Current TV Technology

For 60 years, the cathode ray tube (CRT) was the most popular television display technology. Until recently, it has remained the standard for image quality, particularly for contrast and color, because it offers deep blacks and lifelike hues.

However, the sheer physical size and weight of CRTs make screen sizes larger than 36 inches impractical.

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Over the last 10 years, new display technologies, such as flat-panel LCDs, plasma, and microdisplay rear-projection systems (DLP™ and LCoS), have offered larger screens, slimmer form factors with higher resolution images, and the promise of greater realism.

While plasma has been the dominant technology for screens larger than 40 inches, according to DisplaySearch, shipments of 40-inch and larger LCDs have surpassed plasma screens and continue to increase.

LCDs’ main advantages are higher resolution, a thinner form factor, lower weight, less power consumption and lower cost (especially for 1080p resolution).

 

LCD Panel Basics

An LCD screen consists of the LCD array itself, plus various protective and diffusing layers and a CCFL backlight module, which illuminates the liquid crystal color filters to produce an image on the screen (see Figure 1).

Current LCD technology excels in resolution but its brightness and contrast capabilities limit its ability to reproduce truly lifelike images:

1. No true black and a limited contrast ratio (about 2,000:1). Even in their off state, LCDs cannot completely block the illumination from the backlight. Turning down the backlight improves black levels, but reduces brightness.
2. An artificial look to colors, particularly flesh tones, and to depth and texture because of the nature of the CCFL backlight.
3. Constant brightness, even when images require little light. Power consumption also remains constant.

 

LED Backlighting

 

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The industry is beginning to switch from CCFLs to LEDs, the advantages of which include:

1. Friendlier to the environment: LEDs contain no mercury and have a long lifespan.
2. Faster response time than CCFLs.
3. Increased color gamut with RGB LEDs.
4. Projected exponential increases in efficiencies, in terms of lumens per watt.
5. Declining costs, in terms of dollar per lumen per watt.

LED technical improvements and cost reductions are likely to continue, because demand from other industries—for instance, advanced automotive headlight and taillight systems—is expected to drive increased production capacity and efficiencies. Many laptop LCD screens and one television product line already use LED backlights.