AR Waveguide Outcoupling With Overlaid Diffractive Elements

The patent applies local quality by making the two diffractive optical elements have different diffraction efficiencies rather than being uniform. The first diffractive optical element has a higher diffraction efficiency while the second has a lower diffraction efficiency, creating spatial variation in optical properties across the waveguide surface. This allows different regions to perform different functions: the first element primarily expands light while the second element preferentially couples light out, thus resolving the contradiction between space utilization and optical efficiency.

The patent segments the diffractive optical elements into two distinct types with different functions. The first diffractive optical element is optimized for expanding light in two dimensions with higher diffraction efficiency, while the second diffractive optical element is optimized for coupling light out of the waveguide with lower diffraction efficiency. This segmentation allows the system to simultaneously achieve broad light expansion coverage and efficient light outcoupling, resolving the contradiction between coverage area and optical power transfer efficiency.

The patent converts the previously harmful effect of light being trapped and wasted in the waveguide into a beneficial outcome. By using diffractive optical elements with different diffraction efficiencies, the system ensures that light which would otherwise be lost is instead efficiently coupled out to the user's eye. This increases optical efficiency and reduces the power required to achieve the same display brightness, thereby extending battery life while maintaining full augmented reality functionality.