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A CRTs electron beam focusing circuitry has to change the focal length of an electrostatic or electromagnetic “lens” according to where on the screen the beam is being directed, as shown in Dynamic Focus . This ensures that the beam is consistently focused on a spot of the correct size on the inside of the … Read more
Originally, the term “dongle” was applied to any external attachment to a PC or one of its components. It seems to have originated in the UK and may have been coined to describe something which “dangled”, or hung, from the back of a machine. These days, the term is normally applied only to devices, which … Read more
To make a beam of electrons do something useful, it has to be deflected from its course in some manner so as to make a trace or scan across the CRT’s faceplate. There are two methods used to do this: with an electrostatic charge and an electro-magnetic field. Electrostatic deflection uses pairs of charged plates … Read more
The deflection yoke’s electromagnets are used to alter the path of the electron beam in a CRT. The job of synchronising the influence exerted by each of the yoke’s two magnets, and so controlling the directing of the beam towards specific parts of the screen, is handled by some electronics known as the deflection circuit. … Read more
Although the Braun tube contained all the essential elements of the modern CRT, these existed in a fairly primitive form and it lacked many of the refinements which are now considered as basic components. In the years following Braun’s work, one of his assistants, Jonathan Zenneck, added a second aperture to the neck of Braun’s … Read more
The development of the first CRT was the culmination of many years, or in this case, centuries, of research and discovery which put into place all the necessary elements. These include: the first manmade phosphor (1603); the first gas discharge tube (1751); the first production of light by exciting a phosphor with an electrical discharge … Read more
A simple form of texture filtering, point sampling, could be used to scale textures prior to their being mapped onto surfaces in a 3D scene. This technique could easily introduce errors by taking a too simple approach to the task. Using a more sophisticated, though slower, technique called “bi-linear filtering”, the colour of each pixel … Read more
There are parts of the CRT that control the production, flow, acceleration and direction of the tube’s electron beam but leave its shape unaltered. As the electrons accelerate towards the screen, they tend to diverge, as they all have a similar negative charge. If this divergence were to continue, the beam’s diameter when it reached … Read more
Before the three-gun, shadow mask CRT was firmly established as a standard for producing colour CRTs, several other novel systems were developed. One of these was the PDF (Post Deflection Focusing) Chromatron developed at the University of California. This tube had a single electron gun addressing a pattern of continuous vertical phosphor stripes on its … Read more
Antialiasing, as the name suggests, is a technique used to combat an effect known as aliasing. When a line is drawn on a piece of paper, its edges appear smooth regardless of the line’s orientation. When a line is drawn on a computer display, whether CRT- or LCD-based, the limited resolution of the display means … Read more
The control grid regulates the number of electrons which are allowed to leave the gun of a CRT by using a negative voltage to repel the electrons. Once free of the control grid’s influence, the electrons then need to be accelerated down the tube to ensure that they strike the phosphor face-plate lining with sufficient … Read more
Anisotropic means “non-uniform shape” and it is because this filtering technique works on non-uniform, or uneven, shaped areas that it is more powerful, and takes much more processing power, than Point Sampling, bi-linear or tri-linear filtering. One of the problems with these methods is that they rely on a square as their sampling area and … Read more
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