Clunky glasses that we wear to achieve a convincing 3-D effect of latest Hollywood blockbusters may soon be a thing of the past.
New optics research by a team of South Korean investigators offers the prospect of glasses-free, 3-D display technology for commercial theatres.
Their new technique can bring this added dimension while using space more efficiently and at a lower cost than current 3-D projection technology.
To create modern 3-D 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. By donning the familiar polarized glasses, each eye perceives only one of the offset images, creating the depth cues that the brain interprets as three dimensions.
The two-projector method, however, is cumbersome, so optical engineers have developed various single projector methods to achieve similar effects. The parallax barrier method, for example, succeeds in creating the illusion of 3-D, but it is cumbersome as well, as it requires a combination of rear projection video and physical barriers or optics between the screen and the viewer. Think of these obstructions as the slats in a venetian blind, which create a 3-D effect by limiting the image each eye sees.
The South Korean team has developed a new way to achieve the same glasses-free experience while using a single front projector against a screen.
In their system, the Venetian blinds' "slat" effect is achieved by using polarizers, which stop the passage of light after it reflects off the screen. To block the necessary portion of light, the researchers added a specialized coating to the screen known as a quarter-wave retarding film. This film changes 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 3-D effect to the viewer, without the need for glasses.
The team's experimental results show the method can be used successfully in two types of 3-D displays. The first is 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. The other projection method is integral imaging, which uses a two-dimensional array of many small lenses or holes to create 3-D effects.
"Our results confirm the feasibility of this approach, and we believe that this proposed method may be useful for developing the next generation of a glasses-free projection-type 3-D display for commercial theaters," noted the team's lead researcher Byoungho Lee, professor at the School of Electrical Engineering, Seoul National University in South Korea.
Their new technique has been described in a paper published in the Optical Society's (OSA) open-access journal Optics Express. (ANI)