Samsung LTM1575W 15" TFT-LCD Display
Product Supplied By: Samsung Canada
Review by Paul Machado on
July 2, 2002
Retail Price: $2,499.99CDN
History of TFT LCD:
Liquid crystal was discovered by the Austrian
botanist Fredreich Rheinizer in 1888. "Liquid crystal" is neither solid nor
liquid (an example is soapy water).
In the mid-1960s, scientists showed that liquid crystals when stimulated by an
external electrical charge could change the properties of light passing through
the crystals.
The early prototypes (late 1960s) were too unstable for mass production. But all
of that changed when a British researcher proposed a stable, liquid crystal
material (biphenyl).
Today's color LCDs have a sandwich-like structure (see figure below).
What is TFT LCD Technology?:
TFT LCD (Thin Film Transistor Liquid Crystal Display) has a sandwich-like structure with liquid crystal filled between two glass plates.
TFT Glass has as many TFTs as the number of pixels displayed, while a Color Filter Glass has color filter which generates color. Liquid crystals move according to the difference in voltage between the Color Filter Glass and the TFT Glass. The amount of light supplied by Back Light is determined by the amount of movement of the liquid crystals in such a way as to generate color.
TFT LCD Electronic Aspects:
The most common liquid-crystal displays (LCDs) in
use today rely on picture elements, or pixels, formed by liquid-crystal (LC)
cells that change the polarization direction of light passing through them in
response to an electrical voltage.
As the polarization direction changes, more or less of the light is able to pass
through a polarizing layer on the face of the display. Change the voltage, and
the amount of light is changed.
There are two ways to produce a liquid-crystal image with such cells: the
segment driving method and the matrix driving method.
The segment driving method displays characters and pictures with cells defined
by patterned electrodes.
The matrix driving method displays characters and pictures in sets of dots.
1. Direct vs. multiplex driving of LCDs.
The segment drive method is used for simple
displays, such as those in calculators, while the dot-matrix drive method is
used for high-resolution displays, such as those in portable computers and TFT
monitors.
Two types of drive method are used for matrix displays. In the static, or
direct, drive method, each pixel is individually wired to a driver. This is a
simple driving method, but, as the number of pixels is increased, the wiring
becomes very complex. An alternative method is the multiplex drive method, in
which the pixels are arranged and wired in a matrix format.
To drive the pixels of a dot-matrix LCD, a voltage can be applied at the
intersections of specific vertical signal electrodes and specific horizontal
scanning electrodes. This method involves driving several pixels at the same
time by time-division in a pulse drive. Therefore, it is also called a
multiplex, or dynamic, drive method.
*Note* : Information Courtesy of Samsung Semiconductor
