How is the Television Picture made?
Most persons have a television in
their homes but they are quite unaware of the science that goes on. Some of the
pioneers who helped to invent the television were John Logie Baird, Philo
Farnsworth and Vladimir Zworykin. Without the television, communication
throughout the world would be limited and we would not have the movie industry,
which involves our daily entertainment
The television picture begins in
the camera. There is no film in this camera. Its job is to change the picture
it sees into a sort of electrical picture that can be sent through wires and
across space.
1. Light enters lens – the picture comes in
through the camera and is focused on a screen that is sensitive to light
2. And falls on screen – as the ray of
light hits the screen, it gives off the microscopic charges electricity called
electrons
3.
Releasing
electrons
4.
Which
flow to target
5. Electron gun “scans” target – at the
other end of the tube is an electron gun, shooting out a thin stream of electrons
the way a water pistol shoots out water. This stream of electrons moves back and
forth across the face of the target, which has light sensitive spots.
6. And its beam bounces back to the electron collection plate -
7.
Is strengthened
8. And flows out of the tube – The
electron beam scans so quickly that 30 separate pictures are being sent out every
second. This fast enough to catch and send out whatever action is going on in
front of the camera.
Television image
scanning consists of horizontal lines that are sequentially displaced in a
vertical direction until the whole image area is covered. When no picture
information is present, the full set of scanning lines is called a raster. The
scanning of a single image is called a field, and the horizontal vertical scan
rates are normally synchronous with the local power line frequency.
References
Bookshelf for
boys and girls (1958) Nature and Science
University Society: USA
