تشكيل الصورة على الشاشة ٢_a .. كتاب التلفزيون الملون والعادي

The amplitude of the composite visual signal - as for the width of each vertical pulse, is equal to (2.41) of a horizontal line, i.e.: 15424) (microseconds) - and its frequency is (50 Hz). scan time

In view of the wide width of the vertical pulse, and in order not to disturb the horizontal synchronization during its passage, it was divided into five narrow pulses, with small intervals between them, and the width of each pulse is equivalent to 41% of a period, and the width of each scanning interval is equivalent to 9% of the period of each line scan - this allows The segmentation is also done using successive pulses of horizontal synchronization in both odd and even line fields

Image sliding when vertical synchronization is lost

Equalizing Pulses:

These pulses are located before and after the vertical synchronization pulses, and the number of each of them is five pulses, each with a width of 4.5% of the time of the horizontal line, Figure (1-14). These pulses work to adjust the validity of the interlocking process between each two fields of the image. The first field starts from the left and top of the screen and ends in the middle and bottom of the screen (1 - 3 - 5-...625), while the second field (2) - 4 - 6-62400 starts from the middle of the top of the screen and ends at the bottom and right of the screen. Because each field = (312.5 lines) and it is noted that the vertical synchronization pulse received at the end of the single field scan starts after the last horizontal synchronization pulse with a period of time equal to half a line. While the next vertical sync pulse at
The end of the even field scan, it starts immediately after the last horizontal synchronization pulse (Fig. (1-10).

We will find that the separation of the vertical synchronization pulses is done by an integration circuit, so the difference between the two vertical synchronization pulses of the odd field and the even field will make the capacitor charge of the integration circuit different in the two cases. So the forward threshold of the pulse resulting from the integration of the even field synchronization pulse is less sharp and inclined than that resulting from the integration of the odd field synchronization pulse, and this leads to the stopping of the effective scanning of the even lines at a relatively early moment, so that the period during which the effective scanning of the even field takes place is less than the effective scanning period for the individual field. The frequency of the equalizer pulses is twice the frequency of the horizontal scan, i.e. = (31250) Hz.
- Blanking Pulses: It is the one that extinguishes or erases the beam while it bounces from right to left or from bottom to top of the screen. His trace does not appear on the image, thus blurring its features that he drew during the scanning process. The extinguishing signals have a pulse shape and are divided into: A - Horizontal extinguishing pulses: they operate during the recoil of the horizontal beam (Fig. Horizontal i.e. (15625) pulses / second), and its amplitude is equivalent to 75% of the maximum amplitude of the composite visual signal, and it is sufficient to connect the screen valve to the cut-off state (darkening). It is equivalent to (20) scan lines) and its time is (1280 microseconds), and its frequency is the frequency of the vertical synchronization pulses, i.e. (50) Hz. This pulse has been made relatively slow to get rid of the negative effects and disturbances that may arise in the vertical and horizontal deviation circuits as a result of the recoil. Rapid vertical of the scanner beam
note :

The extinguishing pulses result in some loss of image detail up to

Approximately 24.4 - Since the image details can be calculated as follows: Theoretically, the image details are 625 x 625 x = 520,833 points

The loss is 244,520,833 = 127,083 points, the details of the image in practice = 520,833 - 127,083 = 393,750 points, or about 400,000 points or detail