Researchers have found a new way to make ultrahigh-density 3D holographic images that are both dynamic and moving. By incorporating more details into a 3D image, this sort of hologram could make it feasible to show the real world in virtual reality and other settings.
"A 3D hologram can present real 3D scenes with continuous and fine features," said Lei Gong, who led a research team from the University of Science and Technology of China. "For virtual reality, our method could be used with headset-based holographic displays to greatly improve the viewing angles, which would enhance the 3D viewing experience. It could also provide better 3D visuals without requiring a headset."
To make a holographic display of 3D objects that looks real, images with a high pixel density must be projected onto many close-together planes, or layers. This makes it possible to get a high depth precision, which is vital for giving the hologram depth cues that make it look three-dimensional.
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In Optica, Gong's team and Chengwei Qiu's team at the National University of Singapore outline their new method, which they call 3D scattering-assisted dynamic holography (3D-SDH). They show that it can offer better depth precision than the best multiplane holographic projection methods by more than three orders of magnitude.
Creating a more realistic hologram
"Our new method overcomes two long-existing bottlenecks in current digital holographic techniques -- low axial resolution and high interplane crosstalk -- that prevent fine depth control of the hologram and thus limit the quality of the 3D display," said Gong. "Our approach could also improve holography-based optical encryption by allowing more data to be encrypted in the hologram."
Changing the strength and/or phase of a light beam is usually how a spatial light modulator (SLM) is used to make a dynamic holographic image. But the quality of holograms today is limited because the SLM technology available can only cast a few low-resolution images onto separate planes with low depth clarity.
To solve this issue, the researchers put together an SLM and a diffuser. This lets multiple picture planes be much closer together without being limited by the SLM's properties. This setup makes it possible to cast ultrahigh-density 3D holograms by preventing crosstalk between the planes and taking advantage of light scattering and wavefront shaping.
