The Technology that Will Push VR Beyond the Limits of Human Eyes

The large size of headsets today is due to the number of optical elements that they contain and the need for sufficient space between them and displays to properly focus light. While new compact lens designs and the use of metasurfaces–nanostructured films with unique optical properties–have allowed some miniaturization in this area, say the authors, this is likely reaching its limits.

Innovative designs such as “pancake lenses” and holographic lenses that bounce light between various bits of glass or plastic could reduce the distance from the lens to the display by two to three. Each interaction reduces the brightness of images and must be compensated by more powerful, efficient displays.

To overcome another limitation of today’s devices, better displays are needed. Ultra-HD TV screens can reach pixel densities up to 200 pixels per degree (PPD), at distances of approximately 10 feet. This is far more than the 60 PPD the human eye can discern. VR displays can only achieve 15 PPD because they are just an inch from the viewer’s eyes.

The latest smartphone’s screen manages just 460 pixels per inch.

The authors state that VR displays must squeeze between 7,000 to 10,000 pixels per inch to match the resolution limitations of the human eye.  There are clear ways to close that gap, despite its enormity of it. Currently, VR headsets are made with separate red, green and blue organic light-emitting diodes (OLEDs). These OLEDs are difficult to compact because of their manufacturing process. An alternative method that uses colored filters on white OLEDs to increase the power per hour (PPD) could be possible.

Filtering can be a challenge as it lowers the efficiency of the light source. This results in lower brightness and higher power consumption. A new OLED design, known as a meta-OLED, could circumvent this problem by using a combination of the light source and nanopatterned mirrors that use the phenomenon called resonance to emit light at a specific frequency.

Meta-OLEDS may be able to achieve pixel densities exceeding 10,000 PPD. This is close enough to the physical limits established by the wavelength of light. They are also more efficient than previous generations and could have better color definitions. Despite the interest shown by display technology companies for this technology, it is still in its infancy and unlikely to be commercialized.

According to the authors, the most promising near-term innovation in displays is one that exploits an anomaly of human biology. The central region of the retina known as the fovea is the only area that can distinguish 60 PPD. However, the eye has a significantly lower ability to detect the peripheral.

You only need to render the best definition for the section of the display the user is viewing if eye movements can accurately be tracked. Although the design of the display is more complicated due to the need for improved eye and head tracking, the authors believe this innovation will be the most effective.

If VR is to be widely commercialized, there will need to be a lot more than better displays. Particularly, the powering of these headsets presents complex challenges in terms of battery capacity and heat dissipation from the onboard electronics.

The researchers also discussed display technologies that are relevant to VR, not AR. VR headsets will likely use a different type of optical technology that doesn’t obscure the user’s view of the world. Regardless of the outcome, it appears that immersive virtual experiences may still be a ways off but that there are clear steps to get us there.