Å®ÉúСÊÓƵ

A new kind of wall screen, which was recently heralded in British papers
as making ‘the TV set obsolete’, is part of a conflict over master patent
rights on a technology called ‘depixellation’. Two inventors, one British
and one American, say they devised the method used to make projected pictures
look better.

When normal TV pictures are projected onto a large screen, the gaps
between the horizontal scanning lines become too obvious. If the projector
uses a liquid-crystal display (LCD), its individual cells start to show
up.

William Johnson, a British inventor based in Hampshire, developed a
‘microlens’ system which disguises the lines and cells, and he recently
signed a development deal with the American company Nashua. His patent applications
(PCT 91/18304 and EP 294 122), filed internationally in May 1991, reveal
some details. A home cinema screen is covered with a transparent polymer,
etched or moulded into a honeycomb of tiny lenses. These are elongated sideways
into ovals, so the screen transmits light over a wide horizontal angle,
allowing viewers to watch from the side. The lenses also diffuse the image
slightly, disguising the pixels and lines.

In the US, Eugene Dolgoff of Projectavision has two patents (5 012 274
and 5 300 942) on depixellation and says its Taiwanese licensee, CMC Magnetics,
will start selling a projector under the MGM Home Theatre brand name this
year. Dolgoff’s work grew out of a $1 million contract awarded in 1989
by the Pentagon (Patents, 28 November 1992). In his system, light from the
LCD is passed through an array of microlenses to create several overlapping
replicas of each image, slightly offset to fill the gaps between cells.

The rival patents were filed on a series of overlapping dates. Projectavision
covers an LCD projector for use with any screen, while Johnson’s patent
covers a screen for use with any projector. Of Johnson’s claim, Dolgoff
says, ‘We predate him, and anyone using his technology would have to pay
Projectavision a royalty as well.’ Johnson says: ‘We predate Dolgoff,’ and
asserts that Dolgoff may have ‘misunderstood the meaning of the term depixellation’.