FEATURE
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The big picture

Lasers are making the leap from the laboratory to the consumer world, as Rob Coppinger discovers

Beyond the obvious success of photonic technology in CD and BluRay players, the creeping of lasers into the world of entertainment has been largely limited to laser light displays. However, applications in other areas are emerging, including the use of laser technology to deliver huge, high-definition video in shops, the next generation in interactive console gaming and ever-larger home cinema screens.

Mitsubishi’s Laservue televisions were announced in January 2008 and use a laser for the rear projection system, which the company claims provides double the range of colours of existing televisions. In October of 2008 Mitsubishi had the retail launch for its first Laservue model, a 65-inch screen that had a $6,999 price tag. It was a 10-inch thick rear-projection television and has a power consumption of 135W. Last year Mitsubishi launched a 75-inch screen version, which is 15-inches deep and has a power consumption of 128W. The 3D capable television is cheaper than its smaller predecessor at $5,999. The 75-inch model consumes 0.05W per square-inch of viewing area. Mitsubishi points out that with an operating power under 200W the Laservue televisions are ‘consuming approximately half the power of today’s LCD TVs, and one third of plasma TVs.’

Mitsubishi Digital Electronics America vice president consumer product sales Frank DeMartin says: ‘As a result of our majority share of the worldwide high-performance red laser market, Mitsubishi has an unparalleled, acute understanding of laser technology, and the corresponding expertise to engineer laser beams effectively to function as the ultimate light engine.’

But if a 75-inch screen is not big enough, then there is the modular Laser Phosphor Display (LPD) technology that can build up huge wall screens for shopping malls or public events using its 25-inch diagonal tiles. Produced by San Jose, California based-Prysm, it has patented its LPD technology that uses a laser engine, laser processor and a phosphor panel to create the wide images. But this technology will not only be for the public arena. ‘The technology was created primarily for use as professional displays... to create large format displays,’ says Steve Scorse, Prysm Europe, Middle East and Africa vice president. ‘There are plans to introduce a consumer model at a later date in the product’s lifecycle.’

Fitting tiles

At the core of the Prysm LPD platform is the 25-inch diagonal tile called TD1. Prysm uses a modulated solid-state laser diode emitting a 405nm wavelength beam to deliver the images by energising the phosphor tile’s panel. Viewers can see the images while standing at angles of up to 178° from the screen. Each TD1 tile weighs 26.3kg and is 15 inches high by 20 inches wide. For the laser system the tile’s depth is 14.6 inches. Scorse explained: ‘Each of Prysm’s TD1 tiles is a complete product, so the distance of the lasers to the screen always remains the same [however many tiles you put together]. This is much less depth than traditional projection and LED.’

To completely cover the display area the beams are directed by mirrors that achieve a refresh rate of 240Hz. The higher the rate at which the screen is refreshed the smoother the image. High-definition televisions today have refresh rates starting at 60Hz and can be 120Hz for those that show 3D but 240Hz is not common.

Each panel has a life of 60,000 hours, which is 6.8 years of continuous operation. According to Prysm it is the laser processor that increases the display’s lifespan and lowers power consumption by managing the laser engine, turning it on and off and varying its intensity.

The video inputs to this laser engine are Component, VGA and DVI-D and HDMI, both of which are HDCP-compliant. Plugged into the mains, the average power consumption per tile is 30W, its Watts per square metre consumption is 155W, and its standby consumption is 7W. Prysm claims that the system uses up to 75 per cent less power than traditional backlit or projection technology-based products.

The LDP technology is capable of showing 4K, the high definition standard that will follow 1080P. The 4K refers to the number of vertical lines of pixel, so the screen resolution is 4,096 vertical lines x 2,160 horizontal lines. With 1080 it is 1,200 vertical lines x 1,080 horizontal lines and the P stands for progressive, which is how the lines are scanned. With 1080P, viewers get a picture made of 2.1 Megapixels while 4K will deliver 8.85 Megapixels.

Size isn’t everything

At the other end of the size spectrum is the pico projector. According to a market survey by Display Search, pico projectors could be selling more than 100 million units by 2017. In a market dominated by LEDs, the laser version is viewed as a way of delivering larger more vivid projections with less power leading to a much longer battery life.

Pico projectors incorporating red, green and blue lasers, with very low numerical apertures, can be miniaturised into a format that can be embedded into smart phones. Although red and blue diode lasers are readily available, obtaining a low-cost and efficient green laser is a challenge.

Covesion is a UK manufacturer of periodically poled lithium niobate (PPLN). With an exceptionally high non-linearity, PPLN is able to efficiently convert a low cost 1064nm NIR source into green light. Such lasers are based on the low-cost platform that green laser pointers utilise, but are able to offer three times the efficiency using a crystal of less than 1mm in length.

Companies such as Spectralus and Panasonic are now making PPLN-based green lasers and laser projectors in preparation for volume supply starting in the first quarter 2012. These projectors are likely to be in the 50 to 100 Lumens range, much brighter than their battery-powered LED counterparts.

Lumens is the unit for luminous flux which is the radiant power of the light that reaches the human eye, combined with the known sensitivity of the eye. Covesion’s managing director Mark Middleton says that, with laser pico projectors, ‘you get the same battery lifetime for more than twice the brightness, the colours are much more lifelike, and the picture is always in focus.’

For Middleton, the market-winning brightness is in excess of 50 Lumens. With 50 Lumens Middleton explains that a display can be more than 40-inches across and would be clearly visible in a normally lit room.

Middleton expects that by using PPLN to produce green laser light, the cost of a 50 Lumen pico-projector light engine could be well below $100, meeting the price-point for a wide range of markets and embedded applications.

The pico-projector market is split between two light source configurations: MEMS scanning and Liquid crystal on silicon, DLP field imaging. US company Microvision is utilising a scanning mirror to efficiently rastor a collimated beam of laser light rapidly across the projected area – similar to how a CRT TV operates. This approach minimises the number of optical components required, however increasing brightness to over 20 Lumens could have laser safety implications. Conversely, using an LCOS, DLP field-imaging approach utilises diverging beams of light, maintaining their eye-safe standard to well beyond 250 Lumens – more than enough for any hand-held device.

Whether it is a Laservue television, LPD screen or a pico projector the method of control is always a keypad or remote control, but lasers could be about to make that history. Gesture recognition (GR) that uses lasers for body, limb and hand movement detection has found its first application in gaming.

Popularised to date by Microsoft’s Xbox Kinect, GR console control removes the need for the traditional video game console paddle or Nintendo Wii-like wand. With GR there is no controller of any type, it is the detection and interpretation of a player’s body movements that direct the in-game action.

Kinect uses infrared light detection to see its user, and Israeli company Primesense provides the motion sensor that does it. JDSU, a California-based optical products and test and measurement solutions company, provides Primesense with the laser diodes.

The laser diodes it provides Primesense with are Gallium Arsenide. ‘We chose it for the wavelength; the light needs to be invisible to the player,’ says JDSU’s product line management senior manager Andre Wong. As well as the near IR laser diodes that, Wong says, operate ‘at about 830nm’ JDSU provides optical filters for the receivers that detect the reflected IR light.

Wong says more than one gaming console maker has bought his company’s technology and that there is interest from television makers.

The interest for television is the use of a GR remote control function that is akin to the multi-touch experience people have with smartphones. Waving their arms in the air users will be able to swipe, pinch and zoom the TV menu screen just as they do with their phones. But Wong is not expecting this ‘smart TV’ until later in this decade ‘once they come out with more powerful [television] processors’.

For JDSU the industrial market is more familiar while consumer technology offers bigger profits. But the reliability has to be very high. Wong compares it to the high standards they have to meet for their products that are used underwater. Because of the demands of the consumer market with its annual product refreshes and launches Wong says: ‘We do feel we have to do a lot of development of the lasers. The consumer market is much faster, products can change in the course of a year. Once you have a design in a consumer product the returns can be much higher’.

All these developments mean only one thing: the next time Hollywood or a computer game publisher has aliens invading earth, their heat rays will be seen and fought against on a screen that is not only illuminated by the very technology H G Wells predicted in The War of the Worlds, but controlled with it.