Researcher sees cellophane window to 3D

Professor Keigo Iizuka discovered that ordinary cellophane wrap can be used to turn a laptop computer screen into a 3D display.

Iizuka was searching for so-called half-wave plates, which rotate the polarization of light, and ultimately found that a certain brand of cellophane gift wrap beat out high-tech alternatives. "I tried every possible material that might have that half-wave plate function, and this was the best I could find," he said. "Ironically, it was the cheapest."

Iizuka estimated that the cellophane wrap he used was 3,500 times less expensive than specially made half-wave plates. The wrap cost him about $3 for a 1-by-2 meter roll.

His results were published in the August issue of Review of Scientific Instruments.

Three-dimensional displays can be useful for a range of purposes, such as playing video games and exploring models of molecular structure. Technology for 3D displays usually requires special goggles or altered input and is relatively expensive, Iizuka said. Electronics company Sharp has been working on 3D flat-panel displays that do not require goggles.

Iizuka's system is specific to LCD (liquid crystal display) screens, which emit polarized light--that is, light oscillating in a fixed direction.

Using Iizuka's method, a screen is divided in half, with each side portraying slightly different images, such as those from a stereoscopic camera. He covers half the screen with the cellophane to change its polarization. He then uses a pair of sunglasses that are differently polarized, so that the right eye can see light coming from the left half of the screen only, and the left eye can see light from the right half of the screen only.

The mind blends the resulting images to create the sensation of a single image with three dimensions. Our sense of depth comes from slightly different images hitting each of our eyes.

Iizuka said cellophane is a good choice, partly because it rotates the polarization of the entire visible spectrum of light, unlike commercial half-wave plates that target a specific wavelength. But a cellophane thickness of 25 microns is key, he said, as well as the chemical composition of the cellophane, a petroleum byproduct that can vary in makeup by brands. Iizuka found that a particular product sold by crafts company Lewiscraft best fit the bill.

Iizuka's quest for a 3D display is driven partly by a desire to help the deaf. Sign language transmitted over the Internet would be more effective if viewers could better see the depth of the hand position, he said.

Iizuka also is interested in creating 3D displays for mobile phones.