The Development of Data Projectors
The LCDs utilised for projection systems are generally small reflective or transmissive panels set off by a forceful arc lamp source. A number of lenses expands the reflected or transmitted image and displays it on the screen. In front-projection systems the LCD is set on the same side of the screen as the viewer, although in rear-projection systems the screen is lit from behind. Projectors of higher cost and performance sometimes be found with three distinct LCD panels, creating separate red, green, and blue images that combine to form a coloured picture on the screen.
The increase in desire for film presentations has put a growing emphasis on the switching speed of liquid crystals. This has required the manufacture of objects using smectic liquid crystals, some kinds of which possess a better electro-optical response than nematic liquid crystals. The surface-stabilized ferroelectric liquid crystal (SSFLC) display is currently the most complex smectic device. Within it the liquid crystal molecules are set out in perpendicular layers to the substrate planes, which are distanced by one or two micrometres, and in the layers the molecules are slanted, as illustrated in the figure. The host liquid crystal holds optically active molecules, and a scarcely perceptible turn up of the optical activity and the slant of the molecules is the presence 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 throughout the plane of the layers. Therefore, there is a permanent charge separation over the liquid crystal layer in the SSFLC, and its sign is directly partnered to the tilt direction of the molecules. An applied voltage of the right sign can reverse the direction of this dipole in tens of microseconds and so reverse the tilt direction of the molecules. The corresponding change in optical properties can effect a change from light to dark in the case that one or more polarizers are utilised.
SSFLC devices have been commercialized for bigger passive-matrix displays, but their cost and intricacy has impeded them from creating any significant progress on the market. Small transmissive and reflective active-matrix SSFLC displays, however, have some promise for use as elements in projection systems or as viewfinders in digital cameras. Their quick response allows them to be used in time-sequential colour systems, in which costly colour filters are taken out for a coloured backlight that flashes red, green, and blue in fast pulsing (approx 100 cycles in a second). For example, the liquid crystal might be switched to a transmissive state between the red and green periods but to a nontransmissive state for the blue period, creating the 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.
Sphere: Related Content