Can the cree XRE's dome shape be changed/modified,/replaced?

I was thinking about milling, sanding, or somehow cutting down and then repolishing the top of an XRE's dome to widen the beam angle for more throw in reflectored lights.

In stock form, it only has a 70 degree light pattern compared to a Luxeon's 170 degree light pattern.
This won't work right in some reflectors in stock form.

Has anyone tried this yet?

Re: Can the cree XRE's dome shape be changed/modified?

I asked that same question a few weeks back here, and more recently here.

I'm still wondering if we can get a batwing style radiation pattern from one.

Re: Can the cree XRE's dome shape be changed/modified?

hmmmm.... :thinking:

Maybe someone will give it a shot as more of these hit the masses.
If anyone succeeds, please let us know how you did it.

Or better yet, maybe Cree will start making these with a wider angle.
It appears to be just the dome that determines the beam angle.

Although, I must admit that a pocket, or keychain light with the 70 degree angle would be very useful.

But I really want to put these little hotrods in reflectored flashlights that have a good beam.

Re: Can the cree XRE's dome shape be changed/modified?

If you change it, you will likely reduce the light extraction.

What this means to you- Less lumens output.

Re: Can the cree XRE's dome shape be changed/modified?

From what I understand, the domes are a thin Silica glass shell, filled with a silicone polymer "gel" - I doubt there's any way to reasonably re-shape it.

Re: Can the cree XRE's dome shape be changed/modified?

NewBie said:

If you change it, you will likely reduce the light extraction.

What this means to you- Less lumens output.

Click to expand...

How will slightly altering the profile of the half sphere shaped lens reduce it's total light transmittance?

Re: Can the cree XRE's dome shape be changed/modified?

Moat said:

From what I understand, the domes are a thin Silica glass shell, filled with a silicone polymer "gel" - I doubt there's any way to reasonably re-shape it.

Click to expand...

1idjack posted that here but 4 posts later in the same thread MillerMods contradicted that with this post-mortem report.

The lens is a glass hemisphere.

GanP posted 4 pictures of one here.

Re: Can the cree XRE's dome shape be changed/modified?

I too think it is glass. Otherwise it's a very hard synthetic but don't think so. Anyway it is much more scratch-resistant than Luxeon LEDs.

Re: Can the cree XRE's dome shape be changed/modified?

Don't mess with it. You'll screw it up--guaranteed.

Re: Can the cree XRE's dome shape be changed/modified?

Here is the reason. The die is far down in metal ring. You put a focusing lens and fill the cavity so it shoots the light out the top. If you modify the lens, so it no longer shoots the light out the top, then you have the light shooting inside the metal ring, and not going out the front.

The reason it's 70* is to shoot the light out the front and not have it bounce around inside the metal ring thing. By bending the light and making it go straight out, you get the most light coming OUT of the led.

Since the die is mounted basically on the ceramic, and not on a raised metal platform like the luxeon, it is required to focus the light straight up and out. Also frosting the dome would likely defeat it's focus and you'd run into the same problem.

It's a different creature, and not a new luxeon, so we gotta work with it's characteristics, instead of against them. One of the characteristics is that it produces a ton of lumens

Re: Can the cree XRE's dome shape be changed/modified/replaced?

LumenHound said:

1idjack posted that here but 4 posts later in the same thread MillerMods contradicted that with this post-mortem report.

The lens is a glass hemisphere.

GanP posted 4 pictures of one here.

Click to expand...

Interesting. :thinking:
The led still worked even after the glass hemispherical "lid" was removed?
I wonder if simply pulling it off and replacing it with a small, flat glass piece could work?
Something like a miniature, dome sized, high quality flashlight lense carefully stuck back on there for a couple extra lumens of light.

Edit:
That metal ring appears to be the big issue with doing that.
But still....
I would like to take a shot at that.
It appears that the light is still hitting the metal ring before reaching the bottom of the stock glass hemisphere.
I could be wrong though.

Edit again:
I just ordered 6 of them from nitroz to play with. :devil:

With regards to the half dome, it's just a simple converging lens, the light from the die strikes the bottom surface of the lens and is refracted upon entering the lens. The light is refracted a second time when it exits out the curved surface of the lens. Altering the shape of the lens is going to change that angle of second refraction.
Changing that second angle of refraction is going to change the overall radiation pattern of the package.

Re: Can the cree XRE's dome shape be changed/modified?

IsaacHayes said:

...Since the die is mounted basically on the ceramic, and not on a raised metal platform like the luxeon, it is required to focus the light straight up and out. Also frosting the dome would likely defeat it's focus and you'd run into the same problem.

It's a different creature, and not a new luxeon, so we gotta work with it's characteristics, instead of against them. One of the characteristics is that it produces a ton of lumens

Click to expand...

Very well said. For now, we need to go with the flow. It's very very efficient so we need to work with it, not against it.

:huh2: , CM, are you saying that changing the shape of the lens will hinder throw with regards to using a reflector?

lumenhound, he is saying that by messign with the dome, it will hinder the light that escapes (comes out of) the led. Mess with that and you get less lumens out of the led.

Please be specific.

What optical theory states "messing with the dome" is going to reduce the total light output of the device?

How, exactly, will altering the shape of the converging lens above the die cause the lens to have less total light transmittance?

It sounds as if your asking me to make a leap of faith based on a gut feeling.
I'm asking what scientific principles (other than Murphy's Law while modding) back up your gut feeling?

well try it and test it with an IS or home brew device. Before and after with bare led CC 350ma say and report back and prove us wrong! :nana:

What would happen if you remove the glass AND sand or file down the ring to expose more the die? If there is only air between the Die and the Sphere, why cant it work without it in a more radial pattern of light more suitable with current luxeon compatible reflectors?

I wish mine were here to give it a try and find out.

Anyone have pictures of the underside of a CREE emmiter? I am wondering if i could attach it to a solid copper round heatsink for better heat dissipation.

AlexGT

It is extremely simple LumenHound.

Uber basic stuff, kinda like we learned in middle school or kindegarden (it has been many decades so I forget which). Some children learn it long before this, by observing nature.

The light comming off the die hits the lens at an angle that is near perpendicular, thus you get maximum light extraction.

If you alter the shape the light extraction drops, due to the light hitting the lens exit surface at the wrong angle, and a portion or all of it gets reflected back in- all in the case of reaching the critical angle and having TIR take over. Anything that gets kicked back ends up with high absorption losses on the reflection, and will likely bounce around inside of the package many times before it makes it out- or is fully absorbed.

Now, you can take a OSRAM Golden Dragon or Platinum Dragon, and glue a half dome to it, and actually get 10-20% more light out of it.

Take the basic luxeon and then go look up the lumen output of the side-emitter, you'll see it looses just over 10% of its output. However, with the dimensions they have, and everything inside being highly reflective, they do not suffer much loss due to reflections, like in the batwing.

The exact position of the dome on the CREE XR-E, and the shape and focal point are specifically matched to maximize the light extraction. With the CREE, you really want to get the light out the first time. Take a look inside the package sometime especially a non-white one.

Think about the optics, like the NX-05, and how they work, to understand TIR a little. A laser and a fishtank works great, or even a fish tank/mirror/sunlight.

IsaacHayes said:

well try it and test it with an IS or home brew device. Before and after with bare led CC 350ma say and report back and prove us wrong! :nana:

Click to expand...

Please tell me what scientific theory you are using to convince yourself you are right?

I don't know that you are and I don't know that you aren't.

Again, what scientific principle are you basing your judgement on?

Where can I find more information on this scientific principle?

I'm open minded and would like to learn if you can provide some data.