How TFT's Work

 

Panel Manufacturers
How TFT Technology Works
LED backlighting

OLED Displays

DVI Cables
DisplayPort
CableComp

Faroudja Video Processing
TFT Life Span

 

 


Panel Manufacturers

 

While there are many different manufacturers of TFT monitors, there are several main manufacturers of the panels themselves incorporated into these screens. The main manufacturers in todayís TFT market are

 

 

AU Optronics (AUO)

Samsung

LG.Display (LGD)
Previously known as LG.Philips (LPL)

Sharp

BOE Hydis (BOE)

Hitachi

Chi Mei Optoelectronics (CMO)

Chunghwa Picture Tubes (CPT)

NEC

ID Tech

HannStar

S-LCD
(Samsung+Sony Joint Venture)

            
 

These manufacturers produce a wide range of panel technologies and of differing specs, and source their panels to the monitor manufacturers. For further information and read, see also:

- TFT Central Panel Search - find out which panel is used in a specific model
- TFT Central Panel Part Database -  specs of all the panel modules used

- Horizon Technology - Panel model numbers and links
- LCDTech - Monitor panel database

- Prad.de - German site, but good TFT news. Also panel and spec checking

 

 


How TFT Technology Works

Tom's Hardware provide a good guide to how the TFT monitors work. Another resource which is good comes from one of the biggest panel manufacturers in the world,  and AU Optronics provide a good background to LCD / TFT technology here. There is a lot of information around on the net about the electronics and specifics of TFT technology so I won't re-hash it too much here.

 

 


LED backlighting

 

Traditional CCFL backlighting has been replaced in some models by LED backlighting. This is a new technology, but is designed to offer a few improvements over conventional methods. These include improved panel uniformity, improved life expectancy, and because LEDís are capable of producing whiter whites, the colour fidelity should be improved. Look for models which specifically state that they are LED backlit.

 


Organic Light Emitting Diode (OLED)

This technology was invented in the 1980's. The pros of OLED technology are: Since it is a light emitter, it creates light that is Lambertian so it can be seen uniformly at all angles and gives a very pleasing effect. Wide viewing angles are a key feature of these displays. The biggest strength of OLED's is that they do not require a backlight and can be made thinner than any other technology used today. A 2 mm thick OLED is a reality today where the thinnest LCD is 3 mm.  With no backlight, lighting of the panel is uniform, and they are designed to offer higher brightness and contrast ratios. They will also require less power to operate as they do not need backlighting. They are cheaper to produce than LCD's because they use less materials and the polymers can be "printed" onto plastic or glass sheets using a process similar to inkjet printing. Theoretically, they will be cheaper to produce and so should be cheaper to buy. There are some drawbacks to the technology however:

 

         Dynamic display efficiency. While you can write a few lines of static text with great efficiency, video requires more power than an LCD. OLED's are more efficient for small graphics or text because they only consume power in the area where they are addressed. To date, the reliability has not come up to the levels of LCD's. It is particularly difficult to drive the blue colours where the luminance efficiency is very low. As a consequence, the lifetime is reduced, and burn-in is also an issue. Red and green colour polymers are apparently sturdy enough, but problems with the blue colours are a hurdle at the moment.

 

There is a more detailed article about the technology here on Sharp's and AU Optronics' websites:
 

http://www.sharpsma.com/lcd/lcdguide/Technologies/OLED_displays.php

http://www.auo.com/auoDEV/technology.php?sec=OLED&ls=en

 

OLED displays are not likely to be widely used in the TFT desktop market, and will likely be more aimed at large TVís and Hi-Def displays. These probably wonít emerge until 2007 as well, and will likely be very pricey. However, it is an emerging technology, which I think is worth mentioning.

 

 


DVI Cables

 

DVI is the first digital standard and supports a dual link mode, which allows resolutions up to 2048 x 1536 and beyond. The DVI specification supports hot plug and play display devices.

There are 3 main different configurations when it comes to DVI:


1. DVI-A is designed for analogue only connections
2. DVI-D is designed for digital signals only and is 24 pin
3. DVI-I (Integrated) is a single connector which is designed for both digital and analog use, and is backward compatible with analog displays. DVI-I is 29 pin

 

                                                                


                                                             A DVI >  VGA Adapter  

 

 


                
DVI-D Cable Connection

                                                                        



Most LCD monitors that support digital signal have DVD-D connectors. A DVI-D cable connection is shown.

The cables: DVI-I single link configuration provides bandwidth sufficient for res up to 1600 x 1200 and high speed transmission up to 4.95Gbps. DVI-I dual link config can do 2048 x 1536 @ 9.9Gbps, this is the same for a DVI-D dual link configuration.

Cable suppliers recommend: "Most customers should use a DVI-D to DVI-D cable. We suggest that you do not order a DVI-I to DVI-I cable unless you are certain that it will work for your application."

 

It is possible to get DVI Ė VGA converters. These will not offer any improvements over a standard analogue connection, as you are still going through a conversion from digital to analogue somewhere along the line.

 

 


DisplayPort

Together with other leading video companies like ATI, NVIDIA, Philips and Samsung, Genesis have proposed a new high bandwidth digital interconnect standard. This is designed to greatly simplify connectivity for streaming media from one system to another. It allows streaming of up to 6 High Definition TV Channels simultaneously in the same number of wires that current cables use to only stream 1 channel. Further information about DisplayPort can be found here:

 

Overview: http://gnss.com/technology/DisplayPort Overview White Paper.pdf

Technical: http://gnss.com/technology/DisplayPort Technical Overview White Paper.pdf


 

 


CableComp 

NEC have introduced their "CableComp" technology which automatically compensates for signal quality differences caused by long cables and weak signals. The technology allows you to use cables of up to 20m and still support the 1600 x 1200 resolution over DVI. This is as compared with normal operation of about 7m. For 1280 x 1024 resolution on DVI you can use cables up to 30m in length, and for VGA / Analogue connections, up to 100m! This is achieved through the use of a booster and intermediate replicater, and does not lead to any delay either.


 


Faroudja Video Processing Technology

 

This technology was developed by Faroudja, a subsidiary of Genesis who manufacturer monitor controller chips. The technology consists of a suite of enhancement algorithms designed to improve image quality. These include:

 

See the following article for more information: Faroudja Video Processing and Genesis Controller Chips

 

 

 


TFT Life Span

 

The main area to consider really here is the backlight. TFTís are backlit using CCFL lamps, and these typically have a life expectancy of >40,000hrs. To give you an idea that would be 4.5yrs of the panel being on 24/7 or 9yrs with a more realistic 12/7. Basically by the time the TFT has had itís better days, you will probably be wanting to buy a new one anyway.