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User Manual BDL4211x
9
Q: How are LCDs made?
A: LCDs are created from two glass plates separated from each other at a distance of a few
microns. The plates are filled with liquid crystal and then sealed together. The top plate is colored
with an RGB pattern to make the color filter. Polarizers are then glued to both plates. This
combination is sometimes called 'glass' or 'cell.' The LCD cell is assembled into a 'module' by
adding the backlight, driver electronics and frame.
Q: What is polarization?
A: Polarization is basically directing light to shine in one direction. Light is electromagnetic waves.
Electric and magnetic fields oscillate in a direction perpendicular to the propagation of the light
beam. The direction of these fields is called the 'polarization direction'. Normal or non-polarized
light has fields in several directions; polarized light has a field in only one direction.
Q: What differentiates passive matrix LCDs from active matrix LCDs?
A: An LCD is made with either a passive matrix or an active matrix display grid. An active matrix
has a transistor located at each pixel intersection, requiring less current to control the luminance
of a pixel. For this reason, the current in an active matrix display can be switched on and off more
frequently, improving the screen refresh time (your mouse pointer will appear to move more
smoothly across the screen, for example). The passive matrix LCD has a grid of conductors with
pixels located at each intersection in the grid.
Q: How does a TFT LCD Panel work?
A: On each column and row of the TFT LCD panel a data source drive and a gate drive and
attached, respectively. The TFT drain of each cell is connected to the electrode. The molecular
arrangement of liquid crystal elements differs acceding to whether it is impressed with voltage or
not. It varies the direction of polarized light and the amount of light by letting it through different
arrays of liquid crystal elements. When two polarized filters are arranged vertically on a polarized
light pole, the light that passes through the upper polarized panel is turned 90 degrees along with
the spiral structure of the liquid crystal molecules and goes through the polarized filter at the
bottom. When impressed with voltage, liquid crystal molecules are arranged vertically from the
original spiral structure and the direction of the light is not turned through 90 degrees. In this case,
light that comes through the top polarized panel may not go through the polarized panel at the
bottom.