Iconoscope
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The Iconoscope was an early television camera tube in which a beam of high-velocity electrons scans a photoemissive mosaic. Designed by Vladimir Zworykin in 1929, it was the first practical all-electronic camera tube and replaced earlier electrical and mechanical combinations such as Nipkow's disk. The iconoscope was later replaced, but it laid the foundations for early television cameras.
There is some similarity between the Iconoscope and EMI's Emitron camera developed primarily by J D McGee, and in theory the EMI team under Isaac Shoenberg may have had access to some RCA research under a patent-sharing agreement. However when Zworykin published a paper on the Iconoscope in 1933, Shoenberg concluded that EMI was ahead technologically and had little to learn from Zworykin's development, turning down an offer of technical assistance from RCA.
[edit] Design
Images were projected onto a photosensitive plate, which broke up the image into thousands of picture elements now known as "pixels." A scanning electron beam traversed the face of the plate, "charging" all the pixels. Each pixel retained an electrical charge proportional to the light energy initially projected onto it which was fed to the output of the camera. In this way, a visual image was converted to an electrical signal. There had been other attempts to produce an all-electronic camera tube, but the Zworykin model was easier to manufacture and produced a very clear image. One drawback was that it required very bright, hot lights in the television studio. While it began to be replaced in the 1940's with better technology, many of the basic concepts were retained, such as the use of a photosensitive plate and the scanning electron beam.
