Inside-out images secure screens

Computer displays are not particularly secure. Anyone with a clear view can glean information by glancing at a screen.

A researcher from Marmara University in Turkey has addressed the problem by devising a screen that can only be seen by a user wearing special glasses or standing at a precise angle to the screen.

The method could be used to secure computer displays that appear in public places, like those used in automatic teller machines.

Displays generally work by displaying a sequence of images, or frames. The researcher's scheme displays an inverse frame immediately after each original frame is displayed. Given the right timing, the human eye averages the two frames and sees it as a blank, gray image.

A user wearing LCD shutter glasses synchronized to block out the inverse frames, however, can see the content. A larger LCD shutter glass placed near the eye level of the legitimate user can accomplish the same thing. The method is similar to a common approach to displaying three-dimensional images.

The challenge was finding a way to quickly calculate inverse images that completely block the original images, according to Marmara associate professor Murat Dogruel. The method is fast enough to work on personal computers that contain a special display card, he said.

Practical displays could be built in two to five years, according to Dogruel. The work appeared in the October 3, 2003 issue of Displays.