# Calculating Flux for non-lambertian emitter

1. Apr 21, 2013

### chrisewolf

Hey everyone!

I am struggling with the following problem:
I am calculating the ratio of photons emitted to electrons generated in an LED. Due to the architecture the device shows a strong cavity effect and as such the emission profile is not lambertian but very "flat".
Unfortunately I can not use an integrating sphere with my apparatus. So I tried to measure the luminance (cd/m^2) for angles from the surface normal down to 80°. Indeed this measurements show a strong deviation from the lambertian cosine law.

Now I need to calculate the luminous flux (for an lambertian this is [itex]\Phi=\pi L[\latex]) but I am not sure how to properly do so for my case (though this seems like very basic optics).

The main confusion stems from the inclusion of the solid angle. I do not know how to properly discretize the solid angle element to somehow "sum up" over the half sphere I effectively measure (that is the luminance shows no dependence on the azimuth).

I am very thankful for every tip!

Have a nice sunday!
Chris