how does a flt screen moniter work
Essentially, a computer screen has the task of making the internal state of a computer known to a human user. For this purpose, there are two techniques:
1. a map of colored bits is made in memory (pixels) which are displayed on a CRT or flat panel display — each pixel (or pel) of the map is displayed by three colored dots on the display.
2. for moving 3-D images such as games, a display list is kept in memory which keeps a map of triangular facets, each of which is colored, has qualities of texture and reflection and can be hidden behind other triangles. This list is dynamically converted into an image map as the map is displayed on the screen.
In both cases, the display uses a trio of colored dots (can be short parallel segments or dots in a triangle), which can be displayed with predefined brightness. The three colors chosen approximate the dye used by your eye to discern color (the cone cells in the retina). Since in normal humans there are three such dyes, only three colors need to be added to make a reasonable image — with your brain filling in the inaccuracies. (Color blind people are missing one or more of these dyes in their eyes — so they cannot distinguish some combinations of colors — e.g. red/green colorblindness.) By the way — although it is true that cats are colorblind (as we understand color) they have much better night vision. Ducks, by the way have 8 dyes in their eyes — so have much sharper color discernment than humans. Their rainbow would likely have tens of distinct colors — not just the 7 or 8 colors we see.
Physically, a CRT has three electron beams which are scanned across every set of dots on the front of the tube — the beams can be modulated (the intensity of the beam can be changed quickly) so that each dot gets the right amount of brightness for that part of the image.
In a TFT panel display, a florescent panel light is mounted in front of an array of amorphous transistors which control liquid crystals. These crystals align themselves with an applied electric field (from the transistor) which changes the polarization of light through the pixel. When the polarization matches a special coating on the display, light is let through — so the LCD acts like a variable shutter to the light coming from the panel behind it. Again trios of shutters are used to make any color out of just three. The colors are red, green and blue — although yellow is a primary, you don’t have a dye which responds to yellow — instead, it triggers both the green and red dyes in your eye — and you see yellow. The process is additive, unlike mixing paint, so that red and green make yellow, blue and green make cyan and red and blue make magenta. All three make white
