Television Camera

television camera [′tel·ə‚vizh·ən ‚kam·rə]

(electronics)

The pickup unit used to convert a scene into corresponding electric signals; optical lenses focus the scene to be televised on the photosensitive surface of a camera tube, and the tube breaks down the visual image into small picture elements and converts the light intensity of each element in turn into a corresponding electric signal. Also known as camera.

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Television Camera 

a device designed to produce a video signal that corresponds to the light distribution in a scene to be televised.

Depending on their purpose and field of use, television cameras are classified as broadcast or nonbroadcast cameras. Each category includes a large number of different types of cameras. For example, broadcast television cameras include studio and remote-pickup types, stationary cameras for televising announcers, and cameras for televising motion pictures. Nonbroadcast cameras are particularly diversified, as they must meet a wide variety of requirements. For example, cameras used for underwater television must be watertight and able to withstand considerable pressure, and they must have additional light sources for operation at great depths. Cameras used in space research must operate satisfactorily under conditions of extreme temperature gradients, absolute vacuum, and high radiation levels. Cameras for black-and-white and for color transmissions differ chiefly in that the video signals from the latter carry additional information about the color of each part of a scene.

Black-and-white television cameras consist of a lens, a television camera tube, a horizontal scanning generator, a vertical scanning generator, and a video amplifier. Broadcast cameras are operated by cameramen and are equipped with a viewfinder having a kinescope, which permits the image being transmitted by the camera to be observed on a screen.

Color television cameras usually contain three camera tubes, which produce signals corresponding to the three color components of the luminous flux—red, green, and blue. The luminous flux is separated into components by a color-separating optical system, which consists of a polygonal prism coated with dichroic films or a system of dichroic mirrors. The system is located between the lens and the photosensitive element of the camera tube. The rasters in the camera tubes can be kept synchronized because they are connected to common scanning generators. Video signals from the camera tubes are amplified and fed by cable to a camera control unit and encoding device, where the composite television signal is formed. In broadcast television, several camera chains are combined, either at the television center or at a mobile television station. Color television cameras also have devices for the accurate superposition (manual or automatic) of the images formed by the three camera tubes.

Improvements in television cameras have led to size and weight reductions, and modern designs are increasingly self-contained. Single-tube color television cameras with an encoding optical filter have been designed, with dimensions close to those of a motion-picture camera. Self-contained designs can be achieved either by lengthening the camera cable or by converting the camera into a completely independent unit with its own synchronizing generator and encoding device. In the latter case, the composite signal may be transmitted from the camera by radio or recorded on a videotape recorder.

A. Z. LEIBOV