» Liquid Crystal on Silicon (LCoS) Microdisplay Panels

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December 12, 2006

Liquid Crystal on Silicon (LCoS) Microdisplay Panels

LCoS technology is a native high resolution display technology capable of producing exceptional, flicker free (high refresh rates) video with no pixel definition as inherent with LCD, high contrast ratios, bright natural colors, and no possibility of plasma like “burn-in”.

Although relatively new in terms of market perception, LCoS has been around for over a decade with JVC having shipped professional quality LCoS projectors since 1998. Sony and Brillian began shipping LCoS technology in 2005. Currently there are a few prominent proprietary versions of LCoS technology consisting of JVC’s D-ILA (Direct Drive Image Light Amplifier) chip technology, Sony’s SXRD (Silicon X-tal Reflective Display) and Syntax-Brillian’s Gen II LCoS.

LCoS microdisplay panels are generally less than an inch in size. JVC ship 0.7 inch D-ILA chips with full 1920 x 1080 resolution allowing the display of a full HD 1080p input signal without scaling.

How LCoS Works

LCoS, upon which JVC D-ILA is based, is a combination of both the reflective approach of DLP (millions of actuated micro-mirrors on a chip reflect light required for the display) and the transmissive approach of LCD (millions of liquid crystals act as valves passing through light required for the display). In LCoS, liquid crystals are applied to a reflective mirror substrate with the polarization of liquid crystals being used for light transmission control and the mirror below reflecting the light or not as required for image display. The projection light’s path is from the front - through the liquid crystal layer - reflecting off the mirror substrate and passing through the liquid crystal layer a second time and onto the screen.

The physical configuration of a LCoS panel confers a number of advantages:

Control electronics are placed behind the mirror surface - where they do not block the light causing the pixel definition (screen door effect) inherent with LCD.
In LCD displays, liquid crystals need to be relatively thick to produce a high contrast ratio however, with LCoS, as light passes through the liquid crystal layer twice the liquid crystal layer can be kept thin but, still produce excellent contrast ratio.
As a flow-on effect, the thinner liquid crystal layer also improves response time - reducing the possibility of image smearing with quick onscreen motion.
With all control electronics behind the reflective substrate and not squeezed between liquid crystal pixels there is substantially more room for electronics to produce much higher screen resolutions.

Panel Configurations

LCoS microdisplays are generally of three-panel configuration for the three primary colors however, there are single panels designs. With the three-panel design each panel handles one primary color and the colors are merged optically. In single panel display configurations, colors are displayed sequentially with the human eye relied on to merge the colors. If the sequential display rate is not high enough color breakup can be perceived during image motion or the viewers eye movement. Although less expensive, higher-speed control electronics are required for single panel displays to process three colors for a panel instead of one.