source 1 is collimated with a divergence u03b4 the smaller the diameter the smaller is the divergence u03b4 however the smaller the diameter the smaller is the source flux u03c6 of the light source of a given brightness therefore a trade off has to be made with respect to the desired intensity and resolution of the specific luminous intensity distribution for efficient light throughput the light source 1 advantageously should fulfill the following characteristics the source flux u03c6 of the light source 1 is compatible with the total intensity i d of the specified luminous intensity distribution the source size h is compatible with the angular resolution u03b4 of the specified luminous intensity distribution see fig5 b the source divergence u03b1 is compatible with the collimating optic size diameter d of the collimated beam and focal length f of a collimation lens the precise formulation of these requirements depends on the type of source used at the focal point of the collimating optics two exemplary simple cases are illustrated hereafter a uniform circular light source surface emitting uniformly in a light cone with apex angle 2 u03b1 multi mode fiber output for example where u03c6 is the source flux u03b7 c the source collection efficiency ratio of source flux emitted by the light sources and output flux of the luminaire assumed that there are no losses in the.