Operation
An image dissector focuses a visual image onto a layer of photosensitive material, such as caesium oxide, which emits negatively-charged "photoelectrons" proportional to the intensity of the light striking the material. Electrostatic deflecting plates or magnetic fields then periodically manipulate the resulting electron image horizontally and vertically before an electron multiplier, or a small aperture leading to a positively-charged detector or "anode" in the case of the earliest dissector tubes. The electron multiplier or aperture permits only those electrons emanating from a very small area of the electron image, representing a similarly small area of the visual image. The entire image is scanned several times per second to produce an electrical signal suitably representative of a moving visual image.
Read more about this topic: Image Dissector
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—Francis Bacon (1560–1626)
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