A diffraction limited optical system for head mounted displays (HMDs) was designed. This optical
system consists of four modules, including 1:5 mm and 5:30 mm beam expanders, polarization gratingpolarization
conversion system (PG-PCS) and refractive/diffractive projection optical module. The PG-PCS
module transforms the unpolarized Gaussian beam to a linearly polarized beam and it simultaneously
homogenizes the spatial intensity profile. The optical projector module has a 30° field of view, a 22 mm
eye relief, and a 10 mm exit pupil diameter with a compact structure. Common acrylic materials were
utilized in the optical design process; therefore, the final optical system was lightweight. The whole optical
system is suitable for a 0.7 inch liquid crystal on silicon microdisplay (LCOS) with HDTV resolution
(1920×1080) and 8.0 μm pixel pitch.