Operation
FED display operates like a conventional cathode ray tube (CRT) with an electron gun that uses high voltage (10 kV) to accelerate electrons which in turn excite the phosphors, but instead of a single electron gun, a FED display contains a grid of individual nanoscopic electron guns.
A FED screen is constructed by laying down a series of metal stripes onto a glass plate to form a series of cathode lines. Photolithography is used to lay down a series of rows of switching gates at right angles to the cathode lines, forming an addressable grid. At the intersection of each row and column a small patch of emitters are deposited, typically using methods developed from inkjet printers. The metal grid is laid on top of the switching gates to complete the gun structure.
A high voltage-gradient field is created between the emitters and a metal mesh suspended above them, pulling electrons off the tips of the emitters. This is a highly non-linear process and small changes in voltage will quickly cause the number of emitted electrons to saturate. The grid can be individually addressed but only the emitters located at the crossing points of the powered cathode and gate lines will have enough power to produce a visible spot, and any power leaks to surrounding elements will not be visible. The non-linearity of the process allows avoidance of active matrix addressing schemes – once the pixel lights up, it will naturally glow for some time. Non-linearity also means that the brightness of the sub-pixel is pulse-width modulated to control the number of electrons being produced, like in plasma displays.
The grid voltage sends the electrons flowing into the open area between the emitters at the back and the screen at the front of the display, where a second accelerating voltage additionally accelerates them towards the screen, giving them enough energy to light the phosphors. Since the electrons from any single emitter are fired toward a single sub-pixel, the scanning electromagnets are not needed.
Read more about this topic: Field Emission Display
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