Engineering topics
Publications and source records attributed to Fredd, E. H..
Constant output maintained, though luminance varies by 5 million to 1. Three means of normalizing video output utilized in video-level controller: iris adjustment, tube voltage adjustment, and automatic gain control. With aid of automatic light control and gain control, television camera accommodates maximum light level 5 million times greater than lowest light level, while outputting constant 3-V peak signal to processing circuitry.
A video level control system is provided which generates a normalized video signal for a camera processing circuit. The video level control system includes a lens iris which provides a controlled light signal to a camera tube. The camera tube converts the light signal provided by the lens iris into electrical signals. A feedback circuit in response to the electrical signals generated by the camera tube, provides feedback signals to the lens iris and the camera tube. This assures that a normalized video signal is provided in a first illumination range. An automatic gain control loop, which is also responsive to the electrical signals generated by the camera tube 4, operates in tandem with the feedback circuit. This assures that the normalized video signal is maintained in a second illumination range.