Question about CREE XLamp 7090 emitters

Doug S

Flashlight Enthusiast
Joined
Jun 20, 2002
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2,712
Location
Chickamauga Georgia
I see on the datasheets for the CREE XLamp 7090 series that the viewing angle is listed as 100 degrees. This is pretty far from a true Lambertian pattern which would have a viewing angle of 120. If I had one in my hand, I could answer my own question but I have never seen one. For those who have, does it appear that the reduced [relative to true lambertian] angle is due to the die being recessed into a reflective cup or due to refraction in the dome?
As a related question, does anyone have a link to a document showing the angular intensity distribution for these. Unlike most LED datasheets it is not included on the 7090 datasheets.
TIA
 

McGizmo

Flashaholic
Joined
May 1, 2002
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17,290
Location
Maui
Doug,
Hard to tell what is happening with the white 7090 but with the UV 7090, you can see that the die is down in a cup and I would guess that this is the why of the reduced viewing angle. Since you wasted time on thermal stuff for me, here is back at you:

CreeViewingAngle.jpg
 

HarryN

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Jan 22, 2004
Messages
3,976
Location
Pleasanton (Bay Area), CA, USA
Hi Doug - It is good to see you posting again on CPF.

I cannot tell you the exact reason for the light angular distribution, but it is in fact very real. The dome is also similar in size to a 5mm vs the 5.6 we are used to with the Luxeon products. There is another difference, which in many ways is even more significant. At least to my eyes, it appears that the phosphor is coated on the inside of the dome, not on the LED die itself.

The end result of all of this, is that the light coming from the Cree package behaves more like a "soft white" light bulb, than the "clear" light bulb behavior of a Lux III. The angular distribution also is going to tend to not work well with many conventional optical systems (reflectors / optics) which were really optimized for the Lux III type package.

The really good news, is that in the simplist of reflectors, it makes a very nice smooth beam - mostly corona, unless the reflector is a bit deep. I use the Cree (and Luxeon) for some apps, esp. the UV version in my CR2 light, but I have a different optical setup for each one.

The Cree package, IMHO, is a very good one for flood light applications, especially if driven closer to the 350ma range.
 

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