What is CRT in Computer Technology

Tube screen

The old screens are cathode ray tube monitors (CRT), the display surface of which is a tube. This picture tube is an oversized tube that works in a similar way to its little brother in the audio amplifier area. The same type of tube is built into the television. The picture tubes for computer monitors are of higher quality because the distance between people and the monitor is less than with a television. Therefore, the display quality on the computer monitor must be significantly better.
The main disadvantage of the cathode ray monitors is the enormous space requirement due to the deep design, the very high power consumption and the heat generation.

Structure and functionality of the tube screen

The tube consists of an evacuated, black glass flask. The external pressure is on the tube. It must therefore be protected from mechanical damage, otherwise there is a risk of imploding, which in the end results in an explosion. When the monitor is switched on, an electron beam is generated by the cathode (metallic electrode) at the rear end of the tube, which is directed towards the display surface and hits the pane there. A glowing spot is created there. Each cathode ray tube has three cathodes. One each for the colors red, green and blue (basic colors). At the point where these three colors meet the writing, they merge into a mixed color. So that there is no color chaos on the screen, there is a mask directly behind the pane so that each electron beam only makes its color point shine.

The electron beam passes other electrodes and coils between the cathode and the disk. These components control the intensity of the electron beam and where it hits the pane. To get a usable screen display, the electron beam is magnetically deflected from left to right and top to bottom. This happens so quickly that the viewer gets to see a still picture. The electron beam changes the line several times per second (line frequency). How often is determined by the resolution and the refresh rate.
The refresh rate and the line rate are generated by the graphics card. In order for the monitor to be able to display an image, it must support the frequencies supplied. Caution is advised here. If the graphics card is configured incorrectly and the monitor can no longer display an image, it may be necessary to reset the settings to a usable level with a higher quality monitor.

Refresh rate60 Hz70 Hz72 Hz75 Hz100 Hz
Resolution 640 x 480 pixels31.5 kHz36.8 kHz37.8 kHz39.4 kHz52.5 kHz
Resolution 800 x 600 pixels37.5 kHz43.6 kHz44.9 kHz46.7 kHz62.3 kHz
Resolution 1024 x 768 pixels48.4 kHz56.5 kHz58.1 kHz60.5 kHz80.0 kHz

Shadow mask

The technology behind the shadow mask is the oldest and the most sophisticated. It is therefore used most frequently. The shadow mask is a thin sheet of metal with holes that is attached behind the front screen of the monitor. The mask bundles the three electron beams (red, green and blue) so that they hit their exact color in the phosphor inside the pane. The better this succeeds, the higher quality and clearer the image display.
The quality of a monitor with a shadow mask can be read from the distance between the holes. The hole spacing states how far apart the holes in the shadow mask are from hole center to hole center. The hole spacing is between 0.32 mm and 0.21 mm. The smaller the hole spacing, the higher the resolution and the better the image display.

Strip mask

Monitors with a striped mask are known as Trinitron (Sony) and Diamondtron (Mitsubishi). Instead of the perforated mask, wires running from top to bottom are attached behind the windshield. Two horizontal wires in the upper and lower halves of the picture fix the stripe mask. These two wires can be clearly seen on light screen backgrounds. Screens with a striped mask have better color sharpness and contrast.
Instead of the hole spacing, the spacing between the adjacent sets of phosphor strips is specified here. However, this information cannot be compared with the hole spacing.

Overview: screens

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Computer technology primer

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Everything you need to know about computer technology.

Computer technology primer

The computer technology primer is a book about the basics of computer technology, processor technology, semiconductor memories, interfaces, data storage devices, drives and important hardware components.

I want that!