Somehow, imperceptibly, the time came when TVs and monitors based on cathode-ray technology almost completely disappeared from store shelves. Recall, these are the same bulky devices that occupied almost half of the computer desk. It is now their thickness rarely exceeds 10 cm, and then only taking into account the lamp illumination.
It is not surprising that many have safely forgotten what a CRT monitor is. But in vain! If only because in some respects it is ahead of even the most modern liquid-crystal analogues.
How are monitors CRT
First of all, we give a decoding of the abbreviation. So, the term "CRT" means an electron beam or, as we indicated earlier, a cathode tube (from the English CRT - Cathode Ray-Tube). As a rule, with the word “tube”, most people represent a cylinder with no walls at its ends. Speaking about what a CRT monitor is, it is necessary to mention that in this case such a representation is erroneous. Because the shape of the tube in it is far from cylindrical and expands to a plane on one side. This surface is the front glass part, the one on which the images are formed. The inner side of this site is covered with a special substance - a phosphor. Its unique property is that when a stream of charged particles hits it, their kinetic energy is naturally converted into a glow.
Thus, a CRT monitor is a device in which beams of electron beams draw a picture on the inside of the screen. A man sees her, thanks to the glow of the phosphor.
On the other side of the bulb is a block of electrodes called guns. They create the flow of particles.
In other words, a CRT monitor consists of a glass tube, gun electrodes and a control circuit.
Principle of operation
As you know, mixing in a certain ratio three main colors: green, red and blue - you can get all the rest, including shades. In color monitors, the entire internal surface of the screen consists of dots conventionally grouped into triads (blocks of 3 pieces). Each of them is able to glow with one of the primary colors. There are also three electrodes, each of which highlights their “points”. In a certain order, igniting and passing them on the screen, it is possible to form a color picture. By the way, there is only one gun in black and white image devices.
To control the flow of particles, electromagnetic deflection is used, and the initial direction of their movement is created due to the potential difference.
Since it is technically quite difficult to ensure the accuracy of the beam hitting its point, a special solution is used - a mask. Relatively speaking, this is a perforated mesh between the screen and the guns. There are various types of masks. In part, they are responsible for the display features (clarity, the shape of pixel dots).
Since after the impact of a particle, the luminosity of the phosphor decreases very quickly, it is necessary to constantly recreate the picture. Both static and dynamic. Therefore, the rays draw an image dozens of times per second. These are the famous Hertz personnel scan. The higher the frequency, the less noticeable flicker.
Currently, repair of CRT monitors for subsequent use as part of a computer system is impractical, as modern LCD technology is more promising. The exception is specific use.