صمام الصورة في جهاز التلفزيون .. كتاب التلفزيون الملون والعادي

Chapter Eleven:

Color picture valve TV Picture tube

11-1 Picture valve in the TV set:

It is called the picture valve, the screen valve, or the picture tube, whether in black and white or color television, and it is also called the cathode ray valve. (C.R.T) Figure (1-11). The screen valve in a monochrome television contains one electronic ejector that releases a beam of electrons and directs them in a concentrated manner to a very small point on the screen of the device, which is coated from the inside with a fluorescent or phosphorescent material that lights up when the beam hits the point of collision, with illumination proportional to the intensity and speed of the beam directed at it.

On the neck of the screen are the deflection coils - which deflect the beam horizontally and vertically to draw the linear structure of the Raster image - and can control the illumination of the image by changing the network voltage relative to the cathode voltage of the screen valve. As for the color screen valve, it contains three separate electronic launchers (cannons). The inner surface of the screen is covered with a large number of color-generating phosphorescent dots. They are arranged in the form of triangles or in the form of very close lines that the viewer's eye cannot distinguish.

If the rays from the three launchers are directed at one triple and at the same time, the viewer sees it as white - and any color can be shown by controlling the intensity of each beam by changing the network voltage or the valve cathode voltage: and to ensure that the beam falls on the specified phosphorescent points or lines Only the screen contains a shadow mask that contains a very large number of holes or cracks so that every electronic beam passes through the hole to hit the specific phosphorescent points.

Color screen valve parts:

1- Luminous phosphorescent screen.
2- Shadow mask.
3- Three electronic launchers and electrodes.