plumbicon

The plumbicon is a type of image-sensing vacuum tube used in broadcast television cameras. Developed by Philips in the 1960s, it is a variant of the Vidicon family that uses a lead oxide (PbO) photoconductive layer as the target. Light from the scene alters the conductivity of the photoconductor; an electron beam scans the tube’s face and reads out the accumulated charge as a video signal. The PbO target offered higher sensitivity, improved low-light performance, and reduced image lag compared with earlier camera tubes, along with good linearity and dynamic range, making it attractive for professional broadcasting.

In practice, plumbicons were used in both monochrome and color cameras, including three-tube color systems where separate tubes captured red, green, and blue light. The tubes required a stable vacuum and careful handling, were relatively large and heavy by modern standards, and their performance could be affected by aging of the photoconductive layer and other tube-degradation effects.

With the advent of solid-state imaging sensors, notably CCDs and later CMOS devices, the use of plumbicon tubes declined through the 1980s and 1990s. They were gradually replaced in most new equipment, though some broadcast installations continued to employ image-tube technology for archival or specialty purposes for a time.

See also: Vidicon, Orthicon, Image orthicon, Charge-coupled device.