Jump To:

Go Back Print Page

LCoS Projectors and DLP Projectors

The most similar competing system to DLP is known as LCoS (Liquid Crystal on Silicon), which creates images using a stationary mirror mounted on the surface of a chip, and uses a liquid crystal matrix, to control how much light is reflected.

Liquid Crystal on Silicon (LCoS)

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. This is contrary to LCD projectors which use a transmissive approach. 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. Before this LCoS has been used in standard sets 50" and above (November 2005).

There are two broad categories of projective microdisplay systems: 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. 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 DLP 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.

LCoS technology has the potential to enable the manufacture of big-screen (50" and larger) 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. 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.

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.

See Also

Video Projector Reviews

JVC DLA-X30 Review
Boxlight Pro7501dp
Panasonic PT-AE4000U
Mitsubishi HC4000 Review
JVC DLA-HD250 Review
HC3800 vs 8100
Boxlight Projectowrite2
Epson 8100 Review
Epson 8500UB
Boxlight MP65E

More Projector Reviews