ADF News

The LCDs built in projection systems are most often small reflective or transmissive panels lit up by a forceful arc lamp source. A series of lenses magnifies the reflected or transmitted image and then displays it on a screen. For front-projection systems the LCD is situated on the same side of the screen as the viewer, but in rear-projection systems the screen is illuminated from behind. Projectors of higher expense and capacity sometimes utilise three separated LCD panels, reflecting separate red, green, and blue images that come together to reflect a coloured picture on the screen.

The growth in desire for film displays has granted a growth in emphasis on the switching speed of liquid crystals. This has led to the development of devices utilizing smectic liquid crystals, some kinds of which possess a quicker electro-optical response than nematic liquid crystals. The surface-stabilized ferroelectric liquid crystal (SSFLC) display is at this time the most sophisticated smectic device. With it the liquid crystal molecules are set out in layers that are perpendicular to the substrate planes, which are separated by one or two micrometres, and within the layers the molecules are tilted, as demonstrated in the figure. The host liquid crystal holds optically active molecules, and a subtle outcome of the optical activity and the tilt 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 in the plane of the layers. Hence, there is a permanent charge separation across 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 correct sign can reverse the direction of this dipole in tens of microseconds and so reverse the tilt direction of the molecules. The consequential change in optical properties can create a change from light to dark if one or more polarizers are used.

SSFLC devices have been marketed for large passive-matrix displays, but their expense and detail has stopped them from making any significant impact on the market. Small transmissive and reflective active-matrix SSFLC displays, however, have displayed some promise for use as elements in projection systems or as viewfinders in digital cameras. Their speedy responding allows them to be made use of in time-sequential colour systems, in which expensive colour filters are taken out for a coloured backlight that flashes red, green, and blue in quick pace (around 100 cycles in a second). For example, the liquid crystal could be switched to a transmissive state in the red and green periods and then to a nontransmissive state during 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.