LONDON — Two artists working in a converted church in London's East End have become the unlikely inventors of a holographic 3-D display that produces stunning images for a cost of little more than $5 over a conventional LCD. The design has already piqued the interest of companies such as Silicon Graphics Inc.

Working on less than a shoestring budget, Edwina Orr and David Trayner have patented what is arguably the world's best auto-stereoscopic three-dimensional display technology-one that doesn't require the viewer to wear special glasses.

RealityVision Ltd., the company the couple formed to exploit the technology, is preparing to go into limited volume manufacturing later this year. Under a development contract, RealityVision will scale the technology from its current 800 x 600-pixel resolution, achieved with a standard Toshiba color-LCD module, to 1,280 x 1,024 pixels using an LCD module from IBM Corp.

"A museum in Vienna wants to have 40 units next year," said Trayner. "What we're looking for are projects where people can afford to buy a few units." Orr said Silicon Graphics (Mountain View, Calif.) and other major computer companies have asked for evaluation units. RealityVision has also had discussions with companies on licensing the technology for volume applications.

Sculptors with master's degrees from the Royal College of Art in London, Trayner and Orr over the past 20 years have become experts in holography, using it to make eye-popping large-scale images and for technical purposes such as archive recording.

At the same time they were refining the 3-D holographic display, the couple were busy renovating the once derelict church where they now live and work into a combined arts center, bar and restaurant. It's also headquarters for their fledgling company. They are RealityVision's sole employees.

"We've done this on a very low budget. And there were times when we thought we couldn't keep going," said Trayner.

The east London arts center, known as 291, is a breath-taking space. Orr painstakingly hand-painted whole sections of the ceiling-working, Michelangelo-like, atop a 50-foot-high scaffold, to bring them back to their former glory. (The name is not only a reference to the street address-291 Hackney Rd.-but also pays homage to photographer Alfred Stieglitz's famed 291 gallery, based at 291 Fifth Ave. in New York in the early years of this century.)

The space is used regularly to display art videos and to stage performances. And now its back-room baby-the 3-D color display technology-looks to be on the verge of becoming a commercial reality.

RealityVision has demonstrated and refined the technology over the last couple of years. Trayner and Orr believe that in future systems the 3-D effect could even be presented to several people at once, contrived to follow a moving observer. The display is easier to view than other 3-D display systems and avoids the left-right image reversal possible with established parallax methods, the company claims.

But among its biggest advantages, according to Trayner, is that the display is compatible with conventional 2-D LCD viewing. The 3-D effect is achieved by adding low-cost holographic optics to a conventional LCD module. This means you can turn it off to allow normal viewing of 2-D files, then switch it back on to make use of 3-D effects in appropriately prepared 3-D files for such applications as computer-aided design, medical imaging and keyhole surgery support, cartography and computer games.

How it works
To create a 3-D image, the left and right eyes must see slightly different images. Existing auto-stereoscopic 3-D screens use a series of fine vertical bars or lenses to direct the two images correctly to each eye. But according to Trayner, this reduces the 3-D viewing angle, the horizontal resolution and how convincing the depth of the image looks.

RealityVision's technology solves these problems by using a standard full-color LCD panel and substituting the conventional backlight with a point light source, a Fresnel lens and a horizontally striped holographic optical element (HOE).

One set of HOE stripes aligns with the odd lines of pixels on the LCD, illuminating them for one eye but not the other. Similarly, the second set of HOE stripes-equivalent to the even lines of pixels on the LCD-illuminates these for the second eye but the not the first. Using software to interlace the pair of stereo images on odd and even lines of the display produces the 3-D effect. The only limitation is that the viewer's head must stay more or less directly in front of the screen.

Trayner said that head-tracking technology and appropriate optics could be used to move the stereo viewing position in response to the viewer's head movement. At the same time, software could be used to access and display appropriate image pairs to give the effect of looking around an object.

The display switches to 2-D by sending the same image to both the odd and even lines of the LCD, or by switching to a conventional LCD backlight and sending a conventional image to the screen.

A demonstration system comprising a Toshiba 800 x 600-pixel industrial color-LCD module in a special light-box housing driven from an Apple PowerPC 7500/100 computer works very well indeed.

Trayner uses it to show a specially prepared 3-D graphics file in which a colored-ball model of the DNA double helix seems to hover in front of the screen. Another file shows a 3-D model of the bones and tendons of the human foot. The computer's mouse can be used to grab the image and rotate it so that it can be viewed from all angles.

The demo also shows a tape-recorded video in which Orr demonstrates the 3-D effect by thrusting her hands out of the screen toward the viewer.

The display can even show live video shot with a pair of JVC miniature surveillance cameras carefully bolted together eye-distance apart on a single tripod. The two video data streams are interleaved field-sequentially before being processed within the computer and sent to the LCD- and there is Trayner, almost as tangible on screen as he is across the room in front of the cameras.

The current RealityVision demonstrator uses an HOE made using silver-halide holography and wet photochemical processing. Although so far the HOEs have been hand-made, material costs could be as low as $5 per display, according to Trayner and Orr. For mass production they recommend either surface-relief holograms, the sort used for security printing on credit cards, or holographic photopolymer, which could reduce costs still further.

"There's virtually zero additional cost for our 3-D display," said Trayner.

The light source is an 18-W metal-halide lamp. The main problem here is that the lamp is too bright, and about 95 percent of the output needs to be discarded to make the display dim enough to view comfortably. RealityVision is looking for lower-voltage, lower-output lamps and investigating the use of other light sources, such as light-emitting diodes. "There's a lot of possibilities and trade-offs in how we do this," Trayner said.

While licensing the technology to established display manufacturers remains an option, Trayner believes it may be up to RealityVision to build the first commercial units and demonstrate their usefulness in a variety of applications.

In Trayner's view, one of the problems in technology licensing is that the value of licenses is nearly always calculated in relation to the size of the immediate available market-and for 3-D displays today, that's practically zero. "The Toshibas and Hitachis will only enter a market if the minimum volume is 10,000 units a month," said Trayner. "What needs to happen is a gradual expansion of the uses and the development of the supporting software.

"I think the parallels with stereo sound are notable," he continued. "That was introduced in low volumes as a sound effect in cinemas. It was only when the advantages became known that the music industry picked up on it. And then it had to be introduced so that it was backward-compatible with mono sound."