Abstract: A parallel plate waveguide assembly for conveying an image bearing light from an in-coupling optic to an out-coupling optic is disclosed wherein the waveguide assembly includes at least a waveguide blank having a first surface and a second surface located a distance from the first surface to create a thickness of the blank. The waveguide assembly further includes a first coating applied to the first surface forming a third surface and a second coating applied to the second surface forming a fourth surface. The third and fourth surfaces are less than a quarter of a wavelength of an image bearing light beam in flatness.