A TV camera tube may be called the eye of a TV system. A TV camera tube is a transducer that converts the variations of light intensity into the variation of electrical current or voltage, known as video signals.
Basic Principle of Camera Tube
An optoelectrical converter is used to translate brightness variations into an electrical picture signal. Different converter systems are available, but only pickup tubes with a photosensitive semiconductor layer are really important for TV technology.
Any picture appears to be composed of small elementary areas of light or shade, which are known as picture elements. The elements thus contain the visual image of the scene. The purpose of a TV pick-up tube is to sense each element independently and develop a signal in electrical form proportional to the brightness of each element. Light from the scene is focused on a photosensitive surface known as the image plate, and the optical image thus formed with a lens system represents light intensity variations of the scene. By making use of photoelectric properties, the image plate then converts different light intensities into corresponding electrical variations.
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