Perhaps there is no such person who in his life has not come across devices that include a cathode ray tube (or CRT). Now such solutions are being actively superseded by their more modern counterparts based on liquid crystal screens (LCD). However, there are a number of areas in which the cathode ray tube is still indispensable. For example, LCDs cannot be used in high-precision oscilloscopes. However, one thing is clear - the progress of information display devices will ultimately lead to a complete rejection of CRTs. It is the matter of time.
A cathode ray tube: a story
Yu. Plucker can be considered the discoverer, who, in 1859, studying the behavior of metals under various external influences, discovered the phenomenon of radiation (emission) of elementary particles - electrons. The formed particle beams are called cathode rays. He also drew attention to the appearance of a visible glow of certain substances (phosphor) when electron beams hit them. A modern cathode ray tube is capable of creating an image precisely thanks to these two discoveries.
After 20 years, it was experimentally established that the direction of motion of the emitted electrons can be controlled by the action of an external magnetic field. This can be easily explained if we recall that moving negative charge carriers are characterized by magnetic and electric fields.
In 1895, K. F. Brown finalized the control system in the tube and thereby managed to change the directional vector of the particle flow not only by the field, but also by a special mirror capable of rotation, which opened up completely new prospects for using the invention. In 1903, Venelt placed a cathode-electrode in the form of a cylinder inside the tube, which made it possible to control the intensity of the emitted flux.
In 1905, Einstein formulated the equations for calculating the photoelectric effect and after 6 years a working device for transmitting images over distances was demonstrated. The beam was controlled by a magnetic field, and a capacitor was responsible for the brightness value.
At the beginning of the production of the first CRT models, the industry was not ready to create screens with a large diagonal size, so magnifying lenses were used as a compromise.
Cathode ray tube device
Since then, the device has been modified, but the changes are evolutionary in nature, since nothing fundamentally new has been added to the work.
The glass case begins with a cone-shaped tube forming a screen. In color image devices, the inner surface with a certain step is covered with three types of phosphor (Red, Green, Blue), giving their color of glow when an electron beam hits. Accordingly, there are three cathodes (guns). In order to weed out the defocused electrons and to ensure the exact hit of the desired beam at the desired point on the screen, a steel grating is placed between the cathode system and the phosphor layer. It can be compared with a stencil that cuts off everything unnecessary.
Electron emission begins from the surface of the heated cathodes. They rush towards the anode (electrode, with a positive charge) connected to the conical part of the tube. Then the beams are focused by a special coil and fall into the field of the deflecting system. Passing through the lattice, they fall to the necessary points on the screen, causing the conversion of their kinetic energy into a glow.
Computer Engineering
Monitors with a cathode ray tube are widely used in computer systems. Simplicity of design, high reliability, accurate color reproduction and the absence of delays (the very milliseconds of the matrix reaction in the LCD) - these are their main advantages. However, recently, as already indicated, CRT is being replaced by more economical and ergonomic LCD monitors.