Computational 3D Displays
Tomographic displays correspond to the inverse reconstruction of discrete tomographic imaging. Using a set of projected images, discrete tomographic imaging finds optimal volumetric binary image slices. This reconstruction process could be adopted for layer image determination of tomographic displays.
Tomographic displays consist of three parts: fast spatially adjustable backlight, display panel, and focus-tunable lens. The combination of three elements allows reconstruction of more than 80 focal planes at 60 Hz. Although each focal plane has some correlation, it is feasible to find optimal solution that reconstructs accurate volumetric scenes. The optimal solution can be found by applying an optimization algorithm used for discrete tomographic imaging.
Multi-layer displays capture or render a 3D scene and pickup 7 by 7 orthographic views. And then, this 49 views are compressed and decomposed into layer images via optimization and computer processing. Finally, the 3D scene can be reconstructed by multi-layer displays.
Optical Technologies for Near-Eye displays
Holographic Optical Elements (HOEs)
HOEs can be considered as wavefront transformers that convert a specific wavefront to a predefined wavefront. Fundamental principle of HOEs is similar to that of volume Bragg gratings, which diffract an incident beam from a specific direction in a predefined way. HOEs are recorded by an interference pattern between reference and signal waves. We can suppose that the reference and signal waves correspond to input and output variables of the wavefront transformer. When the reference wave is introduced to the HOE after recording process, the HOE diffracts and converts the reference wave to the signal wave. On the other hand, when a different wave is introduced to the HOE, the wave passes through the HOE without diffraction.
Optical System Design
A projected image on the diffuser is floated on a virtual plane by the hologram lens. As ‘3D AR’ is floated on the plane at 50 cm from the HOE, blurred text is observed when camera focuses on a closer plane.