New Display Design Could Make Lightweight, Compact Smart Glasses a Reality

10 Oct

Researchers have developed a fundamentally new approach to a see-through display for augmented reality, or smart glasses. By projecting images from the glass directly onto the eye, the new design could one day make it possible for a user to see information such as directions or restaurant ratings while wearing a device almost indistinguishable from traditional glasses.

“Rather than starting with a display technology and trying to make it as small as possible, we started with the idea that smart glasses should look and feel like normal glasses,” said research team leader Christopher Martinez of the Laboratoire d’électronique des technologies de l’information (Leti) in France. “Developing our concept required a great deal of imagination because we eliminated the bulky optical components typically required and instead use the eye itself to form the image.”

In Optica, The Optical Society’s journal for high-impact research, the authors detail their new retinal projection display concept and report positive results from initial optical simulations. Although glasses using this new approach wouldn’t be useful for showing videos, they could provide information in the form of text or simple icons.

“Although we are focused on augmented reality applications, the new display concept may also be useful for people with vision problems,” said Martinez. “The disturbance present in the eye could be integrated into the projection, giving visually impaired people a way to see information such as text.”

Forming an image in the eye

The unconventional display design rapidly projects individual pixels, which the brain puts together to form letters and words. “We don’t bring an image to the surface of the glass, but instead bring information that is emitted in the form of photons to make the image in the eye,” explained Martinez.

According to the design concept this feat would be accomplished by sending photons from a laser or other light source through a light-guiding component into a holographic optical element created within the lens of the glasses. Holographic optical elements that are significantly smaller than their traditional counterparts can be made in light-sensitive plastics using the same laser light interactions that make holograms such as those that protect credit cards from forgery.

For the concept to work, it is critical that all the projected photons have synchronized phases and match in coherence. Otherwise, a noisy image is formed, akin to what you would hear if the members of a choral group were singing the same song but starting and stopping at different times. The researchers used the holographic element to synchronize the phase, like a cue that helps the singers start at the same moment.

“It is very complicated to use traditional methods such as a mask with an optical structure to adjust the phase of photon emitters that are separated from each other by just hundreds of microns,” said Martinez. “Our design uses a unique holographic element to synchronize the photons by matching the phase with a reference beam.”

The design also includes a grid of lightguides that makes the photons coherent, akin to making sure the singers all sing at the same speed. This component was made using an integrated photonics approach that incorporates the same semiconductor fabrication techniques used to make computer chips and fabricate optical components in silicon.

The researchers say that their display concept is an important example of the new opportunities for retinal projection that will now be possible thanks to recent developments in integrated photonics, which have moved from applications using telecommunication wavelengths into visible wavelengths that can be used in displays.

Facebook Comments