A first generation image intensifier does not use a micro-channel plate. The electrons are guided from the input to the output by means of electrostatic focussing. Two types can be distinguished: proximity focussed diodes and electrostatic inverters. In the latter a structure of electrodes form an electrostatic lens that focusses the electrons coming from cathode onto the anode. The advantage of electrostatic focussing is that it allows de-magnification of the image. This is especially interesting when these devices are coupled to small CCDs.

Advantages of first generation tubes

  • Available in de-magnifying formats

  • Therefore no fiber optic taper required

  • No MCP noise

  • High intra-scene dynamic range

  • Low cost (standard models)

Disadvantages

  • Electrostatic inverters show a few percent of image distortion

  • Relatively low gain

  • Gating not possible

  • No UV sensitivity

  • Limited external gain control

  • Poor over-illumination protection