Where is angle of light output measured from?

[Codiak]

For luminus SST-90 where does the 120 degree output measurement get measured from? The bottom of the dome? The Top? Somewhere in between?

 

[Benson]

None of the above, really. It's about the actual angle the light is traveling, which is independent of where it left the LED..

Since light is emitted from different portions of the LED, and falls on different portions of whatever sensor is used, the only way to even make such a measurement is to get far enough away that the angle between any point on the sensor and any point on the LED is essentially the same. Considering that the LED is <10mm, and the sensor is probably about the same, you can get resolution of 1 degree with a distance of about 1m.

If you need to do near-field analysis, you're going to need more than the emission angle, or even the lux/theta plots in the datasheet.

 

[yellow]

I would think that it comes from the zero degree and the half beam angles going from there.
So, a "V" shaped, with the middle as starting point.

 

[Codiak]

I would think that it comes from the zero degree and the half beam angles going from there.
So, a "V" shaped, with the middle as starting point.

This was my orginal thought as well and is for my project the worst case scenerio.

I need to recess the entire LED while minimizing the diameter of the the hole. The higher in the dome we start the V the narrower the diameter.

http://picasaweb.google.com/BeaverLakeNe/CPF#5441126485007750978


The dome is a limiting factor here though I don't care to attempt removing it.
Where is the standard published wrt how the degrees are measured?
Why a freaking dome and not just a flat protective coating?

I'm just looking for as wide an output as possible without introducing corrective optics or reflectors.

 

[Codiak]

None of the above, really. It's about the actual angle the light is traveling, which is independent of where it left the LED..

Since light is emitted from different portions of the LED, and falls on different portions of whatever sensor is used, the only way to even make such a measurement is to get far enough away that the angle between any point on the sensor and any point on the LED is essentially the same. Considering that the LED is <10mm, and the sensor is probably about the same, you can get resolution of 1 degree with a distance of about 1m.

If you need to do near-field analysis, you're going to need more than the emission angle, or even the lux/theta plots in the datasheet.

I should have just asked the real question which is what is required diameter of a recessed hole, assumming a star mount, that will maximize the width of output without optics or reflectors?

 

[TorchBoy]

Codiak, where did you get the 120° figure from? In this post jtr1962 has a graph indicating it's bang on 100°. The graph in the datasheet indicates around 110°.

 

[Codiak]

Codiak, where did you get the 120° figure from? In this post jtr1962 has a graph indicating it's bang on 100°. The graph in the datasheet indicates around 110°.

I forget where the original 120degree number came from, though when I checked the Radiation Pattern from the spec -60 to 60 degrees seemed reasonable loss given 180 degree isn't possible in my application.

 

[spencer]

Well the smallest you can make the hole is the diameter of the dome. Placed close enough to the die it would be as if the hole wasn't even there.