What is a cathode-ray tube

Perhaps, there is no such person who would not have encountered in his life devices that have a cathode-ray tube (or CRT) in their design. Now, such solutions are being actively replaced by their more modern analogs based on liquid-crystal screens (LCD). However, there are a number of areas in which a cathode-ray tube is still indispensable. For example, LCDs can not be used in high-precision oscilloscopes. However, one thing is obvious - the progress of information display devices will ultimately lead to a total failure of the CRT. It is the matter of time.

Cathode ray tube: the history of appearance

The discoverer can be considered Yu Plukkera, who in 1859, studying the behavior of metals under various external influences, discovered the phenomenon of emission (emission) of elementary particles - electrons. The particle beams formed are called cathode rays. He also drew attention to the appearance of visible luminescence of certain substances (phosphor) when they hit the electron beams. A modern cathode-ray tube can create an image precisely because of these two discoveries.

After 20 years, it was established experimentally that the direction of motion of the emitted electrons can be controlled by the action of an external magnetic field. This is easy to explain if we recall that moving carriers of negative charge are characterized by magnetic and electric fields.

In 1895, KF Brown improved the control system in the tube and thereby managed to change the direction vector of the particle flux not only by the field, but also by a special mirror capable of rotating, which opened up entirely 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 radiated flux.

In 1905, Einstein formulated the equations for calculating the photoelectric effect and after 6 years, a working device for image transmission over distances was demonstrated. The beam was controlled by a magnetic field, and the capacitor was responsible for the brightness.

During 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.

Electron-beam tube device

Since then, the device has been modified, but the changes are evolutionary, since nothing fundamentally new in the course of the work was added.

The glass body begins with a tube with a conical extension forming a screen. In color image devices, the inner surface with a certain step is covered with three kinds 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 defocused electrons and ensure that the right beam hits the desired point of the screen, a steel lattice is placed between the cathode system and the phosphor layer: a mask. It can be compared with a stencil that cuts all that is superfluous.

The emission of electrons begins from the surface of heated cathodes. They rush towards the anode (electrode, with a positive charge) connected to the conical part of the tube. Further, the beams are focused by a special coil and fall into the field of the deflecting system. Passing through the grid, they fall on the right points of the screen, causing the transformation of their kinetic energy into a glow.

Computer Engineering

Monitors with cathode-ray tube have found wide application in the composition of computer systems. The simplicity of the design, high reliability, accurate color rendering and the absence of delays (the very milliseconds of matrix response in LCD) are their main advantages. However, recently, as already mentioned, CRT is replaced by more economical and ergonomic LCD monitors.