The LCDs used for projection systems are usually small reflective or transmissive panels illuminated by a powerful arc lamp source. A series of lenses magnifies the reflected or transmitted image then sends it onto a screen. With front-projection systems the LCD is located on the same area of the screen as the viewer, but in rear-projection systems the screen is lit from behind. Projectors of greater expense and capability can have three separated LCD panels, reflecting 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 growth in emphasis on the switching speed of liquid crystals. This has necessitated the development of devices utilizing smectic liquid crystals, certain types of which possess a faster electro-optical response than nematic liquid crystals. The surface-stabilized ferroelectric liquid crystal (SSFLC) display is at this time the most sophisticated smectic device. Within it the liquid crystal molecules are set out in layers perpendicular to the substrate planes, which are differentiated by one or two micrometres, and in the layers the molecules are on a slant, as shown in the figure. The host liquid crystal contains optically active molecules, and a subtle consequence of the optical activity and the angle of the molecules is the presence of a permanent charge separation, or ferroelectric dipole, comparable 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. Hence, there exists a permanent charge separation through the liquid crystal layer in the SSFLC, and its sign is directly paired up 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 hence reverse the tilt direction of the molecules. The consequential change in optical properties can cause a change from light to dark in the case that one or more polarizers are used.

SSFLC devices have been produced for larger passive-matrix displays, but their expense and intricacy has prevented them from creating any remarkable impact on the market. Small transmissive and reflective active-matrix SSFLC displays, however, show some promise for use as elements in projection systems or as viewfinders in digital cameras. Their quick reacting allows them to be made use of in time-sequential colour systems, in which costly colour filters are emulated with a coloured backlight that flashes red, green, and blue in quick speed (about 100 cycles every second). For example, the liquid crystal could be switched to a transmissive state in the red and green periods and to a nontransmissive state for the blue period, having the end result that the eye sees an average of red and green light, or the colour yellow.

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