New Type of Luxeon III

I've photographed Royal Philips LumiLEDs Luxeon III devices, many times in the past.

I recently had some issues with anomalies in my photos that I was trying to take of the newer Luxeon III and thought it was my setup/camera, etc...

I was seeing weird effects like this:



You see where the tint changes from the center to the edges?

So I started scratching my head, trying to figure out what was going on.


Another weird thing in a shot:




It almost looks like a clump of phosphor was piled up on top of the die.

Imaging of the die on the wall with a lens wasn't working nearly as well as it used to.


So, I kept taking photos of the latest Luxeons I got, doing different things and kept getting the same results. So, I went and grabbed one of my lower output TWOH LEDs from 2003, and everything looked like it was "supposed" to, and as I remembered it in my photos.

So, I decided to try another tactic, and light the device externally, and found:





You will notice a lump of stuff on top of the die that is a slightly different color, above the phosphor!

I'm not certain as to what this is, but I suspect it is a higher index of refraction material, that is put above the die/phosphor in order to help extract more light out of the die.

Unfortunately, these newer U bin Luxeons seem to have a little bit more tint shift in the beam profile.

Do you think it's an intermediate material that blocks UV light from reaching the epoxy?

No, they do not use epoxy. It is an acrylic dome filled with silicone gel. There is no UV in the blue die output anyhow. I do know they have been working on different index of refraction materials to extract more light out of the die.

At least it explains the extra tint shift of the beam profile in the new Luxeons.


More photos:

Well you have to admit, it was a good guess from a hack like me!

LOL Silicone-filled. I was wondering why I enjoyed touching them!

Man! That's a good camera!
Good pics.
So that's one of the reasons why there are more U*** binned Luxeon3 leds out there now. :thinking:

Extra stuff in the middle instead of at the outer edges.
This is quite different from the older Luxeon1 leds and many other leds made.

3rd_shift said:

Man! That's a good camera!
Good pics.
So that's one of the reasons why there are more U*** binned Luxeon3 leds out there now. :thinking:

Extra stuff in the middle instead of at the outer edges.
This is quite different from the older Luxeon1 leds and many other leds made.

Click to expand...

Most of my Luxeon III LEDs don't have this, just the Luxeon III ones I very recently ordered.

There are more U bins, but they don't seem to have become common yet, unfortunately. They probably just moved up into somewhere within the upper T bin range.

I don't know what to do about the tint shift within the beam profile issues for the white wall police, short using bumpy reflectors like Don has done for some time now. The nice thing about those, is they hide mis-alignment, nicks, and other defects very well.

Thanks on the camera comments, those are just nothing more than macro mode on the low cost Canon S3 IS.

Hint.

Google
index of refraction
LED
silicone
gel

Is it a filter?
Yaesumofo

Those are beautiful photos Jar! If that inner material is a different index of refraction, and like you I suspect it is, it should also have the affect of changing the angular distribution pattern of the output given its lens shape.

If you're talking about the hazy dome above the phosphor, that has always been there.

4 year old Lux I emitter:


3 year old Lux I star:


2 year old Lux III star:


Lux V emitter:

NewBie said:

Hint.

Google
index of refraction
LED
silicone
gel

Click to expand...

I googled these terms. I come up with some stuff about a vacuum, Robert Plant, breast augmentation, and hair care. I feel that I am on the wrong path.

Evan's right. I'm holding up an RY0J sandwich I bought from the Shoppe last year. It's the only high dome I have sitting out right now. It's not easy, but you can see the "hazy dome" above the die with the naked eye. You need to catch it at the proper angle, and light the thing up from an external source (as you noted).

Are we sure that isn't just some refraction/reflection or something? I know you get weird effects when you start staring into fluid filled glass containers (think fishtank). Maybe we're just seeing the inside top of the outer dome itself?

Thank god everyone that googles crap doesn't brag about it.

EngrPaul,

Dig a little deeper, page 31 (also search for index within this one found on Google)
http://www.oti.globalwatchonline.com/online_pdfs/36581MR.pdf

Some LED application specific information:
http://www.nusil.com/literature/tr/Improving Light Extraction from LEDs.pdf


Odd Evan, I've got several old ones around here, where I do not see that.

Any idea why I'm also seeing tint variation across the die surface now?

They used to be uniform, or have a tiny "orbital".

Example:

Is it an air bubble between the die and silicone gel?

Greg

I have a collection of luxeon emitters and many of them have these envelopes (my word for the litle chemical bubble or what ever it is..
I was not able to see the effect on any of my lux V emitters. (3 or 4 of them)
Yaesumofo

My new R binned LOP SE has this inner dome? Never looked before but its there if you look carefully. When on and watching from the side with sunnies! the light does seem to refract somewhat off the inner dome but not understanding the optics side of things I dont clearly see what effects (good or bad) this has? This is why I need you super tech dudes to expalin it for me

Well, I found some old Stars, and I found them on those, but they don't seem to be as obvious or as high?

I wonder if they are just using a higher index of refraction material now.

I also found a new UX1J that it is pretty clear on, that a cpf'er had sent me.


I don't spend as much time looking at the white LEDs, since I do a lot more with RGB.

Very interesting.


Concept-
The high index of refraction materials better match the index of refraction for the LED die, which allows for more of the light to escape out of the die. Lenses basically work because of their higher refraction of index, as compared to air. This allows us to bend the light, to do things, like form a magnifying lens. However, if you take a regular piece of glass, and reflect the sunlight off of it, it is still pretty bright. However, if you put a coating on the glass, like some higher end flashlight makers do, known as AR coating (anti-reflective), that coating helps to match the index of the glass to the air. Thus you get a reflection that is 0.2-0.5% off of each surface, instead of 4-5% off of each surface.

I've been digging out old Luxeons I have around the house and checking them out, and there is a bit of variation in the internal body, however, in the same batch, they look very similar: