CEA-Leti has developed a novel retinal-projection system for augmented reality (AR) applications, based on integrated optics and holography, thus overcoming the limitations of existing AR glasses that suffer from limited field-of-view and bulky optical systems.
TVs and smartphones that project digital images emit light as quasi-isotropic sources. Because the images are projected generally over the air without directivity, many viewers see the same image. In typical AR glasses, images are transmitted close to the eyes (high directivity) by a microdisplay that includes an optical system and an optical combiner. These microdisplays create a small near-to-eye image, which is transformed by the optical system, enabling the user to see it despite the short focusing distance. The combiner superimposes the digital image to the viewers’ vision of the real environment.
CEA-Leti’s innovation is a transparent retinal-projection device that projects various light waves to the eyes from a glass surface. Images are formed in the retina by the interference of light waves, which eliminates the need for optical systems or combiners. The light propagating in the air doesn’t form an image until it interferes precisely in the retina.
The integration of the device and the holographic layer enable compact AR glasses with a larger field-of-view than existing systems, while the transparent retinal projection device allows ambient light to pass through the device for enhanced AR applications.
“Combining integrated optics and holography is a new research area for the scientific community developing display applications,” said Basile Meynard, a Ph.D. student working on the project. “It is also a way to imagine a display device that works more as a data transfer system than as an imaging system.”
The novel approach will require further development before it reaches commercial stage. In the medium to long term, the retinal projection concept is expected to support more compact and higher virtual-image quality applications similar to existing AR glasses.
“Our teams are continuously looking for potential disruptive technologies that could pave the way to new families of display devices,” said Christophe Martinez, optical senior scientist and project leader in Leti. “The investigation on retinal displays is part of this exploration of future optical solutions.”
[Image credit: Uriel Soberanes for Unsplash]