English: Russian-American electrical engineer Vladimir Zworykin holding his iconoscope television camera tube around 1950. The iconoscope, developed by Zworykin between 1923 and 1933 at RCA laboratories, was the first successful electronically-scanned television camera tube. It consists of an evacuated glass envelope containing a square photosensitive mica target onto which the image is projected by an external lens. In the light areas of the image, the light knocks electrons off the target surface, discharging it. An electron beam from an electron gun to the side scans the target. Areas which are charged scatter the electron beam, and the current is picked up by a collector electrode. The iconoscope was the main television camera tube used between 1936 and 1946, when it was superseded by the image orthicon.