Articles and whitepapers

3LCD Technology - Get the full picture (3/3/2005)

By Stuart Davis, Epson UK

Achieving the reality of a cinema in your own home is far easier today than ever before thanks to leading-edge technology in the latest home cinema projectors. These make large-screen viewing both reliable and affordable, whilst also being flexible enough to fit into your home without the room to having to be redesigned. Whether you want to permanently ceiling-mount the projector, or simply bring it out and place on a coffee table, then pack it away, the choice is yours. This flexibility, along with the large achievable screen sizes up to 60" and above, has led to a rapid expansion in demand, which is expected to continue. Volume sales are forecast to increase tenfold between 2003 and 2007.

Projector technology

There are three different technologies used in projector devices:
LCD (Liquid Crystal Diode) or High Temperature Poly Silicon (HTPS).
DLP (Digital Light Processing), which uses Digital Micro Mirror (DMD)devices.
LCOS (Liquid Crystal on Silicon).

LCD and LCOS systems are three-channel devices, i.e. their optical engines contain three imaging devices, one each dedicated to red, green and blue image generation. LCOS projectors tend to be more expensive and in a more specialised category than their LCD counterparts and, whilst there are three-chip DLP products available, it is the single-chip DLP devices which are more comparable from a price/performance point of view. These devices use one DMD combined with a colour wheel which splits the white light from the lamp into red, green and blue light, or sometimes white and other colours depending on the exact specification. This results in sequential projection of the image colours rather than simultaneous, full-colour imaging as achieved by LCD and LCOS devices.

Of the three main technologies, the most widely used is three-panel LCD (3LCD), with approximately 70% of the world's share for front projectors in 2003 (Source: DTC). Epson has spent considerable resources on developing 3LCD technology over the years, including recently 35 billion yen (around US$300 million) on a new plant at Chitose in Japan. As a result, Epson manufactures the majority of LCD panels used in projector manufacture worldwide.

Ultra-high-resolution small LCD panels

3LCD technology

The 3LCD system was developed to meet the demand for small panels that could produce bright, high-resolution images on large screens. In the 1980s, when only single-chip amorphous-Si TFT was used in projection systems, it was difficult to produce displays with resolutions above VGA (680 x 480 pixels) or with enough brightness when used in presentations. 3LCD systems came to dominate the market as they were able to produce higher resolutions and increased brightness. Since the launch of the first LCD data projector in 1994, each generation of panel technology has resulted in better image quality by increasing resolution, improving geometry of pixels, and reducing inter-pixel spacing. By reducing the space between the two glass substrates of the LCD panel, image contrast and response times have also been improved.

DLP and other systems followed, but 3LCD still continues to dominate due to its bright, natural images, smooth video playback and gentleness on the eyes.

3LCD projectors divide the light emitted from the lamp into the three basic colours of red (R), green (G) and blue (B), and then shine each colour light through separate HTPS-type liquid crystal panels that give shape and movement to the final image on the screen. 3LCD technology uses light extremely efficiently, resulting in bright images and low power consumption.

(from right to left) 3LCD mechanism for colour reproduction

Core benefits of 3LCD for home cinema use

Home cinema users are always on the lookout for the ultimate in image quality and projector performance, and 3LCD technology has inherent advantages for home cinema use. The three-channel system gives brighter more energy-efficient performance - business products are available producing 5000 ANSI lumens and above, whereas for home cinema, 800 to 1000 ANSI lumens is generally considered maximum. Home cinema products are designed to give very good contrast and colour reproduction performance in subdued or completely dark conditions - as low as 300 to 400 ANSI lumens can be more than sufficient in complete darkness. Indeed too much brightness in such conditions is painful on the eye and makes achieving deep black levels and good colorimetry more difficult.

3LCD technology also offers more realistic and better saturated colours so that film scenes are accurately reproduced as the director intended. 12-bit processing makes some 3LCD products capable of producing up to 68.7 billion colours, and reds, oranges and greens are produced more vividly and with better accuracy. In addition, the efficient use of light gives quiet and cool operation with rapid shut down after use.

Because the LCD panels used are analogue, they produce smooth gradations and a broad range of neutral grey tones. There is no noticeable 'stepping' or image dithering - important for sky scenes or flesh tones. With a superior bit depth, 3LCD products are able to show incredible detail - one of the latest 3LCD based front projectors is capable of up to 10 quintillion shades of grey.

As a three-channel system, 3LCD does not perform sequential projection but produces full colour images with no colour break-up or rainbow effect. Overall, images are more balanced between white and colour content, making them less harsh on the eye. 3LCD products also feature highly-competitive contrast ratios, with many models are already capable of a contrast ratio over 1000:1, with ratios of 6000:1 having been recently introduced. Also already available are LCD panels which are capable of showing 1080p sources at their native resolution, ensuring that 3LCD technology is able to keep pace with the latest HDTV transmissions as soon as they commence.

Costs

In terms of pricing, costs range from around GB£700 for a 1200 ANSI lumen W-VGA (widescreen with resolution of 854 x 480) 16:9 resolution projector, with 800:1 contrast and component inputs, such as the Epson TW10H, to around GB£2500 for the Epson TW500, which offers 1000 ANSI lumens, W-XGA (widescreen with resolution of 1280 x 720) 16:9 resolution, 1200:1 contrast ratio, component and HDMI digital inputs, horizontal and vertical lens shift, and powered zoom and focus. Indeed all Epson TW products have variable power supplies to allow lower brightness, higher contrast modes for best home cinema performance.

Epson EMP-TW200H, mid-range home cinema projector

Conclusion

3LCD is the dominant microdisplay technology worldwide, and it continues to grow at a rapid pace. The explosive popularity of high-resolution digital video formats such as DVD and HDTV, along with a steady increase in projection-based business applications, have contributed to a massive surge in demand for front projectors and large-screen televisions. 3LCD technology offers high quality images at affordable prices, ensuring development of products that are meeting the demands of the growing home cinema projector market.

Stuart Davis is the Business Manager, Projectors, for Epson UK. The Epson Group's main product lines comprise information-related equipment such as printers and projectors, electronic devices including displays, liquid crystal panels for projectors, semiconductors and quartz devices, and precision products such as watches.

www.epson.co.uk