The working principle of LCD screens, broadly known as Liquid Crystal Displays, involves the manipulation of light by liquid crystals in order to produce images. The LCD technology is widely used in various electronic devices, such as televisions, computer monitors, smartphones, and tablets, due to its compactness and energy efficiency.

 

An LCD screen primarily consists of several key components: a backlight, polarizing filters, color filters, liquid crystals, and a pixel matrix. The process starts with the backlight, which is typically a fluorescent lamp or LED array placed behind the screen. The backlight emits uniform white light, supplying the necessary illumination for the display.

 

The polarizing filters are positioned on the front and back of the LCD panel. They only allow light waves vibrating in a specific direction to pass through. The front filter permits light waves oscillating vertically, while the back filter accepts horizontally vibrating light waves. Consequently, the light becomes polarized as it travels through these filters.

 

Behind the front polarizing filter, there is a layer that contains color filters. These filters are arranged in a pattern to generate red, green, and blue subpixels, which are the primary building blocks used to display colors. Each color filter absorbs all other colors except the one corresponding to its intended primary color.

 

The liquid crystals, located between the color filters and the back polarizing filter, further control the passage of light through the display. The liquid crystals are composed of elongated organic molecules that can change their alignment when subjected to an electric field.

 

Each pixel in the LCD screen comprises three subpixels, one for each primary color. The liquid crystals in each subpixel can be aligned in three different states: twisted, untwisted, or partially twisted. The alignment of the liquid crystals determines the amount of light that can pass through the subpixel, consequently influencing the color and intensity displayed.

 

To manipulate the liquid crystals, thin-film transistors (TFTs) are used. A TFT acts as a switch that controls the electric field applied to its corresponding liquid crystal. By adjusting the voltage across the TFT, the liquid crystals can be oriented to allow or block the passage of light. This process is controlled electronically and corresponds to the desired image or color that needs to be displayed.

 

When an electric charge is applied to the TFT of a pixel, it allows the liquid crystals to untwist or partially untwist, enabling light to pass through. This alignment change allows the polarized light from the backlight to either pass through the color filters or be blocked, resulting in the desired color display. By varying the voltage applied to the liquid crystals, the level of light passing through can be finelycontrolled, thus creating different shades and intensity levels.

 

In summary, LCD screens work by controlling the alignment of liquid crystals through the application of electric fields. By utilizing polarizing filters, color filters, and a backlight, LCDs are able to produce vibrant and colorful images with high precision. This technology has revolutionized the display industry and become an integral part of our daily lives.