LCD was first invented in 1968. But that invention took an unbelievable upward turn, showing way to future technology. Today, LCD is becoming increasingly commonplace in commercial electronic devices. The feature that LCD offers is ineludible. Let it be anything--cellular phones, personal digital assistants (PDAs), camcorders and laptop personal computers (PCs), LCD has to play major role in it.
The special feature of LCD, which puts it in altogther different group, is that it operates as a light "valve", allowing or blocking light passing through it. Using this unique property, an image is formed in LCD. When electric field is applied, chemical properties of each LCC (Liquid Crystal Cell) in the display changes, which in turn alters a pixel+s light absorption properties. To put it simply, these LCCs modify the image produced by the backlight into the screen output requested by the controller. Though the final output may be in color, the LCCs are monochrome, and the colour is added later through a filtering process. Modern laptop computer displays can produce 65,536 simultaneous colors at a resolution of 800 x 600.
Working of LCD
A light ray from the backlight is directed towards user. The light source is usually located directly behind the LCD (Source is either LED or conventional flourescent technology). From this source, the light ray passes through a light polariser, which uniformly polarises the light. From there, it is directed towards liquid crystal (LC) matrix, which determines whether this pixel should be triggered or not.
If the pixel is "on"(triggered), the liquid crystal cell is electrically activated, and the molecules in the liquid orients themselves in a single direction. This allows the light to pass without obstruction.
If the pixel is "off", the electric field is removed from the liquid, and the molecules within scatters. This obstructs the light that passes through the display at that pixel.
In a case of colour display, the light passes through the liquid crystal matrix. Then, it is made to pass through a colour filter (usually glass). This filter blocks all wavelengths of light except those within the range of that pixel. In a typical RGB display, the color filter is integrated into the upper glass coloured microscopically to render each individual pixel- red, green or blue colour. The areas in between the coloured pixel filter areas are made black to increase contrast. After a beam of light passes through the color filter, it passes through yet another polariser to sharpen the image and eliminate glare. The image is finally ready for viewing.