Pixels – the basic element in the screen image

Pixels – the basic element in the screen image

When you look at a screen image, it actually consists of thousands of tiny dots. If you look close you can spot them. Each of these dots is called a pixel. That is a contraction of the term Picture Elements.
In an ordinary screen, each pixel consists of three colors: Red, green and blue. Thus, there are actually three "sub dots" in each pixel. But they are so small that they "melt" together as one dot:

The individual pixel or dot then consists of three mini dots, also called trio dot. Some screens do not have round dots, but they work the same way. With the three basic colors, each of which can be assigned with varying intensity, you can create many different colors.

The cathode ray tube

A traditional picture tube is like a big glass bottle. There are three electron guns in the narrow end. They fire towards the large flat surface facing the user.

The inside of the glass surface we look at is coated with tiny phosphorous dots. They are arranged in groups of three – a red, a green and a blue phosphorous dot. Together they make a pixel. These dots light up, when hit by elections from the electron gun. Each of the mini dots is hit by its own electron gun.
The more powerful the beam is, the brighter they get. The electron beams are guided by electromagnets, which bend the beams, so they hit the exact desired phosphorus dot.

The electron beams sweep across the screen very fast. Each of the three electron guns must scan its intended color mini dots continually, from left to right, line by line from top to bottom, typically about 70 to 85 times per second. The beam intensity can be adjusted for every mini dot, to adjust the color.
A typical screen image could consist of 480.000 pixels. That is called a 800 x 600 image. There are 800 dots in each horizontal line, and there are 600 lines from top to bottom of the screen. That adds up to 480,000pixels.