Dalma Héricz

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.

We propose a compact head-worn 3D display which provides glasses-free full motion parallax. Two picoprojectors placed on the viewer’s head project images on a retro-reflective screen that reflects left and right images to the appropriate eyes of the viewer. The properties of different retro-reflective screen materials have been investigated, and the key parameters of the projection – brightness and cross-talk – have been calculated. A demonstration system comprising two projectors, a screen tracking system and a commercial retro-reflective screen has been developed to test the visual quality of the proposed approach.