Phototube
From Wikipedia, the free encyclopedia
A phototube is a type of gas-filled or vacuum tube that is sensitive to light. These devices operate according to the photoelectric effect: incoming photons strike a photocathode, generating electrons, which are attracted toward the anode. Thus current flow is dependent on the frequency and intensity of incoming light. Unlike photomultiplier tubes, no amplification takes place, so the 'on' current is typically on the order of microamps.
One major application of the phototube was the reading of optical sound tracks for projected films. They were used in a variety of light-sensing applications until they were superseded by photoresistors and photodiodes.
