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Conventional approaches based on space- or time- multiplexing can provide multifocal functionality but with a significant sacrifice in resolution or frame rate. As a novel alternative, polarization multiplexed methods can avoid these drawbacks, but they can only achieve two focal depths since there are only two orthogonal polarization states. The wavelength multiplexing proposed here is intrinsically free from all the limitations mentioned above. Firstly, as a proof of concept, we built a dual-focal near-eye display using off-the-shelf optical components. The prototype is designed based on a birdbath architecture with an extra spectral notch filter as the wavelength-sensitive depth separation element. The optical powers for the two wavelength sets are determined by the distance between the reflector and notch filter. Our benchtop demo can generate two focal depths simultaneously, which are located at 1 m and 2 m away from the optical combiner. Moreover, another compact optical design of a wavelength-multiplexed dual-focus light engine for lightguide type AR displays is also presented. Also, we analyze the implementation of full-color operation and demonstrate an angle insensitive multi-notch filter design based on optical multi-layer coatings. Finally, we discuss practical limitations and potential improvement of the proposed wavelength multiplexing method for overcoming the VAC issue. |
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CITATIONS
Cited by 1 scholarly publication.
Multiplexing
Projection systems
Augmented reality
Head-mounted displays
Optical filters
Polarization
Digital micromirror devices
