See-through displays, including head-up displays (HUD) and augmented reality (AR) displays, allow the viewer to see both the natural world and a projected image thanks to a combiner element. To offer larger field of view (FOV) and an increased eye box, holographic combiners have been used in the past. Most recently, a new type of combiner has been developed using waveguide and edge-lit holograms. The waveguide is used to recirculate the light several times while it propagates inside the material by total internal reflection (TIR). The edge-lit holograms are used to inject, redirect, and extract the image inside the waveguide. Holograms are particularly well suited for see-through applications since they are light, thin, and can be applied on curve substrate without inducing distortion.
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