Data Projector Evolution

The LCDs built in projection systems are most often small reflective or transmissive panels set off by a bright arc lamp source. A line of lenses expands the reflected or transmitted image and then casts it onto the screen.

With front-projection systems the LCD is situated on the side of the screen as the viewer, but in rear-projection systems the screen is set off from behind. Projectors of greater cost and capability can use three separated LCD panels, creating separate red, green, and blue images that come together to make a coloured picture on the screen.

The increase in desire for video displays has put a special emphasis on the switching speed of liquid crystals. This has led to the invention of objects using smectic liquid crystals, particular types of which emit a faster electro-optical response than nematic liquid crystals.

The surface-stabilized ferroelectric liquid crystal (SSFLC) display is in the current day the most complex smectic device. Within it the liquid crystal molecules are arranged in perpendicular layers to the substrate planes, which are differentiated by one or two micrometres, and throughout the layers the molecules are on a tilt, as illustrated in the figure.

The host liquid crystal has optically active molecules, and a scarcely perceptible consequence of the optical activity and the slant of the molecules is the appearance of a permanent charge separation, or ferroelectric dipole, similar 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. Hence, there has to be a permanent charge separation through the liquid crystal layer in the SSFLC, and its sign is directly paired 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 therefore reverse the tilt direction of the molecules. The respective change in optical properties can make a change from light to dark if or when one or more polarizers are employed.

SSFLC devices have been marketed for big passive-matrix displays, but their expensiveness and complex nature has stopped them from enjoying any great progress on the market. Small transmissive and reflective active-matrix SSFLC displays, however, have some possibility for use as aspects in projection systems or as viewfinders in digital cameras. Their quick reacting allows them to be employed in time-sequential colour systems, in which costly colour filters are replaced with a coloured backlight that flashes red, green, and blue in fast pace (approx 100 cycles per second). For example, the liquid crystal may be switched to a transmissive state during the red and green periods but to a nontransmissive state in the blue period, with the upshot 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.

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