Hi Jo Ling,
The Help documentation for Source Rectangle references Source Ellipse for defining the angular distribution. Three methods are offered: 1) rays appear to emit from a point , 2) a Cosine^n distribution, 3) a distribution which is Gaussian in the x and y direction cosines which are l and m. If you follow the directions given, any of these distributions will produce rays which are not collimated.
I often use a Gaussian distribution. From the given formula, I = I0 Exp[-(Gx l^2+Gy m^2)] it is possible to show that if Gx = Gy = G then the distribution is radially symmetric and that if G = 2 / Sin(theta)^2 then the intensity falls to 1/E^2 at an angle theta from the z axis. Further, the distribution is approximately Gaussian in theta for small angles.
Kind regards,
David
Hi David.
Thank you for this; I will try the Gaussian distribution for my analysis.
Best Regards
Jo