05 Aug 2003
Cellophane, the ubiquitous packing material, can also turn a laptop screen into a 3D display.
Keigo Iizuka from the University of Toronto in Canada has discovered that a 25-micron-thick sheet of cellophane can rotate the polarization of visible (400 to 700 nm) light, essentially functioning as a half-wave plate. Iizuka has exploited this property to convert an ordinary laptop screen into a three-dimensional display. (Review of Scientific Instruments 74 3636)
Iizuka is now exploring new applications that take advantage of the wide-wavelength band and low-cost of cellophane. “A large-size cellophane half-wave plate is playing an important role in a 3D television system that we are developing now in my laboratory,” he told Optics.org.
After coming up with the idea to make a 3D-laptop display using a half-wave plate, Iizuka faced the problem that commercially available components are generally designed to rotate the polarization of a specific wavelength and not broadband white light.
“I had been thinking about alternatives for quite some time,” said Iizuka. “I kept measuring the retardance of any birefringent material I could put my hands on. I even tried other materials such as polyethylene sandwich bags but, after repeated failures, I found cellophane to be the most satisfactory material for white light.”
To measure the retardance, Iizuka fired a linearly polarized helium-neon beam through a sheet of cellophane and used a rotating analyser to study the intensity of the emergent light.
“I measured the retardance of my cellophane sample to be 170.2 degrees, which is about 95% of the phase delay of an ideal half-wave plate,” said Iizuka. “These measured results are within acceptable limits for a number of applications that do not require a precise 180 degree phase delay.”
One such application is making a 3D-display, which relies on separating the images that the right and left eyes see. According to Iizuka, light from a laptop used during his experiments was polarized at 45 degrees. To separate the images, one half of the screen was covered in the cellophane half-wave plate to rotate the polarization by 90 degrees. By simply wearing a pair of glasses with orthogonally polarized lenses, the images that the right and left eyes see are separated giving a 3D effect.
Jacqueline Hewett is news reporter on Optics.org and Opto & Laser Europe magazine.