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2009-04-09 Display Hardware

posted Apr 9, 2009, 10:50 PM by Unknown user   [ updated Apr 9, 2009, 10:56 PM by Eddie Woo ]
For further details, please refer to IPT: Display Hardware

Cathode ray tube

CRT screens are boxes with a phosphor-coated glass window at the front and an electron gun at the back. They are capable of displaying images and animations.

Phosphors are chemical compounds that illuminate when contact is made with particles that have energy, such as electrons. This makes them easy to control as far as light intensity is concerned: the more energy that is provided, the brighter the output will be. Another property of phosphors that make them ideal for use in display hardware is the fact that they come in different colours*.

The electron gun at the back directs electrons to the phosphor coating. Various focusing coils, masks, and deflectors between the electron gun and the glass window ensure that the electrons hit the phosphor coating in the correct places, and furthermore, that they hit the correct types of phosphor (red, blue, and green), effectively producing an accurate image with any colour combination possible in the real world.

The phosphors used in CRT screens lose their luminance almost immediately after being hit with electrons. Hence, electrons need to be constantly fired, requiring more energy; however, this also means that animations can be displayed, as the image will need to change many times a second**.


* depending on the chemical structure of the phosphor
** the amount of times the image changes every second is called the refresh rate
Image: "Mac Mini with a CRT Display" by Ben Dodson

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