Brilliant colours?

Projection technology is riddled with acronyms, with competitive technology providers vying for the attention of both manufacturers and purchasers. But do you know your LCoS from your DLP or your 3LCD? Steve Montgomery explores the options.

Over the past ten years, projectors have become more and more prominent in business, educational and commercial environments to the point now, where they are more common than any other form of presentation system. No longer do we have overhead projectors in boardrooms and meeting rooms, nor do we have blackboards in schools. The reason, as ever is the falling price of the equipment, brought about to a great extend by the mass production and simplicity of projector light engines and associated electronics.

Nowadays, projectors are used in the smallest application, right up to the largest cinema installation, and covering every scale of use in between. For the smaller applications and for portable devices, single chip light devices provide compact, low power reasonably bright images, whilst for larger applications three chip devices offer greater brightness and contrast suited to high resolution electronic cinemas.

Texas Instruments manufacturers the Digital Light Projection (DLP), first developed in 1996 and currently used in over 15 million projectors supplied by 50 different manufacturers. John Reder, Texas Marketing Manager: “The DLP engine covers all sectors of the market, with a single chip device that allows manufacturers to build low power, portable devices for roughly 50% of the business and consumer applications, and a three chip set that delivers the ultimate in image quality. Right now, three chip DLP based projectors are used in 99% of top end electronic cinema installations, which has been a very rapid growth market for us. The largest e-cinema projector screens go head to head with first generation film prints and have been winning for several years. Ultimately this market will fall completely to electronic projection.” In the early days of DLP, the individual mirrors were easily apparent on the screen as individual pixels, together with a tiny black mark, which was the hinge used to move the mirror itself. Advancements in the manufacturing process have now resulted in much less obvious pixels and hinges, to the point now where the aperture ratio is well over 90%. Other advances in the number of segments and frequency of the colour wheel used in single chip engines has removed one of the original defects of rainbow effects on the image.

Recent developments in DLP technology have seen the launch of BrilliantColor; a system that adds additional primaries (yellow, cyan and magenta) to the normal red, green and blue primaries. John Reder: “BrilliantColor provides brighter, more saturated colours, allowing greater use of the full lamp spectrum which is particularly important in the penetration of DLP in the business projection market place where LCD has had an edge.”

One of the major advantages in DLP lies in the fact that it is a reflective technology: light is reflected off moving mirrors, rather than being absorbed or shut out of a transmissive element. This takes less power and requires less cooling, allowing projectors to be built that are smaller, lighter and cooler. Ideal for portable units and allowing large projectors of 15-20000 lumens to be manufactured and operated efficiently. Texas is currently developing ‘Picoprojectors’; projectors that are small enough to be built into small housings, even mobile phones and run from batteries, with next generation DVD players containing their own projection systems for use anywhere.

The rapid development in chip technology has led to an equally rapid rate of product launch. projectiondesign, a leading manufacturer of high specification projectors has operated since 2001 with product based on Texas DLP chips. The company’s latest products include the WUXGA (1920 x 1200) format devices. Anders Løkke, International Marketing & Communications Manager explains their philosophy: “very early on we made the decision to go with DLP and have stayed with that ever since. Customers are happy with the performance and it has allowed us to innovate in order to provide unique advantages in our range, primarily in the development of advanced optics and electronics that we fully develop ourselves, rather than simply buying in a third party’s assembly. In some applications, the colour display and saturation of LCD and LCoS have been seen as advantages over DLP, but that is all changing now with BrilliantColor, as that has strongly increased the all important secondary colour display, especially yellow.”

DLP is also used in rear projection cubes for video walls. Eric Henique, Director of International Sales and Marketing at Eyevis explains their advantages: “For 24 hour, 7 days per week operation DLP is better suited than LCD. It is a question of reliability and maintenance. DLP can cope with continuous operation requiring less environmental control and is not so prone to colour and mechanical drift which obviates the need for regular re-adjustment that we find in LCD in this type of application.”

The main competitor to DLP in volume and application is LCD. Another technology that has been expanding and developing for many years. Similar to DLP, LCD offers 3-chip technology with independent panels for each primary colour. 3LCD dominates the Pro AV market, comprising large schools, universities and high-end home theatre. “This year, more than 7 out of 10 projectors sold in the U.S. and Canada featured 3LCD technology, according to dealers in Pacific Media Associates' Pro AV Projector Tracking Service,” said Rina Bhuva, senior strategic marketing manager, 3LCD Technology. “It’s an incredible testament to the real-world performance of 3LCD projectors and shows that professionals who understand and are familiar with projector capabilities are overwhelmingly recommending that their customers choose 3LCD technology. We will continue to develop solutions that meet the exacting requirements of this important market.” 3LCD chips are able to display tonal response with up to 4,096 steps of greyscale providing a continuous and stepless gradation from black to white. LCD is generally recognised as producing more saturated colours than DLP, which is better received in the lucrative business market, although less so in the domestic environment. Additionally, LCD offers better light efficiency; at least on single chip equipment and slightly sharper images overall.

Hitachi manufactures a range of projectors based on 3LCD chips and have successfully combined this technology with their new ultra short throw lens design to achieve projectors capable of producing a 60 inch images from a 42 cm throw. Combined with adequate brightness levels of 2000-2500 lumens, they are ideally suited for whiteboard use for educational applications but are also targeted at standalone applications where short throw is a benefit.

A third technology used in projection is Liquid Crystal on Sapphire (LCoS). This is essentially a hybrid technology between DLP and LCD, which uses liquid crystal cells on a mirror substrate. Light is modulated as it passes through the cells, to be reflected by the mirror. This provides advantages over LCD and DLP in higher resolution, complete lack of visible pixels and smoother pixel edges which softens the edges of the pixels and allows them to blend together better. Above all, LCoS is an analogue system with continuous colour variation, which delivers an infinite colour spectrum and totally smooth images. Alan Dempster European Product Specialist at Canon: “ We have developed the XEED range as an affordable series of projectors using LCoS panels. The images are exceptionally smooth across the entire brightness range and seamless, resulting in fine details and text reproduction with outstanding clarity. An extension of the technology is AISYS, Aspectual Illumination System) a unique optical illumination system incorporating LCoS technology into a remarkably compact body. By optimising the light from the projector’s lamp in relation to the characteristics of the LCOS panels and PBSs (Polarization Beam Splitter), AISYS achieves a lightweight and compact chassis without compromising on brightness and contrast. ”Supplemented by automatic set up features, including focus, keystone and screen colour correction the projectors are suited to low cost applications in the business and commercial world and can deliver high contrast ratios of 1000:1 at high resolution; up to SXGA+ (1400 x 1050 pixels).

Because of the extremely smooth colour and brightness gradient, LCoS is particularly well suited to applications that demand highly accurate image rendition. Alan Dempster: “LCoS is penetrating the medical, photographic and simulation markets where it is essential for as much information about a source to be presented; as opposed to other applications in business where impact is more important. LCoS is ideal for monochrome applications, such as the viewing of X-ray films and in photography.”

What is certainly apparent from the advances in light engine technology is that the quality, price/performance and variety of product offerings from manufacturers can only benefit the installer and user to significant advantage. Reliability, flexibility and performance are reaching levels now that permit full ranges of projectors to be manufactured with a suitable device for every conceivable application.

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