Many researchers were responsable for the development of the cathode ray tube. In this way, the first application of cathode rays to engineering measurements was made by Karl Ferdinand Braun in 1897 by mean of his experimental device as known as the Braun tube. (a)
It consisted of a glass tube comprising in one of its end the cathode. The anode is inserted in the side of the tube so as not to be in the path of the ray beam, whose cylindrical shape is controlled by the diaphragm, a plate with a circular central hole. In the other end of the Braun tube there is a mica plate or the screen. Its side facing to the ray beam is coated with a fluorescent mineral substance. When the tube is excited the screen shows a bright luminescent spot upon its bombardment by the cathode rays. This spot may be deflected in any direction, vertical or horizontal, by means of an electrostatic or magnetic field in such away two electrical phenomena in their mutual relatioship can be displayed on the fluorescent screen, for instance, the linear increasement of a current with the time, giving the birth of the cathode rays oscillograph. (b)
In spite of such electrical measurements, the Braun tube could be used also for others applications. In this way, if the electron bean zigzag or electrical scanning on the screen is made to vary in accordance with the brightness of each point of a picture, the same could be used for reproducing black and white images in the form of a line pattern. Over the years, since its invention in 1894, the Braun tube was upgraded by constantly technological improvement up to the modern cathode rays tube as kown as kinescopes. (c)
At the beginning of 1950, the kinescopes were still manufactured in a round shape with 23 cm in size and thus producing small image area. In order to compensate such technical handicap, the first television receivers were built using a kind of optical system in such away the kinescope image was projected on a translucent screen. (d)
Nowadays, the kinescope screen is manufactured by using complex mixtures of fine powders called as phosphors. In order to improve light efficiency of the screen a thin layer of Aluminium is applied across the inside of the powder substrate. In this way, this kind of surface finishing as known as, metal backing works as a reflector and returns all ligh bean directed inward. (e)
Due to the continuous technological development, new types of screen concepts, such as the ones using the Plasma and the LCD tehcnology, soon will replace the traditional kinescope. The LCD screen consits of thousands of liquid crystal sensors, whose ultra-fast luminous response will be controlled by light filters. A very thin solid-state device, in a transparent film shape with 0,3 micron in thickness, similar to a transitor, will supply the proper voltages in time intervals of thounsands of seconds, producing high definition colored images. (f)

(a) Esquemático do tubo de Braun, projetado em 1897.
The Saga of Vacuum Tube

(b) The discovery of the cathode rays. It was a consequence of the studies for the development of the atomic theory. Around 1830, during his electrochemical experiments, Faradys observed the effect of application of high potential between two electrodes within crudely evacuated glass envelope.
Later Faraday's observation was confirmed by Crook's experiment. Basically, it consisted to connect the poles of high potential source to two metals plates inside an air evacuated glass tube.
During the experiments Crooks noted that the glass tube walls emitted a faint greenish light. The Crookes's tube showed that the fluorescence or rays were more properly discrete particles leaving the cathode at righ angles to its surface. Such phenonomen was named as cathode rays.
(b2) the Crooks' tube
(c) A modern cathode rays tube.

(d) Diagram of a projection television system.

e) The cathode rays tube type MW6-2 made by Philips for the first televison receivers using a projection optical system.

(f) The micro-screen operation principle provided with LCD sensors.

(g) Magazine Communication, Feb. 1939..