Holography, light-field technology combo could deliver practical 3-D displays

[Nergal]

 

While most interaction with digital content is still constrained to keyboards and 2-D touch panels, augmented and virtually reality (AR/VR) technologies promise ever more freedom from these limitations.

AR/VR devices can have their own drawbacks, such as a tendency to induce visual motion sickness or other visual disturbances with prolonged usage due to their stereoscopy or auto-stereoscopy based designs. One promising solution is to adapt holography or light field technology into the devices instead. This, however, requires additional optics that would increase the size, weight, and cost of these devices -- challenges that have so far prevented these devices from achieving commercial success.

Now, a group of researchers in Japan and Belgium has begun to explore a combination of holography and light field technologies as a way to reduce the size and cost of more people-friendly AR/VR devices. They will present their work during The Optical Society's (OSA) Frontiers in Optics meeting, 16-20 September, in Washington, D.C. One of the themes of the meeting is virtual reality and augmented vision, with both a visionary speaker and a series of invited talks on those subjects.

"Objects we see around us scatter light in different directions at different intensities in a way defined by the object's characteristic features -- including size, thickness, distance, color, texture," said researcher Boaz Jessie Jackin of the National Institute of Information and Communication Technology in Japan. "The modulated [scattered] light is then received by the human eye and its characteristic features are reconstructed within the human brain."

Devices capable of generating the same modulated light -- without the physical object present -- are known as true 3-D displays, which includes holography and light-field displays. "Faithfully reproducing all of the object's features, the so-called 'modulation,' is very expensive," said Jackin. "The required modulation is first numerically computed and then converted into light signals by a liquid crystal device (LCD). These light signals are then picked up by other optical components like lenses, mirrors, beam combiners and so on."

The additional optical components, which are usually made of glass, play an important role because they determine the final performance and size of the display device.

This is where holographic optical elements can make a big difference. "A holographic optical element is a thin sheet of photosensitive material -- think photographic film -- that can replicate the functions of one or more additional optical components," said Jackin. "They aren't bulky or heavy, and can be adapted into smaller form factors. Fabricating them emerged as a new challenge for us here, but we've developed a solution."

Recording, or fabricating, a hologram that can replicate the function of a glass-made optical component requires that particular optical component to be physically present during the recording process. This recording is an analogue process that relies on lasers and recording film; no digital signals or information are used.