Quarter-wave retarding film could enable simpler 3D large-screen displays

August 21, 2012 – BUSINESS WIRE — Various techniques create the illusion of depth in 3D movies, often relying on glasses for the viewer and a cumbersome 2-projector method. Researchers at South Korea’s Seoul National University have developed a quarter-wave retarding film that changes light polarization, applied to the display screen as a specialized coating.

With further research, the film could enable “a simple, compact, and cost-effective approach to producing widely available 3D cinema, while also eliminating the need for wearing polarizing glasses,” said lead researcher Byoungho Lee, professor at the School of Electrical Engineering, Seoul National University in South Korea.

To create modern 3D effects, movie theaters use linearly or circularly polarized light. In this technique, two projectors display two similar images, which are slightly offset, simultaneously on a single screen. Each projector allows only one state of polarized light to pass through its lens. Polarized glasses cause each eye to perceive only one of the offset images, creating the depth cues that the brain interprets as three dimensions.

Various single projector methods achieve similar effects. The parallax barrier method creates the illusion of 3D with a combination of rear projection video and physical barriers or optics between the screen and the viewer. These obstructions are likened to the slats in a venetian blind, creating a 3D effect by limiting the image each eye sees.

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The South Korean team’s glasses-free 3D method uses a single front projector against a screen. The venetian blinds’ “slat” effect is achieved by using polarizers that stop the passage of light after it reflects off the screen. A specialized coating, quarter-wave retarding film, was added to the screen to change the polarization state of light so it can no longer pass through the polarizers. As the light passes back either through or between the polarizing slates, the offset effect is created, producing the depth cues that give a convincing 3D effect to the viewer.

Figure. The experimental set up of a proposed glasses-free 3D theater experience is shown, with the projector in the familiar front position, creating 3D images. Credit: Optics Express.

The team’s experimental results show the method can be used successfully in two types of 3D displays: the parallax barrier method, described above, which uses a device placed in front of a screen enabling each eye to see slightly different, offset images and integral imaging, which uses a two-dimensional array of many small lenses or holes to create 3D effects.

The team plans to refine the method, and apply it to developing other single-projector, frontal methods of 3D display, incorporating passive polarization-activated lens arrays and the lenticular lens approach.

While their experimental results are promising, it may be several years until this technology can be effectively deployed in movie theaters.

The technique is described in the Optical Society’s (OSA) open-access journal Optics Express. Paper: “A frontal projection-type three-dimensional display,” Optics Express, Vol. 20, Issue 18, pp. 20130-20138 (2012).Optics Express reports on new developments in all fields of optical science and technology every two weeks, published by the Optical Society and edited by C. Martijn de Sterke of the University of Sydney. Optics Express is an open-access journal and is available at no cost to readers online at http://www.OpticsInfoBase.org/OE.

The Optical Society (OSA) brings together the global optics community through its programs and initiatives. For more information, visit www.osa.org.

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