US Patent 10379358 Optical see-through display element and device utilizing such element

An optical see-through display element and a display device using such an element. The element having a transparent substrate including two opposite faces, an in-coupling structure for coupling light into the substrate, and a diffractive out-coupling grating structure arranged on the transparent substrate for displaying the in-coupled light on the transparent substrate. The diffractive out-coupling structure includes at least two multi-layer gratings superimposed on top of each other on at least one of said opposite faces of the substrate. In particular, multilayer gratings reducing diffraction of transmissive light can be used. The element and device help to increase the out-coupling efficiency of diffractive displays and provides also technology to simultaneously maintain high image quality and transparency.