Cellophane and 3D Displays

New research on ordinary cellophane shows that it can be used to convert a laptop screen image into a seemingly three-dimensional display. Cellophane is birefringent: its index of refraction is not the same in all directions in the material. This means that the polarization of an entering light wave can be rotated. Keigo Iizuka's lab at the University of Toronto verified that a cellophane sample 25 microns thick was better at rotating the polarization direction of white light than a commercially available device (called a half-waveplate) designed for a specific wavelength. Taking advantage of the fact that light emitted from a laptop display is naturally polarized to begin with, a 3D stereoscopic effect can be achieved by covering half the screen with a cellophane sheet in order to construct orthogonally polarized left and right scenes while the viewer wears eyeglasses holding two polarizers oriented 90 degrees apart (see series of figures). Actually, the crossed polarizers could be suspended between the screen and the observer, obviating the need for the viewer to wear the glasses. According to Iizuka (416-978-8657), this "cellography" method for producing 3D effects will be far cheaper than those using commercially available half-waveplates, and should be amenable to arcade gaming applications and for medical and scientific imaging applications. Iizuka is now at work on converting liquid crystal displays on cellular phones to 3D. (Keigo Iizuka, Review of Scientific Instruments, August 2003)