1. A mechanism used to see through haze and fog when an infrared image is formed optically on the photoemissive mosaic of an electron-image tube and then made visible by the tube.
2. An instrument in which the infrared light of a distant object is focused onto a photocathode tube, enlarged by a series of electron lenses, and reproduced onto a fluorescent screen to form an image of the object.
3. A telescope in which an infrared image of a distant object is focused on the photosensitive cathode of an image converter tube.

The resulting electron image is enlarged by electron lenses and made visible by a fluorescent screen.