Editing Photocathode (section)

==Uses==
For many years the photocathode was the only practical method for converting light to an electron current. As such it tends to function as a form of 'electric film' and shared many characteristics of photography. It was therefore the key element in opto-electronic devices, such as [[Video camera tube|TV camera tubes]] like the orthicon and vidicon, and in image tubes such as [[Night vision device|intensifiers]], converters, and [[Image dissector|dissectors]]. Simple [[phototube]]s were used for motion detectors and counters.

Phototubes have been used for years in movie projectors to read the [[Sound-on-film|sound tracks]] on the edge of movie film.<ref>{{cite book | last1 = Fielding | first1 = Raymond | title = A Technological History of Motion Pictures and Television | pages = [https://archive.org/details/technologicalhis0000fiel/page/360 360] | isbn = 9780520050648 | year = 1983 | publisher = University of California Press | url = https://archive.org/details/technologicalhis0000fiel/page/360 }}</ref>

The more recent development of solid state optical devices such as [[photodiode]]s has reduced the use of photocathodes to cases where they still remain superior to semiconductor devices.