Liquid Crystal Display (LCD)
uses liquid crystal fluid as the active medium to create images. As shown in Fig.
1, a very large number of thin crystals suspended in a fluid. The liquid reservoir
is sandwiched between two thin layers of glass. Each layer of glass has a transparent
conductive electrode bonded to it.
Figure
1
Polarizing
material are placed on the outside surface of both front and rear glasses. The
top polarizer can polarize the incident light of random polarization into its
polarization direction. Before an electric field is applied on the conductors,
the crystals are aligned in a spiral pattern. The light is then changed by the
spiral pattern of the crystals. The bottom polarizer is aligned opposite of the
top polarizer. When the light reaches the bottom polarizer, they will align with
each other. The light can pass through and as shown in Fig. 2, the LCD looks transparent.
Figure
2
When
in an electric field, the crystals align themselves with the field so the light
can pass through the crystal without being deflected, as shown in Fig. 3. The
light is then out of phase with the bottom polarizer when the light is absorbed
by the polarizer. The light can't pass through and the LCD looks dark or opaque.
By turning on/off electric field, we can create desired display patterns.
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