LXP-G-RS or LXP-RS for narrowest beam?

gav6280

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I think i may be getting my wires crossed a bit here?

The Ledli LXP-G-RS is quoted as as 5 deg but the LXP RS that was intally designed for XPE chips ( I think) is quoted as 3 deg.

So which one is going to give me a narrower beam using an XPG?

Or am i losing the plot and there is actually the same Optic?

Just looking for the tightest beam possible using an xpg without going down the aspheric route.

:thinking:.

So do i go LXP G RS(5deg) or LXP RS(3deg) but using an XPG?
 
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gav6280

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Nothing.....

But for me personally i just find them to fiddle and complex to deal with in a timely fashion and i have only very basic tooling.

So a very tight ready made optic solution is better for my particular situation.
 

znomit

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I think they are the same optic. For a while ledil were putting them both on the same datasheet... maybe they've updated since... I'm using CXP(same as LXP but square package) with an E and G on the pushbike. G is around 40% wider.
If you want tight throw from a small optic the XPE wins.

From the big XPG beamshot thread here.

CXP SQUARE REAL SPOT
FA10668_CXP-RS
±5.5°

Heres the comparison with an XP-E, ceiling shot at 2m.

Top: XPG WHT-L1-0000-00H51 R5 Bin
Bottom: XPEWHT-L1-WH0-R2-0-01 R2 Flux WH Tint

No surprises, around 50% wider and half as bright.
Note the more uniform colour of the G beam though.

CXPright1.jpg
 

jspeybro

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What is FWHM and what type of lens is this considered to be since it's not an aspheric?

Thanks. Just trying to learn!

FWHM= Full Width at Half Maximum. If you look at the intensity profile of a focussed high power led, you will get a central spot of which the intensity drops off when increasing the angle.
To be able to compare the spot for different leds and optics, one uses the FWHM value. This is the width in degrees at the half of the maximum intensity.
This picture will most likely explain it: http://en.wikipedia.org/wiki/File:FWHM.svg

For the lens type, these are TIR (Total Internal Reflection) lenses. a quick google search gave me this link which gives some explanation about it:
http://www.em.avnet.com/ctf_shared/sta/df2df2usa/LightSpeed-Eskow-0108.pdf
The advantage of these lenses is that they are made of plastic (PMMA usually) so they can be given about any shape.
Also, they are positionned right on top of the led so they will capture as much light as possible. The part where TIR happens can be seen as a reflector, the inner part can be seen as a lens, so this combines both. They usually have to be made for a specific led as all leds have different optical properties, although some can be used for multiple types of leds if you don't care too much about as specified performance.


Johan
 
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znomit

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Thanks Johan.

+1, good description.
Also note for FWHM some manufactures quote full angle and some +/-half ... so sometimes 5=10 :sigh:
Isn't that half width half maximum.... :thinking:

I always look for beam profiles in the datasheets.
 

jspeybro

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+1, good description.

I always look for beam profiles in the datasheets.

Yeah, manufacturers always seem to want to confuse customers with specifications... better have a look at the graphs to be sure what they mean.


as for the LXP lenses, I also think it's the same lens. It was probably designed for an XRE Led (FWHM=3°, however the graph seems to indicate 6° - http://www.ledil.fi/datasheets/DataSheet_LXP.pdf)
I guess they noticed that it also reasonably worked on the XPG (5° instead of 3°) and started selling them seperately.

Johan
 
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