Researchers from Fb Actuality Labs have shared new strategies for the design & fabrication of compact holographic lenses to be used in XR headsets.
The lenses utilized in most of as we speak’s XR units are typical refractive lenses which will be pretty cumbersome, particularly as they’re optimized for sure optical traits. Fresnel (ridged) lenses are continuously utilized in XR headsets to enhance optical efficiency with out including an excessive amount of bulk.
In concept, holographic lenses are a promising strategy for XR optics due to their capacity to carry out the identical (or much more superior) capabilities of a standard lens, however within the area of a wafer-thin movie. Nevertheless, designing and fabricating holographic lenses with excessive optical efficiency is much harder as we speak than it’s with typical refractive optics.
In an effort to maneuver us one step nearer to the sensible use of holographic lenses in XR units, Fb Actuality Labs researchers Changwon Jang, Olivier Mercier, Kiseung Bang, Gang Li, Yang Zhao, and Douglas Lanman have detailed new strategies for creating them. This might go a good distance towards making it attainable to construct, at scale, the sort of compact XR glasses Fb lately demonstrated.
In a paper printed within the peer-reviewed journal ACM Transactions on Graphics (Vol. 39, No. 6, Article 184) in December, titled Design and Fabrication of Freeform Holographic Optical Parts, the researchers write, “we current a pipeline for the design and fabrication of freeform [Holographic Optical Elements (HOEs)] that may prescribe quantity gratings with advanced part profiles and excessive selectivity. Our strategy reduces picture aberrations, optimizes the diffraction effectivity at a desired wavelength and angle, and compensates for the shrinkage of the fabric throughout HOE fabrication, all of that are extremely helpful for VR/AR functions. We additionally show the primary full-color caustic HOE for instance of a fancy, however smoothly-varying, quantity grating.”
Particularly the paper covers optimization strategies for establishing a theoretical holographic lens design, and two approaches for truly manufacturing it.
One makes use of a pair of freeform refractive optics to create the goal hologram; the paper proposes the strategy for creating the refractive optics such that they precisely kind the goal hologram throughout the holographic movie. The opposite entails a holographic printer used to create the goal hologram from tiled holographic patches; once more the paper proposes the strategy for optimizing the method to most precisely recreate the goal hologram throughout the holographic movie with this particular strategy, which they are saying is a very completely different problem from the primary methodology.
Whereas the paper didn’t discover fairly this far, the authors say that future analysis might try to use these identical strategies to curved, quite than flat, surfaces.
“For some VR/AR functions, it may very well be helpful to create HOEs with bodily curved form-factors, for instance, for HOEs laminated on curved windshields or glasses. We anticipate our fabrication framework to broaden effectively to such instances, since neither the printer or the [refractive lens] approaches require the HOE to be flat, and the optimization methodology of Algorithm 1 may very well be tailored to intersect rays with a curved floor […],” the researchers write. “Optimizing the form of the HOE as a part of our methodology would supply us with extra levels of freedom and would broaden functions, however we go away this as future work.”
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