US Patent 11803062 Optical system and head-mounted device

An optical system includes an aperture stop, an image display surface, a reflective polarizer, a partial reflector, first and second quarter-wave plates, and first, second and third optical lens elements. The aperture stop and the image display surface are respectively at front side and rear side of the optical system. The reflective polarizer is between the aperture stop and the image display surface. The partial reflector is between the reflective polarizer and the image display surface. The first quarter-wave plate is between the reflective polarizer and the partial reflector. The second quarter-wave plate is between the partial reflector and the image display surface. The first, second and third optical lens elements are between the aperture stop and the image display surface in order from the front side to the rear side. The first optical lens element has negative refractive power. The second optical lens element has planar front-side surface.