A D V E N T U R E S in C Y B E R S O U N DThe Image Orthicon (Television Camera) Tube c. 1940 - 1960An Image Orthicon tube is a vacuum tube used in early television cameras to take the television picture. It changes light from the scene being televised into electronic signals. The Image Orthicon was developed by the RCA Corporation in the early 1940s. Until the mid-1960s, most television cameras used Image Orthicon tubes. Most cameras that have been built since then use vidicon tubes.
 Image Orthicon Television Camera Tube
The front of the Image Orthicon contains a screen called a photocathode that releases electrons when light from the camera lens strikes it. Bright parts of the scene knock out more electrons than dim parts do. Another screen behind the photocathode, called the target, attracts the released electrons, and a positively charged electronic image of the scene forms on the target. The image consists of highly and weakly charged spots that correspond to the bright and dim areas of the scene. A beam of electrons then scans the target, which absorbs electrons from the beam in proportion to those knocked out by the image. The remaining electrons in the beam bounce from the target. At the rear of the Image Orthicon, a device called an electron multiplier strengthens the returning beam several thousand times. This beam becomes the television picture signal. The development of the Image Orthicon in the early 1940s, followed the Iconoscope a device that accomplished a similar purpose, but required an extensive lighting system to operate properly.
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