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In illumination optics, color mixing is a key design task, but the realization can be a challenge. While tunable light sources based on multiple LEDs are commonplace, color homogenization is just as important for white LEDs, due to their spatial and angular color variation. In this tutorial, we first look at color mixing from an abstract, phase space-based viewpoint. From there, we derive a taxonomy of color mixing problems: How is the multi-color light source composed? What kind of homogeneity is required in the target? How is the homogenization influenced by source and target étendue? We categorize these problems and we present a toolbox: A selection of optical design elements, e.g. mixing rods and fly's eye arrays, and we show for each design pattern how it fits into the taxonomy. [ABSTRACT FROM AUTHOR]

Ray data files are a common way to model light sources, such as light emitting diodes (LEDs), in optical design software. Often, when an LED shall be placed at the focal point of a collimating lens, it is desirable to know the coordinates of just a single point, which is representative of the light source location, similar to the center of mass for a distribution of matter. In some communities, this point is known as the "virtual focus," and some LED vendors publish the virtual focus coordinates with their ray data sources. However, it is hard to find a clear and precise definition of the virtual focus, and it is not clear how it can be computed in an efficient way. We explain our definition and provide an efficient algorithm and its MATLAB® implementation. [ABSTRACT FROM AUTHOR]