Science Fair Project Encyclopedia
Video camera tube
In older video cameras, prior to the 1990s, a video camera tube or pickup tube was used instead of a charge-coupled device (CCD). Several types were in use from the 1930s to the 1980s. They operate in a somewhat similar manner to cathode ray tubes, which display pictures, but are instead used to capture images that are projected onto them through the camera lens system.
The terms vidicon tube and vidicon camera are often used indiscriminately to refer to video cameras of any type. The principle of operation of the vidicon camera is typical of other types of video camera tubes.
The image orthicon tube or simply orthicon tube was common up into the 1960s. It replaced the Iconoscope which required a great deal of light to work adequately. A properly constructed Image Orthicon could take television pictures by candlelight due to the more ordered light sensitive area and the presence of an electron multiplier at the base of the tube, which operated as an high efficiency amplifier. It also had a logrithmic light sensitivity curve similar to the human eye, so the picture looked more natural. It's defect was that it tended to flare if a shiny object in the studio caught a refelction of a light, generating a dark halo acround the object on the picture. Image Orthicons were used extensively in the early color television cameras where their increased sensitivity was essential to overcome their very inefficient optical system. A engineer's nickname for the tube was the "immy", which later was feminized to become the "Emmy".
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