Cathode Ray Tube

The cathode ray tube is a vacuum tube containing an electron gun, as a source of electrons, and a fluorescent screen, with internal or external means to accelerate and deflect the electron beam, used to create images in the form of light emitted from the fluorescent screen. The image may represent electrical waveforms, television pictures, radar targets and others. The cathode ray tube uses an evacuated glass envelope which is large, deep, heavy, and relatively fragile. Display technologies without these disadvantages, such as flat plasma screens, liquid crystal displays, DLP, OLED displays have replaced cathode ray tube in many applications and are becoming increasingly common as costs decline.

The earliest version of the cathode ray tube was invented by the German physicist Ferdinand Braun in 1897 and is also known as the 'Braun tube'. It was a cold-cathode diode, a modification of the Crookes tube with a phosphor-coated screen. The first version to use a hot cathode was developed by John B. Johnson, who gave his name to the term Johnson noise, and Harry Weiner Weinhart of Western Electric, and became a commercial product in 1922.