21-02-2010, 11:37 AM
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Field Emission Display Screen
Introduction
Displays are devices by which we can view moving objects
Used in television and computers
They also have wide use in laboratories and in medical applications.
History of displays
Cathode ray tube
Liquid crystal display
Plasma displays
Electro luminescent displays
Field emission displays
FED Technology
The FED screen mainly contains three parts:
1.Low-voltage phosphorous plate
2.A field emission cathode using a thin carbon sheet as an edge emitter
3.FED packaging, including sealing and vacuum processing
Low voltage phosphor
The low voltage phosphors are the screens in which the images are displayed
In the display technology the phosphor screens act as anode, which receives the electrons emitted from the cathode
The phosphors are made up of layers of three primary colours -green, red and blue
Field Emission Cathode
In the field emission display screen the cathode are electron guns which emit electrons
Electron guns are called micro tips
The emission of electrons is called cold cathode emission
Micro tips are of different types
Wedge type emitter using silicon.
Silicon tips with continuous coating of diamond particles.
Single-crystal diamond particle on silicon tips.
Planar diode emitter.
Metal-insulator-semiconductor type planar emitter
Working
The field emission display works a bit like the cathode ray tube
This emission of electron occurs from the cold cathode when a voltage is applied between the cathode and anode
. These electrons propagate from cathode to anode
They bombard with the phosphor, which is the anode and causes it to glow
This reproduces the image on the screen by the mixing of colours present in the screen
Two ways of working
Low voltage anode
High voltage anode
Low Voltage Anode
In this method the entire screen is individually painted in each of the three primary colours, one at a time.
As each of the colours are painted separately only that colour phosphor is grounded, so that all the electrons can strike that particular colour
This prevents any of the electrons to strike accidentally the other colours present in the screen.
High Voltage Anode In the high voltage approach the emission from micro tip radiate in a roughly 600 cone
When these tips are very close to anode, the spread to emitted stream of electron is small enough to result in a spot size of nearly 0.33mm diameter
When the anode voltage is increased further greater phosphor efficiency is required and also the distance between anode and cathode should be increased to prevent arcing
FED Characteristics
Brightness
Speed
Compact and lightweight
Display size
Low driving voltage
Wider viewing angle
High illumination
Wide temperature extremes
Colour Quality
Draw Backs
Vacuum tubes do require maintenance.
Current FEDs often suffer from variation in screen brightness across the display, and also within each pixel.
Durability due to electrical discharge in the small gaps everywhere in FED prototypes.
The killing problem was durability: the tips couldnâ„¢t survive under severe conditions of arcing (i.e. electrical discharge) due to the small gaps everywhere in FED prototypes.
Another big problem for the FED concept is the cathode driver. For big screen applications, such as HDTV, it is difficult (if not impossible) to build a feasible high voltage
FED Applications
Sonograms
X-ray imaging
Heart-rate monitors
Laptop computers
Hang-on-the-wall televisions
Big screen and PC monitors
High-definition TV
Conclusion
CRT technology has already reached its technological and marketing limits and will likely be replaced in 10 years.
The modern world needs substances that are small in size.
This shows that the cathode ray tube do not have much to do anything in the market in future. And it would die already, if Field Emission Display (FED) technology or any other displays would bring anything to the market.
Field Emission Display Screen
Introduction
Displays are devices by which we can view moving objects
Used in television and computers
They also have wide use in laboratories and in medical applications.
History of displays
Cathode ray tube
Liquid crystal display
Plasma displays
Electro luminescent displays
Field emission displays
FED Technology
The FED screen mainly contains three parts:
1.Low-voltage phosphorous plate
2.A field emission cathode using a thin carbon sheet as an edge emitter
3.FED packaging, including sealing and vacuum processing
Low voltage phosphor
The low voltage phosphors are the screens in which the images are displayed
In the display technology the phosphor screens act as anode, which receives the electrons emitted from the cathode
The phosphors are made up of layers of three primary colours -green, red and blue
Field Emission Cathode
In the field emission display screen the cathode are electron guns which emit electrons
Electron guns are called micro tips
The emission of electrons is called cold cathode emission
Micro tips are of different types
Wedge type emitter using silicon.
Silicon tips with continuous coating of diamond particles.
Single-crystal diamond particle on silicon tips.
Planar diode emitter.
Metal-insulator-semiconductor type planar emitter
Working
The field emission display works a bit like the cathode ray tube
This emission of electron occurs from the cold cathode when a voltage is applied between the cathode and anode
. These electrons propagate from cathode to anode
They bombard with the phosphor, which is the anode and causes it to glow
This reproduces the image on the screen by the mixing of colours present in the screen
Two ways of working
Low voltage anode
High voltage anode
Low Voltage Anode
In this method the entire screen is individually painted in each of the three primary colours, one at a time.
As each of the colours are painted separately only that colour phosphor is grounded, so that all the electrons can strike that particular colour
This prevents any of the electrons to strike accidentally the other colours present in the screen.
High Voltage Anode In the high voltage approach the emission from micro tip radiate in a roughly 600 cone
When these tips are very close to anode, the spread to emitted stream of electron is small enough to result in a spot size of nearly 0.33mm diameter
When the anode voltage is increased further greater phosphor efficiency is required and also the distance between anode and cathode should be increased to prevent arcing
FED Characteristics
Brightness
Speed
Compact and lightweight
Display size
Low driving voltage
Wider viewing angle
High illumination
Wide temperature extremes
Colour Quality
Draw Backs
Vacuum tubes do require maintenance.
Current FEDs often suffer from variation in screen brightness across the display, and also within each pixel.
Durability due to electrical discharge in the small gaps everywhere in FED prototypes.
The killing problem was durability: the tips couldnâ„¢t survive under severe conditions of arcing (i.e. electrical discharge) due to the small gaps everywhere in FED prototypes.
Another big problem for the FED concept is the cathode driver. For big screen applications, such as HDTV, it is difficult (if not impossible) to build a feasible high voltage
FED Applications
Sonograms
X-ray imaging
Heart-rate monitors
Laptop computers
Hang-on-the-wall televisions
Big screen and PC monitors
High-definition TV
Conclusion
CRT technology has already reached its technological and marketing limits and will likely be replaced in 10 years.
The modern world needs substances that are small in size.
This shows that the cathode ray tube do not have much to do anything in the market in future. And it would die already, if Field Emission Display (FED) technology or any other displays would bring anything to the market.
