ZEMAX Development Corporation thanks Radiant Imaging, Opsira and Lumileds for the experimental data used in this article. Luxeon is a trademark of Lumileds, Inc.




Accurate source modelling is the key to accurate illumination system modelling. ZEMAX can split, scatter, diffract, refract, reflect, etc a ray, but this article discusses how to launch a bundle of rays initially, so that they are an accurate representation of the source's spatial and angular flux distributions.

We will discuss modelling a Luxeon LED in this article, but the design approach can be used for any complex source: arc lamps, incandescent lights etc.

ZEMAX contains many source objects that can be used as initial approximations to a source's properties. For example the source_filament is a good first approximation to an incandescent lamp, the source_volume_cylinder is useful for modelling fluorescent tubes. The key to our approach in this article is to get as close as possible to experimental, measured data in both the spatial (near field) and angular (far-field) distributions.

As the LED we are modelling is specified in photometric units, we will use photometric units also in our simulation. Under System > General > Units set it as follows:



As a result, illuminance will be in units of Lux (Lumens.m^-2), luminous intensity will be in Candela (Lumens.steradian^-1) and radiance will be in Candela.m^-2.