Pixels light up by emitting light, typically through the activation of small components within them. The exact mechanism depends on the display technology. In older CRT (Cathode Ray Tube) monitors, pixels light up when phosphors are struck by electron beams. In modern LCD (Liquid Crystal Display) screens, they light up via backlighting and liquid crystals that either block or allow light to pass through colored filters. OLED (Organic Light Emitting Diode) pixels, on the other hand, generate their own light when electricity is applied.
Pixel Illumination Mechanisms
Here's a breakdown of how pixels light up in different display technologies:
Cathode Ray Tube (CRT) Displays
- Electron Guns: CRT monitors use electron guns located at the rear of the tube. These guns fire beams of electrons.
- Phosphor Coating: The inside of the screen is coated with tiny dots of phosphors. There are three types of phosphors: red, green, and blue.
- Light Emission: When an electron beam strikes a phosphor dot, the phosphor emits light. The intensity of the light is determined by the intensity of the electron beam. The combination of red, green, and blue light allows the pixel to display a wide range of colors.
- Black Mask: A black mask surrounds each phosphor dot to prevent light from one dot from bleeding into another, enhancing image clarity.
Liquid Crystal Display (LCD) Screens
- Backlight: LCDs use a backlight, typically made of LEDs (Light Emitting Diodes), to provide a source of light.
- Liquid Crystals: The light from the backlight passes through liquid crystals. These crystals can be twisted to varying degrees when an electric field is applied.
- Polarizing Filters: Two polarizing filters are placed before and after the liquid crystals, oriented at 90 degrees to each other. When the liquid crystals are untwisted, they block the light. When twisted, they allow light to pass through.
- Color Filters: After passing through the liquid crystals and polarizing filter, the light goes through a color filter containing red, green, and blue subpixels. The intensity of light passing through each subpixel determines the color of the pixel.
Organic Light Emitting Diode (OLED) Displays
- Organic Compounds: OLED displays use organic compounds that emit light when an electric current is passed through them.
- Self-Emissive: Unlike LCDs, OLEDs are self-emissive, meaning each pixel generates its own light. This allows for perfect blacks (when a pixel is turned off, it emits no light) and high contrast ratios.
- No Backlight Required: Because OLEDs generate their own light, they do not require a backlight, making them thinner and more energy-efficient than LCDs.
Summary Table
| Technology | Light Source | Mechanism |
|---|---|---|
| CRT | Electron Beams | Electron beams strike phosphors, causing them to emit light. |
| LCD | Backlight (LEDs) | Light passes through liquid crystals and polarizing filters, controlled by an electric field, then through color filters. |
| OLED | Organic Compounds | Organic compounds emit light when electricity is applied. |
In essence, pixels light up through different mechanisms depending on the display technology used, but all involve converting some form of energy (electrical or electron beam) into visible light.
