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The LCDs used in projection systems are typically small reflective or transmissive panels lit by a strong arc lamp source. A series of lenses expands the reflected or transmitted image and then casts it onto the screen. For front-projection systems the LCD is situated on the same area of the screen as the viewer, but in rear-projection systems the screen is illuminated from behind. Projectors of greater expense and capacity might be found with three separate LCD panels, casting separate red, green, and blue images that come together to reflect a coloured display on the screen.

The growing requirement for video presentations has put a special emphasis on the switching speed of liquid crystals. This has demanded the manufacture of objects build with smectic liquid crystals, certain ones of which possess a speedier electro-optical response than nematic liquid crystals. The surface-stabilized ferroelectric liquid crystal (SSFLC) display is currently the most complex smectic device. With it the liquid crystal molecules are set out in layers that are perpendicular to the substrate planes, which are distanced by one or two micrometres, and throughout the layers the molecules are on a tilt, as shown in the figure. The host liquid crystal possesses optically active molecules, and a scarcely perceptible consequence of the optical activity and the shape of the molecules is the appearance of a permanent charge separation, or ferroelectric dipole, analogous to the ferromagnetic dipole of a magnet. The direction of this dipole is perpendicular to the tilt direction of the molecules and through the plane of the layers. Therefore, there must be a permanent charge separation over the liquid crystal layer in the SSFLC, and its sign is directly attracted to the tilt direction of the molecules. An applied voltage of the corresponding sign can reverse the direction of this dipole in tens of microseconds and therefore reverse the tilt direction of the molecules. The respective change in optical properties can create a change from light to dark if one or more polarizers are employed.

SSFLC devices have been commercialized for big passive-matrix displays, but their expense and intricacy has stopped them from having any great impact on the market. Small transmissive and reflective active-matrix SSFLC displays, however, display some promise for use as aspects in projection systems or as viewfinders in digital cameras. Their fast response allows them to be used in time-sequential colour systems, in which high cost colour filters are emulated with a coloured backlight that flashes red, green, and blue in quick succession (around 100 cycles a second). For example, the liquid crystal may be switched to a transmissive state in the red and green periods and to a nontransmissive state in the blue period, creating the end result that the eye sees an average of red and green light, or the colour yellow.

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