The Image Isocon-A Low-Light Television Tube

The isocon camera tube is a development of the image orthicon, but produces a positively modulated output signal. In the image orthicon, the output signal has negative modulation and the detection of weak signals is limited by the shot noise in the large return beam current. The isocon overcomes this limitation as the return beam current is small for small signals, and the signal-to-noise ratio is maintained to very low light levels. The scanning beam current can be set to discharge highlights without materially affecting the low light performance, thus giving very wide dynamic range.