innovation for industry
Eliminates the Need for Optical Systems and Combiners in AR;
Will Be Presented
at SPIE Photonics West 2019
TVs and smartphones that project digital
images emit light all around them, 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
CEA-Leti presented its
results Feb. 6 at SPIE Photonics West 2019 in a paper titled “Integrated Optical Network
Design for a Retinal Projection Concept Based on Single-Mode Si3N4
Waveguides at 532 nm”.
project focused on the design and numerical simulations of integrated Si3N4
optical components and the optical circuit at λ = 532 nm. It required building blocks
for designing an optical integrated
circuit capable of creating an array of emissive points. Starting with
single-mode waveguides to efficiently transport light around the circuit, many
other components were designed to manipulate light in different locations.
Components for extracting the light, such as diffraction gratings, were also
designed and simulated. The team minimized losses of different parts of the
circuit, such as waveguide-bending areas, to increase energy efficiency of the
integration of the
device and its use of a holographic layer also allow creation of 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.
integrated optics and holography is a new research area for the scientific
community developing display applications,” said Basile Meynard, a Ph.D. student and lead author
of the paper. “It is
also a way to imagine a display device that works more as a data transfer
system than as an imaging system.”
novel approach will require further development before it reaches the
commercialization 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.
project builds on CEA-Leti’s many years of development of micro-displays for
near-to-eye displays, such as organic LED technologies (OLED) and liquid
crystal devices (LCD). More recently, the institute has made significant strides
in the field of inorganic LED display manufacturing.
teams are continuously looking for potential disruptive technologies that could
pave the way to new families of display devices down the road,” 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.”
CEA is a French government-funded technological research organisation in four main areas: low-carbon energies, defense and security, information technologies and health technologies. A prominent player in the European Research Area, it is involved in setting up collaborative projects with many partners around the world.