"Virtual" de-doming for aspheric lights?

I was playing around with a dead XM-L ((power supply too long to to switch to constant current, and I had my voltage up to compensate for lead loss, but up a bit too high...) Dropping it in pool of rubbing alcohol makes the dome appear to vanish (refractive index of the dome and IPA are close), and sticking some calipers into the pool to get a rough measure of the die, it comes out to ~2.25mm which is the actual die size of the XM-L iirc. Out of the IPA the die is ~3.2mm across. If you were to put some sort of cylinder on the board, fill it with norland, and drop a slide cover(think microscopes) or even better an AR-coated window (http://www.edmundoptics.com/onlinecatalog/displayproduct.cfm?productID=1919) and cure the whole assembly, would it be practically the same as de-doming?


Would you still keep the boost in extraction effiency that the dome gives you? (Thats from having something with a close/matching refractive index on the surface of the die, correct?) I would fiddle with it some now that I have my lux meter, in, but I have a nasty calse of polyprojectitis lately, and like I said, it was a non-functioning LED anyway

I know norland for covering a bare die doesnt work out, as it yellows from the heat, but now with the silicone insulating the die from the norland, it could possibly survive better?

Re: "Virtual" de-doming for apsheric lights?

i doubt it, i once touched the dome of working xm-l, by accedent, with microfiber cloth, hot dome burned hole in cloth in less than a second. it still gets hot.

Re: "Virtual" de-doming for apsheric lights?

CKOD said:

I was playing around with a dead XM-L ((power supply too long to to switch to constant current, and I had my voltage up to compensate for lead loss, but up a bit too high...) Dropping it in pool of rubbing alcohol makes the dome vanish, and sticking some calipers into the pool to get a rough measure of the die, it comes out to ~2.25mm which is the actual die size of the XM-L iirc. Out of the IPA the die is ~3.2mm across. If you were to put some sort of cylinder on the board, fill it with norland, and drop a slide cover(think microscopes) or even better an AR-coated window (http://www.edmundoptics.com/onlinecatalog/displayproduct.cfm?productID=1919) and cure the whole assembly, would it be practically the same as de-doming?


Would you still keep the boost in extraction effiency that the dome gives you? (Thats from having something with a close/matching refractive index on the surface of the die, correct?) I would fiddle with it some now that I have my lux meter, in, but I have a nasty calse of polyprojectitis lately, and like I said, it was a non-functioning LED anyway

I know norland for covering a bare die doesnt work out, as it yellows from the heat, but now with the silicone insulating the die from the norland, it could possibly survive better?

Click to expand...

The norland may work for you with the dome there to give some distance. Mind you I still would not put that in a salable product but it should be fine just for experimenting. The extraction efficiency will never be the same without the dome however. That is not to say that you will not see an improvement in performance with an aspheric as you can simultaneously decrease extraction efficiency and improve throw.

Re: "Virtual" de-doming for apsheric lights?

1-The extraction efficency, isn't it right that the Led with dome has a 'apparent' bigger die with certain Lux/surface brightness but not Lumen/flux extraction? So would affect beamwidth mainly?

2-I think your idea of giving a window instead of a dome should work. Although the dome from the manufacturer will be pretty smart engineered and so not bad for flux. Home-brew will have little less efficiency.

3-What do you think the alcohol did with the phosphor layer and all? Any visible consequences?

4-Instead of a window, you could attach (with Norland or equivalent) glass-fibre to the die.
In this way, splitting the heat/actual die from the point of emitting light at the end of the glassfibre, make it a lot easier to mount the Led base to a fanned heatsink.
A bundle of this kind of assembly would give a huge die with enormous Lumen and still the high intensity of the XM-L.
And directing all the fibres on a single point would make the surface brightness of each fibre add-up!
That way 15 Led's would approach short arc Xenon closely.
Can you picture it? Close to this:

Re: "Virtual" de-doming for apsheric lights?

I edited the first post to clarify, the IPA didnt dissolve the dome, but just made it dissappear optically since the refractive index of the alcohol and silicone are similar. I'm not talking about chemically de-doming, but rather, filling in around the dome with something of similar refractive index (NOA in this case, or optical silicone if anyone can get their hands on it...) and capping it off with a window.

I guess it all depends on the phyisics of the extraction effiency boost netted by the dome, and the mechanisms of that, no reason it couldnt work optically.

Re: "Virtual" de-doming for apsheric lights?

Ok sorry for the misunderstanding. Liked the concept of chemical de-doming.
For durability building upon the exisiting dome would be a safe mod.

Re: "Virtual" de-doming for apsheric lights?

alpg88 said:

i doubt it, i once touched the dome of working xm-l, by accedent, with microfiber cloth, hot dome burned hole in cloth in less than a second. it still gets hot.

Click to expand...

Is that not the concentration of energy in the emitted light, rather than a hot dome?

Compared to earlier larger-domed LEDs, I think having the possibility of getting so much closer to the die just allows a much greater concentration of energy in a given area of material (or skin, if you happen to put your finger on the dome of even an XP-G/XM-L at full power.

Re: "Virtual" de-doming for apsheric lights?

uk_caver said:

Is that not the concentration of energy in the emitted light, rather than a hot dome?

.

Click to expand...

i seriosly doubt, i'm pretty sure dome just got hot, cuz i had to scrape off melted cloth from the dome, good thing it is hard, not like p7 soft dome. i didn't try finger thou, after seeing what it did to the cloth, i don't feel like it.

Re: "Virtual" de-doming for apsheric lights?

the test would be to immediateley put the cloth on as soon at the light turns off