Non-imaging optics

Non-imaging optics is the branch of optics concerned with the optimal transfer of light radiation between a source and a target. Unlike traditional imaging optics, the techniques involved do not attempt to form an image of the source; instead an optimized optical system for optical radiative transfer from a source to a target is desired.

The two design problems that non-imaging optics solves better than imaging optics are [http://oemagazine.com/fromTheMagazine/dec02/taminglight.html ] :
* "concentration": maximizing the amount of energy applied to the target. (as in solar power)("collecting radiation emitted by high-energy particle collisions using the fewest number of photomultiplier tubes" [http://hep.uchicago.edu/solar/design.html ] )
* "illumination": controlling the distribution of light, typically so it is "evenly" spread over some areas and completely blocked from other areas. (as in automotive headlamps, LCD backlights, etc.).

Typical variables to be optimized at the target include the total radiant flux, the angular distribution of optical radiation, and the spatial distribution of optical radiation. These variables on the target side of the optical system often must be optimized while simultaneously considering the collection efficiency of the optical system at the source.

Examples of non-imaging optical devices include optical light guides, non-imaging reflectors, non-imaging lenses or a combination of these devices. Common applications of non-imaging optics include many ares of illumination engineering (lighting). Examples of modern implementations of non-imaging optical designs include automotive headlamps, LCD backlights, illuminated instrument panel displays, fiber optic illumination devices, projection display systems, luminaires, the concentration of sunlight for solar power, and illumination by solar pipes.

Early academic research in non-imaging optical mathematics seeking closed form solutions was first published in textbook form by W.T. Welford and Roland Winston in their groundbreaking book, "The Optics of Nonimaging Concentrators: Light and Solar Energy", Academic Press, 1978. A modern textbook illustrating the depth and breadth of research and engineering in this area is "Nonimaging Optics" by Roland Winston, Juan C. Minano, Pablo Benitez, with contributions by Narkis Shatz and John C. Bortz, Academic Press, 2004. (ISBN 0-12-759751-4). A thorough introduction to this field can be found in the textbook "Introduction to Nonimaging Optics" by Julio Chaves, CRC Press, 2008 (ISBN-10: 1420054295 ISBN-13: 978-1420054293).

Imaging optics can concentrate sunlight to, at most, the same flux found at the surface of the sun.Non-imaging optics have been demonstrated to concentrate sunlight to 84,000 times the ambient intensity of sunlight, exceeding the flux found at the surface of the sun, and approaching the theoretical (2nd law of thermodynamics) limit of heating objects up to the temperature of the sun's surface [http://hep.uchicago.edu/solar/NIoptics.html ] [http://www.nature.com/nature/journal/v339/n6221/abs/339198a0.html ] .

The simplest way to design non-imaging optics is called the "edge-ray method" or "the method of strings" [http://oemagazine.com/fromTheMagazine/aug05/tutorial.html ] . Other more advanced methods were developed starting in the early 1990s that can better handle extended light sources than the edge-ray method. These were developed primarily to solve the design problems related to solid state automobile headlamps and complex illumination systems. One of these advanced design methods is the Simultaneous Multiple Surface Method (SMS). The 2D SMS design method (US Patent 6,639,733) is described in detail in the aforementioned textbooks. The 3D SMS method, the most advanced design approach to date, was developed in 2003 by a team of optical scientists at Light Prescriptions Innovators. The method is described in detail in the scientific paper "Simultaneous multiple surface optical design method in three dimensions", Optical Engineering, July 2004, Volume 43, Issue 7, pp. 1489-1502.