Pancake window optical device with thin film helicoidal bianisotropic medium

摘要

An optical device (44), which functions as a pancake window so as to form a collimated image at or near infinity, consists of two beam splitters, one being a semi-reflective mirror (54), the other being an optical filter comprising a thin film helicoidal bianisotropic medium (56) on a substrate (62). The optical device is such that circularly polarised light (60) is made to follow a 180{ reflex path. This can be because the circularly polarised light (60) emanating from light source (46) is first reflected by optical filter (56) and then the polarity is reversed by being reflected by semi-reflective mirror (54) whereupon the light is transmitted through optical filter (56) to the eye (58). The device may be used in a head mounted display for virtual reality equipment to provide a collimated image without the need for heavier and more bulky lenses.