الاشارة التلفزيونية الملونة .. كتاب التلفزيون الملون والعادي

Chapter III :

Color TV signal and color transmitter systems

The color image information carries three color signals, namely: the Red. Green-blue, symbolized by RGB, and the luminance signal Y, which is equivalent to white, and it is the signal that suffices to show the color image in black and white in monochrome receivers or in color television when the color circuit stops or malfunctions.

. It is the Y sign = 59% green + 30 red + 11 blue the basic equation for colors, and the X sign that carries luminance information.

3-1 The color TV signal

It is subtracted from the three colors (RGB) and produces the three signals that carry color information only (Chrominance): R-Y (Y), (BY), and are called color difference signals). (BY). And from them we get the third signal (G-Y) in the receiver, and these two signals carry all the information sufficient to retrieve the three colors - when they are processed with the luminance signal L in the color matrix, and it is called (MATRIX). While the (G-Y) signal carries the least color information
GAMA correction: Before transmitting the color difference signals (R-Y) and (B-Y) and the luminance signal (Y), a so-called gamma correction (8) is performed on them, to obtain the linear proportion between the illumination intensity at the points of the screen and the voltage connected to the LED network. The biggest disadvantage of a screen valve is its nonlinearity and is called gamma distortion. By correcting the TV transmitter, this defect is avoided and the relationship is made linear between the degree of brightness of the image and the received signal, and thus we restore the image as an exact copy in the transmitter and receiver, Figure (1-3). In practice, it appears that the image correction curve must achieve (221). It is the opposite value of ( = (22) for the receiving line to be corrected as in the figure
B-Y,R-Y color difference signal:

The two color difference signals R-Y and BY are denoted in the global systems by different symbols, namely

(Q,I) NTSC p

In the PAL system, the first signal carries information about the color orange or turquoise. The second signal carries green or purple information. These two signals are carried on a subcarrier frequency generated by an oscillator in the transmitter. And on page (990) the difference between the two signals to facilitate the process of retrieving and revealing information in the future - and sending them together without any loss in their information. The frequency of the sub-carrier varies according to the transmission system. It is: 4.43 MHz in the PAL system, and the number of image lines is 625 lines or 525 lines.

In the D-B-D-R Secam system

and capacitive adjustment

4.43 MHz in the SECAM system, the number of image lines 625 lines, the frequency modulation 3.58 MHz in the original NTSC system, the number of image lines 525 lines, and the capacitive modulation
The transmission of 1 is done orthogonally, that is, with a page difference between them (90), and the result of the two signals differs in strength and page according to the difference in the two signals, as in Figure (3 -

(2) and (3 - 3)

The basic equation for colors after gamma correction in transmission becomes the following: EY = 0.3ER + 0.59 É6 + 0.11E

Which represents the white color that was taken as the standard reference color

For color TV, then we find that the luminance signal is equal to .