True videophiles know that their choice of HDTV sets the stage for everything else in their home theatre. Sophisticated viewers want to see movies in their home theatres the way the director intended with vivid colors from corner to corner, precision grayscale and dark black levels. There is an impressive array of display technology options available, especially in the evolving high-quality rear projection HDTV market that purport to satisfy the demands of home theatre owners. The three top rear projection display technologies are high temperature polysilicon (HTPS) liquid crystal displays (hereinafter referred to as Projection LCD), the single-source and proprietary reflective electro-mechanical technology called Digital Light Processing (DLP™), and the rapidly emerging top contender, liquid-crystal-on-silicon or LCOS technology. LCOS is an innovative reflective microdisplay architecture that combines semiconductor and liquid crystal display technologies to provide clear performance advantages in image clarity and quality, black level performance, response time, and accuracy of color rendition.
In LCOS technology, a liquid crystal layer is applied between a silicon mirror substrate and specially treated glass. The liquid crystal is controlled with electrical voltages so that light is either reflected or blocked in varying degrees to create grayscale. When combined with precisely colored light, generated from a lamp, the modulation of the liquid crystal material can create an unparalleled color gamut and striking image clarity. Since LCOS devices are fabricated on a silicon chip and operate in reflective mode, all of the control circuitry is â€œhidden” underneath the reflecting mirrors. As a result, LCOS provides a very smooth, non-pixelated image with no noticeable â€œscreen door” effect.
LCOS microdisplays are less than one-inch diagonal. When three microdisplays (one for red, green and blue) are incorporated to create a multi-megapixel light engine, they create a high-quality, high resolution image of up to 100 times or larger than the microdisplay itself. The densely packed pixels in LCOS multi-megapixel light engines deliver nearly seamless high-definition content by painting the pixels on the screen for all colors simultaneously. There are several versions of LCOS available today, but the state of the art is Brillian’s Gen II LCoS™ technology, which has industry-leading contrast levels, a film-like natural color palette, and nearly three-dimensional image depth.
Figure 1: Side View of LCOS microdisplay shows the layer of optical glass, liquid crystal layer, the highly reflective pixel mirror and the silicon backplane with the pixel control electronics.
Projection LCD Technology
Projection Liquid Crystal Displays (LCDs) use two layers of glass, with embedded row and column wires, and liquid crystal material in-between them. Pixels are created at the interconnection points of these row and column wires. Light passes through these LCD panels on the way to the lens and is modulated by the angle or position of the liquid crystals. In projection LCD TV light engines, three separate displays are also used: one for red, one for green and one for blue. The light is transmitted through these displays recombined in an optical cube and projected through a lens.
Because of the poor electro-optic efficiency of the glass sandwich, Projection LCD displays only provide moderate brightness, poor black levels, and suffer from slow video response times. This last feature is crucial in evaluating HDTVs because response time defines how fast liquid crystals move as they transition from one state to another. The response time of Brillian’s LCoS™ is twice as fast as standard nematic LCDs. Brillian’s 11-millisecond liquid crystal switching speed eliminates the blurring in fast action scenes. Some Projection LCD manufacturers try to mitigate the slow-response problem by employing unique video processing techniques but the result is still often criticized for inducing other objectionable artifacts.
Figure 2 The fill factor or aperture ratio is the percentage of active pixel area used to present images to users. The higher the aperture ratio of the pixels, the better the HDTV image clarity. LCOS has smaller pixels than LCD and packs them more densely in the display. The result is a nearly seamless pixel array and image.
Finally, Projection LCD displays are manufactured with organic materials that degrade over time. Brillian Gen II LCoSTM displays are fabricated with inorganic materials that can tolerate the UV light much more successfully over time.
Micromirror Display or DLP™ Technology
A single-source and proprietary reflective technology, Digital Light Processing display (DLP™) technology uses tiny mirrors, one for each pixel, to reflect light similar to how light is reflected in LCOS technology. DLP, however, creates grayscale by tilting the mirrors â€” quickly back and forth in a complex timing sequenceâ€” to reflect more or less light. DLP gained rapid initial market momentum in large-format HDTVs, but the technology does have unique drawbacks. DLP light engines for HDTVs are characterized by a single-display architecture, with an electromechanical color wheel. The color wheel creates an irritating rainbow or color break up effect. Color break up is one of the main DLP defects that video reviewers criticize.
Most videophiles have long known that black level performance is a key parameter that distinguishes a good TV from a great TV. DLP has very good black level performance, but where it has problems is in subtle grayshade transition scenes. DLP often exhibits a displeasing â€œmottled” appearance in subtle gray shade or dark scenes because it crushes the colors in the steep parts of the gamma curve. Brillian’s Gen II LCoS™ technology provides a very dark, black level. Less than 0.25 cd/m2. Brillian achieves this through a proprietary liquid crystal mode that delivers on-screen contrast ratios of up to 2000:1 making it the best in the LCOS industry. Yet, because of its analog control of pixel grayscale, all of the details of the image are resolvable and images look more like film than digital pixels.
In summary, when compared to Gen II LCoS™, the two main alternative projection display technologies come up short. DLP is plagued by digital video artifacts including color break up, blotchy grayscale and crushed blacks, and LCD projection TVs have large visible pixels that can create an annoying screen door effect and slow video response times that can create blurred images. LCOS mitigates these problems and delivers the best overall combination of clarity, superior contrast, artifact-free motion content, plus reliable and durable performance.
The Perfect Picture is on Brillian’s HDTV
The architecture of an HDTV’s light engine or projection subsystem is as important in creating a true cinematic experience as the projection technology itself. Although LCOS microdisplay panels can be used in single- or three-panel light engine configurations, three-panel LCOS configurations deliver the most artifact-free image. Brillian’s three-panel light engine has three microdisplays, one dedicated to each color â€” red, green and blue. The Brillian three-panel light engine is similar to LCD light engines in that three imagers are used, but LCOS pixel density is much higher than LCD. Also, since Brillian has eliminated organic alignment materials in its displays, they withstand UV light exposure from the lamp over time much better than LCD displays can. Unlike DLP, the Brillian three panel light engine is solid state, and there are no electromechanical moving parts that create video artifacts or reliability problems.
Brillian’s 6501mB and 6501iB HDTVs offer intensely brilliant and sharp on-screen images in dark or light rooms. Its UltraContrast™ Gen II LCoS™ technology delivers contrast ratios of up to 2000:1. In addition, Brillian HDTVs include powerful video processing capabilities. For example, when upscaling low resolution content, such as standard definition 480i-based movies that were originally intended for a 4:3 TV, to a large screen, high resolution 65-inch 720p HDTV, it is paramount that the image quality on-screen be maintained. If not, you could see a soft, dull picture and on-screen images with a straight edge would have a jagged appearance. Brillian’s advanced format conversion technology ensures that you can connect virtually any device in any format and see pleasing images.
Brillian has incorporated state-of-the-art motion adaptive video processing technology that smoothes out the jagged images ensuring that a film-like appearance is delivered. While many LCD displays have problems maintaining color uniformity, Brillian’s patented color correction technology ensures that the high fidelity of colors is maintained from edge to edge, which is especially critical in computer applications with expansive monochrome images. Moreover, Brillian’s second generation LCoS™ provides a Gamma range that is exceptionally accurate to reproduce accurate flesh tones that look like real life.
Brillian’s powerful system software is adjustable, manageable, and upgradeable to meet the demands of general consumers, videophiles and Pro AV users. Controls are intuitive and easy to use from adjusting aspect ratios or selecting a pictureâ€“in-picture mode to sophisticated color temperature and gamma curve control. As a result, Brillian satisfies the most demanding videophile. All Brillian HDTV sets support RS232 and IR communication for use with home automation control systems and are certified for use with Creston or AMX home automation systems. Brillian HDTV sets are also software upgradeable so that as fast as new features are created they can be easily uploaded to the system by a technician.
Figure 3 Brillian 65-Inch 720P HDTV optimized for home theatre and built-in design environments. The innovative in-wall design delivers both flat-screen appearance and outstanding image quality.