ADF News

The LCDs built in projection systems are typically small reflective or transmissive panels lit up by a forceful arc lamp source. A series of lenses magnifies the reflected or transmitted image and sends it on the screen. With front-projection systems the LCD is situated on the same area of the screen as the viewer, while in rear-projection systems the screen is set off from behind. Projectors of greater expense and performance can have three distinct LCD panels, reflecting separate red, green, and blue images that come together to reflect a coloured picture on the screen.

The increasing demand for visual presentations has placed a particular emphasis on the switching speed of liquid crystals. This has necessitated the manufacture of items employing smectic liquid crystals, certain types of which have a better electro-optical response than nematic liquid crystals. The surface-stabilized ferroelectric liquid crystal (SSFLC) display is at this point the most developed smectic device. With it the liquid crystal molecules are cast in layers that are perpendicular to the substrate planes, which are distanced by one or two micrometres, and inside the layers the molecules are on a slant, as illustrated in the figure. The host liquid crystal has optically active molecules, and a minor result of the optical activity and the tilt of the molecules is the presence of a permanent charge separation, or ferroelectric dipole, likeable to the ferromagnetic dipole of a magnet. The direction of this dipole is perpendicular to the tilt direction of the molecules and within the plane of the layers. Hence, there has to be a permanent charge separation through 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 correct sign can reverse the direction of this dipole in tens of microseconds and by doing so reverse the tilt direction of the molecules. The corresponding change in optical properties can effect a change from light to dark when one or more polarizers are employed.

SSFLC devices have been marketed for bigger passive-matrix displays, but their cost and intricacy has prevented them from making any particular progress on the market. Small transmissive and reflective active-matrix SSFLC displays, however, have some probability for use as elements in projection systems or as viewfinders in digital cameras. Their speedy response allows them to be used in time-sequential colour systems, in which highly expensive colour filters are emulated with a coloured backlight that flashes red, green, and blue in rapid pace (about 100 cycles per second). For example, the liquid crystal may be switched to a transmissive state between the red and green periods and to a nontransmissive state in the blue period, with the end result that the eye sees an average of red and green light, or the colour yellow.

For help with choosing and purchasing your data projector, contact projectors brisbane and projectors gold coast.