orthicon n a now obsolete picture pickup tube in a television camera; electrons emitted from a photoemissive surface in proportion to the intensity of the incident light are focused onto the target causing secondary emission of electrons Usage(s) The size and complication of the image orthicon would keep television from any use as a hidden, unwinking eye. The image orthicon, 100 times as sensitive as earlier tubes, had actually amplified the light reflected from their faces. Primarily intended for brightening the faint images on X-ray fluoroscope screens, it is based on the image-orthicon tube used in television cameras. Synonym(s) image orthicon