Electrostatic pickup tube of the return-beam type

Electrostatic electron optics has been developed for use in pickup tubes such as the image orthicon (I O.) and the return-beam vidicon (RBV). Advantages of electrostatic optics in these categories include low power and weight, and the absence of heavy and cumbersome yoke and focus-coil assemblies with high-current circuitry. A disadvantage of the all-electrostatic systems is their current-density limitation. In a return-beam system, however, this drawback may be overcome by the use of a built-in electron multiplier. In this case, the beam current requirement becomes so small that good resolution can be realized despite low values of current density.