The Different Types of HDTV Displays

Digital television began in the late 1990s with the deployment of the DVB-T standard in Europe and ATSC in the United States. High definition television or HDTV technology was utilized on the onset in ATSC while Europe opted for standard definition or SDTV. HDTV offers better picture quality at higher resolutions from 720p to 1080p compared to SDTV resolution at only 480i/p or 576i/p. Australia is the only DVB-T country that already aired HDTV programs when it started digital broadcast in 2001.

Today, there are a number of HDTV display technologies available in the market. It will be difficult for a consumer to decide which type of HDTV to buy without the basic knowledge on the differences between these displays. Many years back, the only display technology available was CRT or the Cathode Ray Tube. At present, Plasma, LCD (Liquid Crystal Display), LED TV (a sub-type of LCD), and DLP (Digital Light Processing) are the different HDTV displays that are available in the market to choose from. How do the technologies behind these displays differ and which will provide the best value for your money?

 


Display Technologies Explained

 

CRT

or cathode ray tube is a display device that utilizes vacuum tubes, which contain electron guns and fluorescent screens. Picture data is emitted from the electron guns and corresponding images are displayed at the screen opposite the tube.

Pros:

  • Highest color performance
  • Best black response
  • No motion artifacts
  • Widest viewing angle
  • Smooth gray-scale response

Cons:

  • Bulky and heavy
  • High power consumption
  • Produce image flicker for refresh rates below 75
  • Low contrast ratio
  • Periodic calibration required for critical applications

Plasma

is a type of display technology based on gas consisting of xenon and neon contained in tiny cells or pixels sandwiched between two plates of glass. Each pixel consists of individual RGB light emitters that when lighted convert the gas into plasma. This process excites the phospor coating on the screen to produce the picture images.

Pros:

  • Good color quality
  • Good black response
  • Wide viewing angle
  • High contrast ratio
  • Fast screen refresh rate suited for fast moving pictures

Cons:

  • Suffers from Screen Burn that happens due to prolong display of stationary images
  • Screen Door Effect due to gaps between pixels
  • Display technology makes products heavy and bulky

LCD TV

is a display technology based on liquid crystals, which when activated by electric current align themselves. Polarized color filters on the screen and a source of fluorescent lighting at the back of the screen work in conjunction with the alignment process to produce the desired images.

Pros:

  • Does not suffer from screen burn
  • Longer screen life
  • Lesser power consumption
  • Better glare response
  • Brightest of all the types of display technologies
  • High contrast ratio
  • Display technology allows for slim and lighter products

Cons:

  • Slowest refresh rate of all the the types of display
  • Narrow viewing angle
  • Screen Door Effect due to gaps between pixels

LED TV

is actually a LCD TV that utilizes LEDs as a source of backlighting. There are two ways this can be done – 1) by placing LEDs across the entire back of the display or 2) by placing LEDs around the screen perimeter and using a special diffusion panel to spread the light evenly behind the screen. Most LED TVs in the market use the latter technique to allow the manufacturing of ultra-thin displays. LED TV should not be confused with OLED TV, which is an entirely different display technology.

Pros:

  • Display technology (edge-lit) allows for ultra thin products
  • Even lesser power consumption that fluorescent-backlit LCD TVs
  • Even higher contrast ratio than fluorescent-backlit LCD TVs
  • More environmentally friendly on disposal
  • All above-mentioned advantages of LCD TVs

Cons:

  • All above-mentioned disadvantages of LCD TVs

DLP

or Digital Light Processing is a rear projection technology in which the CRT projectors are replaced by microchip projectors. These consist of tiny mirrors that are laid out in a matrix of a semiconductor chip called Digital Micromirror Device (DMD). The picture images are produced in these tiny mirrors, each of which represent one picture pixel. The number of mirrors is equivalent to the resolution of the projected image.

Pros:

  • Darkest black-level and highest dynamic range of all types of display
  • High color response comparable to CRT direct view displays
  • High pixel fill factor prevents screen door effect and provides smooth images
  • Very fast pixel response times
  • Microchip technology allows the manufacturing of lighter and larger screen sizes

Cons:

  • Noise is produced by the color wheel and cooling fans
  • Possibility of color wheel rainbow artifacts

Which Display Technology is Best

The different HDTV display technologies discussed above offer better picture quality if the comparison is to earlier versions used during the analog television era. Each, however, have their own strengths and weaknesses and no one is a clear winner. But one thing is certain, there is a specific type of HDTV display for every application. It is up to the user to choose what satisfies his requirement and of course his budget.

CRT can be an option if the requirement is only for a small display and if the budget is tight. But the problem is, you can hardly find now HD-capable CRTS in the market. If the requirement is for a thin display at 50 inch or larger, Plasma is the best option. It offers good color and black response, fast refresh rate and better value for money at 50 inch and bigger screen sizes. Plasma is definitely the best choice for home theater systems. For screen sizes less than 50 inch and for home or office applications other than home theater systems, LCD and LED TVs are good options. Since LCD (fluorescent-backlit) is lighter than the other types of display, it is ideal for wall or ceiling mounting. If aesthetics or style is a further concern, then go for LED TV. Both LCD and LED TVs consume less power and do not suffer from screen burn so they are recommended for longer regular viewing and computer monitor applications. If the requirement is for very large screen sizes, DLP is the best choice for it also offers very good picture quality. This type of display is finding its way in small digital cinemas, which are now becoming practical alternatives to traditional projector-type cinemas.