Augmented reality wearables are becoming more mainstream as tech giants like Google, Apple along with several startups are investing time and money on them. So far one of the biggest concern/hurdle of the wearables is pertaining to the display technology.
There are range of transparent display technologies available out in the market. The following factors influence the AR wearable company to decide amongst the available display technologies.
- Optical performance
- Size and weight of the display
- Field of view
- Mass producibility
Conventional combiner display are more commonly used by companies including Epson Moveria, Google glasses and Meta. This display uses semi transparent mirrors with prisms to project the content onto users eye. The fundamental issue with this technology is that the size of the prism and hardware grows exponentially larger as the field of view [FOV] increases. This makes the AR wearable heavy and cumbersome with higher FOV.
The evolution of waveguide display
Waveguide displays on the other hand are compact thereby reducing the size and weight of the hardware.
Waveguide displays are made using the same technology that allows a unidirectional wave of light to be guided down a fiber optic cable. Waveguide lenses use this same property of a unidirectional light-wave to guide a wave of light through a lens or plane (planar waveguide), from one end to the other. Nokia’s patent here is quite notable because it has shown to be mass-producible. The earliest waveguide implementation, by Microsoft in its Hololens is of Nokia’s design.
Types of waveguide displays
They are also categorized as surface release waveguides. They use rows of semi transparent mirrors for the augmented reality experience. The manufacturing is also complicated and needs high level of precision and accuracy. The size of the display is also not that compact as diffractive waveguides as we need to house the several layers of mirrors in an angle. Microsoft’s Hololens uses this technology. This explains the reason for its lower FOV despite the state of the art technology that it houses.
Diffractive waveguides or holographic waveguides uses optical nano structures located in specific areas called as gratings instead of several layers of glasses. This allows the eye to view hologram with a much higher field of view in a compact way without compromising on the optical performance. Magicleap uses this technology.
In conclusion Waveguide displays are becoming more compact without compromising on the resolution, field of view and also are becoming more capable of being mass produced. With advancement in material used for making lens, usage of active holographic optics diffractive waveguide technology is going to make the wearables more commonly available and cost effective.