US Patent 11237413 Multi-focal display based on polarization switches and geometric phase lenses

Some implementations disclosed herein include devices, systems, and methods that display images at multiple focus distances on HMDs. The systems can avoid or mitigate vergence-accommodation conflict (VAC) and depth-blur conflict (DBC) experienced by users on traditional HMDs. Some implementations use a geometric phase lens and a circular polarization switch. The geometric phase lens passively changes its power depending on the light's circular polarization. The circular polarization switch changes the polarization of the light at appropriate times. With the circular polarization switch and geometric phase lens positioned over an HMD screen, the system can quickly change the apparent distance to the screen, which in turn changes the accommodative state of the eye needed to focus on the rendered image.