A sealed glass tube in early (1930s and 40s) video cameras in which light is converted into electric waves.It was invented in 1929 by the American Viadimir Zworykin. The tube has a vacuum-tight glass envelope. At its center is a dielectric plate, one surface of which is coated with a thin uniform layer of metal, the other with a mosaic of thousands of tiny metal elements which release electrons when illuminated. The image is focused onto this mosaic, which makes up a series of mini-condensors. An electron beam bombards these, one after the other. The amount of charge collected is proportional to the charge on each condensor, and therefore to the strength of illumination of each element.(pr. i:-KAH-nə-skohp)