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AR HUD Using a Birefringent Eyepiece


The two channels, the see through channel and the augmenting channel are orthogonally polarized and are combined using a polarization combiner such as a Moxtek wire grid polarizer.

The eyepiece is made of birefringent elements. It has essentially no power for polarized light in the vertical direction used for the see through and has significant power between 30 to 60 mm focal length for polarized light in the horizontal polarization used for the augmenting channel.

The polarizations for the see through and augmented channels can be reversed. The choice for vertical polarization for the see-through is to provide the function of polarized sun glasses in reducing glare from say wet surfaces.

The see-through is shown as collimated but can be designed also to focus at objects about 0.5 meter or other distances considerably larger than the focal length of the augmented channel.

The display is shown as flat but it can preferably be curved spherically or cylindrically for control of field curvature.

The PBS is preferably a wire grid polarizer such as made by Moxtek or Ashahi kasai. Additional lenses can be placed between the display and the PBS such as a field lens at the proximity of the display.

Other highly birefringent crystals can be used like Rutile (Tio2).