the present invention relates to display manufacturing technology , especially for a dielectric - free triode field emission display device based on double - gate / single - cathode type electron emission units and the device drive methods . this device comprises parallelly positioned anode and cathode / gate plates , during production , gate / cathode / gate electron emission units are set on the cathode / gate plate side by side . the spacing between cathode and gate electrodes is vacuum circumstance . for each cathode , an anode is positioned on the anode plate , facing the cathode . and the voltages applied on the cathode and gate electrodes are to scan and the anode voltage is to adjust the signal . when the electrodes on the cathode / gate plate take on fixed roles , fixed voltages are used to drive the device . when these electrodes on the cathode / gate plate can be used interchangeably as cathode or gate electrodes , respectively , pulse scanning method is used to drive the device .