LCDLCD Panels are based upon liquid crystal display technology.

Liquid Crystal

A liquid crystal is something between liquid and solid. A liquid crystal is temperature sensitive. This means that it is closer to liquid but not a complete liquid. The liquid crystal goes through different phases, which depends upon temperature. The liquid crystal in nematic phase is called nematic liquid crystal. Nematic crystals are used for Liquid Crystal Displays (LCDs).

LCD Technology

LCD panels are thin, flat and consist of large number of pixels. The pixels are made up of liquid crystals. The molecules of liquid crystal contain charges. These molecules are suspended between two polarized glass layers (filters) and two electrodes (transparent). When charge is applied on electrodes, the charge on crystal molecules cause them to arrange in twisted structure. As a result a varying light passes through the filters. So degree of light can be controlled with very low power consumption.

LCD Types

Passive matrix and the active matrix are two main type of LCDs used mostly in embedded systems and panels.

Passive Matrix

In passive matrix LCD panels the grid supplies charge to the pixels. The grid consists of two glass layers. The glass layers are coated with a conducting material. One layer is for rows and one for columns. Liquid crystals are kept inside of layers. Polarizing film is covered at outside of glass. Rows and columns are attached to the integrated circuits. To access a pixel, charge is sent on particular column. The ground of the specified row is activated. This results in row-column intersection at desired pixel. A passive matrix technology is easier and faster to implement. But it shows slow response times and an inaccurate voltage control.

ACTIVE Matrix

Active-matrix LCDs are based upon TFTs – thin film transistors. A TFT consists of small capacitor and switching transistor. TFTs are layered in form of a matrix (rows and columns intersects) on a thin glass panel. A particular row is selected. Charge is sent on the column that intersecting the row. Thus the capacitor on the desired pixel gets the charge. So a careful control over voltage can control the light through. Its main advantage is brightness whereas gray-scale is its drawback.

COLOR LCDs

To get color in LCDs, additional filters are use. They can divide each pixel into three sub-pixels of primary colors red, green, and blue. Then each sub-pixel is controlled (control over variation of applied voltage) to create millions of other colors for all the individual pixels.

Choosing LCD Panels

Choosing an LCD panel depends upon what requirements one have. Here are the issues associated with LCDs that can help you to decide what you need. LCD response times, resolution, contrast ratio, DVI or VGA ports and matrix type. LCD Panels present quite crisper image. Consumes very low power. Comes with DVI (for HD) and VGA (for standard signals) connectors. The response times are usually higher resulting in ghost images. The response time is the amount of time that an image is refreshed on screen. Viewing angle is relatively low. Temperature change affects the screen the screen.