Vacuum fluorescent display
Each tube in a VFD has a phosphor-coated carbon anode that is bombarded by electrons emitted from the cathode filament.
[5] The first multi-segment VFD was a 1967 Japanese single-digit, seven-segment device made by Ise Electronics Corporation.
[8] The device consists of a hot cathode (filaments), grids and anodes (phosphor) encased in a glass envelope under a high vacuum condition.
[11] The anode consists of a glass plate with electrically conductive traces (each trace is connected to a single indicator segment), which is coated with an insulator, which is then partially etched to create holes which are then filled with a conductor like graphite, which in turn is coated with phosphor.
The most widely used phosphor is Zinc-doped copper-activated Zinc oxide,[2] which generates light at a peak wavelength of 505 nm.
AMVFD displays that incorporate a driver IC are available for applications that require high image brightness and an increased number of pixels.
Hybrid VFDs include both fixed display segments and a graphic VFD in the same unit.
The segments can also be placed exclusively on the front instead of on the back, improving viewing angles and brightness.
[14][15][16][17][18][19][20][21][22] Besides brightness, VFDs have the advantages of being rugged, inexpensive, and easily configured to display a wide variety of customized messages, and unlike LCDs, VFDs are not limited by the response time of rearranging liquid crystals and are thus able to function normally in cold, even sub-zero, temperatures, making them ideal for outdoor devices in cold climates.
Early on, the main disadvantage of such displays was their use of significantly more power (0.2 watts) than a simple LCD.
[citation needed] While later games had sophisticated multi-color displays, early games achieved color effects using transparent filters to change the color of the (usually light blue) light emitted by the phosphors.
LCD games could be manufactured for a fraction of the price, did not require frequent changes of batteries (or AC adapters) and were much more portable.
In addition to the widely used fixed character VFD, a graphic type made of an array of individually addressable pixels is also available.
[23][24][25] In 2015, Korg released the Nutube, an analogue audio amplifier component based on VFD technology.
Light output drops over time due to falling emission and reduction of phosphor efficiency.
Fading can be slowed by using a display driver chip to lower the voltages necessary to drive a VFD.
More recently, outside the education sector, calculator applications on mobile phones have for many replaced the pocket calculator, and there is progression from LED backlit LCDs back to full LED displays in the form of Organic Light Emitting Diode (OLED) displays.
It could easily be driven by transistors, so was aimed at computer applications as it was easier to drive than a neon and had longer life than a light bulb.
The Japanese seven segment VFD meant that no patent royalties needed to be paid on desk calculator displays as would have been the case using Nixie tubes or Panaplex neon digits or for LED displays on pocket calculators.
