it is absorbed by the phosphor. The color shift is caused by the absence of this extra yellow or orange when the dome is removed. Or more precisely a higher ratio of blue than an LED that has a dome.

If you look at the typical cool white LED's relative spectral power distribution graph in the data sheets, there is a transmission peak at ≈460nm that is about double the intensity of the level at 555nm. Significant enough to cause a color shift in its absence. The eye is much more sensitive to changes in color than intensity.

Someone in this other thread argued a reflection couldn't possibly increase output because there are no new photons being created by the reflection from the dome. Fluorescence is never 100% efficient. It can't create a beam of light more energetic than the original excitation source. It would be more beneficial to multicoat the dome and let the would be reflection pass right on through.

What they didn't to take into account is the lumen is by definition an adjustment of radiant flux power levels against the human eye's sensitivity to different wavelengths of light or luminous efficacy. The eye is ≈17 times more sensitive to 555nm green (peak photopic sensitivity) than it is to 460nm blue. The secondary fluorescence isn't creating new photons but it is converting them into wavelengths easier for the eye to see.


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## Harold_B (Sep 6, 2011)

I would be inclined to argue that the color shift due to the back reflected photons from the dome is not correct. GaN materials (InGan, P-Gan, ...) all have a high index of refraction and absorption coefficient in the visible wavelengths. Basically, anything that is a good emitter is a good absorber. The reflectivity of the die can be calculated using the refractive index which is about 2.45 at 450nM and then generating a best fit curve based on the real and imaginary components of the Reflection Coefficient. At the angles the photons would be back scattered to the die the reflectivity is about 6 - 25%. Mostly less than 10% for any visible wavelength striking the die at 0 to 45 degrees.

The purpose of the dome is light extraction. Making the ray path from the die encapsulant exit surface perpendicular at as many points as possible increases the out-coupling. Removing the dome creates loss at the surface due to TIR. If the light should make it back to the phosphor layer and be reabsorbed by a phosphor chrystal it will be scattered isotropically. That is most of it, if not all will be scattered into the die. Some remote phosphor designs use light recycling schemes but there is typically a gap between the phosphor layer and the die or there is a filter that prevents the scattered light from being sent back toward the die surface.


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## MikeAusC (Sep 6, 2011)

If light from the phosphor crystal is scattered isotropically, then the percentage of light going outwards would be the same, regardless of whether the blue light came from the chip - or reflected back from the dome.


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## Harold_B (Sep 6, 2011)

Yes, exactly. I'm probably not being very clear by trying to be brief. Approximately half of the light from the die (before or after down conversion) will be back scattered and re-absorbed by the die surface. Whatever else makes it back will suffer the same odds, plus the light is likely to be down converted to a wavelength not absorbed by the phosphors so it will be scattered (minus Fresnel loss). There are a ton of papers describing the efficiencies of phosphor down conversion and die modeling. This is a quick one that talks about back scatter and loss: http://lightingresearch.org/programs/solidstate/pdf/Zhu-SPIE6337.pdf


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## Al Combs (Sep 6, 2011)

Clearly you guys have a better understanding of the nature of LED's than I do. Here is a picture from one of the threads I was thinking about. Saabluster had taken a picture of a Luminus CBT-90 at the same current level and exposure. The two pictures are with and without a Wavien recycling collar. The CBT-90 has no Lambertian dome, so the increased output and shift in color temperature must have been caused by some other factor(s). If not secondary fluorescence from a reflected blue ray of light, what is the cause?


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## Harold_B (Sep 6, 2011)

Thanks for including the links in your post Al. Very helpful. Seven page thread, 11:30 at night. It's going to take a bit to digest all of that! At a glance I am only familiar with the Waiven optic via their patent info. I've not had a chance to mess with one. My first impression is that the optic is used to capture the emission for increased brightness (as opposed to increased output or making a change in the numerical aperture). Photos are nice but there's no substitute for hard data when it comes to assessing what's going on. I would be interested in data from a spectrometer and output measurements gathered using an integrating sphere to gage the extent of whatever changes were made.


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## ergotelis (Sep 8, 2011)

I think it is good to post here some first results with other reflectors.
With trustfire x7 @3,5amp on the led, i got ~172,000 lux(!).Led is one of my crappy t6 with one of the 3 wires of the core cut.But still works!Before,on this host it was a xm-l U2 2S performing ~100,000 lux. 

By the way, what is the record of lux number with a led?

On a trusfire C8 classic host with the 41mm widex31mm height smooth reflector, i [email protected] 2,7amp about 48000 lux. Owned my catapult v2 xm-l(!!!). Led is T6 3S with very few defects on the core. 
Till now, i have only dedomed 3 leds, 2 were ok on the one i got a wire cut, but still works,don't know if and how it affects its performance. Will see. The method as i said is at a good heat level of 150-180 C, to press gently the dome with tweezers from left and right of the wires and not close to them(we should not press the dome on the point where the wires are on the core).It will pop out after some time almost easily. But remember, this only for real crazy modders and those who don't have problem to waste their mine(well it is not fine to waste your money but i am maybe a lot more crazy)


Currently, trying to measure the lumen loss.


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## Walterk (Sep 8, 2011)

ergotelis said:


> I think it is good to post here some first results with other reflectors.
> By the way, what is the record of lux number with a led?



I got 2.100.000 cd with a single led.
But it means nothing for comparison, thats why I hope you would measure the [email protected] 1 meter without any reflector, tir or lens.
Because only with that measurement you can calculate the surface brightness of the modified led.
(If you have measured same set-up @1meter without optics before modding, then you really can tell its effect on throw....)


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## zzonbi (Sep 23, 2011)

Hello ergotelis! How well would the phosphor hold in the long run? Isn't its thin layer easy to scratch or to shed itself?


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## pieseal (Sep 27, 2011)

ergotelis said:


> I don't have much time, i will write a few comments, later will post more details.
> The led is a xm-l U2 2S from cutter, pure white color, was damaged during soldering, but dedomed with success. Can tell you how to do it with a good success rate. Same reflector, 7135 based driver same current, in a xeno F8V5 host:
> 
> Was a normal domed led in the flashlight,a xm-l U2 1A:
> ...


 can you share the pic?


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## Walterk (May 13, 2012)

How did the experiment work out?
You still like the de-domed XM-L?
Does it hold, or is the silicongel or phosphor acting up?


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## saabluster (May 15, 2012)

Walterk said:


> How did the experiment work out?
> You still like the de-domed XM-L?
> Does it hold, or is the silicongel or phosphor acting up?


The phosphor seems to hold up for me. I dedomed the LEDs in the latest LR+. I have destroyed a little less than half of the LEDs that I attempted to dedome. Sometimes it is the bond wires and other times it is the phosphor pulling up. Can be quite a nightmare. It does drastically increase performance though.


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## easilyled (May 15, 2012)

saabluster said:


> The phosphor seems to hold up for me. I dedomed the LEDs in the latest LR+. I have destroyed a little less than half of the LEDs that I attempted to dedome. Sometimes it is the bond wires and other times it is the phosphor pulling up. Can be quite a nightmare. It does drastically increase performance though.



To be pedantic, I'd say that it drastically increases _throw_ rather than performance.
Since the total output is actually decreased after dedoming, I don't think its correct to use the word performance.


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## Walterk (May 15, 2012)

easilyled said:


> To be pedantic, I'd say that it drastically increases _throw_ rather than performance.
> Since the total output is actually decreased after dedoming, I don't think its correct to use the word performance.



Yes we know, well I know from beamshots and experiences shared on CPF.

Talking only about the witnessed drop in lumen, please be clear on where it comes from:

Isn't it that the same lumen are emitted, but only in a viewingangle that is hard to collect by most reflectors and optics? 
(And thus most experiments so far have improved throw but not lumen)

So we should regard dedomed led not anymore as an ' almost-point-source ' and thus have to look for an other lenssystem to maintain lumen...

I think dedoming invites to step off the straightforward aspheric, and think more like MegaRay and other light projection lenssystems.
Or using smaller diameter (led filling more of the aperture of the whole lens), multiple lenses like described in the Ledlenser.


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## ergotelis (May 15, 2012)

I own you some photos and beamshots , sorry for not having already done this. On program it is to go out tomorrow in the same place i had taken some beamshots in the past, to show you how a dedomed led performs, among with other famous flashlights.
In general, a dedomed led has almost double the hotspot lux in the same reflector, but with a performance drop of 20-30%. 
I will take beamshots of a dedomed P60 host (Xeno F8V5) and a Trustfire X7 dedomed xm-l mod. 
I will include some very popular flashlights and another interesting mod, a Armytek Predator with a XT-E R5(from cutter) led.
I have another dedomed xm-l led(other than the first two mentioned), it is currently in a cheap trustfire 40mm host(of $12), i will include that too, just to show that in a very cheap setup you can get crazy lux numbers.


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## saabluster (May 15, 2012)

easilyled said:


> To be pedantic, I'd say that it drastically increases _throw_ rather than performance.
> Since the total output is actually decreased after dedoming, I don't think its correct to use the word performance.



"Increased performance" is a perfectly acceptable term to use to describe the effect of removing the dome. Well perfectly acceptable given it is said in context. Context which I did not provide so I am glad you mention it lest we get people thinking dedoming creates more lumens.  Thanks


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## saabluster (May 15, 2012)

Walterk said:


> Yes we know, well I know from beamshots and experiences shared on CPF.
> 
> Talking only about the witnessed drop in lumen, please be clear on where it comes from:
> 
> ...


The same lumens are not emitted.

The dome does two things that improve light extraction. It provides a more gentle transition in index of refraction which reduces reflection losses. They actually use silicones of varying indices going from higher index materials close to the die to lower index silicone as you move out away from the LED die. The LED die has a very high index of refraction and without this gentle transition more light would stay inside.

The other thing the dome does is move the escape surfaces farther away where the angle the light can escape the package is more perpendicular. Light transmission through materials of differing indices happens most efficiently with the light at a 90% angle to the refractive surface. The more you diverge from that the more that will be reflected internally. LED manufacturers could actually improve the performance(lumens) of their current LEDs by doing nothing more than making the dome larger. They of course also have other things like cost to factor into the equation.


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## bshanahan14rulz (May 15, 2012)

SaabLuster, could you tell if the phosphor was suspended in silicone too, or if it might have been a different material? Perhaps a solvent or digester ought to be researched. The Nichia (not a cree, but I don't think I've seen this type of info on a cree DS) datasheet I have actually tells what the different parts' substrate materials are, generically, i.e. dome is silicone (doesn't say what it's doped with, or if it even HAS any additives), phosphor layer is phosphor suspended in silicone.


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## Walterk (May 15, 2012)

ergotelis said:


> In general, a dedomed led has almost double the hotspot lux in the same reflector, but with a performance drop of 20-30%.


Don't be sorry, its nice you show your experiences. When you take beamshots, could you make a white-wall beamshot with a dedomed led without reflector/lens, so we can see how the light distribution has changed?!



saabluster said:


> The same lumens are not emitted.


Thanks for the clear write up, I expected almost same lumen.


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## ergotelis (May 15, 2012)

Walterk said:


> Don't be sorry, its nice you show your experiences. When you take beamshots, could you make a white-wall beamshot with a dedomed led without reflector/lens, so we can see how the light distribution has changed?!
> 
> 
> Thanks for the clear write up, I expected almost same lumen.



I had promised to do the beamshots but i didn't , i am planning to go out tomorrow for this. 
If i understood well, you need two beamshots, from a dedomed xm-l led and a normal xm-l , facing a white wall to see the difference?From what angle?
I clearly measured 20-30% lumen drop output. I think that, as current increases, the difference gets higher. It is logical up to one point, i believe that the energy from the lost lumens is converted into heat, so we get higher temperatures on the core and a another performance drop. I am waiting for saablaster to confirm this statement.


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## psychbeat (May 15, 2012)

Im curious if dedoming helps as much in say a p60/D26 sized reflector as much
as it does with an Aspheric. Maybe Vinh or Dave would start offering this as an option?

thanks for posting your results!!


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## Dioni (May 16, 2012)

I'm very curious to see the results in the beamshots !


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## Walterk (May 16, 2012)

ergotelis said:


> two beamshots, from a dedomed xm-l led and a normal xm-l , facing a white wall to see the difference?From what angle?



What I want to see, is how the light comes out from a dedomed led. How it flares away from the die.
Maybe half the beamangle, cut in half by a piece of paper or along the wall ? Something like this but then without optics:







With reflector shows what dedoming the led does for you.
I wonder what I can make from the dedomed. Half the beam indicates how the light and intensity is distributed, so we can find ourselves optics to match the led-characterisitcs.
Thats why I like to see the bare led without optics.

Der Wichtel posted some comparising beamshots in his post Another-dedoming-experiment sometime ago, but they are not that clear. 
The picture above is from the most useful open dir archives from Newbie.


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## saabluster (May 16, 2012)

bshanahan14rulz said:


> SaabLuster, could you tell if the phosphor was suspended in silicone too, or if it might have been a different material? Perhaps a solvent or digester ought to be researched. The Nichia (not a cree, but I don't think I've seen this type of info on a cree DS) datasheet I have actually tells what the different parts' substrate materials are, generically, i.e. dome is silicone (doesn't say what it's doped with, or if it even HAS any additives), phosphor layer is phosphor suspended in silicone.



Yes Cree uses silicone as a binder for the phosphor. This means that any attempts to dissolve the dome away also dissolve the phosphor layer. 



ergotelis said:


> I had promised to do the beamshots but i didn't , i am planning to go out tomorrow for this.
> If i understood well, you need two beamshots, from a dedomed xm-l led and a normal xm-l , facing a white wall to see the difference?From what angle?
> I clearly measured 20-30% lumen drop output. I think that, as current increases, the difference gets higher. It is logical up to one point, i believe that the energy from the lost lumens is converted into heat, so we get higher temperatures on the core and a another performance drop. I am waiting for saablaster to confirm this statement.


It does increase heat but it hasn't affected the maximum drive levels as much as I had anticipated. 



psychbeat said:


> Im curious if dedoming helps as much in say a p60/D26 sized reflector as much
> as it does with an Aspheric. Maybe Vinh or Dave would start offering this as an option?
> 
> thanks for posting your results!!


Yes it makes a big difference with reflectors as well. I am about to begin offering just this. Hang tight


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## psychbeat (May 16, 2012)

saabluster said:


> Yes it makes a big difference with reflectors as well. I am about to begin offering just this. Hang tight



Keep us posted!


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## mvyrmnd (Aug 20, 2012)

I realise this thread is quite old, but I'm about to replace the emitter in a light, and decided to de-dome the old one for giggles.

I was very, very careful, and picked apart the dome with a very, very sharp knife and a pair of tweezers. The last part of the dome broke off, and still remains covering the bond wires, and I'm not game to try and get it off, so there's a minor artifact in the beam because of it, but I'd call it a 99% success. I sliced straight through the top of the dome, leaving about 1mm of (now flat) silicon covering the die. Then I used the knife to lift the silicon on 3 sides (I didn't want to break the bond wires) then picked it off with the tweezers. It came off in one chunk, minus the bit still covering the wires.

Some pics 












I have no means of measuring the output or lux increase or whatnot, but the spot is now half the size it used to be on my office wall, and it hurts even more to look at. 

I'm pretty sure this scraggy Ultrafire HD2010 will now keep up with some of the big boys for lux, if nor sheer output.


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