A head mounted display is disclosed. More particularly, a head mounted display including one or more projection light sources, one or more eye-tracking light sources, a polarizing beam splitter, and a second polarizing beam splitter is disclosed. Light from the one or more projection light sources and the one or more projection light sources and the one or more eye-tracking light sources are both at least partially reflected by the polarizing beam splitter. An optical path between the polarizing beam splitter and the second polarizing beam splitter passes through air. A head mounted display that utilizes polarizing beam splitters having certain reflection bandedges over a range of incidence angles is disclosed.