Analog Television - Digital Video and Audio Broadcasting Technology - page 11

Let us look at how such a black/white signal, the “luminance signal”, is
produced. Using the letter “A” as an example, its image is filmed by a TV
camera which scans it line by line (see Fig. 2.4.). In the early days, this
was done by a tube camera in which a light-sensitive layer, onto which the
image was projected by optics, was scanned line by line by an electron
beam deflected by horizontal and vertical magnetic fields.

1
2
3
4
5
6
7
8
9
10
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12

700mV = white

Line 3

0mV = black

Fig. 2.4. Scanning an original black/white picture

H
blanking

700mV = white

0mV = black

300mV

Hsync

Visible
part

Fig. 2.5. Inserting the horizontal sync pulse

Today, CCD (charge coupled device) chips are universally used in the
cameras and the principle of the deflected electron beam is now only pre-