Screensavers
What does screensaver mean?
Screensaver: A blank screen, picture or animation that is displayed on a
computer screen during moments of user inactivity.
Where did it the term “screensaver”
come from?
Its roots are to be found in the early days of
the cathode ray tube (CRT).
For those of you that scarcely remember the CRT, they were used in the bulky computer
monitors and televisions that had a glass screen.
The CRT is a glass vacuum tube where a narrow
beam of electrons are fired from one end to a phosphorescent surface at the other end. The
phosphorescent surface absorbs the energy of the electron beam and gives off this energy
as light. The brightness of this light is in direct proportion to the intensity of the
electron beam. An image is built up on the screen by sweeping the beam from
the top of the screen to the bottom, in a series of horizontal lines and at the same time
varying intensity of the electron beam.
Colour screens use the same principal but are
more complicated and use coloured phosphurs.
The CRT was often used to display the image
provided by security cameras, ATMs, airport timetables etc. The unchanging image resulted
in all or the brightest part of the image being permanently burnt into the phosphorus
coating of the display.
The same happened with a CRT computer display
where an unchanging image was displayed for long periods..
The new plasma displays suffer with burn-in and to a lesser extend LCD screens, although
for LCD screens the mechanism of the burn in is different. Both types of display suffer
from a slight image persistance known as transient image persistence, it looks like screen
burn but is not permanent.
Computers would be far better having their
monitors reduced to a low power mode or even powered off during periods of inactivity.
This would not only save on energy but not waste the useful working life of the display
components, E.G the LCD backlight gradually reduces in brightness throughout its working
life and is not generally replaceable. Perhaps the term screensaver should be now changed
to screenwaster. |
