Design Competition - Frequently Asked Questions

What is Nonimaging Optics?

Nonimaging optics is a field that focuses on the optimal transfer of light energy rather than forming images. Unlike traditional optics that aims to create clear images (like camera lenses, microscopes, or telescopes), nonimaging optics is concerned with efficiently collecting, concentrating, or distributing light energy. This is particularly relevant for applications like solar energy or illumination systems.

Below are some good introductory resources if you want to learn more:

• Nonimaging Optics: A Tutorial - An open-access article giving an overview of some fundamental methods and concepts
• Nonimaging Optics by Roland Winston, Juan C. Miñano, and Pablo Benítez - A classic reference covering the theoretical foundations
• Introduction to Nonimaging Optics by Julio Chaves - A comprehensive textbook on the field
• Illumination Engineering: Design with Nonimaging Optics by R. John Koshel - Focused on illumination applications
• Designing Illumination Optics by Julius A. Muschaweck, Henning Rehn - A practical guide to designing illumination systems, including principles of nonimaging optics

I come from another research field, can I still try?

We absolutely welcome this! As an outsider you might bring new ideas into the field. Maybe you even want to submit an abstract to the conference based on your outsider-approach to solving the competition challenge?

Feel free to email us if anything about the competition rules are unclear to you.

Should I use STEP files or STL files for my submission?

In most cases we recommend using STEP files if your design software supports it, as they are generally more accurate and smaller in file size. However, if you are really pushing the limits of your design, there are some considerations to keep in mind:

While STEP files can accurately represent curved surfaces, the surfaces will actually approximated by a mesh before they are raytraced in the submission portal. In most cases, the resolution of this approximation will be sufficient, but you do not have control over if you should find it insufficient for your specific case.

STL files represent surfaces directly as a mesh of triangles. This means that the submission portal will trace exactly the mesh that you upload, and you can choose to generate STL files with exactly the resolution you prefer. However, a higher resolution leads to larger file sizes, and we have a file size limit of 100MB.

What is ètendue, and what does it mean that it is matched?

Étendue can roughly be described as how “spread out” light is in both space and direction. The light entering the build volume in the XX-challenge is spread out over the one square meter of the entrance aperture, and over the solid angle representing the XX-shaped star. Ètendue is conserved in classical optical system, meaning that wherever the light ends up, the magnitude of this ètendue will be the same. If the light has been concentrated down to a smaller area, it means that the directions of the light have been spread out more, and vice versa.

When we say in the instructions the étendue is matched, it means that the input étendue of the light from the XX-shaped source (input area × XX-shaped solid angle) exactly equals the étendue of the target nonimaginum rod (rod surface area × a hemispherical solid angle). This means that all the light can barely “fit” onto the rod, and you need a perfectly designed concetrator to be able to concentrate all the light onto the rod. In Nonimaging Optics, ideal solutions have been found for some specific cases (the most well-known case being the Compound Parabolic Concentrator in 2D). However, achieving the same for a more general case like the XX Challenge is more challenging. As an additional complication, we have given the mirrors a reflectivity of 95%, which will incentivize you to look for designs that minimize the number of reflections.

See https://what-if.xkcd.com/145/ for another fun exploration of étendue conservation, and the references listed above for a more rigorous introduction.

What is the inspiration for this design competition?

The competition celebrates the 20th anniversary of the Nonimaging Optics conference, and draws strong inspiration from the traditional Lens Design Problem and Illumination Problem from the International Optical Design Conference. The XX-shaped source pattern is a nod to the Roman numeral XX (20), celebrating the 20th anniversary of the conference series being part of SPIE Optics + Photonics. The concentration aspect comes from how solar concentration is a classical use-case of nonimaging optics, while the XX-shaped angular distribution also plays to how illumination systems are often designed to exhibit specific angular distributions.

How is the efficiency calculated?

The efficiency is calculated by ray tracing in our submission portal. We generate rays following the XX-shaped angular distribution and uniform spatial distribution over the entrance aperture. The efficiency is the fraction of these rays that reach the nonimaginum rod, taking into account the 95% reflectivity of the mirrors.

Have another question?