News and Articles Resource

Data Projector Evolution

The LCDs put for projection systems are usually small reflective or transmissive panels illuminated by a forceful arc lamp source. A number of lenses expands the reflected or transmitted image and casts it onto a screen.

In front-projection systems the LCD is located on the same area of the screen as the viewer, while in rear-projection systems the screen is lit up from behind. Projectors of more expense and capacity may utilise three separate LCD panels, reflecting separate red, green, and blue images that mesh to create a coloured image on the screen.

The increasing need for video displays has had a particular emphasis on the switching speed of liquid crystals. This has required the development of devices 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 in the current day the most sophisticated smectic device. Within it the liquid crystal molecules are arranged in layers perpendicular to the substrate planes, which are separated by one or two micrometres, and within the layers the molecules are tilted, as displayed in the figure.

The host liquid crystal holds optically active molecules, and a slight consequence of the optical activity and the shape of the molecules is the appearance 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 within the plane of the layers. Therefore, there exists 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 corresponding sign can reverse the direction of this dipole in tens of microseconds and therefore reverse the tilt direction of the molecules. The corresponding change in optical properties can create a change from light to dark when one or more polarizers are employed.

SSFLC devices have been publicized for big passive-matrix presentations, but their high cost and intricacy has stopped them from creating any significant progress on the market. Small transmissive and reflective active-matrix SSFLC displays, however, have displayed some possibility 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 expensive colour filters are emulated by a coloured backlight that flashes red, green, and blue in rapid speed (around 100 cycles every second). For example, the liquid crystal might be switched to a transmissive state for the red and green periods and then to a nontransmissive state for the blue period, displaying the outcome 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.