Illumination design usually requires the shaping of a specific irradiance distribution from a given light source. For point-like sources or collimated laser beams various methods exist to construct the shape of the refractive and/or reflective surfaces within the optical system. However, for extended sources, an additional feedback or optimization loop is usually required and limitations are not clear. We propose an analysis and design method that includes the source extension from the very beginning. The method is based on phase space mapping of the source radiance distribution onto the target irradiance distribution. We illustrate the method with several examples.
In the last few years the requirement of more special and complex optical system increases as the demand in industries for higher eﬃciency increases. To satisfy the demand more complex optical elements substitute continuously standard components. Therefore it is of high interest to develop new methods in evaluating optical systems. In classical illumination design a huge number of rays has to be traced to get enough information to evaluate the performance of the system. An other method is to investigate the transport of etendue in the phase space picture where we have direct access to the radiance, irradiance and radiant intensity without extensive ray tracing. The phase space analyzer oﬀers a diﬀerent way to illustrate directly the phase space diagram of an arbitrary light distribution restricted to two dimensions. This method is much faster than traditional ray tracing. Most often used illumination components like integrator rods and optical arrays can be understood in the phase space approach.
In the last years the requirement of special illumination optics increased in the course of developing specific optical systems for wide range of applications in industries and science. Standard components become continuously substituted by more complex freeform surfaces with higher efficiency. Therefore, other methods in evaluating optical systems are of special interest. In illumination design the classic way to check the performance of a system is to trace a huge number of rays through the system and analyze the radiance and irradiance distribution on the target surface. Another access to the most important illumination quantities like radiance is to look at the transformation of etendue in phase space. This offers a new perspective for the optical designer onto illumination systems. Another interesting aspect is the analysis of aberrations also for freeform elements where standard aberration theory for rotational symmetric systems fail.
For imaging design aberration theory provides solid ground for the layout and development of optical systems. Together
with general design rules it will guide the optical engineer towards a valid starting point for his system. Illumination
design is quite different: Often first system layouts are based on experience, rather than on a systematic approach. In
addition radiometric nomenclature and definitions can be quite confusing, due to the variety of radiant performance
definitions. Also at a later stage in the design, the performance evaluation usually requires extensive statistical raytracing,
in order to confirm the specified energetic quantities. In general it would therefore be helpful for illumination
designers, especially beginners, to have an engineering tool, which allows a fast, systematic and illustrative access to
illumination design problems. We show that phase space methods can provide such a tool and moreover allow a
consistent approach to radiometry. Simple illustrative methods can be used to layout and understand even complex
illumination components like integrator rods and optical arrays.