Head mounted display architectures for 3D augmented reality
Augmented reality (AR) is the enhancement of our perception of the world around us. It promises the ability to simultaneously interact with a virtual environment and real objects, providing an intuitive method to interact with data. However, AR displays must be lightweight and compact, and be able to display bright, high-resolution 3D images. Current AR displays are limited by bulky-form factors with a limited field of view (FOV), and the inability to display high quality 3D images without introducing side effects such as nausea and eyestrain.
In the first part of this thesis an afocal Maxwellian display is analysed and modelled, the small eyebox limitation examined and a solution proposed. A prototype head mounted display unit was constructed as a demonstration. The display performance was analysed objectively and subjectively, and found to perform well over a wide accommodation range. However, the system is mechanically complicated to provide for a large IPD demographic, and the implementation of the eyebox expansion is too limited. An alternative curved reflector system was proposed to reduce weight, increase FOV, and increase the eyebox.
The final part of this research examines waveguides as an AR display technology. The limitations of current systems are evaluated, and a novel switchable waveguide architecture proposed where light can be selectively directed towards the eye to form an image time sequentially. This enables higher quality images, with a wider FOV and increased efficiency, from a more transparent waveguide. A liquid crystal diffraction grating is developed as a switching element with a simulated diffraction efficiency of 20% and a geometry optimised for easy industrial manufacture. The possibility for such a system to include an integrated lens function is also considered, and an 80° FOV design presented.