The $300 hologram display
Wed 8 Jun 2016
Princess Leia’s first holographic appearance in Star Wars (1977) remains the lodestar for generations of geeks – many of them scientists – who are interested in real world, glasses-free holography – and, for that matter, emerging VR and AR technologies such as Microsoft’s HoloLens.
(If you retain the notion of a respectful gap between basement-dwelling Star Wars geeks and ‘serious’ researchers, consider what a major holographic tech venture decided to call itself)
Over five years ago Sony demonstrated an innovative flat panel autostereoscopic 3D display at SIGGRAPH which recalled the hologram/laser obsession of the 1970s – but in colour and at good resolution. The omnidirectional Sony Raymodeller display was developed by Sony and Osaka University, drawing admiration from attendees, and able to provide a convincing holographic illusion by projecting optically distorted material into a cylindrical space to provide a convincing 360-degree colour panoramic image, including moving images:
However the component parts and fabrication process were considerable obstacles, according to a Chinese researcher Che-Hao Hsu, with constituent parts such as lenticular lens arrays, directional backlights and parallax barriers promising prohibitive production costs.
Two years later Hsu re-purposed [PDF] the prototype into a functioning version costing less than $300, but there’s little in evidence today of his dirt-cheap Leia-cam. I found this video below which explains the core concepts behind the holographic cylinder, and footage of the device in action – showing a 3D rabbit – starts at 1:59:
The paper, entitled Omni-Tube: A Low-Cost Portable Omnidirectional Interactive 3D Display, explains that the device uses motion detectors to display whichever slice of the multiple possible images would be appropriate for the viewing angle, and presents that to the viewer. Resolution is limited only by the maximum resolution of the projector powering what is, in effect, a tube-shaped screen.
According to Hsu the cylindrical display zone ‘consists of a diffuse material and a specially designed thick barrier sheet which produces different brightness attenuation for different viewing angles. Based on our considerable amount of user studies, this special-purposed thick barrier sheet significantly improves the 3D depth perception for human beings.’
The striking aspect of Omni-tube is that it is in effect just a screen for a projector, and therefore capable of being considered an accessory for an already existing purchase – although the software to generate the pre-distorted source material combines with the cost of scanning to make home-brewed holograms strictly for dedicated hobbyists.
But it is worth keeping an eye (preferably two) on glasses-free holographic display technologies, particularly as the HoloLens currently suffers from such a limited ‘area of activity’ that its vision of room-filling holograms is still rather speculative.