In recent years, there is a growing need for lighting equipment that creates complex, specific illumination, and light intensity distributions, such as road surface drawing lamps, aesthetic design lighting, and direct backlighting. When designing such lighting equipment, we may often have to use a cut-off method, which is a method of projecting a partially shaded image.

What are the challenges for Illumination design?

The cut-off method has inefficient throughput of light, as we are purposefully cutting off the light source for illumination. To eliminate the cut-off light loss, more complex optical components, with the freeform shape is the highest candidate, is explored. The development of manufacturing capabilities has made feasible the fabrication of more complex freeform shapes, although the asymmetric nature of the illumination requirements makes it challenging.

What are the benefits?

This has opened the possibility of new design approaches. We propose a design solution that meets the high demand for illumination performance in a more straightforward optical configuration, using complex free-form surfaces and a ray mapping approach as opposed to optimization by flooding the detector with millions of non-sequential rays. Freeform surfaces go outside the realm of a rotationally symmetric surface and find efficiency in the system and decrease the number of optical elements.

A conventional optical surface utilizes a parametric equation for the illumination lens, which can be challenging to control for higher orders of the polynomial function. The optical lens designed with conventional methods require complex parts and, in the end, has a low light efficiency due to the shading of the light source. The proposed illumination method takes advantage of a lighter computational approach via ray mapping. It leverages the spatially selective surface sag over a grid of points in the OpticStudio TrueFreeForm^TM surface.

Join Zemax’s Katsumoto Ikeda, Principal Optical Engineer for a webinar on: TrueFreeForm Optimization for Complex Illumination Systems where he introduces illumination and freeform surfaces, Optimization strategies; practical examples - Direct Method and ray mapping, and why the OpticStudio TrueFreeform surface solution is highly efficient.

For an academic paper, read Katsumoto Ikeda’s presentation from SPIE’s OPTO event at Photonics West.

Katsumoto Ikeda 
Principal Optical Engineer
Zemax