how does television produce colored images?

Answer 1

This will take a while, so get something cold to drink. A picture tube has an arrangement of phosphor dots which produce red, green, and blue light. Almost all colors can be made by appropriately controlling the light emitted by the phosphors. Behind the phosphor screen is a shadow mask: a screen perforated with thousands of tiny holes. At the back end of the picture tube are three electron guns, so arranged that one emits electrons that go through the holes to excite the red phosphor, one for green, and one for blue. The electron beams are swept back and forth across the screen at a frequency of 15734.5 Hz by an electromagnet, and swept up and down (at 59.94 Hz) by another one. So, that's how the picture tube works. There is lots more.

A television signal consists of a carrier frequency, which is modulated with a picture signal which changes the amplitude of the carrier according to how much light is falling on the corresponding pixel in the camera tube. A synchronization pulse is added at the end of each horizontal scan line so that the pixels on your CRT can be kept in sync with the pixels in the camera tube. At the end of 480 horizontal scans, during which the vertical position of the scan is moving from the top to the bottom of the screen, 45 lines worth of vertical sync pulses (and also some other information) are placed. The receiver uses diode-capacitor networks or other gadgetry to sort out the sync pulses to control the electromagnets, and feed the picture information to the electron guns. This is the basics of a black-and-white television signal.

The color information is packed into the signal by amplitude and phase modulating a carrier signal that is 3.579545 MHz above the picture carrier. This signal is high enough in frequency that it does not appear visibly in the black-and-white image. The phase corresponds to the hue, and the amplitude corresponds to the intensity of the color. It is necessary to have a local oscillator in the receiver, running at exactly 3.579545 MHz in order to demodulate the color signal, and it is necessary to have this signal match the transmitter subcarrier not only in frequency but in phase. Hence, a reference signal has to be hidden in the broadcast signal, which the local oscillator is compared with to insure phase and frequency lock. This reference signal lurks near the tail end of each horizontal sync pulse, and consists of eight cycles of the 3.579545 MHz signal. Some electronics picks this signal out of the sync pulse and sends it to the phase comparator.

And, now you know how color television works. Simple, eh? But don't get me started on HDTV -- that's more complex yet.

Answer 2

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Answer 3

There are three electron guns in the Cathode Ray Tube (CRT). One electron gun represents the red part of the image, one represents the green and the third represents the blue of the image.

The phosphor screen that faces you has thousands of glowing pixels. Approx 700 wide by 450 tall. Each pixel consists of three glowing side-by-side vertical slits sandwiched together. One emits red glow, one emits green, and the third slit of a pixel emits blue. When all three are lit, the pixel appears to be white. When all three are unlit, the pixel appears black. The combination of the three colors can produce a pixel of any color or brightness. Each slit glows in the front as either red, green or blue and is polished at the back so that the back face of each slit is angled to receive electrons only from the corresponding color electron gun. If you look at your TV screen with a magnifying glass (or put a drop of water on it to act as a magnifying glass) you will see the three slits of each pixel.

The three electron guns scan the phosphor screen downwards one line at a time (but only every other line) once every 1/60th of a second. The next scan does the other ever-other lines).

Each complete downward scan is called a field in which only every other line is refreshed. A pair of fields is called a frame in which every line has been refreshed by the two fields.

Answer 4

By "lighting" the 3 Phosphors in a given "pixel" area with the proper ratio of intensity to be "seen" as the proper color at that location. For example: consider a white square. All the pixels making up the square would be illuminated with a ratio of about 53% red, 36% green and 11% blue. So by only illuminating any one of them, then that color (red,green, or blue) would be the color of the square. If none are on, the square would be black.
Now consider the square as a circle, with two small circles in it, so that it looks like a "smiley" face. By using different ratios of the three colors, we could give it a pail blue back ground, have the face yellow and the eyes green. This is just expanded as the detail of the picture is expanded with the program content..

Answer 5

Conventional CRT TV through the projection mixture of RED, YELLOW and BLUE light beam at a layer of sulphur to form the color

LCD is through the small triangular array which each node having Red, Yellow and Blue. Number of triangular array along the horizontal or vertical line forms the screen resolution

PLASMA is using Gas.. but quite unknown how it works..

Answer 6

I'm not sure about the modern plasma and LCD, but the old style tv's had an electon "gun" that would fire electrons at the red, blue, and green spots on the screen, line by line, color, by color.

Red, green and blue are the primary colors of light.

Answer 7

combination of three colour, red, blue and green fired in to the tube by the in-line gun which is located just behind the tube. When they got mixed up in one slot, they are converted into the colour we perceived.

Answer 8

gone r those dayz to ask such question

just go to market- buy a plasma TV or LCD

& watch ur favourite program


stop thinking - how it works

Answer 9

What's up, just wanted to say, I enjoyed this discussion. quite inspiring replies

Answer 10

Plenty of great answers already for this