Liquid Crystal on Silicone (LCOS, D-ILA or SXRD)

Technology Overview & Description

LCOS technology is a reflective type of LCD that delivers a greater amount of light than a transmissive LCD panel and is comprised of groups of pixels which correspond to each image dot. Also, unlike conventional LCD panels (in which the switches and electronics are mounted on the same surface as the pixels), the LCOS' driving IC substrate is located behind the liquid crystal layer. Because of this, the "screen door effect" found in many LCD projectors is eliminated almost entirely, leaving a nearly-seamless picture which is very impressive. LCOS and DLP will continue to battle it out for the next several years, though we see DLP truly gaining a foothold in the market while LCOS remains on the outskirts, somewhat targeted towards the high-end consumer.

Editor's Note: LCOS is presented by many different manufacturers as their own. For example, D-ILA is essentially JVC's flavor of LCOS and is presented here due, in part, to the significant differences between LCOS front projection and rear projection solutions and applications. D-ILA also particularly impressed us at CES 2005 and we feel it has a tremendous potential for home theater markets once higher yield versions of the light valve are possible. Sony is also utilizing LCOS technology in it line of "SXRD-branded" products.

The LCOS technology is based on an innovation in microchip design that packs 2048 x 1536 pixels on a single 1.3" chip (labeled a QXGA device). Keep in mind that with all of the flavors and versions of LCOS-type technology the resolutions vary more than I care to include here. This makes possible display of HD images at full-spec resolution of 1920 x 1080 (with support for 1080p possible). Overall, LCOS projectors produce higher resolutions, better contrast ratios, less image artifacts, and better tonal and color information than just about any LCD front projection device.

How it works

The light from the xenon lamp travels through a polarizing beam splitter (PBS), which is reflected off the LCOS device, then passed through the projection lens and onto the screen. High brightness and high resolution are achieved using a reflective LCOS device with a high aperture ratio (93%) and high-density pixels, providing real resolution with pixels that blend almost seamlessly together. High contrast is achieved using vertical alignment liquid crystals of normally black operation and a high-precision optical system. Analogue gradation makes it possible to reproduce dark areas with high S/N (signal-to-noise ratio) because the LCOS device has an S-shape response. In combination with the high-speed response of the vertical alignment liquid crystal, LCOS technology makes it possible to reproduce smooth, noiseless motion pictures with clear, sharp high definition and film-like picture quality.

What's Next

JVC just announced July shipment of the next-generation of D-ILA products containing their new 0.7" chip (1920 x 1080) which is designed to take advantage of higher yields (and lower costs) while offering true 1080p HD resolution. Screen sizes include 56-, 61-, and 70-inch models. Sony is constantly dazzling people with its new SXRD line of products which continue to look fantastic so far and Syntax-Brillian is pushing new 1080p models out the door as fast as it can. This should create much needed competition for next-generation LCD and DLP projectors if they can get manufacturing costs down and feed more of these units to consumers. Right now the contrast ratios on these projectors is greater than LCD, but continue to be less than even single-chip DLP projectors. LCD technology, be it reflective or transmissive has a long way to go to gain significant ground in this one area, but its unique characteristics put it somewhat into a class of its own.

LCOS Projection Advantages

• Excellent color reproduction
• Excellent contrast ratios
• Nearly seamless images

LCOS Projection Disadvantages

• Still expensive despite more acceptance
• Currently geared towards high-end home theater and commercial uses

JVC D-ILA Projector (left); Brillian 6501mb LCoS TV (right)