Abstract: A display device may include a guide, a back side coating, a front side coating, an input couple, and output coupler, and an image source. The guide may include a guide front side and a guide back side opposite the guide front side. The back side coating may line the guide back side and may reflect rays in a first waveband. The front side coating may line the guide front side and may reflect rays in a second waveband. The image source may emit rays toward the guide. The input coupler may receive the rays emitted by the image source and couple the rays into the guide. The output coupler may receive rays propagated along the guide between the guide back side and the guide front side and emit the received rays from the guide front side.

Abstract: It has been discovered that optical filters can be manufactured with a low net stress by providing a tensile layer or layers that compensate for a compressive stress exhibited by a thin film filter supported by a glass or other substrate. In particular, a simple, cost-effective and readily reproducible process is used wherein a layer or layers of tensile material such as zirconia is used between the thin film filter and the substrate to offset compressive forces within the remaining structure, so as to provide a low or near zero net stress on the filter. Zirconia (ZrO2) is substantially transparent, inert, and non-interfering, thereby not affecting the output response of the multilayer thin film filter. It's presence is merely to provide a counter stress effectively neutralizing stresses that would otherwise occur from the presence of the thin film filter alone.