US Patent 11619817 Pancake lenses using Fresnel surfaces

A head-mounted display includes a pancake lens block. The pancake lens block includes a first waveplate to form first nonlinearly polarized light, a Fresnel surface to reflect and transmit a portion of the first nonlinearly polarized light, a second waveplate to form first linearly polarized light, and a linear reflective polarizer to transmit linear polarized light of a particular polarization rotation direction and to reflect light of other polarization rotation directions.