Possible reason for the P1D CE beam ring?

[Nereus]

There have been a lot of discussion about the Fenix P1D CE beam in the CPF. Many of us see a ring around the hotspot. Please have a look on the Cree XR-E datasheet: http://www.cree.com/products/pdf/XLamp7090XR-E.pdf , especially the page 5 "typical spatial radiation pattern". There are small but visible peaks on both tails of the light distribution, some 85 degrees off-axis. These peaks are small compared to 0 degrees peak lux but very large compared to the close proximity brightness around 85 degrees off-axis. When going from 75 deg to 85 deg the increase in the (relative) intensity is more than 100%. And since this small peak is so much off-axis it hits certainly the reflector. And since the smooth reflector seems to (in my opinion) be close to parabola the "minor-peak" (is this a proper english word?) light will be projected almost parallel to axis. As a result, in white wall beamshots this portion of light ends up in the close proximity of the hotspot.

After this reasoning I have a question open to CPF discussion: could the P1D CE beam ring be a reflection of this off-axis peak?

-N

 

[PANZERWOLF]

After this reasoning I have a question open to CPF discussion: could the P1D CE beam ring be a reflection of this off-axis peak?

this should be easy to answer if you have a bare cree lying around (which i don't)
because the lighter ring in the reflector beamshots has a yellow tint
if you see a tint like that at 85° off the bare emitter, that should be the source

 

[Moat]

There is a definite luminous dip in the curve, as seen here in Pinter's post (thru an IMS 17mm reflector). Some spectral (tint) separation appears to be going on as well.

Then, if you look here at Newbie's post - specifically the first and second set of "three views" (lowest angles, on the LH side) of the second photo - showing a lightly-driven XR-E at different angles - one can imagine the "dark ring" being caused by either the "dark blob" visible in the XR-E's dome in the first two "angles" of the first set, or (more likely) the luminous loss that appears to occur as the viewing angle transitions between the dome's refracted output (first and second set), and the direct view/output of the die itself (second to third set, and beyond).

It would be interesting to know the specific angles of Newbie's photos, to compare to those you noticed in the Cree specs.

I also suspect the tint shifting is a result of the prismatic spectral separation happening within the glass dome, at the refracted angles seen in the first two "sets-of-three".

I'd think a narrow band of sputter/orange peel, only applied way down deep in the reflector (where the reflector "sees" these above anomalities), would cure the "dark ring"... and allow the remaining reflector surface to be smooth/efficient.

That's my guess, anyways... :thinking:

 

[Nereus]

Thanks, guys, for your comments! Unfortunately I'm still waiting for my P1D CE and CREE XREs to arrive so right now I can't carry out any real life tests. I got my idea of the source of the ring by simply looking the white wall beamshots here in CPF and the XRE datasheet. But you have good ideas how to test my theory! Especially I like the suggestion to sputter only the deepest part of the reflector because that maintains maximum throw but still fixes the problem (_if_ my theory holds...). The only problem is the fact that I should buy an extra P1D-CE so that I could manipulate its reflector. That's a 70 USD experiment! I may end up ruining one P1D-CE and still have no idea where the ring comes from...

-N

 

[LowBat]

I'd think a narrow band of sputter/orange peel, only applied way down deep in the reflector (where the reflector "sees" these above anomalities), would cure the "dark ring"... and allow the remaining reflector surface to be smooth/efficient.

That's my guess, anyways... :thinking:

Like the Streamlight Tasklight 2L reflector.

 

[NewBie]

The rough bumpy reflector coatings also fix the same ring issue with the Seoul P4, and also help it out with it's tinty beam problem.

 

[Nereus]

There is a general feeling here in CPF that there is a trade-off between the beam quality and throw of P1D-CE. But guys, have a look on this thread https://www.candlepowerforums.com/threads/146540 , especially the A19 XRE compared to P1D-CE figures... Isn't it strange that a textured reflector provides _better_ trow than a smooth reflector? Of course the drive currents might be different, emitters might be different bin etc...

Could someone take a P1d-ce reflector and compare its peak lux to Mcr19R reflector using the _same_emitter (should I have P1D-CE and XREs I would do this by myself)? We may be surprised by the results.

-N