LuxIII Lamber. Spatial Radiation Patt & Reflectors

Hi everyone,

I'm getting into reflectors these days and was studying lumiled's
Spacial Radiation Pattern for the Luxeon III Lambertain.
http://lumileds.com/pdfs/protected/DS46.PDF
And I was wondering if any math or reflector guru's can help me here.

I'm trying to calculate from this graph approximately at what
angular displacment to 0 degrees does 50% of total light output
gets emitted.

Assuming that relative intensity is linear, I guess it would be
a adding up the area under the curve - the area within the angular
displacement and the area outside of the displacement being the same
would yield the correct angle.

From eyeballing the graph. It looks like lower bound would be
about 30 degrees displaced and the upper bound would come to about
37 degress.

I'm a little rusting on my trig, but this would mean that if
you want a reflector to reflect 1/2 the light, and the other 1/2
would pass through without touching the reflector, you would need
the open end of the reflector to be about 60-74 degrees. What would
the ratio of the height of the reflector (from emitter to open end) and the diameter of the open end be?

Say a reflector is getting 50% of the light. The light that leaves
a reflector (theoretically) is parallel. But the light that never
touches a reflector leaves the light in a conical way - therefore
will not travel as far and intensity will be about 1/4 intensity
per 2x distance. So the depth of a reflector will determine
how much light is thrown.

Another thought, it doesn't make sense to make a shallow reflector
because according to spacial radiation pattern graph, the intensity
drops drastically at great angles. So a good throwing reflector
needs not only a wide open end, but also need to be deep.

Upon pondering these details, the "size" of the reflector is not
as simple as the diameter of the business end of a light. Also,
the ratio of the reflector height and opening diameter is a factor.

Anyway, I'm rambling a bit here.... can someone add to this or
put some real numbers and formulas here /ubbthreads/images/graemlins/smile.gif

david

Re: LuxIII Lamber. Spatial Radiation Patt & Reflec

This is a bit easier on the eyes than DS46.

Ugh.

In order to conveniently find the half area, you would need a real function to integrate (or at least use a brute-force Rieman sum).

It's been a long time since I've touched any calculus, and neither radiation pattern doesn't look like a nice'n'neat polynomial - especially since they're adapted from the traditional radial chart.

Re: LuxIII Lamber. Spatial Radiation Patt & Reflec

As you dig futher into reflector design, you'll also learn about the importantance of the source size.

There is some interesting items here:
http://www.radimg.com/products_radiantsources.htm

TracePro is also useful:
http://www.lambdares.com/

Re: LuxIII Lamber. Spatial Radiation Patt & Reflec

[ QUOTE ]
NewBie said:
As you dig futher into reflector design, you'll also learn about the importantance of the source size.

There is some interesting items here:
http://www.radimg.com/products_radiantsources.htm

TracePro is also useful:
http://www.lambdares.com/


[/ QUOTE ]

wow nice links.

I do know the smaller the size, the more effective the reflector
becomes. Ideally, it's a point. But we know thats impossible because
a point is infinitely small.

Isn't this why LuxV's cannot throw as far as LuxIII's? Because
their die is so big? I wonder if cree's xl7090 die is smaller than
the lux3

/ubbthreads/images/graemlins/confused.gif

Re: LuxIII Lamber. Spatial Radiation Patt & Reflec

Here are some measurements I made on various reflectors and
the diameter of their hotspots at 3ft:

o17xa 8in
so20xa 6in
so27xa 3.5in
mag 27mm 3in
arc4 6in