Diffractive exit-pupil expander with a large field of view

A concept of asymmetric exit-pupil expansion for head-worn virtual displays is introduced. Expression for the achievable field of view (FOV) of a stack of asymmetric pupil expanders is derived. Comparison with the symmetric case indicates a possibility for doubling the horizontal FOV for given material parameters and spectral bandwidth. Using the parameter values of readily available plastics, the horizontal field of view approaching the viewing conditions of typical desktop monitors should be possible. Moreover, improvement of the illumination uniformity can be achieved through optimized positioning of the out-coupling diffraction gratings.