Saabluster,
Nice work with encapsulating the XR-E emitters. I have been watching this in excitement to see what happens when a flashaholic has control over the emitter dome shape. BTW, how have these mods affected overall lumen output compared to before the mod? I personally lost domes off of two Rebel 0100 emitters and it seems like the phosphor was perfectly intact and the LED operational. The K2, and the Cree products still use bond wires that would be torn after removing the die. Hopefully, regardless of the emitter used, domes will not have to be removed in your experiments. Clean silicone domes of the XP-E, XP-G, and Rebel might disappear when you goop your silicone gel over top of it (so dome removal may be unnecessary).
So, I was just wondering why the encapsulated XR-E (dome removed) with the acrylic lens did better than the one without. Is it an issue with different indexes of refraction? Is it because the acrylic lens has a smoother surface?
You may have stumbled on something good for aspheric lens users, but I think before you should start selling these in large quantities, you should do more testing. I think that members would love to see comparisons between 3-4 new XR-E emitters from the same batch. Who knows, maybe your modded emitter without the lens degraded some, and if in better shape, could have perform the best. Having new emitters that perform the same from the start will help produce more conclusive tests in a more scientific fashion. (I understand the preliminary experiments with spare XR-Es). BTW, does the Deft use a high quality current regulator so even big changes in LED forward voltage will not affect output? I was just wondering.
Between the two modified XR-E emitters, I guess I do not understand why they are so different. Why not remove the ring and then re-encapsulate the emitter? Why not re-encapsulate a Rebel, XP-E or XP-G? I see that the consistency of the optical grade silicone gel causes your "dome" to sag before it cures, but why not let gravity aid you? I do not know its viscosity or its values for surface tension, but maybe when held upside down, a dome might form a geometric shape in your favor (parabolic, spherical, elliptical, or catenary). If you are going for flatness, then why not temporarily fix it to the center flat spot of an old brushless PC cooling fan and let centripetal forces level off the top of the dome some? If the viscosity is high enough and you make the fan spin slow enough, you may get a very flat surface. As you spin it faster it may begin forming a parabolic dip in the center (like what happens with those experimental spinning mercury mirrors). You have a lot of control over the shape of this dome; that is awesome.
If that acrylic lens is the ultimate solution, then why not take an old Cree XR-E metal ring (or a spacer with the same height) and fix it above a Rebel, XP-E, or even XP-G then fix on the acrylic lens? Maybe a modded XP-G would produce a projected beam (in the Deft) of the same size as an un-modded XR-E from your existing setup (I am being hopeful here).
I am just asking that you try different setups with other emitters. We all bow to you since you have the optical grade silicone gel and experience. I like the XR-E, but have always been doubtful to the metal ring from the optical standpoint (I understand the mechanical purposes). If you can make a new dome over the tiny Rebel, XP-E, and XP-G, you might be able to shape the dome to do the same thing that the glass dome on the XR-E did, or you may be able to shrink down the apparent die size (flatten the dome) without sacrificing the total lumen output.
I always found the tint shift interesting. I also worry that the tint shift, while being pleasant to the eyes, may be bad for efficiency or overall longevity. It seems like a major change happens when the tint shift occurs, and it could be a bad change. Does it mean that more blue light is internally reflected back to the phosphor coating to produce reds
(due to the change in index of refraction), or does it maybe affect how heat is removed from the top of the light which affects the efficiency of the phosphors?
Again, good job. Thanks for your patience with my numerous questions mixed in my post. Your experiment is intriguing, as many are afraid of working at the emitter level when doing modifications and experiments. If I had the tools and resources, I would have acted on my own emitter mods. For example. You could theoretically can cut rebel emitters down (the ceramic substrate) without affecting the etched traces to position the four dies tightly together so they almost touch (electrically, they could touch if you plan on wiring the dies in parallel). Just re-encapsulate them (or not if you cut cleanly) and this could equate into a quad TFFC die emitter. Its not a practical mod (with the MC-E, P7, and SST-50 out there), but I dream that it could be done.
Cheers,
-Tony