CEA LETI prints pixelated hologram on miniature 6 x 6mm component

12 Oct 2020

Achievement by French research group opens the door to holograms being presented on augmented reality glasses.

Holographic effect is achieved by engraving hoels on a hundred 200 nm layers.

What if tomorrow holograms could be displayed on augmented reality glasses? French research institute CEA-Leti says it has achieved a major step towards this aim by printing pixelated holograms on a “postage stamp format” component, measuring only 6 x 6 mm²).

Augmented reality glasses allow viewers to observe a real scene, while viewing additional information relevant to the scene: explanatory text, instructions, diagrams, photos, and the like.

CEA-Leti's ambition is to use holograms, or volumetric optical components, in micro- and nano-photonic manufacturing processes for AR applications and beyond.

To avoid reducing the visual field, these holograms must be displayed in an approximately postage stamp size area; a few tens of square millimeters.

Laser illuminated

Specifically, this involves printing on this surface holographic pixels or "hoels" to reconstruct a coherent image in the back of the eye, when illuminated by laser microsources. This technological challenge has now been met.

Motifs are printed within a transparent photopolymer volume.

Christophe Martinez, manager of CEA-Leti's Retina Projection Program, commented, “In practice, we print these hoels, several microns in diameter, within a 16-micron-thick transparent photopolymer volume using a 532 nm laser.

The holographic effect is obtained by engraving them on around one hundred 200 nm layers featuring angular disparities. The writing process is totally repeatable to control hoel size, period and pitch.”

This success, complemented by the registering of a patent, represents a first step. The researchers now plan to evaluate several photopolymers because printing quality depends closely on material characteristics.

Moreover, they are currently limited to static holograms but want to “go dynamic” by activating and deactivating hoels by component external then internal illumination. This is the subject of a number of doctoral cooperations with the University of Haute Alsace, in Mulhouse, France.