Big-screen debut

A large, wedge-shaped monitor and a pocket-sized projector are set to cut the cost of home cinema.

While cheap DVD players enable most of us to enjoy digital-quality films, the high cost of large, flat television screens has kept the complete home-cinema experience out of reach for most consumers.

But UK company Cambridge Flat Projection Displays hopes to change this with a 20mm-thick 50in screen that could cost a fraction of today’s state-of-the-art large-screen TVs.

The company is negotiating with Far East manufacturers to bring the screen into mass production, and expects to have something on the market by 2007.

Dr. Adrian Travis, who heads the Cambridge University spin-off venture, said his company’s display system uses a conventional digital projector to project an image into the edge of a wedge-shaped plexiglass panel.

Through the optical phenomenon of internal reflection, this light bounces backwards and forwards up the length of the wedge. As it does so the angle of reflection gets progressively smaller and smaller until the critical angle at which rays undergo total internal reflection is reached. At this point the light emerges as a crystal-clear image on the front of the screen.

Travis said that while the wedge screen offers equivalent performance to today’s plasma and LCD screens, its lack of electronic components means that it is around half the price. The screen can also be designed to be around 1mm thick, a considerable improvement on existing bulky rear-projection screens, where an image is projected and reflected on to the screen from behind.

The price gap between wedge technology and big LCDs may become even wider as Moore’s Law (that transistor density doubles every 18 months) continues to hold true.

‘Projectors are full of silicon chips, so they follow Moore’s Law and fall in price by about three per cent per month,’ said Travis. ‘Big LCDs don’t do that, so the gap between LCDs and rear projection will widen.’

The largest plasma and LCD screens currently retail for around £3,000.

He added that while existing versions of the screen are designed to be used with a standard off-the-shelf projector, in future the projector could be packaged into a single device.

While most of the company’s efforts are focused on getting the existing screen onto the market, Travis also has an eye on future applications. The firm believes it should be able to make 100in screens, and is investigating the possibility of making plastic wedge displays that can be rolled up and coupled with the type of pocket-sized laser projectors currently under development. The team has even looked into using the system in reverse, as a camera in video conferencing applications.

Meanwhile, the company is concentrating on the product it feels is nearest to being marketed: television for homes. ‘At the moment we’re about making money so we have to stick with what exists and the kind of projectors you can buy off the shelf,’ said Travis.

<b>… and a laser show in your pocket</b>

Projectors the size of a cigarette packet are in development that could be used for everything from impromptu slideshows to downloading and watching the latest blockbuster on your living room wall may knock the iPod from the gadget-lovers top spot.

A team at Germany’s Fraunhofer Institute for Silicon Technology is developing a ‘vest-pocket beamer’ – a portable projector that can be used to display video, text and images onto any available surface.

The device is based on a tilting 1.5mm diameter micro-mirror that builds up a picture pixel by pixel, by rapidly switching its angle and deflecting a laser beam. Each time the mirror is moved, springs pull it back to its original position so quickly that the movement can be repeated, in different directions, several thousand times per second.

Ulrich Hofmann, head of the Fraunhofer team, said the high power demands of existing laser systems make the demonstrator too bulky to be commercialised yet. Also, the only available laser diodes of sufficient durability and brightness all emit red light. But with technology developing quickly, he claimed that a suitable laser source could become available next year, making the first products possible.

Hofmann said the initial devices could be low-cost ‘beamers’ that could, for instance, be used to show slides. But he revealed that he is also working with an unnamed manufacturer to develop a video projector for mobile phones.

A UK team is using a different approach to develop tiny projectors. The ‘holographic video projector’, developed by Cambridge University spin-off company Light Blue Optics, uses lasers and holograms to project an image.

The device creates a holographic pattern on a small liquid-crystal-on-silicon (LCOS) microdisplay. This pattern is then illuminated using a laser, and the light is diffracted to produce a high-quality image for projection onto a screen or wall.

The complexity of holograms has previously made them very slow to perform, but an innovative ‘hologram chip’ developed by the company enables the device to generate 200 frames a second (video films run at 50 frames a second).

Like its German competitors, the UK team is waiting for laser technology to improve, and is only able to produce images in one colour. But company founder Nic Lawrence said he expects to be able to build a full-colour device in the coming year.

He is in contact with a number of companies, including an aircraf developer that wants to use the technology in ‘head-up’ cockpit displays. The first product using the technology could be on the market in around 18 months’ time, he said.

Lawrence claimed that the cigarette-packet-sized device could do for movies what the iPod has done for music, leading to a ‘pocket- sized video projector that you plonk on the table and use to project a film onto the wall’.

While he did not rule out packaging the technology into mobile phones, Lawrence said that the pressures on size, power and costs would make this the toughest application of all.