“The privacy-enhanced computer display uses a ferroelectric shutter glasses and a special device driver to produce a computer display which can be read only by the desired recipient, and not by an onlooker. […] The ferroelectric shutter glasses allow only the desired information to be viewed, while the inverse image causes unauthorized viewers to perceive only a flickering gray image […]. It is also possible to use the system to “underlay” a private message on a public display system.”
Good Noodles.