Modeling and Design of Grating Cell Diffusers for Display and Lighting Applications

The use of diffusers gains momentum in lighting and display applications. It is helpful to distinguish between diffusers which work for a paraxial or even convergent incident light fields and diffusers for strongly divergent fields. In the first case iterative diffractive optics design techniques can be applied directly. Diffusers for Excimer lasers can be designed in this way. In our talk we discuss the situation for highly divergent incident fields as we have it in case of LED lighting and also in the design of diffusers for display applications. We show, that then a multi-channel diffuser concept is the logical choice. In its simplest implementation we consider a diffuser, which is composed of a grid of grating cells. We discuss our solutions for its design and modeling of the scattered pattern. Here ray tracing is not a suitable modeling technique. However, also the physical optics approach must be significantly further developed to handle the enormous amount of data. In addition, the partial lateral coherence of LEDs must be included. We discuss the theory and demonstrate examples using VirtualLab(TM) as modeling and design software.