Liquid crystal on silicon

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Liquid crystal on silicon (LCOS or LCoS) is a "micro-projection" or "micro-display" technology typically applied in projection televisions. It is a reflective technology similar to DLP projectors; however, it uses liquid crystals instead of individual mirrors. By way of comparison, LCD projectors use transmissive LCD chips, allowing light to pass through the liquid crystal. In LCoS, liquid crystals are applied directly to the surface of a silicon chip coated with an aluminized layer, with some type of passivation layer, which is highly reflective.

LCoS technology can produce much higher resolution images using highly advanced silicon technology than liquid crystal display and plasma display technologies, which makes it less expensive to implement in such devices as televisions.

At the 2004 CES, Intel announced plans for the large scale production of inexpensive LCoS chips for use in flat panel displays. These plans were cancelled in October 2004 [1]. Sony has made it to market [2] (December 2005) with the Sony-VPL-VW100 or "Ruby" projector, using SXRD, 3 LCoS chips each with a native resolution of 1080p (1920 X 1080), with a stated contrast ratio of 15,000 using a dynamic lens.

LCoS technology has the potential to enable the manufacture of big-screen high-definition televisions with very high picture quality at relatively low cost. LCoS, while conceptually straightforward, can be a difficult technology to master; a number of companies have dropped out of the LCoS business in recent years. Nonetheless, as of June 2006, proprietary methods for mass-producing LCoS developed, and at least three manufacturers now produce LCoS-based rear-projection televisions for the consumer market.

Commercial implementations of LCoS technology include Sony's SXRD (Silicon X-tal Reflective Display), Syntax-Brillian's Gen II LCoS, and JVC's D-ILA (Digital Direct Drive Image Light Amplifier). All three of these companies produce and market rear-projection televisions that use three-panel LCoS technology. The differing product names are due to Syntax-Brillian holding the copyright for the LCoS name. Sony and JVC also produce and market front-projection displays that use three LCoS panels. Another provider of third-party LCOS chips is a Novato-based firm, Spatialight. Direct-view LCoS devices such as the single-panel LED-illuminated devices made by Displaytech [3] are also used as electronic viewfinders for digital cameras. These devices are made using ferroelectric liquid crystals, which are inherently faster than other types of liquid crystals. MicroDisplay [4]produce single panel LCoS capable of producing true 1080p resolution with two million pixels on a display panel.

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[edit] Display system architectures

There are two broad categories of LCoS displays: three-panel and single-panel. In three-panel designs, there is one display chip per color, and the images are combined optically. In single-panel designs, one display chip shows the red, green, and blue components in succession with the observer's eyes relied upon to combine the color stream. As each color is presented, a color wheel (or an RGB LED array) illuminates the display with only red, green or blue light. If the frequency of the color fields is lower than about 540 Hz, an effect called color breakup is seen, where false colors are briefly perceived when either the image or the observer's eye is in motion. While less expensive, single-panel projectors require higher-speed display elements to process all three colors during a single frame time, and the need to avoid color breakup makes further demands on the speed of the display technology

[edit] Three-panel designs

In a DLP device the light is separated into three components and then combined back: Two beam splitters are needed. In LCoS devices the light is additionally polarized and then analyzed; four beam splitters are needed.

[edit] One-panel designs

There were two single-panel LCoS displays in production. One by Philips, and one by Uneed Systems of Korea.

[edit] See also

[edit] External links

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