LED (Light Emitting Diode)

A LED-backlit LCD is a flat panel display which uses LED backlighting instead of the cold cathode fluorescent (CCFL) backlighting. LED-backlit displays use the same TFT LCD (thin-film-transistor liquid-crystal display) technologies as CCFL-backlit displays, but offer reduced energy consumption, better contrast and brightness, greater color range (using more expensive RGB LEDs, blue LEDs with RG phosphors, or quantum dot enhancement film (QDEF)), more rapid response to changes in scene (with dynamic backlight dimming), and photorefractive effects.

LED Display Advantages

  • Wider color gamut (with RGB-LED or QDEF) and dimming range
  • Very slim (some screens are less than 0.5 inches (13 mm) thin in edge-lit panels)
  • Significantly lighter and cooler, as much as half the total chassis and system weight of a comparable CCFL
  • Typically 20–30% lower power consumption and longer lifespan
  • More reliable than CCFL

LED Arrangement

LED backlights replace CCFL (fluorescent) lamps with several dozen to several hundred white or blue LEDs. Two types of LED arrangement may be used:

Edge-lit LEDs
LEDs form a line around the rim of the screen, with a special diffusion panel (light guide) to spread the light evenly behind the screen.

Direct LED full array
LEDs form an array directly behind the screen at equally spaced intervals.

In Full array local dimming (FALD), LEDs are controlled individually to dynamically control the level of light intensity in a given part of the screen. This method of backlighting allows local dimming of specific areas of darkness on the screen, resulting in much higher dynamic-contrast ratios, though at the cost of less detail in small, bright objects on a dark background, such as star fields or shadow details.

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