Simulation of small- and wide-angle scattering properties of glass-bead retroreflectors

Retroreflective materials are extensively used as traffic signs and security patterns. These goods are often realized by spherical glass-beads attached to some reflective substrate. New applications, especially 3D projection, require the precise evaluation and design of the characteristics of light backscattered from retroreflective screens. Simulation of such materials is not straightforward due to the different optical processes taking place: direct retroreflection involving small-angle diffraction effects, and multiple scattering resulting in wide-angle diffuse light. We propose a new complex method to describe the backscattering properties of glass-bead retroreflectors that uniquely combines diffraction calculations with ray tracing based on the microscopic properties of the screen. We validated our simulation method by measurements performed on commercial retroreflective samples.