An LCD TV works by using a backlight to illuminate a screen made of liquid crystals that selectively block or allow light to pass through, creating the image you see.
Here's a more detailed breakdown:
Layers of an LCD TV
An LCD (Liquid Crystal Display) TV is composed of several layers that work together to produce an image. These layers include:
- Backlight: This provides the light source for the display. Older LCDs used fluorescent lamps (CCFLs), but modern LCD TVs predominantly use LEDs (Light Emitting Diodes) as backlights. LED backlights can be arranged in various ways, such as edge-lit (along the edges of the screen) or full-array (behind the entire screen).
- Polarizing Filters: These filters allow only light waves vibrating in a specific direction to pass through. There are two polarizing filters in an LCD, oriented at 90 degrees to each other. This means that light that passes through the first filter will be blocked by the second filter.
- Liquid Crystals: This is the heart of the display. Liquid crystals are a substance that can change its properties (specifically, its alignment) when an electric current is applied. The crystals are arranged in tiny cells, each representing a pixel. When no electric field is applied, the liquid crystals align to twist the light passing through them, allowing it to pass through the second polarizing filter. When an electric field is applied, the crystals untwist, blocking the light.
- Color Filters: Each pixel is divided into subpixels – red, green, and blue. These color filters allow only the corresponding color of light to pass through. By controlling the brightness of each subpixel, a wide range of colors can be created.
- Glass Substrate: Provides structural support and encapsulates the other layers.
The Process Explained Step-by-Step
- Backlight Illumination: The backlight emits white light.
- Polarization: The light passes through the first polarizing filter, becoming polarized.
- Liquid Crystal Control: The polarized light then passes through the liquid crystal layer. By applying a voltage to the liquid crystals, their alignment can be controlled. This controls the degree to which the light is twisted.
- Second Polarization: The twisted (or untwisted) light reaches the second polarizing filter. If the light has been twisted by 90 degrees, it will pass through. If it hasn't been twisted, it will be blocked. This is how the LCD blocks or allows light to pass through each pixel.
- Color Filtering: The light then passes through the red, green, and blue color filters, creating the individual subpixels.
- Image Creation: By controlling the brightness of each subpixel, the LCD can create a wide range of colors and shades, forming the final image.
Key Concepts Summarized
| Component | Function |
|---|---|
| Backlight | Provides the source of light for the display. |
| Polarizing Filters | Ensures light waves only vibrate in a certain direction, which helps to manipulate the light for image creation. |
| Liquid Crystals | Controls how much light passes through each pixel by twisting or untwisting the polarized light based on applied voltage. |
| Color Filters | Creates the red, green, and blue subpixels necessary to produce a full range of colors in the final image. |
In essence, an LCD TV uses a backlight and electronically controlled liquid crystals to rotate polarized light, allowing varying amounts of light to pass through color filters and ultimately create the image you see.
